Rhinoptericola megacantha gen. et sp. n., Representing a New Family of Trypanorhynch Cestodes from the Cownose Ray, Rhinoptera bonasus (Mitchill 1815)

Abstract

Rhinoptericola megacantha gen. et sp. n. from the spiral valve of the cownose ray, Rhinoptera bonasus (Mitchill), taken in Chesapeake Bay, Virginia, is described. A new family, Rhinoptericolidae, is erected to accept the species. Distinguishing characteristics of the species include: 4 bothridia; heteroacanthous, heteromorphous, atypical armature; absence of sensory pits; an ovary consisting of 4 lobes but lacking a central isthmus; an ooreceptacle; and a uterus with 2 lateral diverticula at its proximal end. Lack of knowledge of the cestode fauna of the cownose ray, Rhinoptera bonasus (Mitchill), is due in part to the infrequent captures of this host. As Bigelow and Schroeder (1953) have pointed out, Most of the published reports of the presence of the Cow-nosed Rays at one point or another along the United States coast have been based on a few specimens. Only three references deal with the cestode parasites of this ray and the worms have proven to be unusual. Linton (1890, 1897) described species of Rhinebothrium, Rhynchobothrium, Tetrarhynchus, and Tylocephalum from this host in the Woods Hole area. Schmidt (1969) discovered that one of the species, Rhinebothrium cancellatum Linton 1890, was a dioecious tetraphyllidean representing a new family. Examination of trypanorhynchs from this host has revealed another unusual cestode which we allocate to the new family, Rhinoptericolidae, described herein. MATERIALS AND METHODS Cestodes were obtained from the spiral valve of a single adult cownose ray caught in the summer of 1967 on hook and line in Chesapeake Bay, Virginia. Worms were fixed in situ with aceto-formolalcohol (AFA) at room temperature and transferred to 70% ethanol. Whole mounts were stained with Ehrlich's acid hematoxylin, dehydrated, and mounted in Permount. Transverse and frontal sections, cut at 10 to 12 ,im, were stained with Harris' hematoxylin and counterstained with eosin. Transparent overlays were made to reconstruct internal anatomy of the segments. Some scolices were cleared in Langeron's lactophenol and mounted in glycerin jelly to facilitate study of the tentacles. Hook nomenclature is based on the system proposed by Dollfus (1942). Drawings were made with the aid of a microprojector or television monitor. Descriptive measurements are expressed as length by width and include the mean with the range given in parentheses. All measurements are in micrometers unless otherwise indicated. Rhinoptericolidae fam. n. Diagnosis: Order Trypanorhyncha. Heteroacantha atypica, with 4 well-separated, sessile bothridia whose margins are entirely free from the scolex. Scolex and tentacles long. Rhyncheal apparatus well developed. Strobila acraspedote, apolytic, with many segments. Ovary consisting of separate lobes, central isthmus absent. Ooreceptacle present. Vitellaria continuous, circumcortical. Adults parasitic in spiral valve of elasmobranchs. Type and only genus: