Larval and juvenile Polymetme elongata (Stomiiformes: Phosichthyidae) collected from Suruga Bay and offshore waters, Japan

Two larvae [17.4 mm standard length: SL (postflexion stage)] and 26.1 mm SL (transformation stage)] and a juvenile (31.7 mm SL) of a phosichthyid, Polymetme elongata, from Suruga Bay and offshore waters, central Japan, are described. These specimens had an elongate body with relatively short preanal length (53–63% SL), long anal fin base (2.6–3.4 times dorsal fin base length), and anal fin origin below dorsal fin base, and were further characterized by a blackish flap on each eye and internal clusters of melanophores (e.g., along caudal myosepta around midlateral line and on ventral margin of caudal peduncle). The short preanal length and larval melanophore pattern were very similar to those of another phosichthyid, Yarrella blackfordi, from the Atlantic Ocean.     

Osteological development of the lophiid anglerfish,lophius gastrophysus

The osteological development of the head skeleton and dorsal, pectoral, and anal fin supports, are described from cleared and stained specimens ofLophius gastrophysus larvae, ranging from 4.6 to 21.8 mm NL; the results are compared with those of juvenile (79.8 mm SL) and adult (398 mm SL) specimens. Tiny conical teeth are present on the premaxillary, dentary, palatine and vomer since early stage. The first three dorsal fin spines are initially positioned on the midline of body posterior to the supraoccipital, but they migrate forward with growth and become cephalic in juveniles. The forward movement of the dorsal spines is produced by the forward extension of the cartilaginous basal inside the subepidermal space. During the planktonic larval stage the pectoral fins are on the sides of body as in ordinary fishes, but they move ventrad and become leg-like in bottom living juveniles and adults. Ossification of the caudal complex ofL. gastrophysus larvae proceeds very slowly and only the 21.8 mm NL larva has an almost completely ossified caudal complex. Eight principal caudal rays are loosely attached on the posterior edge of the hypurals and no procurrent rays are present. Larvae have well developed parhypurapophysis at the mid-portion of the urostyle which transforms into keel-like structure in juveniles and adults.     

External Morphology of Lophiosilurus alexandri Steindachner, 1876 during Early Stages of Development,and Its Implications for the Evolution of Pseudopimelodidae (Siluriformes)

Pseudopimelodidae are Neotropical catfishes characterized by having slightly to strongly depressed body in fully developed specimens. The largest species of the family with 500 mm SL, Lophiosilurus alexandri, experiences impressive changes in body shape during development, becoming extremely depressed when fully developed. Accordingly, Lophiosilurus alexandri is an ideal species to observe the morphological changes during ontogeny, and to seek solid interpretations on the polarity of characters. Specimens of distinct larval periods (yolk sac, flexion and postflexion; n = 186 specimens) and juvenile stages (n = 20) were analyzed. Changes in body shape, position of mouth and eye, morphology of fins and pigmentation were observed during the development of Lophiosilurus. Larvae (5.7–11.2 mm standard length) had pigmentation concentrated on the head and parts of body, eyes small and pigmented, short barbels, and well-developed finfold. Juveniles (15.9–28.1 mm standard length) had body shape similar to adult, with head depressed and bearing bony ridges, large mouth, dorsally-oriented eyes, small barbels and well-developed shoulder bulges (cleithral width). The greatest morphological changes in the development of L. alexandri occurred during the postflexion larval stage. Relative to standard length, measurements of snout length, head depth and body depth are smaller in juveniles than in larvae, but body width is larger. New interpretations on the phylogenetic characters related to these changes are provided in view of the two alternative hypotheses of the evolution of Pseudopimelodidae.     

