Tetsuji Nakabo

Extensive hybridization and associated geographic trends between two rockfishes Sebastes vulpes and S. zonatus (Teleostei: Scorpaeniformes: Sebastidae).

Interspecific hybridization is an important evolutionary process, which has significant influence on the diversity within and between participating taxa. Although interspecific hybridization in terrestrial and freshwater organisms has been subjected to many detailed studies, studies in marine realm have been limited in terms of both numbers and detail. In this study, the potential for interspecific hybridization between two rockfishes, Sebastes vulpes and S. zonatus, occurring in the western North Pacific, was assessed on the basis of 177 specimens collected from three sampling localities within the main geographic distribution of both species, and analysed using a combination of amplified fragment length polymorphisms (AFLP), mitochondrial DNA (mtDNA) markers and morphometric characters. Bayesian‐based individual genetic assignment based on 364 AFLP loci detected a total of 63 (35.6%) hybrid specimens in the data set, the presence of interspecific hybrids also being rigorously supported by mtDNA analysis using partial sequences from the control region and morphological analysis based on 31 morphometric characters. Hybrids from all three localities were found, showing a common pattern of biased introgression across the localities whereby hybrids were more closely related to S. zonatus than to S. vulpes. Apart from this common pattern, rates of hybridization varied considerably among the localities, being greater in the northern localities. Variations in the local rates of hybridization were associated with variations in habitat segregation and thermal regime, implying that vertical water temperature regimes determined the extent of habitat segregation of the two species and, accordingly, the opportunity for hybridization.

Taxonomic review of East Asian Pleuronichthys (Pleuronectiformes: Pleuronectidae), with description of a new species

A review of East Asian frog flounders, genus Pleuronichthys (family Pleuronectidae), recognized Pleuronichthys japonicus sp. nov. and P. cornutus (Temminck and Schlegel 1846). Pleuronichthys japonicus sp. nov. is characterized by small, dark, rounded spots or marbled markings on the ocular side of the body, rounded cycloid scales somewhat irregularly arranged, usually 12 abdominal vertebrae, 67–80 (modally 75) dorsal-fin rays, 48–59 (modally 55) anal-fin rays, and a short branch of the supratemporal lateral line usually present on both sides. Pleuronichthys cornutus is characterized by densely distributed small, dark, irregular spots on the ocular side of the body, elongate cycloid scales somewhat regularly arranged, usually 13 abdominal vertebrae, 72–88 (modally 77) dorsal-fin rays, 52–65 (modally 58) anal-fin rays, and a branch of the supratemporal lateral line usually absent on both sides. Whereas P. cornutus is distributed from Miyagi Prefecture (Tohoku District) southward along the Pacific coast of Japan to the Bungo Channel, from Akita Prefecture (Tohoku District) southward along the Sea of Japan coast through the Tsushima Strait to the East China Sea, Yellow and Bohai Seas, the Taiwan Strait, and northern Chinese coast of the South China Sea, P. japonicus is distributed from southern Hokkaido southward along the Sea of Japan and Pacific coasts of Japan to the southern East China Sea. Geographic variations were found in caudal vertebrae and anal-fin ray counts, and caudal-peduncle depth in P. cornutus, and in ocular side body coloration, body depth, and head length in P. japonicus. Pleuronichthys lighti Wu 1929 was regarded as a junior synonym of P. cornutus.

Distinct genetic isolation between “Kunimasu” (Oncorhynchus kawamurae) and “Himemasu” (O. nerka) in Lake Saiko, Yamanashi Prefecture, Japan, inferred from microsatellite analysis

The possibility of interspecific hybridization between Kunimasu (Oncorhynchus kawamurae) and Himemasu (Oncorhynchus nerka) was investigated in a large number of specimens, in a search for basic data relevant to conservation needs. A Bayesian-based clustering method using five microsatellite DNA loci separated 144 specimens from Lake Saiko, Yamanashi Prefecture, into two genetically distinct groups, corresponding to Kunimasu and Himemasu. Application of a threshold of individual proportion of membership of 0.90, so as to separate hybrids from purebreds, resulted in all specimens except two having high probability of purebred. These results implied that Kunimasu and Himemasu have been maintained as independent genetic entities in Lake Saiko.

