Development and functional morphology of the larval foregut of two brachyuran species from Northern Brazil

A alimentação é um importante fator para o sucesso no cultivo larval de espécies de caranguejos. Informações sobre as características morfológicas do estômago podem contribuir para revelar o comportamento alimentar larval ou, se há lecitotrofia em algum, ou até mesmo, em todos os estágios do ciclo larval. No presente estudo, o desenvolvimento estrutural do estômago e as funções digestivas foram examinados em larvas de duas espécies de braquiúros, Uca vocator e Panopeus occidentalis, cultivados em laboratório. Durante o desenvolvimento larval, os estômagos das larvas no primeiro e último estágio de zoea e megalopa foram microscopicamente examinados, descritos e ilustrados. Em ambas espécies, o estômago dos estágios de zoea são desenvolvidos e especializados, apresentando uma válvula cardiopilórica e um filtro pilórico funcionais. Oestágio de megalopa possui um moinho gástrico complexo e especializado semelhante àquele encontrado em caranguejos adultos com o aparecimento de estruturas rígidas e calcificadas. Estes resultados apóiam a hipótese de que o comportamento alimentar de cada estágio larval está diretamente relacionado à estrutura morfológica do estômago. Tal fato, fortemente indica que todos os estágios larvais de ambos U. vocator e P. occidentalis necessitam de uma fonte externa de alimento para completar o desenvolvimento larval no ambiente planctônico.

Effect of tank colour on larval performance of the Amazon River prawn Macrobrachium amazonicum

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dinâmica populacional e caracterização conquiliomorfológica de Diplodon ellipticus Spix in Wagner, 1827 (Bivalvia: Unionoida: Hyriidae) da lagoa dos Caiçaras (Piraí, Rio de Janeiro, Brasil)

No presente estudo monitoramos uma população de Diplodon ellipticus Spix in Wagner, 1827 da lagoa dos Caiçaras, Piraí, Rio de Janeiro, e avaliamos alguns aspectos conquiliomorfológicos da larva e do adulto, a relação peso-comprimento, os padrões populacionais tais como crescimento, mortalidade e expectativa de vida, e o ciclo larval. Amostragens mensais foram realizadas de novembro/2012 a novembro/2013 em três pontos da lagoa. Em cada ponto, definimos uma area de 15 m2, que foi subdividida em 15 quadrados de 1m2 cada. Os bivalves foram procurados por três coletores, usando mãos e pés, totalizando 45 minutos de coleta/área. Posteriormente, foram medidos com um paquímetro em relação ao comprimento total, marcados e devolvidos a lagoa. Quinze bivalves foram coletados e analisados em laboratório durante dois anos. Os fatores abióticos (condutividade, temperatura da água, temperatura do ambiente, umidade, pH e oxigênio dissolvido) foram mensurados e amostragens do sedimento e da água foram realizados em cada ponto. Os indivíduos foram agrupados em classes de comprimento com intervalo de 2,0 mm para análise da estrutura de comprimento da população. Os parâmetros de curva de crescimento foram estimados pela rotina ELEFAN (distribuição de frequência) e pelo método de Gulland-Holt (marcação e recaptura), ambos no programa FISAT. A mortalidade foi calculada pelo método da curva de captura convertida em comprimento e a expectativa de vida foi calculada pela equação invertida de von Bertalanffy. Ao todo, 3474 bivalves foram marcados e 1849 recapturados, alguns deles mais de uma vez. O menor bivalve recapturado mediu 23,58 mm e foi recapturado 127 dias depois com 25,50 mm e o maior bivalve recapturado mediu 62,14 mm e foi recapturado 31 dias depois com 62,20 mm. Pelo método indireto analizamos 6922 bivalves com comprimentos variando de 11,37 a 62,49 mm. A maior frequência de comprimento foi encontrada em tamanhos intermediários de 44-46 mm, como foi observado em outras populações de Diplodon. A análise do crescimento, mortalidade e expectativa de vida foram similares em ambos os métodos, por isso, utilizamos em conjunto para ajustar a curva de crescimento da população. A relação peso-comprimento foi alta (r = 0,7-0,8). A avaliação do ciclo reprodutivo indica uma continuidade no desenvolvimento larval ao longo dos meses, à exceção de janeiro/2014. Contabilizamos um total de 54.617 gloquídios, havendo mais indivíduos grávidos com gloquídios (n=5) nos meses de julho e setembro de 2014. Padrão similar foi encontrado em outras espécies de bivalves de água doce, inclusive em Diplodon ellipticus no estado do Paraná. Os gloquídios maduros foram encontrados em amplitudes de temperaturas de 20,1-25,27C e acreditamos que a temperatura pode influenciar na liberação dos mesmos. Os bivalves com o maior e o menor número de gloquídios foram encontrados em novembro/2013 (n= 4759) e setembro/2014 (n= 212), respectivamente. A correlação entre o comprimento do marsúpio e o tamanho da ninhada foi testada pela primeira vez nesse gênero e foi significativa (r= 0,303 , p<0,05). As informações deste estudo são relevantes ao conhecimento da espécie e às futuras ações de gestão que tenham como objetivo preservar as espécies de Diplodon

