Hook-shaped enterolith and secondary cachexia in a free-living grey nurse shark (Carcharias taurus, Rafinesque 1810).

The carcass of a critically endangered, juvenile female grey nurse shark (Carcharias taurus, Rafinesque 1810) was recovered from a south-eastern Australian beach and subjected to necropsy. The 1.98-m-long shark exhibited advanced cachexia with its total weight (19.0 kg) and liver weight (0.37 kg) reduced by 60% and 89%, respectively, compared with a healthy individual of the same length. Marked tissue decomposition was evident preventing histopathology and identification of a definitive cause of death. At necropsy, the abdominal organs were abnormally displaced and showed marked reductions in size compared with a healthy individual of the same size. Importantly, a hook-shaped enterolith (HSE), with a rough surface and cream in colour, was found within the spiral valve of the intestine and is to the authors' knowledge, the first description of such in any marine animal. X-ray diffractometry showed that the HSE comprised the minerals monohydrocalcite (Ca[CO3].H2O; ~70 wt%) and struvite (Mg [NH4 ] [PO4 ]. [H2 O]6 ; ~30 wt%). A CT scan showed concentric lamellate concretions around a 7/o offset J-hook that formed the nidus of the HSE. Nylon fishing line attached to the hook exited the HSE and was evident in the abdominal cavity through a perforation in the intestinal wall where the posterior intestinal artery merges. The most parsimonious reconstruction of events leading to enterolithiasis and secondary cachexia in this shark was the consumption of a hooked fish and subsequent hook migration causing perforations of the cardiac stomach wall followed by the thin, muscular wall of the apposed, sub-adjacent intestine.

Structural changes to the uterus of the dwarf ornate wobbegong shark (Orectolobus ornatus) during pregnancy.

Embryos of the viviparous dwarf ornate wobbegong shark (Orectolobus ornatus) develop without a placenta, unattached to the uterine wall of their mother. Here, we present the first light microscopy study of the uterus of O. ornatus throughout pregnancy. At the beginning of pregnancy, the uterine luminal epithelium and underlying connective tissue become folded to form uterine ridges. By mid to late pregnancy, the luminal surface is extensively folded and long luminal uterine villi are abundant. Compared to the nonpregnant uterus, uterine vasculature is increased during pregnancy. Additionally, as pregnancy progresses the uterine epithelium is attenuated so that there is minimal uterine tissue separating large maternal blood vessels from the fluid that surrounds developing embryos. We conclude that the uterus of O. ornatus undergoes an extensive morphological transformation during pregnancy. These uterine modifications likely support developing embryos via embryonic respiratory gas exchange, waste removal, water balance, and mineral transfer.

Capture-induced exertional rhabdomyolysis in the Shortfin Mako Shark, Isurus oxyrinchus.

BACKGROUND: Shortfin Mako sharks (Isurus oxyrinchus) are top-order predators in oceanic food chains. They are captured worldwide by commercial and recreational fisheries, but little is known about the effects that fishing has on the homeostasis and longevity of these animals. OBJECTIVE: This study aimed to assess the health of Shortfin Mako sharks captured by recreational fishers off eastern Australia. METHODS: Twenty-four sharks were captured, and their gender, length, weight, reproductive maturity, and stage were recorded. After blood and urine collection, serum analytes were quantified using standard biochemical methods, whereas urine was analyzed using semi-quantitative reagent strips, microscopic examination, centrifugation, and ammonium sulfate precipitation tests. RESULTS: Six Makos presented with red-brown urine. The means of notable serum analytes were as follows: sodium 276 mmol/L, potassium 15.6 mmol/L, inorganic phosphate 10.6 mmol/L, magnesium 3.3 mmol/L, urea 325 mmol/L, creatinine 52 µmol/L, AST 2806 U/L, CK 240938 U/L, lactate 44.4 mmol/L, osmolarity 1160 mmol/L, and pH 7.13. These analytes differed from the respective sand tiger shark reference interval, which was used as a proxy for Makos. The red-brown urine was due to myoglobin and had a mean pH of 5.76 that, when combined with red-brown casts, led to a diagnosis of fishing-induced exertional rhabdomyolysis that occurred secondary to lactic acidosis, hypoxia, and hypovolemia. It was further exacerbated by hyperkalemia and acute renal failure, serious complications that often lead to mortality. CONCLUSIONS: Practitioners caring for sharks and rays should consider collecting urine from free-living or aquarium animals when they are captured for examination and/or treatment, particularly at times with maximal seawater temperatures.

