Abstracts of AES Scientific Papers
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American Elasmobranch Society 1999 Annual Meeting
State College, Pennsylvania
ABSTRACTS - Part 1: Acher through Fluharty
Acher, Roger
Lab Biological Chemistry, University of
Paris VI, Paris, 75006 France
Organismal versus molecular evolution.
Insights into Chondrichthyes.
The main theories of evolution, Lamarckim
(adaptation) and Darwinism (natural selection), were conceived during the XIXth
century from studies made at the organismal level. At present, deciphering of
complete genomes and proteomes leads to a definition of the species in molecular
terms. Molecular phylogenetic trees, constructed on the percentages of
substitutions in nucleic acid and protein sequences, are confronted to
morphological trees derived from taxonomy. However, the substitution rates
greatly vary from a protein to another and, in a given protein, from a domain to
another. Protein shapes, determined by aminoacid sequences through self-folding,
evolve following rules different from those governing body evolutions. Molecular
clocks are usually not in agreement with divergence times between lineages
estimated through fossil records. Furthermore new evolutionary mechanisms, such
as genetic drift (neutral evolution), genomic drive, horizontal gene transfer,
have been hypothesized. Evolution of Chondrichthyes differ sharply from that of
bony vertebrates by several specific features (skeleton, osmoregulatory
strategy, reproduction). The osmoregulatory system implies four organs: gut,
kidney, gills and rectal gland. Regulation of nephron cells involves a cascade
of molecule interactions : mediators, receptors, transductors and effectors. A
great diversity is found in neurohypophysial hormones when compared to those of
bony vertebrates, whereas, among effectors, Squalus acanthias urea
transporter and CFTR-chloride channels exhibit, respectively, 61% and 72%
sequence identity with their human counterparts. Evolution of the osmoregulatory
function was apparently made more by changes in the combinatorial coordination
of effectors in target cells rather than modifications in the molecules
themselves.
*Amesbury, Elena, Buhi, William C.,
Craine, D. Andrew, Guillette, Jr., L. J., Evans, David H.
(EA, LJG) Department of Zoology,
University of Florida, Gainesville, FL 32611; (WCB) Department of Obstetrics and
Gynecology, University of Florida, College of Medicine, Gainesville, FL 32610; (DAC)
Department of Biology, Maryville College, Maryville, TN 37804; (DHE) Department
of Zoology; University of Florida, Gainesville, FL 32611
Uterine fluid and serum protein
composition and serum steroid hormone concentrations during gestation in the
aplacental viviparous Atlantic stingray, Dasyatis sabina
The Atlantic stingray, Dasyatis
sabina, is an aplacental viviparous elasmobranch. Embryos have an external
yolk sac which is quickly depleted within the first few weeks of a 12-14 week
gestation. Uterine fluid is produced shortly after ovulation, and continues to
be produced until parturition. We test the hypothesis that this fluid contains
unique proteins that are synthesized and secreted by the uterus, and that the
changing protein composition is correlated with varying serum steroid hormone
concentrations. To test this hypothesis, blood and uterine fluid samples were
collected from rays during the annual reproductive cycle. Uterine fluid and
serum proteins were characterized by isoelectric point (pI) and molecular weight
using two dimensional gel electrophoresis. Uterine fluid from early through late
gestation contained a series of basic (pI 7-8) and acidic (pI 4-5) proteins
ranging from 30-220 k molecular weight. A large acidic protein (pI 5) first
appeared in mid-gestation uterine fluid, and was present through late-gestation.
Serum 17-ß estradiol concentrations significantly increased from 426 +/- 78 pg/ml
early gestation to 8293 +/- 2165 pg/ml mid-gestation, and remained elevated
through late gestation. Serum testosterone concentrations increased from 78 +/-
8 pg/ml during early gestation to 279 +/- 19 pg/ml during mid-gestation.
*Amesbury, Elena, Wyffels, Jennifer,
Wourms, John P., Snelson, Jr., Franklin F., Bodine , A. B.
