Early life history of kitsune-mebaru,sebastes vulpes (scorpaenidae), in the sea of japan

The larval and juvenile stages of kitsune-mebaru,Sebastes vulpes, based on 50 wild specimens collected in, the Sea of Japan, are described and illustrated, and some ecological aspects of the early life history (feeding, horizonal distribution and habitat shift) included. Preflexion larvae became extruded between 3.9–4.6 mm body length (BL) and notochord flexion occurred between 4.7–7.1 mm BL. Transformation from postflexion larvae to pelagic juventiles occurred between 13–17 mm BL. Compared with other rockfish species,S. vulpes is deep-bodied, throughout both larval and, juvenile stages. Larval and juvenileS. vulpes inhabit mainly coastal water surface layer (usually on the continental shelf), but do not occur offshore region (northwest of Oki Islands). Although someS. vulpes juveniles are associated with drifting seaweed, such clumps are not indispensable habitats for any stages. Surface-to-benthie migration of juveniles occurs at about 25 mm BL. Preflexion and flexion larvae feed mainly on copepod nauplii, and postflexion, transforming larvae and pelagic juveniles mainly on calanoid copepodites (Parracalanus parvus).     

Developmental morphology of the cyprinid fish Inlecypris auropurpureus

Embryonic, larval, and juvenile development of a Myanmarese cyprinid fish, Inlecypris auropurpureus, is described from laboratory-reared specimens. The eggs, measuring 0.9–1.0 mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk without oil globules. Hatching occurred 49–56 h after fertilization at 26.2°–27.3°C. The newly hatched larvae, measuring 2.9–3.1 mm in body length (BL) with 17 + 19–20 = 36–37 myomeres, had melanophores on the head and body. A cement organ on the forehead for adhering to objects during the yolk sac and early preflexion larval stages was distinctive. The yolk was completely absorbed at 3.6–4.0 mm BL. Notochord flexion was initiated at 5.1–5.6 mm BL and finished at 7.1 mm BL. Aggregate numbers of all fin rays were completed at 14 mm BL. Squamation was initiated midlaterally on the anterior trunk at 14 mm BL and completed at 27 mm BL. Although the eggs of I. auropurpureus resembled those of the closely related species Chela dadiburjori, Danio rerio, and Devario malabaricus, they differed from those of Danio rerio and Devario malabaricus in having a narrower perivitelline space. The larvae and juveniles of I. auropurpureus were also similar to those of C. dadiburjori, Danio rerio, and Devario malabaricus in general morphology, but they differed from the latter three species in having a series of dark blotches laterally on the body in the juvenile stage. Moreover, I. auropurpureus differed from C. dadiburjori in having more myomeres and a near-single row of melanophores on the body along the dorsal midline from the yolk-sac to early postflexion larval stages, from Danio rerio in having a cement organ on the forehead during the yolk-sac and early preflexion larvae, and a single melanophore on the lower eye margin in the early yolk-sac larvae, and from Devario malabaricus in having a single melanophore on the lower eye margin in the early yolk-sac larvae. The presence of a cement organ on the forehead indicates a close relationship among the genera Inlecypris, Chela, and Devario.     

Embryonic, larval and juvenile development of the roughskin sculpin,Trachidermus fasciatus (Scorpaeniformes: Cottidae)

Embryonic, larval and juvenile development of the catadromous roughskin sculpin,Trachidermus fasciatus, were described using eggs spawned in an aquarium. The eggs, measuring 1.98–2.21 mm in diameter, were light reddish-yellow and had many oil globules, 0.05–0.18 mm in diameter. Hatching occurred 30 days after spawning at 2.3–11.3°C. The newly-hatched larvae, measuring 6.9–7.3 mm BL, had a single oil globule, 9–10+25–26=34–36 myomeres and 6 or 7 large stellate melanophores dorsally along the gut. The yolk was almost resorbed, number of pectoral-fin rays attained 16–17, and two parietal, one nuchal and four preopercular spines were formed, 5 days after hatching, at 8.2–8.4 mm BL. The oil globule disappeared, and one supracleithral spine was formed, 11 days after hatching, at 8.9–9.5 mm BL. Notochord flexion began 15 days after hatching, at 9.7–10.3 mm BL. A posttemporal spine was formed 20 days after hatching, at 10.7–10.9 mm BL. The first dorsal fin spines (VII–VIII), second dorsal fin and anal fin rays (18–19, 16–18, respectively) appeared 23 days after hatching, at 12.0–13.7 mm BL. The pelvic fin spine and rays (I, 4) were formed and black bands on the head and sides of the body began to develop 27 days after hatching, at 13.8–15.8 mm BL. Newly-hatched larvae swam just below the surface in the aquaria. Preflexion larvae (8.9–9.5 mm BL), in which the oil globule had disappeared, swam in the middle layer, while juveniles (13.8–15.8 mm BL) began swimming on the bottom of the aquaria. Swimming behavior observed in the aquaria suggested that the fish started to change to a demersal existence at the juvenile stage.     

