Notes on Juvenile Acanthocephala

Abstract

While examining pike from the Great Lakes a number of small fish which could not be identified were found in the pike stomachs. These small fish were then examined, and an amphipod containing a juvenile specimen of Pomphorhynchus bulbocolli was recovered from one of them. This specimen (Fig. 1) is a female and its measurements are as follows: Body 4.9 mm long by 0.7 mm in maximum diameter. Proboscis 0.4 by 0.2 mm. Neck 1.3 by 0.23 mm. Proboscis hooks in 12 longitudinal rows with 14 hooks each. Anterior hooks 0.04 mm long and posterior hooks 0.02 mm long. The ovary has dissociated to form four masses about 0.07 by 0.05 mm located in the ligament. The mesenteries of these smaller fish contained numerous specimens of encysted acanthocephalans which could be identified as P. bulbocolli by the number and arrangement of proboscis hooks. The size of the cysts (Fig. 2) varied from 0.7 by 0.3 mm to 2 by 0.4 mm. The worms seemed to have degenerated and very little of their internal structure could be distinguished. Meyer (1933) suggests that acanthocephalan cysts in the second or third intermediate host undergo degeneration after reaching a certain age, or degenerate as a result of defense mechanisms of the host and improper nourishment. Adults of P. bulbocolli have been reported from a number of host species including Catosto1mus commersonii, Cyprinus carpio, Erimyzon sucetta oblongus and Notemigonus crysoleucas. Van Cleave (1934) states that the suckers and sucker-like fishes are the most frequent hosts of this species. Cysts of P. bulbocolli have been reported from Percina caprodes, although adult specimens were found in the intestine of this host at the same time (Van Cleave, 1919). No record of the occurrence of this species in an arthropod has been found in the literature. Leuckart (1862) found juvenile stages of Echinorhynchus proteus (sic) in the body cavity of Gammniarus pulex. He was probably dealing with Pomphorhynchus laevis or Polymorphus mvinlutus, as suggested by Meyer (1933). Leuckart also conducted an experiment in which he infected Gammarus with the eggs of this species and obtained juvenile