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PubMed2004

Immunoglobulins in the eggs of the nurse shark, Ginglymostoma cirratum.

Elasmobranchs, which include the sharks, skates, and rays, emerged over 450 million years ago and are the oldest vertebrates to possess an adaptive immune system. They have evolved diverse reproductive modes, with a variety of physiological adaptations that enhance reproductive success. The nurse shark, Ginglymostoma cirratum, is an aplacental, viviparous elasmobranch in which the egg and its associated vitelline vasculature are the primary route for maternal-embryonic interactions. During gestation, nurse shark embryos hatch from their eggcases and develop free in the uterus, which is flushed regularly with seawater. Similar to higher vertebrates, embryonic and neonatal nurse sharks possess an immune system that is not fully competent. In birds and bony fishes, maternal immunoglobulins (Ig) stored in the egg during oogenesis confer protective immunity to embryos during gestation. However, early research suggested that such transfer of passive immunity does not occur in sharks. To better understand how elasmobranch embryos are protected from waterborne pathogens during this potentially vulnerable time, we have re-examined the existence of Igs in elasmobranch eggs. Using monoclonal antibodies, we establish the presence of two classes of Igs in nurse shark eggs: 7S IgM and IgNAR. The potential transfer of immunoglobulins from elasmobranch eggs is discussed.

Animals↗
PubMedDate not supplied

c-Reactive protein levels as a biomarker of inflammation and stress in the Atlantic sharpnose shark (Rhizoprionodon terraenovae) from three southeastern USA estuaries.

Circulating c-reactive protein (CRP) levels can be used as a bioindicator of the acute phase inflammatory response and as a possible biomarker of inflammation and neurogenic stress in vertebrates. Currently, there are no data describing the ranges of CRP levels in sharks living in different habitats, especially habitats of differing degrees of pollution. Developing antibodies against CRP is a first and critical step towards developing sensitive methods for quantifying CRP, and thus inflammatory and stress responses in sharks. Sharpnose shark, Rhizoprionodon terraenovae, serum C-reactive protein was purified sequentially over AH-sepharose 4B-PC and sepharose CL-4B columns and used to immunize balb/c mice for generating stocks of polyclonal anti-sera. Serum samples from 131 sharpnose sharks were collected from three different geographical regions along the coast of SC and GA, USA between June and November 2002. Total CRP concentrations were quantified by ELISA and found to be highest in the sharpnose shark population collected in the summer from Charleston, SC, compared to Beaufort, SC and Brunswick, GA. Seasonal comparisons indicated a higher CRP concentration in the summer of the Charleston, SC population compared to the fall. These data suggest that sharks living in the Charleston, SC harbor estuary may be exposed to a suite of pathogens or other stressors that are different than those found in the Beaufort, SC and Brunswick, GA estuaries. These data support the use of CRP as a bioindicator of health status in elasmobranchs.

Acute-Phase Reaction↗
PubMed2006

Absence of neurotoxic effects in leopard sharks, Triakis semifasciata, following domoic acid exposure.

Domoic acid (DA), a potent neurotoxin produced by select species of algae and diatoms, kills neurons bearing kainic acid-type glutamate receptors. Studies have shown that DA bioaccumulates in invertebrates and fish that consume the diatoms. In every vertebrate species tested or observed in the wild, dietary or systemic DA causes neuronal damage or clinical signs of neurotoxicity. Sharks, like marine birds and mammals, are exposed to DA through their diet; however, no research has demonstrated the effect of DA on shark behavior or physiology. In this study, juvenile leopard sharks (Triakis semifasciata) were given DA by intracoelomic injection at doses of 0, 1, 3, 9, and 27 mg/kg and observed for 7 days. The sharks failed to demonstrate behavioral or histological changes in response to the toxin. We identified putative brain glutamate receptors by probing western blots with an antibody specific for kainic acid-type glutamate receptors and demonstrated receptor localization in the cerebellum with immunohistochemistry. Blood levels of DA in three sharks dosed at 9 mg/kg fell rapidly within 1.5h of injection. We show that leopard sharks possess the molecular target for DA but are resistant to doses of DA known to be toxic to other vertebrates.