(EA) Department of Zoology, University of
Florida, Gainesville, FL 32611; (JW) AVS Department, Clemson University, Clemson,
SC 29634; (JPW) Department of Biological Science, Clemson University, Clemson,
SC 29634; (FFS) Department of Biology, University of Central Florida, Orlando,
FL 32816; (ABB) AVS Department, Clemson University, Clemson, SC 29634
Morphology of the uterus during the annual
reproductive cycle of the aplacental viviparous Atlantic stingray, Dasyatis
sabina
The Atlantic stingray, Dasyatis
sabina, is an aplacental viviparous elasmobranch that reproduces annually.
In our study population, ovulation occurred in April, and gestation lasted
approximately 14 weeks. Villous extensions of the uterine mucosa line the inner
wall and are present throughout the year. Prior to ovulation, during the final
stages of oogenesis, the uterus was aglandular. Villus length averaged 3.7 +/-
0.7 mm. The uterine morphology transformed dramatically during gestation.
Uterine villi were differentiated when encapsulated embryos were developing in
the uterus. Shallow tubular glands were present in villi, and deep tubular
glands were present in the uterine mucosal lining. Uteri containing
unencapsulated, early gestation stage embryos were completely glandular. The
uterus was fully glandular through mid- and late gestation. Villi length
significantly increased to 6.9 +/- 0.6 mm during early gestation, and length
remained similar through mid- and late gestation. Vascularization increased and
capillaries hypertrophied during early and mid-gestation. Lipid droplets
accumulated within glandular pits mid- and late gestation. The uterine mucosa
and villi were aglandular in the post-partum uterus, and villus length
significantly decreased to 5.2 +/- 0.6 mm.
Amorim, Alberto F., Arfelli, Carlos A., *Castro,
José I.
(AFA, CAA) Av. Bartolomeu de Gusmao,
Instituto de Pesca, Santos, Bahia 11030-906 Brazil; (JIC) Southeast Fisheries
Science Center, NOAA/NMFS, Miami, FL 33149 USA
A juvenile megamouth shark Megachasma
pelagios caught off southern Brazil.
The megamouth shark Megachasma
pelagios is one of the rarest elasmobranchs. Since the capture of the first
megamouth known to science in 1976, only about thirteen specimens have been
reported, and only four have been available for scientific study. A juvenile
megamouth shark was accidentally caught by the Brazilian longline vessel Tooshin
Maru 106 off southern Brazil (27o 08'S 43o 55' W) on September 18, 1995. The
specimen was hooked in the mouth at depth of 15-40 m over water approximately
1400 m deep. The specimen was recognized as unusual and donated to the Instituto
de Pesca in Santos, Brazil. This is the first juvenile megamouth seen and
studied by scientists. The specimen is an immature male 1800 mm TL (1448mm FL),
weighing 24.4 kg. Morphologically, this specimen is very similar to other
megamouth sharks described from the Pacific. The body is soft and flaccid, with
poor vertebral calcification. The claspers are small and poorly developed, and
the specimen is clearly a juvenile. The specimen is clearly countershaded, being
black and brown above and white below. This specimen confirms the presence of
megamouth in the Atlantic.
*Aubrey, Craig W., Snelson, F. F.
University of Central Florida, Orlando, FL
32816
Sharks of the inshore waters of the
Canaveral Bight, Florida with emphasis on the spinner shark, Carcharhinus
brevipinna
Between September, 1995 and October, 1998,
the sharks of the Canaveral Bight, Florida were qualitatively sampled during the
summers between the beach and approximately 10 m depth. Preliminary observations
indicated that the inshore waters in this area were being used as a nursery area
by the spinner shark, Carcharhinus brevipinna. The objective of this
study was to ascertain if spinner sharks are using these waters as a nursery
area, and if so, to better understand C. brevipinna life history
parameters. Sharks were captured via hook and line from either a 5.9 m outboard
boat or the Ocean Obsession II, a 21.4 m charter boat providing nightly shark
fishing trips between May and October. Four hundred eighty-nine sharks
representing three families and seven species were captured during the study.
