Abstracts of AES Scientific Papers
|
American Elasmobranch Society 1999 Annual Meeting
State College, Pennsylvania
ABSTRACTS - Part 4: Rasmussen through Yano
*Rasmussen, L.E.L., Luer, Carl A., Manire,
Charles A.
(LR) Dept of Biochemistry & Molecular
Biology, Oregon Graduate Institute, Beaverton, OR 97006; (CAL, CAM) Mote Marine
Laboratory, Sarasota, FL 34236
Elasmobranch pheromones:hints from the
clearnose skate, Raja
eglanteria
The identified sex pheromones of
vertebrates include a somewhat random variety of chemical compounds; lampreys
utilize bile salts, while some teleost fishes employ steroid derivatives,
especially progestins, and prostaglandins. Snakes, salamanders, hamsters, pigs
and elephants utilize methyl ketones, a protein, a dimethyl disulfide protein
complex, a steroid and an acetate, respectively. Among the various compounds
employed by marine invertebrates, Aplysia utilizes a novel
peptide. Identification of elasmobranch pheromones has potential to provide
chemical, functional and evolutionary insight. Over a five-year period bioassays
were conducted with isolated male skates during their active reproductive
period. Three types of female-derived material (urine, ovarian extracts and
serum extracts from actively mating females) and selected steroidal hormone
derivatives were investigated. Significantly elevated male response was observed
to urine from ?hot" females, extracts of serum from females with elevated
testosterone and estradiol levels, and dichloromethane extracts of ovaries. The
results from assays of nine substituted estradiols and five progestins were
generally negative. There was some response observed to estradiol 17-sulfate and
less to estradiol 3-sulfate. Continued research will include a placental
viviparous species, the bonnethead shark, Sphyrna tiburo, and will focus on the
assay of protein extracts from female urine.
*Rechisky, Erin L., Wetherbee, Bradley M.
(ELR) Fisheries, Animal and Veterinary
Science, University of Rhode Island, Kingston, RI 02881; (BMW) NOAA/NMFS/NEFSC,
Narragansett, RI 02882
Short-term movements of juvenile sandbar
sharks, Carcharhinus plumbeus, in Delaware Bay using acoustic telemetry
Acoustic telemetry was used to investigate
short-term movements of neonate and juvenile sandbar sharks, Carcharhinus
plumbeus, on the shark nursery grounds in Delaware Bay during the summer of
1998. A total of 12 sharks was tracked continuously for between 6-70 hours. The
majority of the sharks caught and tracked in the southern region of the bay
remained in this area for the entire duration of the tracks. These sharks
predominantly limited their movements to within 3 km of shore and to water that
was approximately 2-5 m deep. Two sharks made longer offshore movements, one
into the deepest section of the bay (37 m), and the other crossed the bay from
Lewes, DE to Cape May, NJ. Tidal flow appears to affect the fine-scale movements
of these small sharks, however no diel patterns were observed for distance from
shore, rate of movement or depth. The results of this study indicate that young
sandbar sharks concentrate their movements within a restricted portion of the
bay, and therefore, area closures during the summer months might prove to be an
effective management technique for this species.
*Ritter, Erich K., Godknecht, Alexander J.
(EKR) Green Marine Institute, Miami, FL
33173; (AJG) Winterthurerstr, University of Zurich, Zurich 8057 Switzerland
Agonistic display in sharks with special
reference to the blacktip shark, Carcharhinus
limbatus
Some carcharhinid show aggressive behavior
patterns starting with forms of agonistic display. This display has been
described in detail for the gray reef shark, Carcharhinus amblyrhynchos .
Modified or less extensive forms of this display have been described for other
carcharhinid species as well. We will describe the agonistic display observed in
the blacktip shark, Carcharhinus limbatus, and discuss possible
origins of these patterns.
*Ritter, Erich K., Godknecht, Alexander J.
