Biology subjects

Taylor, G. J.

Publications and source records attributed to Taylor, G. J..

4 recordsLinked to original sources

bioRxiv2022

Gradients of orientation, composition and hydration of proteins for efficient light collection by the cornea of the horseshoe crab

The lateral eyes of the horseshoe crab, Limulus polyphemus, are the largest compound eyes within recent Arthropoda. While this visual system has been extensively described before, the precise mechanism allowing vision has remained controversial. Correlating quantitative refractive index (RI) mapping and detailed structural analysis, we demonstrate how gradients of RI in the cornea result from the hierarchical organization of chitin-protein fibers, heterogeneity in protein composition and bromine doping, as well as spatial variation in water content. Combining the realistic cornea structure and measured RI gradients with full-wave optical modelling and ray-tracing approaches, we show that the light collection mechanism depends on both refraction-based graded index (GRIN) optics and total internal reflection. The optical properties of the cornea are governed by different mechanisms at different hierarchical levels, demonstrating the remarkable versatility of arthropod cuticle. One-sentence summaryStructural hierarchy and protein hydration determine the optical performance of the cornea of L. polyphemus.

biophysics↗

bioRxiv2022

Allometric scaling of a superposition eye optimises sensitivity and acuity in large and small hawkmoths

Animals vary widely in body size across and within species. This has consequences in large and small individuals for the function of organs and body parts. How these scale in relation to body size reveals evolutionary investment strategies, often resulting in trade-offs between functions. Eyes exemplify these trade-offs, as they are limited by their absolute size in two key performance features: sensitivity and spatial acuity. Previous studies of the 3D structure of apposition compound eyes, which are ideal models for allometric studies due to their size polymorphism, revealed that allometric scaling improves both local resolution and visual sensitivity in larger bumblebees (Taylor et al., 2019). Here, we build on the established methods and results to investigate allometric scaling in superposition compound eyes - the second prominent eye type in insects - for the first time. Our research highlights a surprising strategy to cope with the challenge of trading off sensitivity and spatial resolution in small eyes, as we show that the eyes of the hummingbird hawkmoth retain an optimal balance of these performance measures across all body sizes.

neuroscience↗

bioRxiv2018

Bumblebee visual allometry results in locally improved resolution and globally improved sensitivity

The quality of visual information that is available to an animal is limited by the size of its eyes. Differences in eye size can be observed even between closely related individuals but we understand little about how this affects visual quality. Insects are good models for exploring the effects of size on visual systems because many species exhibit size polymorphism, which modifies both the size and shape of their eyes. Previous work in this area has been limited, however, due to the challenge of determining the 3D structure of eyes. To address this, we have developed a novel method based on x-ray tomography to measure the 3D structure of insect eyes and calculate their visual capabilities. We investigated visual allometry in the bumblebee Bombus terrestris and found that size affects specific aspects of visual quality including binocular overlap, optical sensitivity across the field of view, and visual resolution in the dorsofrontal visual field. This holistic study on eye allometry reveals that differential scaling between different eye areas provides substantial flexibility for larger bumblebees to have improved visual capabilities.

neuroscience↗

bioRxiv2018

Imaging the evolution of visual specializations in fungus gnats

Many insects use vision to inform their behavior, but visual information differs between habitats and the sensory demands vary with each species ecology. The small size of insects eyes constrains their optical performance, and so it is unsurprising that they have evolved specializations for optimizing the information they obtain from their habitat. Unraveling how behavioral, environmental, and phylogenetic factors influence the evolution of such specializations is difficult, however, because existing techniques to analyze insect eyes require specimens to be preserved beforehand. To facilitate broad comparative studies on insect eyes and the evolution of complex visual behavior, we developed a novel analysis technique that uses x-ray micro-computed tomography to quantify and recreate the visual world of insects. We use our methodology to investigate the eyes of fungus gnats (Orfeliini), a tribe of diminutive Dipterans, to identify the visual specializations they evolved for surviving in different forest habitats and to explore how this changed over 30 million years of evolutionary history. The specimens we studied were preserved in different ways (in ethanol, air dried, and as an endocast in amber), demonstrating that our method provides a new opportunity to quantitatively study and compare the vision of a wide range insects held in museum collections. Our analysis indicates that different visual specializations have evolved between fungus gnat species living in different forest types and that the eyes of gnats from a similar geographic location have evolved to match the changing environmental conditions. Despite the small size of fungus gnats, evolution has evidentially been able to exploit sensory specializations to meet the differing sensory demands of species from a variety of forest habitats.\n\nSignificance statementDo insects have visual specializations that evolve with changes in their environment? To answer this question, a novel analysis technique is described that uses 3D imaging and simulations to compare the vision of ancient amber-embedded insects to those of their extant relatives. This study investigated the vision of fungus gnats to understand how tiny insects use vision to negotiate forests, some of the worlds most visually complex environments. Despite being amongst the smallest of any flying insect, the gnats miniature eyes have evolved visual specializations specifically adapted for different forest types, allowing different species to meet their visual demands of their specific habitats.

evolutionary biology↗