Animals↗
PubMed2001

The anatomy of a shark attack: a case report and review of the literature.

Shark attacks are rare but are associated with a high morbidity and significant mortality. We report the case of a patient's survival from a shark attack and their subsequent emergency medical and surgical management. Using data from the International Shark Attack File, we review the worldwide distribution and incidence of shark attack. A review of the world literature examines the features which make shark attacks unique pathological processes. We offer suggestions for strategies of management of shark attack, and techniques for avoiding adverse outcomes in human encounters with these endangered creatures.

Adult↗
PubMed2002

The role of adenosine in the anoxic survival of the epaulette shark, Hemiscyllium ocellatum.

The epaulette shark (Hemiscyllium ocellatum) is among the few vertebrates that can tolerate extreme hypoxia for prolonged periods and, as shown here, anoxia. We examined how anoxia affected this shark's level of responsiveness, concentration of brain ATP and adenosine -- an endogenous neuronal depressant. In addition, we investigated how these variables were affected by aminophylline, an adenosine receptor antagonist. Epaulette sharks placed in an anoxic environment (<0.02 mg O2 l(-1)) lost their righting reflex after 46.3 +/- 2.8 min, but immediately regained vigilance upon return to normoxia. Then 24 h later, the same sharks were injected with either saline or aminophylline (30 mg kg(-1)) in saline and re-exposed to anoxia. In this second anoxic episode, controls sharks showed a 56% decrease in the time taken to lose their righting reflex but maintained their brain ATP levels; conversely, aminophylline-treated epaulette sharks displayed a 46% increase in the time to loss of righting reflex and had significantly lower brain ATP levels. Since anoxia also caused a 3.5-fold increase in brain adenosine levels, these results suggest that adenosine receptor activation had a pre-emptive role in maintaining brain ATP levels during anoxia. Perhaps because adenosine receptor activation initiates metabolic depression, indicated by the early loss of responsiveness (righting reflex), such a mechanism would serve to reduce ATP consumption and maintain brain ATP levels.

Adenosine↗
PubMed2000

Physical properties of shark gelatin compared with pig gelatin.

Physical properties of shark gelatin were examined during gel formation and postgelation in comparison with pig gelatin. Samples with various concentrations and pH values were evaluated by breaking strength, dynamic viscoelasticity, and dynamic light scattering. Sol-gel and gel-sol transition temperatures for shark gelatin were remarkably lower than those for pig gelatin. Shark gelatin gel shows a narrower pH range to form a stable gel compared with pig gelatin. Melting enthalpy of shark gelatin gel was greater than that of pig gelatin gel, and G' of shark gelatin gel changed more extensively with rising temperature in comparison with pig gelatin gel. It is concluded that shark gelatin has different characteristics from pig gelatin not only for gel characteristics but also for the solution property.

Animals↗
PubMed1989

Evolution of immunoglobulin light chains: cDNA clones specifying sandbar shark constant regions.

Sharks are living fossils that are indistinguishable morphologically from their Devonian ancestors of approximately equal to 400 million years ago. If parallel conservatism characterizes their biochemical evolution, characterization of their immunoglobulin chains could provide information regarding the primordial features of these essential defense molecules. Shark immunoglobulins are polydisperse like those of mammals, but these species lack homogeneous myeloma proteins. This heterogeneity has precluded direct determination of the sequence of elasmobranch light-chain proteins. We have sequenced four cDNA clones that contain the constant-region sequence as well as varying degrees of variable- or joining-region segments. The sandbar shark (Carcharhinus plumbeus) has at least four distinct light-chain constant regions, and these can be considered homologs of mammalian lambda chains. Approximately 40% identity was found in comparison from sharks to mammals. Certain stretches of sequence were remarkably conserved, whereas others varied in a manner consistent with accepted concepts of speciation. One hexapeptide (Ala-Thr-Leu-Val-Cys-Leu) occurred in lambda constant regions of all vertebrate species. There was a universal conservation of certain cysteines, phenylalanines, tryptophans, and glycines and strong identities in the block of residues from Ser-176 to Trp-186. Comparison of the shark sequence with that of the characterized human lambda myeloma protein Mcg indicates a strong conservation of three-dimensional structure in this light-chain domain representing species whose ancestors diverged early in vertebrate evolution. The shark light-chain sequence contains primordial features shared by mammalian kappa and lambda chains and by T-cell receptor beta chains.

