The origin of an invasive air sac system in sauropodomorph dinosaurs

One of the most remarkable features in sauropod dinosaurs relates to their pneumatized skeletons permeated by a bird-like air sac system. Many studies described the late evolution and diversification of this trait in mid to late Mesozoic forms but few focused on the origin of the invasive respiratory diverticula in sauropodomorphs. Fortunately, it is possible to solve this thanks to the boom of new species described in the last decade as well as the broad accessibility of new technologies. Here we analyze the unaysaurid sauropodomorph Macrocollum itaquii from the Late Triassic (early Norian) of southern Brazil using micro-computed tomography. We describe the chronologically oldest and phylogenetically earliest unambiguous evidence of an invasive air sac system in a dinosaur. Surprisingly, this species presented a unique pattern of pneumatization in non-sauropod sauropodomorphs, with pneumatic foramina in posterior cervical and anterior dorsal vertebrae. This suggests that patterns of pneumatization were not cladistically consistent prior to the arrival of Jurassic eusauropods. Additionally, we describe the protocamerae tissue, a new type of pneumatic tissue with properties of both camellae and camerae. This reverts the previous hypothesis which stated that the skeletal pneumatization first evolved into camarae, and derived into delicate trabecular arrangements. This tissue is evidence of thin camellate-like tissue developing into larger chambers. Finally, Macrocollum is an example of the gradual evolution of skeletal tissues responding to the fastly specializing Respiratory System of saurischian dinosaurs.

Usefulness of combining computed tomography and air sac fluid examination to rule out aspergillosis: case study in two gentoo penguins (Pygoscelis papua) with respiratory clinical signs

Pulmonary aspergillosis occurring in captive penguins living in zoos and aquariums is a fatal disease owing to its high mortality rate. On conducting computed tomography, two gentoo penguins (Pygoscelis papua) with respiratory clinical signs that were housed at an aquarium in Hokkaido, Japan were found to have a certain amount of fluid in their air sacs. This fluid was collected and cultured for bacteria and fungi, the results of which both came back negative. These results enabled us to rule out bacterial infection or aspergillosis and supported our decision not to administer antibacterial and antifungal drugs. Overall, the combination of computed tomography and air sac fluid examination was useful for ruling out bacterial infection or aspergillosis in penguins with respiratory clinical signs.

In situ observation of a macrourid fish at 7259 m in the Japan Trench: swimbladder buoyancy at extreme depth

A macrourid, Coryphaenoides yaquinae sp. inc., was observed to be attracted to bait and exhibiting normal foraging behaviour during a period of 80 min within view of a baited video camera on the sea floor at 7259 m - the deepest ever observation of a fish species with a swim bladder. The buoyancy provided by an oxygen-filled swim bladder at 74.4 MPa pressure was estimated to be 0.164 N, at a theoretical energy cost of 20 kJ, 200 times less than the cost of equivalent lipid buoyancy. During normal metabolism, 192 days would be required to fill the swimbladder. At these depths, oxygen is very incompressible, so changes in volume during ascent or descent are small. However, swimbladder function is crucially dependent on a very low rate of diffusion of oxygen across the swimbladder wall. The oxygen in the swimbladder could theoretically sustain aerobic metabolism for over 1 year but is unlikely to be used as a reserve.

Evidence of Atlantic midshipman (Porichthys plectrodon) vocalizations from an unmanned surface vehicle in the U.S. South Atlantica)

An unmanned surface vehicle (USV; Wave Glider) was deployed to study the coastal soundscape in shallow (less than 30 m) coastal waters off the coast of Cape Canaveral, FL, in July 2020 and January 2022. These surveys documented temporal and seasonal trends in biological sounds across a variety of habitats within an 812-km2 survey area, including sand shoals, sand-mud plains, and natural hardbottom. Among a broader diversity of identifiable and unidentifiable fish choruses recorded during the survey, a distinct and previously unidentified fish chorus was recorded; corroborating evidence suggests it and other sounds with similar spectral properties may be produced by Atlantic midshipman. Putative Atlantic midshipman sounds included an agnostic grunt and a seasonal chorus of persistent hums that peaked 3 h after sunset in the summer survey. While Atlantic midshipman have been demonstrated to have well-developed sonic muscles on their swim bladder, their acoustic behavior has not been previously described. Our use of a mobile passive acoustic platform combined with bottom sampling of fish communities highlights an important opportunity to identify previously undocumented biological sound sources in coastal habitats.

Fish hearing revealed: Do we understand hearing in critical fishes and marine tetrapods

Hearing evolved in lampreys with a frequency range of 50-200 Hz. This hearing range is comparable to that of elasmobranchs, most non-teleosts, and lungfish. Elasmobranchs most likely use the saccule and the papilla neglecta (PN) for hearing. In non-teleosts and teleosts, lungfish, and certain tetrapods the saccule is the likely sensor for sound reception while the lagena and the PN are important for gravistatic sensing. Coelacanth and most tetrapods have a basilar papilla (BP) for hearing. In coelacanth and tetrapods, the hair cells of the BP are in contact with a basilar and a tectorial membrane. These membranes transmit mechanical vibrations. A cochlear aqueduct (CA) provides a connection between the cerebrospinal fluid that has a sodium rich space in coelacanth and tetrapods while the potassium rich endolymph is known in vertebrates. A unique feature is known in basic sarcopterygians, the intracranial joint, that never developed in actinopterygians and has been lost in lungfish and tetrapods. The BP in coelacanths is thought to generate pressure with the intracranial joint that will be transmitted to the CA. Lungs or a swim bladder are not forming in Chondrichthyes, structures that have a major impact on hearing in teleosts and tetrapods.

Application of an analytical approach to characterize the target strength of ancillary pelagic fish species

The lack of data on the species-specific Target Strength (TS) on ancillary species limits the application of acoustic surveys in assessing their abundance and distribution worldwide. The TS values of Scomber colias and Trachurus mediterraneus in use in the Mediterranean Sea rely on studies conducted on other species in the Atlantic and Pacific oceans. Nevertheless, the application of backscattering models offers the possibility to overcome the absence of empirical data handling the parameters that most affect the TS. X-ray scans were performed on 82 specimens to get digital representations of the swimbladder and the fish body which were used as input for the application of the Kirchhoff Ray Mode model to measure the TS as a function of frequency and tilt angle. The morphometric differences between the two species produced divergent relative frequency responses and broadband TS patterns. Moreover, comparing the results with one ex-situ experiment, we found a good agreement considering a mean tilt angle of - 10°, standard deviation = 12°. Our results provide the first theoretical insights into the use of backscattering models as a tool to distinguish between species in the Mediterranean Sea by acoustic method, increasing the knowledge of the acoustic reflectivity of ancillary species.

A single-cell atlas of West African lungfish respiratory system reveals evolutionary adaptations to terrestrialization

The six species of lungfish possess both lungs and gills and are the closest extant relatives of tetrapods. Here, we report a single-cell transcriptome atlas of the West African lungfish (Protopterus annectens). This species manifests the most extreme form of terrestrialization, a life history strategy to survive dry periods that can last for years, characterized by dormancy and reversible adaptive changes of the gills and lungs. Our atlas highlights the cell type diversity of the West African lungfish, including gene expression consistent with phenotype changes of terrestrialization. Comparison with terrestrial tetrapods and ray-finned fishes reveals broad homology between the swim bladder and lung cell types as well as shared and idiosyncratic changes of the external gills of the West African lungfish and the internal gills of Atlantic salmon. The single-cell atlas presented here provides a valuable resource for further exploration of the respiratory system evolution in vertebrates and the diversity of lungfish terrestrialization.

