2002 AES Annual Meeting Abstracts

Identifying bacteria and possible antibiotic resistance in shark populations: A preliminary assessment of potential human and shark health risks.

Bull sharks, Carcharhinus leucas, and nurse sharks, Ginglymostoma cirratum, are two shark species that are found in close association with humans. Divers near shallow reefs often encounter nurse sharks. Many times divers will interact with nurse sharks, resulting in bites. Bull sharks are known to be an aggressive species and often feed in the shallow beach environments where swimmers are attacked. Little is known about the composition of bacteria species associated with either shark species. Oral swabs were collected from populations of both species in the Gulf of Mexico and the Caribbean Sea to identify bacteria and determine possible health hazards that may be associated with infections from bites. In addition, cloacal swabs were collected to identify possible antibiotic-resistant species of bacteria that may be present in these sharks. No published literature is available on the possible implications of antibiotic resistance in sharks from the marine environment. Studies conducted on birds of prey in close proximity to humans show great potential for antibiotic resistance to natural and synthetic antibiotics. Results will be presented on data from Louisiana and Belize. The Louisiana populations represent sharks that are rarely in direct contact with swimmers, while the Belize populations are regularly in contact.

Elasmobranch science in Portugal: past, present and future.

An overview of studies involving elasmobranchs is given, including current trends for the future. Past studies mostly focused on systematics and commercial exploitation. Present studies are focusing on fisheries biology, movement patterns and greater efforts towards legislation and conservation of elasmobranchs as a sustainable resource. The immediate future will hold constant updates on fisheries biology models coupled with information on movement patterns via satellite tracking. Further studies of immunology and other biological fields will follow as well.

Case studies of elasmobranch husbandry at Oceanário de Lisboa.

Oceanário de Lisboa opened on the 22nd of May, 1998, with a large collection of elasmobranchs from both diverse geographical regions and having a wide range of ecological requirements. Such diversity translated into a number of problematic situations requiring some original solutions. Some of the more interesting case histories have been presented herein. Specifically: (1) the amputation of a broken (Rhinobatus typus rostrum; (2) non-rigid rostrum in (Himantura uarnak) and (H. undulata); (3) pre-copulatory behavior of Stegostoma fasciatum; (4) iodine deficiency and correction in Carcharhinus plumbeus; (5) Monogenea trematode infestation and eradication in Carcharhinus limbatus and C. melanopterus; (6) Stegostoma fasciatum and Aetobatus narinari sensitivity to organo-phosphates.

A stock assessment of small coastal sharks in the U.S. Atlantic and Gulf of Mexico.

The Atlantic sharpnose (Rhizoprionodon terraenovae), bonnethead (Sphyrna tiburo), blacknose (Carcharhinus acronotus), and finetooth (Carcharhinus isodon) sharks are small coastal species caught in directed fisheries and as bycatch in waters off the eastern U.S. coast. A new stock assessment of the small coastal shark (SCS) complex and individual species was conducted using new biological and fishery information that has become available in the last decade. CPUE series analyzed through Generalized Linear Mixed Models revealed fairly flat trends. Several stock assessment models were used to evaluate the status of small coastal sharks using Bayesian statistical techniques. A nonequilibrium Schaefer biomass dynamic model was used to describe the population dynamics of exploited SCS stocks using the SIR algorithm for numerical integration. A reparameterized, nonequilibrium Schaefer surplus production model using a Markov Chain Monte Carlo (MCMC) method for numerical integration was also applied. This state-space model accounts for both process and observation errors in a unified framework. Finally, a lagged recruitment, survival and growth (LRSG) state-space model was used to model the dynamics of SCS stocks. Results of the base-case and alternative scenarios indicate that the current level of removals is sustainable for the SCS aggregate and the individual species analyzed.