Amino Acid Sequence↗
PubMed2003

Regulation of Na,K-ATPase by PLMS, the phospholemman-like protein from shark: molecular cloning, sequence, expression, cellular distribution, and functional effects of PLMS.

In Na,K-ATPase membrane preparations from shark rectal glands, we have previously identified an FXYD domain-containing protein, phospholemman-like protein from shark, PLMS. This protein was shown to associate and modulate shark Na,K-ATPase activity in vitro. Here we describe the complete coding sequence, expression, and cellular localization of PLMS in the rectal gland of the shark Squalus acanthias. The mature protein contained 74 amino acids, including the N-terminal FXYD motif and a C-terminal protein kinase multisite phosphorylation motif. The sequence is preceded by a 20 amino acid candidate cleavable signal sequence. Immunogold labeling of the Na,K-ATPase alpha-subunit and PLMS showed the presence of alpha and PLMS in the basolateral membranes of the rectal gland cells and suggested their partial colocalization. Furthermore, through controlled proteolysis, the C terminus of PLMS containing the protein kinase phosphorylation domain can be specifically cleaved. Removal of this domain resulted in stimulation of maximal Na,K-ATPase activity, as well as several partial reactions. Both the E1 approximately P --> E2-P reaction, which is partially rate-limiting in shark, and the K+ deocclusion reaction, E2(K) --> E1, are accelerated. The latter may explain the finding that the apparent Na+ affinity was increased by the specific C-terminal PLMS truncation. Thus, these data are consistent with a model where interaction of the phosphorylation domain of PLMS with the Na,K-ATPase alpha-subunit is important for the modulation of shark Na,K-ATPase activity.

Adenosine Triphosphate↗
PubMed1998

The effect of shark cartilage extracts on the growth and metastatic spread of the SCCVII carcinoma.

This study was designed to investigate the potential of shark cartilage extracts to inhibit the growth and metastatic spread of a murine solid tumour. The SCCVII carcinoma, implanted in the right rear foot of C3H mice, was used. Following tumour implantation, two different commercially available extracts of shark cartilage (Sharkilage and MIA Shark Powder) were dissolved in water and orally administered to the mice at doses that ranged from 5 to 100 mg per mouse. These injections were repeated on a daily basis for up to 25 days post-implantation of the primary tumour. Compared to non-drug-treated animals, daily administration of the shark cartilage extracts did not show any adverse toxicity (as measured by changes in body weight and lethality). More importantly, none of the shark cartilage doses tested had any retarding effect on the growth of the primary tumour, nor did they inhibit the development of metastases seen in the lungs of the tumour-bearing mice at autopsy. In conclusion, our results offer no support for the proposed use of shark cartilage extracts as an anti-cancer therapy.

Animals↗
PubMed1967

Phylogeny of immunoglobulin structure and function. I. Immunoglobulins of the lemon shark.