Captive parturition and neonatal growth of the dwarf ornate wobbegong (Orectolobus ornatus de Vis, 1883).

Neonatal predation in multispecies aquarium exhibits can prevent detection of captive breeding by wobbegong sharks. We used ultrasonography and isolation strategies to prevent neonatal predation and maximize survival/growth of the dwarf ornate wobbegong (Orectolobus ornatus de Vis, 1883). We captured seven free-living wobbegongs (two males and five females) and subjected each animal to a health assessment which led to the euthanasia of one female with a retained hook. Ultrasonography showed that females were pregnant, one was preovulatory, and one was in a resting phase. Two females (one pregnant) and one male were placed in isolation in each of two tanks. In October 2006, 25 neonates were born overnight with the two litters placed into separate neonate tanks. Over the ∼6.5-month monitoring period, four neonates with reduced body condition died without premonitory signs resulting in a 63.0% annual survival rate. Finite growth rates did not differ between sexes or litters and averaged (±SE) 12.2 (1.5) cm/year and 156.4 (26.4) g/year. At the cessation of monitoring, total length had increased by ∼30%, whereas total weight had almost doubled with neonatal body condition in line with free-living wobbegongs. Our efficacious, six-step manipulative, the approach should be applicable with all wobbegongs given their reproductive similarities, but we recommend that efforts focus on the dwarf ornate, tasselled and Japanese wobbegongs because all are small in size and have bred in aquaria. Ultimately, this approach should produce self-sustaining aquarium populations, place less reliance on the wild acquisition and provide animals for other aquaria, population restocking, or scientific research.

Population structure and connectivity of tiger sharks (Galeocerdo cuvier) across the Indo-Pacific Ocean basin.

Population genetic structure using nine polymorphic nuclear microsatellite loci was assessed for the tiger shark (Galeocerdo cuvier) at seven locations across the Indo-Pacific, and one location in the southern Atlantic. Genetic analyses revealed considerable genetic structuring (FST > 0.14, p < 0.001) between all Indo-Pacific locations and Brazil. By contrast, no significant genetic differences were observed between locations from within the Pacific or Indian Oceans, identifying an apparent large, single Indo-Pacific population. A lack of differentiation between tiger sharks sampled in Hawaii and other Indo-Pacific locations identified herein is in contrast to an earlier global tiger shark nDNA study. The results of our power analysis provide evidence to suggest that the larger sample sizes used here negated any weak population subdivision observed previously. These results further highlight the need for cross-jurisdictional efforts to manage the sustainable exploitation of large migratory sharks like G. cuvier.

Serum biochemical reference intervals for free-living Sand Tiger sharks (Carcharias taurus) from east Australian waters.

BACKGROUND: Sharks are top-order predators in ocean food chains and the star attractions in aquaria worldwide. Unfortunately, blood biochemistry reference intervals (RI) have been determined for few species. OBJECTIVE: The study aims to establish serum biochemical RI for free-living Sand Tiger sharks (Carcharias taurus) off eastern Australia. METHODS: Thirty-seven sharks were captured and their sex, length, weight, reproductive maturity, and health status were recorded. After blood collection, serum analytes were quantified using standard analytical and statistical methods. Reference intervals, means, medians, and 90% confidence intervals were generated. Physiologic data from live and necropsied sharks were used to enhance the study results. RESULTS: Thirty healthy sharks were included in the study. Albumin could not be detected. With the exception of ALP activity, values were unaffected by sex, length, weight, age, and life-history stage. The means (RI) were: sodium 258 (249-267) mmol/L, potassium 5.0 (4.3-5.7) mmol/L, chloride 242 (227-257) mmol/L, inorganic phosphate 1.8 (1.7-2.0) mmol/L, total calcium 3.9 (3.3-4.4) mmol/L, magnesium 1.9 (1.6-2.2) mmol/L, glucose 2.7 (2.2-3.2) mmol/L, urea 377 (360-394) mmol/L, ALP 20 (8-31) U/L, ALT 3 U/L (no RI), AST 29 (13-45) U/L, CK 42 (5-79) U/L, total protein 30 (24-36) g/L, triglyceride 0.3 (0.1-0.6) mmol/L, cholesterol 1.4 (0.9-2.1) mmol/L, creatinine 32 µmol/L (no RI), total bilirubin 1.5 µmol/L (no RI), and osmolarity 1082 (1027-1136) mmol/L. CONCLUSIONS: These preliminary RI will assist with the clinical evaluation and treatment of captive and free-living Sand Tiger sharks worldwide. Studies with more animals will increase the precision of upper and lower reference limits.

