Triakis Semifasciata Research Articles

Digital image analysis of shark gills: modeling of oxygen transfer in the domain of time.

Digital radiographic imaging of blood circulation through leopard shark gills establishes a secondary lamellar transit time of 6.5 s. This duration, combined with estimates of cardiac output and hemoglobin-oxygen affinity, permits novel modeling of gill oxygen transfer in the time domain. The temporal model allows assessment of factors contributing to previously noted discrepancies between physiological and morphometric branchial oxygen conductance estimates. Lamellar transit time for shark blood is 20 times greater than human alveolar transit time, and thus correlates with a slower rate of hemoglobin-oxygen binding and a greater diffusion distance.

Crystal structure of the unique parvalbumin component from muscle of the leopard shark ( Triakis semifasciata) : The first X-ray study of an α-parvalbumin

The three-dimensional structure of parvalbumin from leopard shark ( Triakis semifasciata) with 109 amino acid residues (α-series) is described at 1.54 Å resolution. Crystals were grown at 20 °C from 2.9 m-potassium/sodium phosphate solutions at pH5.6. The space group is P3 121 and unit cell dimensions are a = b = 32.12 A ̊ and c = 149.0 A ̊ . The structure has been solved by the molecular replacement method using pike 4.10 parvalbumin as a model. The final structure refinement resulted in an R-factor of 17.3% for 11,363 independent reflections at 1.54 Å resolution. The shark parvalbumin shows the main features of all parvalbumins: the folding of the chain including six α-helices, the salt bridge between Arg75 and Glu81, and the hydrophobic core. Compared to the structure of β-parvalbumins from pike and carp, one main difference is observed: the chain is one residue longer and this additional residue, which extends the F helix, is involved through its C-terminal carboxylate group in a network of electrostatic contacts with two basic residues, His31 in the B helix and Lys36 in the BC segment. Furthermore, hydrogen bonds exist between the side-chains of Gln108 (F helix) and Tyr26 (B helix). There is therefore a “locking” of the tertiary structure through contacts between two sequentially distant regions in the protein and this is likely to contribute to making the stability of an α-parvalbumin higher in comparison to that of a β-parvalbumin. The lengthening of the C-terminal F helix by one residue appears to be a major feature of α-parvalbumins in general, owing to the homologies of the amino acid sequences. Besides the lengthening of the C-terminal helix, the classification of the leopard shark parvalbumin in the α-series rests upon the observation of Lys13, Leu32, Glu61 and Val66. As this is the first crystal structure description of a parvalbumin from the α-phylogenetic lineage, it was hoped that it would clearly determine the presence or absence of a third cation binding site in parvalbumins belonging to the α-lineage. In β-pike pI 4.10 parvalbumin, Asp61 participates as a direct ligand of a third site, the satellite of the CD site. In shark parvalbumin, as in nearly all α-parvalbumins, one finds Glu at position 61. Unfortunately, the conformation of the polar head of Glu61 cannot be inferred from the X-ray data. Nevertheless, the absence of density suggests that this side-chain is not participating in any coherent co-ordination of an additional cation. On the other hand, we observe an ordered water molecule in contact with the carboxylate groups of Asp53 and Glu59, which are ligands of the third site of a typical β-parvalbumin. So, this analysis cannot unequivocally resolve whether there is a third cation binding site in α-parvalbumins.

Demography of the central california population of the Leopard Shark (Triakis semifasciata)

Demographic analyses can be quite useful for effectively managing elasmobranch fisheries. However, they require valid estimates of age-specific mortality and natality rates, in addition to information on the distribution, abundance, habits and reproduction of the population, to produce reliable estimates of population growth. Because such detailed ecological information is usually unavailable, complete demographic analyses have been completed for only four shark species: the spiny dogfish, Squalus acanthias; the soupfin shark, Galeorhinus australis; the lemon shark, Negaprion brevirostris; and most recently the sandbar shark, Carcharhinus plumbeus. In California, reliable estimates of age, growth, mortality, age at maturity, and fecundity are available only for the leopard shark, Triakis semifasciata. A demographic analysis of this species yielded a net reproductive rate (Ro) of 4.467, a generation time (G) of 22.35 years, and an estimate of the instantaneous population growth coefficient (r) of 0.067. If the mean fishing pressure over 10 years (F= 0.084) is included in the survivorship function, Ro and r are reduced considerably, especially if leopard sharks first enter the fishery at early ages. A size limit of 120 cm TL (estimated age 13 years), especially for female sharks, is tentatively proposed for the leopard shark fishery.