(EKR) Green Marine Institute, Miami, FL
33173; (AJG) Winterthurerstr, University of Zurich, Zurich 8057 Switzerland
Subordinate hierarchy between two closely
related shark species, Caribbean reef shark ( Carcharhinus perezi )
and blacktip shark ( C. limbatus )
Anecdotal evidence suggests that different
shark species exhibit interspecific subordinate hierarchies while feeding. Such
events have never been statistically examined. This paper describes subordinate
associations between two closely related carcharhinid species of similar size,
the Caribbean reef shark, Carcharhinus perezi, and the blacktip
shark, Carcharhinus limbatus, during a controlled setup. A
subordinate event was identified when a shark initiated a bite at the food
source but then first hit, bit or pushed another approaching shark away, before
taking the actual bite. After analyzing 610 biting acts, 35 interspecific
subordinate events were recorded between specimens of the two species.
Robinson, Michael P.
Department of Biology, University of
Miami, Coral Gables, FL 33124
The relationship between home range and
body size in several sharks.
The home range of an animal is an
important facet of its biology and can give insight into other aspects of its
lifestyle. Home range size is correlated with the energetic requirements of
terrestrial organisms. The home range areas of several shark species as reported
in the literature are discussed here and their relationship to shark size is
examined. The home ranges of several shark species (i.e. Heterodontus
fransisci, Sphyrna lewini, Carcharhinus amblyrhynchos )
did not regress significantly against animal size. Only the home range of the
lemon shark, Negaprion brevirostris showed a significant,
positive increase with the size of the individual. This increase was similar to
that of the increase in metabolic requirements with mass; the home range
increased at a greater rate than that predicted by both mammalian and
elasmobranch data. It is proposed that the lemon shark has a high metabolic rate
for elasmobranchs and thus requires a relatively larger area per mass from which
to acquire energy.
*Rojas, José Rodrigo, Camhi, Merry D.
(JRR) ProAmbiente, San Jose, Costa Rica; (MDC)
Living Oceans Program, National Audubon Society, Islip, NY 11751
Status of sharks and their fisheries in
Central America
Shark fisheries in Central America
represent an important source of labor for artisanal fishers as well as protein
for local populations. The demand for shark products, especially fins and
cartilage, has led to an expansion in fisheries and trade throughout the region.
Limited data on landings suggest that shark populations have been declining over
the past 10 years. Increased fishing effort, scant data on biological reference
points, and lack of management are key factors that negatively impact this
fishery. A project currently under way aims to gather basic information on
population status, nursery and fishery grounds, socioeconomics of the fishery,
and needed conservation measures. Twenty four commercially valuable species have
been identified including Carcharhinus falciformes and Nasolamia
velox (Guatemala), C. falciformis (Nicaragua, Costa
Rica), C. obscurus (El Salvador), and C. limbatus
(Panama). Commercial products include the meat, fin, oil, cartilage, and skin.
Shark fins are the most valuable product (e.g., dried caudal fins sell for to
$US 150 - 400 per kg in Costa Rica), which are exported to Hong Kong, Taiwan,
Japan, and the United States. Recommended management measures to improve the
long-term viability of these sharks and the sustainability of their fisheries
are discussed.
Rosenberger, Lisa J.
Department of Organismal Biology and
Anatomy, University of Chicago, Chicago, IL 60637
The Evolution of Batoid Locomotion
The recent integration of functional
morphology with phylogenetic data is creating a renaissance in our view of
functional evolution. A phylogenetic context provides the ability to distinguish
between patterns that arise from similar selective pressures or constraints
independently and patterns that only reflect a common ancestry. Comparative
methods using current higher level phylogenies for batoids (skates, stingrays,
etc.) will reveal the evolutionary patterns of locomotion within this unique and
diverse group of fishes by tracing morphology and kinematic behavior. Batoids
exhibit three locomotor modes related to their lifestyles including axial-based
locomotion (shark-like), undulation of the pectoral fins (waves propagated down
the fins), and oscillation of the pectoral fins (bird-like flapping). Some
species use a combination of at least two of these, like guitarfish in the
family Rhinobatidae which use both axial and pectoral fin undulation. Others,
such as the dasyatids, are able to modify their locomotor style from undulation
to oscillation at high velocities. The assumed evolutionary trend for these
locomotor types is axial (sawfish, electric rays, guitarfish) to undulation
(skates and stingrays) to oscillation (eagle and manta rays), however undulation
and oscillation may have independently evolved multiple times in these fishes.
