Effect of metabolic rate on time-lags change in otolith microchemistry - An experimental approach using Salmo trutta

Over decades ecologists have long been interested in relevant techniques to track the field movement patterns of fish. Elemental composition of otolith represents a permanent record of the growing habitats experienced by the fish throughout its entire lifetime that is increasingly used in the literature. The lack of a predictive and mechanistic understanding of the individual kinematics underlying ion incorporation/depletion still limits our fine-scale temporal interpretation of the chemical signal recorded in the otolith. In particular, the rate at which elements are incorporated into otoliths is hypothesized to depend on fish physiology. However, to date, time-lags have mostly been quantified at a population scale. Here, we report results from controlled experiments (translocation and artificially enriched environment) on individual trace element incorporation/depletion rates in Salmo trutta (Salmonidae). We reported significant lags (i.e. weeks to months) between changes in water chemistry and subsequent change in otolith composition and highlighted substantial inter-individual variations in the timing and magnitude of Sr/Ca and Ba/Ca responses. These differences are partially linked to the energetic status (i.e. metabolic rate) of the individuals. It, therefore, appears that individuals with the highest metabolic rate are more likely to record detailed (i.e. brief) temporal changes than individuals having lower metabolic values. The time taken for environmental changes to be reflected in the growing otolith thus can no longer be assumed to remain a constant within populations. Results from the current study are a step towards fine reconstructing environmental histories in dynamic environments.

Human influence on brown trout juvenile body size during metapopulation expansion

Change in body size can be driven by social (density) and non-social (environmental and spatial variation) factors. In expanding metapopulations, spatial sorting by means of dispersal on the expansion front can further drive the evolution of body size. However, human intervention can dramatically affect these founder effects. Using long-term monitoring of the colonization of the remote Kerguelen islands by brown trout, a facultative anadromous salmonid, we analyse body size variation in 32 naturally founded and 10 human-introduced populations over 57 years. In naturally founded populations, we find that spatial sorting promotes slow positive changes in body size on the expansion front, then that body size decreases as populations get older and local density increases. This pattern is, however, completely different in human-introduced populations, where body size remains constant or even increases as populations get older. The present findings confirm that changes in body size can be affected by metapopulation expansion, but that human influence, even in very remote environments, can fully alter this process.

The biology and feeding ecology of Arctic charr in the Kerguelen Islands

Subsequent to their introduction in the 1950s, Arctic charr Salvelinus alpinus have been able to establish a self-sustaining population that has adapted to the unique conditions of the sub-Antarctic Kerguelen Islands. Here, 48 individuals (198-415 mm) were caught with gillnets and their basic biology and feeding ecology were examined using stable isotope analysis. The Lac des Fougères population split use of littoral and pelagic resources evenly, although larger fish relied more heavily on littoral production and appear to follow the size-dependent life history habitat template seen in many Scandinavian lakes where smaller sized individuals occupy the pelagic zone and larger individuals dominate the littoral habitat. In Kerguelen, Arctic charr mature at the same ages (5.6 years) as Arctic charr in both sub-Arctic and Arctic lakes. Although mortality was average in comparison to comparator sub-Arctic lakes, it was high in comparison to Arctic lakes. Maximal age (>7+) was at the lower end of the range typically seen in sub-Arctic lakes. Although they inhabit a resource-poor environment, Kerguelen Arctic charr showed no evidence of cannibalism. Thus, while Arctic charr can survive and reproduce in the relatively unproductive Kerguelen lake environments, survival and growth nevertheless appear to be traded off against survival and longevity. The uniqueness of the population location and the recency of its introduction suggest that further monitoring of the population has the potential to yield valuable insights into both the adaptability of the species and its likely responses to ongoing large-scale environmental change as represented by climate change.