Outcomes and Complications Associated With Caudal Thoracic and Abdominal Air Sac Cannulation in 68 Birds

Air sac cannulation is used both as an emergency procedure in avian patients with severe upper respiratory compromise, as well as a means of routine ventilation for surgery of the head and neck. The objective of this retrospective study was to describe and quantify the complications associated with air sac cannulation in birds. Medical records were retrieved for all patients that underwent caudal thoracic or abdominal air sac cannulation at a single center between August 2004 and October 2020. Patient signalment, indication for air sac cannulation, location of air sac cannula (ASC) placement, occurrence and category of complications encountered, and survival data were recorded. Eighty-four ASCs were placed in 68 birds across 6 orders; 95.2% (80/84) of cases survived general anesthesia for initial ASC placement. The side and position of ASC placement were known in 33.3% (28/84) and 21.4% (18/84) of cases, respectively. Survival to ASC removal was known in 91.3% (73/80) of cases; 43 (58.9%) of these 73 cases survived to ASC removal. Complications were observed in 32.5% (26/80) of cases, and 11.5% (3/26) of cases died as a direct result of the complication. The most common reported ASC complication was loss of patency in 23.8% (19/80) of cases. Increased likelihoods for complications were seen in cases where exercise intolerance (P = 0.04) or abnormal respiratory sounds (P = 0.04) were reported at presentation. Increased likelihoods for survival to ASC removal were seen with intercostal placements (P = 0.049) and peri-interventional antibiotic therapy (P = 0.005). Decreased likelihood for survival to ASC removal was seen in cases where voice change was reported at presentation (P = 0.02). This study demonstrates a moderate risk of ASC complication, with a guarded overall prognosis for survival to ASC removal.

Monitoring for Anguillicoloides crassus, Anguillid herpesvirus 1, aquabirnavirus EVE and rhabdovirus EVEX in the European eel population of southern Spain

European eel is critically endangered in Europe. Among other stressors, pathogens are well-known to harm eels' fitness. One hundred and eighty-two eels were captured in three Eel Management Units in Andalucía (SE Spain) and analysed for Anguillicoloides crassus, Anguillid herpesvirus 1 (AngHV1), the rhabdovirus Eel Virus European X (EVEX) and the aquabirnavirus Eel Virus European (EVE). A. crassus adults and preadults were isolated and morphometrically identified, and the eel swimbladders were artificially digested to count A. crassus larvae. Also, eel tissues were examined by PCRs for the presence of viruses. EVEX and EVE were not detected in any of the eels. The estimated prevalence (95% confidence limits) was 71 (64-78)% for A. crassus and 35 (28-42)% for AngHV-1, varying these prevalences significantly between and within EMUs. Moreover, A. crassus prevalence was highest in smaller eels, in sites closest to the sea and eels sampled in the autumn. By contrast, AngHV-1 prevalence was highest in biggest eels, in sites far from the sea and sampled in the summer or winter. However, in mixed effects logistic models including site as a random variable, the risk of infection was associated with distance to the sea in both A. crassus and AngHV-1 infections and also to winter sampling in the case of AngHV-1 and not to other variables. These results are evidence that both pathogens are highly endemic in eels from Andalusian habitats. Further studies are needed to better understand the risk factors associated with these pathogens on eel populations.

Mesopelagic fish gas bladder elongation, as estimated from wideband acoustic backscattering measurements

Backscattered acoustic energy from a target varies with frequency and carries information about its material properties, size, shape, and orientation. Gas-bearing organisms are strong reflectors of acoustic energy at the commonly used frequencies (∼18-450 kHz) in fishery surveys, but lack of knowledge of their acoustic properties creates large uncertainties in mesopelagic biomass estimates. Improved knowledge about the volume and elongation (i.e., longest to shortest dimension) of swimbladders of mesopelagic fishes has been identified as an important factor to reduce the overall uncertainties in acoustic survey estimates of mesopelagic biomass. In this paper, a finite element approach was used to model gas-filled objects, revealing the structure of the backscattering, also at frequencies well above the main resonance frequency. Similar scattering features were observed in measured broadband backscattering of several individual mesopelagic organisms. A method is suggested for estimating the elongation of a gas-bubble using these features. The method is applied to the in situ measured wideband (33-380 kHz) target strength (TS) of single mesopelagic gas-bearing organisms from two stations in the North Atlantic (NA) and Norwegian Sea (NS). For the selected targets, the method suggested that the average elongation of gas-bladder at the NA and NS stations are 1.49 ± 0.52 and 2.86 ± 0.50, respectively.

Physical effects of sound exposure from underwater explosions on Pacific mackerel (Scomber japonicus): Effects on non-auditory tissues

Underwater explosions from activities such as construction, demolition, and military activities can damage non-auditory tissues in fishes. To better understand these effects, Pacific mackerel (Scomber japonicus) were placed in mid-depth cages with water depth of approximately 19.5 m and exposed at distances of 21 to 807 m to a single mid-depth detonation of C4 explosive (6.2 kg net explosive weight). Following exposure, potential correlations between blast acoustics and observed physical effects were examined. Primary effects were damage to the swim bladder and kidney that exceeded control levels at ≤333 m from the explosion [peak sound pressure level 226 dB re 1 μPa, sound exposure level (SEL) 196 dB re 1 μPa² s, pressure impulse 98 Pa s]. A proportion of fish were dead upon retrieval at 26-40 min post exposure in 6 of 12 cages located ≤157 m from the explosion. All fish that died within this period suffered severe injuries, especially swim bladder and kidney rupture. Logistic regression models demonstrated that fish size or mass was not important in determining susceptibility to injury and that peak pressure and SEL were better predictors of injury than was pressure impulse.

Aquaporin expression and cholesterol content in eel swimbladder tissue

Leakiness of the swimbladder wall of teleost fishes must be prevented to avoid diffusional loss of gases out of the swimbladder. Guanine incrustation as well as high concentrations of cholesterol in swimbladder membranes in midwater and deep-sea fish has been connected to a reduced gas permeability of the swimbladder wall. On the contrary, the swimbladder is filled by diffusion of gases, mainly oxygen and CO₂ , from the blood and the gas gland cells into the swimbladder lumen. In swimbladder tissue of the zebrafish and the Japanese eel, aquaporin mRNA has been detected, and the aquaporin protein has been considered important for the diffusion of water, which may accidentally be gulped by physostome fish when taking an air breath. In the present study, the expression of two aquaporin 1 genes (Aqp1aa and Aqp1ab) in the swimbladder tissue of the European eel, a functional physoclist fish, was assessed using immunohistochemistry, and the expression of both genes was detected in endothelial cells of swimbladder capillaries as well as in basolateral membranes of gas gland cells. In addition, Aqp1ab was present in apical membranes of swimbladder gas gland cells. The authors also found high concentrations of cholesterol in these membranes, which were several fold higher than in muscle tissue membranes. In yellow eels the cholesterol concentration exceeded the concentration detected in silver eel swimbladder membranes. The authors suggest that aquaporin 1 in swimbladder gas gland cells and endothelial cells facilitates CO₂ diffusion into the blood, enhancing the switch-on of the Root effect, which is essential for the secretion of oxygen into the swimbladder. It may also facilitate CO₂ diffusion into the swimbladder lumen along the partial gradient established by CO₂ production in gas gland cells. Cholesterol has been shown to reduce the gas permeability of membranes and thus could contribute to the gas tightness of swimbladder membranes, which is essential to avoid diffusional loss of gas out of the swimbladder.

