Seasonal Occurrence and Host-Parasite Relationships of Neoechinorhynchus saginatus Van Cleave and Bangham 1949 in the Fallfish, Semotilus corporalis (Mitchill)

Abstract

The seasonal occurrence, population dynamics, intestinal distribution, and host specificity of Neoechinorhynchus saginatus infecting the fallfish, Semotilus corporalis, from the Oyster River, New Hampshire, were studied from June 1975 through July 1976 and March 1977 through December 1977. Neoechinorhynchus saginatus did not exhibit a clearly pronounced seasonal pattern in prevalence and mean intensity. Prevalence was 44% or higher in all months sampled. The number of parasites per examined fish differed significantly between June 1975 through July 1976 and March 1977 through December 1977. Gravid females and subadult N. saginatus were recovered throughout most of the sampling period. Neoechinorhynchus saginatus occurred throughout the intestine of fallfish, but the majority of acanthocephalans was recovered from the middle portion of the intestine. The intestinal distribution of females and males was similar. Gravid females were most common in the region of the first intestinal flexure below the fallfish's stomach. The sex ratio was found to be very close to 1 : 1. Both prevalence and mean intensity increased significantly with increasing size of fish. Although N. saginatus occurred in 4 other fish species, gravid worms were only recovered from fallfish.