Use of crude salt in rearing of freshwater giant prawn, Macrobrachium rosenbergii (de Man) larvae

Three different types of culture media: (i) 100% brine (B 100 ), (ii) 75% brine and 25% crude salt (B 75 CS 25 ), and 50% brine and 50% crude salt (B 50 CS 50) were tested to evaluate the possible use of brackish water reconstituted from the crude salt for the production of M. rosenbergii post-larvae. The production rate of 25.26±0.20 PI/l with a corresponding survival rate of 84.20±0.66% was significantly higher (P<0.05) for the larvae reared on B100 than that of 22.10±0.57 Pl/l with a corresponding survival rate of 73.68±1.89% on B50CS50. Larvae cultured on B75CS25 did not show any significant difference (P<0.05) in production as well as in survival of post-larvae than that on B100. The result shows that, for rearing of prawn larvae, use of brine can be replaced up to 25% without any undue reduction in production of post-larvae. However, the production as well as survival rate of post-larvae with 50% replacement (B50CS50) is also appreciable. It is assumed that the mineral constituents of natural seawater might have some triggering effects on prawn larvae in closing their larval cycle.

Systematics and pathogenicity of vibrionaceae associated with the larvae of macrobrachium rosenbergii in hatchery

The great potential for the culture of non-penaeid prawns, especially Macrobrachium rosenbergii in brackish and low saline areas of Indian coastal zone has not yet been fully exploited due to the non availability of healthy seed in adequate numbers and that too in the appropriate period. In spite of setting up several prawn hatcheries around the country to satiate the ever growing demands for the seed of the giant fresh water prawn, the supply still remains fear below the requirement mainly due to the mortality of the larvae at different stages of the larval cycle. In a larval rearing system of Macrobrachium rosenbergii, members of the family Vibrionaceae were found to be dominant flora and this was especially pronounced during the times of mortality However, to develop any sort of prophylactic and therapeutic measures, the pathogenic strains have to be segregated from the lot. This would never be possible unless they were clustered based on the principles of numerical taxonomy It is with these objectives and requirements that the present work involving phenotypic characterization of the isolates belonging to the family Vibrionaceae and working out the numerical taxonomy, determination of mole % G+C ratio, segregation of the pathogenic strains and screening antibiotics as therapeutics at times of emergency, was carried out.

