Control of salt gland activity in the hatchling green sea turtle, Chelonia mydas

Symblepharon, Ankyloblepharon, and Salt Gland Dysfunction in a Loggerhead Sea Turtle (Caretta caretta)

Adhesions involving the bulbar and the palpebral conjunctiva (Symblepharon) may interfere with tear drainage, cause chronic conjunctivitis, and reduce ocular motility. This condition may be associated with adhesion of the edges of the upper and lower eyelids (ankyloblepharon). The present case describes bilateral symblepharon, ankyloblepharon and salt gland dysfunction in a juvenile Caretta caretta. The loggerhead presented both eyelids swollen, ulcerated, and not separable when rescued. Eye examination was not possible, but ultrasonography showed right bulbar integrity, while the left eye was smaller, with a thicker cornea that had lost its normal doubled lined structure. Surgical dissection of the fibrous adhesions between the palpebral and bulbar conjunctiva, cornea, and third eyelid was performed, and large dacryoliths were removed. The microscopic findings were consistent with chronic keratoconjunctivitis. Ultrastructurally, no virus-like particles were observed. In addition, tissue samples were negative for herpesvirus by qualitative PCR. The eyelids of both eyes and the corneal epithelium of the right eye healed; moreover, the vision was restored in the right eye. There were no recurrences after 12 months of follow-up, and the turtle was released 16 months after the end of treatments on the southern Tyrrhenian coast in the western Mediterranean Sea. To the authors’ knowledge, this is the first report of symblepharon with ankyloblepharon and salt gland dysfunction in Caretta caretta turtle. Ocular ultrasonography was helpful in the preliminary diagnostic work-up.

Osteological and vascular morphology and electrolyte homeostasis of sea turtles

Sea turtles have well developed lacrimal glands for their electrolyte homeostasis. In turtles, stapedial artery and palatine artery send branches to supply orbital region, but supply artery for lacrimal glands was not identified. Micro-CT scans showed dorsoventrally large lacrimal glands of sea turtle are supplied by both stapedial artery and palatine artery. The circulatory pattern in cranial region was reconstructed based on the micro-CT scans, showing that sea turtle has basically similar pattern with the common snapping turtle: stapedial artery supplies orbital region and mandibular artery is ramified from stapedial artery. We also investigate the foramen stapedio-temporalis in turtles using osteological specimens. The foramen stapedio-temporalis, where the stapedial artery passes through, has different size among four families of turtles. We compared the sum of cross sections of left and right foramen stapedio-temporalis since homeostasis of one individual is maintained by a pair of lacrimal glands. The size difference may reflect primarily the share of stapedial artery against palatine artery in cranial circulation pattern and blood supply of orbital regions. Our observations confirmed a significantly larger cross-section in the foramen stapedio-temporalis of sea turtles than other freshwater/terrestrial turtles. Since the circulatory pattern is shared, the size difference of foramen stapedio-temporalis reflects the amount of arterial blood supply to lacrimal glands. Therefore, the size of the foramen stapedio-temporalis may indicate marine adaptation of turtles and are applicable to both fossil and osteological specimens.

Occurrence of Fibropapillomatosis in Green Turtles (Chelonia mydas) in Relation to Environmental Changes in Coastal Ecosystems in Texas and Florida: A Retrospective Study

Fibropapillomatosis is a neoplastic disease of marine turtles, with green turtles (Chelonia mydas) being the most affected species. Fibropapillomatosis causes debilitating tumor growths on soft tissues and internal organs, often with lethal consequences. Disease incidence has been increasing in the last few decades and the reason is still uncertain. The potential viral infectious agent of Fibropapillomatosis, chelonid herpesvirus 5, has been co-evolving with its sea turtle host for millions of years and no major mutation linked with increased disease occurrence has been detected. Hence, frequent outbreaks in recent decades are likely attributable to external drivers such as large-scale anthropogenic changes in the green turtle coastal marine ecosystem. This study found that variations in sea surface temperature, salinity, and nutrient effluent discharge from nearby rivers were correlated with an increased incidence of the disease, substantiating that these may be among the significant environmental drivers impacting Fibropapillomatosis prevalence. This study offers data and insight on the need to establish a baseline of environmental factors which may drive Fibropapillomatosis and its clinical exacerbation. We highlight the multifactorial nature of this disease and support the inclusion of interdisciplinary work in future Fibropapillomatosis research efforts.

