Reproductive strategy of the brown spider Loxosceles intermedia Mello-Leitão (1934) (Araneae; Sicariidae):

functionality of spermatheca secondary structures

Abstract

Introduction: The brown spider Loxosceles intermedia is responsible for thousands of accidents every year in Curitiba. One of the hypotheses refers to the association of reproductive success being linked to the presence of spermatheca with secondary structures. Objective: to relate the pattern of L. intermedia's genitalia with its fecundity. Method: 30 Virgin males and females were paired, and copulatory parameters were recorded. After fertilization, the female was monitored, and oviposition and fertility were recorded. Results: 25 females oviposited, totalling 50 eggsacs, with 80% hatching, 2031 eggs and 1654 hatchlings. Of the receptacles analysed, 78% had two structures, 9% three and 12% four. Of the variables measured only the time spent in copulation, the female's weight and the number of eggsacs correlated with fecundity. However, there was a negative correlation between the number of insertions and the amount of eggsac and eggs, suggesting a relationship with difficulties in sperm transfer. The greater the number of receptacles, the smaller the amount of eggsac produced, not confirming the hypothesis. Conclusion: the low frequency of these variations in the population and the same results obtained 30 years ago suggest that these phenotypes are maintained precisely by functionality, but the low relevance in increasing fecundity maintains the highest proportions of genitalia with only two receptacles. Thus, it is concluded that the fecundity of L. intermedia is related to morphological, behavioural and environmental factors.