Application of bacterins and yeast Acremonium dyosporii to protect the larvae of Macrobrachium rosenbergii from vibriosis

The fresh water prawn, Macrobrachium rosenbergii, has proven potential for use as an aquaculture species (Hanson & Goodwin, 1997; Kurup, 1984). In India alone, culture of this species of prawn in low saline areas requires about 200 million seed per year (Kurup, 1984). In hatcheries poor survival rate has been associated with vibriosis at di#erent stages of the larval cycle. Members of the family Vibrionaceae associated with the larvae of M. rosenbergii were shown to be pathogenic under laboratory conditions (Bhat et al., 2000, in press). Vibrios have been associated with mortality of penaeid prawns by several workers (Aquacop, 1977; Hameed, 1993; Karunasagar et al., 1994). Two methods have been suggested to protect both the larvae and juveniles from vibriosis; one is the administration of bacterins prepared from pathogenic strains (Itami et al., 1989, 1991; Adams, 1991; Song & Sung, 1990; Sung et al., 1991) and the other is the utilization of yeast 1-3 and 1-6 glucans as immunostimulants for enhancing the non-specific defense system (Sung et al., 1994; Song et al., 1997). In the light of these observations it was hypothesised that bacterins and yeast glucans may also be e#ective in protecting the larvae of M. rosenbergii from vibriosis as has been achieved in the case of penaeids. To examine this hypothesis, the ability of bacterins and an extracellular glucan-producing yeast to increase the overall survival and metamorphosis of larvae in a hatchery, as well as to protect against an experimental challenge under laboratory conditions, was evaluated

Seawater carbonate chemistry and biological processes during experiments with early life stages of the blue mussel Mytilus edulis, 2010

Several experiments have shown a decrease of growth and calcification of organisms at decreased pH levels. There is a growing interest to focus on early life stages that are believed to be more sensitive to environmental disturbances such as hypercapnia. Here, we present experimental data, acquired in a commercial hatchery, demonstrating that the growth of planktonic mussel (Mytilus edulis) larvae is significantly affected by a decrease of pH to a level expected for the end of the century. Even though there was no significant effect of a 0.25-0.34 pH unit decrease on hatching and mortality rates during the first 2 days of development nor during the following 13-day period prior to settlement, final shells were respectively 4.5±1.3 and 6.0±2.3% smaller at pHNBS~7.8 (pCO2~1100-1200 µatm) than at a control pHNBS of ~8.1 (pCO2~460-640 µatm). Moreover, a decrease of 12.0±5.4% of shell thickness was observed after 15d of development. More severe impacts were found with a decrease of ~0.5 pHNBS unit during the first 2 days of development which could be attributed to a decrease of calcification due to a slight undersaturation of seawater with respect to aragonite. Indeed, important effects on both hatching and D-veliger shell growth were found. Hatching rates were 24±4% lower while D-veliger shells were 12.7±0.9% smaller at pHNBS~7.6 (pCO2~1900 µatm) than at a control pHNBS of ~8.1 (pCO2~540 µatm). Although these results show that blue mussel larvae are still able to develop a shell in seawater undersaturated with respect to aragonite, the observed decreases of hatching rates and shell growth could lead to a significant decrease of the settlement success. As the environmental conditions considered in this study do not necessarily reflect the natural conditions experienced by this species at the time of spawning, future studies will need to consider the whole larval cycle (from fertilization to settlement) under environmentally relevant conditions in order to investigate the potential ecological and economical losses of a decrease of this species fitness in the field.

Physiological aspects of the life cycle of the river lamprey, Lampetra fluviatilis L

The life cycle of the river lamprey, L. fluviatilis, is reviewed. The larval lamprey, or ammocoete, is a blind, filter-feeding animal, which normally lies concealed in the silt deposits of streams and rivers. After a period of 3-5 years in fresh water the ammocoete undergoes a metamorphosis in the summer months into a sexually immature, non-feeding stage known as the macrophthalia, which is active. This stage migrates downstream in late winter. It adopts a parasitic existence, in intertidal areas. After 18 months it returns to spawn in fresh water, after a final freshwater stage lasting up to 9 months. The river lamprey dies within a few days after the spawning period of 3-4 weeks, and none survive to spawn the following year.