Using the swimbladder as a respiratory organ and/or a buoyancy structure-Benefits and consequences

A swimbladder is a special organ present in several orders of Actinopterygians. As a gas-filled cavity it contributes to a reduction in overall density, but on descend from the water surface its contribution as a buoyancy device is very limited because the swimbladder is compressed by increasing hydrostatic pressure. It serves, however, as a very efficient organ for aerial gas exchange. To avoid the loss of oxygen to hypoxic water at the gills many air-breathing fish show a reduced gill surface area. This, in turn, also reduces surface area available for other functions, so that breathing air is connected to a number of physiological adjustments with respect to ion homeostasis, acid-base regulation and nitrogen excretion. Using the swimbladder as a buoyancy structure resulted in the loss of its function as an air-breathing organ and required the development of a gas secreting mechanism. This was achieved via the Root effect and a countercurrent arrangement of the blood supply to the swimbladder. In addition, a detachable air space with separated blood supply was necessary to allow the resorption of gas from the swimbladder. Gas secretion as well as gas resorption are slow phenomena, so that rapid changes in depth cannot instantaneously be compensated by appropriate volume changes. As gas-filled cavities the respiratory swimbladder and the buoyancy device require surfactant. Due to high oxygen partial pressures inside the bladder air-exposed tissues need an effective reactive oxygen species defense system, which is particularly important for a swimbladder at depth.

Swim bladder as a primary site of mycobacterial infection in Nothobranchius 'belly sliders'

The swim bladder inflates early after fish hatching via its interconnection with the digestive tract (ductus pneumaticus). This interconnection may serve as a portal to foreign particles, including bacteria, causing deficiencies in primary swim bladder inflation. We histologically examined 134 African annual killifish (genus Nothobranchius) with secondary loss of swim bladder function ('belly sliders'). We demonstrate that these fish lost the ability of air regulation in their swim bladders likely due to Mycobacterium spp. infection at an individual-specific age. Nearly all examined belly sliders had thickened swim bladder walls, and their swim bladder was filled with material containing mycobacteria, cell debris, young monocytic cells and phagocyting macrophages. Mycobacterial infection was restricted to the swim bladder in juveniles, where mycobacteria likely enter the host through the ductus pneumaticus. Infection in adults was systemic and mycobacteria were present in all examined organs. Presence of mycobacteria in the epithelial lining and submucosal layers of the digestive tract of adults suggests that it may also serve as the entrance site of infection. We suspect 2 sources of Mycobacterium contamination: dietary (with bloodworms) and/or contaminated hatching substrate. These sources of contamination may be eliminated by use of laboratory dry feed and egg disinfection prior to hatching.

Robotic soft swim bladder using liquid-vapor phase transition

The swim bladder is crucial to underwater robots to enhance their overall performance and to expand their range of motion. However, previous attempts to incorporate this function have failed or have adopted mechanical swim bladders with high-disturbances. This study presents an entirely soft swim bladder capable of controlling buoyancy selectively and noiselessly, making it applicable to sensitive underwater environments. The soft swim bladder, which consists of an elastic cover layer, flexible heating elements, and three expandable pouches filled with low boiling point fluid, can express four modes of motion by varying buoyancy: sinking, suspending, rising, and fast-rising. The varying buoyancy is achieved through liquid-vapor phase transition of the fluid in the selected pouches when Joule heated above its boiling temperature. Moreover, the swim bladder is integrated with a shape memory alloy-based fishtail to form a soft fish robot. The synergy between the bladder and the tail allows the robot to explore a total of ten disparate modes of maneuvers, and their dynamic performance has been evaluated. The results of this study present the potential for the soft swim bladder to be utilized in any underwater robotic applications to enhance their swimming performance.

Cervical air sac oxygen profiles in diving emperor penguins: parabronchial ventilation and the respiratory oxygen store

Some marine birds and mammals can perform dives of extraordinary duration and depth. Such dive performance is dependent on many factors, including total body oxygen (O2) stores. For diving penguins, the respiratory system (air sacs and lungs) constitutes 30-50% of the total body O2 store. To better understand the role and mechanism of parabronchial ventilation and O2 utilization in penguins both on the surface and during the dive, we examined air sac partial pressures of O2 (PO2 ) in emperor penguins (Aptenodytes forsteri) equipped with backpack PO2  recorders. Cervical air sac PO2  values at rest were lower than in other birds, while the cervical air sac to posterior thoracic air sac PO2  difference was larger. Pre-dive cervical air sac PO2  values were often greater than those at rest, but had a wide range and were not significantly different from those at rest. The maximum respiratory O2 store and total body O2 stores calculated with representative anterior and posterior air sac PO2  data did not differ from prior estimates. The mean calculated anterior air sac O2 depletion rate for dives up to 11 min was approximately one-tenth that of the posterior air sacs. Low cervical air sac PO2  values at rest may be secondary to a low ratio of parabronchial ventilation to parabronchial blood O2 extraction. During dives, overlap of simultaneously recorded cervical and posterior thoracic air sac PO2  profiles supported the concept of maintenance of parabronchial ventilation during a dive by air movement through the lungs.

Parental Males of the Plainfin Midshipman Are Physiologically Resilient to the Challenges of the Intertidal Zone

The decision of where to rear young is influenced by both the needs of offspring and the costs parents incur in certain rearing environments. Plainfin midshipman fish (Porichthys notatus) provide extended paternal care in rocky intertidal zones, where they experience regular bouts of aquatic hypoxia and air exposure during low-tide events. We investigated the physiological responses of plainfin midshipman males to three conditions for 6 h that simulate what these fish naturally experience during tidal cycles while nesting: normoxia, progressive hypoxia, or air exposure. Hypoxia- and air-exposed fish exhibited shifts in energy metabolites, driven largely by elevated lactate and glucose content and reduced glycogen content in several tissues (muscle, heart, liver, and brain), but the magnitude of these changes was relatively modest. Hematocrit increased most in air-exposed fish relative to normoxia-exposed fish, contributing to an increase in whole-blood hemoglobin concentration. Air exposure reduced swim bladder oxygen content, suggesting that internal O₂ stores are drawn on during air exposure. In a second experiment, we found that aquatic surface respiration and gill ventilation frequency increased in hypoxia-exposed fish relative to normoxia-exposed fish. Overall, our results suggest that plainfin midshipman overcome the challenges of the intertidal environment through a variety of physiological strategies and exhibit little physiological disturbance in response to the fluctuating and extreme conditions created by regular low tides.

A mechanical approach to understanding the impact of the nematode Anguillicoloides crassus on the European eel swimbladder

One of the most detrimental factors in the drastic decline of the critically endangered European eel (Anguilla anguilla) was the inadvertent introduction of the invasive nematode Anguillicoloides crassus Infection primarily affects the swimbladder, a gas-filled organ that enables the eel to control its depth in the water. A reduction in swimbladder function may be fatal for eel undergoing their spawning migration to the Sargasso Sea, a journey of over 5000 km. Although the physiological damage caused by this invasive parasite is well studied through the use of quantifiable gross pathological indices, providing a good measure of the swimbladder health status, they cannot separate the role of mechanical and morphological damage. Our study examined the appropriateness of three commonly used indices as a measure of mechanical damage by performing uniaxial tensile tests on swimbladder specimens obtained from an infected eel population. When the test results were compared with the gross pathological indices it was found that thickness correlated most strongly with mechanical damage, both confirming and, more importantly, explaining the counterintuitive findings of earlier work. In a damaged swimbladder, the immune response leads to a trade-off; increasing wall thickness raises the pressure required for organ rupture but decreases strength. The results indicate that for moderate infection the mechanical integrity of the swimbladder can be maintained. For severe infection, however, a reduction in mechanical integrity may reach a tipping point, thereby affecting the successful completion of their oceanic migration.

