Acanthocephala of the Subfamily Rhadinorhynchinae from American Fish

Abstract

But two species of Acanthocephala have, to the present time, been definitely ascribed to the genus Rhadinorhynchus. Echinorhynchus pristis Rud. was the original species for which Liihe (1911) created this genus. One year later he added another species to the genus by his description of R. horridus from Egypt. The older species has been reported as parasitic in fishes from various parts of the world. The descriptions given in these scattered reports differ so radically that it seems improbable that they could all apply to single species. Here, as in other genera of Acanthocephala, it seems obvious that the older workers, recognizing the cardinal points which in modern classification have been accepted as indicative of generic value, have failed to observe the less obvious, though significant, differences which serve to separate species. Thus all members of the present genus Rhadinorhynchus have been identified as E. pristis, and the descriptions have usually been inadequate to enable more recent workers to recognize the same forms if encountered again. In some few instances the descriptions have been complete enough to permit one to recognize the forms described. Linton's work on E. pristis is of the type last mentioned. In 1891 Linton recorded the occurrence of Acanthocephala which were at least similar to E. pristis from the intestine of Tylosurus acus (Lacep), and of Lobotes surinamensis (Bloch). After acknowledging perplexity in attempting their identification, Linton tentatively ascribed some of his individuals to the species E. pristis, while others he referred to new variety of that species. To the variety he gave the name E. pristis tenuicornis. In later work he remarked upon the presence in what he determined as E. pristis from fishes at Beaufort, N. C., of a of at the base of the proboscis which are longer than the other hooks (Linton, 1908:89). This circle of was briefly mentioned in an earlier paper (1892:531). In materials studied by the present writer, the spines at the base of the proboscis, though not forming circle, are very conspicuous. After comparison of these specimens with data given by Linton the writer is convinced that Linton was at various times dealing with at least two distinct species of the genus Rhadinorhynchus to which he gave