The Atlantic sharpnose shark, Rhizoprionodon terraenovae, and the
spinner shark were the most common species captured and appear to use these
waters as a nursery area throughout the summer months. Spinners began arriving
in June and were common into September and October. There was no difference in
fork length (FL) between males and females. The 1997 spinners were larger those
observed in 1998. Spinner pups grew about 10 cm FL during the summers of both
1997 and 1998. The lack of adult female spinner sharks and the failure to
observe any young of the year spinner sharks with fresh umbilical remains lends
support to Castro's (1993) statement that spinners appear to undergo parturition
in deeper waters. Young of the year blacktip sharks, Carcharhinus limbatus,
were observed but not in sufficient quantities to indicate that blacktips are
selecting the inshore waters of the Canaveral Bight as a nursery area. A number
of 1+ yr. juvenile C. brevipinna and C.limbatus
sharks were captured in May and June of 1998.
*Bergman, Ulrika, Connett, Stephen,
Simpfendorfer, Colin, Hueter, Robert
(UB) Stockholm University, Vastervik,
Sweden 59340 Sweden; (SC) St. George's School, Newport, RI 02840; (CS, RH)
Center for Shark Research, Mote Marine Laboratory, Sarasota, FL 34236
A remarkably consistent
fishery-independent measure of the relative abundance of large coastal and
pelagic shark species inhabiting the northwestern Atlantic, 1976-1994.
The research vessel Geronimo,
owned and operated by St. George's School of Newport, Rhode Island, instituted a
shark-tagging program in 1976 in collaboration with Jack Casey of the National
Marine Fisheries Service Laboratory in Narragansett. The boat's longline gear,
method of operation, and fishing area remained remarkably consistent through
1994, although annual fishing effort waned after the mid-1980's. The consistency
of operation provides a continuous index of CPUE for sandbar Carcharhinus
plumbeus, blue Prionace glauca, and other large coastal and pelagic
species inhabiting New England shelf and canyon waters. In this region from 1976
to 1994, Geronimo's crew set a total of 37,631 hooks consistently deploying
about 80 to 140 hooks per set, resulting in a total catch of 5,454 sharks.
Reductions in CPUE over the nearly twenty-year period indicate the abundance of
sandbar and blue sharks declined substantially during the 1980's, declines which
match those from other studies. There was no apparent decline in average length
of either sandbar or blue sharks caught during the period. Sex ratios in the
catch of blue sharks show an approximately four-year cycle that may be
indicative of segregated migratory habits of females vs. males.
*Bourdon, James A., Mollet, Henry F.
(JAB) New Jersey Paleontological Society,
Croton-on-Hudson, NY 10520; (HFM) 886 Cannery Row, Monterey Bay Aquarium,
Monterey, CA 93940
The dentition of the pelagic stingray Dasyatis
violacea, its design and function. In both sexes, the pelagic stingray
dentition combines high-cusped anterior files with broadly cuspidate teeth in
posterior positions. The transverse ridges of these posterior teeth create a
cutting edge. This is unlike the typical clutching-crushing design associated
with most members of the genus. Based upon tooth and dentition design, and
feeding observations at the Monterey Bay Aquarium, there appears to be
sufficient evidence to characterize this as a deboning dentition.
Carvalho, Marcelo
Department of Ichthyology, American Museum
of Natural History, New York, NY 10024
A systematic revision of the electric ray
genus Narcine Henle, 1834 (Chondrichthyes:
Torpediniformes: Narcinidae).
The electric ray genus Narcine Henle,
1834 is revised and found to be more diverse than previously understood. Some 20
species are recognized from tropical and sub-temperate waters from all major
oceans and seas of the world (except the eastern Atlantic Ocean and
Mediterranean Sea), and new species are described. Species of Narcine
occur primarily in shallow to off-shore waters of continental shelf regions, but
some species are known from upper continental slope areas as well. The Indo-West
Pacific region is the most speciose but one of the most undersampled areas in
which species of Narcine are known to occur. Many nominal
species are placed in synonymy, some for the first time. A combination of
proportional measurements, numerous counts and external and internal morphology
were used to identify all valid species of Narcine . Difficulties
surrounding taxonomic revisions of electric rays include the poor state of many
specimens in preservative (including type-specimens), the misidentification of
many nominal species by previous authors, and the great similarity among many
species. Taxonomic revisions of the remaining electric ray genera are currently
underway or have been completed.
