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Three polymorphic DNA microsatellite loci were developed in the sandbar shark (Carcharhinus plumbeus) and used to test the hypothesis that sharks from the midAtlantic Bight and western Gulf of Mexico comprise a single genetic stock. No significant differences in microsatellite allele frequencies were detected, a finding consistent with the null hypothesis. Polymorphic microsatellite loci appear to be scarce in sandbar sharks relative to other fish species. The three loci examined in this study had relatively low levels of heterozygosity, most likely attributable to the small number of dinucleotide repeat units per locus. T HE sandbar shark (Carcharhinus plumbeus) is

Recent studies have shown that by 1991 the sandbar shark (Carcharhinus plumbeus) population along the Atlantic coast of the United States had declined in abundance to approximately 20% of its level in the late 1970s. This phenomenon allowed us to test the hypothesis that compensatory (density-dependent) growth occurred after severe population reduction. Age and growth of sandbar sharks were investigated by counting rings and back-calculating lengths at previous ages from vertebral samples collected in 1980-1981 and 1991-1992. The collections included 188 sharks from 1980-1981 and 412 sharks from 1990-1991 ranging in length from 51-172 cm precaudal length (PCL). All sharks were mature at lengths > 136 cm PCL. Minimum and maximum ring counts, which included a birth mark, were 1 and 25. Age at maturity was 15-16 years for both sample periods and both sexes. For sexes combined, the von Bertalanffy growth parameters were L,. = 199 cm PCL, K = 0.057, to = -4.9 years for the 1980-1981 sample and L,. = 164 cm PCL, K = 0.089, to = -3.8 years for the 1991-1992 sample. Statistical tests found significant differences between the two growth models. Significant differences in size at age and annual incremental growth of juveniles suggest a small increase in juvenile sandbar shark growth rate between the two sampling periods. However, age at maturity was unchanged between samples suggesting that any biological significance of a growth rate increase has not been realized.

The purpose of this study was to investigate the reproductive biology of sandbar sharks, Carcharhinus plumbeus from northeastern Taiwan waters. A total of 885 sandbar sharks was examined. The size of 50% maturity in sandbar shark is taken to be 170-175 cm and 175 cm for females and males, respectively. The number of embryos per litter ranged from four to 12, with a mean of 7.54. Pregnant individuals containing six, seven, or eight embryos constituted 59 (80%) of the 74 females examined. Of 558 embryos in 74 litters examined, 274 were female and 284 were male. The null hypothesis of a 1:1 sex ratio is not rejected at the 0.05 level. Pups are born from Feb. to April. We estimate the gestation period to be 10-12 months. Most embryos had attained a total length of about 60-65 cm after 10-12 months of development, at which size they could be readily separated from the placenta, suggesting that they were full term and ready to be born. The relationship between the total number of uterine embryos and the total length of mother is roughly described by the regression equation (n = -7.544 + 0.075 TL; n = 74; r = 0.41). Although it is clear from this regression that fecundity is related to the size of the mother, the relationship is not particularly strong. We find that fertilization occurs during April and May, two months prior to the estimate reported by Taniuchi for C. plumbeus in Japanese waters.

Allozyme electrophoresis and restriction fragment length polymorphism analysis of mitochondrial DNA (mtDNA) were performed on sandbar sharks (Carcharhinus plumbeus) from coastal waters of Virginia, including the Chesapeake Bay, and the Gulf of Mexico to test the hypothesis that individuals from the two locations comprise a single gene pool. Both techniques revealed a very low degree of genetic variability within the species (allozyme mean heterozygosity = 0.005, mean nucleotide sequence diversity = 0.036%). The small amount of genetic variation present appeared to be evenly distributed between sampling locations; and therefore, the null hypothesis of a single gene pool could not be rejected (contingency X2 = 1.344, P > 0.5, chi-square significance of mtDNA haplotype distribution = 0.81). This conclusion is consistent with the known life-history characteristics of the species, as well as the results of tagging studies.