Osteological development of the lumpfish,inimicus japonicus (pisces: Synanceiidae)

The osteological development of the synanceiidInimicus japonicus, was described on the basis of five larvae and four juveniles (4.2–10.1 mm BL) reared in the laboratory, and two wild adult specimens. All bones, except for the basisphenoid, were formed in all larvae and juveniles, but fusions between the uppermost actinost and scapula, upper caudal plate and urostyle, and third preural centrum and hemal spine were not completed by 10.1 mm BL. Following comparison with the adult condition, a rod-like ossified bone without a tooth plate on the upper branchial arch of larvae and juveniles was considered homologous with the second pharyngobranchial. The number of epurals and length of the neural spine on the second preural centrum varied (unrelated to growth) and it is inferred thatJ. japonicus shows intraspecific variations in these bones.     

Growth and morphological development of larval and juvenileepinephelus bruneus (perciformes: Serranidae)

The growth and morphological development of larval and juvenileEpinephelus bruneus were examined in a hatchery-reared series. Average body length (BL) of newly-hatched larvae was 1.99 mm, the larvae growing to an average of 3.96 mm by day 10, 6.97 mm by day 20, 12.8 mm by day 30, 22.1 mm by day 40 and 24.7 mm by day 45 after hatching. Newly-hatched larvae had many mucous cells in the entire body epidermis. By about 4 mm BL, the larvae had developed pigment patterns peculiar to epinepheline fishes, including melanophores on the dorsal part of the gut, on the tips of the second dorsal and pelvic fin spines, and in a cluster on the ventral surface of the tail. Spinelets on the second dorsal and pelvic fin spines, the preopercular angle spine and the supraocular spine, had started to develop by about 6 mm BL. The notochord tip was in the process of flexion in larvae of 6–8 mm BL, by which time major spines, pigments and jaw teeth had started to appear. Fin ray counts had attained the adult complement at 10 mm BL. After larvae reached 17 mm BL, elements of juvenile coloration in the form of more or less densely-pigmented patches started to appear on the body. Squamation started at 20 mm BL. Major head spines had disappeared or became relatively smaller and lost their serrations by 20–25 mm BL.     

Growth and morphological development of laboratory-reared larval and juvenile snakeskin gourami Trichogaster pectoralis

Morphological development, including that of fins, labyrinth organ, body proportions, and pigmentation, in laboratory-hatched larval and juvenile snakeskin gourami Trichogaster pectoralis is described. Body lengths (BL; mean ± SD) of larvae and juveniles were 2.3 ± 0.1 mm just after hatching (day 0) and 8.2 ± 0.6 mm on day 22, reaching 14.1 ± 2.3 mm on day 48. Aggregate fin ray numbers attained their full complements in juveniles >11.8 mm BL. Preflexion larvae started feeding on day 2 following upper and lower jaw formation, the yolk being completely absorbed by day 12. Subsequently, oblong conical teeth appeared in postflexion larvae >8.2 mm BL (day 16). Melanophores on the body increased with growth, with a large dark spot developing on the lateral midline at the caudal margin of the body in flexion larvae >6.1 mm BL. Subsequently, a broad vertical dark band from the eye to the caudal peduncle developed in postflexion larvae >8.9 mm BL. Proportions of head and pre-anal lengths became constant in postflexion larvae greater than ca. 9–10 mm BL, whereas those of maximum body depth, eye diameter, and snout length failed to stabilize in fish of the size examined in this study. First soft fin ray of the pelvic fin elongated, reaching over 40% BL. The labyrinth organ differentiated in postflexion larvae >7.4 mm BL (day 22). Comparisons of larval and juvenile morphology with another anabantoid species Anabas testudineus were also made, revealing several distinct differences, particularly in the numbers of myomeres and fin rays in the dorsal/anal fins, mouth location and body shape.     

