Two Tetraphyllidean Cestodes from Hawaiian Stingrays

Abstract

Two new species, Acanthobothrium chengi and Rhinebothirum hawaiiensis (Cestoda: Tetraphyllidea), are described from the stingray, Dasyatis lata. Distinguishing characteristics of 24 definitive, and six tentative species of Rhinebothrium are reviewed and tabulated. This represents the first report of marine cestodes from Hawaii and one of the few recorded species of Rhinebothrium from beyond the Eastern Pacific. Examination of available literature indicates a paucity of studies concerning elasmobranch cestodes from the Central Pacific. Goldstein (1967) employed geographical criteria in differentiating species of Acanthobothrium and Campbell (1969) proposed that geographical distribution of intermediate hosts explained the presence or absence of this cestode from the same definitive host captured in different locations. The present study concerns collections of elasmobranch cestodes from 11 sharks and two stingrays taken off the Hawaiian islands of Nihau, Kauai, and Oahu during July and August 1967. Two large adult female stingrays (Dasyatis lata), measuring 127 to 140 cm in diameter, were caught on baited handlines off the northwest (windward) shore of Oahu. A sampling of helminths from the two spiral valves included two trypanorhynch cestode species (not identified at this time) and two new tetraphyllideans, Acanthobothrium chengi and Rhinebothrium hawaiiensis. MATERIALS AND METHODS The 2 stingrays were taken in approximately 20 fathoms of water about a mile offshore from Waimea Bay (21?35' N, 57?55' W). Worms were removed from the posterior third of the spiral valve and fixed without pressure in AFA. Whole mounts were stained with Mayer's paracarmine or Ehrlich's acid hematoxylin, counterstained with fast green, dehydrated in a graded ethanol series, cleared in methyl salicylate, and mounted in Permount. Hematoxylin (Harris') and eosin stained serial sections of proglottids were prepared for further study in a routine manner. Illustrations were made with the aid of a microprojector. Measurements are in microns unless otherwise indicated. Important acanthobothriid morphological characters including the mean, standard deviation, and range are given as suggested by Goldstein (1964, 1967). Gosline and Brock's (1965) handbook was used in identification of the hosts. Received for publication 3 June 1974. * Present address. Acanthobothrium chengi sp. n.