Egg-feeding in the freshwater piscicolid leech Cystobranchus virginicus (Annelida, Hirudinea)

Leeches are common terrestrial and aquatic annelids, parasitizing or feeding on a wide range of host taxa. Here we report evidence for an unusual feeding behavior of eggfeeding in the piscicolid leech Cystobranchus virginicus. We identified distended specimens of C. virginicus in the nests of at least 4 different fish species: Campostoma anomalum, Moxostoma carinatum, Moxostoma sp. (either M. anisurum and/or M. breviceps), and Nocomis leptocephalus. We collected a total of 41 leeches from the nests of these host species and documented at least 1 leech in 19 of 55 nests (35%), with many sites containing multiple leeches. Individuals of C. virginicus were not identified feeding on any of the 41 adult specimens ofMoxostoma spp. or the 635 adult specimens ofNocomis leptocephalus examined, and were never found in the absence of active host spawning (26 sites). These results are consistent with individuals ofC. virginicus being an opportunistic or possibly even an obligate egg-feeder, potentially timing their own reproductive activities with the spawning of their fish hosts. The current distribution of C. virginicus has been expanded to include North Carolina, South Carolina, and Tennessee. The potential for leech species to induce mortality in developing fish eggs could be a concern for fish conservation and merits further investigation. Additional key words: Hirudinea, Piscicolidae, Campostoma, Moxostoma, Nocomis Leeches are well-known predators and ectoparasites, displaying a wide variety of feeding strategies. The various feeding structures and diets of leeches are vital to their basic biology and have been used to help determine evolutionary relationships among species (Sawyer 1986). Leeches belonging to the suborder Arhynchobdellida possess buccal cavities containing ridges or toothed jaws. Some species of arhynchobdellid are known to prey upon smaller annelids, devouring them whole, whereas other species parasitize larger organisms by imbibing blood (Sawyer 1986; Davies & Govedich 2001). Leeches in the suborder Rhynchobdellida possess a pharynx modified to form a muscular proboscis. Some members of this group parasitize vertebrates by draining body fluids such as blood, whereas other rhynchobdellid species feed on the soft parts of invertebrate prey. A variety of invertebrate and vertebrate taxa including molluscs (Daniels & Sawyer 1975; Klemm 1975; Sawyer 1986), fish (Paperna & Zwerner 1974; Burreson & Thoney 1991), aquatic birds (Davies & Wilkialis 1981; Oosthuizen & Fourie 1985), reptiles (Ernst 1971; MacCulloch 1981), amphibians (Brockelman 1969; van der Lande & Tinsley 1976), and mammals (Oosthuizen & Davies 1994; Hong et al. 1999) have been identified as hosts for both arhynchobdellid and rynchobdellid species. Leeches have also been known to opportunistically feed on amphibian and fish eggs; however, this feeding strategy is uncommon and is often omitted completely in reviews of leeches (Davies & Govedich 2001). Feeding on amphibian eggs has been documented for the arhynchobdellid leeches Macrobdella decora (Moore 1912, 1923), M. ditetra (Moore 1953; Beckerdite & Corkum 1973), M. diplotertia (Cargo 1960; Turbeville & Briggler 2003), and Philobdella gracilis (Viosca 1962) and the rhynchobdellid leech Desserobdella picta (Brockelman 1969). The rhychobdellid leech Invertebrate Biology 124(1): 50–56. r 2005 American Microscopical Society, Inc. a Author for correspondence. E-mail: [email protected] b Present address: Cornell University, Ithaca, NY 14853,