The influence of the absence of light on the onset of first maturity and egg laying in the crayfish Procambarus (Austrocambarus) llamasi (Villalobos, 1955)

Procambarus llamasi is a crayfish species endemic to southeastern Mexico. Of all the portions of a species lifecycle to be understood, reproduction is the most vital. In order to better understand the effect of external factors on the reproductive development of P. llamasi, an experiment was done testing the influence of complete darkness (CD) and a natural light cycle (NL) on first maturity and egg laying. During the 90-day experiment, three tanks were covered with dark plastic to prevent light from entering (complete darkness, CD), and another three were covered with transparent plastic to allow a natural light cycle (14L:12D, NL). Sexually immature juveniles were placed in the tanks and their growth and sexual maturation monitored. At the end of the experiment, the general spawning mean was 24% for the CD treatment and 15% for the NL treatment. The maturation index was 4.04 for the CD and 3.88 for the NL, and the gonadosomatic index was 3.90 for the CD and 4.20 for the NL. In contrast to many other crayfish species, it is determined that complete darkness does not affect growth, survival or reproduction in P. llamasi. Reproductive development in this species may respond to other external factors such as hydrological cycles. (C) 2002 Elsevier Science B.V All rights reserved