Reproduction of spined loach, Cobitis taenia, (Cypriniformes; Cobitidae) under laboratory conditions

A simple and reliable method is described for breeding spined loach, Cobitis taenia Linnaeus, 1758, under laboratory conditions. Three 40 L aquaria were each provided with a thick tuft of moss placed on top of a gauze-covered plastic box to serve as a spawning site. Ovoposition always occurred in the most densely available vegetation. The nonadhesive eggs fell through the gauze into the box. The spined loach is a fractional spawner releasing eggs in 14–18 batches at intervals of 2–23 (median 6) days. The total number of eggs per female was 2905–4282 during the reproductive season of 101–120 days. Yolks measured 1.14 ± 0.07 mm and eggs were 2.54 ± 0.22 mm in diameter. Total larval length was 5.03 ± 0.34 mm at hatching and 6.77 ± 0.34 mm at the beginning of exogenous feeding. The method allowed the rearing of numerous young for conservation measures and experimental investigations.     

Early ontogeny of Galeichthys feliceps from the south east coast of South Africa

The early development of Galeichthys feliceps (Valenciennes, 1840) was investigated using a combination of incubator-reared embryos and embryos removed from the buccal cavities of wild-caught parents. The eggs were 15·7 mm in diameter and the average brood size was 49. Hatching occurred at an advanced developmental state after approximately 75–80 days, when branchial and fin differentiation were complete. Exogenous feeding began within the adult buccal cavity shortly after hatching. The young were released as juveniles after approximately 140 days, at a total length of 54 mm.     

贝氏高原鳅胚胎和仔鱼的形态发育

通过人工授精获得受精卵,对贝氏高原鳅胚胎和仔鱼的发育过程进行了观察和描述。结果表明,成熟卵淡黄色,卵径较小(直径0.94－1.10mm),遇水后产生强黏性。在水温9.0－12.8℃下,胚盘在受精后4h20min开始分裂,在19h50min和27h40min时达到囊胚期和原肠期,64h40min胚孔封闭,287h时部分胚胎开始出膜,405h30min全部出膜。初孵仔鱼全长(4.32±0.23)mm,肌节36－38对,眼和躯干部黑色素细胞明显,胸鳍原基发育良好。出膜后第5天仔鱼体侧和头部出现浓密的感觉芽。到第8天时全长(6.05±0.41)mm,卵黄吸收完全。仔鱼鳔一室和鳔二室分别于出膜后第30天和第50天形成。第55天的仔鱼全长(14.05±1.01)mm,肌节52－53对,体侧出现7－8条黑色素带,各鳍鳍条数目与成鱼基本一致,但仍有少量鳍褶存在。仔鱼的卵黄囊体积减小速度为0.027mm3/d,鱼体长度生长、鱼体长度性状间的比例关系并不相同,其中,肛后长／全长比例随胚后发育逐渐增加,由初出膜时的31%增加到最后的42％左右。     

The effect of temperature on development and hatching of scad, Trachurus trachurus L., eggs

The effect of temperature on the rates of development and hatching of artificially fertilized eggs of the scad, Trachurus trachurus L., was studied using a thermal gradient incubator. Development of eggs through to hatching occurred within the temperature range 10.5–21.2° C, with greatest survival between 12.2 and 15.8° C. The mean egg diameter was 0.94 mm and mean length of larvae on hatching 2.46 mm. Regressions of development time on mean incubation temperature are presented. The data are compared with those reported in the literature and related to sea temperatures in scad spawning grounds.     

Development of eggs and larvae of the flounders Rhombosolea tapirina and Ammotretis rostratus (Pisces: Pleuronectidae)

The stages of development of laboratory-reared eggs and larvae of Rhombosolea tapirina and Ammotrelis rostratus are described. They both exhibited á typical pleuronectid pattern of development. At ambient seawater temperature of 11.1–13.8° C R. tapirina eggs hatched 83–93 h after fertilization and larvae metamorphosed c. 65 days later at mean length of 8.83 mm. Hatching of A. rostratus eggs occurred 93–105 h after fertilization and larvae metamorphosed after c. 69 days (mean length 11.21 mm) at 12.7–16.5° C. The two species can be readily separated by their morphology, meristics and pigmentation. In particular, the eggs differ in diameter, only R. tapirina larvae possess a pair of spines in the otic region, and juvenile A. rostratus have only a left pelvic fin.     

