Abstract
This study analyses morphology and morphometric growth changes of Halicarcinus planatus females until their terminal moult, and characterises new juvenile stages. Monthly samples were collected in the estuary of the Deseado River, Santa Cruz Province, Argentina. Crabs were sampled between the mid-intertidal and upper subtidal levels. Intermoult stages were analysed in sub-samples of adolescents and adults, and the presence of epizoic organisms was registered. Juveniles and adults were reared at the laboratory and examined for moult changes. All 3376 crabs caught were females, indicating a clear spatial segregation between sexes. Five juvenile stages (immature 1, 2, 3, 4 and adolescent) and a mature one were recognised on the basis of morphology and morphometry. All immature stages differed in cephalothorax width (CW) and abdomen width (AW). Positive allometry was observed in some juvenile stages and isometry in an immature stage and in mature females. Adolescents and adults encompassed a wide range of sizes, and the considerable size overlap between them suggests an anomalous growth process. Moult staging analysis indicated that adolescents have a high incidence of pre-moult stages in winter, when the terminal moult occurs. The measurements performed in laboratory-reared females indicated no abnormal increases during the moult. The terminal moult occurs within a wide size range, perhaps in association with mating.
Highlights
The family Hymenosomatidae is a group of small spider crabs mainly distributed in the Indo-West Pacific region
This crab is larger than almost all other hymenosomatids and can reach up to 19.5 mm in cephalothorax width in the Kerguelen Islands (Richer de Forges, 1977)
The H. planatus population inhabiting the estuary of the Deseado River differs from those of other places
Summary
The family Hymenosomatidae is a group of small spider crabs mainly distributed in the Indo-West Pacific region. Ferrari nus planatus (Fabricius, 1775) is the only species of the family occurring at the southern tip of America and in circumpolar, cold-temperate waters. This crab is larger than almost all other hymenosomatids and can reach up to 19.5 mm in cephalothorax width in the Kerguelen Islands (Richer de Forges, 1977). The species lives mainly in shallow marine waters, and is the dominant brachyuran in subtidal rocky coasts. Individuals are spatially segregated by sex, as indicated by the absence of males in samples from the intertidal and upper subtidal zones all year round (Vinuesa et al, 2005)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