Review of petroleum toxicity in marine reptiles

Worldwide petroleum exploration and transportation continue to impact the health of the marine environment through both catastrophic and chronic spillage. Of the impacted fauna, marine reptiles are often overlooked. While marine reptiles are sensitive to xenobiotics, there is a paucity of petroleum toxicity data for these specialized fauna in peer reviewed literature. Here we review the known impacts of petroleum spillage to marine reptiles, specifically to marine turtles and iguanas with an emphasis on physiology and fitness related toxicological effects. Secondly, we recommend standardized toxicity testing on surrogate species to elucidate the mechanisms by which petroleum related mortalities occur in the field following catastrophic spillage and to better link physiological and fitness related endpoints. Finally, we propose that marine reptiles could serve as sentinel species for marine ecosystem monitoring in the case of petroleum spillage. Comprehensive petroleum toxicity data on marine reptiles is needed in order to serve as a foundation for future research with newer, unconventional crude oils of unknown toxicity such as diluted bitumen.

Physiological determinants of the internesting interval in sea turtles: a novel 'water-limitation' hypothesis

The internesting interval separates successive clutches of sea turtle eggs, and its duration varies both among and within species. Here, we review the potential physiological limits to this interval, and develop the hypothesis that desalination capacity limits the internesting interval owing to the requirement for water deposition in eggs. Sea turtles deposit 1-4 kg of water per clutch in egg albumen; for most species, this represents about 2% of adult body mass. We calculate how quickly turtles can recover this water by estimating maximal salt excretion rates, metabolic water production and urinary losses. From this water balance perspective, the 'water-limitation' hypothesis is plausible for green turtles but not for leatherbacks. Some plasma biochemistry studies indicate dehydration in sea turtles during the nesting season, although this is not a universal finding and these data have rarely been collected during the internesting interval itself. There is mixed support for a trade-off between clutch size and the length of the interval. We conclude that the 'water-limitation' hypothesis is plausible for most sea turtle species, but requires direct experimentation.

Effects of temperature and salinity on body fluid dynamics and metabolism in the estuarine diamondback terrapin (Malaclemys terrapin)

The diamondback terrapin is the only temperate turtle species that exclusively inhabits estuarine environments. Morphological, behavioral and physiological features contribute to the terrapin's ability to regulate body fluid osmotic pressure in a euryhaline environment. Low integument permeability combined with aquatic-terrestrial shuttling behavior limits passive exchange of water and salts with the environment, and terrapins regulate active uptake of salts via alterations in drinking and feeding behavior. The lachrymal salt gland facilitates excretion of excess sodium (Na⁺) and chloride (Cl^-) ions through active transport mechanisms. We investigated body fluid dynamics, oxygen consumption (V̇ _O2 ) and osmotic status of terrapins exposed to an acute increase in salinity (12 to 35 psu) at 10 and 25°C to gain insight into the relative importance of behavioral versus physiological osmoregulatory adjustments over a range of seasonally relevant temperatures. Linear mixed models were used to evaluate the effects of experimental temperature, salinity and mass. Overall, temperature effects were stronger than salinity effects. Terrapins acclimated to 25°C had significantly lower blood osmolality and Na⁺, and higher water turnover rates, daily water flux (DWF) and V̇ _O2  compared with terrapins acclimated to 10°C. Salinity effects were restricted to DWF, which significantly decreased in response to acute exposure to 35 psu. Our results support the notion that behavioral adjustments predominate in the osmoregulatory strategy of terrapins.

