20 resultados para Metamorphosis
em Chinese Academy of Sciences Institutional Repositories Grid Portal
Resumo:
Spontaneous formation of InAs quantum wires in InAlAs on InP(001) via sequential chain-like coalescence of quantum dots along [1 (1) over bar 0] is realized. Theoretical calculations based on the energetics of interacting steps provide a qualitative explanation for the experimental results. Sequential coalescence of initially isolated dots reduces the total free energy strikingly. Thus the wire-like structure is energetically favorable. (C) 1998 Elsevier Science B.V.
Resumo:
Both MI and MII triploids were successfully produced by heat shock in Chinese shrimp Fenneropenaeus chinensis. The inducing conditions for MI and MII triploids were optimized. The highest inducing rate obtained for MI triploids reached more than 90%, and that for MII triploids reached nearly 100% at the nauplius stage as evaluated using flow cytometry. Comparisons of survival rates at larval stages between triploids and diploids or diploids experiencing treatment and diploids without treatment were performed. At larval stage from nauplii to postlarvae, heat shocks lowered survival at larval stages even if the ploidy was not changed. Ploidy did not affect shrimp larvae survival, and no significant difference was found in the survival of shrimp larvae between MI and MII triploids. Highly significant differences were observed in the morphology of triploids and diploids, and no apparent difference was found in the morphology of MI and MII triploids at the grow-out stages. Discriminating formulae for triploid and diploid shrimp at grow-out stage were developed and could be used to distinguish triploids from diploids based on morphological parameters. MI and MII triploids of shrimp have the potential to be used in aquaculture.
Resumo:
Catecholamines regulate several physiological processes in mollusks. Many pharmacological experiments have been conducted to determine the effects of adrenergic agonist and antagonist of catecholamine receptors on Meretrix meretrix metamorphosis. Results showed that adrenaline (AD) and noradrenaline (NA) had substantial effects (p < 0.05) on larval metamorphosis at concentrations ranging from 10 mu M to 100 mu M. 10 mu M beta-adrenergic receptor (AR) agonist isoproterenol showed the same inducement effect as that of NA and AD on metamorphosis, whereas the alpha-AR agonist phenylephrine had no significant effect at concentrations between 0.1 mu M and 100 mu M concentrations (p > 0.05). Furthermore, I mu M beta-AR antagonist propanolol, but not alpha-AR antagonist prazosin, depressed the larval metamorphosis induced by NA or AD. By immunocytochemistry, two cell bodies of beta-adrenergic-like receptor, C/A1, C/A2, were observed in the cerebral/apical ganglion of competent larvae. In addition, there were other immunoreactive dots near C/A1 and C/A2. The results of pharmacology and immunocytochemistry suggests that beta-adrenergic-like receptor located in the larval CNS, might play a considerable role in the larval metamorphosis of M meretrix by AD or NA. (c) 2006 Elsevier B.V. All rights reserved.
Resumo:
In order to assess the toxicity of heavy metals on the early development of Meretrix meretrix, the effects of mercury (Hg), cadmium (Cd) and lead (Pb) on embryogenesis, survival, growth and metamorphosis of larvae were investigated. The EC50 for embryogenesis was 5.4 mu g l(-1) for Hg, 1014 mu g l(-1) for Cd and 297 mu g l(-1) for Pb, respectively. The 96 h LC50 for D-shaped larvae was 14.0 mu g l(-1) for Hg, 68 mu g l(-1) for Cd and 353 mu g l(-1) for Pb, respectively. Growth was significantly retarded at 18.5 mu g l(-1) (0.1 mu M) for Hg, 104 mu g l(-1) (1 mu M) for Cd and 197 mu g l(-1) (1 mu M) for Pb, respectively. The EC50 for metamorphosis, similar to 48 h LC50, was higher than 96 h LC50. Our results indicate that the early development of M. meretrix is highly sensitive to heavy metals and can be used as a test organism for ecotoxicology bioassays in temperate and subtropical regions.
