RESUMO

The complete larval development of Petrolisthes tuberculatus (including two zoeal stages and the megalopa) is described and illustrated in detail for the first time, based on laboratory-reared material. In order to allow the differentiation of specimens from plankton samples, the larval stages of P. tuberculatus are compared with those known for other porcellanid crabs from Chilean waters (Allopetrolisthes angulosus, Petrolisthes granulosus, P. laevigatus and P. violaceus). As expected, this comparison lead to the inclusion of P. tuberculatus within the "sección Porcellanina" together with the other Chilean species of porcellanids.

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RESUMO

Feeding is an important factor for the successful rearing of larvae of the crab species. Further information on the morphological features of the foregut may to reveal larval feeding behaviour and or/whether there is a lecithotrophy in some or even in all stages of the larval cycle. In the present study, the structural development of the foregut and their digestive functions were examined in larvae of two brachyurans, Uca vocator and Panopeus occidentalis, reared in the laboratory. During larval development, the foreguts of the larvae in the first and last zoeal stages and in the megalopa stage were microscopically examined, described and illustrated. The zoeal foreguts of both species were well developed, showing specialization with a functional cardiopyloric valve and a filter press. The megalopa stage had a complex and specialized gastric mill similar to that found in adult crabs with the appearance of rigidly calcified structures. These results support the hypothesis that the feeding behaviour of each larval stage is directly related to the morphological structure of the foregut. Such facts strongly indicate that all larval stages of both . vocator and P occidentalis need an external food source before completing the larval development in a planktonic environment.

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.

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RESUMO

Current efforts for restocking natural populations of the mangrove crab Ucides cordatus (Linnaeus, 1763) in Brazil have focused on developing a methodology for stimulating the metamorphosis of U. cordatus larvae at a large scale. The aim of the present study was to compare the mortality rates both in individual and mass conditions, during the induction of metamorphosis of megalopa to juvenile in U. cordatus, without the use of mangrove sediment as substrate. Furthermore, the importance of intraspecific antagonistic behavior on survivorship rates during early post-metamorphosis period was investigated. Metamorphosis was induced by the use of water conditioned with conspecific adults (30 indiv. 100 L-1 for 24 hours). In the first assay, megalopae were stimulated into metamorphosis in experimental vials, both under individual and mass rearing conditions. The second assay assessed the interactions between megalopae and first instar juveniles, which have metamorphosed for more than 24 hours. In the third assay, the existence of cannibalistic behavior among first instar juveniles under different experimental densities was investigated. Significant differences between survivorship rates of individuals that metamorphosed under individual and mass rearing conditions were detected. However no cannibalistic behavior between juveniles and megalopae was observed in the second assay. Juveniles reared at a density of 200 indiv.m-2 showed survivorship rates similar to those obtained under individual conditions. Yet 500 juveniles.m-2 treatments showed significantly lower survivorship rates. Intraspecific interactions appear to be an important problem in U. cordatus specifically during the metamorphosis, but not during larval and post-larval rearing.

RESUMO

Current efforts for restocking natural populations of the mangrove crab Ucides cordatus (Linnaeus, 1763) in Brazil have focused on developing a methodology for stimulating the metamorphosis of U. cordatus larvae at a large scale. The aim of the present study was to compare the mortality rates both in individual and mass conditions, during the induction of metamorphosis of megalopa to juvenile in U. cordatus, without the use of mangrove sediment as substrate. Furthermore, the importance of intraspecific antagonistic behavior on survivorship rates during early post-metamorphosis period was investigated. Metamorphosis was induced by the use of water conditioned with conspecific adults (30 indiv. 100 L-1 for 24 hours). In the first assay, megalopae were stimulated into metamorphosis in experimental vials, both under individual and mass rearing conditions. The second assay assessed the interactions between megalopae and first instar juveniles, which have metamorphosed for more than 24 hours. In the third assay, the existence of cannibalistic behavior among first instar juveniles under different experimental densities was investigated. Significant differences between survivorship rates of individuals that metamorphosed under individual and mass rearing conditions were detected. However no cannibalistic behavior between juveniles and megalopae was observed in the second assay. Juveniles reared at a density of 200 indiv.m-2 showed survivorship rates similar to those obtained under individual conditions. Yet 500 juveniles.m-2 treatments showed significantly lower survivorship rates. Intraspecific interactions appear to be an important problem in U. cordatus specifically during the metamorphosis, but not during larval and post-larval rearing.