Perspectives on the convergent evolution of tetrapod salt glands

Since their discovery in 1958, the function of specialized salt-secreting glands in tetrapods has been studied in great detail, and such studies continue to contribute to a general understanding of transport mechanisms of epithelial water and ions. Interestingly, during that same time period, there have been only few attempts to understand the convergent evolution of this tissue, likely as a result of the paucity of taxonomic, embryological, and molecular data available. In this review, we synthesize the available data regarding the distribution of salt glands across extant and extinct tetrapod lineages and the anatomical position of the salt gland in each taxon. Further, we use these data to develop hypotheses about the various factors that have influenced the convergent evolution of salt glands across taxa with special focus on the variation in the anatomical position of the glands and on the molecular mechanisms that may have facilitated the development of a salt gland by co-option of a nonsalt-secreting ancestral gland. It is our hope that this review will stimulate renewed interest in the topic of the convergent evolution of salt glands and inspire future empirical studies aimed at evaluating the hypotheses we lay out herein.

Salt gland adenitis as only cause of stranding of loggerhead sea turtles Caretta caretta

The present study describes pathological and microbiological findings in 9 stranded loggerhead sea turtles Caretta caretta, whose only observed lesion was bilateral purulent salt gland adenitis. Histological lesions ranged from the presence of abundant eosinophilic material associated with bacterial colonies in the lumen of the central ducts of the glandular lobules to the destruction of the glandular tissue and presence of abundant eosinophilic material composed of heterophils and cell debris, lined by multinucleated giant cells. Aeromonas hydrophila, Staphylococcus sp., and Vibrio alginolyticus were the bacteria most frequently isolated. Plasma concentrations of sodium and chloride and plasma osmolality from 2 turtles suffering from salt gland adenitis were, respectively 45.7, 69.2, and 45.7% higher than the mean value for healthy turtles. These cases suggest that failure to maintain homeostasis due to severe lesions in the salt glands can cause stranding and/or death of loggerhead sea turtles.

Cholinergic and adrenergic innervation of lingual salt glands of the estuarine crocodile, Crocodylus porosus

Many marine reptiles and birds possess extrarenal salt glands that facilitate the excretion of excess sodium and chloride ions accumulated as a consequence of living in saline environments. Control of the secretory activity of avian salt glands is under neural control, but little information is available on the control of reptilian salt glands. Innervation of the lingual salt glands of the salt water crocodile, Crocodylus porosus, was examined in salt water-acclimated animals using histological methods. Extensive networks of both cholinergic and adrenergic nerve fibres were identified close to salt-secreting lobules and vasculature. The identification of both catecholamine-containing and cholinergic neurons in the salt gland epithelium and close to major blood vessels in the tissue suggests the action of the neurotransmitters on the salt-secreting epithelium itself and the rich vascular network of the lingual salt glands.

Salt and water regulation by the leatherback sea turtleDermochelys coriacea

We measured the salt and water balance of hatchling leatherback sea turtles, Dermochelys coriacea, during their first few days of life to investigate how they maintain homeostasis under the osmoregulatory challenge of a highly desiccating terrestrial environment and then a hyperosmotic marine environment. Hatchlings desiccated rapidly when denied access to sea water,with their hematocrit increasing significantly from 30.32±0.54 % to 38.51±1.35 % and plasma Na+ concentration increasing significantly from 138.2±3.3 to 166.2±11.2 mmoll-1 in 12 h. When hatchlings were subsequently put into sea water, hematocrit decreased and plasma Na+ concentration was unchanged but both were significantly elevated above pretreatment values. In other hatchlings kept in sea water for 48 h, body mass and plasma Na+ concentration increased significantly, but hematocrit did not increase. These data show that hatchlings were able to osmoregulate effectively and gain mass by drinking sea water. We stimulated hatchlings to secrete salt from the salt glands by injecting a salt load of 27 mmol kg-1. The time taken for secretion to begin in newly hatched turtles was longer than that in 4-day-old hatchlings, but the secretory response was identical at 4.15±0.40 and 4.13±0.59 mmol Na+ kg-1 h-1respectively. Adrenaline and methacholine were both potent inhibitors of salt gland secretion in a dose-dependent manner, although methacholine administered simultaneously with a subthreshold salt load elicited a transient secretory response. The results showed that hatchling leatherbacks are able to tolerate significant changes in internal composition and efficiently use their salt glands to establish internal ionic and water balance when in sea water.