Morphological Analysis of Long Bones in Semi-aquatic Mustelids and their Terrestrial Relatives

Abstract

The locomotor environment and behavior of quadrupedal mammals exert functional constraints on their limbs. Therefore long bone shapes are thought to reflect at least partially the species' locomotor ecology. Semi-aquatic species move through two media with distinct density and viscosity and their locomotor apparatus should therefore reflect a trade-off between the divergent functional constraints it faces. Adaptation to a semi-aquatic lifestyle occurred independently in otters (Lutrinae) and minks (Mustelinae). Analyzing semi-aquatic mustelids and their terrestrial relatives, we investigate long bone shape diversity, describe changes in long bone shape associated with a semi-aquatic lifestyle, and discuss the functional consequences of these shape changes. The robustness of the otter bones is highlighted and its potential ballast role discussed. Large epiphyses are observed in otters but this trend seems associated with terrestrial more than with aquatic locomotion. Thus, the most aquatic species, Enhydra lutris, presents narrow knee articulations compared to similar sized less aquatic species. Enhydra lutris presents a fore- and hind limb shape that diverge from that in other otters. Minks show bone shapes similar to each other but only Neovison vison tends to differ from its terrestrial relatives. The evolution of limb shape in this group is strongly correlated with size, locomotor mode, and phylogenetic history, leading to a morphological pattern where the roles of each of these factors are difficult to disentangle.

Selective regimes and functional anatomy in the mustelid forelimb: Diversification toward specializations for climbing, digging, and swimming

“…Stronger extension and flexion of, respectively, the elbow and wrist should bolster the muscular force generated in drag‐based swimming and scratch digging. My finding of relatively greater long bone robustness and relatively longer olecranon process corroborates previous findings for rodents (Samuels & Van Valkenburgh, ), carnivorans as a whole (Samuels et al., ; Van Valkenburgh, ), musteloids (Fabre et al., 2013), and mustelids (Botton‐Divet, Cornette, Fabre, Herrel, & Houssaye, ; Holmes, ; Rose et al., ; Schutz & Guralnick, ). Notably, the overlapping taxa between fossorial and natatorial mustelids are semi‐aquatic mink ( Mustela luterola and Neovison vison ) and fossorial taxa associated with later divergences within Mustelidae ( Melogale sp., Ictonyx striatus , and Poecilogale albinucha ).…”

What about limb long bone nutrient canal(s)? – a 3D investigation in mammals

“…Considering the divergence between lutrines and mustelines in the mustelid sample of femora and based on the strong differences in femur shape and proportions between these two groups (Botton‐Divet et al ), we analyzed the possible correlation between bone proportions and the various parameters, assuming a possible link with the canal geometry parameters. For that analysis, we performed linear regressions of all datasets with L and LR (Table ).…”

A first glimpse at the influence of body mass in the morphological integration of the limb long bones: an investigation in modern rhinoceroses

“…This method can also be easily extended to the study of shape covariation (Goswami and Polly, 2010;Bardua et al, 2019). Bone shape was quantified by placing a set of anatomical landmarks and curve and surface sliding semi-landmarks on the meshes, following Gunz and Mitteroecker (2013), Botton-Divet et al (2016) and Mallet et al (2019). We placed all landmarks and curves using the IDaV LanDMark software (v3.0- Wiley et al, 2005).…”