Resumo:
The impact of starvation on larvae of Ivory shell Babylonia formosae habei was studied in a laboratory experiment. Newly hatched veligers showed considerable tolerance to starvation due to their endogenous yolk material, and time to the point-of-no-return (PNR; the threshold point during starvation after which larvae can longer metamorphose even if food is provided) was calculated to be 104.5 h. However, starvation still affected larval growth, survival, and metamorphosis. Mean shell length of larvae increased 49.77 mum day(-1) for nonstarved, but only 11.13 mum day (-1) for larvae starved for 108 h. After larvae began feeding, their growth rates rapidly recovered to the level of the nonstarved following short periods of starvation (less than 48 h), but were inhibited and unable to ever reach the level of the nonstarved when being starved beyond 48 h. Percent metamorphosis was 53.75% for the nonstarved, but all larvae died before 10 days for those starved for 108 h. Starvation not only affected larval time to reach metamorphosis, but also caused the delay in the time to metamorphosis. For the nonstarved, larvae took only 11.5 days to reach spontaneous metamorphosis, but they took 20 days to reach spontaneous metamorphosis when starved for 96 h, and this duration of delayed metamorphosis reached 8.5 days. Furthermore, the importance of yolk material for maintaining larval survival of B. formosae habei during starvation periods is also discussed. (C) 2004 Elsevier B.V. All rights reserved.
Resumo:
A series of experiments was conducted to evaluate the effects of diet, stocking density, and environmental factors on growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum larvae. These experiments examined the following factors: diet (Isochrysts spp., Chlorella spp., and a mixture of Isochrysis spp. and Chlorella spp. [ 1: 1 w/w]), stocking density (5, 10, 15, and 20 larvae ml(-1)), light intensity (un-shaded, partially shaded, and fully shaded), water filtration (unfiltered and sand-filtered), water exchange (50% and 100% once every other day, 25%, 50%, and 100% once daily; 50% and 100% twice daily), and the use of substrate (with and without sand as the substrate). Results indicated that Chlorella spp. could replace 50% of Isochrysis spp. as a food source for the Manila clam larvae without affecting growth, survival, and metamorphosis. Larval growth decreased significantly with increasing stocking density. A density of 5-10 larvae ml(-1) appeared to be optimal for normal growth of Manila clam larvae. Neither diet nor stocking density used in the study had a significant effect on larval survival. Under partially shaded (light intensity = 1000-5000 lx) and fully shaded (light intensity <500 lx) conditions, larval growth was significantly faster than under direct sunlight (un-shaded). A water exchange rate of 50% twice daily provided optimum larval growth. Larvae grew significantly faster in the unfiltered water than in the sand-filtered water. Using sand as the substrate in the culture system significantly depressed the metamorphosis rate. The type and particle size of sand used as the substrate did not significantly affect growth and metamorphosis rates of the larvae. (C) 2005 Published by Elsevier B.V.
Resumo:
The early life-history of Chinese rock carp Procypris rabaudi was investigated during a 56-day rearing period: 318 artificially propagated P. rabaudi larvae were reared throughout metamorphosis in a small-scale recirculation system (345 L water volume, 10 x 18 L rearing tanks, 150 L storage and filter compartment with bioballs, 20-30 larvae L-1) at the Institute of Hydrobiology, Wuhan, Hubei Province, China. The newly hatched larvae had an initial total length of 8.93 +/- 0.35 mm SD (n = 10) at 3 days post-hatch and reached an average total length of 33.29 mm (+/- 1.88 mm SD, n = 10) 56 days after hatching. Length increment averaged 0.45 mm day(-1), resulting in a mean growth of 24.4 mm within the 56-day period. High mortality rates of up to 92% derived from an introduced fungus infection and subsequent treatment stress with malachite green. Our results indicate that Chinese rock carp can be raised successfully from artificially fertilized eggs. We therefore assume this species to be a candidate for commercial aquaculture.