Using measurements of muscle cell nuclear RNA with flow cytometry to improve assessment of larval condition of Walleye Pollock (Gadus chalcogrammus)

Nuclear RNA and DNA in muscle cell nuclei of laboratory-reared larvae of Walleye Pollock (Gadus chalcogrammus) were simultaneously measured through the use of flow cytometry for cell-cycle analysis during 2009–11. The addition of nuclear RNA as a covariate increased by 4% the classification accuracy of a discriminant analysis model that used cell-cycle, temperature, and standard length to measure larval condition, compared with a model without it. The greatest improvement, a 7% increase in accuracy, was observed for small larvae (<6.00 mm). Nuclear RNA content varied with rearing temperature, increasing as temperature decreased. There was a loss of DNA when larvae were frozen and thawed because the percentage of cells in the DNA synthesis cell-cycle phase decreased, but DNA content was stable during storage of frozen tissue.

Maturity, ovarian cycle, fecundity, and age-specific parturition of black rockfish (Sebastes melanops)

From 1995 to 1998, we collected female black rockfish (Sebastes melanops) off Oregon in order to describe their basic reproductive life history and determine age-specific fecundity and temporal patterns in parturition. Female black rockfish had a 50% probability of being mature at 394 mm fork length and 7.5 years-of-age. The proportion of mature fish age 10 or older significantly decreased each year of this study, from 0.511 in 1996 to 0.145 in 1998. Parturition occurred between mid-January and mid-March, and peaked in February. We observed a trend of older females extruding larvae earlier in the spawning season and of younger fish primarily responsible for larval production during the later part of the season. There were differences in absolute fecundity at age between female black rockfish with prefertilization oocytes and female black rockfish with fertilized eggs; fertilized-egg fecundity estimates were considered superior. The likelihood of yolked oocytes reaching the developing embryo stage increased with maternal age. Absolute fecundity estimates (based on fertilized eggs) ranged from 299,302 embryos for a 6-year-old female to 948,152 embryos for a 16-year-old female. Relative fecundity (based on fertilized eggs) increased with age from 374 eggs/g for fish age 6 to 549 eggs/g for fish age 16.

Temperature-Dependent Growth and Life Cycle of Nemoura sichuanensis (Plecoptera: Nemouridae) in a Chinese Mountain Stream

Plecoptera constitute a numerically and ecologically significant component in mountain streams all over the world, but little is known of their life cycles in Asia. The life cycle of Nemoura sichuanensis and its relationship to water temperature was investigated during a 4-year study in a headwater stream (known as the Jiuchong torrent) of the Xiangxi River in Central China. Size structure histograms suggest that the life cycle was univoltine, and the relationships between the growth of Nemoura sichuanensis, physiological time, and effective accumulated water temperature were described using logistic regressions. The growth pattern was generally similar within year classes but growth rates did vary between year-classes. Our field data suggest a critical thermal threshold for emergence in Nemoura sichuanensis, that was close to 9 degrees C. The total number of physiological days required for completing larval development was 250 days. The effective accumulated water temperature was 2500 degree-days in the field. Development during the life cycle increased somewhat linearly with the physiological time and the effective accumulated water temperature, but some non-linear relationships were best developed by logistic equations.

Seasonal changes, life cycle, and production of a psychrophilic chironomid (Propsilocerus akamusi) in a Chinese Lake

Seasonal changes, life cycle, and production of a psychrophilic Chironomidae species, Propsilacerus akamusi (Tokunage), were studied in eutrophic Lake Donghu. The P akamusi population was characterized by a single annual reproduction period during late November to December, and the larval growth mainly occurred in winter. Most of P akamusi were univoltine, while some of them came to emergence in two years or more. The average density and biomass were 318.9 ind./m(2) and 0.57 g dry weight /m(2) during January 1998 to June 2000, respectively, but these values did not include any summer measurement,; since the larvae aestivated in the deep sediment layer and could not be sampled routinely in summer. The annual production of P akamusi was 2.73g dry weight/m(2), and the corresponding production/biomass ratio was 4.60.

