ZFIN ID: ZDB-PUB-180324-10
Evolution of caudal fin ray development and caudal fin hypural diastema complex in spotted gar, teleosts, and other neopterygian fishes
Desvignes, T., Carey, A., Postlethwait, J.H.
Date: 2018
Source: Developmental dynamics : an official publication of the American Association of Anatomists   247(6): 832-853 (Journal)
Registered Authors: Postlethwait, John H.
Keywords: Amia calva, Danio rerio, Gasterosteus aculeatus, Holostei, Lepisosteus, Ontogeny, plate of connective tissue, tail
MeSH Terms:
  • Animal Fins/anatomy & histology
  • Animal Fins/growth & development*
  • Animals
  • Biological Evolution
  • Fishes/anatomy & histology
  • Fishes/growth & development*
  • Fossils
  • Skeleton/anatomy & histology
  • Skeleton/growth & development
PubMed: 29569346 Full text @ Dev. Dyn.
The caudal fin of actinopterygians transitioned from a heterocercal dorsoventrally asymmetrical fin to a homocercal externally symmetrical fin in teleosts through poorly understood evolutionary developmental mechanisms. We studied the caudal skeleton of major living actinopterygian lineages, including polypteriformes, acipenseriformes, Holostei (gars and bowfin), and teleosts, compared to reports of extinct neopterygians and basal teleosteans. We focused on the hypural diastema complex, which includes 1) a gap between hypurals 2 and 3, that 2) separates two plates of connective tissue at 3) the branching of caudal vasculature; these features had been considered as a shared, derived trait of teleosts, a synapomorphy.
These studies revealed that gars and teleosts share all three features of the hypural diastema complex. Absence of a complex with these features from bowfin, fossil Holostei, and stem Teleostei argues in favor of repetitive, independent emergence in several neopterygian and basal Teleostei lineages, or less likely, many independent losses. We further observed that in gars and teleosts, the earliest developing lepidotrichia align with the horizontal adult body axis, thus participating in external symmetry.
These results suggest that the hypural diastema complex in teleosts and gars represents a homoplasy among neopterygians and that it emerged repeatedly by parallel evolution due to shared inherited underlying genetic and developmental programs (latent homology). Because the hypural diastema complex exists in gars with heterocercal tails, this complex is independent of homocercality. This article is protected by copyright. All rights reserved.