The influence of hunger and breeding temperature on the venom production of the spider Cupiennius salei (Araneae, Ctenidae)

The venom production of the free hunting neotropic spider Cupiennius salei was tested under different breeding conditions. Three groups kept at differ ent temperatures (17, 21 and 25 degrees C) showed that venom production rem ained stable within this temperature range, only at a temperature of 15 deg rees C the spiders stopped feeding and venom synthesis. Hunger periods do n ot have a direct effect on the released venom quantity. Two groups of spide rs - the first group after a four and the second after an eight weeks hunge r period - were compared and no difference in venom production was found, S uch long fasting periods are a natural situation for spiders. In this case Cupiennius salei reduces its body weight but not venom supply. This means t hat body weight is a parameter only of short-term fitness which changes wit h the actual living conditions (temperature, feeding intervals) of each ind ividual, Long-term fitness is best described by the prosoma length, which w as formed during the juvenile growth of each spider and is rather invariabl e in adulthood. It was shown that the quantity of released venom is better correlated with the length of the prosoma than with the weight of the anima l. This means that venom production is mostly an indicator of longterm fitn ess. (C) 1999 Elsevier Science Ltd. All rights reserved.