Helminth parasites and phoronts of dusky dolphins <i>Lagenorhynchus obscurus</i> (Gray, 1828)

The scanty information published on parasites of the dusky dolphin Lagenorhynchus obscurus is reviewed. Prevalence of heminths in relation to body length/sex of the host and intensity of infestation in analysed for 321 dusky dolphins killed in an artisanal coastal fishery off Peru. A total of 707 animals were checked externally for ectoparasites and phoronts and 266 skulls from Peru and Chile were examined for bone lesions revealing parasitosis. Three species of trematodes, three nematode species and two cestodes were registered. These are (with prevalences): Nasitrema sp. in cranial sinuses (78.3% SE=4.2%); Phyllobothrium delphini larvae in blubber of anogenital region (70.0% SE=10.0%); Anisakis sp. mostly in the main stomach (40.0% SE=3.3%); Braunina cordiformis (8.5% SE=1.9%) and Pholeter gastrophylus (8.0% SE= 1.9%) primarily in the pyloric stomach; and an unidentified adult cestode in the intestines (3.7% SE=3.6%). Except in a single specimen, no Crassicauda-caused cranial bone lesions were seen, nor was the nematode itself found in cranial sinuses or in the blubber/muscle interface. The occurrence of the phoront Xenobalanus globicipitis, present overall on 38.9% (SE=1.8%) of dolphins, peaked in June and December. The 6-month phase difference suggests a seasonal factor determining the barnacle's life-cycle. X. globicipitis can serve as a sensitive ecological marker on a small temporal scale (months), but exactly the high 'resolving power' makes it unreliable as an indicator of breeding populations. Prevalence of helminth parasites was independent from total length and sex of dolphins, except for Braunina cordiformis where infestation rate significantly declined with body length, suggesting progressive host immunization. Nasitrema sp., B. cordiformis, P. gastrophylus, Halocercus sp., and X. globicipitis constitute first records for the host species L. obscurus