Monogeneans of the speckled blue grouper, Epinephelus cyanopodus (Perciformes, Serranidae), from off New Caledonia, with a description of four new species of Pseudorhabdosynochus and one new species of Laticola (Monogenea: Diplectanidae), and evidence of monogenean faunal changes according to the size of fish

Abstract

Nine species were identified among 1500 monogeneans collected on the gills of 17 speckled blue groupers, Epinephelus cyanopodus, caught off New Caledonia, South Pacific. A new method for describing squamodiscs in tables is proposed. Diplectanids included one new species of Laticola, which was the most abundant species, and six species of Pseudorhabdosynochus, including four new species, which were differentiated mainly on the basis of morphology of the sclerotised vagina. Laticola cyanus n. sp. is characterised by its genital organs. Pseudorhabdosynochus cyanopodus n. sp. and P. podocyanus n. sp. both have a vagina with a large primary chamber. Pseudorhabdosynochus chauveti n. sp. has a vagina with a long, coiled primary canal. Pseudorhabdosynochus exoticus n. sp. has an aberrant discoid vagina and characters (tip of quadriloculate organ, lateral bar with hook), which differentiate it from all other species. The fivepreviously cited species are strictly specific to E. cyanopodus and were abundant in large (>585 mm) fish. In addition, Haliotrema sp. (Ancyrocephalidae) and Allobenedenia sp. (Capsalidae), both undescribed, were also found on large fish. Pseudorhabdosynochus duitoe Justine, 2007 and P. huitoe Justine, 2007, were collected in very small numbers, mainly in young (345–500 mm) fish; the type-host of these two species is the highfin grouper, E. maculatus, and their occurrence on E. cyanopodus was considered accidental and due to habitat overlap between the young speckled blue groupers and adult highfin groupers. It is hypothesized that the speckled blue groupers are infested by their own, strictly specific monogeneans, only when they encounter older members of their species during spawning aggregations. Spawning aggregations thus play a key role in infestation of coral reef fish by their monoxenic parasites such as monogeneans. Lists are given for other parasites of the speckled blue grouper, including digeneans, cestodes, nematodes, isopods and copepods, with new records from New Caledonia: 41 species of parasites are recorded.