Behavioural patterns, size-ratio and sperm transfer in the mountain scorpion Zabius fuscus.

CARRERA, P. & A. V. PERETTI.

San Pedro, San Pablo, Brasil

Congreso; 17th International Congress of Arachnology; 2007

International Society of Arachnology

Previous studies have suggested that the scorpion male size could be an important factor influencing the male mating success. Up to date there is no evidence supporting a direct relationship between the male/ female sex ratio, the male stimulatory behavior displayed during the courtship and the final amount of sperm transfer. In the present study we examine these topies using the mountain scorpion Zabius fuscus (Thorell), a buthid specie whose reproductive behavior is relatively well known. We found that larger females show a growing resistance in front ofbigger males (Spearman correlation: -0.286, p = 0.49) contrasting with previous studies that have suggested that the larger males spent less time during the "Promenade a deux" (P AD; phase Oí courtship that precedes sperm transfer) because the female are less resistant. We analyzed the duration and frequency of occurrence of the main male stimulatory behavioral patterns: "Cheliceral massage" (CM) and "Rubbing with legs" (RL) and the combination of both (CM-RL). Smaller males spent less time displaying stimulatory behaviors, but with bigger total frequency. There was a positive correlation between the male size and the spermatophore longitude (Linear regression 0.71; P > 0.0001); between the spermatophore longitude and the female size (Linear regression= 0.74; P > 0.0001). But surprisingly the larger males transferred lesser sperm to the female (Linear regression= - 0.77; P = 0.004). We did not find any statistical significant influence of the male size in the success of the sexual interactions (Chi-square = 0.53; P = 0.465), suggesting that the female sexual receptivity is mainly influenced by the male stimulatory patterns, rather than the size- ratio presented in each mating evento Contrasting with previous studies in scorpions, our results suggest that sexual selection may favor smal1er scorpions' males since they are more capable to display better stimulatory behavior to be accepted by females and transfer more sperm. We discuss our results in light of sexual selection hypothesis.