Swim bladder enhances lagenar sensitivity to sound pressure and higher frequencies in female plainfin midshipman (Porichthys notatus)

The plainfin midshipman fish (Porichthys notatus) is an established model for investigating acoustic communication because the reproductive success of this species is dependent on the production and reception of social acoustic signals. Previous work showed that female midshipman have swim bladders with rostral horn-like extensions that project close to the saccule and lagena, while nesting (type I) males lack such rostral swim bladder extensions. The relative close proximity of the swim bladder to the lagena should increase auditory sensitivity to sound pressure and higher frequencies. Here, we test the hypothesis that the swim bladder of female midshipman enhances lagenar sensitivity to sound pressure and higher frequencies. Evoked potentials were recorded from auditory hair cell receptors in the lagena in reproductive females with intact (control condition) and removed (treated condition) swim bladders while pure tone stimuli (85-1005 Hz) were presented by an underwater speaker. Females with intact swim bladders had auditory thresholds 3-6 dB lower than females without swim bladders over a range of frequencies from 85 to 405 Hz. At frequencies from 545 to 1005 Hz, only females with intact swim bladders had measurable auditory thresholds (150-153 dB re. 1 µPa). The higher percentage of evoked lagenar potentials recorded in control females at frequencies >505 Hz indicates that the swim bladder extends the bandwidth of detectable frequencies. These findings reveal that the swim bladders in female midshipman can enhance lagenar sensitivity to sound pressure and higher frequencies, which may be important for the detection of behaviorally relevant social signals.

Description of a new species of Triplophysa (Teleostei: Nemacheilidae) from Guizhou Province, China

A new cave-dwelling fish species Triplophysa guizhouensis is described based on specimens collected from Guizhou, China, in a subterranean system interconnected with the Hongshui River drainage. The species can be distinguished from its congeners by a combination of characters: eyes present; caudal fin with 14 branched rays; inner gill rakers of first gill arch 8-10; posterior chamber of air bladder developed; and body posterior of dorsal fin scaled. A key to species of Triplophysa in the Pearl River basin is provided.

Passive acoustic monitoring, development of disturbance calls and differentiation of disturbance and advertisement calls in the Argentine croaker Umbrina canosai (Sciaenidae)

Disturbance and advertisement calls of the Argentine croaker Umbrina canosai were recorded from coastal Uruguayan waters. Dissections indicate typical sciaenid extrinsic swimbladder muscles present exclusively in males. Disturbance calls were produced when captive U. canosai were startled, chased with a net or grabbed by the tail. Calls were unusual for sciaenids because each pulse consisted of multiple cycles. The number of cycles per pulse and dominant frequency did not change with U. canosai size, but pulse duration and interpulse interval increased. Advertisement calls were recorded from unseen choruses in the field and confirmed with captive individuals in a large tank. Advertisement calls were recorded throughout the known range of the species in Uruguay indicating a continuous belt of spawning populations. Tank recordings of the same individuals permitted explicit comparisons between the two calls. Advertisement call pulses averaged 2·4 more cycles (11·0-8·6) although pulses of both calls were basically similar as were durations and dominant frequencies. Pulse number, however, differed markedly, averaging 13·6 and 3·4 pulses for disturbance and advertisement calls respectively. Furthermore, disturbance calls were produced as a rapid series with an interpulse interval of 26-31 ms whereas advertisement call patterns were less stereotyped and ranged from <100 to 450 ms. Multicycle pulses distinguished U. canosai from other sympatric sciaenids.

Morphological features of an endangered Japanese strain of Cyprinus carpio: reconstruction based on seven SNP markers

Morphological analyses of 183 specimens of Japanese common carp Cyprinus carpio (171 from Lake Biwa and 12 from nursery ponds) using genetic hybrid indices demonstrated that the typical native Japanese strain of C. carpio has a more elongate body, more branched dorsal-fin rays, fewer and shorter gill rakers, more developed pneumatic bulb, more coiled pneumatic duct, longer posterior swimbladder and shorter intestine than the typical introduced C. carpio. These results provide a basis for a better understanding of the ecological characteristics and taxonomic status of the endangered Japanese strain of C. carpio.

Biomimicking of a Swim Bladder and Its Application as a Mini-Generator

A model fish with a man-made swim bladder achieves fast vertical motions based on density adjustments in a pressure-responsive way. When exposed to a magnetic field, a mini-generator is achieved by harvesting energy from the environment, working with pressure differences in the blood-pressure range and at the frequency of a beating heart.

Osteological and Soft-Tissue Evidence for Pneumatization in the Cervical Column of the Ostrich (Struthio camelus) and Observations on the Vertebral Columns of Non-Volant, Semi-Volant and Semi-Aquatic Birds

Postcranial skeletal pneumaticity (PSP) is a condition most notably found in birds, but that is also present in other saurischian dinosaurs and pterosaurs. In birds, skeletal pneumatization occurs where bones are penetrated by pneumatic diverticula, membranous extensions that originate from air sacs that serve in the ventilation of the lung. Key questions that remain to be addressed include further characterizing (1) the skeletal features that can be used to infer the presence/absence and extent of PSP in birds and non-avian dinosaurs, and (2) the association between vertebral laminae and specific components of the avian respiratory system. Previous work has used vertebral features such as pneumatic foramina, fossae, and laminae to identify/infer the presence of air sacs and diverticula, and to discuss the range of possible functions of such features. Here, we tabulate pneumatic features in the vertebral column of 11 avian taxa, including the flightless ratites and selected members of semi-volant and semi-aquatic Neornithes. We investigate the associations of these osteological features with each other and, in the case of Struthio camelus, with the specific presence of pneumatic diverticula. We find that the mere presence of vertebral laminae does not indicate the presence of skeletal pneumaticity, since laminae are not always associated with pneumatic foramina or fossae. Nevertheless, laminae are more strongly developed when adjacent to foramina or fossae. In addition, membranous air sac extensions and adjacent musculature share the same attachment points on the vertebrae, rendering the use of such features for reconstructing respiratory soft tissue features ambiguous. Finally, pneumatic diverticula attach to the margins of laminae, foramina, and/or fossae prior to their intraosseous course. Similarities in PSP distribution among the examined taxa are concordant with their phylogenetic interrelationships. The possible functions of PSP are discussed in brief, based upon variation in the extent of PSP between taxa with differing ecologies.

Effect of drying and frying conditions on physical and chemical characteristics of fish maw from swim bladder of seabass (Lates calcarifer)

BACKGROUND

Swim bladder is generated as a by-product during evisceration. It has been used for the production of fish maw, in which several processing parameters determine the characteristics or quality of the resulting fish maw. The present study aimed to investigate the characteristics of fish maws from seabass swim bladder as influenced by drying and frying conditions.

RESULTS

The expansion ratio and oil uptake content of fish maw increased as the moisture content of swim bladder increased (P < 0.05). Nevertheless, the expansion ratio of fish maw decreased when the moisture content was higher than 150 g kg(-1) . The L*-value decreased, whilst the a*- and b*-values of fish maw increased with increasing moisture content. When pre-frying and frying temperatures increased, the expansion ratio of fish maw increased (P < 0.05). However, the expansion ratio decreased when the frying was performed at a temperature higher than 200 °C. The oil uptake contents of fish maw with frying temperatures of 180 and 200 °C were in the range of 451.06-578.06 g kg(-1) , whereas the lower contents (378.60-417.17 g kg(-1) ) were found in those having frying temperatures of 220-240 °C. Hardness of fish maw decreased but no changes in fracturability were observed with increasing pre-frying temperature when subsequent frying was carried out 200 °C.

