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.     

Larval development of the Common Ponyfish, Leiognathus equulus (Teleostei: Leiognathidae)

Larval development of Leiognathus equulus is described from reared postflexion specimens (4.6–15.8 mm Standard Length, SL) from Taiwan. Larvae have strong head spination, particularly a supraoccipital crest, strong supraocular ridge and very long, serrate preopercular spines, with the spine at the preopercular angle initially heavily pigmented. Fin spines are robust, and the anterior spines of dorsal, anal and pelvic fins are long and serrate. Structures characteristic of the family Leiognathidae form early in development (ca. 5 mm SL), including the very protrusible mouth, the fin-locking mechanism and the bacterial light organ. Pigment is initially largely confined to the ventral midline, but as development proceeds, extensive lateral and dorsal pigment patches appear. Larvae of L. equulus have the Trnski and Leis Morph 1 morphology.     

Larval developmental stages of laboratory-reared silver pomfret,pampus argenteus

Eggs of the silver pomfret,Pampus argenteus, were collected and artificially fertilized by stripping fully-ripe male and female broodstock caught by gillnets in Kuwait waters during June 1997. Larvae hatched from fertilized eggs were reared until 90 days after hatching (DAH) in water temperatures of 27–30°C. Newly-hatched larvae grew from an average of 2.4 mm in body length (BL) to 3.7, 4.4, 7.2 and 8.4 mm at 8, 12, 24 and 30 DAH, respectively. Myomere and vertebral numbers ranged from 34 to 36. Transformation from the larval to juvenile form was completed at 22.2 mm BL (40 DAH). Dorsal and anal fin spines first appeared when juveniles reached 38.8 mm BL (50 DAH). Body depth increased with increase in body length; a rapid increase in body depth occurred in larvae 7.1–8.0 mm, reaching 57% of BL, and further increased to 69% of BL in juveniles 38.8 to 47.9 mm. Pigmentation during development is described and illustrated.     

Larval development of Pseudorhombus oculocirris and P. arsius (Pleuronectiformes, Paralichthyidae) from off southern Japan

 Larvae of two paralichthyids, Pseudorhombus oculocirris and P. arsius, are described and illustrated from specimens collected off Tosa Bay, southern Japan. Peudorhombus oculocirris larvae (5 specimens, 4.5–7.8 mm BL) are characteristic in having 6 or 7 elongated anterior dorsal fin rays and poorly developed head spines and melanophores on the tail. Pseudorhombus arsius larvae (3 specimens, 5.3–8.4 mm BL) are distinctive in having 11 or 12 elongated anterior dorsal fin rays and well-developed head spines, including a row of spines on the sphenotic. Received: June 28, 2001 / Revised: November 2, 2001 / Accepted: November 22, 2001     

Premetamorphic bonefish (Albula sp.) leptocephali from the Gulf of California with comments on life history

Synopsis Ten early premetamorphic bonefish (Albula sp.) leptocephali were collected in MOCNESS plankton tows in the Guaymas Basin area of the Gulf of California from 27 July–1 August, 1985. Initial captures of five larvae showed that these were found only in surface waters (0–100 m) at temperatures of 15–29° C. A shallow tow made from 200 m to the surface resulted in the capture of five additional larvae that were distributed in the upper 50 m of the water column at temperatures of 21–29° C. Both pre-flexion larvae (<17.0 mm notochord length, NL) and larvae with flexed notochords were captured. The size range was from 12.0 mm NL to 27.0 mm standard length. Drawings of representative larvae are given. This is apparently the first report of premetamorphic bonefish larvae for the Gulf, although metamorphic larvae have been known to be abundant in coastal areas of this region for almost 100 years. Distribution records for metamorphic larvae are reviewed. This, together with observations on seasonal distribution of ripe adults in coastal waters near Guaymas, Sonora, Mexico, has allowed us to speculate on various aspects of life history. Our data suggest that spawning occurs during late spring and summer and that early development takes place offshore. The premetamorphic interval is postulated to last approximately 6–7 months. Larvae then return to coastal areas during the winter and spring to complete metamorphosis.     

Osteological development in the Japanese sardine,Sardinops melanostictus

The development of all osteological elements, except scales, of the Japanese sardine,Sardinops melanostictus, is described from newly-hatched larvae to adult fishes. Newly-hatched larvae lacked osteological elements. Part of the head skeleton began to develop in 53 hour old larvae (4.2 mm in notochord length [NL]). Larvae at the first-feeding stage (77 hours, 5.5 mm NL) possessed several elements of the head skeleton and pectoral fin supports. In a 10.5 mm NL specimen, part of the caudal and dorsal fin supports were apparent. The centra appeared in specimens 18–22.7 mm in standard length (SL). Gill rakers were first observed in the lower branchial arches at 13 mm NL and spine-like processes with spiny nodules from about 25 mm SL. The distance between the predorsal and first dorsal proximal radial relative to SL rapidly decreased with forward translocation of the dorsal fin and became constant beyond approximately 34 mm SL. At this stage, most basic osteological elements were established. Completion of the osteological structure was characterized by the disappearance of the dentary teeth at 60–70 mm SL. Based on the osteological development, ontogenetic intervals consisting of four periods and eight phases were recognized.     

