| dc.description.abstract | This study investigated the behavior of crayfishes of the genus Parastacus. Two experiments were
performed: one describing and comparing the agonistic behavior of Parastacus brasiliensis and
Parastacus pilimanus, in laboratory; and another experiment, in the field, where movement and
activity of P. pilimanus were monitored through radio-telemetry. For the first experiment,
individuals of both species were captured and taken to the lab, were they were paired according to
carapace and cheliped length. Ten pairs of P. brasiliensis and thirteen of P. pilimanus, were
formed, being acclimated individually. The pairs were allowed to interact for 20min, during which
they were filmed. Quantifications of aggressiveness, relative aggressiveness, first bout duration,
mean bout duration, number of bouts, latency period, representativity of aggressive behaviors,
number of approaches, number of antennal whips and number of chela punches were made. The
species were compared regarding the formation of dominance hierarchies. P. brasiliensis
exhibited significantly higher values for all parameters, except latency, number of bouts and
antenal whips (only winners), while P. pilimanus executed chela punch more frequently.
Formation of dominance hieararchies was more frequent in P. pilimanus than in P. brasiliensis.
These results point the fossorial species as less aggressive. The behavioral repertory differed from
the expected for crayfish. Another difference was a non-escalated aggression. In the second phase,
two campaigns were performed, one in the spring of 2010 and another in the spring of 2011. In
each, five P. pilimanus were monitored for seven days through radio-telemetry. Verifications of
position of crayfishes were made at 13, 19, 22, 1, 4 and 7h. Air temperature, water temperature,
flow speed, dissolved oxygen, pH and conductivity were measured daily. Daily displacements
were compared. The crayfish were tested for preferably diurnal/nocturnal activity, preferably
upstream/downstream movements and permanence within burrows. The influence of abiotic
parameters in the animal s displacement and the circadian activity were also checked. Only one
crayfish presented significantly higher activity than two other crayfish. There were no significant
differences between for movements. The permanence of the animals was higher within burrows
than in the streambed, and none of the abiotic parameters affected movement. These results were
the same for both campaigns. Between the campaigns, no differences were found for any
parameters. The circadian activity analysis revealed that only three crayfish (one in 2010 and two
in 2011) showed activity concentrated between 19h49min and 02h11min. The results point that P.
pilimanus makes short, but frequent displacements. The high permanence within burrows
characterizes this species as a primary burrower. The low dispersal potential of the studied
population highlights its vulnerability towards a possible disturbs. This weak dispersion ability
might also be related to the occurrence of intersexuality in the group. Both these studies relate to
unknown subjects, when concerning the behavior of Neotropical crayfishes, which stand out for
their differentiation, in relation to the general patterns within the Astacida, especially regarding
the Northern Hemisphere species, better studied so far. | |