Feeding behavior and prey capture kinematics of the lesser electric ray Narcine brasiliensis, with comments on jaw protrusion mechanisms

The lesser electric ray Narcine brasiliensis is a suction-feeding batoid that preys primarily on polychaete annelids. Typical prey capture behavior involves raising the body-disc and simultaneously ventrally protruding the jaws with open, laterally occluded gape. Before maximum protrusion, the prey item is sucked into the buccal region through quick expansion of the branchial cavity. Ingestion of the prey is followed by pronounced retraction/flaring of the labial cartilages as the mouth is closed and the jaws return to resting position. Prey processing when present, involves repeated, often asymmetrical protrusion of the jaws while sand is expelled from spiracles, gills and mouth. Anatomically, this extreme jaw protrusion is similar to that described for the wobbegong Orectolobus maculatus. The medioventral swing of the stout hyomandibula is transmitted to the mandible. Through tight ligamentous and cartilaginous association between the lateral edges of the jaws, this motion results in medial compression of the entire jaw complex (i.e. shortening the distance between the right and left corners of the jaws), forming a more acute symphyseal angle. The euhyostylic jaw suspension of Narcine, however, allows a degree of ventral protrusion impossible for the Orectolobidae, creating great versatility and maneuverability for retrieving prey items from the benthos.

Comparison of the life histories and genetics of blacknose sharks (Carcharhinus acronotus) from the western North Atlantic and the Gulf of Mexico.

Blacknose sharks were collected from the coastal waters of South Carolina (113 male and 125 female) and the west coast of Florida (73 male and 48 female) to analyze their age, growth, and reproduction. There were significant differences between von Bertalanffy growth function parameter estimates for males and females in the western North Atlantic Ocean and the Gulf of Mexico. Based on the results of this study, male and female blacknose sharks from the Atlantic Ocean have lower growth constants and are longer lived than conspecifics in the Gulf of Mexico. Additionally, differences were found in the age/size at maturity and fecundity of blacknose sharks between the two regions. Differences between important life history parameters and genetic haplotype frequencies suggest that future management strategies should consider managing blacknose sharks off the coast of the southeastern United States as separate stocks.

Nearshore nursery use in the hammerhead shark, Sphyrna lewini.

Scalloped hammerhead shark pups (Sphyrna lewini) inhabit coastal nurseries where they act as apex predators and may seasonally dominate vertebrate biomass. Hypotheses of distribution, residency, growth, and survivorship of pups in nursery areas were tested by conducting mark-recapture and captive growth studies of S. lewini in Kaneohe Bay, Oahu, Hawaii. Shark pups were present throughout the year, with highest catch rates in late summer. There was little spatial segregation of pups in the bay and, while most recaptures occurred close to release, sharks dispersed up to 5 km after one week at liberty. This is contrary to previous suggestions that pups congregate in the south part of Kaneohe Bay. Most recaptures occurred within four months of tagging, but some sharks were at liberty for one year. Combined growth-rate data from recaptures and from captive sharks suggest that S. lewini pups grow very slowly in the months after birth. The presence of larger pups, the recapture of pups at liberty for a year, and the growth-rate of captive pups, suggest that coastal nurseries remain important hammerhead habitat throughout the first few years of life. This finding has fishery implications throughout tropical waters where S. lewini pups are heavily gill-netted.

Phylogeography of the sharpnose sharks, genus Rhizoprionodon.

The Sharpnose sharks, genus Rhizoprionodon, comprise seven coastal species with a circumtropical distribution in continental shelves. They include two Indian-Pacific species (R. oligolinx and R. taylori), one eastern Atlantic-Indian-Pacific species (R. acutus), and four American species, distributed in eastern Pacific (R. longurio) and western Atlantic (R. lalandei, R. porosus and R. terraenovae). In order to understand the most likely history of events that led to their present distribution, we obtained DNA sequence data from three mitochondrial genes, NADH-2, NADH-4, and cytochrome b, and one nuclear gene, RAG-1, totaling approximately 5000 bp for all seven species. Phylogenetic analysis suggests a basal position of the Indian Ocean species R. oligolinx. The other species were divided into two groups, one composed of R. acutus and R. taylori and another of the American species. Within this last group, the clade composed of western Atlantic species R. porosus and R. terraenovae is strongly supported in bootstrap analysis. In contrast, the relationship between eastern Pacific R. longurio and western Atlantic R. lalandei is unclear. In this study we propose a hypothesis of dispersion of the genus Rhizoprionodon that can best explain the extant species distribution, molecular phylogeny, and fossil record.

Financial support for VVF: CAPES, Brazil.

What’s happening to my body? Puberty in the male bonnethead shark, Sphyrna tiburo.

