A Quantitative Study of Environmental Factors Influencing the Seasonal Onset of Reproductive Behaviour in the South American Apple-snail Pomacea canaliculata (Gastropoda: Ampullariidae) |
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Authors: | Albrecht EA; Carreno NB; Castro-Vazquez A |
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Institution: |
Laboratorio de Reproducción y Lactancia (LARLAC), Consejo
Nacional de Investigaciones Cientificas y Técnicas (CONICET), and Cátedra de
Fisiología Normal, Universidad Nacional de Cuyo, Casilla de Correo 855, RA-5500
Mendoza, Argentina |
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Abstract: | Two laboratory experiments were carried out on sets of winter(inactive) pairs of
Pomacea canaliculata (Lamarck), one to studythe influence of water temperature (either
18°C or 25°C,corresponding to late winter and summer temperatures in Mendoza,
respectively)and day length (either 10 h light/day or 14 h light/day, correspondingto the shortest
and the longest day of the year in Mendoza,respectively), and the other to determine the effects
of foodavailability (ad libitum feeding vs. restriction to 25% of thead
libitum requirements) on the frequency of copulation andspawning, on spawn
measurements (number and volume of eggs,and spawn volume), and on an index of the
reproductive effort.Animals in all experimental groups were observed during 4 weeks,after
seven days of acclimation to the experimental aquaria(under low water temperature and short
photoperiod). Low watertemperatures induced a lesser and later activation of copulationand
spawning than that induced by warm temperatures. Day lengthwas without effect on both
behaviours. Both the frequency ofspawning and the reproductive effort index decreased under
restrictedfeeding, without altering the spawn measurements. The latencyperiods for both
copulatory and spawning behaviours were similarin both ad libitum and restrictedly fed
groups. We concludethat water temperature may be the critical factor that causesthe seasonal
onset of copulatory and spawning behaviour in theseapple-snails. However, food availability
may also be a determiningfactor, mainly to trigger spawning activity. These results suggestthat
the factors that control the seasonal onset of the sexualactivities in Pomacea canaliculata are similar to those thatcontrol the seasonal arrest, thereby establishing the annualpattern
of reproduction in this species. (Received 26 January 1998; accepted 23 July 1998) |
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