First record of albinism in the rockfish Sebastes pachycephalus complex (Scorpaeniformes : Scorpaenidae)

Albinism, a condition resulting from a group of genetically determined disorders of the melanin pigmentary system (Kinnear et al. 1985), occurs in two forms: (1) complete albinism, which is phenotypically expressed as a lack of integumentary and retinal melanin, indicating defects in the integumentary and retinal melanophores, and (2) partial albinism or leucism. The latter describes an individual with reduced or absent integumentary pigment, but with pigmented retinas, resulting in diminished or no body coloration and darkly pigmented eyes. Primarily used in herpetological literature, the term leucism has recently been suggested as appropriate for ichthyology (Clark 2002). Complete albinism and leucism have been reported in numerous teleost species (e.g., Follett and Dempster 1966; Huzita and Nishino 1966; Dawson 1967; Shinohara and Amaoka 1993; Delgado et al. 2009; Mansur 2011; Pillai and Somvanshi 2011), as well as among chondrichthyans (e.g., Talent 1973; Ishihara et al. 2001; Bottaro et al. 2005; Sandoval-Castillo et al. 2006; Reum et al. 2008; Veena et al. 2011). However, in rockfishes of the genus Sebastes Cuvier 1829, only one record of albinism has been documented to date [Follet and Dempster 1966, as Sebastodes melanostomus (Eigenmann and Eigenmann 1890)], an unusual example of leucism, termed ‘‘melanalbinism’’ by the authors. On 28 February 2012, a single leucistic individual of Sebastes pachycephalus complex was captured alive in a basket trap in Kamaishi Bay, Iwate Prefecture, Japan (Fig. 1). A brief description of the specimen is given below. Morphological characters were examined following Muto et al. (2011) except for the lower jaw length, which was taken as the distance between the symphysis and the posteriormost point of the dentary, after fixation in 10 % formalin and preservation in 70 % ethanol. Terminology of the head spines follows Randall and Eschmeyer (2001). Counts and measurements were taken from the right side of the body, the left side having been damaged. The specimen was deposited in the Kyoto University Fish Collection (FAKU). Description (based on FAKU 134960, 245.3 mm in standard length). The following measurements are expressed as percentage of standard length: head length 41.3; snout length 10.5; orbital length 8.6; postorbital length 22.6; upper jaw length 18.3; lower jaw length 16.6; body width 25.6; caudal peduncle depth 12.1; preanal length 68.2; predorsal length 32.7; prepelvic length 46.9; longest dorsal-fin spine (both fourth and fifth) length 15.3; longest dorsal-fin soft ray (fourth) length 16.4; first anal-fin This article was registered to the Official Register of Zoological Nomenclature (ZooBank) as DE8B323D-8BC9-4B36-90D5-6F3EC46CACE5. This article was published as an Online First article on the online publication date shown on this page. The article should be cited by using the doi number.

Hongeo, a new skate genus (Chondrichthyes: Rajidae), with redescription of the type species

Hongeo gen. nov. is proposed following examinations of several individuals, including adult males, of the type species Raja koreana, previously described from a single adult female specimen from the southern coast of the Korean Peninsula. A number of external (including claspers, squamation, and ampullary and lateral line canal systems) and skeletal characters are newly described. The phylogenetic position of R. koreana among 26 nominal rajid supraspecific taxa plus 2 unnamed supraspecific taxa of Rajidae and 3 outgroups was estimated. According to a strict consensus tree of 20 equally parsimonious trees of 139 steps (CIxa0=xa00.626; RIxa0=xa00.850; RCxa0=xa00.532; HIxa0=xa00.374), Hongeo gen. nov. is defined by the two derived character states: rostral cartilage continuous with neurocranium and stout proximally, but very slender and uncalcified distally; and anterior fontanelle broad, extending forward onto the basal part of rostral cartilage slightly beyond the leading edge of nasal capsules. The new genus also differs from all other supraspecific taxa of Rajidae in the following combination of characters: dorsal surface of tail with a row of distinct thorns along midline in both sexes; most thorns directed anteriorly; a pair of longitudinally elongated black blotches having undulated contours on middle of dorsal surface of disc; three groups of outer buccal ampullae and tubules; three groups of nasal ampullae and tubules; hyoidean ampullae and tubules on ventral surface posteriorly extending past cloaca; rostral shaft narrow with filamentous cartilage at base; scapulocoracoid comparatively short and high with dorsoventrally elliptical anterior fenestra and expanded postventral fenestra; external margin of mesopterygium of pectoral fin slightly undulated, not sinuous, and not fused with pectoral radials; and clasper component eperon and pent present.