Puberty is defined as the period during which juveniles acquire the capacity to reproduce. Although considerable progress has been made in understanding this event in mammals, little is known about the physiology of puberty in lower vertebrates. In order to gain a better understanding of the physiological changes that occur during sexual maturation in elasmobranchs, this study investigated hormonal correlates of puberty in captive, maturing male bonnethead sharks, Sphyrna tiburo. Data from captive individuals are compared with that obtained from wild, maturing male S. tiburo in this first study of puberty in this ancient vertebrate group.

Homeothermy in adult salmon sharks, Lamna ditropis.

Salmon sharks, Lamna ditropis, occur in the boreal and cool temperate waters of the North Pacific Ocean. They belong to a small group of sharks that possess vascular counter-current heat exchangers (retia mirabilia) allowing retention of metabolically generated heat, resulting in elevated body temperatures. The capacity of free-swimming lamnid sharks to regulate rates of heat gain and loss has not been demonstrated. This is due to a several factors including their size, logistical difficulties, and the serendipity involved in obtaining field data that can serve as a surrogate for a laboratory experiment. Using acoustic telemetry, we found that free-swimming adult salmon sharks maintain a specific body temperature independent of changes in ambient temperature through a combination of physical and physiological means, and essentially function as homeotherms. Mean body temperature among individuals tracked ranged from 25.0 and 25.7º C. These sharks defended specific elevated temperatures regardless of changes in ambient temperature, which ranged from ~5 to 16º C. The maximum observed elevation of body temperature over ambient was 21.2º C. This unique ability is probably the underlying factor in the evolutionary niche expansion of salmon sharks into boreal waters and in their ability to actively pursue and capture highly active prey.

DNA microsatellites and multiple paternity in nurse shark (Ginglymostoma cirratum).

Recent studies indicate that multiple paternity of clutches occur in several sharks including nurse sharks. We used multiple DNA microsatellite loci to investigate multiple paternity in nurse shark by genotyping four clutches ranging in number from 6 to 39 pups. All four clutches exhibit more than two paternal alleles at multiple loci, demonstrating that multiple paternity is common in this species and serves to validate previous studies using RFLP. The number of male parents per clutch was estimated two ways: minimum estimates based on the number of paternal alleles and maximum likelihood estimates using microsatellite allele frequencies taken from presumably unrelated nurse sharks. Multilocus genoptypes were used to sort the pups into full-sib and half-sib groupings. The presence of multiple paternity in nurse sharks is not surprising considering previous field observations of free-living nurse sharks frequently encountered multiple males involved in courtship and mating activities with individual females. This project is part of an ongoing study of nurse shark reproductive ecology in the Dry Tortugas, Florida. The unrivaled access to all life stages of nurse sharks, including mating groups and neonates, coupled with the very limited lifetime home ranges of nurse sharks, make this species ideal for studies of reproductive ecology.

Age and growth in captive southern stingrays, Dasyatis americana.

Reproductive parameters have previously been determined for a captive, breeding population of southern stingrays, Dasyatis americana, at the National Aquarium in Baltimore. Offspring were tagged with passive integrated transponders (PIT) and growth was assessed over time. Growth for the first 7 years followed the von Bertalanffy growth model. Size at maturity for both sexes closely agrees with previously published values in wild conspecifics. Age at maturity was determined to be 3-4 years in males and 5-6 years in females in these captive-bred animals fed ad libitum and maintained at 24+º C.

Observation of philopatric behaviors in juvenile blacktip sharks.

Philopatry of juvenile blacktip sharks Carcharhinus limbatus to a nursery area on the Gulf coast of Florida was studied using passive acoustic monitoring. Monitoring equipment within the study site recorded the presence of individuals fitted with long-life (18 month) acoustic transmitters. Ninety-two sharks were fitted with transmitters between 1999-2001 to determine if one-year-old sharks return to their natal nursery in subsequent years. Monitoring began in 1999 and no sharks were found to return during 2000. However, in 2001 five individuals returned to the study site. Two individuals from the 1999 season (two years old) returned to the bay and were continuously resident within the study site until their transmitter battery expired (60 and 142 days). An additional three sharks from the 2000 season returned to the nursery as one-year-old animals and remained within the bay for varying periods of time (23-164 days). All five of these sharks were monitored for over 130 days during their original season of capture. Results of spatial utilization of returning animals will be compared to patterns for the same individuals for the previous monitoring period and neonate animals present at the same time.