Development of eggs,larvae and juveniles of the labrid fish,Halichoeres poecilopterus,reared in the laboratory

Embryonic, larval and juvenile development of the labrid fish,Halichoeres poecilopterus, is described using a laboratory-reared series. The eggs, measuring 0.60–0.72 mm in diameter, were pelagic and spherical with a single oil globule (0.12–0.16 mm in diameter). Hatching occurred 18 h 48 min after spawning. The newly-hatched larvae, measuring 1.46–1.70 mm TL, had 8–114 + 16–18 myomeres. A conspicuous melanophore appeared on the dorsal finfold 8 h after hatching, at ca. 2 mm TL. The yolk was completely absorbed 3 days after hatching, at 2.52–2.72 mm TL. Flexion of the notochord started at ca. 6 mm TL and was finished at ca. 8 mm TL. Aggregate numbers of all fin rays were completed at ca. 14 mm TL. Squamation was almost completed at ca. 20 mm TL.     

Embryonic and larval development of Thai Pangas (Pangasius sutchi Fowler, 1937)

The embryonic and larval development of Thai pangas was investigated during peak (May-July 1995) and late spawning (August-October 1995) periods. The fertilized eggs are adhesive and spherical with a yellowish or greenish-brown egg capsule. The yolk sac is yellowish-brown in color and 1.20-1.80 mm in diameter. Nine hours post-fertilization, the first cleavage stage, embryonic shield, head, tail region, neural grooves and somites were evident. The incubation period ranges from 24-36 h at a temperature of 20-30 degrees C. The newly hatched larvae are quite transparent and light yellowish in color with a body length of 2.98-3.10 mm. Eye pigments appear and the heart starts to work within 12-14 h of hatching. In 1-day-old pro-larvae, the mouth becomes well developed; barbules are elongated, prominent and look like tiny threads. The yolk sac is fairly well absorbed and the palatine teeth are fully developed during the 3 day pro-larval stage. At the end of 12 days of larval development, the stomach becomes functional and aerial respiration starts. After 2 weeks, the young fry is well-developed, and is of an adult appearance, that is, measuring up to 13.56 mm in length.     

Osmotic changes during the development of eggs and larvae of the lumpsucker, Cydopterus lumpus L.

The demersal eggs of Cyclopterus appear to osmoregulate like the pelagic eggs of cod and plaice. Unfertilized eggs in ovarian fluid exhibited ovoplasm osmolarities similar to those of adult blood and ovarian fluid (356–359 mosmol kg⁻¹). Yolk osmolarities remained virtually constant from fertilization and during development (356–366 mosmol), with a slight decrease near hatching (to 332 mosmol). Yolk and body fluids of larvae (338 mosmol) had osmoconcentrations similar to egg yolk values near hatching. Yolk osmoconcentration of unfertilized eggs remained unchanged during the first 12 h in sea water, with a slow increase thereafter. Fertilized eggs of bad quality cultures exhibited higher yolk osmoconcentrations than eggs of good quality. Cyclopterus eggs were found to develop normally and survive in 20–34%o salinity, larvae seemed to have the same salinity range.     

