Are all species of Pseudorhabdosynochus strictly host specific? — A molecular study

Abstract

Species of the diplectanid monogenean genus Pseudorhabdosynochus are strictly host-specific (specialist), with the exception of P. cyanopodus, which was reported in New Caledonia, South Pacific, from two host species, Epinephelus cyanopodus and E. chlorostigma. We sequenced the COI gene of both host fish species and of their monogeneans. Morphological identification and pairwise distances showed that the two fish species were distinct (difference 6.1-6.6%), but that their monogeneans were not (difference 0-1.5%). A morphological study of sclerotised parts showed that specimens of P. cyanopodus are similar in both fish. Most species of groupers and their associated Pseudorhabdosynochus species are from warm surface waters, but the two groupers E. cyanopodus and E. chlorostigma are usually caught in deep-sea on the outer slope of the coral reef. This suggests that acquisition of a less strict host specificity is an adaptation of P. cyanopodus to deep-sea hosts.

Pseudorhabdosynochus sulamericanus(Monogenea, Diplectanidae), a parasite of deep-sea groupers (Serranidae) occurs transatlantically on three congeneric hosts (Hyporthodusspp.), one from the Mediterranean Sea and two from the western Atlantic

“…The closest sequence in GenBank according to BLAST was from P. cyanopodus Sigura & Justine, 2008 (Schoelinck, Cruaud & Justine, 2012), a parasite from Epinephelus spp. in the South Pacific.…”

“…More than 80 species of Pseudorhabdosynochus are known; they are generally extremely species-specific, i.e., a species is found only on one species of host (Justine, 2005a; Justine, 2005b; Justine, 2007a; Justine, 2007b; Justine, 2008b; Justine, 2008c; Justine et al, 2010; Justine & Sigura, 2007; Sigura & Justine, 2008); however, Schoelinck, Cruaud & Justine (2012) recently demonstrated, on morphological and molecular bases, that P. cyanopodus occurs on two sympatric species of deep-sea groupers that inhabit the outer slope off the barrier reef of New Caledonia, South Pacific. These are Epinephelus cyanopodus and E. chlorostigma (Schoelinck, Cruaud & Justine, 2012). Those authors hypothesized that low specificity was an adaptation of P. cyanopodus to deep-sea conditions, where hosts are rare and separated by wide areas, and that infesting two species of hosts helps in perpetuating the parasite species (Schoelinck, Cruaud & Justine, 2012).…”

“…These are Epinephelus cyanopodus and E. chlorostigma (Schoelinck, Cruaud & Justine, 2012). Those authors hypothesized that low specificity was an adaptation of P. cyanopodus to deep-sea conditions, where hosts are rare and separated by wide areas, and that infesting two species of hosts helps in perpetuating the parasite species (Schoelinck, Cruaud & Justine, 2012). This hypothesis was coherent with the observation that the species richness of gill monogeneans is five times higher in surface fish than in deep-sea fish (Rohde, 1988).…”

“…Recently, it was shown that two groupers from off New Caledonia shared the same species of Pseudorhabdosynochus . This was interpreted as the result of adaptation to deep sea by the monogenean because lower specificity helps transmission of the parasites in the deep-sea environment, where hosts are rarer than in coral seas (Schoelinck, Cruaud & Justine, 2012). This finding echoed previous results of lower biodiversity of monogeneans in deep-sea fish compared to surface fish (Rohde, 1988).…”

Two new species of nematode parasites, Cucullanus epinepheli sp. n. (Cucullanidae) and Procamallanus (Spirocamallanus) sinespinis sp. n. (Camallanidae), from marine serranid and haemulid fishes off New Caledonia

“…Although only three specimens of E. chlorostigma were collected off New Caledonia for parasitology, identifications and descriptions of new species were obtained for copepods , digeneans (Bray and Justine 2011, 2013, cestodes (Beveridge et al 2014), monogeneans (Justine and Henry 2010, Schoelinck et al 2012 and nematodes (the present paper).…”