Functional effect of vaterite - the presence of an alternative crystalline structure in otoliths alters escape kinematics of the brown trout

The fast-start escape response is the main locomotor behaviour observed in fish to evade predatory attacks and thereby increase their probability of survival. Thus far, this high-speed sensory motor control has been extensively studied in relation to extrinsic factors. In contrast, there has been surprisingly little consideration of intrinsic individual factors that can mediate sensorial perception, such as inter-individual variability in mechanosensory systems. The inner ear of teleost fishes is composed of otoliths that play an important role in hearing and balance functions. While sagittal otoliths are normally composed of aragonite in many fish species, the inclusion of vaterite (an abnormal crystalline structure) has been reported in a number of individuals from different environments. There is currently strong theoretical and empirical evidence that vaterite deposition has a negative impact on auditory sensitivity in fishes. While the functional/behavioural implications of this defect on otolith-related hearing function has been hypothesised, it has remained largely untested experimentally. Here, using juvenile (0+ years) Salmo trutta originating from the wild in experimental conditions, we report for the first time that the deposition of calcium carbonate in its crystalline vateritic polymorph has significant pervasive effects on the escape kinematics of fish. The presence of an alternative crystalline structure in otoliths is likely to alter fish behaviour in ways that decrease survival. We also report that altered behaviour in individuals with vateritic otoliths is partially compensated for by the presence of a functional lateral line. Such functional compensation suggests more slight consequences, if any, in the wild.

Invasion dynamics of a fish-free landscape by brown trout (Salmo trutta)

Metapopulation dynamics over the course of an invasion are usually difficult to grasp because they require large and reliable data collection, often unavailable. The invasion of the fish-free freshwater ecosystems of the remote sub-Antarctic Kerguelen Islands following man-made introductions of brown trout (Salmo trutta) in the 1950's is an exception to this rule. Benefiting from a full long term environmental research monitoring of the invasion, we built a Bayesian dynamic metapopulation model to analyze the invasion dynamics of 85 river systems over 51 years. The model accounted for patch size (river length and connections to lakes), alternative dispersal pathways between rivers, temporal trends in dynamics, and uncertainty in colonization date. The results show that the model correctly represents the observed pattern of invasion, especially if we assume a coastal dispersal pathway between patches. Landscape attributes such as patch size influenced the colonization function, but had no effect on propagule pressure. Independently from patch size and distance between patches, propagule pressure and colonization function were not constant through time. Propagule pressure increased over the course of colonization, whereas the colonization function decreased, conditional on propagule pressure. The resulting pattern of this antagonistic interplay is an initial rapid invasion phase followed by a strong decrease in the invasion rate. These temporal trends may be due to either adaptive processes or environmental gradients encountered along the colonization front. It was not possible to distinguish these two hypotheses. Because invasibility of Kerguelen Is. freshwater ecosystems is very high due to the lack of a pre-existing fish fauna and minimal human interference, our estimates of invasion dynamics represent a blueprint for the potential of brown trout invasiveness in pristine environments. Our conclusions shed light on the future of polar regions where, because of climate change, fish-free ecosystems become increasingly accessible to invasion by fish species.

An invasive fish and the time-lagged spread of its parasite across the Hawaiian archipelago

Efforts to limit the impact of invasive species are frustrated by the cryptogenic status of a large proportion of those species. Half a century ago, the state of Hawai'i introduced the Bluestripe Snapper, Lutjanus kasmira, to O'ahu for fisheries enhancement. Today, this species shares an intestinal nematode parasite, Spirocamallanus istiblenni, with native Hawaiian fishes, raising the possibility that the introduced fish carried a parasite that has since spread to naïve local hosts. Here, we employ a multidisciplinary approach, combining molecular, historical, and ecological data to confirm the alien status of S. istiblenni in Hawai'i. Using molecular sequence data we show that S. istiblenni from Hawai'i are genetically affiliated with source populations in French Polynesia, and not parasites at a geographically intermediate location in the Line Islands. S. istiblenni from Hawai'i are a genetic subset of the more diverse source populations, indicating a bottleneck at introduction. Ecological surveys indicate that the parasite has found suitable intermediate hosts in Hawai'i, which are required for the completion of its life cycle, and that the parasite is twice as prevalent in Hawaiian Bluestripe Snappers as in source populations. While the introduced snapper has spread across the entire 2600 km archipelago to Kure Atoll, the introduced parasite has spread only half that distance. However, the parasite faces no apparent impediments to invading the entire archipelago, with unknown implications for naïve indigenous Hawaiian fishes and the protected Papahānaumokuākea Marine National Monument.

