Species of Pseudorhabdosynochus Yamaguti, 1958 (Monogenea: Diplectanidae) from Epinephelus fasciatus and E. merra (Perciformes: Serranidae) off New Caledonia and other parts of the Indo-Pacific Ocean, with a comparison of measurements of specimens prepared using different methods, and a description of P. caledonicus n. sp.

Abstract

Species of Pseudorhabdosynochus were studied from fresh specimens collected from Epinephelus fasciatus and E. merra off New Caledonia, South Pacific, and specimens deposited in Museums. Experiments on two species demonstrated that the sclerotised hollow organs, such as the quadriloculate male copulatory organ and the vagina, may show differences in measurements of up to 50% when flattened. P. caledonicus n. sp. is described from E. fasciatus in New Caledonia, on which it is relatively rare; it is distinguished on the basis of the quadriloculate organ, which has a very thin anterior wall, the sclerotised parts of the vagina in form of a straight tube with a star-shaped lateral structure, and the squamodiscs composed of 11 open rows of rodlets. P. cupatus (Young, 1969) is redescribed from abundant material from E. fasciatus off New Caledonia (new geographical record) and compared with paratype specimens from Australia (from E. fasciatus and E. merra) and specimens from E. fasciatus in the Red Sea (both herein redescribed and figured); a specimen was also found on a slide from E. merra off Vanuatu. P. melanesiensis (Laird, 1958) is redescribed from material from E. merra off New Caledonia (new geographical record) and compared with type-specimens (herein redescribed and figured) from the same host off Vanuatu. The structure of the sclerotised vagina in P. cupatus and P. melanesiensis is very similar, with a thin-walled tube and a heavily sclerotised structure with three loculi. P. vagampullum (Young, 1969) is redescribed from the paratypes from E. merra from Australia, but was not found in New Caledonia; specimens included among its paratypes (from E. merra in Australia), but different, are herein attributed to Pseudorhabdosynochus sp. 3. P. lantauensis (Beverley-Burton & Suriano, 1981) is redescribed from the paratype specimens from E. longispinis off Hong-Kong. A specimen found among the paratypes of P. cupatus belongs to a different species, herein designated as Pseudorhabdosynochus sp. 1. Specimens from E. longispinis off Hong-Kong, previously attributed to P. cupatus, are attributed to another species, Pseudorhabdosynochus sp. 2. The three species P. cupatus, Pseudorhabdosynochus sp. 1 and Pseudorhabdosynochus sp. 2 have in common a 'lamellosquamodisc' composed of central telescopic lamellae and peripheral rows of rodlets; they can be distinguished by the shape of the sclerotised vagina and measurements of the haptoral hard-parts. Specimens from E. longispinis off Hong-Kong, previously attributed to P. vagampullum, probably belong to a different species. Consequently, after these modified determinations, P. cupatus parasitises only E. fasciatus and E. merra, and P. melanesiensis and P. vagampullum parasitise only E. merra. With their wide geographical distribution and different species of Pseudorhabdosynochus in different localities, E. fasciatus and E. merra appear to represent excellent models for investigating monogenean biogeography in the Indo-Pacific Ocean.

Resolution of the discrepant host-specificity of Pseudorhabdosynochus species (Monogenea, Diplectanidae) from serranid fishes in the tropical Indo-Pacific

“…Drawings were scanned and redrawn on a computer with Adobe Illustrator. Measurement methods for haptoral hard parts were summarized in Justine (2005a, Fig. 1) and Justine (2007, Fig .…”

“…All measurements are given in micrometres. Measurements of monogeneans significantly vary with the degree of flattening (Justine 2005a(Justine , 2009; comparisons between various samples took this factor in consideration.…”

“…Ventral hamulus outer length 53, inner Justine (2005a). Zeng and Yang (2007) redescribed the species from E. quoyanus from the South China Sea and described the secondary chamber (as 'star-shaped lateral structure').…”

“…Justine (2005a) considered the monogenean material in USNPC slide 07725 deposited by Beverley-Burton and Suriano to belong to another species. Justine (2009) concluded that host misidentification and erroneous slide labelling in this material suggest that the real host could be E. quoyanus.…”

“…Pseudorhabdosynochus cupatus was originally described from Epinephelus merra Bloch (type-host) and E. fasciatus Forsskål (other host). In E. merra in New Caledonia, Justine (2005a) and Hinsinger and Justine (2006b) did not find P. cupatus but found abundant P. melanesiensis (Laird, 1958) Kritsky et Beverley-Burton, 1986, a species originally described from this fish species in Vanuatu and Fiji (Laird 1958); in E. fasciatus in New Caledonia they found a diplectanid that they considered conspecific with P. cupatus. Pseudorhabdosynochus vagampullum, also described from E. merra, was never found in New Caledonia (Justine 2005a, Hinsinger andJustine 2006b).…”