Muneo Okiyama

Aspects of the Roles of Squid in Food Chains of Marine Antarctic Ecosystems

Squid (Cephalopoda) are important organisms in marine food chains. However, there are very few studies of their ecological roles in marine ecosystems of the Antarctic. Seventy-six specimens of squid, both large (ca 355 mm in mantle length) and small (ca 40 mm), have been collected by large mid-water trawl operations of the Japanese pilot fishery for Antarctic Krill, Euphausia superba, in the Antarctic during 1980–81 and 1981–82. The squid collected are all considered to be young juveniles distributed at shallower depths than adults. Two species, Kondakovia longimana and Moroteuthis knipovitchi, are dominant. Alluroteuthis antarcticus, Pholidoteuthis boschmai, Brachioteu this picta and Galiteuthis glacialis also occurred in the collections. These squid consume various kinds of food, but they feed mainly on macro-zooplankton and micro-nekton. Krill is the main food item of squid in the Antarctic. An amphipod, Themisto gaudichaudii, is also a major component of the food of Kondakovia longimana. Small euphausiids, Thysanoessa macrura, and large chaetognaths, Sagitta gazellae, are also found in the stomachs of K. longimana, which indicates that the species is a plankton feeder. Fish are considered to be a major food item for Moroteuthis knipovitchi, together with E. superba. Cannibalism appears to be rather common in these squid. Predation by deep-diving Sperm Whales, Physeter catodon, on squid larger than 400 mm in mantle length was observed, and this, associated with the fact that such large squid were not caught in mid-water trawls, suggests that squid are segregated into different water depths according to size and maturity in the Antarctic.

Osteology and relationships ofPseudotrichonotus altivelis (Teleostei: Aulopiformes: Pseudotrichonotidae)

The osteology of the rate Japanese fishPseudotrichonotus altivelis is described based on several specimens collected off the Izu Peninsula. Relationships ofPseudotrichonotus are discussed based on osteological comparisons with other neoteleosts. The placement ofPseudotrichonotus among iniomous fishes has been questioned because of its lower numbers of caudal-fin, pelvic-fin, and branchiostegal rays. Our investigation supports an iniomous affinity forPseudotrichonotus, specifically as a member of the Aulopiformes. Within that group,Pseudotrichonotus belongs in a new suborder diagnosed herein, the Synodontoidei, which also includes the Aulopidae (Aulopus), Synodontidae (Synodus andTrachinocephalus), and Harpadontidae (Harpadon andSaurida). A synodontoid affinity forAulopus has never been suggested, but numerous osteological features support the monophyly of this clade. Synodontoids have a peculiar proximal segmentation of most principal caudal-fin rays, expanded neural and haemal spines on posterior vertebrae, cartilage extending along the ventral margin of the anterior ceratohyal, ventral displacement of the first one to three epineurals, supraneurals with large laminar expansions and six or more branchiostegals on the posterior ceratohyal. They lack median caudal cartilages. Among synodontoids,Pseudotrichonotus is the sister group of the Synodontidae plus Harpadontidae, with which it shares paired peritoneal pigment spots, an abrupt transition between the epipleurals in and beneath the horizontal septum, and absence of the fourth pharyngobranchial toothplate. Our study does not support a previously proposed relationship betweenBathysaurus and synodontids.

Mesopelagic Fishes of the Bering Sea and Adjacent Northern North Pacific Ocean

AbstractFourteen midwater trawl collections to depths of 450 m to 1,400 m were taken at eleven stations in the Bering Sea and adjoining regions of the northern North Pacific by the R/V Hakuho Maru during the summer of 1975. A total of 29 kinds of fishes were identified. Mesopelagic fishes of the families Myctophidae, Gonostomatidae and Bathylagidae predominated in the catches, contributing 14 species (94%) of the fishes caught.Seventeen species of fishes were caught in the Bering Sea, and all of these are known from nearby areas. The mesopelagic fish fauna of the Bering Sea is similar to that in adjoining regions of the northern North Pacific Ocean: endemic species are rare or absent. Stenobrachius nannochir was usually the most common mesopelagic fish in our catches.Stenobrachius leucopsarus is a diel vertical migrant that is usually the dominant mesopelagic fish in modified Subarctic waters of the northeastern Pacific. The change in dominance fromS. nannochir in the western Bering Sea toS. leucopsarus in the eastern Bering Sea is related to differences in oceanographic conditions.

