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Tese de Doutorado Hirose, G. L., 2009
ABSTRACT:The seasonal changes that occur in the region of Ubatuba are mainly related
to the transgressive movement of ACAS. During the seasons of spring and summer the
cold water (ACAS), rich in nutrients, approaching near the coast promotes a decrease of
bottom temperature and a increased of primary production. For Brachyuran larvae, the
increase of primary productivity may be very important. Although they are mainly
predatory zooplankton, field studies have shown that the diatoms may be one of the
most abundant components in the diet of the early larvae. In regions where there is
fluctuation of temperature, photoperiod and/or the availability of food, the reproduction
of the crabs can vary between the seasons, so that increased larval abundance tends to
coincide with the increase of temperature and primary productivity. Considering this,
two questions may be raised: 1 - The characteristics of habitats occupied (adults) could
influence the reproductive intensity of this species? 2 - The ACAS can be considered as
a factor regulating the abundance and distribution of larval species under study? The
larval distribution and abundance of Persephona mediterranea and Menippe nodifrons
were analyzed to answer such questions. The plankton samples were taken seasonally
during the years 2000 to 2002 in the inshore and offshore regions of Ubatuba, SP, using
a commercial fishing boat, with 2 conical plankton nets (mesh of 250 µm) equipped
with a flowmeter. A total of 1643 larvae of P. mediterranea and 563 larvae of Menippe
nodifrons were obtained in samplings. The two species have different patterns of
reproductive intensity (based on larval abundance), which were related to local abiotic
variations, of adult populations. A significant evidence that correlates the ACAS as a
primary factor influencing the increase of larval abundance was not found. The results
of this study facilitates the understanding of the complex life cycle of many Brachyura
that inhabit coastal regions and the possible interactions between the different variations
of environmental factors in which each stage of life is exposed.
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