Resumo:
从空间、时间、食物3个方面研究了若尔盖湿地3种两栖类的种间竞争,运用生态位理论探讨了3种两栖类利用环境资源的能力以及它们之间的共存模式,研究了3种两栖类年周期食性,并考察了畜牧业对3种两栖类食性及食物竞争格局的影响;此外,还通过实验室研究对2种两栖类幼体的种间竞争策略进行了考察。主要结果如下: 1、两栖类的空间资源利用状况:在3种两栖类成体生态位宽度的比较中,岷山蟾蜍(Bufo minshanicus)成体在牧场性质(0.41)、牛粪数量(0.42)、植被盖度(0.20)、地表温度(0.50)、地表湿度(0.51) 5个维度上的生态位宽度最窄;而倭蛙(Nanorana pleskei)成体在牛粪数量(0.81)、植被高度(0.63)、植被盖度(0.47)、小水体距离(0.68) 4个维度上的生态位宽度最宽。在3种两栖类亚成体生态位宽度的比较中,岷山蟾蜍亚成体在牧场性质(0.66)、牛粪数量(0.58)、植被高度(0.64)、小水体距离(0.51)、地表湿度(0.79) 5个维度的上生态位宽度最宽;倭蛙亚成体在牧场性质(0.39)、牛粪数量(0.30)、地表温度(0.18)、地表湿度(0.33) 4个维度上的生态位宽度最窄。高原林蛙(Rana kukunoris)在地表温度(成体:0.62;亚成体:0.56)、地表湿度(成体:0.84;亚成体:0.60)两个维度上具有较大的生态位宽度值,而在小水体距离维度上(成体:0.27;亚成体:0.14)的生态位宽度值则很小。比较3种无尾两栖类在不同生长阶段(成体、亚成体)的生态位宽度,发现高原林蛙和倭蛙的亚成体对栖息环境的要求更高。3种两栖类空间资源利用的相似程度很高,高原林蛙与倭蛙之间的生态重叠度(0.87)较之它与岷山蟾蜍(0.81)的生态位重叠度更大。 2、两栖类的日活动节律:高原林蛙成体、亚成体、岷山蟾蜍亚成体活动的最低气温为0℃、2℃、8℃;岷山蟾蜍和高原林蛙亚成体出现的数量与气温成极显著的正相关(r=0.797, p<0.001;r=0.794, p<0.001),高原林蛙成体出现的数量与气温有一定相关性(r=0.456, p<0.05);晴天时两栖类的活动性明显高于阴天(p<0.001);多云转晴天气,高原林蛙和岷山蟾蜍亚成体出现两次日活动高峰,分别为中午12:30左右和下午15:30~16:30之间;多云天气,高原林蛙和岷山蟾蜍亚成体出现两次日活动高峰,分别为9:30~10:30之间和15:30~16:30之间。 3、两栖类的食物资源利用状况:春、秋两季,高原林蛙最主要的食物是蜉金龟科(Aphodiidae)昆虫,相对重要性指数(IRI)最高(春季:35.28%,秋季:28.57%),其次为昆虫的幼虫,以及双翅目的毛蚊科(Bibionidae)、蝇科(Muscidae)、丽蝇科(Calliphoridae)昆虫,秋季,蝗虫是高原林蛙食物组成中的重要部分;岷山蟾蜍最主要的食物是蚂蚁(IRI,春季:85.54%,秋季:49.70%),其次为蜉金龟科、象甲科(Curculionidae)、步甲科(Carabidae)、粪金龟科(Geotrupidae) 等鞘翅目昆虫;倭蛙春季的最主要食物也是蜉金龟科昆虫(IRI,春季:13.41%),其次为蚂蚁、毛蚊科昆虫、昆虫的幼虫以及狼蛛科(Lycosidae)。3种两栖类中,倭蛙的食性生态位宽度相对较宽(0.43),而岷山蟾蜍(0.09)和高原林蛙(0.22)的生态位宽度较窄,与春季相比,两栖类在秋季的食谱更宽。以利用食物种类为标准,春季高原林蛙与倭蛙的生态位重叠度(0.40)比它与岷山蟾蜍的生态位重叠度(0.33)更大。 4、畜牧业对两栖类食性及食物竞争格局的影响:以藏牦牛粪为食物或寄居场所的昆虫,如蜉金龟科、粪金龟科、毛蚊科、蝇科、丽蝇科昆虫和某些昆虫幼虫,是3种两栖类食物谱中最主要的组成部分,蜉金龟科昆虫在高原林蛙食谱中的比例更高,高原林蛙可能从畜牧业发展中获得更多的好处,使之在食物竞争方面处于优势地位。与无放牧样地相比,在有放牧样地的中,两栖类食谱中的蜉金龟科昆虫数量更多(有放牧:31.94%;无放牧:21.32%)、出现频率更高(有放牧:76.38%;无放牧:44%)。然而在不同样地上(有放牧/无放牧),两栖类的食物组成无显著性差异(P=0.188),两栖类的数量(P=0.075)、肥满度(P=0.537)均没有显著差别。 5、两栖类幼体的竞争策略:实验室条件下,通过活动性水平,变态时的体重、增长率和完成变态所需时间考察自然条件下常同水塘分布的中华蟾蜍(Bufo gargarizans)和高原林蛙蝌蚪的竞争策略。结果表明:中华蟾蜍蝌蚪在不同食物资源条件下,所选择的生存策略可能不同,即食物资源充足时,增加活动性获取更多食物,食物资源有限时,降低活动性且提前完成变态;与中华蟾蜍蝌蚪相比,在食物资源有限时高原林蛙蝌蚪获取食物能力可能更强。 This paper presented the study of competition of three amphibians (Rana kukunoris, Nanorana pleskei, Bufo minshanicus) based on spatial, temporal and dietary scales in Zoige wetland. We measured coexistence patterns of three amphibians and analyzed their ability of exploiting resource. Effects of grazing on the diet composition and diet competition of amphibians were analyzed by their diet composition during spring and autumn. Furthermore, we examined the competitive ability of larval common frogs (Rana kukunoris)and common toads(Bufo gargarizans) in a laboratory experiment, and analyzed their competitive strategies respectively. The results were as follows: 1 .The status of using spatial resource Niche breadths of B. minshanicus adults on 5 dimensional axes including character of pasture(0.41), number of yaks dung(0.42), vegetation coverage(0.20), temperature (0.50)and humidity(0.51) of ground surface were narrower than adults of R. kukunoris and N. pleskei. Niche breadths of B. minshanicus subadults were broader than R.kukunoris subadults and N.pleskei subadults on 5 dimensional axes including character of pasture (0.66), number of yaks dung (0.58), vegetation height (0.64), distance to small waterbodies (0.51), humidity of ground surface (0.79). Niche breadths of N. pleskei subadults were the narrowest in three anurans subadults on 4 dimensional axes including character of pasture (0.39), number of yaks dung (0.30), temperature (0.18) and humidity (0.33) of ground surface, niche