*Castro, Andrey, Rosa, Ricardo S.
Lab. de Ictiologia, Depto de Sistematica
é ecologia, Universidade Federal da Paraíba, João Pessoa - PB, Paraíba
58059-900 Brazil
A Preliminary investigation of spatial
distribution of Nurse shark at Atol das Rocas, Brazil.
The nurse shark Ginglymostoma cirratum,
although widely distributed along the Brazilian coast, faces possible localized
population declines, especially due to artisanal fishery impact. The goal of
this study is to investigate some populational aspects of this species, and its
distribution in the Biological Reserve of Atol das Rocas, only atol of South
Atlantic. We carried out underwater observations at different parts of the area,
recognizing the individuals through natural distinctive marks, like scars on
their fins. A total of 92 nurse sharks was observed, of which 29 were
individually identified. Most specimens (57 %) were found in tide pools. The
maximum observed period of individual permanence in the pools was 22 days; three
individuals moved among different pools in intervals of five days or less. Total
length of the individuals varied from 45 to 350 cm, and average length in open
areas of reserve was significantly higher than the one of specimens from closed
areas (t=2.3918, p<0.05). Most specimens were young and their total length
did not exceed 150 cm, rendering sex determination difficult. Mature specimens
were only observed in open areas (TL>235 cm).
Castro, José I.
Southeast Fisheries Science Center, NOAA/NMFS,
Miami, FL 33149
Myths and misinformation about the nurse
shark, Ginglymostoma cirratum .
Although the nurse shark is an extremely
common shallow-water species, abundant in Florida and the Caribbean, its biology
is poorly known, and there are numerous myths and a great deal of misinformation
about it in the literature. Although its name has been attributed to the making
a "sucking sound" while feeding, it is actually derived from the name
"huss", an ancient English name for a dogfish. The size and weight
attained by the nurse shark has often been exaggerated, with claims of specimens
2130-3350 mm TL being common. None of the specimens measured in this study
exceeded 2680 mm TL and 110 kg. None of the specimens actually measured by other
researchers ever exceeded 2800 mm TL. The size at maturity is also often stated
erroneously at about 1500 mm TL. Nurse shark females begin to develop sexually
at about 2200 mm TL. In late spring, maturing females measuring 2360-2380 mm TL
carried ripe oocytes 55-58 mm in diameter. Mating occurs primarily from mid-June
to early July. The reproductive cycle of the nurse shark encompasses a five to
six-month gestation cycle and a two-year ovarian cycle. A female will mate and
ovulate in June of the first year. It then gestates for about five and a half
months and gives birth in November or early December of that year. It will not
mate again until about eighteen months later, in June of the second year. Thus,
the reproductive cycle is biennial and a female produces a brood or litter every
two years. The adult population of females could be divided into two groups
during most of the year based on whether they were reproducing that year
(carrying ripe oocytes or embryos) or they were post-partum.
*Chen, Che-Tsung, Chen, Sen-Lu, Cheng, I-Jiunn
National Taiwan Ocean University, Keelung
202, Taiwan R.O.C.