Reproductive behaviour of the filefishRudarius ercodes: male spawning parades and female choice

SynopsisThe reproductive behaviour ofRudarius ercodes is described from undersea observations in Aburatsubo Bay, Japan. Reproductive behaviour can be separated into four parts: (1) Prespawning Search = searching for spawning sites by females and searching for gravid females by males, (2) Spawning Parade = males follow a gravid female in a line, competing with each other to reach the head of the queue, (3) Spawning = the female takes the spawning position, males rush to the side of the female, and mating occurs between one female and several anterior males of the spawning parade, (4) Parental Care = females attach adhesive eggs to seaweed with the mouth and guard them until embryos hatch. There is no male parental care. The reproductive season ranges from May to October and spawning occurs early in the morning every day. Females begin feeding early in the morning, but males feed little at this time.R. ercodes shows neither territorial behaviour nor fixed-pair spawning. One male might spawn several times in one morning. One female spawns at most once every 5 days. The mating system of this species is promiscuous. The probable function of the spawning parade as a style allowing female choice is discussed.

Reproductive Behaviour of Japanese Tubesnout, Aulichthys japonicus (Gasterosteiformes), in the Natural Habitat Compared with Relatives

We observed significant sexual dimorphism in size (females > males) and in colour in Japanese tubesnout, Aulichthys japonicus, in Aburatsubo Bay, central Japan, and Otsuchi Bay, northern Japan. This species is known to spawn its eggs into ascidians. We observed reproductive behaviour of tubesnout in the natural environment in both bays. All the males established territories at harbours or rocky shores and showed conspicuous nuptial colouration with metallic green or blue on their snout and bright yellow on the body. Females had a dark brown body with remarkable white spots. The male territories varied somewhat in location and extent on a daily basis. The individual male size and territory size were not correlated. The females usually stayed in the seaweed beds where no males were present. Males and females were distributed separately, and the gravid females visited the male territories in groups to spawn. The territorial males courted the gravid females by rushing and returning, and tried to lead the females to the particular place of their territories by tail beating. We discuss nuptial colouration, courtship behaviour and territoriality in comparison to the related species; Aulorhynchus flavidus, Hypoptychus dybowskii, and gasterosteid fishes.

A new type of exterilium larva referable to Leptobrotula (Ophidiiformes : Ophidiidae : Neobythitinae) from tropical Indo-West Pacific

A new type of exterilium larvae referable to Leptobrotula (Ophidiiformes: Ophidiidae) is described on the basis of two specimens (20.7+ mm and ca. 35.4 mm SL) collected from the tropical Indo-Pacific. They are characterized, in particular, by several elongated anterior dorsal fin rays supported by the large dorsal pterygiophores and the exterilium gut bearing filamentous appendages along the ventral border. It is suggested from larval evidence that Leptobrotula forms a distinct lineage with Brotulotaenia and Lamprogrammus, which may be placed in an expanded Brotulonaeniinae.

A pelagic juvenile ofBarathronus pacificus (Ophidiiformes: Aphyonidae) from the Southwest Pacific, with notes on its metamorphosis

T he deep-water ophidioid family Aphyonidae comprises six genera with more than 25 species, all of which apparently live at bathyal and abyssal levels (Marshall, 1984; Nelson, 1994). Since Nielsens (1969) extensive review of the systematics and biology of the family, several new taxa have been described (Nielsen, 1974, 1984a, b; Shcherbachev, 1976; Nielsen and Eagle, 1984). However, little is known about the early life history of these progenetic (neotenic) viviparous fishes except for the advanced embryonic stages of several species (Nielsen, 1969, t984b; Marshall, 1984). During a recent cruise to the southern Pacific Ocean by the R/V Hakuho-maru of the Ocean Research Institute, a single pelagic juvenile referable to the aphyonid Barathronus pacificus was collected in a plankton tow. This rare specimen is herein described and the possible process of its metamorphosis discussed with reference to progenetic tendencies.