Embryonic development, larval growth and life cycle of Coenagrion puella (Odonata: Zygoptera) from an Austrian pond

SUMMARY. 1. Newly-laid eggs of Coenagrion puella (L.) from a pond near Herzogenburg (Lower Austria) were kept at constant water temperatures (range c .3.5°C to c .28°C)in the laboratory. Hatching success varied with temperature; no eggs hatched below 12°C and nearly all hatched at c .l6°C. Hatching time decreased with increasing temperature and the relationship between the two variables within the range 12–28 °C was well described by a power law. The length of the hatching period was less than 12 days. Hatching times estimated from the power-law equations and those obtained in the field experiments were similar. Therefore both the hatching time and the length of the hatching period in the field could be estimated from the laboratory data for the range 12–28°C.
2. The maximum number of instars from egg to imago was 11; the average body length increment (mm) per moult was proportionately constant at c .26% and Dyar's rule was applicable. The interval between moults decreased with increasing temperature up to the seventh instar and the relationship between the two variables within the range 12–28°C was well described by a power law. The moulting interval for instars 8–11 ranged from 23 to 48 days and was relatively independent of temperature. No moulting occurred at temperatures below 12°C.
3. Larval growth was logistic in the laboratory and variations in mean logistic growth rate (range 0–2.5% length day⁻¹) were related to mean temperature with no growth at temperatures <12°C. Larval growth rates in pond experiments were similar to those estimated from laboratory data, and therefore the regression equations obtained from the laboratory experiments are probably applicable to larval growth in the field.
4. Information on the life cycle of C. puella is briefly reviewed and it is concluded that C. puella from the pond near Herzogenburg has an univoltine life cycle.     

Reproductive biology of anadromous arctic char,Salvelinus alpinus (L.)? in the Cumberland Sound area of Baffin Island

The ovaries of anadromous arctic char, Salvelinus alpinus (L.), captured during 1973 from four high arctic rivers on Baffin Island started to increase in weight early in July and were at their heaviest in mid-September just before spawning. At this time, 40 cm (615 g) char from two rivers contained ovaries weighing 17.0 g (dry) which differed significantly from the 22.5 g gonads of comparable char from the other two areas. Gonadal development in male fish began in June and the diameter of testes at full maturity (3.0–4.0 cm) was similar regardless of river system. Fecundity of comparable fish varied significantly among the rivers with char 40 cm in length containing 1400–2400 eggs while the corresponding values for 60 cm (i.e. 2050 g) char ranged from 4000–5500. The diameter of both immature and mature eggs was similar regardless of system. Values for immature eggs averaged 0.64 mm in 40 cm fish and 1.60 mm in 60 cm specimens. Diameter of mature eggs, on the other hand, was considerably greater (3.2 and 4.3 mm, respectively). Maturity was first reached at age 10 (i.e. 35 cm) in both males and females and maturing fish of both sexes were not always restricted to fresh water. Redd construction occurred at a depth of one to at least 11 m at a temperature of 0.5–4.0° C. The percentage of eggs retained in the body cavity after spawning varied from 0.22–1.50 and the mortality rate of spawned eggs was extremely low.     

Larval development,growth and age determination in the sharpnose pufferfishCanthigaster valentini (Teleostei: Tetraodontidae)

The eggs, early larvae and juveniles of the sharpnose pufferfishCanthigaster valentini are described, based on material collected in Great Barrier Reef waters. Eggs were obtained in the field by divers and reared in the laboratory. The eggs are spherical, strongly adhesive, 0.68–0.72 mm in diameter, possess a dense cluster of small oil droplets, and hatch around sunset 3 to 5 days after fertilization. Newly hatched larvae have a small yolk sac, pectoral fin folds, 17 myomeres (6 pre-anal, 11 post-anal) and measure 1.30–1.40 mm in notochord (standard) length. The eggs ofC. valentini differ from those of other tetraodontids in being much smaller and having a longer incubation time. The larvae can be distinguished from other tetraodontid larvae by pigmentation, myomere count and size at hatching. Growth is most rapid during the first day of larval life. Age determinations (based on otolith microstructure) of field collected juveniles, both pelagic and newly settled, indicate a pelagic phase of between 64 and 113 days for this species. This estimate appears consistent with the extended pelagic juvenile stages observed in other tetraodontiform fishes and could indicate thatC. valentini can delay settlement for some time after becoming competent to settle at a minimum age of 64 days.     

Influence of egg size on embryos and larvae of Fundulus heteroclitus (L.)