Lemon sharks immunized with bovine serum albumin produced two molecular forms of antibodies detectable by passive hemagglutination of antigen-coated, tanned sheep erythrocytes. Throughout the course of immunization 2-ME-sensitive antibody was associated with a 19S immunoglobulin fraction (4-5 mg/ml serum) while late in the course of immunization antibody was found also associated with a 7S immunoglobulin fraction (7-8 mg/ml serum). No evidence for any anamnestic response was found in these animals. Naturally occurring hemagglutinins for sheep erythrocytes were found to be 2-ME-sensitive and present in the 19S immunoglobulin fraction. These immunoglobulin fractions were readily purified by DEAE-cellulose chromatography and Sephadex G-200 gel filtration. Both immunoglobulin molecules yielded equimolar amounts of H and L polypeptide chains when subjected to extensive reduction and alkylation followed by gel filtration in 5 M guanidine-HCl. Antigenically reactive H and L chains were obtained by partial reduction and alkylation followed by gel filtration in 1 M propionic acid. The 7S and 19S immunoglobulin H chains were indistinguishable by fingerprints of tryptic digests, disc electrophoretic patterns, antigenic properties, and mass (molecular weight approximately 70,000), thus suggesting these two molecules to belong to the same immunoglobulin class. The shark 19S and 7S immunoglobulin L chains were indistinguishable from each other by similar criteria and were different from the H chains. These L chains exhibited the electrophoretic heterogeneity of their mammalian counterparts. The 7S (shark immunoglobulin) molecule was shown to have a molecular weight of approximately 160,000 and to consist of 2H and 2L polypeptide chains (total mass congruent with180,000). The 19S molecule was shown to have a molecular weight of 800,000-900,000; therefore, there were probably five 7S subunits per 19S molecule, comparable to mammalian gammaM. Other reasons for considering the 7S and the 19S lemon shark molecules to belong to a class of immunoglobulins comparable to the gammaM class of mammals are that they both have high carbohydrate contents, and H chains of mass similar to micro chains. The lemon shark serum proteins with electrophoretic mobilities comparable to gamma G of mammals were not related to the immunoglobulins of this species. These proteins had no antibody activity and had no antigenic or chemical similarity to either the H chains, the L chains, or the intact immunoglobulin molecules from the lemon shark.

Animals↗
PubMedDate not supplied

Growth and metabolism in the embryonic white-spotted bamboo shark, Chiloscyllium plagiosum: comparison with embryonic birds and reptiles.

Birds and reptiles have been important models for studying the energetics of embryonic development. Studies on these groups reveal three metabolic patterns: an exponential increase in metabolism with embryo age, a sigmoidal increase with age, or a sigmoidal increase followed by a decrease before hatching. Models developed to explain avian metabolic patterns and developmental costs partition total costs between growth and maintenance. To test the generality of these models, we examined embryonic energetics of the oviparous white-spotted bamboo shark Chiloscyllium plagiosum. Oviparous sharks must actively ventilate during development, which could increase their development costs relative to birds and reptiles. Our results demonstrated that bamboo shark embryos have a peaked metabolic pattern and sigmoidal increase in body mass similar to ratites, crocodilians, and some turtles. The total cost of development was higher in bamboo sharks than in reptiles and many birds. However, calculations reveal that the high cost of bamboo shark development can be explained by the relatively long incubation time rather than the additional cost of muscular movement. Finally, an avian model can reasonably describe shark embryonic metabolism, suggesting that movement costs do not significantly alter the metabolic pattern during development.

Animals↗
PubMed2002

The breeding biology of lemon sharks at a tropical nursery lagoon.

Surprisingly little is known about the reproductive behaviour and breeding biology of most shark species, especially in natural populations. Here, we characterize reproductive patterns and use of a natal nursery at Bimini, Bahamas by lemon sharks, Negaprion brevirostris. We systematically and exhaustively sampled young lemon sharks at Bimini annually from 1995 to 2000 and opportunistically sampled adults over the same period. Out of the 897 young sharks sampled, 119 could be assigned to five sampled mothers using microsatellite genotyping. Reproductive females showed strong philopatry to the nursery, returning to Bimini every two years to give birth. Each of these females may rely entirely on the Bimini nursery for recruitment. The protection of known nursery grounds should therefore figure prominently in conservation efforts for large coastal shark species. The reconstruction of paternal genotypes indicates that litters are sired by multiple males, and females mate with different males nearly every breeding cycle. The ubiquitous polyandry reported here raises the possibility that genetic incompatibility and post-copulatory paternity-biasing mechanisms may operate in viviparous sharks.