Morphological development and growth of chub, Leuciscus cephalus (L.), larvae

This study describes the morphological development and early growth of laboratory-raised chub, Leuciscus cephalus (L. 1758), larvae. Larvae hatched with relatively large yolk sacs, stayed motionless at the tank bottom and exhibited short and sudden bursts from time to time. They were olive in colour and with complete absence of melanophores on the body. Larvae were transparent but showed brownish eye pigment. Intense body pigmentation first appeared on day 4 after hatching. By day 8 the yolk sac was fully absorbed; only 30% of the initial population of larvae successfully established exogenous feeding. Fin rays first appeared on the dorsal and anal fins of larvae around day 12. Growth during the yolk sac stage was initially fast but slowed down with the increasing size of larvae at the time of yolk absorption. The specific growth rate (SGR) of larvae declined with time, although the total observation period was relatively short (12 days). SGR values ranged from 5.18 (day 2) to 2.97 (day 12). Only a negligible egg mortality was observed during the period of early endogenous feeding (between days 1 and 6), and about 45% towards the end of endogenous feeding and immediately after the yolk sac phase (between days 7 and 9). During the exogenous feeding period (between days 10 and 12) deaths were negligible.     

Dispersal and biogeography of silica-scaled chrysophytes

The silica-scaled chrysophytes—here mainly represented by the freshwater genera Mallomonas and Synura—have special problems in dispersal from one habitat to another because they cannot tolerate desiccation. Their dispersal is limited by the fragile construction and aquatic habit. Dispersal from one water body to another involves dangerous changes of the environment, and the ability to avoid desiccation during transport is crucial. So, air-borne and ectozoic dispersal by birds or mammals can only work at short distances. This danger may be avoided by endozoic dispersal of thick-walled cysts; as far as they can tolerate the digestion fluids in the intestine. In spite of these difficulties, Chrysophytes have been dispersed worldwide, but they display various distinct distribution patterns, e.g., cosmopolitan, arctic-northern temperate, bipolar, and tropical. Quite a large proportion may be considered endemic, occurring only within a restricted area. Even if the exact dispersal methods are elusive, the distribution of chrysophytes around the world proves their ability for dispersal. On the other hand, the different degree of distribution shows the varying success of the individual species. The distribution of a species at a given time depends on several factors: dispersal capacity—available vectors—suitable available habitats—and most important: sufficient time for dispersal. It is remarkable that the chrysophytes—in spite of their fragile cell construction and apparently low dispersal capacity—show distribution types comparable to those found in, e.g., blue–greens and desmids, whose cell construction appears much better adapted for dispersal. Special Issue: Protist diversity and geographic distribution. Guest editor: W. Foissner     

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.     

Early ontogeny of Lophonectes gallus (Bothidae) from southeastern Australia

 The early ontogeny of Lophonectes gallus (Bothidae) is described based on 83 specimens (1.9–17.5 mm BL), collected from the Tasman Sea off southeastern Australia. The larvae are diagnosed by the following array of characters: vertebrae 10 + 30–31 = 40–41; one elongated dorsal fin ray and several melanophores present on gut in preflexion stage (1.9–4.7 mm BL); and spines on posterior basipterygial process, and urohyal, cleithrum, and epiotic without spines after postflexion stage (8.0–17.5 mm BL). The larvae are relatively small at metamorphosis (15–18 mm BL) compared with other bothid larvae. Received: March 22, 2001 / Revised: December 12, 2001 / Accepted: December 26, 2001     

Abundance and daytime vertical distribution of planktonic fish larvae in an oligotrophic South Island lake

The vertical distribution of common bully (Gobiomorphus cotidianus) and koaro (Galaxias brevipinnis) larvae in the limnetic zone of Lake Coleridge were determined using a high-frequency (200 KHz) echosounder. Planktonic bully larvae first appeared in appreciable numbers in January. By February, they formed a scattering layer between depths of 12 to 24 m during the day, where they achieved a maximum density of 0.59 fish m^-3. Larger (> 18mm) fish migrated to the littoral zone and densities declined to < 0.01 fish m^-3 by July, when remaining larval fish occupied greater daytime depths. Their vertical distribution during the day appeared to be influenced mainly by light levels and water temperatures. Larvae grew more slowly (0.12 mm d^-1) than in more productive North Island lakes, and were also present in lower densities for a more restricted period of time. Koaro larvae first appeared in November and December and were found in low numbers (< 0.01 fish m^-3) in summer at depths of 10 to 26 m. Salmonid production in the limnetic zone is probably limited by the small size and relative scarcity of forage fish present.     

