Ecology of the spider crab Libinia ferreirae (Brachyura: Majoidea): ontogenetic shifts in habitat use

Abstract

We described the ecology of the spider crab Libinia ferreirae testing the habitat segregation during the ontogenetic shifts. Collections were performed monthly by trawling along the coastal area of Cananéia, São Paulo State (southeastern Brazil). Medusae were examined for the presence of any symbionts, and crabs were classified as juveniles (abdomen sealed to the sternite), adults (unsealed abdomen), and ovigerous females (embryos adhered to the pleopods). The environmental factors related to the water column were obtained using a multiparameter probe. In total, 564 adults and 357 juveniles were collected. However, all juveniles were obtained in association with Lychnorhiza lucerna medusae. An increase in the abundance of ovigerous females was observed as chlorophyll levels (phytoplanktonic production) increased, which is consistent with the patterns proposed for crustaceans with planktotrophic larval stages, i.e., the association of larval hatching with oceanic productivity could explain the success in juvenile recruitment approximately two months after the peak in the abundance of ovigerous females (crosscorrelation: r = 0.96). This spider crab shows an ecological strategy of habitat segregation among juvenile and adult individuals, thus avoiding competition for resources among different life cycle stages.

Growth and longevity of the spider crab Libinia ferreirae (Majoidea, Epialtidae)

“…Because of this growth pattern, spider crabs do not exhibit continuous growth during their lifespan, i.e., when crabs reach maturity (gonadal, morphometric or functional), they do not present apparent growth, as seen in other brachyurans (Hartnoll, 1982). Whilst investigating gonad development, Gonçalves et al (2017b) did not observe the production of a new carapace in L. ferreirae when removing the calcified carapace from adult crabs, as seen in the study of Teixeira et al (2008) with Epialtus brasiliensis (Dana 1852). Thus, adult crab size is set by the number of pre-pubertal moults and depends on factors that may influence its life cycle, such as food availability, survival and gonadal and morphometric maturation (Hartnoll et al, 1993).…”

“…To date, studies on this spider crab L. ferreirae have addressed their larval development (Anger et al, 1989;Bakker et al, 1990), symbiotic relationships (Nogueira Jr. and Haddad, 2005;Winter and Masunari, 2006;Gonçalves et al, 2016;2017b), morphology and maturity (Tavares and Santana, 2012;Gonçalves et al, 2017a) and distribution (Braga et al, 2007). However, little is known about the growth of this species.…”

“…We analysed the growth parameters for L. ferreirae based on the similarity of the estimated parameters found in Gonçalves et al (2017a;2017b), to the size and maturity of crabs in real ecosystems. Specimens with CW smaller than 4 mm were sexually undifferentiated and were not included in the size class distribution.…”

“…The largest individuals captured measuring 71.64 and 77.84 mm CW for females and males, respectively. Our sample size was limited by low crab abundance, however, we used ecological parameters established by Gonçalves et al (2017a;2017b), and the data was tested for their confidence limits. We have 95% confidence (bootstrap interactions: 100000) that the mean CW for female is somewhere between -0.37 mm lower than for males up to 4.72 mm higher than for females.…”

“…It is essential to understand the biology and ecology of the species, especially concerning its period of gonadal and morphometric maturity, since the Majoidea crabs reach their maturity before ceasing growth (during the terminal moulting). This study was based on previous knowledge of reproductive maturity and ecology of Majoidea studied by Gonçalves et al (2017a;2017b), in the same region. It is important to use a representative sampling technique that shows the size distribution of crabs in the population, in order to accurately calculate carapace asymptotic width (CW∞).…”