Animals↗
PubMed2005

Effects of shark hepatic stimulator substance on the function and antioxidant capacity of liver mitochondria in an animal model of acute liver injury.

This study was carried out to investigate whether shark hepatic stimulator substance (HSS) can prevent acute liver injury and affect mitochondrial function and antioxidant defenses in a rat model of thioacetamide (TAA)-induced liver injury. The acute liver injury was induced by two intraperitoneal injections of TAA (400 mg/kg) in a 24 h interval. In the TAA plus shark HSS group, rats were treated with shark HSS (80 mg/kg) 1 h prior to each TAA injection. In this group, serum liver enzyme activities were significantly lower than those in the TAA group. The mitochondrial respiratory control ratio was improved, and the mitochondrial respiratory enzyme activities were increased in the TAA plus shark HSS group. The mitochondrial antioxidant enzyme activities and glutathione level were higher in the TAA plus shark HSS group than in the TAA group. These results suggest that the protective effect of shark HSS against TAA-induced acute liver injury may be a result of the restoration of the mitochondrial respiratory function and antioxidant defenses and decreased oxygen stress.

Animals↗
PubMed2026

Genomic Tracking of Market-Derived Bull Shark Fins Back to Source Population of Origin.

International trade of shark fins remains difficult to monitor because products are rarely labelled to species and are often highly processed, resulting in severely degraded DNA. For several shark species listed under Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), this limits external verification of source populations supplying global trade hubs. Here, we assess whether nuclear genomic approaches can be applied to market-derived bull shark (Carcharhinus leucas) fins to determine their population of origin. We analysed dried fin trimmings collected from retail vendors in Hong Kong SAR, one of the world's largest dried shark fin trade hubs, using a targeted DArTcap single nucleotide polymorphism (SNP) panel, originally developed for population genomic studies of this species. Despite substantial DNA degradation, genomic libraries were successfully obtained for most samples, yielding sufficient SNP data to perform robust provenance and sex assignment. Using a Bayesian mixed-stock analysis, most fin samples were assigned to the Indo-West Pacific (71.4%), with smaller contributions from the western Atlantic (22.6%) and eastern Pacific (3.0%). Genetic sex assignment revealed twice as many males as females, although results indicated a conservative bias towards male assignment due to the limited number of X-linked markers available in degraded samples. Our results demonstrate that genome-wide targeted approaches can be effectively applied to highly processed shark fin products to infer population sources and sex composition. This study provides proof-of-concept for integrating genomics into shark trade monitoring, highlighting its potential to improve traceability, support CITES implementation and inform conservation and fisheries management, particularly for species with well-resolved population structure.

Animals↗
PubMed2004

Postprandial response of gastric pH in leopard sharks (Triakis semifasciata) and its use to study foraging ecology.

Changes in gastric pH of leopard sharks Triakis semifasciata were quantified as an indicator of feeding frequency and ration size. Continuous in situ measurements of gastric pH were made in captive adult leopard sharks using an autonomous pH/temperature probe for periods ranging from 5-16 days. Instrumented sharks were fed meals of squid at different ration sizes. Gastric fluid samples were also taken from non-instrumented juvenile leopard sharks at different time intervals after feeding, and the pH measured to quantify effects of the pH probe in the stomach. Continuous in situ measurements of pH show that empty stomachs have a low pH of 1.54+/-1.42 (mean +/- S.D.) and that feeding causes a rapid increase in pH to 3.11+/-0.71, followed by a gradual decrease back down to baseline levels. There was a positive relationship between changes in pH and meal size (r(2)=0.72, P=0.001). There were no significant differences in pH between continuous in situ and laboratory serial sample measurements. Together these findings indicate that gastric acid secretion may be continuous in leopard sharks, and that changes in gastric pH may be used to estimate feeding chronology, frequency and ration size of leopard sharks in the field.

Analysis of Variance↗
PubMed1999

Brain blood flow and blood pressure during hypoxia in the epaulette shark Hemiscyllium ocellatum, a hypoxia-tolerant elasmobranch.