Morphological aspects of the development of swimming and feeding functions in the milkfishChanos chanos

Development of swimming and feeding abilities based on morphological development of larval and early juvenileChanos chanos was investigated. In larvae smaller than about 6.5 mm SL, mechanical supports of fins and branchial arches were in a primordial stage of development. Supports and rays of the vertical fins and branchial arches rapidly developed from 6.5 mm SL, and all components appeared by about 10.5 mm SL. Thereafter body depth proportion changed and the supports and rays of the paired fins and gill-rakers developed. These developmental events were nearly or totally completed by about 17 mm SL, and we concluded that the larvae transformed to juveniles at this size. By this time, the mode of swimming of the fish shifted from undulating locomotion to caudal propulsion and that of feeding from swallowing paniculate food to filtering and concentrating substrate food matters using gill-rakers and the epibranchial organ. One of the most characteristic, and well-known, phenomena in the life history ofChanos chanos is the mass occurrence in the surf zone of postlarvae of a limited size range. In view of the scheme of the development of mechanical supports of the body and fins, they may acquire a swimming ability strong enough to move against the current only upon reaching about 10.5 mm SL, and if active shoreward migration of the larvae occurs, it is only during the late period of their journey from the spawning grounds to the shore. The sudden disappearance from the surf zone of larvae larger than 15–16 mm SL is obviously related to a change in food habit.     

Occurrence of Larval and Juvenile Japanese Snook, <Emphasis Type="Italic">Lates japonicus</Emphasis>, in the Shimanto Estuary,Japan

A total of 54 postlarval, 12 juvenile and six young Lates japonicus were collected in the Shimanto estuary from August 1985 to January 1987. The larvae (4.3–7.6 mm SL) and juveniles (8.1–28.0 mm SL) occurred only in areas with eelgrass beds from late July to middle August. Temperatures and salinities at waters where any number of them were collected ranged from 27.8 to 31.9°C and from 2.8 to 18.2%, respectively. The larvae are very similar in general morphology to those of Mugilidae and some of Gobiidae, but are distinguished from others by the spines of preopercle, position of the anus and pigmentation patterns in the posterior part of body.     

Development of Sebastes taczanowskii (Scorpaenidae) in the Sea of Japan off Hokkaido with a key to species of larvae

The larval and juvenile stages of Sebastes taczanowskii (Japanese name: Ezo-mebaru) are described and illustrated based on 33 wild specimens [7.1–26.9 mm in body length (BL)] collected in the Sea of Japan, and eight specimens of reared larvae extruded from the one specimen of a captive pregnant female. Larvae were extruded between 4.3–5.0 mm BL and notochord flexion occurred 5.7–9.0 mm BL. Transformation from postflexion larvae to pelagic juveniles occurred between 13 and 17 mm BL. Preflexion and flexion larvae have a single melanophore row on the dorsal surface on the tail, and an internal line of melanistic dashes on the ventral side of the tail. Lateral pigmentation of postflexion and transforming larval body surfaces are light. Compared with other Japanese rockfish species, S. taczanowskii is shallow-bodied throughout both larval and juvenile stages. We provide an identification key to preflexion and flexion stage rockfish larvae found around the Japanese archipelago, and comparisons with other species. Larval and juvenile S. taczanowskii occurred in both near-shore and relatively offshore water around Shakotan Peninsula-Ishikari Bay, Hokkaido in June and July.     

Larval morphology and occurrence of the louvar,Luvarus imperialis (Luvaridae)

A total of nineteenLuvarus imperialis larvae, 3.5 to 10.7 mm in standard length were collected during the cruises of R/V Shoyo Maru in the northwestern Pacific and eastern Indian Ocean. This paper describes meristic and morphological features of these specimens throughout development. The features particularly noted in postlarvae and early juveniles ofL. imperialis are: 1) large head with a wide snout, 2) oval and well-compressed body, 3) large pectoral fins, 4) developed and finely serrated dorsal and pelvic spines, 5) well-developed head spination, 6) minute spines on the soft rays of all fins in larvae larger than about 5.6 mm SL, and 7) very rough body surface associated with the development of spiny-edged scales. Larvae ofL. imperialis occur mostly in the coastal waters between lat. 40°N and 40°S of the world oceans, suggested the spawning in temperate waters.     

