INVESTIGADORES
FERRETTI Nelson Edgardo
congresos y reuniones científicas
Título:
Where place takes the mating of Grammostola schulzei, Schmidt 1994 (Araneae: Theraphosidae)? An experimental approach.
Autor/es:
FERRETTI NELSON; FERRERO ADRIANA
Lugar:
São Pedro, São Paulo, Brasil
Reunión:
Congreso; 17th International Congress of Arachnology; 2007
Institución organizadora:
Universidad de São Paulo e Instituto Butantan
Resumen:
The place proposed for mating in the major species of Grammostola that came from observations and experiments in laboratory, was the open field. Grammostola schulzei, Schmidt 1994 seems to be the exception, because exhibit a peculiar behaviour that is only register for other burrowing species, like Eupalaestrus weijenberghi Thorell 1894, Acanthoscurria suina Pocock 1903 or Aphonopelma paloma Prentice 1993. To test where G. schulzei mates, we carried out two series of experiments in cages of 30 x 35 x 30 height completing 22 trials. The first series was performed with a layer of soil of 2 cm. and we call “open arena”; in the second, the layer was of 10 cm. and a burrow was excavated against the glass wall using a vial to keep the structure, and allowed the observation constituting “burrowing arena”. In the “open arena” we register a total of seven successful mating, and only four in “burrowing arena”. In the unsuccessfully courtships, where the copulation failed, all involved unreceptive females which did not performed any signal. In all cases the males initiated sexual behavior. In “open arena” the couple mated with no apparent problem of equilibrium, but in one encounter they fell because a flexion of the third leg of the female. This could be due to a fail in the ecdisis, and not by the flexion carapace-abdomen. In all cases the female approached towards the males after palpal drumming and within a radius of 10 cm. approximately. Only in one case the female displayed leg tapping with legs I and palps against the substrate, and the male reoriented to her. In “burrowing arena”, females increased their possibilities of selecting mates because mating can not occur inside the burrow. In one case the female left the burrow and went directly to the male’s position and copulation took place outside the retreat. For the other three mating, the female wait inside and mated at the entrance of the burrow. During the encounters no female displayed leg tapping, but they were receptive because the copulation occurred. Finally we left one female inside the burrow and put two males confined in glasses vials to elicit the female sexual response. The two males courted for at least one and a half hour but there was no response. We are in the presence of a versatile species at the mating time, with no problem to mate in open field, or at the entrance of their burrows. The sexual behavior of females is to indicate the male which is their position and has no meaning in receptiveness. Because G. schulzei is a burrowing tarantula that made retreats under stones, we estimate that mating takes place at the burrow entrance.