ULTRASTRUCTURE OF THE VENOM GLAND OF THE BROWN RECLUSE SPIDER, LOXOSCELES-RECLUSA GERTSCH AND MULAIK (ARANEAE, LOXOSCELIDAE)

Studies were conducted to describe the histology and fine structure of the venom gland of the brown recluse spider, Loxosceles reclusa, and to provide information about venom production and secretion. The L. reclusa venom glands are paired bulbous structures, located in the cephalothoracic cavity; the glands diminish proximally into cuticle-lined ducts that lie within the cheliceral fangs. The secretory epithelium is surrounded by a thick, striated musculature composed of irregularly shaped muscle bundles and is ensheathed by a basement membrane. The venom-producing cells of the gland are pyramidal epithelial cells which extend into the central portion of the gland. The secretory products of the venom gland are produced in the basal area of the epithelial cells as Golgi-associated, membrane-bounded packets of different electron densities and subsequently fuse with a large apical vacuole. Morphological evidence of neuroglandular control of the apical venom release is presented. Evacuation of the gland, following venom release, is subsequently promoted by the constriction of the large musculature. Comparison of venom glands from electrically depleted and normalbiting situations reveals no morphological differences. This study provides the first description of the L. reclusa venom gland in addition to supporting the use of venom obtained from spiders by electrical stimulation. © 1979.