RESUMO

Current efforts for restocking natural populations of the mangrove crab Ucides cordatus (Linnaeus, 1763) in Brazil have focused on developing a methodology for stimulating the metamorphosis of U. cordatus larvae at a large scale. The aim of the present study was to compare the mortality rates both in individual and mass conditions, during the induction of metamorphosis of megalopa to juvenile in U. cordatus, without the use of mangrove sediment as substrate. Furthermore, the importance of intraspecific antagonistic behavior on survivorship rates during early post-metamorphosis period was investigated. Metamorphosis was induced by the use of water conditioned with conspecific adults (30 indiv. 100 L-1 for 24 hours). In the first assay, megalopae were stimulated into metamorphosis in experimental vials, both under individual and mass rearing conditions. The second assay assessed the interactions between megalopae and first instar juveniles, which have metamorphosed for more than 24 hours. In the third assay, the existence of cannibalistic behavior among first instar juveniles under different experimental densities was investigated. Significant differences between survivorship rates of individuals that metamorphosed under individual and mass rearing conditions were detected. However no cannibalistic behavior between juveniles and megalopae was observed in the second assay. Juveniles reared at a density of 200 indiv.m-2 showed survivorship rates similar to those obtained under individual conditions. Yet 500 juveniles.m-2 treatments showed significantly lower survivorship rates. Intraspecific interactions appear to be an important problem in U. cordatus specifically during the metamorphosis, but not during larval and post-larval rearing.

RESUMO

Megalopae of many decapod crab species accelerate their development time to metamorphosis (TTM) when exposed to natural physical and/or chemical cues characteristic of the parental habitat. In the present study, the influence of natural settlement cues on the moulting rates and development TTM in megalopae of the fiddler crab Uca vocator was investigated. The effects of mud from different habitats (including well-preserved and degraded-polluted mangrove habitats) and conspecific adult 'odours' (seawater conditioned with crabs) on the induction of metamorphosis were compared with filtered pure seawater (control). 95 to 100 percent of the megalopae successfully metamorphosed to first juvenile crab stage in all treatments, including the control. However, the development TTM differed significantly among treatments. Settlement cues significantly shortened development, while moulting was delayed in their absence. The fact that megalopae responded to metamorphosis-stimulating cues originating from both adult and non-adult benthic habitats demonstrates that settlement in this species may occur in a wider range of habitats within the mangrove ecosystem, including impacted areas.

Megalopas de muitas espécies de caranguejos decápodes aceleram seu período de desenvolvimento até a metamorfose (TOM) quando são expostas a estímulos naturais físicos e/ou químicos característicos do habitat parental. No presente estudo, a influência de estímulos naturais sobre as taxas de muda e sobre o PDM foi investigada nas megalopas do caranguejo violinista Uca vocator. Os efeitos da (i) lama de diferentes habitats (incluindo habitats de um manguezal bem preservado e de um degradado e poluído) e (ii) 'odores' dos adultos conspecíficos (água do mar acondicionada com caranguejos) sobre a indução da metamorfose foram comparados com (iii) água do mar pura e filtrada (controle). 95 a 100 por cento das megalopas realizaram a metamorfose com sucesso para o primeiro estágio de caranguejo juvenil em todos os tratamentos, incluindo o controle. No entanto, o PDM diferiu significativamente entre os tratamentos. Os estímulos encurtaram significativamente o desenvolvimento, enquanto que a muda foi retardada na ausência deles. O fato de que as megalopas responderam aos estímulos indutores da metamorfose oriundos de ambos os habitats bentônicos dos adultos e de habitats onde eles são ausentes, demonstra que o assentamento nesta espécie pode ocorrer em uma grande variedade de habitats dentro do ecossistema de manguezal, incluindo áreas impactadas.

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