*Ryburn, Julie A., Naylor, Gavin, Fedrigo,
Olivier, Lopez, Andres
Zoology and Genetics, Iowa State
University, Ames, IA 50011
The phylogenetic relationships of
carcharhinid shark: An inference based on both nuclear and mitochondrial genes.
The Carcharhinidae is one of the most
diverse families of sharks, as well as one of the most commercially important.
Our current understanding of carcharhinid phylogeny is based on the comparative
morphological studies by Compagno (1988) and allozyme studies by Lavery (1992)
and Naylor (1992). In the present study we present phylogenetic inferences based
on 6kb of sequence data comprising 3 mitochondrial genes and one nuclear gene
for 45 carcharhinid taxa.
*Sasko, Desirée, Motta, Philip
University of South Florida, Tampa, FL
33569
The prey capture behavior and kinematics
of the Atlantic cownose ray, Rhinoptera bonasus .
This study explores the feeding behavior
and mechanics of the myliobatid Atlantic cownose ray, Rhinoptera
bonasus . This species possesses a euhyostylic jaw suspension
permitting extensive ventral protrusion of the jaws. Inertial suction prey
capture during the preparatory phase is characterized by depression of the
subrostral lobes. The expansive phase begins with the closure of the spiracle,
followed by depression of the mandible and protrusion of the palatoquadrate and
nasal cartilages. Throughout the feeding sequence, the subrostral lobes are
fully depressed, forming a laterally enclosed chamber trapping the food. During
the compressive phase, the mandible is elevated toward the palatoquadrate and
nasal cartilages grasping the food. In the recovery phase, the jaws are brought
back to the resting position and the spiracle is reopened. Manipulation involves
repeated jaw open and closing movements such that the hard parts of the food are
winnowed from the edible portions and ejected from the mouth. Total prey-capture
duration is 240 ms. When excavating food from the sand, the ray repeatedly opens
and closes its mouth to fluidize the sand, and suspend the food, before using
suction to capture the food.
*Saville, Kenneth J., Lindley, Andrea M.,
Maries, Eleonora G., Carrier, Jeffrey C.
Biology Department, Albion College,
Albion, MI 49224
The use of PCR-RFLP and DNA sequence
analysis of major histocompatibility class II alpha genes for paternity testing
in the nurse shark, Ginglymostoma cirratum .
We have developed a DNA-based paternity
test with which to further our understanding of the mating behavior and
reproductive biology of the nurse shark. It is hoped that this paternity test
will allow us to determine if matings of female nurse sharks with multiple males
can lead to multiple paternity in a single brood of offspring. We have focused
our analysis on the major histocompatibility class II alpha (MHC II A) locus.
Others have shown that this locus is duplicated, and that each of the duplicated
loci is highly polymorphic(Kasahara et al.,1992, Eur. J. Immunol. 23:
2160-2165). We have used a PCR-RFLP strategy to determine the MHC class II A
genotypes of DNA amplified from frozen shark tissue of one small family
consisting of one mother and seven offspring. We were able to assign genotypes
to each member of this family, but there was no evidence for multiple paternity.
However, the sample size was too small to rule out this possibility. The
analysis of a second family consisting of one mother and 33 offspring is
underway, and the results of this analysis will be reported.
*Schulze, Margo, Lent, Rebecca ,
Brewster-Geisz, Karyl, Meyers, Stephen
Highly Migratory Species Division, F/SF1,
National Marine Fisheries Service, Silver Spring, MD 20910
The Highly Migratory Species Fishery
Management Plan
On October 21, 1998, the Highly Migratory
Species (HMS) Management Division of the National Marine Fisheries Service (NMFS)
announced the availability of the draft Fishery Management Plan (FMP) for
Atlantic highly migratory species, including Atlantic tunas, swordfish, and
sharks. The draft FMP addresses rebuilding of overfished stocks (western
Atlantic bluefin tuna, Atlantic bigeye tuna, Atlantic swordfish, and large
coastal sharks), managing healthy stocks at optimum yield levels, limited
access, essential fish habitat, economic and social impacts, safety at sea,
scientific data and research needs, and permitting and reporting requirements.
