Resumo:
A habitat may be considered a refuge of countless disturbances, such as refuge against
predation, herbivory, physiological stress, competition, but most studies evaluate refuge
against predation. In the estuarine environment, refuges may be found in several
habitats, such as saltmarshes. Few studies have focused on tropical saltmarshes and
nothing is known about its role as refuge for fauna in this region. Here, we tested the
hypothesis that tropical saltmarshes serve as refuge against (i) variations in temperature
of superficial sediments and (ii) predation for megalopa and juvenile of fiddler crabs.
Measurements (temperature and abundance of megalopa and juveniles along the
vegetation density gradient) and manipulative experiments (field predation experiment)
were used to test the hypothesis. Data from the mensurative experiment indicate that
abundance of megalopa is explained by temperature and vegetation density, while
abundance of juveniles is explained only by vegetation density, suggesting that only
megalopa benefit from milder temperatures that occur in the saltmarshes. Future studies
may elucidate the mechanisms behind this pattern. Data from the manipulative
experiment indicate that predation is similar in the saltmarshes and nearby non vegetated areas, thus, tropical marshes can not be considered as predation refuges for
juveniles of fiddler crabs. In the present study, hermits were attracted to the closed
cages of the non-vegetated area of the experiment. These organisms are found both in
and out of saltmarshes and may act as potential predators, but this has yet to be tested.
Although not offering refuge against predation, the presence of marshes seems to play a
role in the recruitment of juvenile fiddler crabs. The abundances of megalopas are
affected by temperature and this aspect should be studied more deeply. In addition,
future studies should consider the evaluation of the role of hydrodynamics in the
settlement and the availability of food in plants of tropical saltmarshes.
