The genetics‐morphology‐behavior trifecta: Unraveling the single greatest limitation affecting our understanding of chondrichthyan evolution

Gayford, Joel H.

doi:10.1002/ece3.10204

Cited by 4 publications

(4 citation statements)

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“…Multiple paternity (where a single brood consists of individuals sired by more than one male) is a known phenomenon in M. henlei (Byrne and Avise, 2012; Chabot and Haggin, 2014; Réndon-Herrera et al, 2022) and could hypothetically contribute to morphological variation. However, the potential influence of multiple paternity is difficult to quantify due to uncertainty regarding the genetic basis of morphological traits in sharks (Gayford, 2023), and geographic variation in the extent of multiple paternity (Chabot and Haggin, 2014; Réndon-Herrera et al, 2022). Even if the genotypes of potential sires do not result in substantial morphological variation, multiple paternity could result in morphological differences between embryos due to latency of fertilisation within a brood.…”

Section: Discussionmentioning

confidence: 99%

“…However, the potential influence of multiple paternity is difficult to quantify due to uncertainty regarding the genetic basis of morphological traits in sharks (Gayford, 2023), and geographic variation in the extent of multiple paternity (Chabot and Haggin, 2014;Réndon-Herrera et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

“…Typically, a mosaic of allometric and isometric growth (where some structure grows disproportionately or proportionately relative to body size respectively) is observed in functionally important morphological measurements, with the nature of these scaling relationships varying between size classes and sexes in some cases (Gayford et al, 2023b). Despite the increasing number of studies addressing the topic of ontogenetic allometry in a range of shark species, there exist a number of factors that severely limit our understanding of the phenomenon, including taxonomic coverage, sample sizes, and an understanding of the genetic/developmental and functional basis of the morphological structures in question (Sternes and Higham, 2022; Gayford, 2023; Gayford et al, 2023a).…”

Section: Introductionmentioning

confidence: 99%

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Insights into ontogenetic scaling and morphological variation in sharks from near-term brown smooth-hound (Mustelus henlei) embryos

Gayford,

Sternes,

Seamone

et al. 2024

Preprint

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Elasmobranchs (sharks and rays) exhibit a wide range of body forms adapted to various ecological niches. Body form differs not only between species, but between life stages of individual species as a result of ontogenetic allometry. In sharks, it has been proposed that these ontogenetic shifts in body form result from shifts in trophic and/or spatial ecology (the allometric niche shift hypothesis). Alternatively, it has been suggested that ontogenetic allometry may result from intrinsic morphological constraints associated with increasing body size, e.g. to counteract shifts in form-function relationships that occur as a function of size and could compromise locomotory performance. One major limitation affecting our understanding of ontogenetic scaling in sharks is that existing studies focus on postpartum ontogeny, ignoring the period of growth that occurs prior to birth/hatching. In this study, we report ontogenetic growth trajectories from 39 near-term brown smooth hound (Mustelus henlei) embryos taken from manually collected measurements. We found that unlike most other species and later ontogenetic stages of M. henlei, these embryos predominantly grow isometrically, and appear to display relatively high levels of morphological disparity. These results provide rudimentary support for the allometric niche shift hypothesis (as in the absence of ontogenetic niche shifts isometry dominates body-form scaling) and provide important insight into early shark ontogeny and morphological/developmental evolution.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Insights into ontogenetic scaling and morphological variation in sharks from near-term brown smooth-hound (Mustelus henlei) embryos

Gayford,

Sternes,

Seamone

et al. 2024

Preprint

Self Cite

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“…Evo-devo studies (e.g. 74 ) focussing on the neurocranium should form the major focus of future studies investigating elasmobranch braincase evolution. Finally, it is important to mention that all phylogenies, models of trait evolution, and calculations of ancestral states are intrinsically hypotheses, subject to revision upon the incorporation of additional data.…”

Section: Discussionmentioning

confidence: 99%

Evolutionary trends in the elasmobranch neurocranium

Gayford,

Brazeau,

Naylor

2024

Sci Rep

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The neurocranium (braincase) is one of the defining vertebrate characters. Housing the brain and other key sensory organs, articulating with the jaws and contributing to the shape of the anteriormost portion of the body, the braincase is undoubtedly of great functional importance. Through studying relationships between braincase shape and ecology we can gain an improved understanding of form-function relationships in extant and fossil taxa. Elasmobranchii (sharks and rays) represent an important case study of vertebrate braincase diversity as their neurocranium is simplified and somewhat decoupled from other components of the cranium relative to other vertebrates. Little is known about the associations between ecology and braincase shape in this clade. In this study we report patterns of mosaic cranial evolution in Elasmobranchii that differ significantly from those present in other clades. The degree of evolutionary modularity also differs between Selachii and Batoidea. In both cases innovation in the jaw suspension appears to have driven shifts in patterns of integration and modularity, subsequently facilitating ecological diversification. Our results confirm the importance of water depth and biogeography as drivers of elasmobranch cranial diversity and indicate that skeletal articulation between the neurocranium and jaws represents a major constraint upon the evolution of braincase shape in vertebrates.

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Heterochrony and Oophagy Underlie the Evolution of Giant Filter‐Feeding Lamniform Sharks

Gayford,

Irschick,

Chin

et al. 2024

Evolution and Development

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Evolutionary transitions toward gigantic body sizes have profound consequences for the structure and dynamics of ecological networks. Among elasmobranchs (sharks and rays), gigantism has evolved on several occasions, most notably in the iconic Megalodon (Otodus megalodon†) and the extant whale shark (Rhincodon typus), basking shark (Cetorhinus maximus), and megamouth shark (Megachasma pelagios), all of which reach total lengths exceeding 6 m and, in some cases, reach 21 m or more. Comparative phylogenetic studies suggest that filter feeding and heterothermy provide two alternative evolutionary pathways leading to gigantism in sharks. These selection‐based explanations for gigantism are important; however, our understanding of evolutionary transitions in body size is fundamentally constrained without a proximate, mechanistic understanding of how the suite of adaptations necessary to facilitate gigantism evolved. Here we propose the heterochrony hypothesis for the evolution of the giant filter‐feeding shark ecomorphotype. We suggest that craniofacial adaptations for oophagy in embryonic stages of lamniform sharks are retained through ontogeny in C. maximus and M. pelagios by paedomorphosis, resulting in an enlarged head and mouth relative to the rest of the body, even in adulthood. This change in developmental timing enables these taxa to optimize prey acquisition, which is thought to be the limiting factor for the evolution of gigantism in filter‐feeding marine vertebrates. We discuss the concordance of this hypothesis with current developmental, morphological, and evolutionary data, and we suggest future means by which the hypothesis could be tested.

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The genetics‐morphology‐behavior trifecta: Unraveling the single greatest limitation affecting our understanding of chondrichthyan evolution

Abstract: Sharks, rays, and chimaera form the clade Chondrichthyes, a group of cartilaginous fishes thought to have first arisen during the Paleozoic and thus to have survived all five mass extinctions (Guinot

Cited by 4 publications

References 120 publications

Insights into ontogenetic scaling and morphological variation in sharks from near-term brown smooth-hound (Mustelus henlei) embryos

Insights into ontogenetic scaling and morphological variation in sharks from near-term brown smooth-hound (Mustelus henlei) embryos

Evolutionary trends in the elasmobranch neurocranium

Heterochrony and Oophagy Underlie the Evolution of Giant Filter‐Feeding Lamniform Sharks

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