The breeding biology of two sympatric species of tropical intertidal hermit crabs, Clibanarius chapini and C. senegalensis

A one-year study of breeding in the two intertidal hermit crabs Clibanarius chapini Schmitt and C. senegalensis Chevreux and Bouvier showed that both species maintain a high reproductive activity throughout the year. Brief low reproductive activities, found in both species, occurred in different months: C. chapini in November, C. senegalensis in May. While these drops cannot be attributed to any recognisable environmental factor, it is suggested that such pattern may result from competition between the two species. Sex-ratio studies indicated slightly more females than males in both species. The maximal size attained by males of both species is considerably greater than that of the females; in C. senegalensis this is very marked. It is suggested that it may be selectively advantageous for a female to attain a smaller maximal size since her brood must also be accomodated within the shell. As expected for continuously breeding species, recruitment of young into the population is also continuous.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46628/1/227_2004_Article_BF00395523.pd

Simultaneously Hermaphroditic Shrimp Use Lipophilic Cuticular Hydrocarbons as Contact Sex Pheromones

Successful mating is essentially a consequence of making the right choices at the correct time. Animals use specific strategies to gain information about a potential mate, which is then applied to decision-making processes. Amongst the many informative signals, odor cues such as sex pheromones play important ecological roles in coordinating mating behavior, enabling mate and kin recognition, qualifying mate choice, and preventing gene exchange among individuals from different populations and species. Despite overwhelming behavioral evidence, the chemical identity of most cues used in aquatic organisms remains unknown and their impact and omnipresence have not been fully recognized. In many crustaceans, including lobsters and shrimps, reproduction happens through a cascade of events ranging from initial attraction to formation of a mating pair eventually leading to mating. We examined the hypothesis that contact pheromones on the female body surface of the hermaphroditic shrimp Lysmata boggessi are of lipophilic nature, and resemble insect cuticular hydrocarbon contact cues. Via chemical analyses and behavioural assays, we show that newly molted euhermaphrodite-phase shrimp contain a bouquet of odor compounds. Of these, (Z)-9-octadecenamide is the key odor with hexadecanamide and methyl linoleate enhancing the bioactivity of the pheromone blend. Our results show that in aquatic systems lipophilic, cuticular hydrocarbon contact sex pheromones exist; this raises questions on how hydrocarbon contact signals evolved and how widespread these are in the marine environment

Chemical detection of sex and condition in the crayfish Orconectes virilis

Individual crayfish ( Orconectes virilis ) were tested for responses to water containing conspecific individuals of several sex-status categories. Isolated males did not react to “self” water but did show aggressive postures while isolated, nonself male water was introduced. Males' responses to female water was different from responses to male water. Water from aggressing males elicited fewer agonistic postures and more “neutral” postures. Females showed little difference in response to waters from different categories of conspecifics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44870/1/10886_2004_Article_BF00988201.pd

Disturbance pheromones in the crayfish Orconectes virilis

The reactions of individual crayfish to the introduction of waters from tanks containing other individuals were recorded to test for the release of chemicals by stressed crayfish. Female Orconectes virilis and male O. rusticus did not show responses to stressed crayfish. Male O. virilis responded differently to undisturbed and disturbed male crayfish (conspecific and heterospecific). Responses to waters from tanks which contained disturbed individuals were similar whether the source of disturbance was aggressive, predatory, or thermal. Chemical(s) involved appear to persist for at least one hour at room temperature.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44869/1/10886_2005_Article_BF01012121.pd

Distribuição temporal do ermitão Clibanarius vittatus (Anomura, Diogenidae) no litoral do Paraná Temporal distribution of the hermit crab Clibanarius vittatus (Anomura, Diogenidae) from Paraná State coast, Brazil

Um estudo sobre a flutuação temporal da estrutura populacional do ermitão Clibanarius vittatus (Bosc, 1802) foi realizado no Baixio Mirim, Baía de Guaratuba, Estado do Paraná, Brasil (25°52'S, 48°36'W). Clibanarius vittatus é uma espécie largamente estudada, entretanto estudos da biologia populacional desta em diferentes regiões são escassos. Coletas mensais foram realizadas na zona entremarés, de abril/2005 a março/2006. Foram obtidos 1187 ermitões, dos quais, 949 machos, 22 indivíduos intersexo, 204 fêmeas não ovígeras e 12 fêmeas ovígeras. O comprimento do escudo cefalotorácico (CEC) foi medido e agrupado em 10 classes de tamanho. Machos ocorreram em 10 classes de CEC, enquanto fêmeas e intersexos em apenas seis. A razão de sexos total e mensal foi a favor dos machos. Todas as categorias demográficas estiveram presentes o ano inteiro, com exceção dos intersexos e das fêmeas ovígeras. Estas foram pouco frequentes e ocorreram do final da primavera até o outono, e em agosto de 2005. O período reprodutivo foi considerado contínuo-sazonal, com maior intensidade nos meses mais quentes. A razão de sexos nesta população, que é diferente das demais estudadas, corrobora a teoria de migração proposta para esta espécie. O presente estudo constitui o primeiro registro do período reprodutivo desta espécie em águas rasas de clima subtropical quente.<br>A study on the temporal fluctuation of the population structure of the hermit crab Clibanarius vittatus (Bosc, 1802) was carried out at Baixio Mirim tideflat, Guaratuba Bay, Paraná State, southern Brazil (25°52'S, 48°36'W). Clibanarius vittatus is a species widely studied, but studies of population biology of these hermit crabs in different regions are scarce. Samplings were done in the intertidal zone, monthly, from April/2005 to March/2006. A total of 1187 hermit crabs were obtained, among which, 949 males, 22 intersexes, 204 non-ovigerous females and 12 ovigerous females. The cephalothoracic shield length (CSL) was measured and grouped in 10 size classes. Males were distributed in 10 CSL classes while intersexes and females occurred only in six size classes. Males predominated in every month and in the whole population. All demographic categories were present all year round, except intersexes and ovigerous females. These were uncommon and occurred from late spring until autumn and in august/2005. The reproduction was considered seasonal-continuous, with higher intensity in the warmer months. The observed sex ratio in this population, that was different from other ones, corroborates the theory of migration for this species. The present research constitutes the first record of reproductive period of C. vittatus population occurring in warm subtropical shallow waters