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The American Elasmobranch Society


Abstracts of AES Scientific Papers
American Elasmobranch Society 1995 Annual Meeting
Edmonton, Alberta, CANADA
ABSTRACTS - Part 1: Amesbury through Ellis
Amesbury, Elena, and Snelson, Franklin F.

Department of Biology, University of Central Florida, Orlando, Florida, 32816 USA

Structure and histology of uterine trophonemata in the Atlantic stingray, Dasyatis sabina.

The mode of reproduction in all rays is aplacental viviparity, also termed ovoviviparity. Embryos are nourished by egg yolk during the early phases of development, but during later phases the source of nutrition is shifted to a secretion produced by the maternal uterus. We analyzed aspects of embryonic nutrition in Dasyatis sabina throughout gestation. Early gestation through mid-gestation embryos had an external yolk sac that ranged in weight from 66 mg to 2 mg, respectively. By late July the external yolk was absorbed, no internal yolk sac was present, and the embryos were entirely dependent upon histotroph nutrition. The inner wall of the maternal uterus was lined with vascularized evaginations called trophonemata. In the non-gravid uterus, trophonemata averaged 2.6 mm long, maximum 3.2 mm, and uniformly 0.4 mm wide. By early gestation trophonemata maximum length reached 15.9 mm. After this rapid increase, average trophonemata length stayed relatively constant through mid- and late-gestation, although a few hypertrophied strands attained maximum length of 31.7 mm. Width continued to vary throughout gestation. After parturition the strands began to shrink and resembled pre-gestation trophonemata. The histological structure of trophonemata will be described.

Keywords: Dasyatis, uterus, stingray, elasmobranch, embryo, nutrition
Bain, Christopher A.1, Lacy, Eric R.2, and Miller, Donald H.3

Poster

1. Grice Marine Biological Laboratory, University of Charleston, 205 Fort Johnson Rd., Charleston, South Carolina, 29412, USA

2. Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, South Carolina, 29425, USA

3. Department of Pharmacology, Medical University of South Carolina, Charleston, South Carolina, 29425, USA

The kallikrein-kinin system in the Atlantic Stingray

The renal kallikrein-kinin system in mammals participates in the regulation of urine volume. We have begun to characterize the components of this system in the stingray in order to investigate its possible role in the regulation of renal function in elasmobranch fish. When the euryhaline Atlantic Stingray Dasyatis sabina travels from seawater into estuarine waters, a compensatory increase in urine volume occurs, but the regulation of this process is not understood. We have identified a kallikrein-like activity (KLA) in various tissues of the stingray, and renal activity is increased 24 hrs after the animals are moved from seawater (910 mOsm/l) to dilute seawater (459 mOsm/l). Immunohistochemical studies show localization in extraglomerular cells of the mesangium. The kidney also contains a kinin-like substance detected by bradykinin (BK) RIA. When the mammalian peptide lysyl-BK is administered to the stingray, a 25% change in renal blood flow could be demonstrated with laser-doppler flowmetry. KLA in other osmoregulatory tissues also increased after dilution. The evidence suggests that a kallikrein-kinin system exists in the Atlantic Stingray, and that the system may be involved in osmoregulation. Supported by NIH HL44671.

Keywords: stingray, kidney, osmoregulation, kinin, kallikrein
Barton, Kimby N.1, Buhr, Mary M.2, and Ballantyne, J. S.1

1. Department of Zoology, University of Guelph, Guelph, Ontario, N1G 2W1 Canada

2. Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario N1G 2W1. Canada.

The effects of urea and trimethylamine oxide (TMAO) on membrane properties: The elasmobranch connection.

The effects of the major organic solutes of marine elasmobranchs (urea and trimethylamine oxide (TMAO)) on membrane fluidity were determined in a model membrane system. Fluorescence polarizations of 1,6-diphenyl-1,3,5-hexatriene (DPH), trans-parinaric acid (tPNA) and cis-parinaric acid (cPNA) were used to study the effects of urea and TMAO on the fluidity of dipalmitoyl phosphatidylcholine (DPPC) liposomes. A further study was conducted to relate elasmobranch membrane composition to the effects of these organic solutes. A preliminary study (Glemet and Ballantyne, unpublished observations) found that although there were no differences in the phospholipid headgroups, liver mitochondrial membranes of an elasmobranch had phospholipids that were substantially more saturated than membranes of non-elasmobranch fish. Since the mitochondrial membrane does not contain cholesterol, adaptation of cholesterol-containing membranes to the presence of urea may employ other strategies. We have therefore, examined a cholesterol containing membrane (the plasma membrane of the red blood cell) from a urea-retaining elasmobranch Raja erinacea and an osmoregulating teleost Pleuronectes americanus.

