The Structure, Function, and Postembryonic Development of the Male and Female Copulatory Organs of the Black Widow Spider Latrodectus Curacaviensis (Müller)

Abstract

A comparison of the structure of the male and female pedipalpi shows that the patella, tibia, tarsus, and the pretarsus of the male are modified. The tarsus in the male is represented by a spoon-shaped cymbium, and the pretarsus by a complex, copulatory palpal organ. This organ in the mature male is a "more specialized" type with an internal receptaculum seminis guarded by the subtegulum, tegulum, median apophysis, radix, terminal apophysis, conductor, and the embolus. The walls of the fundus and the reservoir are of uniform thickness, containing numerous pores on the side facing the gland cells. The ectodistal tooth of the cymbium fits into the socket of the median apophysis, the embolic tip rests on the conductor, and the embolic base is hooked to the basal tooth of the radix. A trigger-like mechanism of extension of the palpal organ is described.The palpal organ arises from the hypodermal cells of the claw fundament. A longitudinal invagination in the ventral lobe of the fundament forms the receptaculum seminis and the dorsal lobes form the accessory sclerites. After transformation of its fundament, the new claw loses connection with the muscle tendons and is short and simple. There is no correlation between the teeth of the claw and the sclerites of the organ.The female copulatory organs consist of paired, dumb-bell-shaped spermathecae; coiled sac-like bursae copulatrices; small, straight fertilization tubes; and blind canals. Ventrally the apparatus is covered by a heavily sclerotized epigynum with an elliptical opening into the atrium which contains the outer openings of the bursae copulatrices. The embolus penetrates the bursa to bring its tip partly within the spermatheca where the broken embolic fragment is later found.The female apparatus arises as a pair of double invaginations of the body wall within the epigastric furrow, immediately ventrad of the opening of the uterus. In successive stages, gradual development of the tissue brings the invaginations outside the epigastric furrow. The two pockets of the invaginations increase in size, the dorsal ones developing into the spermathecae and the ventral ones into the bursae copulatrices.

Copulation with immature females increases male fitness in cannibalistic widow spiders

“…[9], figure 1). Nevertheless, L. hasselti males approach immature females in the laboratory [3], and mount them in nature (M.C.B.A.…”

“…Females may, however, cannibalize males after one copulation (particularly if courtship is brief [5,8]), thus limiting paternity if females remate with a new male [6,8]. Since the tip of each pedipalp can break inside the spermatheca [6,9,10] and block later inseminations, the first mate has the highest paternity [5,10,11]. Breakage does not, however, prevent & 2016 The Author(s) Published by the Royal Society.…”

Morphology and Evolution of Cobweb Spider Malegenitalia (Araneae, Theridiidae)

“…tion, special similarity (similarity in fine detail), and ontogeny (e.g., de Beer 1971;Rieppel 1994Rieppel , 2001Hall 1995;Brigandt 2003). Although one of the most detailed studies of spider palpal ontogeny concerned Latrodectus (Bhatnagar & Rempel 1962), their study was not comparative, so that ontogeny cannot be compared across Theridiidae.…”

“…Heimer & Nentwig (1982) and Heimer (1986) proposed a detailed theory on the evolution of the theridiid ''paracymbium' ' and Heimer (1986) also discussed the homology of the median apophysis. Saaristo (1978) discussed theridiid palpal morphology in detail suggesting several novel hypotheses, and Bhatnagar & Rempel (1962) described the ontogeny of the Latrodectus palp (probably hesperus, although identified as ''curacaviensis''). All these authors disagreed among themselves about homology of palpal sclerites in theridiids in particular and araneoids in general.…”

Multiple sperm storage organs facilitate female control of paternity

“…Females were randomly placed in a same-side treatment (rival males insert in the same spermatheca) or an opposite-side treatment (insertions in opposite spermathecae). All males were manipulated to ensure the assigned insemination pattern by removing the embolus (apical portion of the palp; see Bhatnagar & Rempel 1962) from the palp that was not to be used. Males were anaesthetized with CO 2 and both had the left or right embolus removed (same-side treatment); or one male had the left and one male the right embolus removed (opposite-side treatment).…”