Acanthogobius

Abstract: Gravid females of two species of philometrid nematodes (Philometridae) were collected from marine perciform fishes in Japanese waters, mainly from the southern Sea of Japan. Based on light microscopy and scanning electron microscopy examinations, the previously described but poorly known species Philometra cryptocentri Yamaguti, 1961 is redescribed from specimens recovered from the abdominal cavity of Acanthogobius flavimanus (Temminck et Schlegel), Pterogobius elapoides (Gunther) and P. zonoleucus Jordan et Snyder (all Gobiidae) (all new host records); the number (14) and arrangement of cephalic papillae in this species are described for the first time. The new species, Philometroides branchiostegi sp. n. from head tissues of Branchiostegus japonicus (Houttuyn) (Malacanthidae), based on a single specimen, is mainly characterized by the embossment of the entire body except for the cephalic end, presence of four submedian pairs of large cephalic papillae of external circle and two small lateral single papillae of internal circle, pair of large papilla-like caudal projections, the oesophagus with a distinct anterior inflation, by a markedly small body (length about 18 mm) and the larvae 306-465 microm long.

Abstract: The genus Acanthogobius of gobiioid fish has been reported for six species from East Asia, and inhabits estuarine and coastal waters. Within this genus, Acanthogobius insularis is an endangered and endemic goby in the Amami-oshima and Okinawa-jima Islands, southern Japan, and its range is restricted to the lowermost course of a few river basins. Basic knowledge on this species is scarce in spite of its vulnerable conservation status. The purpose of this study was to elucidate the life history of A. insularis. Monthly sampling was conducted at five stations in the Taiho River, Okinawa-jima Island, from November 2014 to November 2015. Monthly standard length (SL) distributions were unimodal except in April during the recruiting period, suggesting that A. insularis is an annual species. Analysis of the gonadosomatic index and histological observations of the ovaries revealed that this species spawns from January to May. The beginning of the spawning season seems to be related to a decline in water temperature in December. Growth rates appeared to be lower from April to December and higher in winter months. From monthly collections, A. insularis was found to move upstream with growth, and gather at spawning grounds during the reproductive season. Acanthogobius insularis might be threatened by increasing water temperature due to climate change, since low water temperatures appear to be important for their reproduction and growth. Moreover, habitat diversity, from tidal flats for recruiting grounds to upstream sites with cobbles for spawning, is needed to complete their life cycle, and should be conserved.

Abstract: Thirty three species belonging to twenty genera in the subfamily Gobiinae of Korea were reviewed and key to species and genera were provided. Among them twenty seven species captured during 1985-1987 were examined on the cephalic sensory canal systems for the taxonomic review, and classified into 4 groups based on the presence or absence of the canal and their canal pore patterns. It was confirmed that the pore patterns of preopercular and anterior ocular-scapular canal were important in the diagnosis of gobiid genera or species and in the discussion of the specialized species group. It was considered that the genus of Acentrogobius masago should be transferred to Pseudogobius from Acentrogobius, because A. masago was more similar to P. jausnicus than to A. pflaumi and its congeneric species in their cephalicc sensory canal systems. Some populations of Chaenogobius annularis and Acanthogobius lactipes showed the geographical variations in cephalic pit organs and the number of predorsal scales. The endemic gobiid species was not found the Korean waters, but some species showed a disjunct distributions between the west and the east coast waters in Korea. The south coast was inhabited by the abundant species including twenty seven species of seventeen genera. The genera of Acanthogobius, Chaenogobius, and Chasmichthys were considered to be the common genera in Korean waters.

Abstract: The complete mitochondrial genome of Acanthogobius stigmothonus is first sequenced in this study. This genome was 16,666 bp in size and contained 37 classic genes, including 13 protein-coding genes, 22 transfer RNA genes and two ribosomal RNA genes. The gene organization and nucleotide composition were the same with those found in most other Gobiidae fishes. Among 37 genes, 28 were encoded by the heavy strand, while nine were encoded by the light strand. The total nucleotide composition of this genome was 27.4% for adenine (A), 17.6% for guanine (G), 28.2% for cytosine (C), and 26.8% for thymine (T), with a high A + T content of 54.2%. This study will provide a better understanding of population genetic diversity of A. stigmothonus and offer useful information for future studies concerning Gobiidae mitogenome evolution.