Induction of ovarian maturation and development of eggs,larvae and juveniles of the tonguefish,Cynoglossus abbreviates,reared in the laboratory

Cynoglossus abbreviatus spawns from mid-March to mid-April in the Sea of Shimabara in Kyushu. During the spawning season ovarian maturation was successfully induced by injection of the pituitary homogenate ofHypophthalmichthys molitrix. The dose of the aceton-dried pituitary homogenate was 6.5 mg/kg body weight ofC. abbreviatus. It took about 2 days for ovulation after injection at a water temperature of 14 to 16°C. Artificial fertilizations were accomplished on March 29, 1974 and again on April 7, 1984, using the females matured by hormone injection in the latter case only. The larvae were reared on the rotifers,Artemia nauplii,Tigriopus japonicus and copepods collected from the sea over a period of 113 days in 1974 and 58 days in 1984. The eggs were pelagic, spherical, 1.19–1.23 mm in diameter and had 30–50 oilglobules of 0.068–0.095 mm in diameter, and the perivitelline space was narrow. The incubation period was 90–98 hours at a water temperature of 14 to 16°C. The newly hatched larvae were 3.18–3.45 mm TL and had 61–64 myomeres. The larvae had many melanophores and xanthophores on the body, forming three bands on the caudal region, but were lacking chromatophores on the finfolds. The yolk was completely absorbed when the larvae attained a size of 4.7–5.6 mm TL 8 days after hatching. A single elongated dosai fin ray developed on the head in the 8-day old larvae. The ray was reduced in size as long as the other rays 1 or 2 days after metamorphosis. The rudiment of pectoral fins were found on the both sides of the body in the 2-day old larvae, but two of them disappeared after metamorphosis. A pelvic fin first appeared as a ventral bud just anterior to the gut in the larva of 8.39 mm TL. The full count of 4 rays was observed on the larva of 10.83 mm TL. Metamorphosis began 22 days after hatching when the larvae were 11.20 mm TL. The right eye began to shift the left side of the head at night and reached to the final place after 8.5 hours. It took about 36 hours to complete the metamorphosis, including the eye movement and fusion of the hole in the rostral beak. At the last stage of metamorphosis, the dosal, caudal, anal and ventral fins became confluent. The larvae reached the juvenile stage at a size of 13.5–14.0 mm TL, approximately 28 days after hatchling. The growth of larvae reared in 1974 is expressed by the following equations: Y₁ = 3.448 · 1.0507^x (8≦X≦28) Y₂ = 6.3322 · 1.0275^x (28≦X≦75) where Y is the total length (mm) and X is the number of days after hatching. Growth rate changed after metamorphosis.     