Putting in shape: towards a unified approach for the taxonomic description of monogenean haptoral hard parts

Among monogeneans, haptoral hard parts provide prominent morphological characters upon which identifications are largely based. Traditionally, morphometric approaches are based on the use of arbitrary collections of linear distance measurements between landmarks. An exhaustive review of the specific diagnoses published in the journal Systematic Parasitology highlights the fact that an intricately important number of measurements are used to describe the same morphological features. Hence, this does not allow relevant comparison between studies and may have caused confusion in the literature. More importantly, a significant proportion of diagnoses commonly used do not maximize the amount of information available from morphological features, and sets of linear measurements between landmarks do not properly allow the complete reconstruction of the shape of haptoral hard parts. Given this prominent bias and the disparate use of traditional methodologies, I suggest the use of alternative methods in systematic parasitology that fully take into consideration the shape of morphological features. In addition to these considerations, a move toward placing shape at the centre of automated species recognition would be mutually beneficial for both taxonomists and non-taxonomists.

Characterization of the Different Dextransucrase Activities Excreted in Glucose, Fructose, or Sucrose Medium by Leuconostoc mesenteroides NRRL B-1299

When grown in glucose or fructose medium in the absence of sucrose, Leuconostoc mesenteroides NRRL B-1299 produces two distinct extracellular dextransucrases named glucose glucosyltransferase (GGT) and fructose glucosyltransferase (FGT). The production level of GGT and FGT is 10 to 20 times lower than that of the extracellular dextransucrase sucrose glucosyltransferase (SGT) produced on sucrose medium (traditional culture conditions). GGT and FGT were concentrated by ultrafiltration before sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Their molecular masses were 183 and 186 kDa, respectively, differing from the 195 kDa of SGT. The structural analysis of the dextran produced from sucrose and of the oligosaccharides synthesized by acceptor reaction in the presence of maltose showed that GGT and FGT are two different enzymes not previously described for this strain. The polymer synthesized by GGT contains 30% alpha(1-->2) linkages, while FGT catalyzes the synthesis of a linear dextran only composed of alpha(1-->6) linkages.

Multiple parasite introduction and host management plan: case study of lutjanid fish in the Hawaiian Archipelago

The bluestriped snapper Lutjanus kasmira and the blacktail snapper L. fulvus were deliberately introduced in the Hawaiian Archipelago from French Polynesia in the late 1950s to enhance local fisheries. These species rapidly spread all over the Windward Islands, became extremely abundant and, therefore, caused controversial environmental concerns. A comparison of the whole metazoan parasite community of L. kasmira and L. fulvus was performed between their native ranges in French Polynesia (Moorea Island in the Society Archipelago and Ua Huka in the Marquesas Islands) and their introduced range in O'ahu, Hawaii, USA. We suggest that 8 monogenean species have been introduced with L. kasmira and L. fulvus into the Hawaiian Archipelago from French Polynesia; 2 other species as well as one nematode should be referred to as cryptogenic. Moreover, experimental mortality conducted on monogeneans found in Polynesia emphasizes the inefficiency of anti-parasite treatment which was performed 50 yr ago, explaining possible parasite introduction. Finally, we discuss the potential threat of exotic parasites to the native fish community in the Hawaiian Archipelago and conclude that the absence of co-evolved hosts prevents parasite transfer from non-indigenous to native fishes as monogeneans are highly specific.