Growth and demography of the Pacific Angle Shark (Squatina californica), based upon tag returns off California

Knowledge of the age, growth and demography of an organism can be quite useful for managing its fishery. However, for many elasmobranch species, no valid estimates of age, growth and therefore age-specific mortality and natality rates are available. Thus, even though the distribution, abundance, habits and reproduction of a population may be known, no reliable estimates of population growth are possible. As a result, detailed demographic analysis has been completed for only a few shark species (e.g. the California leopard shark, Triakis semlfasciata). All age-determination techniques attempted for the Pacific angel shark (Squatina californica) have met with difficulties. Recently, however, we have accumulated data on 69 tag-recaptures and have used this information to model a von Bertalanffy growth function (VBGF) to predict the growth of this commercially exploited shark species. We performed a demographic analysis of this species, which yielded a net reproductive rate (R0) of 2.25, a generation time (G) of 14.5 years, and an estimate of the instantaneous population growth coefficient (r) of 0.056 year-1, assuming that only natural mortality (M) was occurring, estimated to be 0.2 year-1. When reasonable estimates of fishing mortality (F) are included in the survivorship function, Ro and r are reduced considerably. Presently, Pacific angel sharks first enter the fishery at the same size and age at which they first reproduce. Until accurate estimates of M and Fare available, it would be prudent to set a size limit considerably above the size at first reproduction to protect the Pacific angel shark in California.

Gonadotropin hormone‐releasing hormone (GnRH) immunoreactivity in the mesencephalon of sharks and rays

Other than association with the terminal nerve (TN), little is known concerning the distribution of gonadotropin hormone-releasing hormone (GnRH) in elasmobranchs. The purpose of this study was to identify GnRH immunoreactivity in the brains of three elasmobranch species with special regard to the mesencephalon. The round stingray (Urolophus halleri), thornback guitarfish (Platyrhinoidis triseriata), and leopard shark (Triakis semifasciatus) were used and immunocytochemistry was performed with antisera to both salmon and mammalian GnRH. A large GnRH-immunoreactive (ir) nucleus extends rostrocaudally for approximately 1.5 mm along and adjacent to the midline of the midbrain near the area of the oculomotor nerve. GnRH-ir fibers surround the nucleus and are found diffusely throughout the mesencephalon; some of the fibers may contact the ventricle. The medulla and spinal cord contain ir fibers that most likely originate from the midbrain nucleus. Mesencephalic GnRH-ir cell groups have been reported in representatives of all vertebrate classes with the exception of agnathans and mammals. Such a well-developed cell group in elasmobranchs may aid in understanding the evolution of GnRH systems with regard to the mesencephalon as well as providing insight to the functional significance of this cell group. Possible homologies to mesencephalic GnRH systems reported in other vertebrates is discussed as well.

The effectiveness of sodium lauryl sulphate as a shark repellent in a laboratory test situation

Swim‐through chemical repellency tests, using sodium lauryl sulphate (SLS), cupric acetate, and rotenone, were conducted in a specially‐designed roundabout tank on horn sharks, Heterodontus francisci, swell sharks, Cephaloscylliun ventriosum, and leopard sharks, Triakis semifasciata. Effective concentration thresholds (EC50s) were calculated for two levels of response: (1) minimum noticeable and (2) strong. The SLS EC50s were: horn shark 43.6 and 174.5 ppm; swell shark 95.1 and 160.0 ppm; and leopard shark inconclusive and 113.1 ppm. No response was discernible from cupric acetate. Rotenone evoked a weak response with an EC50 of 5.7 ppm, but no strong response.The ratio of the minimum noticeable EC50: 24‐hour lethal concentration (LC50) indicated the relative repellency (compared to toxicity) of the chemicals. The ratio for SLS was 19:1 and for rotenone 57:1. SLS did not provoke a repellency response at a low enough concentration to function effectively as a classical, surrounding‐cloud type, repellent. The range of potency of SLS, however, does allow it to be used as a directional repellent.