Early development of the laboratory-reared flounder,Pleuronichthys cornutus

Fertilized eggs ofPleuronichthys cornutus were obtained by both artificial fertilization and natural spawning of laboratory-reared fish. The present paper describes in detail the early development of the fish and the rearing methods employed to provide basic information for mass production of this species. Eggs and sperm for artificial fertilization were obtained from adult fish caught in the Ariake Sound, Kyushu in November and December of 1984. Their maturation was successfully induced by intermuscular injection of pituitary homogenate of the silver carp,Hypophthalmichthys molitrix. Fertilized eggs were also obtained in 1985 by natural spawning of a broodstock kept in a tank for a year. Hatched larvae were fed successively with rotifers,Artemia nauplii and the harpacticoid copepod,Tigriopus japonicus and reared for 80 days. Ten thousand young fish of about 33 mm TL were obtained in 1984 and 1985 with the survival rate of about 17%. Ten developmental stages were defined on the basis of the morphological characteristics: A) newly hatched to 4 day old larvae, 2.7 to 4.1 mm TL (2.6 to 3.9 mmNL), yolk sac present; B) 4 to 16 day old larvae, 3.8 to 5.9 mm (3.6 to 5.6 mm), yolk resorbed, actively feeding on rotifers; C) 15 to 30 day old larvae, 6.3 to 8.3 mm (6.0 to 7.9 mm), notochord straight, hypural fin ray visible; D) 24 to 40 day old larvae, 6.7 to 9.2 mm (6.4 to 8.8 mm), caudal notochord upturned (45°); E) 28 to 45 day old larvae, 7.9 to 10.8 mm (7.5 to 10.3 mm), caudal notochord upturned (45°–90°); F) 32 to 50 day old larvae, 10.8 to 15.7 mm (8.8 to 12.8 mm BL), eyes symmetrical; G) 35 to 66 day old larvae, 13.4 to 20.0 mm (10.9 to 16.3 mm), eyes asymmetrical, but left eye not visible from the right side; H) 40 to 75 day old larvae, 13.8 to 26.2 mm (11.3 to 21.4 mm), the upper edge of left eye visible over top of the head from the right side; I) 46 to 89 day old larvae, 20.1 to 27.4 mm (16.4 to 22.4mm), left eye on the edge of the head and pupil visible from the right side; and J) juveniles of 51 day old or over, 23.6 mm or more (19.3 mm or more), metamorphosis completed. One to three inflections were found for relative growth of total length, eye diameter, upper jaw length, preanal length, and distance between the base of the pectoral fin and the anus against the notochord length or body length. Two inflections were found for body length (or notochord length)-body weight relationship. Most inflections appeared at the stages of D, F and J, corresponding to the body length of 8, 9–12 and 18–22 mm respectively.     

Small-scale patterns in distribution and feeding of Atlantic mackerel (Scomber scombrus L.) larvae in the Celtic Sea with special regard to intra-cohort cannibalism

Short-term variability in vertical distribution and feeding of Atlantic mackerel (Scomber scombrus L.) larvae was investigated while tracking a larval patch over a 48-h period. The patch was repeatedly sampled and a total of 12,462 mackerel larvae were caught within the upper 100 m of the water column. Physical parameters were monitored at the same time. Larval length distribution showed a mode in the 3.0 mm standard length (SL) class (mean abundance of 3.0 mm larvae =75.34 per 100 m³, s=34.37). Highest densities occurred at 20–40 m depth. Larvae <5.0 mm SL were highly aggregated above the thermocline, while larvae ≥5.0 mm SL were more dispersed and tended to migrate below the thermocline. Gut contents of 1,177 mackerel larvae (2.9–9.7 mm SL) were analyzed. Feeding incidence, mean number (numerical intensity) and mean dry weight (weight-based intensity) of prey items per larval gut were significantly dependent on larval size. However, while weight-based feeding intensities continued to increase with larval length, numerical intensity peaked at 4–4.9 mm SL, indicating a shift in the larval diet. While first-feeding larvae relied most heavily on copepod nauplii and eggs, larvae ≥5.0 mm SL initiated piscivorous feeding. All identifiable fish larvae were Atlantic mackerel. Thus, the piscivory was cannibalism. Larval feeding incidence and numerical feeding intensities peaked during daytime and were reduced at night. Daily ration estimates for first-feeding mackerel larvae <4.0 mm SL were extremely low = 1.43% body dry weight, but increased dramatically at 5.0 mm SL, i.e., at the onset of cannibalism, reaching >50% body dry weight in larva ≥8.0 mm SL. Received in revised form: 31 October 2000 Electronic Publication     

A new deepwater assfish, <Emphasis Type="Italic">Bassozetus nielseni</Emphasis> sp. nov. (Ophidiiformes: Ophidiidae), from the North Atlantic and West Indian oceans

A new deepwater assfish, Bassozetus nielseni sp. nov., is described from 29 specimens [147–615 mm in standard length (SL)] collected from the North Atlantic and West Indian oceans. It is distinguished from 13 congeners by the following combination of characters: dorsal-fin rays 122–129, long rakers on first gill arch 11–14, oblique scales 20–25, abdominal vertebrae 13–14, head length 18.1–21.3 % SL, body depth at anal-fin origin 8.2–14.6 % SL, predorsal length 16.4–20.1 % SL, tail length 62.7–68.0 % SL, posterior tip of pelvic-fin rays anterior to anus, a single median basibranchial tooth patch, dorsal margin of sagittal otolith smooth, and fins pale yellowish brown (preserved condition).     

