Morphometric and gonad maturity of the spider crabLibinia ferreiraeBrito Capello, 1871 (Decapoda: Majoidea: Epialtidae) on the south-eastern Brazilian coast

Abstract

Sexual maturity of the spider crab Libinia ferreirae was assessed for each sex, based on body dimensions and observations of gonad condition. A total of 346 crabs were analysed, of which 68% were females. Immature and adult individuals were recognized based on their allometric growth and gonad development. Abdomen width (AW) vs carapace width (CW) and propodus length (PL) vs CW were the relationships that best separated allometric groups of females and males, respectively. For females, gonad and allometric morphological maturity were, respectively, 38.77 and 39.43 mm of CW, which is close to the carapace size of the smallest ovigerous female (38.08 mm). For males, gonad maturity was 34.86 mm of CW and three allometric phases were observed: immature (IM♂), adolescent (AD♂) and adult morphometrically mature (MM♂). The IM♂ phase showed lower values of CW and PL than the AD♂ phase, without spermatophores inside the vas deferens; the AD♂ phase exhibited higher CW values than IM♂, but lower CW and PL values than the MM♂ phase, and the presence of spermatophores in the vas deferens; the MM♂ phase had higher values of CW and PL than the AD♂ phase and spermatophores in the vas deferens. Therefore, females showed synchronic morphometric, gonadal and functional maturity, while in males, gonadal maturity was attained before morphometric maturity, which probably could be a reproductive strategy for this species.

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

“…However, males of some Majoidea species can reach gonadal maturity during pre-pubertal moulting (the second to last moult before terminal moulting), these crabs have gonad maturity but no morphometric maturity. This may allow opportunistic copulation before going through the last moult (terminal moult and end of growth), where individuals have maturity (gonadal and morphometric), and are able to transfer sperm and guard females (Laufer and Ahl, 1995;Gonçalves et al, 2017a). In this way, individuals who undergo early gonadal maturity have an altered reproductive role within the species population dynamics.…”

“…This may lead to selection for an extended pre-puberty intermoult stage (Laufer and Ahl, 1995;Sal Moyano and Gavio, 2012). The spider crab Libinia ferreirae Brito Capello, 1871 is included in this superfamily, the females of these species reach gonadal and morphometric maturity simultaneously; unlike males, who reach gonadal maturity before morphometric maturity (Gonçalves et al, 2017a).…”

“…During their larval and juvenile stages, the crabs grow together with the medusa and use the host for protection, transportation and as a food source. When they reach the adult stage, they live in the benthos associated with many organisms attached to their carapace such as anemones, polychaetes, algae among others (Gonçalves et al, 2017a). Thus, these crabs can move on the sea bed camouflaged (Nogueira Jr. and Haddad, 2005;Winter and Masunari, 2006).…”

“…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.…”