Population genomics of introduced Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in the Democratic Republic of the Congo: Repeated introductions since colonial times with multiple sources.

During colonial times, Nile tilapia Oreochromis niloticus (Linnaeus, 1758) was introduced into non-native parts of the Congo Basin (Democratic Republic of the Congo, DRC) for the first time. Currently, it is the most farmed cichlid in the DRC, and is present throughout the Congo Basin. Although Nile tilapia has been reported as an invasive species, documentation of historical introductions into this basin and its consequences are scant. Here, we study the genetic consequences of these introductions by genotyping 213 Nile tilapia from native and introduced regions, focusing on the Congo Basin. Additionally, 48 specimens from 16 other tilapia species were included to test for hybridization. Using RAD sequencing (27,611 single nucleotide polymorphisms), we discovered genetic admixture with other tilapia species in several morphologically identified Nile tilapia from the Congo Basin, reflecting their ability to interbreed and the potential threat they pose to the genetic integrity of native tilapias. Nile tilapia populations from the Upper Congo and those from the Middle-Lower Congo are strongly differentiated. The former show genetic similarity to Nile tilapia from the White Nile, while specimens from the Benue Basin and Lake Kariba are similar to Nile tilapia from the Middle-Lower Congo, suggesting independent introductions using different sources. We conclude that the presence of Nile tilapia in the Congo Basin results from independent introductions, reflecting the dynamic aquaculture history, and that their introduction probably leads to genetic interactions with native tilapias, which could lower their fitness. We therefore urge avoiding further introductions of Nile tilapia in non-native regions and to use native tilapias in future aquaculture efforts.

Polylabris lingaoensis sp. n. and Polylabris cf. mamaevi Ogawa et Egusa, 1980 (Monogenoidea: Microcotylidae) from perciform fishes in the Gulf of Tonkin, South China Sea.

Polylabris lingaoensis sp. n. is described from the gills of the bald glassy, Ambassis gymnocephalus (Chandidae), from the Gulf of Tonkin (South China Sea), near Lingao, Hainan Province, China. The new species is characterized by a midventral vaginal pore, comparatively few (5-7) testes, and 2 parallel rows each comprised of 30-43 microcotylid clamps in the haptor. Polylabris lingaoensis is the only member of the genus known to parasitize a chandid host. Polylabris cf. mamaevi is described from the gills of the mottled spinefoot, Siganus fuscescens (Siganidae), from the South China Sea, which represents new host and locality records for the helminth. The gill parasites from S. fuscescens are tentatively assigned to P. mamaevi pending new collections and restudy of microcotylid species from siganid fishes.

Diplectanids infesting the gills of the barramundi Lates calcarifer (Bloch) (Perciformes: Centropomidae), with the proposal of Laticola n. g. (Monogenoidea: Diplectanidae).

Four species of the Monogenoidea, Laticola lingaoensis n. sp., L. latesi (Tripathi, 1957) n. comb. [previously Pseudorhabdosynochus latesi (Tripathi, 1957) Kritsky & Beverley-Burton, 1986], L. paralatesi (Nagibina, 1976) n. comb. [previously Diplectanum paralatesi Nagibina, 1976] and Diplectanum penangi Liang & Leong, 1991, are reported from the gills of Lates calcarifer (Centropomidae) from the South China Sea (new geographical records for L. latesi and D. penangi). Collections from off Bathurst Island, Northern Territory, Australia, represent a new geographic record for L. paralatesi; Chilka Lake, Orissa, India, is established as the type-locality for L. latesi. Laticola n. g. (Diplectanidae) is proposed for species with a spoon-shaped copulatory organ with two to four concentric incomplete ridges in the base. Laticola lingaoensis, the type-species of Laticola, is described, and L. latesi and L. paralatesi are redescribed based on specimens from the South China Sea. Pseudorhabdosynochus monosquamodiscusi Balasuriya & Leong, 1995 and Pseudorhabdosynochus yangjiangenesis Wu & Li, 2005 are considered junior subjective synonyms of L. latesi and L. paralatesi, respectively.

