Taxonomic approaches to and interpretation of host specificity of trematodes of fishes: lessons from the Great Barrier Reef

Abstract

The taxonomy of trematodes of Great Barrier Reef (GBR) fishes has been studied in some detail for over 20 years. Understanding of the fauna has been informed iteratively by approaches to sampling, understanding of morphology, the advent of molecular methodology and a feed-back loop from the emergent understanding of host specificity. Here we analyse 658 host-parasite combinations for 290 trematode species, 152 genera and 28 families from GBR fishes. These are reported from 8 orders, 38 families, 117 genera and 243 species of fishes. Of the 290 species, only 4 (1·4%) have been reported from more than one order of fishes and just 23 (7·9%) infect more than one family; 77·9% of species are known from only one genus, and 60% from only one species of fish. Molecular studies have revealed several complexes of cryptic species and others are suspected; we conclude that no euryxenous host distribution should be accepted on the basis of morphology only. The occurrence of individual trematode species in potential hosts is patchy and difficult to predict reliably a priori or explain convincingly a posteriori. These observations point to the need for a vigorous iterative interaction between the accretion of host specificity data and its interpretation.

A review of the Lepocreadiidae (Digenea, Lepocreadioidea) from fishes of the waters around New Caledonia

“…Considering those species reported more than once, the following types of specificity are exhibited (see Miller et al 2011).…”

“…Oioxenous Miller et al (2011), having surveyed the patterns of hostspecificity of digeneans of Great Barrier Reef fishes stated that 'no host euryxenous host distribution should be accepted on the basis of morphology alone' and argued that true euryxenicity is relative rare. One case they recognised was Lepotrema clavatum.…”

Parasites and cleaning behaviour in damselfishes

“…Derogenes pearsoni from damselfishes) and euryxenicity where parasites infect a wide range of hosts (e.g. Aponurus laguncula known from 67 species from 29 fish families) (Miller et al 2011b). …”

“…This species has a widespread distribution and is reported to be highly euryxenic (Bray et al 1993a;Miller et al 2011b). It has been reported from Heron Island in 15 species of Pomacentridae as well as in species of Acanthuridae, Chaetodontidae, Kyphosidae, Lethrinidae, Pomacanthidae, Serranidae and Siganidae (Yamaguti 1938;Manter 1969a;Ichihara 1986;Lester and Sewell 1990;Bray et al 1993a;Barker et al 1994).…”

“…Host specificity of parasites can be classified into three broad categories: oioxenicity, where an individual parasite species is known to only infect a single host species; stenoxenicity, where the parasite infects multiple phylogenetically related species; and euryxenicity, where a species infects a diverse range of hosts united by ecology and physiology rather than taxonomy (Miller et al 2011b). Miller et al (2011b) showed that 60 % of the trematodes then known from the GBR were oioxenic, 32 % were stenoxenic and just 8 % were euryxenic. For the Pomacentridae specifically, Barker et al (1994) found that, of the 18 species of digeneans known from pomacentrids at Heron Island, six [Bivesicula unexpecta , Haplosplanchnidae sp., Lepotrema adlardi (Bray, Cribb & Barker, 1993), Lepotrema sp.…”