Larger males display better stimulatory behavioural patterns and transfer more sperm in the mountain scorpion Zabius fuscus

CARRERA, P. & A. V. PERETTI

Sitges-Barcelona, España

Conferencia; 23 European Colloquium of Arachnology; 2006

European Arachnological Society

Previous studies have shown that among scorpions larger males acquire more mates, suggesting the male size could be an important factor assessed by females during the courtship phase. Larger males spend more time displaying stimulatory behaviour during the sperm transfer phase. Up to date there is no evidence supporting a direct relationship between male-female size ratio, the male´s stimulatory behaviour exhibited during courtship and amount of sperm transferred. The present work focuses in these topics using the mountain scorpion Zabius fuscus (Thorell), a buthid species whose reproductive behaviour is well known. Adult females and males were captured and kept under laboratory conditions. We recorded on digital videos the courtship and sperm transfer phases. Complementary to ethological analyses, we measured the principal morphometric characteristics of specimens and percentage of sperm removed from spermatophore. We analysed the duration and frequency of occurrence of the principal male stimulatory behavioural patterns: “cheliceral massage” (CM), “rubbing with legs” (RL) and the combination of both (CM-RL). Larger males displayed CM-RL more time (Kruskall-Wallis ANOVA: x²= 17.91; p= 0,036) and CM with more frequency in front of the females (One-way ANOVA: F= 2, 89; p= 0,036).  There was a positive correlation between the male-female size ratio and the spermatophore length (Spearman rank correlation: r²= 0,837; p= 0,038), but interestingly this relation was weaker when we consider only absolute values of male´s size and spermatophore length (Spearman rank correlation: r²= 0, 60; p= 0,208). Finally, larger spermatophores transferred more sperm to the female (Lineal Regression: r²= 0,976; p= 0,001). These results suggest that sexual selection may favours larger scorpions males since they can display better stimulatory behaviour to be accepted by females and transfer more sperm by producing larger spermatophores. In addition, this study confirms that scorpion males use luring rather than coercive behaviour during mating.