NMFS released the proposed rule to implement the provisions contained in the
draft HMS FMP on January 20, 1999, and is conducting numerous public hearings
throughout the Atlantic, Gulf of Mexico, and Caribbean coasts.
*Sedoruk, Sarah, Hopkins, Todd
(SS) Southampton College, Southampton
College of Long Island University, Southampton, NY 11968; (TH) Rookery Bay
National Research Resreve, Naples, FL 34113
Flushing Behavior of the Bluntnose
Stingray ( Dasyatis sayii )From the Southwest Gulf Coast of
Florida
This study was carried out to determine
whether method of approach influenced the flushing distance of bluntnose
stingrays. Juvenile bluntnose stingrays were captured, tagged with a small
float, and released at the site of capture. One hour after release each ray was
approached by a researcher and the flushing distance was recorded. Flushing
distance was a measure of the distance between the investigator and the ray at
the moment the ray "spooked". During the first part of the study each
ray was approached once by a researcher walking normally and once by a
researcher doing the "stingray shuffle". During the second part of
this study each ray was approached once by a barefoot researcher and once by a
researcher wearing booties. Statistical analysis showed that neither the
"stingray shuffle" nor booties influenced flushing distances. Short
flushing distances were observed in response to all methods of approach. While
the "stingray shuffle" did not increase the flushing distances
observed, it did have the benefit of reducing one's chances of stepping directly
on top of the ray and therefore one's chances of getting stung. The results did
show a significant difference in the flushing distances recorded between the
beginning and end of the study period.
*Shivji, Mahmood S., Rogers, Scott O.,
Stanhope, Michael J.
(MSS) Oceanographic Center, Nova
Southeastern University, Dania, FL 33004; (SOR) College of Environmental Science
and Forestry, State University of New York, Syracuse, NY 13210; (MJS) Biology
and Biochemistry, The Queen's University, Belfast, Northern Ireland BT9 7BL UK
Species-specific markers for PCR-based
identification of sharks
Since individual species of sharks respond
differently to exploitation, management of the shark fishery on a
species-specific basis is considered imperative for effective conservation and
sustainable harvesting of this resource. The morphological similarities of many
of the commercially harvested species, coupled with on-board processing methods
have made it very difficult to collect accurate, species-specific catch data. As
a result, many of the sharks landed are either incorrectly identified or
classified as "unidentified sharks" in fishery records. Moreover, the
widespread practice of shark finning in many parts of the world, and a
potentially expanded list of prohibited shark fishery species in US waters will
require the ability to identify sharks accurately from dried fins and other body
parts for legal forensic purposes. To this end we are exploring the development
of DNA sequence-based differences in sharks as markers for reliable species
identification. In the quest to develop a streamlined process, we investigating
the utility of multiplex PCR-based protocols for rapid identification of tissues
using nucleotide differences in the ribosomal internal transcribed spacer
regions. We report here on our progress to date in this endeavor.
Simpfendorfer, Colin A.
Mote Marine Laboratory, Center for Shark
Research, Sarasota, FL 34236
Demography of western Atlantic sawfishes:
Implications for conservation
Sawfish are a group of elasmobranchs that
have been heavily impacted by humans due to targeted fishing, entanglement in
fishing gear, and habitat modification. Four species are currently listed on the
World Conservation Unions Red List of Threatened Animals, two as critically
endangered. Two species occur in the western Atlantic: the small tooth sawfish ( Pristis
pectinata ) and the large tooth sawfish ( P. perotteti ).