breadths of N. pleskei adults were the broadest in three anurans adults on 4 dimensional axes including number of yaks dung (0.81), vegetation height (0.63) and coverage(0.47), distance to small waterbodies(0.68).Comparatively, niche breadths of R. kukunoris were broader on the two microclimate factors including temperature(adults:0.62;subadults:0.56) and humidity (adults:0.84;subadults:0.60)of ground surface, but was narrow on distance to small waterbodies(adults:0.27;subadults:0.14). Strategies for using habitat resource of adults and subadults of the three species anuran were different. Generally, subadults of R. kukunoris and N. pleskei needs better habitat condition. It was quite similar that three anurans exploited spatial resource, Niche overlap between R. kukunoris and N. pleskei (0.87) was greater than that between R. kukunoris and B.minshanicus(0.81). 2.Daily activity rhythm R. kukunoris audlts were active when air temperatures were as low as 0℃, R. kukunoris subadults were active at 2℃, B.minshanicus subaudlts were active at 8℃. Positive correlation was found between activities of amphibians and air temperature, Subadults of R.kukunoris, (r=0.797, p<0.001), Subadults,of,B.minshanicus, (r=0.794, p<0.001), andbadults,of,R.kukunoris(r=0.456, p<0.05).Amphibians were more active during sunny days than cloudy days. In cloudy turning into sunny, R. kukunoris and B.minshanicus subadults had two active peak: at noon about 12:30 and 15:30~16:30 pm; in cloudy, R. kukunoris and B.minshanicus subadult had two active peak too : 9:30~10:30am,15:30~16:30pm. 3.Diet analysis Aphodiidae was the most commonly consumed food item by R. kukunoris based on index of relative importance (IRI) during spring (35.28%) and autumn (28.57%) in Zogie wetland. Besides Aphodiidae, larval insect, dipterans such as Bibionidae, Muscidae, Calliphoridae also were important food item for R. kukunoris, in autumn, locust was one of important food item for R. kukunoris. The most important food item for B.minshanicus during spring (IRI:85.54%) and autumn (IRI:49.70%) was ants, following, was coleopterans, such as Aphodiidae, dung beetle. Aphodiidae (IRI:13.41%) were the most important consumed food item by N. pleskei during spring too, following, was ants and Bibionidae. Dietary breadth of N. pleskei (0.43) were greater than R. kukunoris (0.22) and B. minshanicus (0.09). As a whole, Dietary breadth of amphibians during aurumn were greater than spring. Based on prey item, dietary overlap between R. kukunoris and N. pleskei (0.40) was greater than that between R. kukunoris and B.minshanicus (0.33) during spring. 4.Effects of grazing on the diet composition and diet competition of amphibians Amphibians are an important part of the pasture ecosystems as prey and predator. In Zogie wetland, major diet of amphibians was closely associated with dung of yaks, for example, Aphodiidae, Bibionidae, Muscidae, dung beetle. Dung of yaks was major diet and habitat of these insects. Proportion of Aphodiidae was higher in diet composition of R. kukunoris than N. pleskei and B.minshanicus, with development of pasturage, R. kukunoris may have a diet competitive advantage over N. pleskei and B.minshanicus. Number of Aphodiidae in diet composition of amphibians was higher in samples with grazing (31.94%) than in those without grazing (21.32%). Occurrence Frequency of Aphodiidae in diet composition of amphibians was higher in samples with grazing (76.38%) than in those without grazing (44%). However, There was not significantly different on diet composition (P=0.188), and number (P=0.075) and the relative fatness (P=0.537) of amphibians between grazing samples and without grazing. 