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 ®rst 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 signi®cantly 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.

First evidence of neurons in the male copulatory organ of a spider (Arachnida, Araneae)

“…For example, secretions from such glands are often associated with the production of mating plugs [11]. However, there is no evidence for mating plugs in H. troglodytes [12] and thus the gland present in the embolus would appear to serve other function(s). In theory, males should invest more sperm in high-quality females, but take advantage of any further mating.…”

Web Building Behavior and the Phylogeny of Austrochiline Spiders

“…Filistatines construct funnel webs (Eberhard 1988). Fortunately enough, Hickmania troglodytes constructs a sheet web quite similar to that of austrochilines (Hickman 1967;Forster et al 1987;Doran et al 2001).…”

Spiders in caves

“…Among other subterranean taxa, spiders are distinctive for their ecological role of top predators [3][4][5], and for the variety of functional adaptations [6], therefore representing undervalued models for the understanding the evolution of life in extreme habitats. Accordingly, subterranean spiders have served as models for physiological [7][8][9], ecological [4,5,[10][11][12], ethological [13,14] and biogeographic studies [15][16][17], among others.However, compared with other animal groups, the potential of spiders as model organisms is still under-expressed. It is possible that the paucity of studies is related to the difficulty of working in subterranean habitats and to the rarity of most subterranean species, which pose major impediments to data collection and analysis.…”