There are limited biological and population data available. However, sufficient
exists to construct preliminary demographic models for both western Atlantic
species. A series of models were constructed to examine the sensitivity of
demographic results to uncertainties in the biological and population data. The
results of these models indicate that P. perotteti has an
intrinsic rates of population increase of between 0.04 and 0.07, while P.
pectinata has a rate between 0.08 and 0.13. These intrinsic rates of
increase result in estimates of population doubling time of 10 - 17 years for P.
perotteti and 5 -9 years for P. pectinata . The
implications of these results for conservation of sawfish populations are
discussed.
*Simpfendorfer, Colin A., Hall, Norman
WA Marine Research Labs, Fisheries Western
Australia, North Beach, Western Australia 6020 Australia
Stock assessment and risk analysis for the
whiskery shark ( Furgaleus macki ) in south-western Australia
The status of the whiskery shark
population in south-western Australia was assessed using an age and sex
structured model. The results from the best estimates of the model indicate that
fishing prior to 1975 had a limited impact on the population, with total biomass
estimated to be 97% of virgin and mature female biomass estimated to be 95% of
virgin. The best estimate of total biomass in 1998 was 38.8% of virgin (95%
confidence interval (CI) 22.7% to 47.2%) indicating that heavy commercial
fishing had resulted in a significant decrease in the population. The best
estimate of mature female biomass in 1998 was 23.0% of virgin (95% CI 13.4% to
36.4%), demonstrating that the impact of the fishery has been biased towards
mature animals. Sensitivity tests indicated that uncertainty in the catch and
effort data, or the way it was corrected, had the greatest effect on the biomass
estimates. Uncertainty in biological and gear parameters resulted in only small
changes in the biomass estimates. Risk analysis indicated that to have a greater
than 60% probability of achieving biomass targets set by the management body
would require annual catches to be reduced to less than 160 tonnes.
*Skjaeraasen , Jon Egil, Bergstad, Odd
Aksel
(JS) Norwegian University of Science and
Technology (NTNU), Trondheim, 7035 Norway; (OB) Flødevigen Marine Research,
Institute of Marine Research, His, N-4817 His Norway
Distribution and feeding of rays in the
northeastern North Sea and on the Norwegian Sea Slope
Spatial distribution and diet composition
of five ray species were analysed based on data from several research vessel
cruises in the period 1984-1996.
Three species were characteristic members
of the demersal fish communities of the northeastern North Sea and Skagerrak and
the warm upper continental slope waters of the eastern Norwegian Sea, i.e. Raja
radiata, R. lintea, and R. fyllae. Within the North Sea, the southern slope of
the Norwegian Deeps at the entrance to the Skagerrak had a particularly high
density of rays.
In the Norwegian Sea, two species, Raja
hyperborea and Bathyraja spinicauda, occurred near the slope front between the
Atlantic Watermass and the cold Norwegian Sea Deep-water. R. hyperborea was the
only ray inhabiting sub-zero temperature water beneath the front.
The gut contents of Raja hyperborea and
Bathyraja spinicauda were dominated by fish, also epipelagic species, suggesting
extensive scavenging. Also R. lintea had mainly consumed fish prey, but also
deep-water shrimps. R. fyllae was the more typical benthivore, feeding mainly on
polychaetes and benthic crustaceans. The diet of Raja radiata differed between
the slope and North Sea-Skagerrak areas. Along the slope euphausids were the
prominent prey, whereas in the North Sea, shrimp, polychaetes and, in the bigger
specimens, fish were significant.
*Smith, Mark, Correia, Joáó P.
Esplanada D. Carlos I, Oceanário de
Lisboa, Lisboa, 1998 Portugal
An update on elasmobranch landings in
Portugal: 1986-1998
Elasmobranch Portuguese landings from 1986
until 1998 were analysed. Landings were discriminated by species, port, year,
month and selling cost. All species totalled 77651 metric tonnes, where
Squaliformes and Hexanchiformes accounted for 46% of the total,
Charcharhiniformes and Lamniformes for 16% and Squatiniformes for 38%. A total
of 36 species (some only identified by genus) were officially landed during that
period of time. The most landed species were Raja spp. (36%
of the total landed between 1986 and 1998), Centrophorus granulosus
(11%), Centroscymnus coelolepis (10%), Scyliorhinus
spp. (10%), Centrophorus squamosus (8%), Prionace
glauca (7%), Dalatias licha (6%) and Mustelus
spp. (4%). Because landings are only available for a period of 13
years, it is hard to determine accurately whether there is an increasing or
decreasing trend. However, when looking at monthly values it is possible to
observe that some species show high and low variations within each year. All
species that showed landings greater than 250 metric tonnes and ports with
landings greater than 500 metric tonnes were analysed with detail. Some species
show a clear boom-and-crash pattern parallelled by an increase in value.