Monogeneans of the grouper Epinephelus tauvina (Perciformes, Serranidae) off Moorea, French Polynesia, with a description of Pseudorhabdosynochus pai n. sp. (Monogenea: Diplectanidae)

Specimens of the greasy grouper Epinephelus tauvina (Forsskål), caught off Moorea, French Polynesia, harboured four species of gill monogeneans. The diplectanid Pseudorhabdosynochus pai n. sp. is characterised by an extremely big male quadriloculate organ (inner length 77 mum, cone length 15, tube length 47), the largest of all members of the genus, and a sclerotised vagina with a very complex structure, including three secondary chambers instead of one as in most species. Pseudorhabdosynochus sp. is a species of the 'cupatus group'; this species is not formally described but various measurements are provided. The ancyrocephalid Haliotrema sp. and the capsalid Benedenia sp. were rare; they are both mentioned but not described. The diplectanid fauna of E. tauvina corresponds to the pattern already found in a clade of grouper species, the members of which often harbour both a species of the 'cupatus group' and another species of Pseudorhabdosynochus Yamaguti, 1958.

Measurement of the radiological hip joint space width. An evaluation of various methods of measurement

OBJECTIVE

To determine the most relevant method of measurement of the radiographic hip joint space width (JSW).

DESIGN

Seventy hips were examined from 36 patients of the ECHODIAH study having had one to four X-rays of the pelvis during the 3-year course of the study. Minimum interbone distance (MIDc), mean width of both the whole joint space (MJSWL) and a region of interest of the joint space (MJSWroi) were measured using computerized analysis of digitized radiographs. MID was also measured using a graduated eyepiece (MIDge). Reproducibility of the measurement was assessed by the intraclass coefficient of correlation. Sensitivity to change was evaluated by the standardized response mean.

RESULTS

The intraobserver intraclass coefficient of correlation of MIDc and MJSWroi was 0.98 and 0.94, respectively. The mean value degrees S.D. of MJSWL, MJSWroi, MIDc and MIDge was 3.3 degrees 0.9, 2.6 degrees 0.9, 2.4 degrees 0.9 and 2.6 degrees 1.2 mm, respectively. MIDge was significantly larger than MIDc (mean difference: 0.21 degrees 0.62 mm, P<0.001), in both normal and osteoarthritic hips. However, the difference between MIDge and MIDc varied largely when considering topography of femoral head migration. Whatever the method was, a significant (P<0.001) mean decrease of nearly 0.5 mm was found in osteoarthritic hips over the 3 year follow-up. The standardized response mean for MJSWL, MJSWroi, MIDge and MIDc was 0.73, 0.75, 0.79 and 0.85, respectively. Superiority of MIDc, in term of sensitivity to change, was mainly seen in osteoarthritic hips showing a superomedial or a concentric migration of the femoral head.

CONCLUSION

Minimum interbone distance measured with a computer assisted method is suggested as the most suitable method for the evaluation of hip osteoarthritis (OA) progression.

Involvement of Gln937 of Streptococcus downei GTF-I glucansucrase in transition-state stabilization

Multiple alignment of deduced amino-acid sequences of glucansucrases (glucosyltransferases and dextransucrases) from oral streptococci and Leuconostoc mesenteroides has shown them to share a well-conserved catalytic domain. A portion of this domain displays homology to members of the alpha-amylase family (glycoside hydrolase family 13), which all have a (beta/alpha)8 barrel structure. In the glucansucrases, however, the alpha-helix and beta-strand elements are circularly permuted with respect to the order in family 13. Previous work has shown that amino-acid residues contributing to the active site of glucansucrases are situated in structural elements that align with those of family 13. In alpha-amylase and cyclodextrin glucanotransferase, a histidine residue has been identified that acts to stabilize the transition state, and a histidine is conserved at the corresponding position in all other members of family 13. In all the glucansucrases, however, the aligned position is occupied by glutamine. Mutants of glucosyltransferase I were constructed in which this glutamine, Gln937, was changed to histidine, glutamic acid, aspartic acid, asparagine or alanine. The effects on specific activity, ability to form glucan and ability to transfer glucose to a maltose acceptor were examined. Only histidine could substitute for glutamine and maintain Michaelis-Menten kinetics, albeit at a greatly reduced kcat, showing that Gln937 plays a functionally equivalent role to the histidine in family 13. This provides additional evidence in support of the proposed alignment of the (beta/alpha)8 barrel structures. Mutation at position 937 altered the acceptor reaction with maltose, and resulted in the synthesis of novel gluco-oligosaccharides in which alpha1,3-linked glucosyl units are joined sequentially to maltose.