Involvement of p90 ribosomal S6 kinase in termination of cell cycle arrest during development of Artemia-encysted embryos

Artemia has evolved a unique developmental pattern of encysted embryos to cope with various environmental threats. Cell divisions totally cease during the preemergence developmental stage from gastrula to prenauplius. The molecular mechanism of this, however, remains unknown. Our study focuses on the involvement of p90 ribosomal S6 kinase (RSK), a family of serine/threonine kinase-mediating signal transduction downstream of mitogen-activated protein kinase cascades, in the termination of cell cycle arrest during the post-embryonic development of Artemia-encysted gastrula. With immunochemistry, morphology, and cell cycle analysis, the identified Artemia RSK was established to be specifically activated during the post-embryonic and early larval developmental stages when arrested cells of encysted embryos resumed mitoses. In vivo knockdown of RSK activity by RNA interference, kinase inhibition, and antibody neutralization consistently induced defective larvae with distinct gaps between the exoskeleton and internal tissues. In these abnormal individuals, mitoses were detected to be largely inhibited in the affected regions. These results display the requirement of RSK activity during Artemia development and suggest its role in termination of cell cycle (G(2)/M phase) arrest and promotion of mitogenesis. Our findings may, thus, provide insights into the regulation of cell division during Artemia post-embryonic development and reveal further aspects of RSK functions.

Identification of late larval stage developmental checkpoints in Caenorhabditis elegans regulated by insulin/IGF and steroid hormone signaling pathways.

Organisms in the wild develop with varying food availability. During periods of nutritional scarcity, development may slow or arrest until conditions improve. The ability to modulate developmental programs in response to poor nutritional conditions requires a means of sensing the changing nutritional environment and limiting tissue growth. The mechanisms by which organisms accomplish this adaptation are not well understood. We sought to study this question by examining the effects of nutrient deprivation on Caenorhabditis elegans development during the late larval stages, L3 and L4, a period of extensive tissue growth and morphogenesis. By removing animals from food at different times, we show here that specific checkpoints exist in the early L3 and early L4 stages that systemically arrest the development of diverse tissues and cellular processes. These checkpoints occur once in each larval stage after molting and prior to initiation of the subsequent molting cycle. DAF-2, the insulin/insulin-like growth factor receptor, regulates passage through the L3 and L4 checkpoints in response to nutrition. The FOXO transcription factor DAF-16, a major target of insulin-like signaling, functions cell-nonautonomously in the hypodermis (skin) to arrest developmental upon nutrient removal. The effects of DAF-16 on progression through the L3 and L4 stages are mediated by DAF-9, a cytochrome P450 ortholog involved in the production of C. elegans steroid hormones. Our results identify a novel mode of C. elegans growth in which development progresses from one checkpoint to the next. At each checkpoint, nutritional conditions determine whether animals remain arrested or continue development to the next checkpoint.

Larval development of the pedunculate barnacles Octolasmis angulata Aurivillius 1894 and Octolasmis cor Aurivillius 1892 (Cirripedia: Thoracica: Poecilasmatidae) from the gills of the mud crab, Scylla tranquebarica Fabricius, 1798

Detailed studies of larval development of Octolasmis angulata and Octolasmis cor are pivotal in understanding the larval morphological evolution as well as enhancing the functional ecology. Six planktotrophic naupliar stages and one non-feeding cyprid stage are documented in details for the first time for the two species of Octolasmis. Morphologically, the larvae of O. angulata and O. cor are similar in body size, setation patterns on the naupliar appendages, labrum, dorsal setae-pores, frontal horns, cyprid carapace, fronto-lateral gland pores, and lattice organs. Numbers of peculiarities were observed on the gnathobases of the antennae and mandible throughout the naupliar life-cycle. The setation pattern on the naupliar appendages are classified based on the segmentation on the naupliar appendages. The nauplius VI of both species undergoes a conspicuous change before metamorphosis into cyprid stage. The cyprid structures begin to form and modify beneath the naupliar body towards the end of stage VI. This study emphasises the importance of the pedunculate barnacle larval developmental studies not only to comprehend the larval morphological evolution but also to fill in the gaps in understanding the modification of the naupliar structures to adapt into the cyprid life-style.