Developmental morphology of the cyprinid fish Tanichthys albonubes

Embryonic, larval, and juvenile development of a small cyprinid species, Tanichthys albonubes, is described from laboratory-reared specimens. The eggs, measuring 1.0–1.2 mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yolk without oil globules. Hatching occurred 45–53 h after fertilization at 25.5°–26.9°C. The newly hatched larvae, measuring 2.2–2.6 mm in body length (BL), had melanophores on the head and body. In particular, a dark vertical streak occurring posterior to the otic capsule and melanophores above the eyes were distinctive. The yolk was completely absorbed at 3.4 mm BL. Notochord flexion was initiated at 5.0 mm BL and finished at 6.0 mm BL. Aggregate numbers of all fin rays were completed at 11 mm BL. Squamation was initiated at 8.4 mm BL and completed at 13 mm BL. Although the eggs of T. albonubes resembled those of other small danionin species, including Aphyocypris chinensis, Chela dadiburjori, Danio rerio, Devario malabaricus, Gobiocypris rarus, Hemigrammocypris rasborella, and Horadandia atukorali, they differed from those of A. chinensis, C. dadiburjori, G. rarus, and Horadandia atukorali in having a wider perivitelline space. The larvae and juveniles of T. albonubes were similar to those of the aforementioned seven species plus Danio albolineatus, Danio kerri, and Devario sp. (cf. D. aequipinnatus) in general morphology. However, the early life stage morphology of T. albonubes differed from them in having a dark vertical streak posterior to the otic capsule and melanophores above the eyes in the yolk sac larval stage, and a dark lateral streak with an unpigmented area just above the former on the body, a dark blotch on the caudal fin, and reddish dorsal, anal, and caudal fins during the postflexion larval and juvenile stages.     

Descriptive morphology of the eggs,larvae, and juveniles of two cyprinid fishes belonging to the <Emphasis Type="Italic">Zacco temminckii</Emphasis> species' group

 Embryonic, larval, and juvenile development of two cyprinid species belonging to the Zacco temminckii species' group, Z. temminckii (Temminck and Schlegel) and Zacco sp. (type A), are described and compared with each other from laboratory-reared and wild specimens. The eggs of both species were closely similar except in diameter [1.92–2.20 mm in Z. temminckii vs. 1.60–1.75 mm in Z. sp. (type A)], being demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk, and no oil globule. Hatching occurred 40–53 h after fertilization in Z. temminckii and after 47–60 h in Z. sp. (type A). The newly hatched larvae of both species [4.9–5.3 mm in body length (BL) in Z. temminckii and 3.5–4.8 mm BL in Z. sp. (type A)] also resembled each other, having a large transparent pear-shaped yolk and lacking body pigmentation. Myomere counts of Z. temminckii and Z. sp. (type A) larvae and juveniles were 24–27 + 14–17 = 41–42 and 23–27 + 14–17 = 40–41, respectively. The yolk was completely absorbed at 8.3 mm BL in Z. temminckii and at 6.6 mm BL in Z. sp. (type A). Notochord flexion was initiated and completed at 7.8 mm BL and 8.2 mm BL in Z. temminckii and at 6.3 mm BL and 6.6 mm BL in Z. sp. (type A), respectively. Aggregate numbers of all fin rays were completed at 17 mm BL in Z. temminckii and 13 mm BL in Z. sp. (type A). Although the morphology of larvae and juveniles of both species was very similar, differences in body length of each developmental stage, the duration and process of disappearance of the adipose finfold, the anal fin ray counts, and pigmentation on the lateral body surface were clearly recognized. Received: August 10, 2001 / Revised: March 14, 2002 / Accepted: March 27, 2002     

Development of eggs, larvae and juveniles of laboratory-reared blue whiting,Sillago parvisquamis (Percoidei: Sillaginidae)

