Growth and maturity of the spider crab Halicarcinus planatus (Brachyura: Hymenosomatidae) females in the southwestern Atlantic Ocean. Can these parameters be influenced by the population sex ratio?

MARTIN VARISCO; JULIA COLOMBO; TOMAS ISOLA; JULIO VINUESA

MARINE BIOLOGY RESEARCH

TAYLOR & FRANCIS AS

Año: 2016

1745-1000

The Halicarcinus planatus populations of the Southwestern Atlantic Ocean (SAO) show a very variable sex ratio and a large size overlapping between females in the last immature instar (ADO) and mature (MAT). We hypothesized that these facts are related and that female impregnation has a central role in this relation. Non-impregnated ADO delay maturity and would continuous to grow, leading to size overlapping. This scenario is most probable in populations with scarcity of males and could affect the growth, maturity time and population structure. The sex ratio and female size distribution of several populations of the SAO were analyzed. Growth and maturity were studied in two populations with different sex ratio (Camarones, a population with males and Rada Tilly, a population without males). Size overlapping was not related to the populatio sex ratio. Size overlapping was due to a variable molt increment and, to a lesser extent, to delayed maturity. Females mated before terminal molt in both populations. However, in Camarones, physiological maturity was not related to impregnation, while in Rada Tilly, vitellogenic oocytes were observed only in impregnated females. Also, differences in the number of spermatophores in female spermathecae were related to the sex ratio. Our results show that the growth and morphological maturity pattern of H. planatus females are not influenced by the population sex ratio. However, physiological maturity was related to female impregnation and sex ratio. Also, the variation in number of spermatophores suggest differences in the mating system related to the population sex ratio.