Helminth ectoparasites of sillaginid fishes (Perciformes: Percoidei) have low species richness

Just nineteen species of ectoparasitic helminths were found in a survey 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 ectoparasitic digenean living under the scales, and three are leeches of the mouth cavity and fins. The most common monogeneans were diplectanids (Diplectanum spp. and Monoplectanum spp.) and microcotylids (Polylabris spp.), each with five recently described or redescribed species. Of the remaining monogeneans, three were extremely rare, and two were uncommon. Pseudobivagina sp. and Polynemicola sp. (Microcotylidae) and Pseudempleurosoma sp. (Ancyrocephalidae) were represented by only a single worm each from three different hosts (Sillago robusta, S. sihama, and S. ingenuua, respectively). The gyrodactylid Gyrodactylus sp. is widespread and was recorded from four species of sillaginids (S. ciliata, S. japonica, S. schomburgkii and S. sihama). Encotyllabe chironemi Robinson (Capsalidae) is recorded for the first time from sillaginids, but only on S. aeolus. Two additional monogeneans are known from sillaginids only in the literature: Dactylogyrus sp. (Dactylogyridae) is known only from cultured S. sihama; the single specimen of Microcotyle sp. (Microcotylidae) recorded from Sillaginodes punctata is probably a contaminant, since the haptor was missing. The generalist trematode Transversotrema licinum Manter (Transversotrematidae) was found for the first time in samples of four species of sillaginids (Sillago analis, S. ingenuua, S. lutea and S. sihama). Three species of piscicolid leeches were 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 diversity of host-specific worms in Sillaginidae is low compared with those of some other Indo-west Pacific fishes.