CONCLUSION

Drying temperatures, moisture content, pre-frying and frying temperatures were the factors influencing the characteristics and properties of fish maws from seabass swim bladder. Fish maw could be prepared by pre-frying swim bladder, dried at 60 °C to obtain 150 g kg(-1) moisture content, at 110 °C for 5 min, followed by frying at 200 °C for 20 s.

Comment on "Resonant acoustic scattering by swimbladder-bearing fish" [J. Acoust. Soc. Am. 64, 571-580 (1978)] (L)

Love's model for the acoustic scattering by a spherical viscous fluid shell filled with gas and surrounded by inviscid liquid [J. Acoust. Soc. Am. 64, 571-580 (1978)] is reviewed. For certain material parameters, discrepancies are observed in Love's scattering cross section when compared with the exact solution near resonance. Those errors are corrected in this study. It is shown that there is excellent agreement between the corrected formulation and the exact solution in the resonance region where ka=1 and ε = b/a ≥ 2.5, where k is the acoustic wavenumber, and a and b are the inner and outer radii of the shell, respectively. Errors between Love's equation and the exact solution are not significant for the case of swimbladder-bearing fish where the bubble radius is typically greater than about 0.05 m, but could be large for bubbles and gas-bearing zooplankton where the radius is less than about 0.05 m.

Effects of the air sac thickness on ventilation by a 1D model of an avian respiratory system

Airflow in an avian respiratory system was simulated to study why birds affected with airsacculitis have respiratory distress. The airflow in the avian lung was modeled with a 1D electrical circuit and simulated for investigating what effect an increase in wall thickness of air sacs caused by airsacculitis has on flow in lung. The results demonstrated that thickening of the air sac wall caused anti-synchronization between an elastic recoiling force of the air sac walls and an intra-pleural pressure, bringing difficulties in expansion of air sacs to draw in airs during an inspiration period and thereby decreasing air to be pumped out during an expiration period. This was reflected in a decrease in air flow volume in parabronchi where gas exchange takes place. Therefore, it was concluded that airsacculitis causes imbalance in air flow dynamics in the avian lung and thus impairs breathing ability of birds.

Evolution of archosaurian body plans: skeletal adaptations of an air-sac-based breathing apparatus in birds and other archosaurs

Living birds represent the only extant sauropsid group in which pulmonary air sacs pneumatize the postcranial skeleton. Notable in this regard is an extraordinary degree of variability, ranging from species that are completely apneumatic to those characterized by air within the entire postcranial skeleton. Although numerous factors (e.g., body size) have been linked with "relative" pneumaticity, comparative studies examining this system remain sparse. This project sought to (1) characterize whole-body patterns of skeletal pneumaticity in distantly related neognath birds and (2) evaluate putative relationships among relative pneumaticity, body size and locomotor specializations. Pneumaticity profiles were established for 52 species representing 10 higher-level groups. Although comparisons reveal relatively conserved patterns within most lower-level clades, apparent size- and locomotor-thresholds do impart predictable deviations from the clade norm. For example, the largest flying birds (vultures, pelicans) exhibit hyperpneumaticity (i.e., pneumaticity of distal limb segments) relative to smaller members of their respective clades. In contrast, skeletal pneumaticity has been independently lost in multiple lineages of diving specialists (e.g., penguins, auks). The application of pneumaticity profiling to extinct archosaurs reveals similar trends in body size evolution, particularly when examining patterns of pneumaticity in a size-diverse assemblage of pterosaurs (flying "reptiles"). As a fundamental organizing system, skeletal pneumaticity may play a role in relaxing constraints on body size evolution by allowing volumetric increases without concomitant increases in body mass. Not only might this be critical for taxa (birds, pterosaurs) exploiting the energetically costly aerial environment, but could be beneficial for any large-bodied terrestrial vertebrates such as the dinosaurs.

Development and physiology of gastric dilation air sacculitis in Chinook salmon, Oncorhynchus tshawytscha (Walbaum)

The syndrome known as gastric dilation air sacculitis (GDAS) has previously been shown to affect Chinook salmon, Oncorhynchus tshawytscha, in seawater (SW) aquaculture. Feed and osmoregulatory stress have been implicated as potential epidemiological co-factors. The development and physiology of GDAS was investigated in SW and freshwater (FW) adapted smolts. Diet A (low-cohesion pellets) and diet B (high-cohesion pellets) were fed to both FW- and SW-adapted fish. GDAS was induced only in the SW trial on feeding diet A. Stimulated gastro-intestinal (GI) smooth muscle contractility, and fluid transport by the pyloric caeca were different in GDAS-affected fish, which also showed osmoregulatory dysfunction. Cardiac stomach (CS) smooth muscle contractility in response to acetylcholine and potassium chloride (KCl) was significantly reduced in fish fed diet A relative to controls from weeks 3-5. In contrast, maximal pyloric sphincter (PS) circular smooth muscle contraction in response to KCl was significantly elevated in fish fed diet A in weeks 4 and 5. Serum osmolality was elevated in GDAS-affected fish from week 2 of the SW trial. Fluid transport from the mucosal to serosal surface of isolated pyloric caeca was significantly reduced in weeks 3, 4 and 5 in SW fish fed diet A. Gastric evacuation from the stomach of healthy fish was shown to be significantly different when diets of low- and high-cohesion were fed. The results are consistent with the intestinal brake playing a role in the development of the disease.

Near-resonance scattering from arrays of artificial fish swimbladders

The air-filled swimbladders of fish resonate like damped air bubbles, and are very efficient acoustic scatterers at low to mid frequencies (typically <20 kHz). Scattering experiments were performed on an artificial "fish school" constructed from polyethylene bubbles. A mathematical model, developed to describe near-resonance backscattering from schooling fish [J. Acoust. Soc. Am. 99, 196-208 (1996)], was used to analyze the physical behavior for three different arrays of these bubbles. The measurements gave excellent agreement with the model, showing that coupled-resonance and interference effects cause the frequency response of tightly packed arrays, with spacing corresponding to the order of a body length for fish, to differ significantly from those of more dispersed arrays. As the array spacing is increased to the equivalent of several body lengths, these effects rapidly diminish. The results of this comparison demonstrate that, at low to mid frequencies, coupled resonance and interference effects are likely in schooling fish, and need to be considered in applications of underwater acoustic methods to the study of fish populations.

Endoscopic examination of snakes by access through an air sac

Sixteen boa constrictors (Boa constrictor), three royal pythons (Python regius) and 15 Burmese pythons (Python molurus bivittatus) were examined endoscopically by access through the air sac. The snakes were immobilised in a ventral position using a half-open anaesthetic system with assisted ventilation and a mixture of isoflurane and oxygen. The rigid endoscope was introduced percutaneously and the internal structure of the lungs and the air sac, and the shape, size and external surface of the liver were visible in the cranial direction. In the smaller snakes the bifurcation and caudal part of the trachea could be viewed, provided the endoscope was positioned in a retrograde orientation. The caudal orientation of the endoscope made it possible to view the gall bladder and the size, shape and surface of the spleen. In some cases, the pancreas and the surface of the stomach and colon could be monitored. Endoscopy through the air sac also made it possible to check the major veins in the coelom. The snakes were monitored for at least 30 days after the intervention and no changes in their respiratory function or general health were observed.

