Biology subjects

Summers, A. P.

Publications and source records attributed to Summers, A. P..

3 recordsLinked to original sources

bioRxiv2026

Habitat impacts the diversification of adhesive discs and skull shape in clingfishes

Specialized suction discs are functional innovations that enable fishes to attach to diverse surfaces and resist hydrodynamic forces. The adhesive discs of clingfishes (Gobiesocidae) vary in size and shape, but it is unclear how ecological factors have influenced their morphological evolution. Here we analyzed the disc and skull shape of 74 clingfish species using micro-CT scanning and 3D geometric morphometrics to investigate the role of habitat and substrate use on patterns of diversification. We also present novel comparisons of adhesive performance for 10 clingfish species. Clingfish interface directly with their environment using their adhesive discs, but we found that the disc and skulls are evolutionary integrated and share similar responses to habitat. Transitions from coastal habitats to coral reefs promoted elevated rates of evolution and morphological disparity across the body, whereas transitions to freshwater did not. Concurrently, repeated shifts from living on hard substrates to softer substrates (i.e., macroalgae and seagrass) were associated with more constrained disc shapes, convergent morphologies, and differences in adhesive performance. We propose that habitat and substrate use make complementary contributions to skeletal diversification in clingfishes, but the adhesive system requires further investigation to disentangle the complex interactions between form and function.

evolutionary biology↗

bioRxiv2025

Twist and Snout: Head and Body Morphologies Determine Feeding Kinematics in Substrate-Biting Fishes

Across teleosts, feeding by biting substrate-attached prey has evolved multiple times and is associated with convergent morphologies that include a deep body and an elongated, tapered head. However, the functional role of these morphologies in substrate-biting fish is not established. Here, we tested the hypothesis that these morphologies function as control surfaces that affect feeding kinematics during biting. To test this hypothesis, we used simplified physical models of substrate-biting fish and examined the role of head, body, and fin morphology in determining feeding kinematics that facilitate the removal of substrate-attached prey. Models simulated the swift lateral movement of the head, previously documented in species biting substrate-attached algae. Using models that capture the natural morphological variation of biters, we tested (i) how different head morphologies affect the speed of the head and (ii) how different body morphologies affect the stability of the body during head movements. We found that the moment of inertia (MOI) of the head and body explained most of the variation in head speed and body displacement. A decrease in head MOI resulted in faster lateral head movements, known to facilitate removal of attached prey. An increase in body MOI, relative to that of the head, stabilized the lateral displacement of the body during bites. Overall, our results suggest that the laterally compressed bodies and tapered snouts function as control surfaces during feeding in substrate-biting fish. We propose that a selective pressure to extend the lateral surface area underlies the prevailing morphological convergence of biting reef fishes.

zoology↗

bioRxiv2024

Something to sink your teeth into: the mechanics of tooth indentation in frugivorous fishes

Frugivorous vertebrates engage in a mutualism with fruiting plants: the former receive a nutrient subsidy and the latter benefit by having their seeds distributed far from parent plants. Vertebrate frugivores like primates and bats have particular morphologies, like wide jaws and blunt teeth, which are thought to aid in dismantling fruit and obtaining trapped sugars. However, variation among frugivores and fruits has made the identification of common frugivore phenotypes difficult. We measured the performance of frugivorous fish dentitions whether this performance was comparable to fruit-eating bats and primates. We also explored how fruit characteristics affect puncture performance, and how indentation of fruit differs mechanically from harder foods like nuts. Finally, we used photoelasticity and videography to visualize how serrasalmid dentitions propagate stresses in simple gel models. We expected that frugivore dentitions would exhibit low force and then high work when engaging fruit tissues. Aligning with our expectation, the most frugivorous serrasalmid we tested, Colossoma, had dental performance that matched the low force, high work model. Indentation behavior differed between food types, both between fruits and nuts, and among different fruits. We also documented considerable differences in the indentation performances of different serrasalmid dentitions, among frugivores, omnivores, and carnivores. We propose that some differences in the morphology of frugivore dentitions make them better for granivory (eating seeds) than the softer fruit tissues. Fishes exhibit convergent mechanical and morphological strategies with other vertebrates for obtaining nutrition from fruits and seeds.

evolutionary biology↗