Temporal Variation of Heavy Metal
Concentrations of Galeus sauteri (Carcharhiniformes:
Scyliorhinidae) in the Northeastern Waters of Taiwan
This study is to determine the
concentrations of Hg, Zn , Cu , Ni , Pb and Cd in Galeus sauteri in the waters
off northeastern Taiwan by flameless and flame atomic absorption
spectrophotometry. The concentration of Zn was found to be abundant in vertebrae
(72.29ºg.g-1 dry.wt.) and stomach (71.85ºg.g-1
dry wt.) samples and was the lowest in muscle samples (17.00ºg.g-1 dry
wt.). The concentration of Cu was associated with stomach samples (9.23ºg.g-1 dry
wt.) and the highest concentrations of Cd was found in liver (0.99ºg.g-1
dry wt.) and kidney (1.13ºg.g-1 dry wt.) samples. The
concentrations of Pb (ˇ0.02ºg.g-1 dry wt.) and Ni (ˇ0.01ºg.g-1
dry wt.) were not detectable and that of Hg was found abundant in liver (293.60
ng.g -1 wet wt.) and muscle (871.42 ng.g-1 wet
wt.) samples. The Zn ranked the first place in concentration series of G.
sauteri and followed by Cu. There was no significant difference on heavy metal
levels between males and females except that of Zn in gonad and Cu in kidney.
The concentrations of Zn and Cu in liver and vertebrae have significantly
temporal variation. There was no significantly temporal variation on Cd and Hg
which were not essential elements. Hence, concentrations of Cd and Hg could be
resulted from biomagnification and long-term accumulation. There was an
exponential positive relationship between the length of adult G.sauteri and
Hg concentration in the muscle.The concentration of Hg in elesmobranchs was
higher than that in teleosts, but no significant difference on the
concentrations of Zn was found between G. Sauteri and
teleosts.
*Chiaramonte, Gustavo E., Tamini, Leandro
L., Perez, Jorge E., Cappozzo, H. Luis
Museo Argentino de Ciencias Naturales,
Estacióñ Hidrobiológica de Puerto Quequén (EHPQ), Buenos Aires 1405
Argentina
Preliminary study of discard composition
of Batoids in a bottom trawl fishery at Puerto Quequéñ, Buenos Aires,
Argentina.
From the 439 coastal vessels working in
Argentina, 25 are at Puerto Quequéñ(38o 37' S, 58o
50' W). Bottom trawl (BT), in multispecific fishery, is the most common kind of
gear used and the fishing discard is composed by invertebrates, elasmobranchs
and finfishes. This work describes the by-catch composition of batoids in BT at
Puerto Quequéñ, studied during 1998 winter-spring seasons by on board observed
in 24 gear operations. Eleven batoid species were recognized and 599 specimens
were weighted and measured disc width. The commercial species were Raja
castelnaui, R. flavirostris and R. cyclophora
. Vessels worked in the same fishing area during winter and spring and
each gear operation spent 2.2 Ò 0.3 hours. Batoids was 56 % of the total catch
with an average of 220.13 Ò 156.80 kg per operation (83.6 Ò 60.5 kg of
commercial biomass) in winter and 309.22 Ò 201.99 kg (56.9 Ò 39.1 kg) in
spring. Batoids was 57.2% of the discard in winter and 72% in spring. Electric
ray, Discopyge stchudii, was 78,5% of the race captured (sex ratio
1:0.9; mature males and females 87 and 90%) and all the individuals were
discarded . For the electric ray populations and other diferent taxa, BT fishery
impact might by important and its effect on benthonic communities has not been
measured yet.
*Correia, Joáo, Figueiredo, Ivone, Silva,
Alexandre
(JC) Esplanada D. Carlos I, Oceanário de
Lisboa, Lisboa, 1998 Portugal; (IF) Av. Brasília, DRM, IPIMAR, Lisboa, 1400
Portugal; (AS), DOP, Universidade dos Açores, Horta, 9900 Portugal
Age and growth of Blackmouth Catsharks, Galeus
melastomus, from Portuguese waters
1301 vertebrae were extracted from
Blackmouth catsharks fished off the Portuguese Continental slope during five
surveys held by the IPIMAR in 1994 and 1995. The vertebrae were prepared and
observed following a protocol established earlier by the same authors. A growth
curve was established based on vertebrae where both readers had 100% agreement
(56%) and parameters were estimated using models from Von Bertallanfy, Gompertz,
Richards and Schnute. The model that provided the best fit for the data was
Richards', yielding Linf = 70.0 cm, K = 0.57, T0 = 2.27. These results were
verified using MULTIFAN, a length frequency analysis based on five length
distributions totalling 10.361 individuals.