Caudal thoracic air sac cannulation in zebra finches for isoflurane anesthesia

Small songbirds such as the zebra finch are commonly used for studies on the neural mechanisms that underlie vocal learning. For these studies, survival surgeries are often performed that involve animal anesthesia and stereotaxic stabilization for localization of specific brain regions. Here we describe air sac cannulation as a novel method for delivering isoflurane gas to zebra finches for anesthesia during neurosurgery. Advantages of this method include that it leaves the bird's head free for stereotaxic targeting and does not interfere with the beak clamps that are often used to position and stabilize the head. It additionally allows for the use of the inhalant anesthetic, isoflurane, which is an appealing alternative to injectable anesthetics because it provides fast, minimally stressful induction, and low subject and personnel toxicity. The use of isoflurane also prevents overdosing and lengthy postoperative recovery times.

Measurement of an individual silver perch Bairdiella chrysoura sound pressure level in a field recording

Simultaneous audio and video were recorded of a silver perch Bairdiella chrysoura producing its characteristic drumming sound in the field. The background noise contribution to the total sound pressure level is estimated using sounds that occurred between the pulses of the silver perch sound. This background contribution is subtracted from the total sound to give an estimate of the sound pressure level of the individual fish. A silver perch source level in the range 128-135 dB (re: 1 microPa) is obtained using an estimate of the distance between the fish and the hydrophone. The maximum distance at which an individual silver perch could be detected depends on the background sound level as well as the propagation losses. Under the conditions recorded in this study, the maximum detection distance would be 1-7 m from the hydrophone.

Changes in volume reverberation from deep to shallow water in the eastern Gulf of Mexico

Scattering from fish is a primary cause of volume reverberation and, since fish populations change from deep to shallow water, the character of volume reverberation should also change. However, there are few data available to document expected changes. Therefore, an experiment was conducted in the eastern Gulf of Mexico to investigate possible changes in volume reverberation from deep to slope to shelf waters. Results showed that volume reverberation in outer shelf waters varied more rapidly with respect to both time and space than that in deeper waters. Day-time scattering was similar for deep, slope and shelf waters, total scattering strengths generally increased with frequency. Night-time scattering for the deep ocean and slope also increased with increasing frequency. Scattering modeling suggests that swimbladder-bearing fishes smaller than 10 cm were responsible for the observed volume reverberation. Night-time scattering at the outer shelf location was very different, with strong scattering peaks at low frequencies. Scattering modeling implicates 12-15 cm rough scad and round herring as potential causes of the low frequency peaks. Hence, experiment results confirmed that, as expected, volume reverberation over shelf waters is different and more variable than in deeper waters of the eastern Gulf of Mexico.

Experimental production of gastric dilation and its association with osmoregulatory stress and biogenic amines in chinook salmon, Oncorhynchus tshawytscha (Walbaum)

Chinook salmon smolt in fresh water fed a commercial diet known to produce minimal gastric dilation and air sacculitis (GDAS) were randomly assigned to four experimental tanks with flow-through sea water. All four groups were acclimatized to sea water for 3 weeks and fed a diet of minced fresh seafood. After 3 weeks the groups were fed either; seafood as before, a different commercial pelleted diet associated with the development of GDAS on farms, or either diet supplemented with 500 mg L(-1) putrescine, 300 mg L(-1) cadaverine and 250 mg L(-1) tyramine. Gastric dilation was produced in fish fed the commercial diet for 1 month but not by feeding a diet of minced seafood. The addition of putrescine, cadaverine and tyramine to either diet had no significant effect on the development of gastric dilation. Fish fed the commercial diet had significantly (P < 0.0001) wider weight-adjusted stomach widths, less prominent longitudinal stomach folds (P < 0.0001) and lower (P < 0.0001) stomach-width ratios than fish fed the fresh seafood diet. There was no significant difference in serum osmolality or sodium concentration between fish from groups with or without gastric dilation or fed biogenic amines.

The effect of airsacculitis on bird weights, uniformity, fecal contamination, processing errors, and populations of Campylobacter spp. and Escherichia coli

A study was conducted to determine if the presence of airsacculitis in broiler chickens contributes to loss of saleable yield, lack of uniformity, fecal contamination, processing errors, and increases in populations of pathogenic and indicator bacteria. In a commercial processing facility, groups of carcasses from airsacculitis (AS)-positive (ASP) and airsacculitis-negative (ASN) flocks were selected from the line and weighed, evaluated for cut or torn areas on the digestive tracts, and assessed for Campylobacter and Escherichia coli counts. Additionally, fecal contamination was monitored and recorded. The presence of AS reduced (P < or = 0.05) carcass weight averages in two of five repetitions. Although not significantly different in repetitions 1, 4, and 5, the means were higher for ASN flocks. The net loss averaged over five repetitions was 84 g/carcass, equating to a loss of 14,686.9 k (32,379 lb) of chicken meat for one growout house per year as the result of AS infection. ASP carcasses had higher (P < or = 0.05) fecal contamination in four of five repetitions. The number of total digestive tract cuts or tears were much higher on ASP carcasses at 42, 49, 37, 60, and 59% as compared to 14, 12, 17, 24, and 16% for ASN carcasses in repetitions 1 to 5, respectively. In three of the five replications, the presence of AS in the flocks increased (P < or = 0.05) the number of Campylobacter recovered from broiler carcasses. Hence, there appears to be a relationship between the presence of AS and Campylobacter-positive carcasses. Escherichia coli counts for ASP flocks were significantly higher than ASN flocks in repetitions 1 and 3. In repetition 5, E. coli numbers were significantly lower for the AS flock. These data differ from previous unpublished data from two separate pilot studies that demonstrated that E. coli counts for ASP flocks are significantly higher than ASN flocks. This difference may be attributed to the fact that in the pilot studies visibly infected carcasses were sampled, and in this study healthy birds that had passed inspection were sampled within an ASP flock. Because flocks of chickens showing signs of AS have lower weights, more fecal contamination, more processing errors, and higher levels of Campylobacter spp., broiler companies should emphasize control of AS in the flocks as a means of preventing subsequent food-borne bacterial infection.

Systemic and mucosal antibody responses to selected cell surface antigens of avian pathogenic Escherichia coli in experimentally infected chickens

The immune response to four cell surface antigens of avian pathogenic Escherichia coli (APEC) was investigated as the first step in identifying vaccine candidates. F1 pilus adhesin, P pilus adhesin, aerobactin receptor protein, and lipopolysaccharide (LPS) from an O78 E. coli (strain EC99) were used as antigens. The proteins were purified as 6xhistidine-tagged recombinant proteins and LPS was purified from a phenol/water extract. Groups of 12 broiler chickens were vaccinated intranasally with the EC99 strain and challenged with the same strain 10 days later via the intra-air sac route. The chickens that survived were euthanatized 10 days postchallenge. Scores were assigned to infected chickens on the basis of lesions and recovery of the challenge E. coli. The immunoglobulin (Ig) IgG, IgA, and IgM antibodies to the four antigens were measured in serum and air sac washings in an enzyme-linked immunosorbent assay. Among the chickens that were not vaccinated prior to challenge, two died and three of the survivors were ill, whereas, of the chickens that were vaccinated prior to challenge, one died and one of the survivors became ill. After the intranasal vaccination, high antibody activity against all four antigens was associated with each Ig isotype in serum and air sac washings. IgG was the predominant isotype of Ig in air sac washings as detected by radial immunodiffusion. Chickens that were not ill after challenge had greater IgG, IgA, and IgM antibody activity against all four antigens in serum and air sac washings than did sick chickens. Thus, all of the antigens tested appear to be suitable candidates for a vaccine to protect chickens from respiratory tract infections caused by APEC.

