Yukio Iwatsuki

Effects of marine ciliates on survivability of the first-feeding larval surgeonfish, Paracanthurus hepatus: laboratory rearing experiments

The contribution of ciliates as a food source to survival of first-feeding surgeonfish larvae, Paracanthurus hepatus, was examined in rearing experiments. The larvae were exposed to eight treatments; i.e. a tintinnid, Amphorellopsis acuta (1.0 × 104, 5.1 × 103 and 2.2 × 103 cells l−1) and a naked ciliate, Euplotes sp. (1.3 × 104, 8.0 × 103 and 5.0 × 103 cells l−1), plus two controls without ciliates. Highest survival of the larvae over the first 4–8 days was observed in the highest density of A. acuta. Rearing experiments also showed that the survivals of larvae fed with A. acuta were higher than those fed with Euplotes sp. Gut content analyses revealed loricae of A. acuta in the larvae. Although Euplotes sp. (lacking loricae) was never recognized in those larval guts, feeding on Euplotes sp. by larvae was confirmed using the ciliate labeled with fluorescent microspheres, implying that the feeding on naked ciliates by fish larvae has been overlooked. The results strongly suggested that both tintinnid and naked ciliates play important roles as alternative food sources to copepod nauplii by enhancing the survivability of fish larvae, especially those with a smaller mouth.

Genetic differences among three species of the genus Trichiurus (Perciformes: Trichiuridae) based on mitochondrial DNA analysis

The mitochondrial DNA segment encoding the 16S ribosomal RNA (16S rRNA) gene sequence (ca. 600 bp) was compared among Trichiurus sp. 2 (sensu Nakabo, 2002) (obtained from various areas of Japan), T. japonicus Temminck and Schlegel (collected from various localities within Japan), and true T. lepturus Linnaeus (caught off the Atlantic coast of the United States and Brazil) of the family Trichiuridae using 10, 10, and 15 specimens, respectively. Based on phylogenetic analysis using a neighbor-joining (NJ) algorithm, the haplotypes of Trichiurus sp. 2, T. japonicus, and T. lepturus indicated three distinct monophyletic lineages, being supported by 100% bootstrap values with no haplotypes overlapping or sharing among the lineages. Trichiurus sp. 2, T. japonicus, and T. lepturus are genetically different from each other, suggesting that they are three distinct species.

The Leiognathus splendens complex (Perciformes: Leiognathidae) with the description of a new species, Leiognathus kupanensis Kimura and Peristiwady

Taxonomic analysis of a group of morphologically similar ponyfishes (Perciformes: Leiognathidae) establishes the Leiognathus splendens complex comprising four valid species: L. jonesi James, 1971, widely distributed in the Indo-West Pacific, from Mauritius to Papua New Guinea, north to Hainan I. (China), and south to Brisbane, Australia; L. kupanensis sp. nov., currently known only from Kupang, Timor, Indonesia; L. rapsoni Munro, 1964, currently known only from India, Indonesia, and Papua New Guinea, and L. splendens Cuvier, 1829, widely distributed in the eastern Indian and western Pacific oceans, from India to Papua New Guinea, and from southern Japan to northern Australia. The L. splendens complex can be defined by the following combination of characters: body depth 42–60% of standard length; mouth protruding downward; slender, minute teeth uniserially on jaws; lower margin of orbit above the horizontal through the gape when mouth closed; breast almost completely scaled; lateral line complete, and a dark blotch on top of spinous dorsal fin. Diagnostic characters of the members are as follows: L. jonesi—anterior dorsolateral body surface with a semicircular naked area on nape, and a paler dark blotch on spinous dorsal fin; L. kupanensis—anterior dorsolateral body surface widely naked; L. rapsoni—cheek scaled; L. splendens—anterior dorsolateral body surface completely scaled and a jet black blotch on spinous dorsal fin.

Revision of the Indo-West Pacific polynemid fish genus Eleutheronema (Teleostei: Perciformes)

Abstract A taxonomic revision of the polynemid fish genus Eleutheronema, which is redefined, resulted in three species of the genus being regarded as valid: Eleutheronema rhadinum (Jordan and Evermann, 1902), having to date been treated as a junior synonym of E. tetradactylum (Shaw, 1804) and currently known only from East Asia (China and Japan) where it is endemic; E. tetradactylum, a senior synonym of both Polynemus teria Hamilton, 1822 and Polynemus coecus Macleay, 1878, being a widely distributed Indo-West Pacific species, which ranges from the Persian Gulf to Australia; and E. tridactylum (Bleeker, 1845), distributed in Southeast Asia (Thailand, Malaysia, and Indonesia). Eleutheronema tridactylum is easily distinguished from both E. rhadinum and E. tetradactylum owing to the vomer lacking tooth plates in the former [vs. vomer with 2 deciduous tooth plates (in specimens at least over ca. 70 mm SL) in the latter] and lower counts of pectoral filaments (free lower rays, 3 vs. 4) and gill rakers [mode 8 (range 4–10) vs. 12 (10–17) and 13 (6–18) in E. rhadinum and E. tetradactylum, respectively]. Eleutheronema rhadinum clearly differs from E. tetradactylum in having higher counts of pored lateral line scales [mode 95 (range 82–95) vs. 73 (71–80) in the latter] and higher scale counts above and below the lateral line [12 (11–14) and 16 (15–17), respectively, vs. 10 (9–12) and 14 (13–15), respectively]. Furthermore, E. rhadinum is distinguished from E. tetradactylum by having a dense black pectoral fin [vs. vivid yellow in life (except in specimens over ca. 350 mm SL, pectoral fin dusky-yellow) in the latter]. Intraspecific variations and morphological changes with growth of the three species are also discussed.