The embryonic, larval and juvenile development of blue whiting,Sillago parvisquamis Gill, are described from a series of laboratory-reared specimens. Mean egg diameter and mean total length (TL) of newly-hatched larvae were 0.71 mm and 1.58 mm, respectively. The eggs were non-adhesive, buoyant and spherical with an oil globule (mean diameter 0.18 mm). Hatching occurred about 20 hours after fertilization at a temperature of 24.0–25.0°C, newly-hatched larvae having 38–40 myomeres. The yolk and oil globule were completely absorbed 3 days after hatching at 2.8–3.2 (mean 3.0) mm TL. Notochord flexion was completed by 7.2–8.2 (7.7) mm TL, and pectoral and caudal fin rays fully developed by approximately 10 mm and 8.5 mm TL, respectively. Completion of fin development occurred in the following sequence: caudal, pectoral, anal and second dorsal, first dorsal and pelvic, the last-mentioned by approximately 11 mm TL. The larvae ofS. parvisquamis andS. japonica, which closely resemble each other in general morphology and pigmentation, could be distinguished as follows. Newly-hatchedS. parvisquamis larvae had more myomeres thanS. japonica (38–40 vs. 32–34) and more melanophores on the dorsal surface of the body (19–28 vs. about 40).Sillago japonica had a vertical band of melanophores on the caudal peduncle, which was lacking in postflexionS. parvisquamis larvae. In addition, juveniles ofS. parvisquamis (larger than 23 mm TL) had melanophores on the body extending anteriorly to below the lateral line to form a midlateral band, whereas no obvious band occurred on similarly-sizedS. japonica juveniles.     

Growth and morphological development of laboratory-reared larval and juvenile three-spot gourami <Emphasis Type="Italic">Trichogaster trichopterus</Emphasis>

Morphological development, including the body proportions, fins, pigmentation and labyrinth organ, in laboratory-hatched larval and juvenile three-spot gourami Trichogaster trichopterus was described. In addition, some wild larval and juvenile specimens were observed for comparison. Body lengths of larvae and juveniles were 2.5 ± 0.1 mm just after hatching (day 0) and 9.2 ± 1.4 mm on day 22, reaching 20.4 ± 5.0 mm on day 40. Aggregate fin ray numbers attained their full complements in juveniles >11.9 mm BL. Preflexion larvae started feeding on day 3 following upper and lower jaw formation, the yolk being completely absorbed by day 11. Subsequently, oblong conical teeth appeared in postflexion larvae >6.4 mm BL (day 13). Melanophores on the body increased with growth, and a large spot started forming at the caudal margin of the body in flexion postlarvae >6.7 mm BL, followed by a second large spot positioned posteriorly on the midline in postflexion larvae >8.6 mm BL. The labyrinth organ differentiated in postflexion larvae >7.9 mm BL (day 19). For eye diameter and the first soft fin ray of pelvic fin length, the proportions in laboratory-reared specimens were smaller than those in wild specimens in 18.5–24.5 mm BL. The pigmentation pattern of laboratory-reared fish did not distinctively differ from that in the wild ones. Comparisons with larval and juvenile morphology of a congener T. pectoralis revealed several distinct differences, particularly in the numbers of myomeres, pigmentations and the proportional length of the first soft fin ray of the pelvic fin.     

Growth and morphological development of laboratory-reared larval and juvenile climbing perch <Emphasis Type="Italic">Anabas testudineus</Emphasis>

Morphological development, including fin and labyrinth organ, body proportions and pigmentation, in laboratory-reared larval and juvenile climbing perch Anabas testudineus was described and behavioral features under rearing condition were observed. Body lengths (BL) of larvae and juveniles were 1.9 ± 0.1 (mean ± SD) mm just after hatching (day-0), 8.7 ± 1.3 mm on day-19, reaching 18.4 ± 2.1 mm on day-35 after hatching. Aggregate fin ray numbers attained full complements in juveniles larger than 8.3 mm BL. Preflexion larvae started feeding on day-2 following formation of the upper and lower jaws, the yolk being completely absorbed by day-7 after hatching. Teeth appeared in flexion larvae larger than 5 mm BL on day-6, with cannibalism starting shortly after and continuing with further growth. Melanophores on the body increased with growth, a large dark spot developing on the lateral midline around caudal margin of the body in the postflexion and juvenile stages. The labyrinth organ differentiated in postflexion larvae larger than 7.2 mm BL on day-16, with air-breathing starting at the same time. Body proportions attained constant in postflexion larvae larger than 7.0 mm BL, and habitat of fish shifted from bottom to mid-layer. With the exception of fin ray numbers, the above morphological developments corresponded to behavioral shifts that occurred in the postflexion stage (ca. 7 mm BL), their subsequent continuity illustrating that the species possessed most juvenile-equivalent functions from ca. 7 mm BL.     

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.     

