Feeding resumption, morphological changes and mortality during starvation in Japanese flounder larvae

Japanese flounder Paralichthys olivaceus larvae established first feeding 3 days after hatching (DAH) at c. 17degreesC. Non-fed fish reached irreversible starvation at age 5 DAH. Non-fed fish showed similar feeding rate and feeding intensity as the fed fish when they were provided with prey before 5 DAH, after which the starved larvae did not feed even when prey became available. None of the six morphological measurements examined (total length, body height, eye height, head height, gut height and myotome height) showed significant differences between the non-fed and fed larvae until 5 DAH. Normal development continued only in the fed group, and the non-fed larvae showed reverse growth or body collapse after 5 DAH. Owing to the shrinkage and collapse at the top of head due to starvation, head height could be a sensitive indicator of starvation in Japanese flounder larvae. In the fed treatments, high mortality occurred from first feeding (3 DAH) to irreversible starvation (5 DAH), accounting for about two-thirds to three-quarters of the overall mortality (46-52%) throughout the experiments. This mortality was not prey density or larval density dependent. Mortality during the same period in the non-fed larvae accounted for about a third of the overall mortality (100%). (C) 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved.

Effects of temperature and delayed initial feeding on the survival and growth of Japanese flounder larvae

The effects of the timing of initial feeding (0, 1, 2 3 and 4 days after yolk exhaustion) and temperature (15, 18 and 21degrees C) on the point-of-no-return (PNR), survival and growth of laboratory-reared Japanese flounder Paralichthys olivaceus larvae were studied under controlled conditions. The larvae reached PNR on 7(.)7, 5(.)2 and 4(.)2 days-post-hatching (dph) at 15, 18 and 2 V C, respectively. At each temperature, larval growth did not differ significantly among the delayed initial feedings 1 day before PNR but decreased significantly in larvae first fed after that. In the treatments where initial feeding was equally delayed, larvae grew significantly faster at 18 and 21degrees C than at 15degrees C. The larvae survived apparently better at 15 and 18degrees C than at 21degrees C when initial feeding was equally delayed. At each temperature, survival of the larvae first fed before PNR did not differ noticeably, while delayed initial feeding after that apparently reduced their survival. These results indicated that there existed a negatively temperature-dependent PNR in the Japanese flounder larvae. Survival and growth of the larvae strongly depended on temperature as well as the timing of initial feeding. High temperature accelerated the yolk exhaustion and growth of the larvae and thus reduced their starvation tolerance and survival. To avoid potential starvation mortality and obtain good growth, the Japanese flounder larvae must establish successful initial feeding within 2 days after yolk exhaustion at 15degrees C and within 1 day at both 18 and 21degrees C. (C) 2005 The Fisheries Society of the British Isles.

Effects of delayed first feeding on growth and survival of rock bream Oplegnathus fasciatus larvae

The effects of the timing of first feeding (0, 1 and 2 days after yolk exhaustion) and starvation on the point-of-no-return (PNR), survival and growth of laboratory-reared rock bream larvae were studied under controlled conditions. Larvae began to feed exogenously at 3 days after hatching (dah) and reached PNR on 54 h after yolk exhaustion at 22 +/- 1.5 degrees C. Larvae growth was significantly affected by the time of first exogenous feeding. The growth of 0 day delayed first feeding larvae was obviously faster than those of the other delayed first feeding larvae (P<0.05) whether at 7 dab (SL=3.40 mm, SGR=5.7, CV=4.0) or at 15 dah (SL=4.85 mm, SGR=6.1, CV=8.2) with a more uniform size distribution. Survival of 0 day delayed first feeding larvae and I day delayed first feeding larvae was 13% and 8% at the end of experiment, respectively, while no larvae survived up to 7 dah for 2 days delayed first feeding larvae and unfed larvae. Food resulted in a progressive deterioration of the larval digestive system and atrophy of skeletal muscle fibre. The ratios of head length to SL (standard length), body height to SL and eye diameter to SL were the most sensitive morphometric indices to detect the effects of fasting on larval condition. Present results showed that the combination of morphological and morphometric variables could be used to evaluate the nutritional condition of rock bream larvae. In order to avoid the potential mortality and gain better development, survival and growth in industrial production, the rock bream larvae must establish successful first feeding within 2 days after yolk exhaustion. (C) 2008 Elsevier B.V. All rights reserved.