Cardiac function of the leopard shark, Triakis semifasciata

The pressure difference between the cardinal sinus and the pericardium, and the transmural ventricular diastolic pressure at rest and during swimming in the leopard shark, Triakis semifasciata, was measured to characterize the mechanism of cardiac filling in chronically-instrumented fish and to evaluate cardiac responses to swimming. Echo-Doppler and radiographic imaging were also used to fully describe the cardiac cycle. Swimming induces an increase in preload as manifested by a large increment of cardinal sinus pressure (0.26/0.20 [systolic/diastolic] to 0.49/0.32 kPa) which always exceeds pericardial pressure. Increases in both mean ventricular diastolic transmural pressure (0.30–0.77 kPa) and cardinal sinus pressure during swimming suggest increased cardiac filling by vis a tergo as the mechanism for augmenting cardiac output. In contrast to mammals, the fluid-filled pericardial space of elasmobranchs is considerably larger and the pericardium itself does not move in concert with the heart throughout the cardiac cycle. Also, modest increases in heart rate drastically curtail the duration of diastole, which becomes much less than that of systole, a phenomenon not found in mammals. In the absence of tachycardia (<40 bpm), ventricular filling is characterized by a period of early rapid filling, and a late period of filling owing to atrial systole, separated by a period of diastasis. Ventricular filling in elasmobranchs is thus biphasic and is not solely dependent on atrial systole. Atrial diastole is characterized by three filling periods associated with atrial relaxation, ventricular ejection, and sinus venosus contraction. The estimated ventricular ejection fraction of Triakis (80%) exceeds that of the mammalian left ventricle.

Blood Respiratory Properties and the Effect of Swimming on Blood Gas Transport in the Leopard Shark Triakis Semifasciata

ABSTRACT Changes in vascular pressures, blood respiratory properties and blood gas transport induced by swimming were investigated in the leopard shark Triakis semifasciata (Girard). In resting sharks, the mean ventral and dorsal aortic pressures (systolic/diastolic) were 6.8/5.6 kPa and 4.5/3.9 kPa, respectively, and only the former were increased significantly during swimming. Swimming also caused a significant decline in venous , (1.6 to 0.9kPa), O2 content (0.9 to 0.4 mmol l−1) and percentage O2 saturation (, 39 to 18%) but the arterial variables were not affected. A significant decline in venous pH and an increase in venous also occurred during swimming but lactate concentration did not increase during or after swimming. An in vivo dissociation curve compiled from blood and data for sharks in the resting, swimming and post-swimming recovery phases shows a mean P50 of 2.04 kPa, as determined by Hill transformation. The pH-bicarbonate plot for this fish shows a weak blood buffer capacity of 9.3 mmol I−1 pH unit−1 and during swimming the average blood pH and bicarbonate concentration follow the buffer line which was not compensated in recovery. Neither oxygenated nor deoxygenated blood pH values were affected by CO2 equilibration, suggesting the absence of a Haldane effect. Thus, at the expense of respiratory acidosis, Triakis can aerobically sustain long (up to 60 min) and moderately intense (0.45 Ls−1, where L is body length) periods of swimming by increasing cardiac output and tapping its venous reserve.

Aspects of Shark Swimming Performance Determined Using a Large Water Tunnel

ABSTRACT A large, sea-going water tunnel was used in various studies of shark swimming performance. The critical swimming velocity (Ucrit, an index of aerobically sustainable swimming speed) of a 70 cm long lemon shark (Negaprion brevirostris Poey) was determined to be 1.1 Ls−1, where L is body length. The Ucrit of the leopard shark (Triakis semifasciata Girard) was found to vary inversely with body size; from about 1.6Ls−1 in 30–50cm sharks to 0.6Ls−1 in 120cm sharks. Large Triakis adopt ram gill ventilation at swimming speeds between 27 and 60cms−1, which is similar to the speed at which this transition occurs in teleosts. Analyses of tail-beat frequency (TBF) in relation to velocity and body size show that smaller Triakis have a higher TBF and can swim at higher relative speeds. TBF, however, approaches a maximal value at speeds approaching Ucrit, suggesting that red muscle contraction velocity may limit sustained swimming speed. The TBF of both Triakis and Negaprion rises at a faster rate with swimming velocity than does that of the more thunniform mako shark (Isurus oxyrinchus Rafinesque). This is consistent with the expectation that, at comparable relative speeds, sharks adapted for efficient swimming should have a lower TBF. The rates of O2 consumption of swimming lemon and mako sharks are among the highest yet measured for elasmobranchs and are comparable to those of cruise-adapted teleosts.