Developmental morphology of the Indian cyprinid fish Barilius canarensis

Embryonic and larval development of an Indian cyprinid fish, Barilius canarensis, is described from laboratory-reared specimens. The eggs, measuring 2.1–2.4 mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk without oil globules. Hatching occurred 39–45 h after fertilization at 26.8°–27.4°C. The newly hatched larvae, measuring 4.8–5.1 mm in body length (BL) with 22 + 17 = 39 myomeres, were characterized by melanophores already deposited on the eyes. The eggs of B. canarensis resembled those of the related danionin species Candidia barbatus, Opsariichthys uncirostris uncirostris, Zacco platypus, Z. sieboldii, and Z. temminckii. Although the larvae of B. canarensis were also similar to those of the foregoing species in general morphology, they differed in having a straight notochord tip and pigmentation on the eyes at hatching and the almost entire absence of melanophores on the ventral body surface from the yolk sac to postflexion larval stages. Conversely, melanophores occurred on the anterior abdominal and pericardial cavities from the preflexion to postflexion larval stages.     

Vulnerability of larval white perch,Morone americana,to fish predation

Synopsis The vulnerability of white perch, Morone americana, larvae to yearling bluegill, Lepomis macrochira, predators was examined in relation to larval size, nutritional condition and relative abundance of alternative prey. Short-term (15 min) predation trials were conducted in 381 tanks in the laboratory. Larval vulnerability was measured as the proportion of larvae killed and the proportion of successful attacks per predator in each 15 min trial. No significant differences in vulnerability were apparent among larvae regardless of feeding history at sizes < 6 mm SL. At larval lengths > 6 mm SL, size of larvae was the crucial determinant of their vulnerability. Percentage of larvae killed in 15 min was nearly 100% at sizes < 6 mm SL, decreased to 30% at a length of 12.0 mm SL and dropped to 18% at 14.0 mm SL. Larvae initially feeding at low food levels for 2–4 d exhibited decreased growth of 13–25% over the first 3 wks of life, and simulations based on laboratory results indicated that these growth deficits could result in 5- to 68-fold decreases in survivorship at 38 days after hatching (DAH). The relative abundance of alternative prey also had a pronounced effect on mortality of larvae. A 10-fold increase in alternative prey (Daphnia magna) abundance decreased bluegill predation rates on white perch larvae by 10–20%, while a 100-fold increase in Daphnia density decreased larval mortality by 75–90%.     

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).     

Developmental morphology of the cyprinid fish, Candidia barbatus

 Embryonic, larval, and juvenile development of a Taiwanese cyprinid fish, Candidia barbatus, is described from laboratory-reared specimens. The eggs, measuring 1.8–2.1 mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk and no oil globule. Hatching occurred 56–69 h after fertilization, the newly hatched larvae measuring 4.9–5.3 mm in body length (BL) with 25–26 + 13–14 = 39–40 myomeres. The yolk was completely absorbed at 7.6 mm BL. Notochord flexion was initiated at 6.8 mm BL and finished at 7.6 mm BL. Aggregate numbers of all fin rays were completed at 12 mm BL. Barbels on the upper jaw appeared near the corner of the mouth at 17 mm BL. Eggs of the species closely resembled those of its related cyprinid genera, Opsariichthys and Zacco. Larvae and juveniles of C. barbatus were similar to those of O. uncirostris subspp., Z. platypus, and Z. pachycephalus, but differed from the latter in the process of disappearance of the adipose finfold (postflexion larval stage), barbels on upper jaw (juvenile stage), and pigmentation on the lateral body surface (postflexion larval and juvenile stages). Although C. barbatus also differed from the Z. temminckii species' group [Z. temminckii and Zacco sp. (sensu Hosoya, 2002)] in having barbels, larvae and juveniles of the former showed more similarity to the latter species group than to O. uncirostris subspp., Z. platypus, and Z. pachycephalus, from the aspect of head and body pigmentation.     

Diet composition,feed preferences and mouth morphology of early stage silver therapon (Leiopotherapon plumbeus,Kner 1864) larvae reared in outdoor tanks

This study examined the diet composition, feeding preferences, and mouth morphology of the silver therapon (Leiopotherapon plumbeus, Kner 1864) larvae under captive conditions. Larvae were reared in outdoor tanks (4 m³) with natural food grown 2 weeks prior to start of larval rearing. Food preference was measured by the Chesson's electivity index (α_i). Gut content analysis of larvae sampled between 5 and 25 days after hatching (DAH) showed the dominance in the diet by zooplankton, mainly copepod nauplii, cladocerans and insect larvae. Small fish larvae (5–9 DAH; 3.32–6.29 mm standard length) preferred cladocerans, ciliates and copepod nauplii; whereas older larvae (12–25 DAH; 5.45–19.26 mm standard length) preferred insect larvae over cladocerans and adult insects. The mouth gape size at 5 DAH was 359 μm and increased to 3.75 mm at 40 DAH when body size grew at an average rate of 0.59 mm d^?1. The standard length (SL) of L. plumbeus larvae was strongly associated with mouth size (r² = 0.98, P < 0.05), indicating a progressive increase of ingested prey size of the fish larvae. These results clarified the early life feeding ecology of this species, which is essential in developing effective hatchery techniques.     

