Choice and the evolution of habitat specialization: the case of life on shells

Evolutionary Dynamics of Lineage-Specific Class-A GPCR Subsets Reveal Widespread Chemosensory Roles and Adaptations in Lophotrochozoa

“…For example, species adapted to extreme environments like deep-sea hydrothermal vents and those with parasitic lifestyles, such as freshwater leeches and parasitic Platyhelminthes, consistently exhibit reduced numbers of Class-A GPCRs and LSEs across various phyla. Similarly, lineages with alternative chemosensory mechanisms, such as cephalopods (48,49,(88)(89)(90), and those emphasizing sessile behaviors like certain limpets (41), show decreased GPCR and LSE counts. Excluding deep-sea and species with specific lifestyle adaptations, taxa inhabiting various coastal, freshwater, and terrestrial habitats, as well as those with advanced sensory structures across different phyla, typically demonstrate large and divergent LSEs.…”

“…S2B). While the cause of this reduction in limpets is unclear, their sedentary lifestyle, attaching firmly to specific locations for extended periods and grazing on algae and microorganisms on rocky surfaces using their muscular foot, may explain the observed decrease (41). Similarly, bivalves like Congeria kusceri (Dreissenidae), which are adapted to subterranean waters with a highly confined biogeographical distribution, exhibit notable reductions compared to other Dreissena species.…”

Sclerobiosis: A Term for Colonization of Marine Hard Substrates

“…But, why limit its use only to shells? A general rule is that most colonizing organisms are able to employ any kind of substrate indiscriminately, including shells and inanimate substrates (Vermeij, 2020). Additionally, sclerobionts encompass a wide variety of life modes or ethological class, including borers, sessile encrusters, cementers, ephemeral organisms that are not obligate to the hard substrate, such as vagile organisms, or attached organisms associated to any hard substrate.…”

“…This example is complicated because paguroids also change shells as they grow, and the question can be asked: Are these epibionts from when the gastropod was alive, when the crab occupied the sell, or when the crab discarded it? Although epibioses have been documented as unique, specific associations or obligate symbionts associated with hermit crabs (Williams & McDermott, 2004;Vermeij, 2020) -that is, they are unambiguously now part of the living biocenosis of the hermit crab -there are also colonizations of the shell prior to the occupation of the crab, including active selection of shells already colonized (crabs choosing epibiont covered shells) or that have occurred during the intermolt stage of hermit crabs (Bell, 2009;Stanski et al, 2018;Vermeij, 2020).…”

Size Doesn’t Matter: Integrative Taxonomy ShowsCrepidula aduncaandCrepidula norrisiarumHave Overlapping Shell Sizes and Broadly Concordant Distributions

“…The sedentary, suspension-feeding gastropod mollusks known as slipper limpets (Calyptraeidae: Crepidula) provide a useful system for studying the impact of mutualism on phenotypic traits, behavior, and species distribution patterns. Numerous species in this group form long-term epibiotic associations with other invertebrates but many can also be opportunistically found on rocks and other hard substrates (Vermeij, 2020). Because the slipper limpet lacks an operculum and has a large aperture, the edges of the shell must grow to closely fit the curvature and irregularities of the substrate in order to protect the internal body.…”