The key to surviving hypoxia is to protect the brain from energy depletion. The epaulette shark (Hemiscyllium ocellatum) is an elasmobranch able to resist energy depletion and to survive hypoxia. Using epi-illumination microscopy in vivo to observe cerebral blood flow velocity on the brain surface, we show that cerebral blood flow in the epaulette shark is unaffected by 2 h of severe hypoxia (0.35 mg O2 l-1 in the respiratory water, 24 C). Thus, the epaulette shark differs from other hypoxia- and anoxia-tolerant species studied: there is no adenosine-mediated increase in cerebral blood flow such as that occurring in freshwater turtles and cyprinid fish. However, blood pressure showed a 50 % decrease in the epaulette shark during hypoxia, indicating that a compensatory cerebral vasodilatation occurs to maintain cerebral blood flow. We observed an increase in cerebral blood flow velocity when superfusing the normoxic brain with adenosine (making sharks the oldest vertebrate group in which this mechanism has been found). The adenosine-induced increase in cerebral blood flow velocity was reduced by the adenosine receptor antagonist aminophylline. Aminophylline had no effect upon the maintenance of cerebral blood flow during hypoxia, however, indicating that adenosine is not involved in maintaining cerebral blood flow in the epaulette shark during hypoxic hypotension.

Adenosine↗
PubMed2002

Electroreception in juvenile scalloped hammerhead and sandbar sharks.

The unique head morphology of sphyrnid sharks might have evolved to enhance electrosensory capabilities. The 'enhanced electroreception' hypothesis was tested by comparing the behavioral responses of similarly sized carcharhinid and sphyrnid sharks to prey-simulating electric stimuli. Juvenile scalloped hammerhead sharks Sphyrna lewini and sandbar sharks Carcharhinus plumbeus oriented to dipole electric fields from the same maximum distance (approximately 30 cm) and thus demonstrated comparable behavioral-response thresholds (<1 nV cm(-1)). Despite the similarity of response threshold, the orientation pathways and behaviors differed for the two species. Scalloped hammerheads typically demonstrated a pivot orientation in which the edge of the cephalofoil closest to the dipole remained stationary while the shark bent its trunk to orient to the center of the dipole. By contrast, sandbars swam in a broader arc towards the center of the dipole. The different orientation patterns are attributed to the hydrodynamic properties of the cephalofoil, which enables the hammerheads to execute sharp turns at high speed. The greater trunk width of the sandbar sharks prevented them from demonstrating the same degree of flexibility. Therefore, although the sphyrnid head morphology does not appear to confer a greater sensitivity to prey-simulating dipole electric fields, it does provide (1). a greater lateral search area, which may increase the probability of prey encounter, and (2). enhanced maneuverability, which may aid in prey capture.

Animals↗
PubMedDate not supplied

[Spatial distribution of sharks captures in the Pacific of Nicaragua and its relationship with several oceanographic variables].

Between August 1995 and August 1997 long line fishing techniques and a bathythermograph were used to correlate some physical variables with the spatial distribution of four shark species in 26 fishing cruises off the Nicaraguan Pacific Coast. They were the thresher (Alopias vulpinus), blue (Prionace glaucea), gray (Carcharhinus falciformis) and hammer (Sphyra lewini). All species concentrated in the southeastern Nicaraguan Pacific, at the seasonal upwelling area of Papagayo Gulf. The range of sea surface temperatures in which the sharks were captured was 25-28 degrees C. We could clearly associate this physical parameter with shark availability. The vertical distribution of the captured sharks suggests that they occupy termocline levels above the 15 degrees C isotherm. Although these species are oceanic, the blue shark was captured in ocean waters over the 1800 m isobar, while the grey and thresher sharks where close to the continental shelf. Body length in decreasing order are: thresher (210-290 cm, SN = 21), blue (60-240 cm, SN = 13) and gray (80-200 cm, SN = 17).

Animals↗