Data from: Exploring the visual world of fossilized and modern fungus gnat eyes (Diptera: Keroplatidae) with X-ray microtomography

Animal eyes typically possess specialised regions for guiding different
behavioural tasks within their specific visual habitat. These
specializations, and evolutionary changes to them, can be crucial for
understanding an animal’s ecology. Here, we explore how the visual systems
of some of the smallest flying insects, fungus gnats, have adapted to
different types of forest habitat over time (~30 mya to today).
Unravelling how behavioural, environmental and phylogenetic factors
influence the evolution of visual specialisations is difficult, however,
because standard quantitative techniques often require fresh tissue and/or
provide data in eye-centric coordinates that prevent reliable comparisons
between species with different eye morphologies. Here, we quantify the
visual world of three gnats from different time periods and habitats using
X-ray microtomography to create high resolution 3D models of the compound
eyes of specimens in different preservation states – fossilized in amber,
dried or stored in ethanol. We present a method for analysing the
geometric details of individual corneal facets and for estimating and
comparing the sensitivity, spatial resolution, and field of view of
species across geographical space and evolutionary time. Our results
indicate that, despite their miniature size, fungus gnats do have
variations in visual properties across their eyes. We also find some
indication that these visual specializations vary across species and may
represent adaptations to their different forest habitats. Overall, the
findings demonstrate how such investigations can be used to study the
evolution of visual specializations – and sensory ecology in general –
across a range of insect taxa from different geographical locations and
across time.