The reproductive behaviour of the Tasmanian cave spider Hickmania troglodytes (Araneae: Austrochilidae)

Abstract

Hickmania troglodytes, the Tasmanian cave spider, belongs to a relict group with a scattered world distribution, and is of both phylogenetic and zoogeographic interest. It belongs to the superfamily Austrochiloidea (infra-order Araneomorphae) and shares characteristics with more advanced araneomorphs and primitive spiders in the infra-orders Liphistiomorphae and Mygalomorphae. The reproductive behaviour of H. troglodytes (including courtship, mating, egg-sac construction, brooding, emergence, and moulting behaviour) is described, providing the first such account for any member of the Austrochiloidea. Courtship in H. troglodytes is ritualized and involves distinct communicatory gestures (beating with the legs) by the male to identify and protect himself. Males use a pronounced curve in the metatarsus of the second leg to immobilize females during mating; this curve closely matches the contours of the female's cheliceral region. Both courtship and mating are protracted and each can last for over 5.5 h. The egg-sac is large and unusual, with a rigid internal structure that separates the egg mass from the silk walls, while the silk itself seems to be exceptionally resistant to fungal degradation. The young emerge from the egg-sac 8–10 months after laying, a period significantly longer than the typical emergence time of araneomorph spiders (4–8 weeks). It is suggested that the rigid internal structure and the silk of the egg-sacs may help to buffer and protect the eggs and young from biotic and abiotic factors during this extended pre-emergence period.