Umingmakstrongylus pallikuukensis (Nematoda : Protostrongylidae) in gastropods: Larval morphology, morphometrics, and development rates

Morphological and morphometric aspects of larval development of Umingmakstr ongylus pallikuukensis in Deroceras laeve and the effects of temperature on development rates in D. laeve and Deroceras reticulatum were investigated in the laboratory. Larval stages were best differentiated by separation of cuticular sheaths, tail structure, and viability following digestion. Growt h in body and esophagus width was observed during the first-stage within th e intermediate host, but the major increases in body length and width occur red immediately following the second molt. Larval development in D. laeve a nd D. reticulatum occurred more rapidly at warmer temperatures. The calcula ted threshold temperatures were 8.5 and 9.5 C in D. laeve and D. reticulatu m, respectively, and 167 degree-days were required for development to third -stage larvae (L3) in both hosts. These thresholds are higher than those ca lculated from published data for the closely related Muellerius capillaris (4.2 C) but are similar to those for the more distantly related northern pr otostrongylid, Elaphostrongylus rangiferi (8.3-10.3 C). Conversely, degree- days required for development to infective L3 were more similar among the M uelleriinae than between this group and the Elaphostrongylinae. Development al parameters for protostrongylid larvae may be influenced both by the envi ronment and by features of the parasites and the intermediate hosts, includ ing phylogeny.