Feeding behaviour of Japanese flounder larvae under laboratory conditions

Tank-reared Japanese flounder larvae, Paralichthys olivaceus, had a major feeding peak in the morning and a secondary peak in the afternoon throughout the larval development, with light being the primary factor regulating their feeding activity. The larvae consumed rotifers in preference to Artemia for up to 10 days, after which the food preference shifted to Artemia. Feeding rates of the larvae prior to 10 days post-batch depended on prey density, but in the old larvae, feeding rates were independent of prey density. Maximum feeding rate occurred at 19 degrees C. The occurrence of the attack posture, after its onset at first feeding (2 days post-hatch), increased up to 25 days, began to decrease when the larvae prepared to settle down, then disappeared after settlement. The occurrence frequency of the attack posture was positively related to fish density, but inversely related to starvation duration, and occurred most frequently at 19 degrees C. This posture depended on prey density in larvae prior to 10 days post-hatch, but became independent of prey density as the larvae developed. It was obvious that, for flounder larvae, attack posture was a behavioural character closely related to feeding and subject to larval development and environmental factors. (C) 2000 The Fisheries Society of the British Isles.

Cannibalism in Japanese flounder juveniles, Paralichthys olivaceus, reared under controlled conditions

Laboratory experiments were conducted to determine the effects of sand substratum, light, starvation, fish density and size variation on cannibalism among Japanese flounder juveniles, Paralichthys olivaceus. Cannibalistic behavior (biting and swallowing) increased significantly with starvation except in darkness, where juveniles could not find and attack their prey. Cannibalism occurred more frequently in heterogeneous than in the homogeneous size groups. Cannibalism was more frequent in light than in darkness at each starvation level. With sufficient food present, sand had no significant effect on cannibalism among homogeneous size juveniles, but played an important role in discouraging predation among members of the heterogeneous size groups. With sufficient food present, the rate of cannibalism was generally low and there were no significant differences in cannibalism among fish density levels of the homogeneous juveniles, With starvation, the cannibalism rate was significantly higher in high density groups than in the lower ones. Our results indicate that size variation, starvation and Light are the major factors affecting cannibalism in flounder juveniles, while sand and fish density only have a limited effect on cannibalism, depending on the nature of other factors. (C) 2000 Elsevier Science B.V. All rights reserved.

Waterborne exposure to PFOS causes disruption of the hypothalamus-pituitary-thyroid axis in zebrafish larvae

Thyroid hormones (THs) play an important role in the normal development and physiological functions in fish. Environmental chemicals may adversely affect thyroid function by disturbing gene transcription. Perfluorooctane sulfonate (PFOS), a persistent compound, is widely distributed in the aquatic environment and wildlife. In the present study, we investigated whether PFOS could disrupt the hypothalamic-pituitary-thyroid (HPT) axis. Zebrafish embryos were exposed to various concentrations of PFOS (0, 100, 200 and 400 mu g L-1) and gene expression patterns were examined 15 d post-fertilization. The expression of several genes in the HIPT system, i.e., corticotropin-releasing factor (CRF), thyroid-stimulating hormone (TSH), sodium/iodide symporter (NIS), thyroglobulin (TG), thyroid peroxidase (TPO), transthyretin (TTR), ioclothyronine deiodinases (Dio1 and Dio2) and thyroid receptor (TR alpha and TR beta), was quantitatively measured using real-time PCR. The gene expression levels of CRF and TSH were significantly up-regulated and down-regulated, respectively, upon exposure to 200 and 400 mu g L-1 PFOS. A significant increase in NIS and Diol gene expression was observed at 200 mu g L-1 PFOS exposure, while TG gene expression was down-regulated at 200 and 400 mu g L-1 PFOS exposure. TTR gene expression was down-regulated in a concentration-dependent manner. Up-regulation and down-regulation of TR alpha and TR beta gene expression, respectively, was observed upon exposure to PFOS. The whole body thyroxine (T-4) content remained unchanged, whereas triiodothyronine (T-3) levels were significantly increased, which could directly reflect disrupted thyroid hormone status after PFOS exposure. The overall results indicated that PFOS exposure could alter gene expression in the HPT axis and that mechanisms of disruption of thyroid status by PFOS could occur at several steps in the synthesis, regulation, and action of thyroid hormones. (C) 2009 Elsevier Ltd. All rights reserved.

