CONICET | Buscador de Institutos y Recursos Humanos

Allometry and asymmetry of male and female body structures and of the spermatophore and hemispermatophore of Bothriurus bonariensis (C.L. Koch, 1842) have been analysed. Specimens were measured three times and the measurements had haigh repeatability. The highest values of phenotypic variation found for the body parts correspnded to those that are involved directly in courtship (IC), especielly the spine-shaped mesal apophysis of the male pedipalp chela, the genital operculum and pectinal plate. Some spermatophore structures show high coefficient of variation (CV), particularly the length of the crest and lateral edge of the lamina and the height of the capsular concavity. In males and females growth relationships were nearly isometric for those characters not directly associated with courtship (NIC), while they appeared almost horizontal for characters involved in courtship. The relationship between body length and spermatophore length in males was moderate, though statistically significant. Body characters show fluctuating asymmetry (FA), whilw the structures of the spermatophores show antisymmetry (AA). In general, there is positive correspondance between phenotypic variation as measured by the coeffiecient of variation and the degree of asymmetry (FA or AA). The regression slopes comparing size of the character with the asymmetry are uniformly negative, suggesting that individuals with bigger characters had lower levels of asymmetry. Anisymmetry of spermatophores may be related to the way in which its parts form in the male reproductive system. Some body and spermatophore characters may be under stabilizing selection (with low CV, FA and AA), while others would be affected by sexual selection (having high CV, FA or AA).

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