QUANTITY AND QUALITY OF VENOM RELEASED BY A SPIDER (CUPIENNIUS-SALEI,CTENIDAE)

The amount of venom injected by the spider Cupiennius salei depended o n the efficiency of the mechanical defence of the prey species. Spider s were milked for the first venom (i.e. the first microlitre of venom emitted) versus remaining venom, and for venom regenerated from emptie d glands. HPLC gel filtration and IEF electrophoresis showed that the protein content of the first venom was only half as compared to that o f the remaining venom, and that this was due to a dilution of all prot eins. Venom regeneration came in two speeds. The amount of venom was r egenerated more rapidly than the protein concentration. Newly regenera ted venom as compared to older venom was characterized by a lower conc entration of all proteins and by a higher total concentration of free amino acids, whereas histamine and taurine did not follow this trend. K+ concentration and pH remained similar during venom regeneration. Cr ickets injected with the venoms showed less acute symptoms when the pr otein concentration was lower, namely with the first venom and with ne wly regenerated venom. Consequently, a spider which modulates the quan tity of venom injected into a prey also directly changes the venom qua lity. The ecological consequences of this are discussed. This paper al so discusses which region of a gland (ampulla, extracellular and intra cellular parts of the glandular sac) is involved in the changes of the venom quality.