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 degrees C (range: 25.7-27) and the larvae reared at temperatures ranging from 21.8 to 28 degrees 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 degrees 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.

Growth of juvenile Chinese sturgeon Acipenser sinensis fed live and formulated diets

Triplicate groups of 3.8-g juvenile Chinese sturgeon Acipenser sinensis were reared for 8 weeks in indoor flow-through systems on one of four diets: a natural diet consisting solely of live tubificid worms, a semimoist practical diet, a dry practical diet, and a purified diet. The formulated diets were prepared in the laboratory and had protein contents of 47-50%. Except for the group fed the purified diet, fish showed high survival (94-96%) and growth (final weight, 41-45 g). Survival and specific growth rate did not differ significantly between groups fed the natural, semimoist, and dry practical diets, but were significantly (P < 0.05) lower in fish fed the purified diet. Proximate analysis showed that fish fed purified diet had lower protein and lipid levels but a higher moisture content than fish fed other diets. Our results demonstrated that growth and survival of cultured juvenile Chinese sturgeon fed practical diets were comparable with those fed live tubificid worms. However, Chinese sturgeon fed a purified diet showed inferior growth and survival.

CO2浓度升高对三种树木叶片化学和舞毒蛾幼虫取食及生长的影响

探讨全球气候变化的生物学和生态学效应是当今生态学中的热点，研究大气CO2浓度升高对植物-昆虫相互作用关系的影响具有重要的理论和实践意义。本文使用开顶式气室（Open-top chamber，OTC）在野外条件下研究了CO2浓度升高对三种树木（小青杨、白桦和蒙古栎）叶片化学成分含量的影响，以及树木叶片品质变化对一种广食性森林昆虫（舞毒蛾）幼虫取食、生长发育和取食偏嗜性的影响。得出如下结果：（1）CO2浓度升高对3个受试树种叶片中的营养成分及次生代谢物含量均有显著影响，总体表现为氮含量降低，而碳氮比、非结构性碳水化合物、总酚和缩合丹宁含量增加。叶片中的化学成分含量可随时间发生显著变化，不同树种、甚至同一树种不同冠层高度的叶片对CO2浓度升高的响应强度也是不同的。叶片的干物质含量和比叶重对CO2浓度升高的响应不显著。（2）室内非选择性取食实验、室内选择性取食实验以及上树取食饲养方式下的多龄期取食实验，均发现高浓度CO2处理组内舞毒蛾幼虫的生长发育受到显著抑制。但对四龄舞毒蛾幼虫所进行的短期生物测定并未发现不同CO2浓度处理下幼虫的生长发育速率、对食物的取食率和转化率等昆虫营养指标存在显著差异。（3）叶片品质的降低是导致舞毒蛾幼虫生长发育受抑制的主要原因。但是总体上，CO2浓度升高导致的叶片品质变化并未显著影响幼虫的取食率和取食量。（4）舞毒蛾幼虫对不同叶片种类表现出清晰的取食选择性，这种选择性在其幼龄期就可表现出来。幼虫对小青杨上层叶片有最显著的偏嗜性，对蒙古栎下层叶片有最明显的拒食性。但是CO2浓度升高导致的叶片品质变化对舞毒蛾幼虫的取食选择性和寄主偏嗜行为并未产生显著影响。（5）检测出高浓度CO2处理组内舞毒蛾幼虫虫粪中含有浓度更高的植物次生代谢物质（总酚和缩合单宁），这很可能是昆虫整体生长发育受抑制的重要原因之一。

Size and time of day affect the response of postlarvae and early juvenile grooved tiger prawns Penaeus semisulcatus De Haan (Decapoda:Penaeidae) to natural and artificial seagrass in the laboratory

