N. E. Doran

Hickmania Troglodytes, the Tasmanian Cave Spider, and its Potential Role in Cave Management

Cave faunas – which often contain a high representation of spiders – are subject to increasing pressure from the effects of epigean habitat degradation and recreational caving activities. Hickmania troglodytes is a prominent member of the Tasmanian cave fauna, a spider of phylogenetic, zoogeographic and ecological importance, but about which little has previously been known. Long-term monitoring has revealed many unusual life-cycle characteristics in this species, most of which occur over long periods of time and are dependent upon environmental stability. The species presents a potentially useful tool in the management and monitoring of cave fauna and karst, as it is large, conspicuous, numerous, ubiquitous, sedentary, functionally significant and potentially sensitive to various sources of disturbance. H. troglodytes may provide a visible and obvious measure of disturbance in and around cave entrances, and may also prove useful in detecting broader scale impacts affecting the entire cave. Many promising developments are being made in terms of cave management in Tasmania, but other issues are less well addressed and still need to be resolved. With further research, the use of indicator or sentinel species may prove to be well suited to the less complex and often sparsely populated subterranean environment, and may play an important role within larger management strategies for cave fauna and karst.

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

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 females 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.