Description of Sinodiplectanotrema malayanum n. sp. (Monogenea: Diplectanidae), with comments on the taxonomic position of the genus

A new genus for Diplectanum setosum Nagibina, 1976 (Monogenea: Dipletanidae), a parasite of Psammoperca waigiensis (Cuvier) (Perciformes: Latidae) from Okinawa-jima Island, Japan

The diplectanid monogenean Diplectanum setosum Nagibina, 1976 is redescribed based on newly collected specimens from Psammoperca waigiensis (Cuvier) (Perciformes: Latidae) from the Okinawa-jima Islands, Okinawa Prefecture, Japan, and transferred to a new genus, Latiphagum n. g., herein proposed based on the results of the morphological and molecular analysis. This new genus is closely related with Pseudorhabdosynochus Yamaguti, 1958, Echinoplectanum Justine & Euzet, 2006, and Laticola Yang, Kritsky, Sun, Zhang, Shi, & Agrawal, 2006, but distinguished from them by the male copulatory organ (MCO) of the new genus devoid of cirrus, the tube supported both sides by two plates with long bristles, and the presence of the prostatic reservoir in the expanded base of the MCO.

Neither Diplectanum nor specific: a dramatic twist to the taxonomic framework of Diplectanum (Monogenea: Diplectanidae)

The taxonomy of the genus Diplectanum has been exclusively based on morphological features, with 28 nominal species parasitic on perciform fishes recognised. We used molecular data, to our knowledge for the first time, to evaluate the taxonomic framework of Diplectanum, infer the relationships amongst species attributed to this genus, re-assess the degree of host specificity and explore the population genetic structure of Diplectanum spp. parasitising Mediterranean sciaenids, which are potential target fish species for aquaculture diversification in the region. A minimum of 10 specimens of Diplectanum spp. were sequenced per host species (Argyrosomus regius, Sciaena umbra, Umbrina canariensis and Umbrina cirrosa) and locality (Burriana, Sant Carles de la Ràpita and Santa Pola (Spain)) together with five individuals of the type species Diplectanum aequans. Sequences of partial 28S rDNA and internal transcribed spacer region of Diplectanum spp. were analysed together with those from other Diplectanidae spp. in GenBank using Bayesian inference and maximum likelihood phylogenetic methods. Population genetic analyses were performed using cytochrome c oxidase subunit I gene sequences for a diplectanid species with a wide distribution across host species and localities. Results showed that Diplectanum was not monophyletic, nor were the specimens infecting sciaenids. Instead they formed two separate clades, 26.1-28.6% divergent for the internal transcribed spacer and 13.2-16.9% for the 28S region from D. aequans. Altogether, our results suggest that these specimens represent two distinct new genera from Diplectanum and five putative species with low host specificity. It is likely that morphological variability has led to the description of more species than were detected by molecular methods. In contrast to other monogeneans, Diplectaninae gen. spp. are chiefly generalists. Nonetheless, intraspecific genetic divergence in the internal transcribed spacer region of Diplectaninae gen. spp., and population genetic analyses of one presumed generalist species, Diplectaninae gen. sp. 1.2, showed significant variation between subpopulations living on different hosts. The intraspecific genetic structure by host also suggests different cross-infection potential amongst sciaenid species.

Gyrodactylus medaka n. sp. (Monogenea: Gyrodactylidae) parasitic on wild and laboratory-reared medaka Oryzias latipes (Beloniformes: Adrianichthyidae) in Japan

Gyrodactylus medaka n. sp. (Monogenea: Gyrodactylidae) is described from the skin, fins, and gills of medaka Oryzias latipes (Beloniformes: Adrianichthyidae) from Japan. This new species was collected from wild medaka in Hiroshima, Aichi, Saga, and Kumamoto prefectures, and laboratory-reared medaka in Chiba and Aichi prefectures. The small marginal hook sickle (≤4 μm) and the length of the marginal hook of the new species are the diagnostic morphological characters differentiated from other gyrodactylids reported from Asia. The pairwise sequence divergences for the interspecific variation in ITS regions and the phylogenetic analysis suggest that the populations of G. medaka n. sp. may have a similar genetic variation as the medaka populations in Japan. Gyrodactylus medaka n. sp. and Dactylogyrus oryziasi (Monogenea: Dactylogyridae) can maintain their populations in laboratory aquaria using medaka as their hosts, and these monogeneans and medaka have the potential as experimental model animals for clarifying various aspects of their host-parasite relationships. In addition, we report the composition of modified ammonium picrate-glycerin (APG) and show it is advantageous for monogenean taxonomy.

A new species of Furcohaptor Bijukumar & Kearn, 1996 (Monogenea: Diplectanidae) parasitic on Cynoglossus robustus Günther (Pleuronectiformes: Cynoglossidae) in the Seto Inland Sea, Japan, with comments on its systematic position and an amended generic diagnosis of Furcohaptor

Furcohaptor brevis n. sp. is described from the gills of Cynoglossus robustus Günther caught in the Seto Inland Sea off Hiroshima Prefecture, Japan. Although Furcohaptor Bijukumar & Kearn, 1996 has been assigned to the Ancyrocephalinae Bychowsky, 1937 in the Dactylogyridae Bychowsky, 1933, this genus is transferred to the Diplectaninae Monticelli, 1903 in the Diplectanidae Monticelli, 1903 based on both morphological and molecular data. An amended generic diagnosis is provided.