Juvenile tiger prawns (Penaeus semisulcatus De Haan and P. esculentus Haswell) show a strong association with vegetated habitats and are rarely caught on non-vegetated areas. This pattern of distribution may be caused by postlarvae selecting vegetation when they settle, or to differences in post-settlement mortality in different habitats. In this study, we examined whether the postlarvae and early juvenile stages of P. semisulcatus would distinguish between seagrass (Zostera capricorni Aschers) without epiphytes, artificial seagrass and bare substratum in the laboratory. The responses of prawns reared from the egg to different stages of postlarval and juvenile development were tested to determine whether, and when, each size class showed a response to a particular habitat. Five size classes of postlarvae (average carapace lengths [CL] of 1.2, 1.4, 1.6, 1.7 and 2.0 mm) were offered a choice between Z. capricorni and bare sand. Small size classes of postlarvae either did not respond to Z. capricorni (1.2 and 1.6 mm CL), or were more abundant on bare substratum than Z. capricorni. In contrast, the largest size classes of postlarvae (1.7 and 2.0 mm CL) were more abundant on Z. capricorni during the day but not at night. The behaviour of postlarvae changed markedly at a size of 1.7 mm CL (22 days from the first nauplius): smaller postlarvae frequently swam in the water column; 1.7 and 2.0 mm CL postlarvae spent much more. time resting on the substrate and perched on seagrass leaves. This size at which postlarvae first respond to seagrass during the day, and show mainly benthic behaviour, is similar to the size at which they are found on shallow seagrass beds in northern Australia. Large postlarvae (2.7 mm CL) and juveniles (4.1 mm CL) both were more abundant on artificial seagrass than bare sand during the day but not at night, indicating that they respond to structured habitats. When large postlarvae (2.4 mm CL) and juveniles (3.5 mm CL) were offered a choice between Z. capricorni without epiphytes and artificial seagrass, they were more abundant on the Z. capricorni, which suggests that chemical cues from seagrass may explain some of the responses of P. semisulcatus to seagrass. (C) 1997 Elsevier Science B.V.

Effect of stocking density on growth, settlement and survival of clam larvae, Meretrix meretrix

To determine the optimal larval density for hatchery culture of the clam Meretrix meretrix, experiments with stocking densities of 5, 10, 20, 40 and 60 larvae ml(-1) were designed, which included the developmental stages from D-veliger to 8 days postsettlement. Shell length, settlement time and survival rate of the larvae were recorded. Results showed that, at each sampling time, larvae reared at the highest density had the smallest mean size, whereas larvae reared at the lowest density had the largest mean size. Statistical differences in mean shell length at different stocking densities appeared from day 2, and greater differences occurred with increased culture time. Specific growth rate (SGR) in the rapid growing stage (day 0-3) was negatively correlated with density; however, no correlation was found between SGR and density in the slow growing stage (days 3-7). Settlement time was prolonged and shell length of settled larvae decreased as density increased. However, larval survival rate (74.8-79.1%) was independent of stocking density. Results showed that a high stocking density, in the designated range, is feasible for larval culture of the clam M. meretrix. However, for large-scale culture, in the interest of costs and safety, a stocking density of 10-20 larvae ml(-1) is recommended. (c) 2006 Elsevier B.V. All rights reserved.

LABORATORY HYBRIDIZATION BETWEEN CRASSOSTREA ARIAKENSIS AND C. SIKAMEA

TO understand possible reproductive interaction between Crassostrea ariakensis (Fujita, 1913) and C. sikamea (Amemiya, 1928), which coexist ill estuaries of China and Japan, we conducted 2 X 2 factorial crosses between the two species. Asymmetry in fertilization success was observed where C. sikamea eggs can be fertilized be C. ariakensis the receprocal cross resulted in no fertilization. Fertilization Success ill C.sikamea female X C. ariakemvis male (SA) crosses was lower than that in the two intraspecific crosses and produced larvae that had similar growth the rate as their maternal species during the first nine days because of maternal effects. After that, genome incompatibility casted negative effects on the growth and survival of the hybrid larvae. Most hybrid larvae died during metamorphosis. but a small number of spat survived. Genetic analysis revealed that the survived SA spat contained DNA from both species and were the hybried. This study demonstrates that hybridization between C. ariakensis and C. sikamea is possible in one direction.

