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ABSTRACT Visual ecology, the study of how animals acquire and respond to visual information in nature, has grown rapidly over the past few decades. Research in this field has transformed our understanding of fundamental processes, such as the neurobiological basis of behavior and the diversification of species through sensory drive. The recent growth in the field has been accompanied by leaps in our understanding of the diversity of visual systems and in the development of novel technologies and techniques (for example, those allowing us to measure scenes and signals). With such growth, however, it is more important than ever to integrate wide perspectives and expertise to move the field forward in the most productive way. To that end, in summer 2024, 30 visual ecologists from around the world – spanning all career stages – met to discuss the state of the field. From that meeting, we identified two broad emerging themes in the study of visual ecology. (1) Can we further ‘step inside’ the perceptual experience of a non-human animal? (2) Can foundational ‘rules’ of vision and visual stimuli be identified? Although large questions such as these can feel unanswerable, this is where some of the most exciting discoveries in visual ecology remain to be made. Here, we outline eight relevant areas of research and identify ways in which researchers can bring us closer to answering these complex questions. 

Path dependence influences macroevolutionary predictability by constraining potential outcomes after critical evolutionary junctions. Although it has been demonstrated in laboratory experiments, path dependence is difficult to demonstrate in natural systems because of a lack of independent replicates. Here, we show that two types of distributed visual systems recently evolved twice within chitons, demonstrating rapid and path-dependent evolution of a complex trait. The type of visual system that a chiton lineage can evolve is constrained by the number of openings for sensory nerves in its shell plates. Lineages with more openings evolve visual systems with thousands of eyespots, whereas those with fewer openings evolve visual systems with hundreds of shell eyes. These macroevolutionary outcomes shaped by path dependence are both deterministic and stochastic because possibilities are restricted yet not entirely predictable. 

Abstract Molluscs biomineralize structures that vary in composition, form, and function, prompting questions about the genetic mechanisms responsible for their production and the evolution of these mechanisms. Chitons (Mollusca, Polyplacophora) are a promising system for studies of biomineralization because they build a range of calcified structures including shell plates and spine- or scale-like sclerites. Chitons also harden the calcified teeth of their rasp-like radula with a coat of iron (as magnetite). Here we present the genome of the West Indian fuzzy chiton Acanthopleura granulata, the first from any aculiferan mollusc. The A. granulata genome contains homologs of many genes associated with biomineralization in conchiferan molluscs. We expected chitons to lack genes previously identified from pathways conchiferans use to make biominerals like calcite and nacre because chitons do not use these materials in their shells. Surprisingly, the A. granulata genome has homologs of many of these genes, suggesting that the ancestral mollusc may have had a more diverse biomineralization toolkit than expected. The A. granulata genome has features that may be specialized for iron biomineralization, including a higher proportion of genes regulated directly by iron than other molluscs. A. granulata also produces two isoforms of soma-like ferritin: one is regulated by iron and similar in sequence to the soma-like ferritins of other molluscs, and the other is constitutively translated and is not found in other molluscs. The A. granulata genome is a resource for future studies of molluscan evolution and biomineralization.