School of Biomedical Sciences - Research Publications
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ItemThe eyes have it: dim-light activity is associated with the morphology of eyes but not antennae across insect orders(OXFORD UNIV PRESS, 2021-10)Abstract The perception of cues and signals in visual, olfactory and auditory modalities underpins all animal interactions and provides crucial fitness-related information. Sensory organ morphology is under strong selection to optimize detection of salient cues and signals in a given signalling environment, the most well-studied example being selection on eye design in different photic environments. Many dim-light active species have larger compound eyes relative to body size, but little is known about differences in non-visual sensory organ morphology between diurnal and dim-light active insects. Here, we compare the micromorphology of the compound eyes (visual receptors) and antennae (olfactory and mechanical receptors) in representative pairs of day active and dim-light active species spanning multiple taxonomic orders of insects. We find that dim-light activity is associated with larger compound eye ommatidia and larger overall eye surface area across taxonomic orders but find no evidence that morphological adaptations that enhance the sensitivity of the eye in dim-light active insects are accompanied by morphological traits of the antennae that may increase sensitivity to olfactory, chemical or physical stimuli. This suggests that the ecology and natural history of species is a stronger driver of sensory organ morphology than is selection for complementary investment between sensory modalities.
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ItemLong-term captivity is associated with changes to sensory organ morphology in a critically endangered insect(WILEY, 2022-02)Abstract Captive breeding programmes are key to many threatened species reintroduction strategies but could potentially be associated with adaptations to captivity that are maladaptive in their natural habitat. Despite the importance of sensory ecology to biological fitness, few studies explore sensory system adaptations to captivity. Captive environments are devoid of predators and provide ready access to food sources and potential mates, thus reducing the need for individuals to use signals and cues to identify and locate resources or detect potential threats. With reduced complexity of the signalling environment, relaxation of selective pressures may favour reduced investment in sensory organs in captivity. We test this prediction in an iconic critically endangered invertebrate, the Lord Howe Island stick insect Dryococelus australis, which was extirpated from the island in the 1920s/30s and rediscovered on a nearby volcanic stack, Ball's Pyramid, in 2001. Using historical specimens from these populations and specimens from the 8–10th and 14th generations of a long‐term conservation captive breeding programme, we examine differences in behaviourally relevant morphological traits of the compound eyes (visual organs) and antennae (olfactory organs). We find that captivity is associated with smaller compound eye size, smaller eye ommatidia and reduced density of antennal odour receptors. These morphological changes are indicative of reduced sensitivity to visual and olfactory signals and cues, and therefore are likely to have fitness implications when reintroducing a captive population into the wild. Synthesis and applications. We observe differences in sensory organ morphology between wild and captive‐bred populations of the critically endangered Lord Howe Island stick insect. Our results emphasise the importance of incorporating evolutionary biology and sensory ecology into conservation programme design: to minimise the potential for captive breeding environments to compromise sensory systems that support appropriate behaviours upon reintroduction of populations into a natural habitat.