The ophidiid fish genus Homostolus is revised on the basis of 44 specimens. Meristic and morphometric characters strongly indicate that the genus as presently known contains a single species, Homostolus acer Smith et Radcliffe, 1913, with Homostolus japonicus Matsubara, 1943, reduced to synonymy. Geographical variations found in certain meristic characters indicate that H.acer expanded its range from Philippine waters into both northern and southern waters. The species is distributed on deep-sea floors from the Pacific Ocean off central Japan, to the Indian Ocean off northern Western Australia, and to the Tasman Sea off New South Wales, at bathyal depths from about 400 to 700m.

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Platygobiopsis akihito is described from 12 specimens 63.4-95.9mm SL. It is most closely related to Gobiopsis Steindachner, based on the presence of a pair of chin barbels and two horizontal, fleshy, papillae-bearing folds on the cheek, and the absence of vertical papillae-bearing folds on the sides of the anterior half of the head. Platygobiopsis differs most obviously from all the species Lachner and McKinney (1978, 1979) included in Gobiopsis in having an exceedingly depressed head and body (both the most depressed of any gobioid), an elongate form (depth 4.5-5.8% SL), and in its dorsal-and anal-fin formulae: D. VI-12, A. I, 12, which include at least one more segmented dorsal-fin ray and two more segmented anal-fin rays than is known to occur in any species of Gobiopsis.

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Idiastion pacificum is described as a new, and second, species of the genus Idiastion. This species is the first of the genus from the Indo-Pacific region. It is characterized by having 25 rather than 24 vertebrae, branched pectoral rays, humpbacked body outline, no occipital pit, a small slit behind the fourth gill arch, a swimbladder, teeth on the palatines and well developed spines on head. It is distinguished from I. kyphos Eschmeyer recorded from Atlantic by having ctenoid scales on nape and maxilla, and cycloid scales on isthmus, breast, anterior part of belly and membranes of anal, lower part of pectoral and pelvic fins.

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A new cottid species, Porocottus coronatus, is described on the basis of nine specimens from the Pacific coast of eastern Hokkaido, Japan. It differs from other species of this genus by having a group of finger-like cirri on the dorsal midline of the head, long uppermost preopercular spine, 15-16 anal fin rays and well developed cephalic sensory system with many small pores.

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The collection of an adult specimen of Echiodon from Owase, Japan, enabled us to further evaluate one of the unresolved identification problems listed by Markle and Olney (1990). The recognition of Echiodon anchipterus Williams as a valid western Pacific species was questioned by Markle and Olney (1990), who tentatively synonymized it with the western Indian Ocean E. coheni Williams. The Japanese specimen had 15-16 pectoral fin-rays (vs. 18 in Echiodon coheni), 22 total nasal lamellae (vs. 24), and 21 precaudal vertebrae giving a range for E. anchipterus of 19-21 (vs. 18-19). These new data support the recognition-of both E. anchipterus and _{E. coheni} as valid, allopatrically distributed species. The phylogenetic relationships among the species of Echiodon are reexamined and a cladogram summa-rizing our hypothesis of their interrelationships is presented.
Eurypleuron owasianum (Matsubara) is considered to be endemic to the Japan zoogeographic region, where adults are known only from specimens taken off Owase, Japan. The South African, southeastern Australian, New Zealand, and Sala y Gomez Ridge specimens are collectively referred to Eurypleuron cinereum (Smith) pending a comprehensive revision of the group.

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Naso minor was described from a single specimen (Smith, 1966). Only one other specimen has since been reported (Randall, 1986). The species apparently differed from N. thynnoides in the ratio of fork length to head length and eye diameter, the shape of the caudal peduncle spine, and in number of dorsal spines. Collections of 24 specimens of four- and five-spined individuals (putatively assigned to both species) from the Philippines revealed that the first three differences are not valid. However, spine number, the length of the nasal groove, the pigmentation of the basal plate of the caudal peduncle spine, and the morphology of the first dorsal-fin pterygiophore confirm the distinctness of the two species.