Histochemical localization of Na+–K+ ATPase and carbonic anhydrase activity in gills of 17 fish species

Activities of two enzymes considered to be involved in NaCl regulation, Na+–K+ ATPase and carbonic anhydrase, were localized in gill epithelia of 14 teleost, 2 agnathan, and 1 shark species through light microscopic histochemistry. Findings were confirmed by use of appropriate inhibitors (ouabain, acetazolamide). Na+–K+ ATPase activity was detected in chloride cells of most marine teleost species (six of eight) and of marine leopard shark and hagfish, but never in freshwater fish gills. In general, this finding agrees with past biochemical assays showing gill Na+–K+ ATPase activity to be highest in marine teleosts. Staining for carbonic anhydrase took one of three patterns among species: gill pavement cells or chloride cells, or both, were stained. Interspecific distribution of these patterns bore little relation to taxonomy or to habitat salinity, although chloride cells of euryhaline teleosts seemed more likely to stain than chloride cells of stenohaline teleosts, freshwater or marine. Given the lack of a definite correlation with salinity, it is concluded that fish gill carbonic anhydrase may not function in NaCl regulation as much as in acid–base regulation; the enzyme's role in preventing systemic pH imbalance is discussed.

Osteoclasts can be induced in fish having an acellular bony skeleton

Kelp bass (Paralabrax clathratus) and leopard sharks (Triakis semifasciata) are characterized by an acellular (anosteocytic) bony skeleton and a focally calcified cartilaginous endoskeleton, respectively. These skeletal forms are not considered to function as mineral reservoirs. Previous studies showed that implanted bone particles are resorbed in rats by large multinucleated cells with ultrastructural features (ruffled borders) characteristic of osteoclasts. We tested the ability of fish to resorb bone matrix and to adapt to reduced salinity conditions. Bone particles were implanted in sharks and bass maintained in seawater (34 ppt, 40.5 mg of calcium per dl) or in diluted seawater (26 ppt, 28.5 mg of calcium per dl). Sera and elicited tissues were harvested 4 weeks later. In sharks, bone particles were not resorbed, and multinucleated cells were not evident under either normal or hyposalinity conditions. Shark sera were isoosmolar with the seawater or diluted seawater, with serum chemistries of the hyposalinity group reflecting the 23% reduction in environmental minerals and electrolytes, compared to sharks in normal seawater. In marked contrast, bass adapted to diluted seawater resorbed bone particles and maintained normal serum chemistries. Electron microcopy showed that the bone particles were surrounded by large, foamy multinucleated cells, many with membrane specializations typical of osteoclasts from higher vertebrates, i.e., extensive clear zones apposed to intact bone matrix and active ruffled borders overlying areas of matrix undergoing dissolution. Although osteoclasts had not been described in these fish, this study shows that bass have stem cells that can be stimulated to differentiate into bone-resorbing osteoclasts.

On the yellowish brown pigment granules in the interrenal cells of anglerfish and leopard shark.

Yellowish brown pigment called lipofuscin is included in the adrenal gland of variousmammalian species and appears as abundant granules in the cortical cells of its zona recticularis. Among many fish species examined by the present author, the yellowish brown pigment granuleswere abundantly detected only in the interrenal cells of the anglerfish Lophius litulon and the leopardshark Triakis scyllia. For this examination, three large-sized specimens of the anglerfish wereused and their body weights were 2.5 to 8.6kg. In the leopard shark, appearance and accumu-latiop of the pigment granules were remarkable in four large-sized specimens(118-123cm in bodylength) among ten specimens(60-123cm)investigated. Accordingly, it was suggested that the yellowish brown pigment granules appeared and revealed conspicuous accumulation in the inter-renal cells of large-sized fishes with advanced age

