Biology subjects

Kolmann, M. A.

Publications and source records attributed to Kolmann, M. A..

5 recordsLinked to original sources

bioRxiv2025

Tongue bite apparatus highlights functional innovation in a 310-million-year-old ray-finned fish

Gill skeleton modifications for processing prey represent a major source of functional innovation in living ray-finned fishes. Here we present the oldest actinopterygian tongue bite, derived from the gill skeleton, in the Early Pennsylvanian ([~]310 Ma) {dagger}Platysomus parvulus. Unrelated to extant tongue biters, this deep-bodied taxon possesses a large, multipartite basibranchial tooth plate opposing an upper tooth field centered on the vomer. This branchial structure occurs in conjunction with toothed jaws, indicating a role for both in feeding. {dagger}P. parvulus illustrates the assembly of the tongue bite in the geologically younger {dagger}Bobasatraniidae: large opposing dorsal (vomerine) and ventral (basibranchial) crushing plates associated with toothless jaws. The origin of tongue bites falls within the Carboniferous actinopterygian radiation, although postdates the first signs of durophagy in other ray-finned lineages by several million years. This lends support to a protracted long-fuse model of actinopterygian diversification in the aftermath of the End-Devonian Mass Extinction.

paleontology↗

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↗

bioRxiv2023

Comparing Approaches to Specimen Identification using Neotropical Freshwater Fishes in the Barra del Colorado Wildlife Refuge, Costa Rica

As global biodiversity declines continue, conservation efforts are increasingly important in megadiverse areas such as the Neotropics where biodiversity is especially imperiled. The accurate identification of specimens is critical to successful conservation plans. However, in groups such as freshwater fishes, different identification methodologies have documented challenges. Using a biodiversity survey of fishes from the Barra del Colorado Wildlife Refuge in northeastern Costa Rica, we compared: (1) morphological identifications in the field, (2) morphological identifications in the lab by experts, (3) DNA barcode-based identifications, and (4) identifications based on an integrative approach. Our results suggest that both barcode-based identifications and field morphological identifications provided fewer correct species identifications than lab identifications performed by experts using morphology. We attribute shortfalls of DNA barcoding in this case to the misidentification of reference material, the use of outdated taxonomy for references sequences, and the non-uniform representation of groups in public databases across taxa. We suggest the use of an integrative approach to identify freshwater fishes in Costa Rica and other megadiverse areas of the Neotropics where similar issues with public barcode reference libraries exist. We also recommend the creation of regional curated barcode reference libraries to aid in the identification of traditionally difficult to identify species/specimens. We also provide the most up to date species list for the ichthyofauna of the Barra del Colorado Wildlife Refuge identifying 51 species from 42 genera, 21 families, and 17 orders. Generating accurate species lists for protected areas and areas of importance will provide conservation practitioners with effective tools for tracking diversity changes over time.

molecular biology↗

bioRxiv2020

Phylogenomics of piranhas and pacus (Serrasalmidae) uncovers how convergent diets obfuscate traditional morphological taxonomy.

The Amazon and neighboring South American river basins harbor the worlds most diverse assemblages of freshwater fishes. One of the most prominent South American fish families are the Serrasalmidae (pacus and piranhas), found in nearly every continental basin. Serrasalmids are keystone ecological taxa, being some of the top riverine predators as well as the primary seed dispersers in the flooded forest. Despite their widespread occurrence and notable ecologies, serrasalmid evolutionary history and systematics are controversial. For example, the sister taxon to serrasalmids is contentious, the relationships of major clades within the family are obfuscated by different methodologies, and half of the extant serrasalmid genera are suggested to be non-monophyletic. We used exon capture to explore the evolutionary relationships among 64 (of 99) species across all 16 serrasalmid genera and their nearest outgroups, including multiple individuals per species in order to account for cryptic lineages. To reconstruct the timeline of serrasalmid diversification, we time-calibrated this phylogeny using two different fossil-calibration schemes to account for uncertainty in taxonomy with respect to fossil teeth. Finally, we analyzed diet evolution across the family and comment on associated changes in dentition, highlighting the ecomorphological diversity within serrasalmids. We document widespread non-monophyly within Myleinae, as well as between Serrasalmus and Pristobrycon, and propose that reliance on traits like teeth to distinguish among genera is confounded by ecological convergence, especially among herbivorous and omnivorous taxa. We clarify the relationships among all serrasalmid genera, propose new subfamily affiliations, and support hemiodontids as the sister taxon to Serrasalmidae.

evolutionary biology↗

bioRxiv2018

From Armament to Ornament: Performance Trade-Offs in the Sexual Weaponry of Neotropical Electric Fishes

The evolution of sexual weaponry is thought to have marked effects on the underlying static allometry that builds them. These weapons can negatively affect organismal survivability by creating trade-offs between trait size and performance. Here we use three-dimensional geometric morphometrics to study the static allometry of two species of sexually dimorphic electric fishes (Apteronotus rostratus and Compsaraia samueli) in which mature males grow elongate jaws used in agonistic male-male interactions. We quantify jaw mechanical advantage between the sexes of both species to track changes in velocity and force transmission associated with the development of sexual weaponry. We find evidence for trade-offs between skull shape and mechanical advantage in C. samueli, where males with longer faces exhibit lower mechanical advantages, suggesting weaker bite forces. In contrast, males, and females of A. rostratus exhibit no difference in mechanical advantage associated with facial elongation. We hypothesize that differences in the functionality of the sexual weaponry between the two species may drive divergences in the allometric scaling of mechanical advantage.

evolutionary biology↗