Mutagenesis of asp-569 of glucosyltransferase I glucansucrase modulates glucan and oligosaccharide synthesis

Glucansucrases of oral streptococci and Leuconostoc mesenteroides are enzymes of medical and biotechnological interest that synthesize alpha-glucans. They can also synthesize oligosaccharides in the presence of a sugar acceptor. Previous reports have identified an amino acid residue that may affect the structure of the glucan product; therefore, random mutagenesis of the corresponding Asp-569 of Streptococcus downei glucosyltransferase I (GTF-I) was used to further understanding of its involvement in the catalytic mechanism and to evaluate how different amino acids can modulate glucan and oligosaccharide synthesis. GTF-I variants were obtained where Asp-569 was replaced by each of the different possible classes of amino acids. These were expressed in Escherichia coli and purified by means of a His(6) tag. The results showed that the amino acid in position 569 influences the structure of the glucan and the size of the oligosaccharides produced by GTF-I. The results suggest that the amino acid occupying this position is more likely to interact with the acceptor molecules (oligosaccharides or elongating glucan chain) than to be directly involved in glucosyl transfer from sucrose. Engineering of the equivalent position in glucansucrases thus appears to be a good target to expand the range of oligosaccharides synthesized.

Isolation of key amino acid residues at the N-terminal end of the core region Streptococcus downei glucansucrase, GTF-I

Related streptococcal and Leuconostoc mesenteroides glucansucrases are enzymes of medical and biotechnological interest. Molecular modelling has suggested that the catalytic domain contains a circularly permuted version of the (beta/alpha)8 barrel structure found in the amylase superfamily, and site-directed mutagenesis has identified critical amino acids in this region. In this study, sequential N-terminal truncations of Streptococcus downei GTF-I showed that key amino acids are also present in the first one-third of the core domain. Mutations were introduced at Trp-344, Glu-349 and His-355, residues that are conserved in all glucansucrases and lie within a region which is a target for inhibitory antibodies. W344L, E349L and H355V substitutions were assayed for their effect on mutan synthesis and also on oligosaccharide synthesis with various acceptors. It appeared that Trp-344 and His-355 are involved in the action mechanism of GTF-I; His-355 may also play a role in a binding subsite necessary for oligosaccharide and glucan elongation.

[Occupational asthma: retrospective study of a series of 144 cases]

The occupational origin of asthma is only found only late, from a diagnosis delay due to development. The aim of this work was to study the chronological characteristics of occupational asthma of different etiologies and to understand the occupational after-effects. A series of 144 cases were analysed (115 men and 29 women) who were seen in a consultation that specialised in occupational pathology, with the inclusion criteria those of the National Institute for Occupational Safety and Health (NIOSH). The analysis was based on: the causative allergen or work protocol; the role of atopy; length of the latency phase; length of symptom exposure; diagnosis delay; occupational consequences. Asthma from isocyanates and flour between them accounted for 62% in this series. These were followed by asthma from wood (8.3%) and persulphates (7.6%). The mean length of the latency period was 7.5 years and the mean diagnosis delay was 2.5 years. Clinical history of atopy and the existence of rhinitis were much more common for the "biological" than the "chemical" asthmas (respectively 69% and 95%, against 36% and 15%). Amongst the 64% of patients who benefited from complete removal of the allergen, 78.5% who were cured or improved, though for those who kept the same conditions of work there was a persistence or even aggravation of symptoms. In 74 cases a certificate of occupational illness was given to the patient.