The early life history of kurosoi,Sebastes schlegeli (Scorpaenidae), in the Sea of Japan

Larval and juvenile stages of kurosoi,Sebastes schlegeli, are described and illustrated from wild specimens. Some ecological aspects of larvae and juveniles are also described. Notochord flexion occurred between 5.6–7.5 mm SL. Transformation occurred between 13–20 mm SL. Preflexion and flexion larvae ofS. schlegeli can be distinguished from similar larvae by the pigmentation of the dorsal and ventral midlines of the tail and absence of pigmentation on the ventral portion of the rectum. After notochord flexion, the dorsal and lateral regions in both larvae and pelagic juveniles were heavily pigmented, suggesting adaptation for neustonic life style. Larvae and juveniles were caught at many coastal stations, but did not occur in cooler offshore waters. Larvae smaller than 20 mm SL inhabited surface waters. Until ca. 40 mm SL, juveniles inhabited mainly surface waters (without drifting seaweed), but also used other habitats, such as the drifting seaweed, and near the sea bed. Small larvae (<7 mm SL) fed mainly on copepod nauplii. Larger larvae fed on calanoid copepodites andEvadne nordmanni. Pelagic juveniles fed mainly on fish eggs, with fish larvae also being important food items for some individuals. Most food items taken by juveniles that were associated with drifting seaweed were eggs with attaching filaments (Cololabis saira andHyporhamphus sajori), suggesting that the high density of such food items both attracts and keeps juveniles around drifting seaweed.     

Review of the clingfish genus <Emphasis Type="Italic">Kopua</Emphasis> (Gobiesocidae: Trachelochisminae) in Japan,with description of a new species

A taxonomic review of the clingfish genus Kopua (Gobiesocidae: Trachelochisminae) in Japan recognizes three species: K. japonica Moore, Hutchins and Okamoto 2012, K. vermiculata Shinohara and Katayama 2015 and K. yoko sp. nov. Kopua japonica and K. vermiculata are redescribed with revised diagnoses on the basis of 20 specimens (10.4–30.4 mm standard length; SL) and the holotype, respectively. Kopua japonica is similar to K. vermiculata in head sensory pore characters (normally single nasal and postocular canal pores). However, the former differs distinctly from the latter as follows: 6–8 (modally 7) gill rakers (vs. 4 or 6); 31–33 (33) vertebrae (vs. 35); anus slightly closer to posterior margin of disc than to anal-fin origin (vs. much closer to posterior margin of disc); snout length 5.3–8.7 (mean 7.0) % SL (vs. 9.2 % SL); disc length 21.2–24.0 (22.8) % SL (vs. 18.8 % SL); pre-dorsal- and anal-fin lengths 72.9–78.4 (75.2) and 78.1–82.8 (80.1) % SL, respectively (vs. 67.5 and 73.6 % SL); and two stripes on cheek (vs. a triangular blotch). Kopua yoko sp. nov., based on 14 specimens (17.7–28.8 mm SL) from the Pacific coast of southern Japan, Sea of Japan and the East China Sea, is characterized by the following combination of characters: 6 or 7 (modally 6) dorsal-fin rays; 4–6 (5) anal-fin rays; 21 or 22 (21) pectoral-fin rays; 4–6 (5 or 6) gill rakers; 31–33 (31) vertebrae; a single (rarely two) nasal canal pores; two lacrimal and preopercular canal pores; snout length 6.5–7.9 (mean 7.1) % SL; gill opening depth 5.8–7.1 (6.5) % SL; least interorbital width 2.0–3.7 (2.6) % SL; disc length 20.3–25.0 (23.1) % SL, disc region D without flattened papillae; caudal-peduncle depth 8.1–10.2 (9.2) % SL; anus slightly closer to posterior margin of disc than to anal-fin origin; pre-dorsal- and anal-fin lengths 71.6–77.1 (73.9) and 77.0–83.7 (80.4) % SL, respectively; post-dorsal-caudal length 12.6–15.0 (13.8) % SL; arch-shaped blotches on lateral aspect of body; and two reddish-orange stripes on cheek. Morphological changes with growth in K. japonica and K. yoko sp. nov. are also described.     