Infectivity of, and Laboratory Infection with, an Elasmobranch Cestode, Lacistorhynchus tenuis (Van Beneden, 1858)

The presumptive life cycle of Lacistorhynchus tenuis (Cestoda) involves 3 hosts: a copepod, a teleost, and an elasmobranch. This study describes the laboratory infection of the copepod, Tigriopus californicus, mosquitofish, Gambusia affinis, and the leopard shark, Triakis semifasciata. At room temperature, L. tenuis coracidia and procercoids were infective for up to 2 and 4 wk, respectively. The development of eversible tentacles by the plerocercoid took 3 mo at 12 to 15 C. Leopard sharks force-fed plerocercoids from laboratory infected mosquitofish and white croakers, Genyonemus lineatus collected from the field were infected with immature adults. More than 4 mo are required for L. tenuis to develop proglottids.

Characterization of hepatic growth hormone binding sites in two fish species, Gillichthys mirabilis (teleostei) and Acipenser transmontanus (chondrostei)

To obtain information on the presence of growth hormone (GH) receptors in liver of nonmammalian vertebrates the specific binding of 125I-bovine growth hormone (bGH) to liver membranes of seven species representing the major groups was studied by radioreceptor assay. A substantial degree of specific binding was detected with sturgeon ( Acipenser transmontanus) liver membranes and a much lower amount was detected on hepatic membranes of Gillichthys mirabilis. No significant specific binding was detected on liver membranes of pigeon, turtle, bullfrog, tilapia, or leopard shark. Gillichthys and sturgeon liver membranes were further characterized and compared with hepatic membranes from male rabbits. The sturgeon and Gillichthys membranes showed binding that was dependent upon time, temperature, pH, and membrane concentration. Scatchard analysis of the binding of 125I-bGH to sturgeon and rabbit membranes revealed both high and low affinity binding sites. The high affinity sites had K A values of 3.1 × 10 11 and 1.0 × 10 11 M −1, and capacities of 12 and 50 fmol/mg protein, respectively. Membranes from Gillichthys liver contained only a single class of binding sites with a K A of 6.7 × 10 9 M −1 and a binding capacity of 49 fmol/mg. Hormonal specificity of the sturgeon and Gillichthys hepatic binding sites was studied using methionyl-human GH (met-hGH), ovine prolactin (oPRL), and a crude preparation of sturgeon (st)GH. The met-hGH and stGH inhibited the binding of 125I-bGH to sturgeon liver membranes while only met-hGH displaced labeled bGH from Gillichthys liver membranes. One μg of oPRL did not significantly inhibit 125I-bGH binding in either membrane assay. Based on these studies, sturgeon hepatic GH receptors seem to be more like those of nonprimate mammals than those of teleosts. Our results, in conjunction with the data of J. N. Fryer ( Gen. Comp. Endocrinol. 39, 123–130 (1979)), indicate that considerable evolutionary divergence has occurred among teleost hepatic GH receptors. Thus, vertebrate GH receptors seem to have undergone at least as much evolution as has the hormone itself.

Histological and enzymatic studies on the renal tubules of some marine elasmobranchs.

Renal tubules in the dog shark, leopard shark, and red skate were examined histologically and analyzed histochemically for enzymes. Cells of the distal and collecting tubules exhibit extensive interdigitations and large intercellular spaces, suggesting that these tubules are sites of sodium reabsorption. Although Na-K-ATPase is very scarce to nonexistent in the distal and collecting tubules, very intense carbonic anhydrase activity in these segments indicates that they secrete large amounts of hyrogen ion and reabsorb sodium by H+ /Na+ exchange process. Epithelial cells of the necks are not interdigitated, tightly join adjacent cells, and have low enzyme activities. They seem to be passively permeable to the water. Necks are attached to the distal tubules with scant intervening stroma. It seems likely that the stroma has a high osmotic pressure resulting from absorption of solutes in the distal tubules. Water may be reabsorbed from necks to stroma because of a concentration gradient of the solutes distributed between these sites.