Effect of early handling of turkey poults on later responses to a dexamethasone-Escherichia coli challenge. 1. Production values and physiological response

The stress responses of mice and rats has been shown to be permanently altered by brief, gentle handling during the first 10 d of life, resulting in increased BW and resistance to stress-induced immunosuppression. The purpose of this study was to determine whether early handling of turkey poults could permanently affect production values and physiology of adult turkeys. Turkey poults were handled 0, 1 (1x), or 2 (2x) times daily for the first 10 d after hatch. Handling consisted of gently catching each poult and holding it for 10 s. On Day 11 after hatch, half of the birds from each handling treatment were treated with three injections of 2 mg dexamethasone (DEX)/kg BW on alternating days. On the day of the third DEX injection, duplicate pens of birds were also inoculated in the airsac with 0 or 50 cfu of Escherichia coli. The same birds were treated with a second series of DEX injections at 5 wk of age. Two weeks later, all birds were weighed, and 3 wk later four birds per pen were bled and 10 birds per pen were necropsied; relative organ weights were then determined. Surviving birds were treated with a third series of DEX injections at 10 wk of age; 2 wk later, all surviving turkeys were bled, weighed, and necropsied. Feed consumption was determined weekly. There were no differences due to handling treatment on the body weights or on the relative organ weights of birds that died after the first DEX treatment. Birds treated with a second DEX injection at 5 wk of age and handled 1x daily had decreased BW. Those handled 1x or 2x daily had higher feed conversion ratios. Surviving birds that were given a third DEX treatment had higher BW and no difference in feed conversion when handled 1x or 2x daily. Relative liver, heart, and spleen weights were affected by handling of DEX-E. coli-treated birds, as were serum chemistry values for calcium, iron, glucose, total protein, blood urea nitogen, uric acid, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and gamma-glutamyltransferase. Handling also affected the numbers of white blood cells of DEX-treated birds. These results indicate that brief and gentle handling of turkey poults during the first 10 d after hatch has lasting effects on production values and physiology of adult turkeys and that these effects can be positive or negative. These results suggest a genetic divergence in the response to stress and its effect on production values and physiology of commercial turkey populations.

Comparative study of sequential expression of the organizer-related genes in normal Cynops pyrrhogaster embryos and mesodermalized ectoderm

An artificially mesodermalized ectoderm (mE) of early Cynops pyrrhogaster gastrula acquires the organizer property; the mE is able to induce the secondary axis. The expression of organizer-related genes was investigated during the mesodermalizing process of the mE. The expression of C. pyrrhogaster organizer-related genes, such as bra, gsc, lim-1, chd and noggin, were analyzed. Cynops pyrrhogaster shh expression was also investigated. The organizer-related genes were activated by 12 h after the mesoderm-inducing stimulus. It was noted that there was a temporal gap in the expression of each gene. The expression of bra and gsc seemed to be more quickly activated during the mesodermalizing process. While expression of lim-1 and noggin was activated later than that of bra and gsc, lim-1 expression was earlier than chd and noggin expression. Shh expression was activated later than lim-1/noggin. The present study suggests the possibility that the bra/gsc, lim-1, chd, noggin and shh genes are expressed one by one in that order during the mesodermalizing of the presumptive ectoderm. It also indicates that the sequence is not always consistent with that of the whole embryo during normal embryogenesis. The meaning of the discrepancy will be discussed in connection with the cascade of certain genes expressed during the mesodermalizing process.

Construction and evaluation of a delta cya delta crp Salmonella typhimurium strain expressing avian pathogenic Escherichia coli O78 LPS as a vaccine to prevent airsacculitis in chickens

Avian pathogenic strains of Escherichia coli cause a number of extraintestinal diseases in poultry, including airsacculitis and colisepticemia. Expression of O78 lipopolysaccharide (LPS) is frequently associated with pathogenic isolates. Salmonella, a common poultry contaminant, is a major public health concern. The purpose of this work was to develop an E. coli vaccine for poultry with the use of an attenuated Salmonella typhimurium carrier that would benefit both the bird and the consumer. Orally administered attenuated S. typhimurium delta cya delta crp strains have been shown to provide excellent protection against wild-type Salmonella challenge in chickens. This work describes the construction of a delta cya delta crp derivative of an avian pathogenic S. typhimurium that expresses both the homologous group B determinants (O1,4,5,12) and the heterologous E. coli O78 LPS O antigens. This was accomplished by inserting the E. coli rfb region, which encodes the genes required for O78 expression, into the chromosomal cya gene of S. typhimurium, creating a defined deletion/insertion mutation. A delta crp mutation was introduced in a subsequent step. Expression of both O antigens was stable in vitro and in vivo. Vaccination of white leghorn chicks at day of hatch and 14 days with the recombinant vaccine strain induced serum immune responses against both S. typhimurium and E. coli LPS and protected the birds against subsequent challenge with an avian pathogenic E. coli O78 strain. Introduction of a mutation in rfc, which encodes the O antigen polymerase, reduced the chain length of the S. typhimurium LPS without affecting the expression of O78. The rfc mutation further enhanced the ability of the vaccine strain to protect chickens against E. coli challenge.

The secretion of oxygen into the swim-bladder offish. II. The simultaneous transport of carbon monoxide and oxygen

Toadfish, Opsanus tau, L., were maintained in sea water equilibrated with gas mixtures containing a fixed proportion of oxygen and varying proportions of carbon monoxide. The swim-bladder was emptied by puncture, and, after an interval of 24 or 48 hours, the newly secreted gases were withdrawn and analyzed. Both carbon monoxide and oxygen are accumulated in the swim-bladder at tensions greater than ambient. The ratio of concentrations, carbon monoxide (secreted): carbon monoxide (administered) bears a constant relation to the ratio, oxygen (secreted): oxygen (administered). The value of the partition coefficient describing this relation is (alpha = 5.44). The two gases are considered to compete for a common intracellular carrier mediating their active transport. The suggestion is advanced that the intracellular oxygen carrier is a hemoglobin. Comparison of the proportions of carboxy- and oxyhemoglobin in the blood with the composition of the secreted gas proves that the secreted gases are not evolved directly from combination with blood hemoglobin. The suggestion is advanced that cellular oxygen secretion occurs in the rete mirabile: the rete may build up large oxygen tensions in the gas gland capillaries. It is suggested that the gas gland acts as a valve impeding back diffusion of gases from the swim-bladder.

The secretion of oxygen into the swimbladder of fish. I. The transport of molecular oxygen

Fish were maintained in sea water equilibrated with a gas mixture containing a non-equilibrium mixture of the three molecular species of oxygen, O¹⁸-O¹⁸ (mass 36), O¹⁸-O¹⁶ (mass 34), and O¹⁶-O¹⁶ (mass 32). Analyses in the mass spectrometer, of the gases secreted into the swim-bladder showed that no change in the relative abundance of these three molecular species had occurred during the secretory process and that therefore no exchange of atoms between oxygen molecules had occurred. Scission of the oxygen-oxygen bond probably does not occur during the transport process. It is concluded that the active transport of oxygen into the swim-bladder by the gas gland is a transport of molecular oxygen.