Growth and morphological development of laboratory-reared larval and juvenile bighead catfish Clarias macrocephalus (Siluriformes: Clariidae)

Morphological development in laboratory-reared larval and juvenile bighead catfish Clarias macrocephalus is described. Body length (BL) of larvae and juveniles was 3.4 ± 0.3 (mean ± SD) mm just after hatching, reaching 11.3 ± 1.0 mm by day 16, and 24.2 ± 2.8 mm by day 40. Overall aggregate fin ray numbers (except for caudal fin procurrent rays) attained full complements by 15.2 mm BL. Gill buds appeared on day 0, those of barbels (four pairs) and primordial nostrils on day 1, and pectoral fins on day 3. All larvae began feeding by day 3. Conical teeth were observed on day 7. Notochord flexion began on day 2, the yolk being completely absorbed during days 7–9. Melanophores were scarce at hatching, increasing with growth to cover almost the entire body except the ventral surface of the abdominal cavity. Proportions of head length, pre-anal length, body depth, eye diameter, and maxillary barbel length became relatively constant after yolk absorption, those of snout length and upper jaw length increasing until ca. 12–13 mm BL and decreasing thereafter. Suprabranchial organ started developing in postflexion larval stage larger than ca. 11.0 mm BL (day 16), and air-breathing was suggested to be functional at that time.     

Morphometric Analysis and Identification on Specific Metric Characters Pertaining Growth of the Osteobrama cotio of the Brahmaputra, Barak and Teesta River of North Eastern Himalayan River Systems

The variations of morphometric features and the identification of the characteristic features involved in growth variation of Osteobrama cotio were studied from three Eastern Himalayan River Systems: The Brahmaputra, Barak and Teesta River systems. Altogether 220 specimens of different sizes were analysed. Each morphometric character including total length of 220 individuals ranging from 47 to 86 mm and the standard length (SL) from 31 to 65 mm, were recorded. We tested the hypothesis that the body proportion changes gradually rather than abruptly by fitting the linear and quadratic regression curves against the SL of each metric character. The subpopulation from all the locations appeared to be relatively uniform in all of the characters examined. Out of the nine metric characters examined, all the eight characters (head length, snout length, eye diameter, body depth, pre dorsal length, post dorsal length, dorsal fin length and caudal fin length) demonstrated the allometric growth of the fish as described by quadratic regression, except anal fin character which is isometric in growth.     

Early ontogeny of the big roughy Gephyroberyx japonicus (Beryciformes: Trachichthyidae) in captivity

Development of eggs and larvae of the big roughy Gephyroberyx japonicus are described on the basis of specimens reared in captivity. Spherical eggs (diameter 1.26–1.35?mm) with a single oil globule were pelagic. Newly hatched larvae (2.8–3.1?mm in body length, BL) had strong linear pigmentation on the head and trunk. The mouth opened at ca. 3.5?mm BL; thereafter the yolk was absorbed. Notochord flexion started at ca. 4.5?mm BL when body depth increased rapidly, and melanophores spread to all of the body. Notochord flexion was completed at ca. 5.0?mm BL. Head spination and pelvic fins began to develop during the flexion stage.     

