Spinneret spinning field ontogeny and life history observations in the spider Palpimanus uncatus (Araneae: Palpimanidae).

Abstract

As in other Palpimanidae, two pairs of posterior spinnerets present in typical Araneomorphae are vestigial in Palpimanus uncatus Kulczyński, 1909, with only the anterior lateral spinneret (ALS) pair prominent. Nevertheless, in late juvenile and adult females, spigots appear in the ancestral posterior spinneret region (PS). Consistent with these spigots serving cylindrical silk glands, females construct substantial egg sacs. While juveniles and adults exhibit a compressed PS, in postembryos it is fully extended. Piriform silk gland (PI) spigots form a linear array on ALSs from the 1st stadium, increasing in number during ontogeny by addition of PIs of the tartipore-accommodated (T-A) subtype (i.e., functional during proecdyses). The number of T-A PIs added from one stadium to the next and locations occupied by their spigots often exhibit a stereotypic pattern, especially consistent in early instars. The number of non-T-A PIs remains constant through ontogeny from the 1st stadium: one per ALS rather than the two per ALS inferred in a few araneoids. The secondary major ampullate silk gland (2° MaA) spigot, primitively uni-shafted among araneomorphs, has become modified into a multi-shafted spigot with extended base, the number of shafts increasing during ontogeny. However, the multiple ducts that connect to the shafts continue to be accommodated during proecdysis by a single enormous tartipore. Sexual dimorphism is present, with late stadium females having greater numbers of T-A PI spigots and 2° MaA spigot shafts. Observations are presented pertaining to feeding behavior, sexual cannibalism (absent), habitat, winter diapause, numbers of molts, and longevity.