[Percutaneous occlusion of arterial vessels using permanent embolization for the treatment of an air sac hemorrhage in horses. A case report]

This article reports a case of guttural pouch bleeding which was managed successfully by using intravascular embolisation systems to occlude the damaged vessels. Percutaneous catheterisation of the common carotid artery allowed angiographic visualisation of the main head arteries: A. carotis externa, A. carotis interna and A. occipitalis, which showed no abnormalities angiographically. Originating from the A. occipitalis, one artery sent smaller, extensively branching and tortuous vessels to the guttural pouch area. This branching was interpreted as a sign of inflammatory hypervascularization. The artery was occluded by positioning of a detachable balloon distally of the origin of the two small vessels. Insertion of two coils in the A. occipitalis proximally of the origin of this artery completed the embolisation. Occlusion of the distal part was necessary to avoid blood supply to the lesion from the contralateral arterial system via the circle of Willis. The technique used allowed occlusion of a selected head artery without direct surgical intervention in this area. There is no need to remove the implants. After catheterisation, no more episodes of epistaxis occurred. The causing diphtheroid inflammation in the guttural pouch was treated by local infusions of iodine-solutions and resolved completely within 24 days.

Differential effects of inhibition of isoforms of cyclooxygenase (COX-1, COX-2) in chronic inflammation

OBJECTIVE AND DESIGN

The anti-inflammatory effects of therapeutic dosing of drugs with greater selectivity for the inhibition of the constitutive (COX-1) or inducible isoform (COX-2) of cyclooxygenase were assessed in a model of chronic inflammation.

METHODS

The murine chronic granulomatous tissue air pouch model involves the subcutaneous injection of air into the dorsum of mice followed 24 h later by the intrapouch injection of an inflammatory stimulus (0.5 ml of Freund's complete adjuvant containing 0.1% croton oil). Aspirin, more selective in vitro for the inhibition of COX-1 (10,200 (mg/kg) and nimesulide, a selective in vitro inhibitor of COX-2 (0.5, 5 mg/kg) were dosed p.o. daily from 3 days after injection of the inflammatory stimulus. Granuloma dry weight, vascularity and COX activity (measured as PGE2) were assessed at various time points throughout the inflammatory lesion to resolution at day 28. A second COX-2 inhibitor, NS 398 (0.1, 1, 10 mg/kg), was dosed p.o. daily from 3 days after the injection of the inflammatory stimulus and its effects on granuloma dry weight, vascularity and COX activity were measured at 7 days.

RESULTS

Aspirin (200 mg/kg) significantly inhibited levels of PGE2 throughout the time course and at the lower dose (10 mg/kg) from day 14. Nimesulide (5 mg/kg) however, significantly increased levels of PGE2 at days 5 and 21, but at 0.5 mg/kg was without effect. Aspirin (200 mg/kg) significantly reduced granuloma dry weight at day 14 but had no effect on granuloma vascularity at day 7. In contrast, nimesulide (5 mg/kg) significantly increased granuloma vascularity at day 7 and granuloma dry weight at day 14. NS-398 at all doses had no effect on granuloma dry weight, vascularity or COX activity 7 days after the injection of the inflammatory stimulus.

CONCLUSION

In this model of chronic inflammation, aspirin, more selective for the inhibition of COX-1 is more effective than the selective COX-2 inhibitors nimesulide and NS-398 at inhibiting granuloma dry weight, vascularity and COX activity.

Localization of the in vivo expression of P and F1 fimbriae in chickens experimentally inoculated with pathogenic Escherichia coli

Escherichia coli causing septicemia in poultry often possess F1 (type 1) and/or P fimbriae which may be involved in bacterial colonization and infection. To investigate the expression of these fimbriae in vivo, two pathogenic E. coli strains with different fimbrial profiles, TK3 (fim+/pap+) and MT78 (fim+/pap-), were administered to 2-week-old chickens by either the intratracheal or caudal thoracic air sac inoculation route. Antibodies specific for native F1 fimbriae were detected by ELISA and immunodot in the serum of chickens inoculated with either strain MT78 or strain TK3, irrespective of the route of inoculation. Antibodies specific for P fimbriae of serotype F11 were detected by ELISA and immunoblotting in the serum of chickens inoculated by either route with strain TK3. F1, but not P fimbriae, were expressed by bacteria colonizing the trachea of chickens inoculated by the air sac route with strain MT78 or TK3, as demonstrated by examination of frozen tissue sections using immunofluorescence. F1 fimbriae were also expressed by bacteria colonizing the air sacs and lungs, but not by bacteria in the blood or other internal organs, of chickens inoculated with either strain. P fimbriae were expressed by bacteria colonizing the air sacs, lungs, kidney, blood, and pericardial fluid, but not by bacteria colonizing the trachea, of chickens inoculated with strain TK3. Fimbriae-like structures were observed by electron microscopy on bacteria adhering to the epithelial cells of the air sacs of chickens inoculated with strain TK3. These results demonstrate that both strains MT78 and TK3 undergo in vivo phase variation with respect to their fimbrial profiles and site of bacterial colonization in different organs of infected chickens and suggest that F1 fimbriae are important for initial bacterial colonization of the upper respiratory tract whereas P fimbriae are important for later stages of the infection.

THE SECRETION OF OXYGEN INTO THE SWIM-BLADDER OF FISH. 3. THE ROLE OF CARBON DIOXIDE

The secretion of carbon dioxide accompanying the secretion of oxygen into the swim-bladder of the bluefish is examined in order to distinguish among several theories which have been proposed to describe the operation of the rete mirabile, a vascular countercurrent exchange organ. Carbon dioxide may comprise 27 per cent of the gas secreted, corresponding to a partial pressure of 275 mm Hg. This is greater than the partial pressure that would be generated by acidifying arterial blood (about 55 mm Hg). The rate of secretion is very much greater than the probable rate of metabolic formation of carbon dioxide in the gas-secreting complex. It is approximately equivalent to the probable rate of glycolytic generation of lactic acid in the gas gland. It is concluded that carbon dioxide brought into the swim-bladder is liberated from blood by the addition of lactic acid. The rete mirabile must act to multiply the primary partial pressure of carbon dioxide produced by acidification of the blood. The function of the rete mirabile as a countercurrent multiplier has been proposed by Kuhn, W., Ramel, A., Kuhn, H. J., and Marti, E., Experientia, 1963, 19, 497. Our findings provide strong support for their theory. The unique structure of the gas-secreting complex of the swim-bladder of the bluefish, Pomatomus saltatrix L., is described.

The whistle and the rattle: the design of sound producing muscles

Vertebrate sound producing muscles often operate at frequencies exceeding 100 Hz, making them the fastest vertebrate muscles. Like other vertebrate muscle, these sonic muscles are "synchronous," necessitating that calcium be released and resequestered by the sarcoplasmic reticulum during each contraction cycle. Thus to operate at such high frequencies, vertebrate sonic muscles require extreme adaptations. We have found that to generate the "boatwhistle" mating call (approximately 200 Hz), the swimbladder muscle fibers of toadfish have evolved (i) a large and very fast calcium transient, (ii) a fast crossbridge detachment rate, and (iii) probably a fast kinetic off-rate of Ca2+ from troponin. The fibers of the shaker muscle of rattlesnakes have independently evolved similar traits, permitting tail rattling at approximately 90 Hz.

Effect of bentonite incorporated in a feed ration with tilmicosin in the prevention of induced Mycoplasma gallisepticum airsacculitis in broiler chickens

A factorial arrangement of tilmicosin and bentonite was evaluated for efficacy in broiler chickens infected with Mycoplasma gallisepticum and correlated to tilmicosin recovery in a feed assay method. Tilmicosin at 300-500 g/ton prevented development of airsacculitis. The addition of 2% bentonite to the ration caused tilmicosin at 300 g/ton to be ineffective in controlling air-sac lesions, whereas 400 and 500 g/ton were moderately effective. Six percent bentonite rendered tilmicosin completely ineffective at all dose levels. There was a direct correlation between the percentage of bentonite in the feed rations, the percentage of the tilmicosin recovered in the assay procedure, and the increased incidence of air-sac lesions.