Egg size for Fundulus heteroclitus (L.) populations is concordant with the distribution of the two F . heteroclitus subspecies, i.e. F. h. heteroclitus eggs are considerably larger than F. h. macrolepidotus eggs. The influence of egg size on survival of embryos during incubation and survival and growth of newly-hatched larvae was estimated for four populations representing both subspecies along the Atlantic coast of the United States and in Delaware Bay. Survival of embryos was determined for incubation periods of 14, 21 and 28 days. Greatest differences in survival were detected following the longest incubation period where less than 50 per cent of the smaller F. h. macrolepidotus eggs survived while little or no mortality was detected among the larger F. h. heteroclitus eggs . Influence of egg size on larval survival was also greatest among those larvae hatched after 28 days where F. h. macrolepidotus larvae survived without food, for an average of 6 days, while F. h. heteroclitus larvae survived 11–12 days. F. h. heteroclitus larvae were significantly larger at hatching than F. h. macrolepidotus larvae. Larval growth rates were the same (0.4 mm day⁻¹) in both subspecies. As a result, size differences at hatching were still maintained after 42 days of growth. The differences in egg size along with other morphological and reproductive characteristics of F. heteroclitus populations probably represent genetically based adaptations to environmental conditions, of which the length of the spawning season is one of the major components stimulating the coevolution of these traits.     

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.     

Relationships between maternal size, egg diameter, time of spawning season, temperature, and length at hatch of Atlantic silverside, Menidia menidia

Eggs were stripped from gravid Atlantic silversides collected on two occasions, once during the early part and once during the late part of the natural spawning season. Unfertilized egg diameter was not correlated with length of the female, nor was it significantly larger during the early part of the season. Eggs were fertilized and incubated in the laboratory. Larval length at hatch was measured every 24 h during the hatching period after embryos were incubated at 18 or 25° C. Lower incubation temperature caused a significantly greater length at hatch for the offspring of each of the 20 females studies. In most cases (17 out of 20 at 25° C, 10 out of 20 at 18° C), there was a significant decrease in length at hatch during the hatching period for a given female's eggs incubated at a given temperature. In the natural environment, larvae hatched early in the season under cooler temperatures could average 12% longer than those hatched later under warmer temperatures, and therefore may have a greater chance of survival. The results help to explain the observation that field-caught M. menidia that hatched early in the season are larger at any given age than those that hatched late in the season.     

Reproduction and growth of Craterocephalus marjoriae and C. stercusmuscarum (Pisces: Atherinidae) in south-eastern Queensland, Australia

SUMMARY. 1. The reproductive cycle and growth of Craterocephalus marjoriae and Craterocephalus stercusmuscarum (Atherinidae) were studied in Brisbane, south-eastern Queensland, over a 17-month period (1981–82).
2. Both species had a 5-month breeding season in spring and summer, with a breeding peak in spring (September-October). Multiple spawning occurred but life time fecundity was not determined.
3. Gonosomatic index values and mean fecundity per female were higher in Craterocephalus marjoriae than in C. stercusmuscarum. Fecundity increased with body length in both species according to the relationship, F=aL^b. Growth rates were similar and growth was adequately described by the von Bertalanffy equation. Both species grew rapidly during the first year and reached maturity the following season. Reproductive strategies are considered in relation to seasonal flooding in the streams inhabited.     

Larval development of the back keeled mullet Liza carinata

The sex ratio of the fish used in this study, was 1:1.5 females to males. Natural spawning of the keelback mullet, Liza carinata, in captivity was possible and occurred between December and February. The mean fertilized egg diameter of L. carinata was 0.8±.051 mm. Hatching took place after 36 h at 23°C. The mean total length of the just-hatched larvae was 2.0±0.179 mm. Larval developmental stages, growth, and morphological changes of L. carinata were described on the basis of a series of specimens (391 in total) reared from days 1 to 89 after hatching. Details of the larval developmental stages were drawn and photographed, with special reference being taken of morphological transformations. Larvae completed yolk absorption on the sixth day after hatching, and opened their mouths on day 4. Notochord flexion started on the sixteenth day at 5.0 mm total length. Transformation from larval to juvenile stage occurred between days 30 and 51 after hatching. The maximum size of larvae and the minimum size of juveniles which appeared during the transitional period were 19 and 9.9 mm TL, respectively. By day 51, all the larvae had changed into juveniles with a mean TL of 29.3±6.429 mm. The juveniles started to change into young adults with three anal spines by day 88 at a TL of 62 mm. This revised version was published online in September 2006 with corrections to the Cover Date.     