5.Competitive strategies of amphibian larvae I examined the competitive ability of larval toads (Bufo gargarizans) and frogs (Rana kukunoris) which co-occur in the nature pond by activity level, the growth rate and mass at metamorphosis and larval period in a laboratory experiment. The results suggest: In laborary, B.gargarizans adapted himself to different food level by changing activity. At high food level, B. gargarizans increased activity to gain more diet. At low food level, B. gargarizans decreased activity and achieved early metamorphosis. When food resource was limit, R. kukunoris could gain more food than B. gargarizans.
Changes in RNA, DNA, protein contents and growth of turbot Scophthalmus maximus larvae and juveniles
Resumo:
The growth potential of turbot Scophthalmus maximus larvae and juveniles was studied using nucleic acid-based indices and protein variables. The experiment was carried out from 4 to 60 days post hatching (dph). A significant increase in instantaneous growth rate during metamorphosis and retarded growth rate during post-metamorphic phase were observed. Ontogenetic patterns of DNA, RNA and protein all showed developmental stage-specific traits. The RNA:DNA ratio decreased up to 12 dph, then increased rapidly till 19 dph and fluctuated until 35 dph followed by a decline to the end. The RNA:DNA ratio was positively correlated with growth rate of juveniles during the post-metamorphic phase, whereas this ratio was not a sensitive indicator of growth during the pre-metamorphic phase and metamorphosis. The protein:DNA ratio showed a similar tendency to the RNA:DNA ratio. Changes of DNA content and protein:DNA ratio revealed that growth of S. maximus performed mainly by hyperplasia from 4 to 12 dph and hypertrophy until 21 dph during the pre-metamorphic larval phase. Growth was dominantly hypertrophical from the early- to mid-metamorphosing phase and hyperplastic thereafter. The results show that the DNA content and protein:DNA ratio can evaluate growth rates of larval and juvenile S. maximus on a cellular level.
Resumo:
Shell formation is one of the important events during larval development and metamorphosis in bivalves. However, the molecular mechanisms and environmental cues regulating shell initiation and growth are unclear. Here, we report that ferritin, a principal protein for biological iron storage and metabolism, might play a role in larval shell development of the bivalve mollusk Meretrix meretrix. A full-length ferritin subunit cDNA, named as MmeFer, was cloned and characterized. The MmeFer mRNA expression in different developmental stages, from trochophore to post larvae, was analyzed by real-time reverse transcription polymerase chain reaction (RT-PCR). MmeFer mRNA expression in larvae of later developmental stages increased at least 8-fold following trochophores. Moreover, the temporal and spatial expressions of MmeFer mRNA were examined by whole mount in situ hybridization. In the trochophore stage, MmeFer was detectable where it was supposed to be for shell initiation. In the later developmental stages, MmeFer was found near digestive glands and mantle that secret larval shell. MmeFer expression was also detected in larvae cultured in artificial seawater with different iron concentrations ranging from 0 to 100 mu M. These results suggest that ferritin may play a role in the shell formation of mollusks. (C) 2009 Elsevier Inc. All rights reserved.
