Full text
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| Author(s): |
Mariana Vellosa Capparelli
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Ribeirão Preto. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC) |
| Defense date: | 2010-03-19 |
| Examining board members: |
Augusto Alberto Valero Flores;
Rodrigo Egydio Barreto;
Sergio Luiz de Siqueira Bueno
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| Advisor: | Augusto Alberto Valero Flores |
| Abstract | |
The grapsid crab Pachygrapsus transversus undergoes an alternative reproductive strategy compared to other brachyurans. This species reaches maturity early in its ontogeny, few months after recruiting to the rocky intertidal. After the main breeding period, females may molt to a stage, marked by a regression of the abdomen and its appendages, which are easily distinguished from both the juvenile and adult form. In this condition, there is no reproductive activity. Because the frequency of different adult morphotypes changes in a seasonal basis, the effect of temperature, photoperiod and their interaction on the incidence of the puberty molt (for juveniles), the maintenance of reproductive activity and the proportion of females molting to a resting stage (adults) was tested. With this purpose, different female groups were kept in captivity under four different combinations of photoperiod and temperature, during two experimental trials. The results of the first experiment show that growth, abdominal allometry and the proportion of females molting to maturity were all higher under winter temperature. In the second experiment, adult females exhibited higher growth rate under winter conditions of photoperiod and temperature, while the proportion of females molting to a resting stage was generally high, with no significant differences among treatments. Growth did not differ between females exhibiting abdominal regression and females holding the adult breeding condition. A third experiment was conducted to examine the dynamics of morphotypic shift under the presence of conspecifics (isolated females, females held with another female, and females held with a male) in different interaction levels (chemical, visual, tactile). In this experiment, no females undergone abdominal regression, and no differences were observed in growth rate and abdominal allometry among treatments. In a final experiment, the behavioral response of males facing resting and active females was compared. Results demonstrated that males can discriminate these morphotypes. Physical contact, including copula, took longer when males were confronted with the reproductive morphotype. It is concluded that growth is mostly influenced by physical variables (temperature and photoperiod), while holding or not reproductive activity, dictated by the incidence of females molting to a resting stage, is apparently related to the presence of conspecifics. This strategy would allow an efficient temporal segregation between reproduction and growth (in the long run), which might be crucial for a species undergoing precocious sexual maturity. (AU) | |