Identification of factors affecting the growth and survival of the settling Japanese flounder larvae, Paralichthys olivaceus

A series of experiments were conducted to identify the factors that affected the growth and survival of the settling flounder larvae Paralichthys olivaceus. Settling larvae 24 days after hatching (DAH) were reared in 10-l experimental tanks up to 40 DAH, and two of the following factors were changed as controlled factors in each experiment: light regime (24L:0D or 12L:12D), prey density (1500, 3000, or 5000 Artemia l(-1)), shelter (sand or no sand) and stocking density (5, 10, or 15 fish l(-1)). Early settling larvae (24-35 DAH) experienced little mortality (less than 10% of the overall mortality) that was not significantly affected by above factors. In contrast, late settling larvae (36-40 DAH) suffered high cannibalistic mortality which was significantly influenced by each of the above factors. Larvae experienced significantly lower mortality at 10 fish l(-1) level than at other densities. Larvae at 15 fish l(-1) level had higher mortality than at 5 fish l(-1) when all other factors were identical. Larvae at 3000 and 5000 Artemia l(-1) treatments survived significantly better than at 1500 Artemia l(-1), but no significant differences in larval mortality were found between the two higher densities. Larvae suffered higher mortality at low prey density or at the absence of sand when they were exposed to longer photoperiod. Low stocking density significantly improved the growth of the settling larvae. The average daily instantaneous growth rate (G) at 5 and 15 fish l(-1) treatments were 0.050 and 0.034, with the coefficient of variation (CV) in final length at 16.4 and 23.5, respectively. Daily instantaneous growth rate increased significantly from 0.033 in the 1500 Artemia l(-1) to 0.041 and 0.045 in the 3000 and 5000 Artennia l(-1), respectively, but no significant difference in larval growth existed between the two higher prey densities. These findings suggested that the optimal prey density for growth and survival of the settling flounder larvae at a stocking density of 5 - 15 fish l(-1) was around 3000 Artemia l(-1) . Larvae that were exposed to 24L showed 20% increase in growth ( G = 0.046, CV = 18.7) than those exposed to 12L ( G = 0.037, CV = 20.5). Longer exposure to light significantly improved larval growth, provided sufficient food was available. Sand substrate did not show significant effects on larval growth, possibly because the larvae spent most of the time swimming or feeding in the water column during this stage. (C) 2003 Elsevier Science B.V. All rights reserved.

Effects of rearing temperature and density on growth, survival and development of sea cucumber larvae, Apostichopus japonicus (Selenka)

In laboratory conditions, effects of rearing temperature and stocking density were examined on hatching of fertilized egg and growth of auricularia larvae of Apostichopus japonicus respectively. Data series like larval length and density, metamorphic time, and survival rate of the larvae were recorded. Statistics showed that for A. japonicus, survival rate (from fertilized egg to late auricularia) decreased significantly with the increasing rearing temperature (P < 0.05). At different temperatures SGR was statistically significant as well (P < 0.05) from day 1, and maximal SGR was found on day 9 at 24A degrees C (159.26 +/- 3.28). This study clearly indicated that at low temperature (< 24A degrees C), metamorphic rate was remarkably higher than at higher temperature (> 26A degrees C). Hatching rate was significantly different between 0.2-5 ind./ml groups and 20-50 ind./ml groups. Rearing larvae at the higher density had the smaller maximal-length, whereas needed longer time to complete metamorphosis. This study suggested that 21A degrees C and 0.4 ind./ml can be used as the most suitable rearing temperature and stocking density for large -scale artificial breeding of A. japonicus's larvae.

Some Key Technics of Drop Tower Experiment Device of National Microgravity Laboratory (China) (NMLC)

Drop tower is an important ground based facility for microgravity science experiment. The technical performances of the drop tower NMLC are advanced compared with similar facilities in the US, Germany and Japan. The main components such as drop capsule, deceleration devices, release mechanism present its advantages and creativities.