Keywords: urea, TMAO, membrane properties, Raja erinacea, Pleuronectes americanus
Bodine, A. B.1, Wyffels, J. T.1, Luer, C. A.2, Walsh, C. J.2, and Scott, T. R.3

1. Department of Animal, Dairy and Veterinary Sciences, Clemson University, Clemson, South Carolina 29634-0361 USA

2. Mote Marine Laboratory, Sarasota, Florida 34236 USA

3. Department of Poultry Science, Clemson University, Clemson, South Carolina 29634-0379 USA

Effect of a T-cell inhibitor on differential counts and immune organ histology in nurse sharks, Ginglymostoma cirratum.

Preliminary experiments have been conducted with the potent helper T-cell inhibitor cyclosporin A (Cyc A) (Sandoz) to determine if it would adversely affect the white cell population or the cellular structure/distribution in immune organs of the nurse shark. Nurse sharks were injected (IM) a total of three times at 48 hour intervals with either olive oil vehicle (control, N=2), 25 mg cyclosporin/kg body weight (N=4), or 50 mg cyclosporin/kg body weight (N=4). Prior to injections, and at frequent intervals thereafter, blood samples were withdrawn for differential counts and hematocrits. All animals at the high dose level became moribund and expired within 4 days after the final injection. Within two days following the 1st injection, animals at both dose levels demonstrated an inversion of the lymphocyte: granulocyte ratio which persisted for 72-96 hrs after final injection or until death in the high dose animals. Hematocrits were significantly lowered in either treatment group compared to control (P<.05), but in surviving animals, hematocrits returned to normal 3-5 days following the last injection of Cyc A. Histologically, there appeared to be a dose-dependent degeneration of tissue and cell integrity in the thymus, epigonal, and spleen of treatment animals with greater amounts of mitotic activity, cellular debris, and epithelial infiltration than in control animals. Keywords: Nurse shark, Cyclosporin A, T-cell inhibitor, Histology, Differential counts
Bonfil-Sanders, Ramon 1,2

1 Instituto Nacional de la Pesca, Chilpancingo 70, Mexico City, 06000, MEXICO 2. Fisheries Centre, UBC. 2204 Main Mall, Vancouver B.C. V6T 1Z4 CANADA

Global trends and status of elasmobranch fisheries.

A brief synopsis of recent trends in elasmobranch exploitation and management on a worldwide basis is presented. The world elasmobranch catch reported in 1991 is 704,000 t and present trends indicate forecasts of 755,000-827,000 t by the year 2000. However, the present total annual catch inclusive of discarded and unreported catches is estimated at around 1.35 million tonnes. An index of relative production is developed and used to diagnose elasmobranch exploitation in each of 15 FAO's Major Statistical Areas. Three of these Areas could probably support significant increases in elasmobranch exploitation while another five Areas are not likely to sustain further expansion in yields. The bulk of the world's elasmobranch catch is taken by 26 countries: Japan, Indonesia, India, Taiwan and Pakistan have the highest average yields of elasmobranchs in the world. The estimated by-catches of elasmobranchs (mainly sharks) in high-seas fisheries of the world are 20,000-38,000 t/y in the recently banned driftnet fisheries, 232,425 t/y in the various longline fisheries for tunas and billfishes and 6,345 t/y in purse seine tuna fisheries. This is equivalent to an estimated total by-catch of 11.6-12.7 million sharks per annum. The discard of sharks in these fisheries is also very high, probably in the order of 230,000-240,000 t/y. Elasmobranch fisheries are poorly researched and managed worldwide: only Australia, New Zealand and USA are known to have specific management and research programmes for elasmobranch fisheries. The general problems found for appraising elasmobranch fisheries and the need for management are discussed.

Keywords: elasmobranch fisheries, catch trends, bycatches, worldwide.
Bradley, James Lee, IV, and Tricas, Timothy C.

Department of Biology, Florida Institute of Technology, Melbourne, Florida, 32901-6988 USA

Multiple foraging strategies to maximize energy return in the Atlantic stingray, Dasyatis sabina.

The diet of the Atlantic stingray, Dasyatis sabina, is temporally variable but it is unknown whether this feeding pattern reflects seasonal prey abundance or active preferences for prey with high energy return. Caloric content was determined for the six major prey types: in rank order amphipods, isopods, ophiuroids, mysids, polychaetes, and bivalves. Maximum caloric density occurs in the mysids Bowmaniella spp. (5.98 mg/AFDW) and the minimum in the isopod Cymadusa faxoni (4.73 mg/AFDW). Caloric density among species varies within these taxonomic orders from 2.1% in isopods to 14.9 % in amphipods. Despite the perennial occurrence of ophiuroids at the study site, they are taken only in the summer when caloric content is 16.5% higher than in winter. The prey of D. sabina are divided into two functional groups: 1) small prey that require negligible handling time, and 2) large prey that require post-capture processing. It is proposed that energetic returns from small crustaceans are maximized by selection of dense patches whereas returns from large prey are constrained by post-capture processing.