*Smith, Wade D., Bizzarro, Joseph J.,
Jones, Erin M., Neer, Julie A., Tyminski, John, Márquez-Farias, J. Fernando,
Cailliet, Gregor M., Hueter, Robert E.
(WDS, JJB, EMJ, JAN, GMC) Moss Landing
Marine Laboratories, Moss Landing, CA 95039; (JT, REHMote
Marine Laboratory, Sarasota, FL 34236; (JM) Instituto Nacional de la Pesca,
Sonora, Mexico
A preliminary assessment of the
elasmobranch fishery in the northern Gulf of California, Mexico
Mexican elasmobranch fisheries have
expanded to become the largest in the Americas (~30,000 MT/year), with much of
the yield taken from the Gulf of California (GOC). To improve the understanding,
conservation, and management of shark and ray resources in the GOC, a 2-year,
multi-institutional project involving Mexican and US scientists was initiated.
The extent and activity of fishing camps within the northern GOC and catch
information from these camps, including species composition, sex, weight, size,
and other pertinent biological information were determined during 1998 field
surveys. A total of 31 elasmobranch species were encountered. Fishing effort was
highly variable among seasons in both Baja California Norte (BCN) and Sonora.
Landings were highest in summer and fall. Batoids numerically dominated BCN
catches and were important constituents of the Sonoran fishery. Large sharks
(esp. Alopias pelagicus, Carcharhinus falciformis, and
C. limbatus )comprised a greater component of the catch in BCN
than Sonora. Small sharks, juveniles of larger species, and batoids dominated
landings in both locations. Females dominated the fall catch composition of Mustelus
sp. and Gymnura marmorata . These primary data represent an
important step toward documenting fishing trends that are critical for
sustainable fisheries management of elasmobranchs in the GOC.
*Tyminski, John P., Cortés, Enric, Manire,
Charles A., Hueter, Robert E.
(JPT, CAM, REH) Center for Shark Research,
Mote Marine Laboratory, Sarasota, FL 34236; (EC) Southeast Fisheries Science
Center, National Marine Fisheries Service, Panama City, FL 32408
Gastric Evacuation and Estimates of Daily
Ration in the Bonnethead Shark Sphyrna
tiburo
The rate of gastric evacuation is an
integral component in estimating daily ration in fishes caught in the wild. The
gastric evacuation curve for the bonnethead shark was established in a
laboratory study by force feeding a pre-weighed meal of the iridescent swim
crab, Portunus gibbesii . Stomach contents were removed by
everting the stomachs at selected times after feeding. These data were best fit
by both the exponential and Gompertz nonlinear models. Analysis of these
contents was used to develop a discrete stage-of-digestion scale that then was
applied to prey items from bonnethead stomach contents obtained in the wild.
This allowed reconstruction of meal size which, together with feeding frequency,
was used to estimate daily ration. As an alternative approach, stomach contents
were collected from bonnethead sharks in the field over a 24-hr period at 3-hr
intervals. Stomach content weight and stage of digestion were used to determine
daily ration with this method. Daily ration also was estimated through the
balanced energy equation. These and other methods of estimating daily ration
will be compared for their suitability given the assumptions implicit in each
method.
*Villavicencio-Garayzar, Carlos, Cailliet,
Gregor M.