Natural or artificial? Habitat-use by the bull shark, Carcharhinus leucas.

BACKGROUND: Despite accelerated global population declines due to targeted and illegal fishing pressure for many top-level shark species, the impacts of coastal habitat modification have been largely overlooked. We present the first direct comparison of the use of natural versus artificial habitats for the bull shark, Carcharhinus leucas, an IUCN 'Near-threatened' species--one of the few truly euryhaline sharks that utilises natural rivers and estuaries as nursery grounds before migrating offshore as adults. Understanding the value of alternate artificial coastal habitats to the lifecycle of the bull shark is crucial for determining the impact of coastal development on this threatened but potentially dangerous species. METHODOLOGY/FINDINGS: We used longline surveys and long-term passive acoustic tracking of neonate and juvenile bull sharks to determine the ontogenetic value of natural and artificial habitats to bull sharks associated with the Nerang River and adjoining canals on the Gold Coast, Australia. Long-term movements of tagged sharks suggested a preference for the natural river over artificial habitat (canals). Neonates and juveniles spent the majority of their time in the upper tidal reaches of the Nerang River and undertook excursions into adjoining canals. Larger bull sharks ranged further and frequented the canals closer to the river mouth. CONCLUSIONS/SIGNIFICANCE: Our work suggests with increased destruction of natural habitats, artificial coastal habitat may become increasingly important to large juvenile bull sharks with associated risk of attack on humans. In this system, neonate and juvenile bull sharks utilised the natural and artificial habitats, but the latter was not the preferred habitat of neonates. The upper reaches of tidal rivers, often under significant modification pressure, serve as nursery sites for neonates. Analogous studies are needed in similar systems elsewhere to assess the spatial and temporal generality of this research.

Serum biochemical reference intervals for wild dwarf ornate wobbegong sharks (Orectolobus ornatus).

BACKGROUND: Sharks are important to sport and commercial fishing, public aquaria, and research institutions. However, serum biochemical reference values have been established for few species. OBJECTIVE: The aim of this study was to establish serum biochemical reference intervals for wild-caught dwarf ornate wobbegong sharks (Orectolobus ornatus). METHODS: Fifty wobbegongs were caught, and their health status, sex, length, and weight were evaluated and recorded. Following collection of blood, serum biochemical analytes were measured and analyzed using standard analytical and statistical methods. Combined samples generated means, medians, and reference intervals. RESULTS: For the measured analytes, means (reference intervals) were as follows: sodium 287 (284-289) mmol/L, chloride 277 (274-280) mmol/L, potassium 5.2 (5.0-5.3) mmol/L, total calcium 4.6 (4.5-4.7) mmol/L, magnesium 1.9 (1.7-2.0) mmol/L, inorganic phosphate 1.8 (1.7-1.9) mmol/L, glucose 2.6 (2.4-2.8) mmol/L, total protein 46 (45-47) g/L, urea 396 (392-401) mmol/L, creatinine ≤ 0.02 mmol/L, total bilirubin 2.0 (1.9-2.1) µmol/L, cholesterol 1.3 (1.2-1.4) mmol/L, triglyceride 0.5 (0.4-0.6) mmol/L, alkaline phosphatase 24 (21-28) U/L, alanine aminotransferase 3 U/L, aspartate aminotransferase 28 (25-31) U/L, creatine kinase 49 (38-59) U/L, and osmolarity 1104 (1094-1114) mmol/L. Serum values were not affected by sex, length, or weight. CONCLUSIONS: Established reference values will assist with clinical evaluation and treatment of dwarf ornate wobbegongs in aquaria, research institutions, and the wild.

Embryonic Growth and Maternal-embryo Nutritional Relationship of Wobbegong Sharks (genus Orectolobus).

This article was retracted. See the Notification.