Ontogenesis, gender, and molting influence the venom yield in the spider Coremiocnemis tropix (Araneae, Theraphosidae).

The demand for spider venom increases along with the growing popularity of venoms-based research. A deeper understanding of factors that influence the venom yield in spiders would therefore be of interest to both commercial venom suppliers and research facilities. The present study addresses the influence of several factors on the venom yield by systematically analyzing the data obtained from 1773 electrical milkings of the Australian theraphosid spider Coremiocnemis tropix. Gender and ontogenesis were found to cause a major effect on the venom yield, as adult female C. tropix yielded significantly more venom than adult males. During ontogenesis, the venom yield increased with increasing size of the spiders. Furthermore, a significant reduction in the venom yield during the 50-day time interval preceding a molt was found. On the other hand, extended milking intervals (up to 449 days) and different states of nutrition (as an indication of how well the spider was fed) did not significantly affect the venom yield. Overall, the present findings suggest that venom production in spiders is carefully balanced between the demand for venom and the energy costs associated with its production. It can therefore be concluded that, in line with the venom optimization hypothesis, venom is a precious resource for spiders, which have implemented control mechanisms to ensure economical venom production and usage.