Immunocytochemical localization and secretion process of the toxin CSTX-1 in the venom gland of the wandering spider Cupiennius salei (Araneae : Ctenidae)

Fluorescein and horseradish peroxidase-labeled monoclonal antibodies were u sed to localize the predominant toxic peptide CSTX-1 in the venom gland of the spider Cupiennius salei. There was no polarity of CSTX-1 expression in repleted glands, whereas the glands of previously milked spiders showed a d ecreasing immunofluorescent response from the distal to the proximal portio n. Detailed investigation revealed a new structure in the venom-secreting e pithelium, which is postulated to be an evolutionary adaptation to increasi ng gland volume, CSTX-1 was found to be synthesized and stored as a fully a ctive toxin within complex units, composed of long interdigitating cells ru nning perpendicular to the muscular sheath and extending into the central l umen of the gland. These venom-producing units were found in all sectors of the gland, including the transitional region between the main gland and th e venom duct. The venom is liberated from the venom-producing units into th e glandular lumen following the contraction of the surrounding muscle layer . Free nuclei or other cellular fragments, which would have provided eviden ce for a holocrine secretion process, were not found in the glandular lumen or in the crude venom obtained by electrical stimulation. The fine regulat ion of the spider's venom injection process is postulated to be the functio n of the bulbous ampulla, situated in the anterior third of the venom duct.