Resumo:
The hybrid between olive flounder Paralichthys olivaceus and stone flounder Kareius bicoloratus was produced by artificial insemination of olive flounder eggs with stone flounder sperm. Sinistral and dextral are two types of hybrid progeny after metamorphosis. Karyotypes of both hybrid flounders are the same as those of the two parental species. Of the 22 loci examined from 12 allozymes, 12 confirmed hybridization of the paternal and maternal loci in hybrids and no difference was found in allozyme patterns of sinistral and dextral hybrid fishes. RAPD patterns of these specimens were also studied with 38 primers selected from 104 tested. Among them, the PCR products of 30 primers showed hybridization of the paternal and maternal bands. Genetic variation between hybrids and their parental stocks was analyzed by RAPD using 10 of the above 38 primers. The average heterozygosity and genetic distance were calculated. The results suggested that the filial generation could inherit a little more genetic materials from paternal fish than that from maternal fish.
Resumo:
Effects of food availability on larval growth and survival of Meretrix meretrix were studied in two experiments by feeding the larvae with different algae diets and by starving the larvae for different periods of time. Newly hatched larvae of M meretrix were fed with five different marine microalgae species, singly and in various mixtures. Best growth was with Isochrysis galbana as a single species diet. Nutritional value of the other single species diets was in the order of Dunaliella sp.> Phaeodactylum tricornutum > Platymonas subcordiformis > Pavlova viridis. Of the mixtures tested, 50% I. galbana/50% Dunaliella sp., 50% I. galbana/50% P tricornutum, and 50% 1 galbana/50% P subcordiformis, supported growth and metamorphosis equivalent to those of the I. galbana control. At 25 degrees C, larvae of M meretrix were deprived of food for various days to study the growth compensation from the outset of development. The results showed that M meretrix larvae could survive long feeding delays, and even reach metamorphosis without food added, although starvation had significant effects on growth. These results suggested that M meretrix larvae had the capacity to survive 'starvation' using alternative sources of energy. It also showed that growth, survival and metamorphosis of M meretrix were affected by many factors besides food quality and quantity. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
Triploid Penaeus (Fenneropenaeus) chinensis was successfully produced by heat shock. Their metamorphosis, the relationship between body weight and length and difference in appearance between triploids and their diploid siblings under laboratory culture were studied. Hematological studies showed a smaller number of haemocytes, but larger cell volume, in triploids than in diploids. Triploid shrimp did not show higher growth during the immature stage, but exhibited superior growth during the maturation stage. Characteristics of reproductive organs indicated that triploid shrimp may be sterile and sex ratio can be changed through triploidization of shrimp. This paper summarizes the progress made in triploid shrimp research which would be helpful in understanding more about triploids of crustaceans. (c) 2006 Elsevier B.V. All rights reserved.
Resumo:
This review paper provides a brief review on the development of ideas in the fields of the sea level change of the ECS (East China Sea), the history of the Yangtze River entering the sea and paleochannels in the shelf of the ECS since the Last Glacial Maximum (LGM). The paper summarizes two opposite theories about the Yangtze River entering the sea during the LGM. One theory is that the Yangtze River input a lacustrine in the north of Jiangsu province which was defunct in middle Holocene, and the river was once dry. The other was that the Yangtze River still existed and entered into the Okinawa Trough during the LGM, but scholars share different opinions on which course the river ran across and which place the river input the trough. This paper concludes future work is to study the evolution of the Yangtze River and the paleoclimate and the corresponding events as a whole from the view of regional and even global change, and more attention should be paid to the study on mud sediment, the Yangtze River's response to the changes in climate and sea-level, and the channel metamorphosis.