Occurrence and morphology of larvae and juveniles of six <Emphasis Type="Italic">Luciogobius</Emphasis> species from Aritsu Beach,Okinawa Island

Larvae and juveniles of six species of Luciogobius were collected at Aritsu Beach on Okinawa Island using a small seine. Postflexion larvae were dominant during sampling and were collected when they approached the shoreline adjacent to or at the entrances to their adult habitats prior to settlement. Standard lengths of postflexion larvae ranged from 5.4 to 14.4 mm and varied depending on the species. The larvae occurred mainly from January to April, but some larvae were caught in October and November. Their pelagic larval durations were estimated to range from 17 to 36 days and varied depending on the species. Morphologies of field-caught larvae and juveniles and laboratory-reared juveniles were described. Six species were clearly distinguished based on fin ray and vertebral counts, proportions, body size, and pigment patterns. Although their taxonomic statuses could not be determined, it is thought that they have independent relatives in other regions.     

Oogenesis and larval development in Micromaldane spp. (Polychaeta: Capitellida: Maldanidae)

Summary

The morphology of larval development and some aspects of oogenesis are described in Micromaldane spp. from eastern Australia. All four species breed throughout the year, and in all the oocytes are released into the coelom prior to vitellogenesis. Micromaldane androgyne, M. pamelae and M. rubrospermatheca all have solitary oogenesis, while Micromaldane nutricula has “nurse” cells attached to the oocytes throughout vitellogenesis. Mature females of Micromaldane nutricula brood up to two groups of 1–4 directly developing larvae at a time. Newly fertilized eggs are ellipsoidal, 150x350 μm. No ciliation is visible during development. Larvae leave the tube after developing 12 chaetigers. All Micromaldane androgyne adults brood a single batch of two or three directly developing larvae at a time. Newly deposited eggs are 1 mm long and 150 μm in diameter. No ciliation is visible on the larvae during development. Larvae develop 19 chaetigers before leaving the tube. Mature females of Micromaldane pamelae brood single batches of up to 31 larvae at a time. Mature oocytes are ellipsoidal 300 X 150 μm. Larvae show a distinct neurotroch in early stages of development, but this is resorbed as chaetigers are formed. Larvae probably leave the tube at the 16-chaetiger stage.

Comparisons are made with other polychaetes and members of the Capitellida. Micromaldane spp. may be useful in the study of reproductive effort and covariables, outlined for polychaetes by Olive (1985), such as body size with longevity and fecundity (inversely) with brood frequency.     

Fish-induced variation in abdominal spine length of Leucorrhinia dubia (Odonata) larvae?

The lengths of dorsal and lateral spines on abdominal segments 4, 6 and 9 were measured on last-instar larvae of Leucorrhinia dubia (Odonata) from seven natural lentic systems containing fish and nine systems lacking fish. Larvae from systems with fish had significantly longer spines than larvae from systems without fish. In contrast, lake/pond area and pH had no effect on the length of spines. The length of the spines was not correlated with larval size, but there was a high correlation between the length of the three spines measured. Also, abundances of L. dubia larvae differed between systems, being significantly lower in systems with fish. Laboratory experiments showed that perch (Perca fluviatilis) handled long-spined larvae for significantly longer times than short-spined larvae. The results suggest that fish predators may induce morphological defences in insects.     

Size- and locomotion-related aspects of hominid and anthropoid pelves: An osteometrical multivariate analysis

Two multivariate methods — the logarithmic principal component analysis (LPCA), and the logarithmic factorial analysis (LFA) — have been used tocompare the hip bone proportions of hominoids biometrically. The results have shown that size effects among apes and hominids interact to a centain extent with locomotor specializations, which are related to the attainment of more or less terrestrial behaviors. The pelvic morphology of great apes (Pongo, Pan, Gorilla) has retained numerous morphological traits — such as a gracile and elongated hip bone —, which were inherited from common adaptations to arboreal locomotion. In spite of these common traits, the African pongids (Pan, Gorilla) present two very different pelvic morphologies corresponding to two adaptative modes of terrestrial quadrupedalism. The hip bone of humans is proportionnally short and robust, most particularly at the level of its axial part. These characteristics, as well as the whole pelvic proportions, clearly indicate that gravitational forces exert a strong pressure on the pelvic walls during bipedalism. Among hominids, the transition from an australopithecine-like pelvic pattern to a human-like one corresponds to an increase of loading constraints on the hip jiont. This seems to indicate an evident change in locomotor behavior. Progression apparently became exclusively terrestrial with the genusHomo.     

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.     

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.     

Susceptibility of the leatherjackets Tipula oleracea and T. paludosa to soil flooding

A relation was found between temperature and the survival of larvae of Tipula oleracea and T. paludosa when submerged in tap water alone or on turf growing on a sandy loam flooded with still or disturbed water (experiments with soil always starting with freshly flooded soil). Larvae under water alone usually survived until they starved, whereas larvae submerged on soil died in a relatively short time. The periods of survival at a depth of 25 mm were the same for both large and small larvae of either species at any one temperature. The regression of log.-log. survival time on temperature was a straight line, mean arithmetic values ranging from about 5 h at 20 °C to 122 h at 0 °C. Survival times at 25 mm were not increased by disturbing the water and the times at greater depths were no different, providing the water was still. If the water was regularly disturbed then the greater the depth the longer the survival time at any one temperature. Survival times in deoxygenated water indicated that lethal conditions may not be entirely due to deoxygenation of the water.     

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.