Pseudorhabdosynochus summanoides n. sp. (Monogenea: Diplectanidae) from Epinephelus coioides in Dapeng Bay, South China Sea, with observations on several similar species of Pseudorhabdosynochus Yamaguti, 1958.

One new species of diplectanid monogenean, Pseudorhabdosynochus summanoides n. sp., is reported and described from the marine fish Epinephelus coioides off Nan'ao Shenzhen, China. P. summanoides differs from its closest relative, P. summanae (Young, 1968), by the shape of its vaginal hard-parts, which have a tightly twisted distal region and an accessory patch on the proximal curve. During the course of this work, type-material of several species of Pseudorhabdosynochus was examined and aspects of the vagina and haptor are redescribed and/or figured. These species include P. americanus (Price, 1937), P. hargisi (Oliver & Paperna, 1984), P. amplidiscatus (Bravo-Hollis, 1954), P. epinepheli (Yamaguti, 1938), P. riouxi (Oliver 1986), P. melanesiensis (Laird, 1958), P. cupatus (Young, 1969), P. bocquetae (Oliver & Paperna, 1984), P. kritskyi Dyer et al., 1995, P. capurroi Vidal-Martinez, 1998, P. querni (Yamaguti, 1968) and P. summanae (Young, 1969). Several closely related species are considered in terms of their conspecificity: P. hargisi is proposed as a junior synonym of P. americanus; P. capurroi is suggested as a likely synonym of P. kritskyi; and it is suggested that P. cupatus and P. bocquetae may eventually be demonstrated to be consepcific with P. melanesiensis.

Revision of Allobenedenia Yamaguti, 1963 (Monogenoidea: Capsalidae) with the description of A. zhangi n. sp. from Epinephelus fasciatus (Teleostei: Serranidae) in the South China Sea.

Allobenedenia Yamaguti, 1963 is revised to include capsalid species with five radial septa in the haptor. Megalocotyloides Bychowsky & Nagibina, 1967 and Allosprostonia Lawler & Hargis, 1968 are considered junior synonyms of Allobenedenia. Eight described species comprise the genus: A. convoluta (Yamaguti, 1937) Yamaguti, 1963 (type-species), A. epinepheli (Bychowsky & Nagibina, 1967) n. comb., A. patagonica (Evdokimova, 1969) n. comb., A. pedunculata Raju & Rao, 1980, A. pseudomarginata (Bravo-Hollis, 1958) n. comb., A. sebastodi (Egorova, 1994) n. comb., A. yamagutii (Egorova, 1994) n. comb. and A. zhangi n. sp. A. ishikawae (Goto, 1894) Yamaguti, 1963 is considered a species inquirenda; Megalocotyloides hongkongensis Wu, Lu & Woo, 2002 is placed in synonymy with A. yamagutii; M. grandiloba (Paperna & Kohn, 1964) Egorova & Aleshkina, 1984 is provisionally returned to Megalocotyle as M. grandiloba Paperna & Kohn, 1964; and specimens identified as M. grandiloba from Serranus cabrilla (Serranidae) by Buhrnheim et al. (1973) are considered an undescribed species of Allobenedenia. A. zhangi n. sp. is described from the external surface of Epinephelus fasciatus (Serranidae) of Allobenedenia. A. zhangi n. sp. is described from the external surface of Epinephelus fasciatus (Serranidae) in the South China Sea and is characterised by having an elongtate proximally uncoiled male copulatory organ extending to near the level of the anterior margin of the ovary, a large prostatic reservoir apparently external to the male copulatory canal, and a submedial protuberance on the dorsal surface of the accessory sclerite of the haptor.

A list of monogeneans from Chinese marine fishes.

This paper contains a brief history of studies on monogeneans of Chinese marine fishes and a list of 337 monogenean species, together with their marine hosts and notes on the sea in which they were found. An additional 139 species have been added to the 198 species recorded in 'Monogeneans of Chinese Marine Fishes' published by Zhang, Yang and Liu in 2001.