Development of eggs,larvae and juveniles of the puffer,Takifugu chrysops,reared in the laboratory

The artificial fertilization of the puffer,Takifugu chrysops (Hilgendorf), was carried out at Sajima in Yokosuka City on May 22, 1984. Hatched larvae were reared for a period of about 150 days. The spawning period seems to extend from mid to late May in the eastern part of Sagami Bay. The eggs were spherical, pale milky white and semitransparent, demersal and adhesive in nature, measuring 1.32±0.04 mm in diamter, and with a cluster of small oil-globules. The incubation period was about 162 hours at a water temperature of 17.4 to 21.8°C. During embryonic development, the only pigment cells that appeared on the embryo were the black chromatophores. The newly hatched larvae measured from 2.72 to 3.06 mm TL, averaging 2.87±0.1 mm TL, and 22–23 (9 + 13?14) myomeres. At yolk absorption, 4 days after hatching, the larvae attained 3.64–3.79 mm TL. On the 11th day, postlarvae averaged 4.69±0.24 mm TL. Larval finfolds disappeared and rudimental dorsal, anal and caudal fins were formed. There were two large clusters of melanophores, one on the back, exteding from the mid-base of the dorsal fin to the caudal peduncle region, the other along the anal fin base. The color of the body began to turn pale green to brownish-orange and spinelike scales appeared on the belly. Eighteen days after hatching (7.02±0.27 mm TL), the caudal notochord began to turn up and a “constriction” appeared on the posterior margin of the caudal fin membrane. This notch moved upwards as the notochord upturning advances. The larvae attained full fin ray counts and reached the juvenile stage at 9.1-9.5 mm TL, 24 days after hatching. Characteristic black blotches on the back and specific brownish orange body color appeared at the stage of 20 mm TL, 24 days after hatching. The growth during the larval stage and early juvenile stage (24 to 51 days after hatching) were expressed by the following equations, wherey is total length (mm) andx is days after hatching.y ₁=2.8424× 1.0509⁹ (0≦x≦24)y ₂ = 3.7872×1.0372^x (24≦x≦51)     

Dispersion and settlement of two sympatric sculpins of the genus Gymnocanthus

Larval dispersion rather than adult migration generally leads to the worldwide expansion of fishes. Species of the genus Gymnocanthus have expanded geographically while undergoing allopatric speciation. Of this genus, while Gymnocanthus tricuspis inhabits the Arctic Ocean and surrounding area, G. herzensteini and G. intermedius occur around northern Japan. Larval early life histories of G. herzensteini and G. intermedius from northern Japan and G. tricuspis from Unalaska Island were investigated to estimate their dispersal potential during larval stages. The larval and juvenile abundances of G. herzensteini and G. intermedius were highest in May in shallow sandy bottoms below 7 m in depth, and the body sizes were 9.7–34.6 mm notochord length (NL) and/or standard length (SL) in G. herzensteini and 8.4–46.7 mm NL and/or SL in G. intermedius. Two egg masses of G. tricuspis (1.92 ± 0.08 mm in diameter) and hatched larvae (6.20 ± 0.19 mm NL) were collected in March. Compared with other sculpins in previous studies, the body sizes of G. herzensteini and G. intermedius at hatch are large and at settlement are small, while both hatch and settlement sizes of G. tricuspis are much larger. Counting micro-increments between the hatch check and settlement marks in G. herzensteini and G. intermedius demonstrated that the pelagic larval durations for 2 weeks with an immature body suggests that these species cannot disperse widely during the pelagic phase, while pelagic larvae of Arctic species such as G. tricuspis with long pelagic larval durations could disperse.     

Juvenile development of a flathead,Suggrundus meerdervoortii (Scorpaeniformes: Platycephalidae)

Juvenile development ofSuggrundus meerdervoortii was described, based on twelve specimens (12.9–43.8 mm SL) collected from off Yamagata Prefecture, Japan Sea. Two exterior openings in the lateral line scales were completed at ca. 35 mm SL, with the interopercular flap and iris lappet being visible at ca. 44 mm SL, these all being useful taxonomic characters. In juveniles and additional young and adult specimens (ca. 70–191 mm SL), the proportions of head length, snout length, orbital diameter, caudal peduncle depth and caudal fin length decreased with growth; interorbital width decreased rapidly until ca. 70 mm SL, but more or less stabilised thereafter (70–191 mm SL).