comparative succcess of 3 types of external tags. Fla. Sci. 48(3):146-154. . 1985b. Nurse sharks of Big Pine Key (FL): an investigation of growth and movement and a comparison of the success of several types of external tags, p. 655-661. In: Proc. 5th Int. Coral Reef Congress, Volume 6. C. Gabrie and V. Harmelin (eds.). 27 May-1 June, 1985. Tahiti, French Polynesia. Antenne Museum-EPHE, Moorea, French Polynesia. CASEY,J. G., H. L. PRATT AND C. E. STILLWELL. 1985. Age and growth of the sandbar shark (Carcharhinus plumbeus) from the Western North Atlantic. Can. J. Fish. Aquat. Sci. 42:963-975. COMPAGNO, L. J. V. 1984. FAO species catalog, Volume 4, Part 1. GILBERT, P. W., AND F. G. WOOD,JR. 1957. Method of anesthetizing large sharks and rays safely and rapidly. Science 126(3266):212-213. GRUBER, S. H., AND R. G. STOUT. 1983. Biological materials for the study of age and growth in a tropical marine elasmobranch, the lemon shark, Negaprion brevir stris (Poey). NOAA Tech. Rpt. NMFS 8:193-205.

KISCH, B. 1951. Erythrocytes in fishes. Exp. Med. Surg. 9:125-137. LARSSON, A., M-LJOHANSSEN-SJOBECK AND R. FANGE. 1976. Comparative study of some haematological and biochemical blood parameters in fishes from the Skagerrak. J. Fish. Biol. 9:425-440. PENNELLY, R. R., R. W. NOBLE AND A. RIGGS. 1975. Equilibria and ligand binding kinetics of hemoglobins from the sharks, Prionace glauca and Carcharhinus milberti. Comp. Biochem. Physiol. 52B:83-87. PRESTON, A. 1960. Red blood values in the plaice (Pleuronectes plastessa L.). J. Marine Biol. Ass. U.K. 39:681-687. SAUNDERS, D. C. 1966a. Elasmobranch blood cells. Copeia 1966:348-351. . 1966b. Differential blood cell counts of 121

Three methods for determining food consumption were used to estimate the daily ration of young sandbar sharks in Chincoteague Bay, Virginia. One method required information concerning the rate of gastric evacuation and the amount of food in the stomachs of sharks caught in the wild. Another approach used the stomach contents to determine feeding frequency and reconstruct meal size. The final method for estimating daily ration was a bioenergetics model relating food intake to growth and metabolism. Most of the parameter estimates needed in each of the models were obtained from earlier studies on this shark but several values were extrapolated from studies of other species. The estimates produced by the models were compared with respect to the assumptions implicit in each and the uncertainties associated with the parameter values used. Overall, the models produced similar estimates and indicate that the daily ration for this shark in Chincoteague Bay is close to 1% body weight (BW).

cm per year for the later years of life. Females have been taken as much as 251 cm long, while males have reached only 214 cm. The proposed growth curve is based on males, except for some of the smallest individuals, so growth rate can only be surmised for large females, by extrapolation. The available evidence suggests that they reach their larger size mainly through longer life--approximately 16 years for females of about 2.5 meters to about 12 years for males of maximum size.

NOLF, D. 1985. Otolithi piscium, p. 1-145. In: Handbook of Paleoichthyology, Vol. 10. H.-P. Schultze (ed.). Gustav Fischer, Stuttgart, West Germany. SCHAEFFER, B. 1967. Comments on elasmobranch evolution, p. 47. In: Sharks, skates and rays. P. W. Gilbert, R. F. Mathewson, and D. P. Rall (eds.). Johns Hopkins, Baltimore, Maryland. SCHULTZE, D. M. 1988. Notes on the structure and phylogeny of vertebrate otoliths. Copeia 1988:257259. STEEL, R. 1985. Sharks of the world. Blandford Press, Poole, Dorset, England. STEWART, C. 1906. On the membraneous labyrinths of Echinorhinus, Cestracion and Rhina. Zool. J. Linn. Soc. 29:439-442. STINGO, V. 1979. New developments in vertebrate cytotaxonomy II. The chromosomes of the cartilaginous fishes. Genetica 50:227-239. STOLKOWSKI, J. 1962. Essai sur le determinisme des formes mineralogiques du calcaire chez les etres vivants. Ann. Inst. Oceanogr. 26:1-113. TESTER, A. L.,J. I. KENDAL AND W. B. MILISEN. 1972. Morphology of the ear of the shark genus Carcharhinus, with particular reference to the macula neglecta. Pac. Sci. 26:3, 264-274. TSuJI, S., AND T. AOYAMA. 1982. Daily growth increments observed in otoliths of the larvae of Japanese Red Sea Bream Pagrus major (Temminck et Schlegel). Bull. Jap. Soc. Sci. Fish. 48:1559-1562. WRIGHT, C. G., P. C. ROUSE, S. D. SCHAEFER, D. G. HUBBARD AND L. A. BARNARD. 1982. A calcareous