Keywords: bivalves, caloric content, crustaceans, Dasyatis sabina, energetics, foraging, handling time, ophiuroids, predation, stingray
Bush, Aaron, and Holland, K.

1. Department of Zoology, University of Hawaii, Edmondson Hall, Honolulu, Hawaii 96822 USA

2. Hawaii Institute of Marine Biology, P.O. Box 1346, Kaneohe, Hawaii 96744 USA

Gastric evacuation in juvenile scalloped hammerhead sharks, Sphyrna lewini

Gastric evacuation was studied in juvenile scalloped hammerhead sharks (Sphyrna lewini) in Kaneohe bay, Oahu, Hawaii. Sharks were caught using handlines and kept in individual enclosures. Experimental meals consist of goldspot herring (Herklotsichthys qaudrimaculatus) equal to 1.2% of the sharks weight. Stomach contents were recovered by gastric eversion, and dried to constant weight. Fifty-six percent of the meal was digested in ten hours, and 73% in twenty hours. Water temperatures during the experiment ranged from 22.0 to 24.5 C.

Keywords: gastric evacuation, Sphyrna lewini
Carvalho, Marcelo*1,2, and Maisey, John G.3.

1. Department of Ichthyology, American Museum of Natural History, Central Park West at 79th Street, New York, New York, 10024 USA

2. Department of Biology, Graduate Center and City College of The City University of New York, New York, New York, 10036 USA

3. Department of Vertebrate Paleontology, American Museum of Natural History, Central Park West at 79th Street, New York, New York, 10024 USA

Phylogenetic relationships of the Upper Jurassic shark Protospinax Woodward, 1919 (Chondrichthyes, Elasmobranchii).

The phylogenetic relationships of Protospinax annectans, an Upper Jurassic shark from Solnhofen (Germany), has been subjected to much debate by numerous previous authors, with varying conclusions. Based on two additional specimens, the anatomy of this enigmatic fossil was further studied. Using recent cladistic analyses, the phylogenetic position of Protospinax is now corroborated to a greater extent. Protospinax is resolved as a very derived member of the Squalea, and is the sister-group to the Hypnosqualea (a group comprising squatinoids, pristiophoroids and batoids). 10 characters support this contention. Although our analyses varied with respect to included/excluded characters and weighting, Protospinax still remained the most basal hypnosqualean.

Key words: Protospinax, Squalea, Hypnosqualea, systematics.
Castro, Dr. Jose I.

Southeast Fisheries Science Center, NOAA/NMFS, 75 Virginia Beach Dr., Miami, Florida, 33149 USA

The biology of the blacktip shark, Carcharhinus limbatus, off the southeastern United States.

The blacktip shark is a cosmopolitan species found throughout tropical and subtropical waters. It is common along the southeast coast of the United States, where it migrates northward to Georgia and the Carolinas in summer and southward to Florida in winter. The blacktip shark feeds on small bony fishes, primarily menhaden, and small elasmobranchs. Males mature between 1425 and 1450 mm TL, and all males over 1450 mm TL are mature. Females mature at about 1560 mm TL. The reproductive cycle lasts two years and includes biennial ovulation with a one year gestation period. Mating and ovulation occur in Bulls Bay, South Carolina, from mid-May to early June. Parturition occurs the following year from early May to early June in the shallow coastal waters of the Carolinas. The blacktip shark is a viviparous, placental species. Implantation usually occurs during the 10th and 11th weeks of gestation when the embryos measure 178-194 mm TL. The young are born at about 550-600 mm TL during May and early June in the shallow water, coastal nurseries of Georgia and the Carolinas. The neonate stage lasts about a month. The young remain in the shallow water nurseries until fall.

Keywords: sharks, life history, reproduction, migrations, Carcharhinus limbatus.
Cowley, Paul D.