Taxonomic review of the genus Cottiusculus (Cottoidei: Cottidae) with description of a new species from the Sea of Japan

A taxonomic review of the cottid genus Cottiusculus Jordan and Starks 1904 established three species, C. nihonkaiensis sp. nov., C. schmidti, and C. gonez. Cottiusculus nihonkaiensis sp. nov., which had been previously confused with C. schmidti, is described on the basis of 32 specimens (44.8–77.9xa0mm, SL) collected from the Sea of Japan. The new species is very similar to C. schmidti in having a curved barbless uppermost preopercular spine and the lateral line extending past the caudal fin base, but is distinguishable as follows: nasal spines simple or sometimes weakly bicuspid (vs. deeply bicuspid in C. schmidti); first dorsal fin not elongated in either males or females (vs. elongated in males); ventral lateral and lateral line cirri present (vs. absent). The former is known from the Sea of Japan coasts of Hokkaido, Honshu, Kyushu and the Korean Peninsula, and Volcano Bay, Hokkaido, and the latter from the Pacific coast of Tohoku District, Japan. Cottiusculus gonez, known from the Sea of Japan, Sea of Okhotsk and Pacific coast of Hokkaido, is characterized by having a simple nasal spine, the uppermost preopercular spine almost straight with two small cusps dorsally, posterior cusp barbed, and the lateral line almost reaching to the caudal fin base. A lectotype of C. gonez is designated here. Sequence differences in the cytochrome b gene among the above three species of Cottiusculus are also presented.

Molecular insights into geographic and morphological variation within the Eumicrotremus asperrimus species complex (Cottoidei: Cyclopteridae)

A molecular phylogeny of lumpsukers, Eumicrotremus asperrimus and related species (family Cyclopteridae), is presented on the basis of sequence variations in the cytochrome b and cytochrome c oxidase subunit 1 genes (1,659 base pairs) of mitochondrial DNA using specimens collected from across the North Pacific, including the Sea of Japan, Sea of Okhotsk, Bering Sea, and Gulf of Alaska. Specimens identified as Eumicrotremus phrynoides, Cyclopteropsis bergi, Cyclopteropsis lindbergi, and Lethotremus muticus on the basis of the presence or absence of spiny tubercles and height of the first dorsal fin did not exhibit reciprocal monophyly, but were randomly clustered with E. asperrimus. This collection of forms is therefore referred to as the “E. asperrimus species complex.” DNA sequence data presented here divided the E. asperrimus species complex into two distinct clades, corresponding to the eastern North Pacific (the Bering Sea, Aleutian Islands, and Gulf of Alaska) and the western North Pacific (the Seas of Japan and Okhotsk) regions. Slight morphometric differences between eastern and western clades were also evident, indicating that they represent at least two different species. The genetic level of divergence between the two clades suggests that the speciation event occurred during the early Pleistocene to late Pliocene. Although the presence and morphology of tubercles have been used extensively for species discrimination in Cyclopteridae, our results suggest that this character complex is confounded by intraspecific variation. Examined samples showed some sexual dimorphism in the relative development of the tubercles, although the pattern was different between the eastern and western North Pacific clades. These results underscore the need for a thorough re-examination of the taxonomy of Pacific cyclopterids, using molecular data to supplement potentially misleading tubercle morphology.

Growth-related morphology of “Kunimasu” ( Oncorhynchus kawamurae : family Salmonidae) from Lake Saiko, Yamanashi Prefecture, Japan

Biological characteristics of “Kunimasu” (Oncorhynchus kawamurae), poorly known even before the species was prematurely believed extinct, have now become apparent following the examination of 59 specimens from Lake Saiko, Yamanashi Prefecture, Japan and comparison with 58 examples of “Himemasu” (kokanee of Oncorhynchus nerka in Japan), also from Lake Saiko. Significant (pxa0<xa00.01) differences between Kunimasu and Himemasu from Lake Saiko occurred in counts of anal-fin rays, pectoral-fin rays, gill rakers (no overlap found) and pyloric caeca. Secondary sexual characters related to maturity level were also found in Kunimasu, the body being more compressed in pre-spawning and spawning males and females than in immature and maturing individuals. Furthermore, maturing male Kunimasu and Himemasu also differed in body shape. Body coloration of Kunimasu also differed according to level of maturity, the nuptial coloration in both sexes being olive-green when alive and black when fresh. Dark dots, found in ca. 40xa0% of Kunimasu individuals examined, were less distinct than in Himemasu. The spawning season of Kunimasu extended through winter and early spring in Lake Saiko, with spawning males and females remaining near the bottom, compared with non-spawning individuals which occupied the upper and middle profundal zones in the daytime.

