Effect of burrowing cymothoid parasitism on loricariids

Cymothoids belong to the order Isopoda and are ectoparasites of fishes, and their main parasitism strategies are by penetrating, burrowing, and lodging in the abdominal cavity of the hosts. Due to this complex parasitism strategy, they are considered highly host-specific parasites. We investigated the effects of parasitism of the burrowing cymothoid Artystone sp. on the loricarids Hisonotus chromodontus and Curculionichthys luteofrenatus in the Selma stream, a tributary of the Teles Pires river, Southern Amazon. The hypothesis under study is that parasitism causes negative effects on the feeding, reproduction, and length-weight relationship of the hosts. The presence of alternative hosts was also investigated. The parasitic interaction of Artystone sp. with Curculionichthys luteofrenatus and Hisonotus chromodontus was monitored for one year with standardized monthly collections, and was found to be highly specific when there were no other parasitized fish species. Parasitic castration caused by Artystone sp. occurred in Curculionichthys luteofrenatus and Hisonotus chromodontus hosts, and there was a higher prevalence of infestation in females. The weight-length relationship was lower in parasitized Hisonotus chromodontus hosts, indicating a negative effect on somatic increment, although all hosts had fully replete stomachs and gastrointestinal tracts. The greatest standard-length values for both species were observed in the parasitized hosts. The presence of parasitized young specimens with undifferentiated sex and immature males and females suggests that the parasitic interaction in both species starts at a young age.