Neonate Rhizoprionodon terraenovae, Carcharhinus plumbeus, and C. limbatus were held in laboratory aquaria for a 16 mo study on the periodic formation of bands found in the vertebral centra. The sharks were injected with tetracycline to mark the vertebrae, and the aquarium situation mimicked seasonal environmental fluctuations. The tetracycline incorporated within a 3 d period, and a definable annual mark formed between Oct. and Dec. which was visible just off the edge of the centra by Jan. Age/growth data for R. terraenovae from a concurrent field study produced a von Bertalanffy growth curve with an Loo = 108 cm TL, K = 0.359, and to = -0.985 yr; values similar to known life history characteristics. Growth of the lab-reared R. terraenovae closely matched this curve. RECENT expansions in recreational and commercial efforts for sharks in the Gulf of Mexico prompted a study initiated in 1981 to better define the age and growth of the most commonly taken species. Sharks were aged by enumeration of the alternating calcified (opaque) and less calcified (translucent) bands discernable in the centra. Band pair periodicity must be verified and/or validated for each species (Brothers, 1983; Cassleman, 1983; Smith, 1983) and for all age/size classes (Beamish and McFarlane, 1983). In either sagittal or frontal sections cut from centra, a distinct mark cor

(Pisces: Cyprinodontidae) with special reference to a quantitative analysis of parental fanning. Z. Tierpsychologie 23:537-554. MINCKLEY, W. L., AND E. T. ARNOLD. 1969. "Pit-digging," a behavioral feeding adaptation in pupfishes (Genus Cyprinodon). J. Arizona Acad. Sci. 5:254-257. s: Cyprinodontidae) with special r ferRANEY, E. C., R. H. BACKUS, R. W. CRAWFORD AND C. R. ROBINS. 1953. Reproductive behavior in Cyprinodon variegatus Lacepede, in Florida. Zoologica 38:97-105.

All elasmobranch placentae are of the yolk-sac type, but within this single classification rather wide structural variations occur. The placenta of C. falciformis possesses a discoidal shape and is completely nondeciduate. The following layers intervene between the foetal and maternal blood systems: (1) maternal endothelium, (2) maternal epithelium (essentially not reduced), (3) possibly the egg-case membrane, depending on factors stated in the paper, (4) foetal epithelium (greatly reduced), and (5) foetal endothelium.

Nineteen sharks collected from freshwater at several points on Lake Nicaragua and the Rio San Juan were all of the same species and indis­ tinguishable from marine Carcharhinus leucas of the Atlantic. Minor differences previously thought to separate C. leucas from the lake shark proved to be invalid. Females had slightly longer gill slits, somewhat greater breadth of pelvic fin, and a longer abdominal region than males. Clasper length indicated that the onset of sexual maturity in males occurs when they are between 1,600 and 1,700 mm in total length. The classical theory or origin of the sharks from Pacific ancestry no longer appears tenable. An Atlantic origin is indicated by (a) strong evidence that the taxonomic affinities not only of the shark, but also of the sawfish and tarpon, are more pronouncedly with Atlantic relatives than with those of the Pacific, (b) recent evidence that Lake Nicaragua may never have been a part of the Pacific but opened originally to the Atlantic, (c) the fact that Lake Nicaragua drains into the Caribbean Sea by a large, broad river, and (d) all three of the large, otherwise marine types of fish occurring in the lake are species that habitually congregate in brackish water and frequently move up rivers. Evidence that the sharks are not landlocked includes the following facts: (a) they are abundant the full length of the river, (b) barges drawing from one to three feet of water regularly negotiate the river (including all of the rapids) in both directions, (c) sharks were observed both below and above the three major rapids as well as actually in the rapids, most of them headed upstream.