Department of Ichthyology and Fisheries Science, Rhodes University, P. O. Box 94, Grahamstown, 6140, South Africa

Age and growth of the blue stingray Dasyatis chrysonota chrysonota from the southeastern Cape coast of South Africa

The age and growth of Dasyatis chrysonota chrysonota from the southeast coast of South Africa was investigated by examination of bands on the vertebral centra. The annual nature of band deposition was verified by centrum edge characteristics and supported by gowth of known-age individuals kept in captivity. The derived von Bertalanffy parameters from age and length data were La= 532 mm DW, K = 0.175 and to = -3.65 for males and La= 913 mm DW, K = 0.070 and to = -4.48 for females. Growth of captive specimens showed distinct seasonal differences, with a mean monthly growth rate of 7.3 mm/month during the summer and 3.8 mm/month during the winter. The mean rate of growth in captivity for the first year after birth, calculated at 66.7 mm/year, is similar to the value obtained from back calculations (64.6 mm/year) but lower than the calculated value of 45.1 mm/year. The estimated age at first maturity is five years for males and seven years for females.

Keywords: Elasmobranch age and growth, growth in captivity validation, Dasyatis sp.
Crow, Gerald L.

Waikiki Aquarium, 2777 Kalakaua Ave., Honolulu, Hawaii, 96815 USA

The reproductive biology of the tiger shark Galeocerdo cuvier in Hawaii: A compilation of historical and contemporary data

The reproductive biology of the tiger shark Galeocerdo cuvier has never been fully documented. Reproductive data were gathered from 111 females and 106 males from the 1959-1960 and 1967-1969 shark control programs in Hawaii. Additional data from 11 females and 4 males were obtained from 1993-1994. Based on oviducal width, the smallest mature female was 282 cm TL and the largest immature was 303 cm TL. The smallest mature male was 292 cm TL and the largest immature was 323 cm TL, based on calcification of the claspers. Tiger sharks are aplacental and have a compartmentalized uterus with presumed matrotrophy. Based on mating scars, free flowing male "sperm", and a copulatory plug, copulation occurs primarily in January and February. Oviducal "sperm" storage occurs until ovulation in May-July. Embryonic uterine development starts almost immediately and gestation lasts 15-16 months. Pups are typically born at 80-90 cm TL in September and October. Excluding very near term females, tiger sharks in Hawaii average 41 pups (n=13). Based on "sperm" storage and the long gestation period, the females are thought to have a triennial reproductive cycle. The male reproductive cycle is unknown but may be annual. Keywords: Tiger shark, Galeocerdo cuvier, Reproductive cycle, Maturity
Demski, Leo S.*1, Beaver, Joel1, Sudberry, Jonathan1 and Luer, Carl A.2

1. Division of Natural Sciences, New College of the Univ. of South Florida, 5700 North Tamiami Trail, Sarasota Florida 34243 USA

2. Mote Marine Laboratory, 1600 Thompson Parkway, Sarasota Florida 34236 USA

Development of gonadotropin hormone releasing (GnRH)- immunoreactive systems in the terminal nerve and brain of the clearnosed skate, Raja eglanteria, with preliminary observations on terminal nerve regeneration.

Skates (7-32 weeks & adult) were obtained from Mote Marine Laboratory. The terminal nerve (TN) has bundles of GnRH- immunoreactive (ir) fibers that arise from ir-ganglia located on the olfactory bulb (OB) and distribute peripherally to the olfactory epithelium and OB and centrally into the ventral medial telencephalon. TN GnRH-ir was similar in all stages with the exception that diffuse fibers in the telencephalon, thought to be of TN origin, were scarce in younger stages. Numerous scattered GnRH-ir cells are located in the basal forebrain. In all stages, the largest group of GnRH-ir cells is in the midbrain near the midline below the ventricle. From 10 weeks, ir-fibers, most likely from TN and basal forebrain cells, extend throughout the forebrain with heavy projections into the septopreoptic area, basal hypothalamus and pituitary and ir-fibers, most likely from midbrain cells, project to most areas of the brainstem and spinal cord. Thus, while GnRH-ir cell groups are present at 7 & 8 weeks, it appears that fiber growth does not approach the adult condition until 10 to 16 weeks. In the younger stages, cutting the TN just proximal to its ganglia can result in axonal sprouting and reinnervation of the OB.

Keywords: reproduction, elasmobranch, batoid, nervous system
Ellis, Jim R. and Shackley, S. E.

Department of Marine Biology, School of Biological Sciences, University of Wales, Swansea, Singleton Park, Swansea, SA2 8PP, U.K.

Feeding ecology of Scyliorhinus canicula in the Bristol Channel The stomach contents of 731 specimens of Scyliorhinus canicula were examined and the diet assessed by the frequency of occurrence, by numbers and by the points method. Seasonal, geographical, sexual and sized -based differences in the diet were determined. The most common prey species were Pagurus bernhardus, Cancer pagurus, Carcinus maenas, Buccinum undatum, Ensis spp. and Ascidiella sp.. The most important factors in determining the diet appeared to be the geographical location, season and size.

Keywords: Scyliorhinus canicula, Scyliorhinidae, diet, Bristol Channel