The Atlantic sharpnose shark as a sentinel for marine zoonotic pathogens in coastal SC, U.S.A.

The ability of elasmobranchs to mount vigorous immune responses against marine bacteria remains uncharacterized. Developing antibodies against elasmobranch immunoglobulin M (IgM) is a first and critical step towards developing sensitive ELISA systems for quantitating specific (antibody) immune responses of sharks to marine pathogens. Serum samples from Rhizoprinodon terraenovae (Atlantic sharpnose) were mixed with a saturated ammonium sulfate solution overnight to precipitate IgM proteins. Precipitated IgM was partially purified using a PD-10 desalting column and extensive dialysis. Balb/c mice were used to develop-sharpnose IgM-specific antisera. The antisera was used to screen Mustelus canis (dogfish), Carcharhinus obscurus (black whaler) and Rhizoprinodon terraenovae (Atlantic sharpnose) serum samples by SDS-PAGE/immunoblotting techniques. The mouse antisera recognizes only sharpnose IgM. In addition, an ELISA system was developed for detection of bacterial pathogen-specific antibodies. Our results show that the Atlantic sharpnose is exposed to these pathogens and is able to produce pathogen-specific IgM. The specificity of these immunoglobulins allows us to detect exposure to different pathogens and allows us to analyze the health status of various sharpnose shark populations. Efforts to develop sharpnose IgM-specific monoclonal antibodies (mAb) are underway. These mAbs will be used to survey pathogen-specific antibody responses in sharpnose collected along the coast of SC.

Investigation of female philopatry and stock structure among blacktip shark nurseries using mitochondrial haplotypes and microsatellites.

Blacktip sharks Carcharhinus limbatus utilize continental nurseries along the U.S. Atlantic and Gulf of Mexico coasts. Although adult blacktips in this area are highly migratory, the degree to which females in these populations return to specific natal nurseries to give birth (natal philopatry) is currently unknown. Natal philopatry can lead to genetic differentiation among nurseries despite mixing of adults from different nursery areas during migrations. We investigated mitochondrial DNA and microsatellite heterogeneity among neonates collected from specific continental nurseries within the Gulf of Mexico and U.S. Atlantic coast. Nursery areas sampled included: South Carolina, three nurseries on the central Gulf coast of Florida, Gulf coast of Texas and the Mexican Yucatan. Preliminary mitochondrial results yielded a much larger degree of genetic differentiation than did microsatellites among nurseries along the Gulf and Atlantic coasts, perhaps due to female philopatry against a background of male-mediated gene flow. A smaller degree of genetic differentiation was observed among Florida nurseries, potentially indicating a greater degree of straying among these proximate nurseries.

Response properties of the stingray lateral line system: test of the mechanotactile hypothesis.

The elasmobranch lateral line includes an extensive cephalic non-pored canal subsystem hypothesized to serve a mechanotactile function for localization of prey during feeding. The mechanotactile hypothesis was tested in the stingray (Dasyatis sabina) by comparing the spontaneous activity, sensitivity and frequency response of primary afferent neurons from pored and non-pored lateral line canals. Ventral non-pored canals had a higher proportion of units with no resting discharge (33%) than did units from pored dorsal (3%) and ventral (12%) canals. Resting discharge activity of units from ventral pored and non-pored canals was similar, but lower than units from dorsal pored canals. Sensitivity of non-pored units to tactile stimulation was 2-70 times greater than to dipole water motion near the skin. Non-pored canals responded to skin depression velocities of ~74-1488mm/sec from 1-20Hz. Frequency response of afferents from pored canals was consistent with acceleration detectors at 20-30 Hz, whereas afferents from non-pored canals respond as velocity detectors at frequencies <10Hz. These low frequency properties match the mechanical stimuli produced by prey, and support the hypothesis that the stingray’s non-pored ventral lateral line functions as a tactile receptor subsystem used to guide small invertebrates to the ventrally positioned mouth. Supported by the AES Nelson Fund.

Gene regulation of xenobiotic metabolizing enzymes: Aryl hydrocarbon receptor diversity in elasmobranchs.