Cortés, Enric
NOAA/NMFS, Panama City, FL 32408
Life history patterns and relationships in
sharks
This study examines life history patterns
and correlations between traits related to body size, reproduction, age, and
growth in sharks, using data from over 200 populations. Interspecifically, body
size correlated positively with litter size and offspring size, and a trade-off
between litter size and offspring size was found after factoring out the effects
of body size. Offspring size correlated positively with growth completion rate
(K) after correcting for body size effects. Parental size for males, females,
and genders combined was negatively correlated with K. Parental size and size at
maturity exhibited a strong positive correlation, with sexual maturity occurring
at about 75% of maximum size in both genders. Males were found to be 9% smaller
than females and to reach their maximum length 46% faster than females on
average. Maximum size and longevity were not correlated in females, but were
positively correlated in males. Principal component and cluster analyses were
used to reflect similarities among traits of 40 populations and three separate
life history strategies were identified. Among conspecifics, body size shows
considerable geographic variability, but no clear patterns could be discerned.
There is also limited evidence of clinal variation in life history traits in
some species.
Didier, Dominique A.
The Academy of Natural Sciences,
Philadelphia, PA 19103
Diversity and taxonomy of chimaeroid
fishes (Chondrichthyes, Chimaeridae)
At present there are 34 described species
of chimaeroid fishes. Taxonomy of this lineage is historically problematic and
many species of chimaeroids remain undetermined due to lack of useful characters
for species identification. As part of a taxonomic revision of chimaeroid fishes
over 1200 specimens were examined. A total of 35 measurements were taken on each
specimen for morphometric analysis. At least 5 described species of chimaeroids
are synonymous, 4 new species have been described, and at least 9 additional new
species have been discovered. Status of each species, including several newly
described species, and known geographic range, including range extensions for
some species are presented. Characters for species determination and
phylogenetic analysis are identified. Accurate identification of species is
critical for management and preservation of chimaeroids as a bycatch and
emerging fishery. This study emphasizes the instrumental role of systematics
research centers, such as museums, as leaders in addressing issues of global
biodiversity and conservation. Supported by NSF DEB-9510735.
*Ellis, Jim, Rogers, Stuart
Lowestoft Laboratory, Centre for the
Environment, Lowestoft, Suffolk NR33 0HT U.K.
Nursery areas of elasmobranch fishes in
the coastal waters of the British Isles
Nursery areas are utilised by many species
of elasmobranch fishes and are important habitats for neonatal and juvenile
individuals. Nursery areas of coastal elamobranchs are typically in shallower
waters than areas inhabited by the adults, and usually provide abundant food
resources and protection from predation. Nursery areas have been documented for
several species of carcharhinid and sphyrnid sharks, although there have been
fewer studies on the nursery grounds of other families. Additionally, there are
few records of elasmobranch nursery grounds in the coastal waters of the British
Isles. Groundfish survey data (1988-1998) from the English Channel, Irish Sea
and Bristol Channel were used to identify those locations where juvenile
demersal elasmobranchs and the egg cases of oviparous species (e.g. Raja
spp. and Scyliorhinus canicula ) occur. Recent data on the
macro-epibenthic assemblages within the study areas are used to describe some of
the biological characteristics of these juvenile habitats.
*Feldheim, Kevin A., Gruber, Samuel H.,
Ashley, Mary V.