Redescription ofpolydactylus macrochir (günther, 1867), a senior synonym ofP. sheridani (macleay, 1884) (perciformes: Polynemidae)

Polydactylus macrochir (Günther, 1867), for many years identified asP. sheridani (Macleay, 1884), is redescribed as valid and a senior synonym of the latter species, following examination of the holotype of the former and comparative material.Polydactylus macrochir is characterized by 14 or 15 pectoral-fin rays (usually 14), five pectoral filaments, 70–76 pored lateral-line scales, 32–35 gill rakers, occipital profile concave in adults, posterior margin of maxilla extending considerably beyond posterior margin of adipose eyelid, depth of posterior portion of maxilla greater than dermal eye opening in adults, second spine of first dorsal fin very strong and long pectoral-fin rays (22–27% of standard length).Polydactylus macrochir is currently known only from northern Australian and southern Papua New Guinea, being endemic to those areas.

A review of the Indo-Pacific bonefishes of the Albula argentea complex, with a description of a new species

In this statement about numbers of nominal and valid species, the bonefish Albula argentea (Forster in Bloch and Schneider 1801) of the western and South Pacific, previously regarded as an unavailable name, is a senior synonym of Albula forsteri Valenciennes (an unnecessary replacement name for A. argentea) and A. neoguinaica Valenciennes. It is easily distinguished from the wide-ranging A. glossodonta (Forsskål 1775) by its more pointed lower jaw and higher vertebral and lateral-line scale counts. It is most similar to the Indian Ocean A. oligolepis, described here as a new species, and the endemic Hawaiian A. virgata Jordan and Jordan, resurrected from synonymy. Albula argentea differs from its two related species by higher counts of pored lateral-line scales and vertebrae. It has 68–74 (mode 70) lateral-line scales vs. 61–65 (63) for A. oligolepis and 63–67 (65) for A. virgata, and 71–74 (73) vertebrae vs. 64–66 (65) for A. oligolepis and 65–68 (67) for A.virgata. Albulavirgata differs further from A. oligolepis in having the pelvic fin tip reaching beyond the anus (vs. short of or just reaching anus) and higher numbers of scale rows above the lateral line 9–10 (9) vs. 7½–8 (8) for A. oligolepis.

Polymerase chain reaction–restriction fragment length polymorphism analysis for species identification of hairtail fish fillets from supermarkets in Japan

Hairtail fillets are marketed as both fresh and frozen forms in retail outlets within Japan. The present study was undertaken to develop a rapid and reliable method for identification of the hairtail species in commercial fillets. A total of 64 fillet samples, caught from various localities within Japan and purchased from various supermarkets, were analyzed. Polymerase chain reaction (PCR) amplification of a portion of the mitochondrial DNA encoding 16S ribosomal RNA gene and subsequent restriction digestion of the amplified products, using Vspl endonuclease, generated different restriction patterns indicating two different species of hairtails in the fillet samples. The results indicated that the commercial hairtail fillets, labeled and marketed as ‘Tachiuo’ in Japan, were comprised of two species of hairtails with Trichiurus japonicus (commonly called Tachiuo) accounting for 47% and Trichiurus sp. 2 (commonly called Tenjikutachi) accounting for 53% of the analyzed samples. This simple and inexpensive PCR-restriction fragment length polymorphism analysis can be routinely applied to determine species composition of hairtails in commercial fillets.

