Construction of the orb web in constant and changing abiotic conditions

Abstract

Orb weaving spiders are thought to alter their web-building in different abiotic conditions to maximise prey capture success, while being as silk-efficient as possible. However, there is limited evidence to support this, along with a lack of focus on web variation over time under constant conditions. It is important to better understand web-building in constant and changing abitoic environments to determine if spiders perform adaptive manipulations of their webs. Here, both of these concepts are investigated and the hypothesis that web construction under constant abiotic conditions will not change over time, due to a lack of environmental cues for spiders to respond to, is tested. It is also predicted that Zygiella x-notata will reduce the prey capture aspects in high light intensities, when prey would be more active, and silk can be preserved. The webs of both species were monitored in a constant abiotic environment and Z. x-notata web building behaviour was compared in varying environmental light intensities. These experiments explored patterns of variation in the web characteristics of Argiope bruennichi and Zygiella x-notata over time in a constant abiotic environment and identified significant differences in the web building of Z. x-notata in bright and dark conditions. Results show an overall lack of variation in the webs of A. bruennichi over time apart from radii number in webs of adult females and upper mesh spacing in juvenile webs, and no significant variation in the webs of Z. x-notata over time. No significant differences in the web geometry of Z. x-notata webs occurred in the light intensity treatment, except for lower mesh height becoming reduced in darker conditions. These findings suggest that varying abiotic factors, overall, do not influence the adaptive web building decisions of an orb weaver and could only marginally impact specific web aspects.

Date of Award	23 Jan 2019
Original language	English
Awarding Institution	The University of Bristol
Supervisor	Beth Mortimer (Supervisor) & Daniel Robert (Supervisor)