The genus Poecilancistriumn Dollfus, 1929 is reduced to a single species P. caryophyllum (Diesing, 1850) Dollfus, 1942. Adults are described from a bull shark and lemon shark from the Gulf of Mexico and a list of hosts and the known range of the parasite are presented. Thatcher (1961) reported two specimens of Poecilancistrium robustum (Chandler, 1935) Dollfus, 1942 in Carcharhinus limbatus, the spot-fin ground shark. Only one specimen was mature and this was briefly described. In a subsequent abstract Goldstein (1962) reported P. robustum from C. leucas, the bull shark, and from Negaprion brevirostris, the lemon shark; the present paper contains a description of this worm based on 30 specimens and an analysis of the genus Poecilancistrium Dollfus, 1929. The material herein described was obtained from a bull shark (1.75 m in length) and a lemon shark (2.24 m in length) collected during the summer of 1961 from the coastal waters of the Gulf of Mexico in the vicinity of the Alligator Harbor Marine Laboratory of Florida State University. The worms were fixed in aceto-formolalcohol, some with pressure, others without. Thirty were stained as whole mounts with Semichon's acetocarmine, borax carmine, or alum cochineal. Three were sectioned transversely or frontally at 15 p and stained with Ehrlich's acid hematoxylin and eosin or Mallory's triple stain. Drawings were made with the aid of a camera lucida and a microprojector. All measurements are in millimeters; averages are given with ranges in parentheses. Measurements, except those of the hooks, are from specimens fixed without pressure. DESCRIPTION OF ADULT Maximum length of 13 specimens from the lemon shark and 12 from the bull shark, 120; minimum length, 25; minimum length of a mature specimen, 90. Scolex (Fig. 1): Length (14 worms), 3.22 (2.90 to 3.69); width (10 worms), 1.14 (1.04 to 1.52); length of bothridia (14 worms), 1.61 (1.23 to 1.88); bulb length (14 worms), 1.10 (0.96 to 1.16); bulb width (14 worms), 0.34 (0.30 to 0.40); diameter of 14 tentacles excluding hooks (14 worms), 0.13 (0.10 to 0.14). External face of tentacle (Fig. 2) with large hooks in successive whorls about 0.07 apart; each whorl consisting of a pair of large hooks (1, Fig. 2) followed on either side by three, sometimes four, successively smaller hooks (2, 3, 4, 4a) which form a broad V converging to the pair of large hooks; internal face of tentacle covered by small, spinelike hooks (5) tending in irregular diagonal rows. Total length of largest hooks (1) (48 hooks, ten worms from lemon shark), 0.107 (0.084 to 0.120); (50 hooks, five worms from the bull shark) 0.113 (0.102 to 0.120). Total length of small hooks (5) (69 hooks, nine worms from lemon shark), 0.027 (0.024 to 0.030); (50 hooks, five worms from bull shark) 0.027 (0.024 to 0.030). Strobila: Neck short; strobila acraspedote, apolytic; proglottids (Fig. 3) rapidly becoming much longer than wide toward the posterior part of the strobila. Testes, 0.070 (0.054 to 0.090), numerous, medullary, some postovarian; genital pores marginal, irregularly alternate, each in a shallow notch in the posterior third of the proglottid; cirrus unarmed, contained within large cirrus pouch. Ovary bilobed, follicular, in cross section appearing broadly X-shaped; Mehlis' gland conspicuous, between the ovarian lobes, posterior to the isthmus; uterus median, extending slightly into anterior fourth of segment; eggs, 0.030 by 0.018 (seven, partially collapsed, in sectioned material).