(KAF) Dept. of Biological Sciences,
University of Illinois at Chicago/Bimini Biological Field Station, Chicago, IL
60607; (SHG) Division of Marine Biology and Fisheries, Bimini Biological Field
Station/University of Miami, Miami, FL 33194; (MVA) Dept. of Biological Sciences
(M/C 066), University of Illinois at Chicago, Chicago, IL 60607
Multiple paternity of a lemon shark litter
determined by DNA microsatellite analysis
A long term field and genetic study of
lemon shark mating system and breeding biology is in progress at a nursery
ground in Bimini, Bahamas. In the spring of 1996 an adult female lemon shark was
caught, measured, sampled for DNA analysis, and injected with a PIT tag. The
female was judged to be pregnant when caught. This same female was also caught
in April, 1998. At the time of her second capture, the female gave birth to 13
offspring, of which 11 were caught, tagged, and sampled. The recapture of this
female provides the first definitive evidence that female lemon sharks are
returning to give birth at the Bimini nursery ground, and the reproductive cycle
can be no longer than biennial for some females. We used four microsatellite
marker loci, developed from a genomic library of Negaprion brevirostris,
to genotype the adult female and her litter. At two of the four loci, four
paternal alleles were observed among the pups, indicating that the littermates
were sired by at least two males. These results suggest that lemon sharks likely
have a polygamous mating system. Observation and analysis of this single female
therefore provided critical new information regarding the mating and
reproduction of a large coastal shark.
*Feldheim, Kevin A., Gruber, Samuel H.,
Ashley, Mary V.
(KAF) Dept. of Biological Sciences,
University of Illinois at Chicago/Bimini Biological Field Station, Chicago, IL
60607 U.S.A; (SHG) Division of Marine Biology and Fisheries, Bimini Biological
Field Station/University of Miami, Miami, FL 33194; (MVA) Dept. of Biological
Sciences, University of Illinois at Chicago, Chicago, IL 60607
Isolation and characterization of
microsatellite markers in the lemon shark genome
Although microsatellite loci have proven
to be extremely useful for population genetic studies of many vertebrates, their
application in elasmobranchs has been extremely limited. We are currently
developing microsatellite markers for lemon sharks ( Negaprion
brevirostris ) in order to assess the local mating system and
larger-scale stock structure of this species. A size selected plasmid library
was constructed from genomic DNA and screened for 10 di- and trinucleotide
repeats. Screening yielded 42 positive clones, of which 35 have been sequenced.
(CA)n and (GA)n dinucleotide repeats were
primarily found. Primer pairs were developed for 21 loci, and these are being
screened. To date, only five loci have been shown to be polymorphic, suggesting
that microsatellite loci in sharks may be less variable than in other
vertebrates. Two loci, LS22 and LS30, have been optimized, and at least 90 adult
and juvenile lemon sharks from two populations, Bimini, Bahamas, and Marquesas
Key, Florida have been genotyped at each locus. LS22 has 16 alleles and observed
heterozygosity of 0.82 and LS30 has 15 alleles and observed heterozygosity of
0.70. These preliminary data suggest that although application of microsatellite
markers in elasmobranchs may require additional screening, these markers can
provide an important new tool for shark biologists.
*Fluharty, Cynthia A., Grogan, Eileen D.
Saint Joseph's University, Philadelphia,
PA 19131
Chondrichthyan calcified cartilage:
chimaerid cranial tissue with reference to Squalus.
Select cartilages of the chimaerid, Callorhinchus
capensis, were processed for light microscopy, stained with hematoxylin and
eosin, alizarin red, and von Kossa stains, and assessed for features of
mineralization. The calcified cartilage demonstrates a tesserate-mode of
mineralization which is fundamentally similar to that observed for Squalus
acanthias . Calcification exists in the form of superficial, polygonal
deposits of calcium phosphate. In cross section, they appear block-like and are
located subperichondrally. Viable chondrocytes and Liesegang waves could be seen
throughout the bodies of calcification. Comparison of select stains permits a
study of progressive mineralization. Presumptive sites of mineralization first
stain positive with alizarin red then positive with von Kossa. This suggests the
progression from calcium to calcium phosphate as mineralization proceeds.
Fundamentally these results conform to those obtained from examination of S.
acanthias . They demonstrate similar developmental and histological
characteristics of mineralization in sister taxa. However, there was no evidence
of a discrete tessera cap, as has been noted in Squalus and
other sharks and jaw tissue provided evidence of mineralization other than that
found peripherally. Regional variation in the stage of mineralization was
observed across the tissue. At this time these features are interpreted as
architectural and stress related.
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