The toxic effects of halogenated aromatic hydrocarbons (dioxins, furans, non-ortho polychlorinated biphenyls) occur through the activation of the aryl hydrocarbon receptor (AHR), a member of the basic-loop-helix PER-ARNT-SIM family of transcription factors. Previous work in our laboratory has identified three distinct AHR genes among 5 species of elasmobranchs; AHR1 is the ortholog of the mammalian AHR and AHR1 in bony fish, AHR2 is orthologous to bony fish AHR2, and AHR3 forms a clade basal to that of AHR1 and AHR2. Of these genes, two were cloned from each shark species (Squalus acanthias, Somniosus microcephalus, Carcharhinus plumbeus, Mustelus canis) and one fromRaja erinacea. With the goal of determining if all three AHR paralogs exist in elasmobranchs, we isolated liver, testis and spleen mRNA from spiny dogfish Squalus acanthias (AHR1 and AHR3 were previously cloned from this species). Using reverse transcription and polymerase chain reaction with degenerate primers, we amplified the PAS domain of the AHR. Using restriction enzyme analysis we screened several clones from each tissue. The resulting patterns were consistent with that of AHR2 in other species. Subsequent sequencing of these clones resulted in the third distinct AHR gene in S. acanthias, AHR2. Phylogenetic and toxicological implications will be discussed.

Comparative population demography of elasmobranchs using life history tables, Leslie matrices, and stage-based matrix models

We compared results of demographic analyses of four species of elasmobranchs using life history tables, Leslie matrices, and several stage-based matrix models. Dasyatis violacea, with few age classes, was used to demonstrate the basics of Leslie-matrix and stage-based matrix model calculations. The demography for Carcharias taurus, with a 2-year reproductive cycle, produced higher potential population growth (lambda, r = ln lambda) using actual fertility rather than effective annual fertility. The demography for Alopias pelagicus, with continuous reproduction, produced higher lambda for a birth-flow than a birth-pulse population. The Carcharodon carcharias example demonstrated only a small difference in lambda between step-like and logistic fertility functions. Stage-based models with fixed-stage duration produced identical lambdas as those obtained from a life history table or Leslie matrix, but the net reproductive rates and generation times differed. Stage-based models with few stages had different dynamics with shorter recovery to the stable age distribution: they underestimated the elasticity of juvenile survival and overestimated the elasticity of adult survival suggesting cautious interpretation. We used elasticity analyses to estimate the number of juvenile age-classes that could be fished and have the same effect on potential population growth as fishing all the adult age-classes.

Characterization of the initial steps of steroidogenesis in the freshwater stingray (Potamotrygon hystrix).

The proper regulation of steroidogenesis is crucial to the maintenance of physiological homeostasis in all vertebrates. The initial steps of steroidogenesis are catalyzed by the steroidogenic acute regulatory protein (StAR) and cholesterol side chain cleavage (SCC). A freshwater stingray (Potamotrygon hystrix) interrenal gland cDNA library and degenerate primers were used to amplify cDNAs of StAR and SCC. PCR amplicons of the appropriate size were cloned and sequenced. Gene-specific primers used in RACE reactions yielded the entire open reading frame (ORF) of both StAR and SCC (encoding proteins of 284 and 526 amino acids, respectively). StAR and SCC clones were characterized by short 5′-untranslated and long 3′-untranslated regions. To confirm their identity, the ORFs encoding P. hystrix StAR and SCC were subcloned into the pCMV5 expression vector and expressed in cultured cells. StAR mRNA was detected in several P. hystrix tissues, while the expression of SCC had a more limited tissue distribution. The nucleic acid reagents isolated in this study will be used to examine the regulation of StAR and SCC genes in an effort to better define the physiological roles of interrenal steroids in elasmobranchs.

The nearshore elasmobranch fauna of the Southern California Bight.