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The ultra-structure of the epidermis of the mudskipper, Periophthalmus modestus, was ex-amined by both light and transmission electron microscopies. The epidermis is exceptionally not well endowed with mucous or granular cells. Filament-containing cells occur in three distinct layers of the surface, middle and basal epidermis. The surface layer is further subdivided into two layers, an outermost and less superficial one. Two different cell types were identified in the epidermis. Type I cells are flat cells in a single stratum. Type II cells are enormous cells, characterized by having a large vacuole in the cytoplasm. The outermost layer is composed of a free surface of Type I cells and numerous microridges covered with a fuzzy, fibrillar substance. The “fuzz” forms a cuticule-like structure, but keratinization as found in terrestrial animals does not occur. The superficial layer contains Type I cells and intraepithelial blood capillaries. When Type I cells become senescent, numerous intercellular spaces are formed in the plasma membranes of adjacent cells, with the senescent cells finally falling off. Just beneath these cells, however, young cells of Type I are always found. The blood capillaries are usually reinforced with young Type I cells. A large volume of oxygen may be absorbed through the skin using the blood capillary network. The middle layer contains several strata of Type II cells. The special corky structure of these cells seems to play an important role in thermal insulation and protection against ultraviolet light in relation to life out of water. However, by comparison with terrestrial animals, the histological design of the epidermis of this goby appears incomplete, so as to reduce desiccation on land, owing to the epidermis lacking a keratinized stratum. The differentiation of the epidermis seems to be an adaptation for a terrestrial habit in this species.

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The present paper deals with gonadal formation, sex succession and sexual function in the Japanese hawkfishes, Cirrhitichthys aureus (Temminck et Schlegel), C. aprinus (Cuvier), C. falco Randall, Cirrhitops hubbardi (Schultz) and Cyprinocirrhites polyactis (Bleeker). Detailed studies were made for C. aureus collected from Suruga Bay, central Japan. In this species the gonad of a young fish of 21.8mm SL had begun to initially differentiate into an ovary forming an early ovarian cavity of the parovarian type. The gonadal structures of 63 further specimens of C. aureus, ranging from 23.9 to 114.3mm SL, could be separated into three categories: viz., ovaries (7), ambisexual gonads (54) and secondary testes (2). Reproduction of C. aureus in Suruga Bay took place from June to November. Although ovaries which appeared throughout the year presented only in the immature stage and occurred only in small fish ranging from 25.1 to 46.6mm SL, functional gonads occurred in 32 ambisexual fish ranging from 61.5 to 113.5mm SL and in one secondary male of 101.5mm SL, collected during the reproductive season. The smaller ambisexual fish, ranging from 61.5 to 92.0mm SL, showed active oogenetic processes in the major ovarian zones with many ripened eggs ovulating into the ovarian cavity. These gynogenic gonads undoubtedly functioned as female; however, distinct meiosis proceeded partially in the minor testicular zones with a few spermatozoa occurring in the was deferens. The larger ambisexual specimens, ranging from 71.5 to 113.5mm SL, had slender androgenic gonads, which showed active spermatogenesis in various testicular zones and which might function as males with reduced ovigerous lamellae. The secondary males had testes occupied by seminal lobules, but which retained the ovarian cavity within. According to aquarium rearing experiments, in a pair of C. aureus twice crossed mutually after spawning, functional sex changes occurred in twice, opposite directions, in a single gonad, i.e., from female to male and from male to female. These gonadal aspects in captive C. aureus seemed to show an intermediate phenomenon between consecutive and simultaneous hermaphroditism. This finding also suggested that C. aureus had similar sex succession characteristics to those of the serranid, Serranus fasciatus, studied by Hasting and Petersen (1986) and the gobiid, Trimma okinawae, studied by Sunobe (1990). We also established that normal functional hermaphroditism occurred in the four other cirrhitid species, which showed almost identical gonadal characteristics to C. aureus.

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Morphological changes in free neuromasts are reported from larvae of the Ayu, Plecoglossus altivelis. In newly-hatched larvae, free neuromasts were already recognizable in both the head and trunk. During larval growth, the number of free neuromasts increased, and the number of its sensory cells 2 days after hatching was constant. In the trunk, two types of free neuromasts, one with maximum sensitivity in the antero-posterior direction and the other with maximum sensitivity in the dorso-ventral direction, were observed. The former type predominated. In the head, free neuromasts were located around the eye and nose, their directions of maximum sensitivity forming lines tangential to concentric circles about the eye and nose. Distinct changes in free neuromasts occurred during the formation of the canal organ. The canal organ was first observed in the head region 64 days after hatching and in the trunk region 100 days after hatching. Concomitant with the formation of the canal organ, the profile of the cupulae of the free neuromasts changed from a flat bar to semispherical. Sensory cells in the canal neuromasts did not differ morphologically from those in the free neuromasts. It is considered that there is a close relationship between the sensitivity of the neuromast and the shape of the cupula, i.e., that the free neuromasts are adapted to slow water flow, as in lakes and the sea, while the neuromasts in the canal organ are adapted to rapid water flow.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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