Fin-fold development in paddlefish and catshark and implications for the evolution of the autopod

Frank J. Tulenko, James L. Massey, Elishka Holmquist, Gabriel Kigundu, Sarah Thomas, Susan M.E. Smith, Sylvie Mazan, Marcus C. Davis

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14 Citations (Scopus)

Abstract

The evolutionary origin of the autopod involved a loss of the fin-fold and associated dermal skeleton with a concomitant elaboration of the distal endoskeleton to form a wrist and digits. Developmental studies, primarily from teleosts and amniotes, suggest a model for appendage evolution in which a delay in the AER-to-fin-fold conversion fuelled endoskeletal expansion by prolonging the function of AER-mediated regulatory networks. Here, we characterize aspects of paired fin development in the paddlefish Polyodon spathula (a non-teleost actinopterygian) and catshark Scyliorhinus canicula (chondrichthyan) to explore aspects of this model in a broader phylogenetic context. Our data demonstrate that in basal gnathostomes, the autopod marker HoxA13 co-localizes with the dermoskeleton component And1 to mark the position of the fin-fold, supporting recent work demonstrating a role for HoxA13 in zebrafish fin ray development. Additionally, we show that in paddlefish, the proximal fin and fin-fold mesenchyme share a common mesodermal origin, and that components of the Shh/LIM/Gremlin/Fgf transcriptional network critical to limb bud outgrowth and patterning are expressed in the fin-fold with a profile similar to that of tetrapods. Together these data draw contrast with hypotheses of AER heterochrony and suggest that limb-specific morphologies arose through evolutionary changes in the differentiation outcome of conserved early distal patterning compartments.

Original languageEnglish
Article number20162780
Number of pages9
JournalProceedings of the Royal Society B: Biological Sciences
Volume284
Issue number1855
DOIs
Publication statusPublished - 31 May 2017

Keywords

  • AER
  • Autopod
  • Catshark
  • Fin-fold
  • HoxA
  • Paddlefish

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