From 1995 to present, the nearshore rocky-reef ichthyofauna of the Southern California Bight has been continually monitored by gill nets by the Ocean Resource Enhancement Hatchery Program (OREHP) for the California Department of Fish and Game. While the sampling program is designed to catch white seabass (Atractoscion nobilis), data from the bycatch indicates that elasmobranchs have a higher density and biomass in our nearshore environment than previously understood. We will discuss the spatial and temporal trends of the Galeorhinus zyopterus, Mustelus henlei, M. californicus, Triakis semifasciata (Carcharinidae),Gymnura marmorata (Dasyatidae), Heterodontus francisci (Heterodontidae), Myliobatis californica (Myliobatidae), Notorynchus cepedianus (Hexanchidae), Platyrhynoidis triseriata and Rhinobatis productus (Rhinobatidae), Cephaloscyllium ventriosum (Scylliorhinidae), Squalus acanthias (Squalidae), Squatina californica (Squatinidae), and Urolophus halleri (Urolophidae).

Genetic population structure of shortfin mako sharks (Isurus oxyrinchus).

Shortfin mako sharks are becoming increasingly important in both longline sports fisheries and as a target, not just a by-catch for commercial fishermen. As their numbers continue to be depleted, low reproductive rates decrease the probability of maintaining healthy stocks. Migration of individuals may function to replace depleted populations, but the degree of movement between bodies of water, and whether gene flow between populations occurs, remains unclear. This study assesses the genetic population structure of the shortfin mako (Isurus oxyrinchus) using DNA sequences of the mtDNA D-loop gene. Of interest is the inter- and intraoceanic movement of the sharks, while identifying areas of high genetic variability and gene flow.

Adventures of 01P0967: some lessons in using pop-up archival transmitting (PAT) tags on elasmobranchs.

In 1999 a single Wildlife Computers pop-up archival transmitting (PAT) tag was deployed on three separate species of elasmobranch. The tag was recovered twice and redeployed. The first deployment, on a bull shark (Carcharhinus leucas), lasted approximately five days. The tag was recovered a week later and returned by a recreational fishermen. The second deployment, on a blacktip shark (Carcharhinus limbatus), lasted approximately three days. Data from the tag suggest that the tag was initially removed after only a few hours by another animal that consumed the tag. The tag was recovered on a beach in the Florida Keys one month later, after it drifted at least 270 km. The third deployment, on a smalltooth sawfish (Pristis pectinata), lasted 51 days and was terminated when the tag “popped-up” as programmed on January 10th. Data from each of the deployments was analyzed to test the accuracy of the positioning algorithm of the PAT tag, and to help understand how best to utilize these tags to optimize their performance. In addition, the data from the sawfish deployment is being used to better understand the movement and migration patterns of this endangered species.

The first results of archival tagging of a basking shark, Cetorhinus maximus, in the western North Atlantic.

Little is known of the life history and ecology of the world’s second largest fish, the basking shark (Cetorhinus maximus). In the western North Atlantic, this federally protected species is known to congregate in New England waters from May through October each year. To initiate a study of the seasonal movements, behavior, and preferred habitat of the basking shark, a 6m female was tagged on September 27, 2001 with a pop-up satellite archival tag 73km east of Nantucket Island, Massachusetts. This animal belonged to an aggregation of approximately ten to twelve individuals swimming closely in a discrete area; none of the sharks was observed feeding. Although the tag was programmed to release in February 2002, the tag detached prematurely on December 6, 2001 in an area approximately 674km southwest of the tag site. The basking shark was vertically active for the entire tracking period, moving though depths and temperatures ranging from the surface to 320m and 5.8-21.0ºC, respectively. Over the 71 days, the shark displayed temporal variation in depth preference, with shallow behavior (<25m) more pronounced in late September, early October, and late November. Despite the wide range of water temperatures encountered, the behavior of the basking shark displayed a strong temperature preference, with 72% of the temperature observations in the narrow range of 15.0-17.5ºC. Although preliminary, this track provides evidence that the basking shark remains active and does not enter a hibernative state during the autumn months.

Taxonomic validity of Gymnura crebripunctata (Peters 1869) and Gymnura marmorata (Cooper 1863): a meristic, morphometric, and molecular approach.

