Megaloastia: a most extraordinary jumping spider (APSF 09-8)

APSF 09-8 | Amount: $ 44,901 | Project Leader: P Taylor | Project Period: Jul 2009 - Jul 2012

A project undertaken at Department of Biological Science, Macquarie University, and supervised by Phillip Taylor, John Prenter and Robert Jackson

Jumping spiders differ from other spiders in appearance, visual ability and behaviour. Typical jumping spiders have compact bodies with short, stout, legs and are highly mobile predators with large eyes and the most acute vision among terrestrial arthropods. During the day, typical jumping spiders roam widely, using vision to navigate, search out prey and mates, and to communicate using elaborate postures and ‘dances’. Upon finding prey, they stalk it like tiny eight-legged cats, creeping up slowly and then pouncing once within range. Upon finding a prospective mate, males court with dramatic visual displays in which they move from side to side while waving and posturing with their legs. Conflicts between same-sex rivals are also mediated by elaborate leg-waving displays. Typical jumping spiders may use a silken retreat as a ‘home base’, to which they return each night from their diurnal wanderings, but do not build webs.

Figure 1. Megaloastia mainae feeding on prey captured by stalking, using its large eyes to detect and track prey
Figure 2. Typical habitat of Megaloastia mainae in the Kimberley region of Western Australia

One Australian species, Megaloastia mainae, breaks the basic conventions of jumping spider ‘design’ and lifestyle. Typical jumping spiders of comparable body length (9-11 mm) have legs just 8-12 mm long, are active hunters, and do not build webs; Megaloastia mainae has extraordinarily long and ungainly legs that are as much as 45 mm long in males and 30 mm long in females and has only been reported living in sheet-like webs on the underside of large boulders in the Kimberley region of WA. How, and to what extent, has Megaloastia mainae’s behaviour diverged along with its bizarre morphology and habits? In this species, we expect to find unusual behavioural solutions that will extend our understanding of how morphology, ecology and behaviour evolve in concert.

Both in the field and in the laboratory, we are studying Megaloastia mainae’s web structure and use, hunting behaviour, locomotion and intraspecfic communication, making comparisons with related ‘typical’ jumping spiders to identify the differences.