Population ecology of Neritina virginea (Linnaeus, 1758) in the intertidal zone of the Araçá Bay, north coast of São Paulo

Author(s)

Rafael Kenji Murayama

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2016-02-29

Examining board members

Antonia Cecília Zacagnini Amaral; Fosca Pedini Pereira Leite; Leonardo Querobim Yokoyama

• Advisor: Antonia Cecília Zacagnini Amaral

Abstract

This thesis study the population dynamics, growth, secondary production, morphology, sex ratio, migratory behavior and diet of N. virginea in the intertidal region of the Araçá Bay, São Sebastião, SP. Samples were collected monthly in two distinct ways: 1) nested sampling, to determine the spatial and temporal dynamics, and the contribution of three scales to the variation of the spatial dynamics; and 2) Active search to increase the number of individuals marked and recaptured. Individuals collected were marked and had its length measured. For the study of diet and sex ratio, some individuals were dissected, sexed and digestive tract content photographed. With the analysis of the temporal dynamics, higher densities were found in late spring and lower densities in the fall. There were no relationship between average density of individuals and the air temperature and daily rainfall. Regarding the spatial distribution, significance was found in the spatial variation of two scales, with the Residual being the largest contributor to the variance of densities. To estimate the growth and mortality, we used the von Bertalanffy model. We obtained K = 1.1 year -1, ?'= 2.59 and z = 3.94. The secondary production of the rainy and dry season, biomass and turnover rate were evaluated by AFDW, Prainy = 0.9248 g AFDW m-2 yr-1, Brainy = 1.0394 g AFDW m-2, Rp /b rainy = .8931 years-1; Pdry = 0.991 g AFDW m-2 yr-1, Bdry = 1.5536 g AFDW m-2, Rp /b dry = 0.706 years-1. Differences were not found between the periods. The study of morphometry indicates that the growth of the shells of the individuals of this population is isometric. The sex ratio of this population is displaced to females (1:2.19) and during the rainy season this displacement increases, and in the dry, it approaches the expected 1:1. The number of full spermatophores is higher in the rainy than the dry season. No pattern was found in migratory behavior, temporal or spatial. The average distance traveled by individuals was 69,35m ± 7.8 (standard error), with the lowest average distance of 35m and the biggest, of 170m. The diet of this population is dominated by diatoms (%NIi = 29.4 and %FOi = 100) and if considered the importance of biofilm from the sand grains (%NIi =69.9 and %FOi = 100), this population has a very specialized diet and selective trophic strategy. These results, when compared with other works with N. virginea or other gastropod species suggest that the different populations of N. virginea have distinct population dynamics, with distinct population parameters within each other and vary considerably between different species. This shows that N. virginea has a great plasticity in the use of habitats, which gives it great geographical and ecological range (AU)

• FAPESP's process: 13/23513-3 - Population dynamics, growth and secondary production of the gastropoda Neritina virginea (Linnaeus, 1758) in the intertidal zone of Araçá Bay, Northern Coast of São Paulo
• Grantee: Rafael Kenji Murayama
• Support Opportunities: Scholarships in Brazil - Master