| Resumo: |
The present study investigates the growth of Parastacus defossus Faxon, 1898, a fossorial species known only from Brazil (state of Rio Grande do Sul) and Uruguay. The estimated growth curve was calculated for animals from the wild and for juveniles cultivated in the laboratory. The specimens were collected monthly between January, 2003 to August, 2005, in Lami region, municipality of Porto Alegre, state of Rio Grande do Sul, Brazil. The VON BERTALANFFY (1938) growth model was used to estimate the growth curve . To calculate the modal values from the frequency distributions the software PeakFit 4.12© SeaSolve Inc., was employed. The growth curve for field animals is described by the equation: Lt = 30,98 [1 - e-0,0026 (t+44,86)] and for the juveniles cultivated in laboratory: Lt = 19,29 [1 - e-0,0048 (t+37,14)]. It was shown that, under laboratory conditions, the growth was slower than in the field. By comparing the data of P. defossus with those of P. brasiliensis (von Martens, 1869), it was possible to verify a slower growth, both in laboratory as under field conditions. The longevity of the studied species (1198.7 days or 40 months) also showed to be lower when compared to P. brasiliensis.
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