Ecological interaction of a “parasitic” candiru catfish and botos (Inia geoffrensis): ARAÚJO-WANG ET AL.: CANDIRU CATFISH AND BOTOS

The range of ecological interactions of the boto (Inia geoffrensis), an obligate freshwater dolphin of South America, is poorly known. We describe a new interaction between botos and small candiru catfish (genus Ochmacanthus), and their possible relationships. Candirus were photographed on at least 29 different botos. The minimum number of candirus per boto varied greatly from 1 to >230 (mean = 16.3, SD = 39.4, mode = 1). Our observations showed that candiru-boto interactions occur commonly year-round. Two types of ecological interaction may be occurring: parasitism (trophic) or phoresy (nontrophic). Although candirus are generally known as parasites, the candiru-boto relationship does not appear to fulfill several characteristics of a typical parasitic interaction. Thus, the candiru-boto relationship is most likely phoretic in nature. A shift in candiru trophic strategy may occur depending on the victim (botos or fish) and on the spatial scale, and human activities may influence the nature of these complex ecological interactions.