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.     

Early ontogeny of Ancherythroculter nigrocauda and effects of delayed first feeding on larvae

Development of embryos and larvae in Ancherythroculter nigrocauda Yih et Woo (1964) and effects of delayed first feeding on larvae were observed after artificial fertilization. The fertilized eggs were incubated at an average temperature of 26.5°C (range: 25.7–27) and the larvae reared at temperatures ranging from 21.8 to 28°C. First cleavage was at 50 min, epiboly began at 7 h 5 min, heartbeat reached 72 per min at 24 h 40 min and hatching occurred at 43 h 15 min after insemination. Mean total length of newly hatched larvae was 4.04 ± 0.03 mm (n = 15). A one‐chambered gas bladder was observed at 70 h 50 min, two chambers occurred at 15 days, and scales appeared approximately 30 days after hatching. Larvae began to feed exogenously at day 4 post‐hatch at an average temperature of 24°C. Food deprivation resulted in a progressive atrophy of skeletal muscle fibres, deterioration of the larval digestive system and cessation of organ differentiation. Larval growth under food deprivation was significantly affected by the time of first exogenous feeding. Starved larvae began to shrink, with negative growth from day 6 post‐hatch. The point of no return (PNR) was reached at day 11 after hatching. Mortality of starved larvae increased sharply from day 12 after hatching.     

光照强度与光周期对虎斑乌贼胚胎发育的影响

为探究光照对虎斑乌贼受精卵孵化的影响,确定其胚胎发育的最佳光照条件,本研究采用单因子试验方法,分析了不同光照强度(10、30、50、70、90 μmol·m^-2·s^-1)和光周期L∶D(24 h∶0 h、18 h∶6 h、12 h∶12 h、6 h∶18 h、0 h∶24 h)对虎斑乌贼胚胎发育的影响.结果表明: 不同光照强度对虎斑乌贼胚胎发育的孵化率、卵黄囊断裂率、培育周期、初孵幼体体质量与胴长均影响显著;而对孵化周期和幼体出膜7 d后存活率无显著影响.其中孵化率、培育周期、初孵幼体体质量与胴长随着光照强度的增强先增大后减小,而卵黄囊断裂率则逐渐增大.最适光照强度为30 μmol·m^-2·s^-1,此光照强度下孵化率为(90.0±4.1)%,卵黄囊断裂率为(7.3±1.5)%,培育周期为(25.50±0.35) d,孵化周期为(8.10±0.89) d,初孵幼体体质量为(0.213±0.011) g,胴长为(1.013±0.022) cm,出膜7 d后存活率为(97.1±4.0)%.不同光周期对虎斑乌贼胚胎发育的孵化率、培育周期、孵化周期均影响显著,而对卵黄囊断裂率、初孵幼体体质量、胴长和幼体出膜7 d后存活率无显著影响.其中孵化率和孵化周期随着光照时间的增加呈现先增大后减小的变化.最适光周期为LD(12 h12 h),此光周期下孵化率达(88.7±1.8)%,卵黄囊断裂率为(8.7±1.8)%,培育周期为(25.00±0.50) d,孵化周期为(7.00±3.20) d,初孵幼体体质量为(0.209±0.005) g,胴长为(0.998±0.026) cm,出膜7 d后存活率为(96.8±7.1)%.说明弱光照强度30 μmol·m^-2·s^-1和半日光照强度L∶D(12 h∶12 h)更有利于虎斑乌贼的胚胎孵化.在实际生产中,应避免阳光直射,采取适当的遮光措施.