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

Larval morphology and salinity tolerance of a land crab from West Africa, Cardisoma armatum (Brachyura: Grapsoidea: Gecarcinidae)

The complete larval development of a terrestrial crab from West Africa, Cardisoma armatum Herklots, 1851, was studied in laboratory rearing experiments carried out at various salinities ranging from 0.2& to 45&. Six zoeal stages and one megalopa are described and illustrated. Our experimental results showed that zoeal stages of C. armatum are fairly euryhaline, zoea I to IV tolerating a salinity range of 1545&, and 1535& during later development. However, salinity 15& tended to cause higher mortality and a significantly delayed development in most stages, while 25& allowed for maximum survival through metamorphosis. These observations suggest that C. armatum follows a limited export strategy, where the adults may live in brackish or even freshwater habitats, while a successful larval development is possible only in estuarine or coastal waters with higher salinities, presumbly with an optimum in the lower parts of estuaries with 25&. Before this study, only an incomplete description of the first zoeal stage of C. armatum was available, and complete larval development had been known only for C. carnifex and C. guanhumi. In the present paper, the larval morphologies of these three congeneric species are compared. Within the Gecarcinidae, the complete larval development has been described also for Discoplax hirtipes and Gecarcinus lateralis, while only data for the morphology of the first zoeal stage are available for the other two genera of this family, Epigrapsus and Gecarcoidea. Hence, there are at present no sufficient data, in particular on megalopal morphology, to allow for conclusive intergeneric comparison and identification of familial characters. Gecarcinid zoeal morphology, as far as this is known, is briefly discussed in relation to that in other grapsoid families

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