Variations in the fecundity and body size of digenean (Opecoelidae) species parasitizing fishes from Northern Chile

Abstract

Parasite life history and reproductive strategies show considerable variability associated with host identity and/or environmental factors. In this study, we measured parasite body length (PBL) and fecundity of 3 digenean species: Helicometra fasciata, Helicometrina nimia and Neoleburia georgenascimentoi, in their different host species, to evaluate the host influence on these biological traits. Additionally, parasite identifications were confirmed using molecular markers (V4 region of 18S and CO-I genes). From January 2010 to June 2012, 305 fish belonging to Paralabrax humeralis, Acanthistius pictus; Labrisomus philippii; Prolatilus jugularis and Pinguipes chilensis were captured, by diving, off the northern Chilean coast (24°S). In the laboratory, fish were measured and all their parasites collected. The total length and body width of each individual parasite were measured and all eggs were extracted from the parasites' uterus and counted. Generalized lineal models were used to identify factors affecting fecundity of digeneans. Fecundity of H. nimia was highest in A. pictus and lowest in individuals from L. philippii; fecundity of H. fasciata was highest in P. humeralis and lowest in L. philippii and fecundity of N. georgenascimentoi was highest in P. chilensis. GLM showed that variations in fecundity of digeneans are explained by host fish species and by PBL. Variations in PBL and fecundity are apparently associated with host species sizes: longer parasites (with more eggs per parasite) were recorded in larger fish species (P. humeralis, A. pictus and P. chilensis). However, molecular analyses showed that H. nimia from L. philippii should be considered a distinct species from specimens found in A. pictus and P. humeralis, while N. georgenascimentoi from P. jugularis should be considered a distinct species from specimens found in P. chilensis, which might explain the observed fecundity differences in those host species.