Reproduction and early development of a freshwater pipefish <Emphasis Type="Italic">Microphis leiaspis</Emphasis> in Okinawa-jima Island,Japan

We investigated the size at maturation, breeding season, and morphological development of larvae and juveniles of a freshwater pipefish Microphis leiaspis, which belongs to Gastrophori, collected from three rivers on the northern part of Okinawa-jima Island, Japan. The minimum size of brooding males was 105–123 mm in standard length (SL). The smallest mature female was estimated to be ca. 130 mm SL from the analysis of gonadosomatic index (GSI) and histological observations of gonads. The breeding season was estimated to be from June to December according to monthly changes in female GSI, histological observations of gonads, and monthly changes in the occurrence of brooding males. The number of eggs in the male brood pouch ranged from 75 to 241 (mean ± SD: 152 ± 52, n = 22). The male releases newly hatched larvae in freshwater areas. After newborns grow in the sea, they return to freshwater areas of the rivers and attain maturity. Microphis leiaspis was conformed to have an amphidromous life history. Notochord length of the released larvae was 6.1 mm, with a well-developed finfold. Larvae attained 11.1 mm SL, formation of the caudal and dorsal fin rays was complete, and the caudal fin became lozenge shaped at 30 days after the release, and juveniles reached 36.0 mm SL at 63 days after release. In the period between 30 and 63 days after the release, formation of all fins except the pectoral fins was completed, and caudal fin rays were extended and sector shaped with deep slits between each fin ray. The morphology of the released larvae of M. leiaspis is similar to that of Gastrophori species, and the morphology of juveniles similar to other species of Microphis.     

Growth and morphological development of laboratory-reared larval and juvenile <Emphasis Type="Italic">Hemibagrus filamentus</Emphasis> (Siluriformes: Bagridae)

Morphological development in laboratory-reared larval and juvenile Hemibagrus filamentus, and behavioral features observed under rearing conditions are described. Body lengths (BL) of larvae and juveniles were 3.8 ± 0.2 (mean ± SD) mm just after hatching and 11.7 ± 1.6 mm on day 15, reaching 26.5 ± 5.4 mm on day 30 after hatching. Aggregate fin ray numbers (for caudal fin, except for procurrent rays) attained full complements in specimens larger than 12.9 mm BL. A maxillary barbel bud appeared on day 0, and all larvae initiated feeding on day 3 with the development of mandibular barbels and conical teeth. Pectoral fin buds and primordial nostrils were present on day 1. Notochord flexion began on day 3, and the yolk was completely absorbed by day 4. Melanophores were scarce at hatching, but increased with growth to cover almost the entire body except the ventral surface of the head and body. Body proportions became relatively constant in juveniles, excepting maxillary barbel length that continued to increase, reaching over 40% BL. Fish were negatively phototactic from day 1. Cannibalism was observed from day 6, continuing to the juvenile stage.     

Ontogenetic diet shift, feeding rhythm, and daily ration of juvenile yellowfin goby Acanthogobius flavimanus on a tidal mudflat in the Tama River estuary, central Japan

To ascertain the feeding habits of benthic juvenile yellowfin goby Acanthogobius flavimanus, the gut contents of 599 specimens (15–41 mm in standard length, SL), collected on a tidal mudflat in the Tama River estuary throughout the diel cycle, were examined. The major prey items changed from harpacticoid copepods to errant and sedentary polychaetes at ca. 20 mm SL. Prey width increased with fish size. Fish of 26–28 mm SL fed mainly from sunset to morning, with highest feeding intensity during twilight hours and/or high tide. Based on the gut evacuation rate estimated from a forced feeding experiment in the laboratory and data for the diel change of mean gut-content volume in the field, the daily ration of juvenile yellowfin goby (26–28 mm SL) was calculated to be 13.8 mm³ fish⁻¹ day⁻¹. This volume is approximately equivalent to 3.9 individuals of the errant polychaete Ceratonereis erythraeensis (9.7 mm in body length, BL) or 8.1 individuals of the sedentary polychaete Prionospio japonica (14.8 mm BL), both species occurring abundantly on the mudflat during the study.