Timing of Vertebral-Band Deposition in Tetracycline-Injected Leopard Sharks

In late summer 1979, 948 leopard sharks Triakis semifasciata were tagged and released into San Francisco Bay after being injected with the bone-labeling reagent oxytetracycline (OTC). The fluorescent time mark was compared to new growth zones in the vertebral centra of tagged fish recovered over 3 years to determine how often the calcified bands are formed. As of 31 December 1982, 25 vertebral samples were recovered and examined. Although OTC deposition was variable, an intense fluorescent mark was evident in 12 individuals. The results confirm that one opaque (highly calcified) zone and one translucent zone are deposited per year, and that these zones can be used reliably in aging this species within the size group examined. The progression of band formation indicates that opaque zones probably form sometime between May and September. Received July 22, 1983 Accepted March 18, 1984

Wound healing in Sharks

Pieces of skin together with scales measuring 7×7 mm were removed from a mature Nurse Shark and a mature Leopard Shark. In the following 2 weeks the wound area secreted mucus, later it contracted and the epidermis regenerated, then it expanded again and newly formed scales erupted. Most of the scar area was covered with scales after 4 months. In the regenerated dermal skeleton the scales show a high degree of variability in that they are much larger and much more complex than the scales of control areas. The repair scales are no longer arranged in diagonal rows and are not so perfectly oriented in a caudal direction as the control scales. Wolpert's concept of positional information in pattern formation can explain this type of regeneration behaviour. The fact that regeneration of the dermal skeleton is not perfect leads to the assumption that the flow of positional information was temporarily inhibited by the surgery.

Partial characterization of the bile salt-dependent triacylglycerol lipase from the leopard shark pancreas

Leopard shark triacylglycerol lipase has been characterized as a crude pancreatic preparation. The enzyme demonstrated an absolute requirement for trihydroxy bile salts for activity with natural bile salts of the shark giving a 4-fold greater stimulation of activity than pure sodium taurocholate. Bile salts also protected the enzyme from apparent inactivation by p-chloromercuribenzoate and trypsin treatment. The shark lipase demonstrated a temperature optimum of 36° C and was rapidly inactivated at 50° C even in the presence of bile salts. Divalent metal ions were required for activity with Ca 2+ providing the greatest stimulation. At 22° C, pH 8.5 and in the presence of natural bile salts, the apparent V was about 0.6 μmol fatty acid released/min per mg protein. The shark enzyme hydrolyzed over 90% of the fatty acids from trioleoylglycerol and methyl esters of pancreatic lipase-resistant fatty acids were hydrolyzed at the same rate as typical fatty acid methyl esters. Hydrolysis of triacylglycerol proceeded about ten-times faster than wax ester hydrolysis. The kinetic properties of the leopard shark enzyme were compared to other bile salt-dependent lipolytic enzymes. Pancreatic lipase activity was not dectected.

Distribution of prostaglandins in the animal kingdom

A semiquantitative determination of prostaglandins was carried out in twenty two species of vertebrates and invertebrates by bioassay. Prostaglandins were detected not only in higher vertebrates but also in carp, sheat-fish, leopard shark, crawfish, blue crab, mussel, scallop, sea-squirt and sea-anemone. In lower animals, gastrointestinal tissue, air bladder, heart and gill were inclined to have a moderately higher level of prostaglandins than the other tissues.

High levels of pancreatic nonspecific lipase in rattlesnake and leopard shark.

Hydrolysis of synthetic triglycerides by rattlesnake and leopard shark pancreatic enzymes revealed striking differences in specificity, depending on the presence or absence of sodium taurocholate. Without added sodium taurocholate the classical specificity of pancreatic lipase was expressed. Rattlesnake enzymes, in the presence of sodium taurocholate, attacked the unsaturated oleic acid in the 2-position of racemic glycerol-1-palmitate-2-oleate-3-stearate nearly twice as fast as either outside saturated fatty acid. In this instance, over 90% of the monoglyceride which accumulated were 1-monoglyceride. These results are attributed to very high levels of bile salt activated nonspecific lipase. Eight vertebrate species were compared. With the exception of the rattlesnake and leopard shark, the other species (3 elasmobranchs and 3 mammals) all exhibited low levels of nonspecific lipase, e.g. less than 5% hydrolysis of the 2-position of racemic glycerol-1-palmitate-2-oleate-3-stearate in the presence of sodium taurocholate.