(CV) Departamento de Biologia Marina,
Universidad Autonoma de Baja California Sur, La Paz, B.C.S, 23080 Mexico; (GMC)
San Jose State University, Moss Landing Marine Laboratories, Moss Landing, CA
95039
Age and Growth of the Pacific lesser
electric ray, Narcine entemedor, from the west coast of Baja California Sur,
Mexico
We describe the age and growth of the
Pacific lesser electric ray, Narcine entemedor, from artisanal fisheries in two
locations, Almejas Bay and San Ignacio Lagoon, along the western coast of Baja
California Sur, Mexico. We removed, cleaned and sectioned vertebrae for growth
zone analysis. We independently counted pairs of opaque and translucent bands
and calculated the average percent error (APE) and percent error (D) and
produced precision histograms that indicate precision of counts was relatively
good, with among-reader APE and D values for females being 10.38 and 6.10%,
while for males they were 8.25 and 4.71%, respectively. Most age estimates were
within 2 years of each other. Marginal increment measurements for large females
over 70 cm TL and males over 50 cm TL indicated seasonal changes, with an
increase in the dimension of opaque bands during the summer months. We fit the
von Bertalanffy growth (VBG) function to the data from 315 female and 79 male
rays, producing growth curves that indicated that females grew faster (k =
0.313) and reached a larger size (Loo = 82.4 cm TL) than males (Loo = 79.4 cm
TL; k = 0.094). The oldest female and male rays were estimated to be 15 and 11
years old, respectively. Growth characteristics, coupled with information on
reproduction, indicate that this ray could be susceptible to heavy fishing
pressure, especially in their nursery areas.
*Walker, Nancy B., Shivji, Mahmood S.,
Stanhope, Michael J., Rogers, Scott O.
(NBW, SOR) College of Environmental
Science and Forestry, State University of New York, Syracuse, NY 13210; (MSS)
Oceanographic Center, Nova Southeastern University, Dania, FL 33004; (MJS)
Biology and Biochemistry, The Queen's University, Belfast, Northern Ireland BT9
7BL UK
Characterization of group I intron-like
insertion elements in shark ribosomal DNA spacers.
A set of insertion elements has been found
in the ribosomal DNA (rDNA) internal transcribed spacers in four Orders of
sharks (Carcharhiniformes, Hexanchiformes, Lamniformes, and Orectolobiformes).
These elements are from 303 to 575 nucleotides in length, and show all the RNA
folding characteristics of group I introns, with each element having nine to
eleven pairing regions and a conserved core region. Each of these putative
introns has been cloned into RNA expression vectors and in vitro
splicing experiments are underway. If these elements are capable of in
vitro splicing, this will be the only group I intron within rDNA
reported for any metazoan. Also, this would be the only report of a group I
intron within a transcribed spacer region. If these elements are incapable of in
vitro splicing, they may represent remnants of a very ancient
insertional event by a group I intron ancestor. Aside from the biological and
evolutionary importance of these elements, their sequences vary greatly and so
have the potential for use as species-specific markers for shark identification.
*Walsh, Cathy J., Luer, Carl A., Wyffels,
Jennifer T., Bodine, A. B.
(CJW, CAL) Mote Marine Laboratory, Mote
Marine Laboratory, Sarasota, FL 34236; (JTW, ABB) Clemson University, Clemson,
SC 29634
Dexamethasone-induced apoptosis
(programmed cell death) in immune cells from peripheral circulation and
lymphomyeloid tissues of juvenile clearnose skates ( Raja eglanteria ).
Programmed cell death (apoptosis) plays a
critical role in shaping the immune repertoire in higher vertebrate thymi.
Elasmobranchs represent the earliest phylogenetic appearance of a clearly
defined thymus. Apoptosis was induced in juvenile clearnose skates by IM
injections of dexamethasone-21-phosphate in areas adjacent to the thymus at
levels of 50, 75, and 100 mg/kg body weight. After 24 h, skates were sacrificed,
and Leydig organ, spleen, and thymus were removed and frozen in liquid nitrogen.