Review of the Acanthopagrus latus complex (Perciformes: Sparidae) with descriptions of three new species from the Indo‐West Pacific Ocean

Acanthopagrus latus, long considered a single valid Indo-West Pacific Ocean species, characterized by having yellow pelvic, anal and caudal fins, is reviewed and separated into A. latus (east Asian shelf) and Acanthopagrus longispinnis (Bengal Bay), and three new species: Acanthopagrus morrisoni sp. nov. (north-western Australia), Acanthopagrus arabicus sp. nov. [Middle East (except for the Red Sea) to coasts of Iran and Pakistan, and western Indian coast] and Acanthopagrus sheim sp. nov. (The Gulf). Although A. latus as redefined considerably varies in morphology and colouration, it can be recognized as a discrete east Asian endemic, with the following nominal species being junior synonyms: Chrysophrys auripes, Chrysophrys xanthopoda, Chrysophrys rubroptera and Sparus chrysopterus. Chrysophrys novaecaledoniae, known only from the holotype (type locality: Nouméa, New Caledonia), is a questionable junior synonym of A. latus, the lack of subsequent collections suggesting that the type locality is erroneous. Acanthopagrus longispinnis is differentiated from the other species in the complex by consistently having 12 dorsal-fin spines and a much larger second anal-fin spine, 21-26% (mean 23%) of standard length (LS ) (v. 14-24%, mean 18-21% in the other four species). Acanthopagrus morrisoni sp. nov. has the entire caudal fin yellow with a wide black posterior margin (persisting in preserved specimens) and consistently 3 ½ scale rows between the fifth dorsal-fin spine base and the lateral line. Acanthopagrus sheim sp. nov. has the pelvic, anal and lower caudal fins vivid yellow, with two (rarely three) small black blotches on the lower inter-radial membranes between the spinous and soft dorsal-fin rays. Acanthopagrus arabicus sp. nov. consistently has 4 ½ scale rows between the fifth dorsal-fin spine base and the lateral line, whereas A. latus always has black streaks proximally on the inter-radial membranes between the yellow anal-fin rays. A neotype and lectotye, respectively, are designated for A. latus and A. longispinnis. The p-distance (net nucleotide substitutions per site) of partial mitochondrial 16s ribosomal RNA genes (538 bp) among the above species (except A. longispinnis) and three other congeners (Acanthopagrus berda, Acanthopagrus pacificus and Acanthopagrus bifasciatus) strongly indicates that each is a distinct species. A key is provided for the 20 species of Acanthopagrus currently known from the Indo-West Pacific Ocean.

Taxonomic Review of the Western Indian Ocean Species of the Genus Acanthopagrus Peters, 1855 (Perciformes: Sparidae), with Description of a New Species from Oman

Abstract The taxonomy of the Western Indian Ocean species of Acanthopagrus is reviewed. A new species, A. omanensis, is illustrated and described from two specimens. Acanthopagrus vagus (Peters, 1852) is resurrected from the synonymy of Acanthopagrus berda (Forsskål, 1775), redescribed, and compared with A. berda. Acanthopagrus vagus differs from all congeners in the following combination: scale rows between fifth dorsal-fin spine base and lateral line 3; front edge of dorsal scaly area on head with a median W-shaped scaleless area anteriorly; second anal-fin spine longer than third anal-fin spine; ventral edge of first two infraorbitals straight (slightly curved in fish more than 25 cm SL); preopercle flange with 0–6 scales, number increasing with growth, scales obvious on fish more than 20 cm SL; anal fin with pale rays, and a black streak near the base on each inter-radial membrane; molariform teeth well developed on both jaws. Acanthopagrus berda is differentiated from all congeners by the following combination: scale rows between fifth dorsal-fin spine base and lateral line 3; anterior head profile slightly convex, front edge of dorsal scaly area of head convex, with small scales anteriorly; ventral edge of first two infraorbitals with a strongly curved concavity that receives the enlarged tip of the maxilla in fish larger than 13 cm SL; no scales on preopercle flange; second anal-fin spine clearly longer than third anal-fin spine; anal fin almost completely black (no pale rays); molariform teeth well developed, lower jaw teeth rows strongly curved laterally at rear of jaw. Acanthopagrus omanensis, new species, is discernible from all congeners by the following combination: scale rows between fifth dorsal-fin spine base and lateral line 5; front edge of dorsal scaly area on head forming an obtuse angle anteriorly; ventral edge of first two infraorbitals straight; no scales on preopercle flange; second anal-fin spine slender and subequal to third anal-fin spine; dorsal and caudal fins with wide black margins; upper and lower molariform teeth poorly developed. Junior synonyms of A. berda and A. vagus are discussed, with notes on other congeners, including nominal species of Sparidentex, which are sometimes confused with species of Acanthopagrus. A key to species of Acanthopagrus from the Western Indian Ocean is presented.

A new genus, Leptomelanosoma, for the polynemid fish previously known as Polydactylus indicus (Shaw, 1804) and a redescription of the species

Abstract A new genus, Leptomelanosoma, is proposed for the polynemid fish, Polydactylus indicus (Shaw, 1804). The genus differs from all other genera in the family Polynemidae by the following combination of characters: anterior one-third of lower jaw with small teeth extending onto lateral surface, adjacent portion of lip poorly developed; ethmoid not covered dorsally by frontals; sphenotics visible dorsally between anterior margins of parietal and pterotic; upper and lower caudal fin lobes very long, filamentous; swimbladder with many appendages inserted into lateral walls of abdominal cavity; grayish-black body. The type species, Polydactylus indicus, is redescribed as Leptomelanosoma indicum.