Abstract
Heterochronic changes in the rate or timing of development underpin many evolutionary transformations. In particular, the onset and rate of bone development have been the focus of many studies across large clades. In contrast, the termination of bone growth, as estimated by suture closure, has been studied far less frequently, although a few recent studies have shown this to represent a variable, although poorly understood, aspect of developmental evolution. Here, we examine suture closure patterns across 25 species of carnivoran mammals, ranging from social-insectivores to hypercarnivores, to assess variation in suture closure across taxa, identify heterochronic shifts in a phylogenetic framework and elucidate the relationship between suture closure timing and ecology. Our results show that heterochronic shifts in suture closure are widespread across Carnivora, with several shifts identified for most major clades. Carnivorans differ from patterns identified for other mammalian clades in showing high variability of palatal suture closure, no correlation between size and level of suture closure, and little phylogenetic signal outside of musteloids. Results further suggest a strong influence of feeding ecology on suture closure pattern. Most of the species with high numbers of heterochronic shifts, such as the walrus and the aardwolf, feed on invertebrates, and these taxa also showed high frequency of closure of the mandibular symphysis, a state that is relatively rare among mammals. Overall, caniforms displayed more heterochronic shifts than feliforms, suggesting that evolutionary changes in suture closure may reflect the lower diversity of cranial morphology in feliforms.
Highlights
Despite recent advances in vascular biology, the mechanisms underpinning vascular development remain poorly understood
Plexus samples were collected from five- and six-day-old wild-type mouse pups and fixed with 2% paraformaldehyde in phosphatebuffered saline (PBS) for 5 h at 48C, thereafter retinas were dissected in PBS
One of the many challenges when simulating blood flow in open domains—such as the subset of retinal vasculature that we present in figure 5—is the impact of the choice of inlet/ outlet boundary conditions on the simulated haemodynamics
Summary
Despite recent advances in vascular biology, the mechanisms underpinning vascular development remain poorly understood. It is crucial to gain further insight into the mechanisms governing the formation of complex vascular networks and their response to external stimuli. The translation of these results holds the key to the improvement of therapies modulating vascular patterning and sprouting for the treatment of stroke, ischaemia, retinopathies or cancer, the leading cause of death worldwide. One of the pressing questions in the field is establishing how primitive vessel networks remodel into a hierarchically branched and functionally perfused. License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited.
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