Blood was drawn via cardiac puncture, and peripheral blood leukocytes (PBL)
isolated. A method to detect DNA strand breaks (TUNEL reaction) was used to
assess apoptotic activity in cryostat sections of tissue and cytospin
preparations of PBL, and transmission electron microscopy was utilized to
examine glutaraldehyde/paraformaldehyde fixed thymi. Results show that
dexamethasone treatment resulted in increased apoptotic activity in immune
tissues and PBL of juvenile clearnose skates. These studies demonstrate that
immune cells of elasmobranchs have the capacity for glucocorticoid-driven
apoptosis, and that mechanisms of programmed cell death appear to have been well
conserved during evolution. Knowledge gained from studies of these processes in
primitive vertebrates such as elasmobranchs should contribute to a better
understanding of the significance of apoptosis in higher vertebrates.
*Wyffels, Jennifer, Bodine, A. B., Wourms,
J. P., Luer, C. A., Walsh , C. J.
(JW, ABB) AVS Department, Clemson
University, Clemson, SC 29634; (JPW) Biological Sciences Department, Clemson
University, Clemson, SC 29634; (CAL, CJWMote Marine Laboratory, Sarasota, FL
34236
A series of developmental stages for the
clearnose skate, Raja
eglanteria
A series of developmental stages for the
clearnose skate, Raja eglanteria, based on external morphology has
been prepared. Images were collected with macrophotography, epifluorescent
microscopy, and scanning electron microscopy from more than 100 embryos. The
skates were maintained at 21 C and fixed with aldehydes at regular intervals
throughout their 12 week incubation period. Embryonic development was observed
from early cleavage to 1 week post-hatching. The embryos were staged based on
modifications of the staging systems of Ballard and Mellinger, 1993; Scammon,
1911; and Balfour, 1876. Newly laid eggs are in the blastoderm stage. The
embryonic axis of the skate is established 3 days after oviposition. Fusion of
the neural folds is complete 7 days after oviposition. Otic and optic vesicles
are apparent 10 days after oviposition. The olfactory pit is invaginated in day
12 embryos. Thirteen days after oviposition all pharyngeal grooves are open and
gill filaments protrude from the gill bars. Pectoral and pelvic fins attain
their definitive shape 17 days after oviposition. The stages established for the
clearnose skate will be useful for comparative and evolutionary studies of
vertebrate development.
*Yano, Kazunari, Ito, Takashi, Sato,
Fumihiko, Takahashi, Tomoko, Shimizu, Hirofumi
(KY) Ishigaki Tropical Station, Seikai
National Fisheries Research Institute, Okinawa, 907-0451 Japan; (TI), Marine
Service Ito, Okinawa, 907-1221 Japan; (FS) Byobudani, Chichijima, Ogasawara,
Ogasawara Marine Center, Tokyo, 100-2101 Japan; (TT) Miyanohama-michi,
Chichijima, Ogasawara, Sea-Tac Co., Tokyo, 100-2101 Japan; (HS) Seikai National
Fisheries Research Institute, Seikai National Fisheries Research Institute,
Ishigaki, Okinawa, 907-0451 Japan
Photo-identification of individual manta
rays, Manta birostris, at the Yaeyama Islands, the Miyako Islands,
and the Ogasawara Islands, Japan
The manta ray, Manta birostris
(family Mobulidae), is the largest ray and one of the largest living fishes,
reaching a disc width of at least 6.7 m and a weight of more than 1360 kg. The
manta ray occurs worldwide in tropical and subtropical regions, and occasionally
migrates into temperate waters. Individual mantas are recognizable on the basis
of natural marks and color patterns, especially dark markings on their abdomen.
In this study mantas were recorded by photographs and video tape recording
around several Japanese islands. We identified 180 individuals at the Yaeyama
Islands, Okinawa, from 1978 to 1998, 48 individuals at the Miyako Islands,
Okinawa, from 1996 to 1998, and 42 individuals at the Ogasawara Islands, Tokyo,
from 1995 to 1998. We observed that manta rays migrated between the Yaeyama
Islands and the Miyako Islands. The color patterns of manta rays differed
between the Yaeyama Islands/Miyako Islands populations and the Ogasawara Islands
population. Seasonal abundance, migration, and swimming behavior of manta rays
are reported.
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