Studies on the Life Cycle of Huffmanela huffmani (Nematoda: trichosomoididae)

Abstract

The histozoic nematode Huffinanela huffinani Moravec, 1987 (Trichosomoididae) parasitizes the gas bladders of several species of centrarchid fishes in the upper spring run of the San Marcos River, TX. Despite a previously reported prevalence of up to 90%, year-round presence of freshly laid eggs in the gas bladders, and years of research, knowledge of the parasite’s life cycle is limited. The objective of this study was to gather information relevant to the life cycle of H. huffinani. This objective was met through prevalence studies, definitive host diet analysis, in vitro culture experiments, and infection challenges. The overall prevalence of H. huffinani was 59%. A trend of decreasing H. huffinani prevalence downstream from the headsprings of the San Marcos River was observed. No single diet item appeared to be more prevalent in the diet of infected definitive hosts than in that of uninfected definitive hosts. Two new techniques successful in the extraction and induced hatching of H. huffinani eggs are described. No H. huffinani larvae were successfully cultivated. Three models depicting potential life cycles are described for H. huffinani. Several candidate intermediate hosts for H. huffinani are identified; however, use of these hosts in infection challenges did not produce infections in definitive hosts. These results suggest the life cycle of H. huffinani is most likely indirect, and the required intermediate host is most likely of an unknown taxon directly associated with the headsprings of the San Marcos River.