It was the account in the literature of the intriguing modifications of the standard orb web in the tetragnathid cave orb spider Meta menardi that first got me interested in subterranean biology back in 2016. I was therefore very pleased when I managed to attract an undergraduate student – the very promising young researcher Daniel Simonsen – to a project quantifying the webs of the cave spider and comparing it to two related aboveground species (Metellina mengei and Tetragnatha montana). The student managed to get a very good sample size with 19 webs analysed from Creswell Crags in Derbyshire, UK (as well as 29 M. mengei webs from Wytham Woods and 25 T. montana from the Oxford University Park), which allowed us to confirm that M. menardi webs show drastic modifications by having very few frame threads with the radial threads instead attaching directly to the cave wall as well as a number of minor modifications. We argue that the lack of frame threads is a likely adaptation to allow novel off-web predation of walking prey stumbling into these radial threads although more research is needed on the actual prey capture behaviour. The resulting paper has now been published in Scientific Reports
Simonsen, D. and Hesselberg, T. (2021). Unique behavioural modifications in the web structure of the cave orb spider Meta menardi (Araneae, Tetragnathidae). Scientific Reports. 11, 92.
https://doi.org/10.1038/s41598-020-79868-w
Abstract
In the last decade there has been a renewed interest in the study of behavioural adaptations to environmental constraints with a focus on adaptations to challenging habitats due to their reduced ecological complexity. However, behavioural studies on organisms adapted to nutrient poor subterranean habitats are few and far between. Here, we compared both morphological traits, in terms of relative leg lengths, and behavioural traits, captured in the geometry of the spider web, between the cave-dwelling spider, Meta menardi, and two aboveground species from the same family (Tetragnathidae); Metellina mengei and Tetragnatha montana. We found that the webs of the cave spider differed significantly from the two surface-dwelling species. The most dramatic difference was the lack of frame threads with the radii in the webs instead attaching directly to the surrounding rock, but other differences in relative web size, web asymmetry and number of capture spiral threads were also found. We argue that these modifications are likely to be adaptations to allow for a novel foraging behaviour to additionally capture walking prey within the vicinity of the web. We found only limited evidence for morphological adaptations and suggest that the cave orb spider could act as a model organism for studies of behaviour in energy-poor environments.
Recent Comments