New surgical obturator prosthesis for hemimaxillectomy patients

Many materials have been used to make immediate and intermediate obturator prostheses for the hemimaxillectomy patient. The weight of the obturator prosthesis is a major hindrance. A new thermoplastic material, Polysar, is described to create a hollow obturator extension for immediate and intermediate lightweight obturator prostheses.

Streptococcus suis meningitis. A severe noncompensated occupational disease

Meningitis caused by Streptococcus suis type 2, a rare disease first recognized in 1968 (108 cases worldwide in 1989), is contracted by occupational exposure to pigs and often results in very severe disabilities (definitive deafness and ataxia in 50% of cases). We report the case of an employee in a rendering plant whose initial symptom was deafness. A detailed analysis of medical and veterinary literature is provided concerning the epidemiology of the disease, the clinical forms in man, bacteriological diagnosis and the role of the pig as healthy carrier. It is recommended that this occupational disease be officially recognized for compensation in France.

Purification and properties of an endo-1,4-xylanase excreted by a hydrolytic thermophilic anaerobe, Clostridium thermolacticum. A proposal for its action mechanism on larchwood 4-O-methylglucuronoxylan

An extracellular xylanase from a thermophilic anaerobe, Clostridium thermolacticum, was purified 400-fold by ion-exchange chromatography and gel filtration. The purified enzyme had a specific activity of 31,670 nkat/mg of protein at 60 degrees C, a molecular mass of 39 kDa and a pI of 4.9. The enzyme exhibited maximal activity at 80 degrees C (1 h assay) and at pH 6.0-6.5. There was little loss of activity after 4 days at 60 degrees C and the enzyme was stable in the wide pH range 3-11. Examination of the hydrolysis products of larchwood xylan indicated that it was an endoxylanase; at the early stage of the reaction, xylose (Xyl)-containing oligosaccharides of 3-12 residues were released and after a prolonged incubation time, the neutral end-products were Xyl2 and Xyl3. Kinetic studies of the hydrolysis of xylose-containing oligosaccharides of 4-7 residues showed that the tetrasaccharide was hydrolysed more slowly than the pentasaccharide, while the calculated Km and V values for pentasaccharide and hexasaccharide were similar. The primary structures of the XylnGlcA produced by long-term hydrolysis of larchwood glucuronoxylan were determined on the basis of their carbohydrate composition, by methylation analysis and by 1H-NMR and 13C-NMR spectroscopies. These data allowed us to propose a model for the mode of action of this endoxylanase on larchwood 4-O-methylglucuronoxylan.

Proof of the occurrence of 5,6-O-(1-carboxyethylidene)-D-galactofuranose units in the capsular polysaccharide of Klebsiella K12

The 13C-n.m.r. spectra of the capsular polysaccharide of Klebsiella K41 and phage-derived oligosaccharides K41-P1 and K41-P2 were compared with spectra from the structurally similar polysaccharide of Klebsiella K12 and oligosaccharides K12-P1 and K12-P2. This led to the conclusion that K41 and K12 contain one and two galactofuranose residues per repeating unit, respectively, and that the terminal, lateral residue in K12 has the 5,6-O-(1-carboxyethylidene)-D-galactofuranose structure rather than that of a 4,6-acetal of D-galactopyranose as originally stated. This is the first reported occurrence in Nature of such a structural unit.

Structural investigation of the capsular polysaccharide from Klebsiella K19 by chemical and N.M.R. analyses

Sugar analysis of the capsular antigen K19 from Klebsiella and of the carboxyl-reduced derivative confirmed its classification into the chemotype containing rhamnose, galactose, glucose, and glucuronic acid residues. Partial acid hydrolysis and phage depolymerization of K19 provided respectively a modified, linear form of the polysaccharide and oligosaccharides of the repeating unit, these were used for the structural elucidation of the original polymer. Methylation analysis, Smith degradation, and 1H- and 13C-n.m.r. spectroscopy of the polysaccharide and derivatives permitted formulation of the following structure for K19: (formula; see text)