Cathetocephalus thatcheri gen. et sp. n. is described from the spiral valve of the bull shark, Carcharhinus leucas (Valenciennes), taken in the Gulf of Mexico and the Atlantic coast of Florida. A new family is erected for the new genus. The species most closely resembles Pillersium owenium Southwell, 1927, in that both possess a scolex which is perpendicular to the long axis of the strobila. It differs, however, in having a single neck and holdfast organ rather than a bifurcate neck with 2 bothridia. Also, the surfaces of the scolex differ from those of P. owenium by possessing fleshy pa- pilliform structures on the leading and trailing edges rather than leaflike folds. Specimens with sev- eral strobilae are figured and discussed. A heavy infection of cestodes was found in the spiral valve of two specimens of the bull shark, Carcharhinus leucas (Valenciennes), that had been collected in Galveston Bay, Texas. The sharks had been flown to Sea World, San Diego, California, and died several days later. Additional specimens were also recovered from the same species of host at Mi- ami, Florida. The presence in those worms of a unique multistrobilate condition in some specimens prompted this study. The species does not have the typical tetraphyllidean scolex, but is considered here as representing a new genus in a new family in the order Tetraphyllidea. Worms were fixed in AFA, Bouin's fluid, or 10% formalin. Whole mounts were stained with cellestine blue B or Semichon's carmine. Sections of other specimens were cut at 6, 8, and 10 Au and stained with hematoxylin-eosin or Mallory's trichrome stain. All material was dehydrated in ethanol, cleared in xylene, and mounted in Piccolyte. Drawings were made with the aid of a drawing tube and stereo- scopic microscope. Average measurements are given, with ranges in parentheses. They are in millimeters unless otherwise indicated.

The material was collected during the summer of 1922 by Mr. Rodric Heffron of Chicago, to whom I am greatly indebted. One blood smear was made from each fish, air-dried and later stained with either Giemsa or Heidenhain's ironhematoxylin. The names and number of fishes examined are as follows: Carcharhinus obscurus, 1; Isurus dekayi (?), 1; Raia ocellata, 3; R. erinacea, 1; Acanthocottus aeneus, 2; Brevoortia tyrannus, 1; Chilomycterlus schoepfii, 5; Cyclopterlts

MAHADEVAN, G. 1940. Preliminary observations on the structure of the uterus and the placenta RICK, J. A. F., R H. BACKUS, AND R. H. I BS, JR. 1964. Carc arhinus floridanus, e silky shark, a synonym of C. alciformis. eia 1964(2):369-375. I BERT, P. W. AND D. A. SCHLERNITZAUER. 1965. lacentation in the silky shark, Carcharhinus lciformis, and the bonnet shark, Sphyrna of a few Indian elasmobranchs. Proc. Ind. Acad. Sci., ser. B, 11:2-38. RANZI, S. 1934. Le basi fisiomorfologiche dello svilluppo embrionale dei Selaci-Parti II e III. Pubb. Staz. Zool. Napoli 13:331-437. STRASBURG, D. W. 1958. Description, abunda ce, and habits of pelagic sharks in the central Pacific Ocean. U. S. Fish Wildl. Serv. Fish. Bull. No. 138, 58:335-361. DIVISION OF BIOLOGICAL SCIENCES, CORNELL UNIVERSITY, ITHACA, NEW YORK.

Carcharhinus floridanus Bigelow, Schroeder, and Springer, 1943 (holotype a female about 2,300 mm long) and C. falciformis (Bibron 1841) (holotype a 528-mm embryo) represent the size extremes of a single species the name of which should be C. falciformis. This conclusion is based on the study of 65 specimens comprising both sexes and well distributed over the size range of the animal. The physical characters heretofore used to distinguish these nominal species, pectoral fin length, eye diameter, dorsal fin shape, contour of snout, and character of the denticles, all are shown to change gradually with growth from one supposed diagnostic set to the other. C. falciformis is sometimes confused with other carcharhinid sharks and means of distinguishing it from two of these, C. obscurus and Hypoprion signatus, are given.