Recent artisanal elasmobranch fishery surveys in the Gulf of California and Pacific coast of Mexico have indicated that batoids are a much moreimportant component of landings than previously estimated. Two butterflyrays, Gymnura crebripunctata and G. marmorata, are recognized in the Mexican Pacific and are among the primary elasmobranchs observed in these landings. The validity of these species was first questioned in 1928, but evidence supporting synonymy has been inconclusive. However, the primary characteristics used to distinguish the species (inter-orbital width and pre-orbital length) are known to be sexually dimorphic features in Gymnura micrura. To determine if G. crebripunctata and G. marmorata are valid species or male and female morphs of the same species, multiple analytical techniques have been applied. Heart and white muscle tissues were collected from fishery-derived specimens in the states of Sonora and Baja California Sur, Mexico. Similarity of the two species was examined through direct sequence comparison and phylogenetic analyses of approximately 445 base pairs of the mitochondrial cytochorme b locus, including other congeners as outgroups. Measurements, vertebral and spiral valve counts were obtained from and and compared to field and museum specimens. We report here on the preliminary results from these analyses.

An interesting tendon from a flat shark, with implications for the evolution of tendon.

Tendon is a dense connective tissue that is usually loaded in tension. Under certain circumstances, when passing around a bony prominence for example, tendon is also subjected to compressive forces. Mammalian tendon responds to this loading regime by developing a fibrocartilaginous pad that “cushions” the linearly arrayed tendon fibers. In the jaws of myliobatid stingrays that eat hard prey we have found a tendon that also has this response to compressive load. The fibrocartilaginous pad is morphologically similar to that seen in mammals, and histological sections have similar staining. Biochemical analysis reveals both similarities and differences, though there is strong concordance. We conclude that the physiological response to compressive loading evolved very early in the history of tendon and may predate the bony endoskeleton. We also will present data from hagfish linear tendon showing that the stiffness and strength of tendon arose with the craniates and is little changed in vertebrate taxa.

Bioactive compounds from bonnethead shark Sphyrna tiburo epigonal cells: Inhibitory activity against tumor cell lines.

Previous work in our laboratory has established conditions for maintenance of elasmobranch immune cells in short term culture. Assays for immune regulatory factors in conditioned media (CM) from cultures of bonnethead shark Sphyrna tiburo epigonal cells have demonstrated potent inhibitory activity against three mammalian tumor cell lines (malignant melanoma, A375.S2; fibrosarcoma, WEHI 164; Burkitt’s lymphoma, Daudi). Activity is lost after heating at 75 C for 30 min, and can be destroyed by some proteolytic enzymes (proteinase K, pronase) but not by others (trypsin, chymotrypsin). Separation of protein components using SDS-PAGE results in a reproducible pattern of three major bands with approximate molecular sizes of 43, 24, and 17 kD. Under non-denaturing conditions, CM appears to contain relatively large protein molecules or multimolecular complexes or aggregates. Nucleic acids in the CM might be responsible for aggregation of CM proteins, but are not required for inhibitory activity. Flow cytometric analyses of cell membrane changes (Annexin-V binding) and DNA fragmentation (TUNEL assay) indicate that CM inhibitors act through the induction of apoptosis in proliferating cells. Immunoblot detection of components of the TRAIL pathway suggests activation of the caspase cascade via the mitochondria as the probable route leading to apoptosis.

Diel movement behavior of the tiger shark, Galeocerdo cuvier, at the Miyako Islands, Japan using ultrasonic telemetry.

The swimming behavior of tiger sharks, Galeocerdo cuvier, was studied using ultrasonic telemetry around the Miyako Islands of the southern Ryukyu Islands, Japan. The tiger sharks (2.0-3.8 m in total length) were captured using shark longlines. Two-channel transmitters with depth and swimming-speed sensors (Vemco Model, V32SP, 34kHa) were attached to three sharks and one one-channel transmitter with a depth sensor (Vemco Model, V22P, 34kHz) was attached to one shark at the base of their first dorsal fin using a small, anchor-like device (1 cm in length) harpooned into the sharks. The sharks were tracked during July and August 2002. Tracking periods were 53 hours 15 minutes for No. 1, 7 hours 30 minutes for No. 2, 20 hours 31 minutes for No. 3, and 24 hours 21 minutes for No. 4, respectively. Swimming speeds calculated via the speed sensors of the transmitters were from 0.4 km/h to 21.2 km/h. The sharks actively swam during the day and night and their movements ranged widely around the Miyako Islands. The depth of the sharks extended from the surface down to 300 m. The range of swimming depths during the night was deeper and wider than during the day.