HELMINTH ECTOPARASITES OF SILLAGINID FISHES (PERCIFORMES, PERCOIDEI) HAVE LOW SPECIES RICHNESS

Just nineteen species of ectoparasitic helminths were found in a surve y of over 1,500 individuals of 26 species of sillaginid fishes in the Indo-west Pacific. A twentieth worm is known only from the literature; a twenty-first, also known only from the literature, is considered a doubtful record. Fifteen of the twenty worms are branchial monogeneans , one is a monogenean of the pharyngeal plates, one is an ectoparasiti c digenean living under the scales, and three are leeches of the mouth cavity and fins. The most common monogeneans were diplectanids (Diple ctanum spp. and Monoplectanum spp.) and microcotylids (Polylabris spp. ), each with five recently described or redescribed species. Of the re maining monogeneans, three were extremely rare, and two were uncommon. Pseudobivagina sp. and Polynemicola sp. (Microcotylidae) and Pseudemp leurosoma sp. (Ancyrocephalidae) were represented by only a single wor m each from three different hosts (Sillago robusta, S. sihama, and S. ingenuua, respectively). The gyrodactylid Gyrodactylus sp. is widespre ad and was recorded from four species of sillaginids (S. ciliata, S. j aponica, S. schomburgkii and S, sihama). Encotyllabe chironemi Robinso n (Capsalidae) is recorded for the first time from sillaginids, but on ly on S. aeolus. Two additional monogeneans are known from sillaginids only in the literature: Dactylogyrus sp. (Dactylogyridae) is known on ly from cultured S. sihama; the single specimen of Microcotyle sp. (Mi crocotylidae) recorded from Sillaginodes punctata is probably a contam inant, since the haptor was missing. The generalist trematode Transver sotrema licinum Manter (Transversotrematidae) was found for the first time in samples of four species of sillaginids (Sillago analis, S. ing enuua, S. lutra and S. sihama). Three species of piscicolid leeches we re encountered: Austrobdella translucens Badham was common on the fins of three large inshore sillaginids (S. ciliata, S. schomburgkii and S , analis); a single specimen of the generalist species Zeylanicobdella arugamensis De Silva was recovered from S. soringa; and specimens of Z. stellata (Moore) infected S. schomburgkii and S. analis. The divers ity of host-specific worms in Sillaginidae is low compared with those of some other Indo-west Pacific fishes.