Helminth parasites in the toad Rhinella major (Bufonidae) from Chaco region, Argentina

The present study describes the diversity of helminth parasites of Rhinella major (Anura: Bufonidae) in relation to their body size in 4 subhumid vs. semiarid sampling sites from the Argentine Chaco region. Helminths were found in 81% of the specimens examined (n = 85). Fifteen species (13 in subhumid and 7 in semiarid areas) of helminth parasites were found, and most of them were nematodes. Parasites were found in all the examined organs, with highest prevalence and intensity in the digestive tract. Parasite transmission to the toad host occurs by skin penetration or oral ingestion. Maximum helminth richness ranged between 2 and 4 species per infected toad. The most abundant species was Aplectana hylambatis. Body size of the host was the main factor in determining parasite richness. The helminth parasite fauna was rather different in hosts from subhumid vs. semiarid sites, but the dominant (Aplectana hylambatis) and codominant species (Cylindrotaenia sp. and Rhabdias elegans) were the same. Mean species richness and mean species diversity of helminths were significantly different between the zones. These results suggest that the amount of rainfall and associated humidity affects the distribution and development of the parasite fauna of this toad