Remarkable ophidiid larva (Neobythitinae) from New Guinean waters

A new type of ophidiid larva referred to the Neobythitinae is described on the basis of one specimen (22.5 mm in standard length: SL) found in the “Dana” flatfish larval collection from New Guinean waters. It is characterized by a very high body (ca. 48% SL), with a single elongate first dorsal-fin ray and protruding abdominal cavity with a long fleshy appendage at its posteroventral end. Generic and specific affinities of the larva are discussed. It is supposed that the larva belongs to one of the Pycnocraspedum species, probably to P. squamipinne.

Record of Ipnops sp. (Ipnopidae: Aulopiformes) from northern Japan

During a dive of the submersible Shinkai 6500 (run by the Japan Agency for Marine-Earth Science and Technology, JAMSTEC, formerly the Japan Marine Science and Technology Center) in the Japan Trench, off Cape Erimo, northern Japan, the second author succeeded in taking a photograph of an ipnopid fish on the bottom at about 3,500 m (Fig. 1). Locality data are as follows: Okamura (Cadet) Seamount (41 15.960N, 144 34.560E), water temperature 1.8 C, at the apex of the seamount, KY07-14, mother ship Yokosuka, 1 October 2007. This specimen was readily referred to the genus Ipnops based on its general morphology and the distinctive reflection of light from its unique plate-like eyes, as finely demonstrated in the robotic-camera photograph of Roper and Brundage (1972). This record represents an unexpected northern extension of the geographical ranges of the genus, including its first appearance in Japanese waters. Currently two species of Ipnops are known from lower bathyal and abyssal depths in the Indo-Pacific Ocean, i.e., Ipnops agassizi and Ipnops meadi. The two species can usually be separated by their depth of capture, with I. agassizi found at shallower depths than I. meadi at the same latitude (Fig. 2). Ipnops agassizi is concentrated in the lower bathyal zone (\3,000 m) north of around 20 S, whereas I. meadi occupies a deeper habitat and extends its depth range to the abyssal zone (down to 5,400 m; Shcherbachev 1981) further south, in the absence of I. meadi. In contrast, I. meadi is restricted to the abyssal zone (3,310–4,940 m) throughout its range. From these data, the present specimen is most probably referable to I. meadi, and represents an extension of its northern range limit from ca. 29 N to ca. 41 N. The size of this specimen is estimated to be about 150 mm in TL from the photograph taken from the submersible, which was more than 5 m from the target fish. Since recorded demersal specimens of I. meadi are 50–121 mm SL (Nielsen 1966), this fish may be a fully grown adult. Judging from the photograph, this true benthic fish inhabits a slightly disturbed muddy flat bottom (also confirmed on the core sample near the present photo site) dominated by certain ophiuroids. Although little is known about the biology of I. meadi, the putative early life history of I. agassizi, including extensive ontogenetic vertical migration terminating at around 55 mm SL (Okiyama 1986, 1988), may be shared by I. meadi. In the present case, therefore, there is the possibility of northward transport during a long larval stage by the prevailing Kuroshio Current from its typical adult habitat in the subtropical/tropical western Pacific. Without the specimen to hand, it is also possible that an undescribed species is represented in the photograph. M. Okiyama (&) Marine Ecology Research Institute, Towa Edogawabashi Bldg 7F, 347 Yamabuki, Shinjyuku-ku, Tokyo 162-0801, Japan e-mail: okiyama@kaiseiken.or.jp

A megapterygium larva of Discoverichthys praecox (Aulopiformes: Ipnopidae) from the tropical western Pacific

The larva of Discoverichthys (Aulopiformes: Ipnopidae) is described for the first time based on a specimen 39.5 mm in standard length collected in surface waters near the Marianas in the western North Pacific. Despite its remote location from the previous record in eastern North Atlantic (type locality), this larva was identified as Discoverichthys praecox by general agreements of meristic counts and other morphological features. It is characterized by the following possible autapomorphic features: body moderately elongate, with uniformly distended abdomen, terminating in long, stout trailing gut; all fins, particularly the pectoral and pelvic, are extensively produced; body pigmentation is scanty, but all fins except the caudal are polka-dotted distally and covered by unusually thick skin; the skeleton is largely cartilaginous, with poorly differentiated axial components and uniquely expanded dorsal- and anal-fin pterygiophores. Its peculiar morphology is discussed with special reference to transformation events.