Mitochondrial DNA sequence divergence between “Kunimasu” Oncorhynchus kawamurae and “Himemasu” O. nerka in Lake Saiko, Yamanashi Prefecture, Japan, and their identification using multiplex haplotype-specific PCR

In order to develop a simplified method for discriminating between Oncorhynchus kawamurae (Kunimasu) and sympatric Oncorhynchus nerka (Himemasu), sequence variations of mitochondrial DNA control region were examined on 71 specimens of Kunimasu and 103 of Himemasu. Sequence analyses for 530xa0bp revealed 3 variable sites, which defined three haplotypes in Kunimasu and one in Himemasu. Based on determined nucleotide sequences, species-specific primers were designed for the multiplex haplotype-specific polymerase chain reaction, which amplified ca. 900 and 1,040xa0bp fragments in Kunimasu and Himemasu, respectively. This simple rapid approach can be used to distinguish between the two species without the need to sacrifice specimens.

An underwater photograph of Sphyraena iburiensis (Perciformes: Sphyraenidae) from the Red Sea: first record outside Japanese waters

Sphyraena iburiensis, a small-sized barracuda (family Sphyraenidae) recently described by Doiuchi and Nakabo (2005), belongs to the S. obtusata group sensu Doiuchi and Nakabo (2005), characterized by two gill rakers on the first gill arch. The original description of S. iburiensis was based on the holotype and paratypes collected from Iburi, Kochi Prefecture, with additional paratypes from Kushimoto, Wakayama Pref. and Kawana, Shizuoka Pref., all located on the Pacific coast of southern Japan. Subsequently, a specimen of S. iburiensis was reported from Fukaura, Ehime Pref., Japan by Takagi et al. (2010), although additional records based on underwater photographs include Taketomi Island, Ryukyu Islands, Japan (KPM-NR 12009, taken by J. Nakamoto) and Hachijo Island, Izu Islands, Japan (KPM-NR 91935–91937, taken by S. Kato); the photographs are deposited at the Image Database of Fishes, Kanagawa Prefectural Museum of Natural History (http://research.kahaku.go.jp/zoology/ photoDB/). To date, therefore, S. iburiensis has been considered endemic to Japanese waters, although Sphyraena obtusata and Sphyraena pinguis, also members of the S. obtusata group, are both widely known from the IndoWest Pacific (Doiuchi and Nakabo 2005). In 10 October 2008, an underwater photograph of S. iburiensis (Fig. 1) was taken at Shams Alam reef, Wadi Gimal area, Red Sea coast of Egypt (24 4101800N, 35 0500800E), by the second author (S. B.). This record is the first of S. iburiensis outside Japanese waters; the fishes pictured agree well with the diagnostic characters of the S. obtusata group given by Doiuchi and Nakabo (2005), viz. pored lateral-line scales ca. 81–84; scales below lateral line ca. 10 , orbit diameter ca. 5.5% in standard length, posterior tip of maxilla not reaching anterior margin of eye, anterior tip of lower jaw without a pointed fleshy knob, origin of first dorsal fin well behind that of pelvic fin, and body with two longitudinal stripes on the lateral surface. Among the S. obtusata group, S. iburiensis differs from S. pinguis as follows: two longitudinal stripes, lower stripe running through upper part of pectoral-fin base (a single stripe running above pectoral-fin base in S. pinguis) (Doiuchi and Nakabo 2005). Sphyraena iburiensis differs from S. obtusata in having both longitudinal stripes distinct (somewhat indistinct in S. obtusata), the lower stripe extending to the caudal-fin base just below the lateral line (lower stripe joining lateral line midway between end of second dorsal-fin base and caudal-fin base, extending to middle of caudal-fin base in the latter), in addition to 10 – 11 scales below the lateral line (8 –9 in S. obtusata) (Doiuchi and Nakabo 2005). The individuals in Fig. 1 agree closely with the original description of these characters. Shams Alam reef is a large, semi-enclosed lagoon characterized by sandy areas, seagrass beds, isolated coral reefs and fringing reefs. The pictured individuals were observed at a depth of between 1 and 2 m (over about 3 m). Approximately 20 individuals with total lengths of R. Doiuchi (&) Fisheries Experimental Station, Wakayama Research Center of Agriculture, Forestry, and Fisheries, 1557-20 Kushimoto, Higashimuro-gun, Wakayama 649-3503, Japan e-mail: doiuchi_r0001@pref.wakayama.lg.jp