A note on the genus Poecilancistrium Dollfus, 1929 (Cestoda: Trypanorhyncha).

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).