Embryonic and postembryonic development of the ornamental twin‐tail goldfish

• Published in: Developmental dynamics Vol. 248; no. 4; pp. 251 - 283
• Main Authors: Li, Ing‐Jia, Lee, Shu‐Hua, Abe, Gembu, Ota, Kinya G.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.04.2019; Wiley Subscription Services, Inc
• Subjects: Animal Fins - growth & development; Animals; Artificial selection; Bifurcations; Body Patterning - genetics; Carassius auratus; chordin; Developmental stages; Domestication; dorsal‐ventral patterning; Embryo, Nonmammalian; Embryogenesis; Embryonic Development; Fins; Goldfish - embryology; Goldfish - growth & development; Molecular modelling; Morphology; Mutation; Phenotypes; Tails; Transcription Factors - genetics; Artificial selection; chordin; dorsal-ventral patterning; domestication
• ISSN: 1058-8388; 1097-0177
• DOI: 10.1002/dvdy.15

Background Twin‐tail ornamental goldfish have “bifurcated median fins,” a peculiar morphology known to be caused by a mutation in the chdA gene. However, several ambiguities regarding the development of the phenotype remain due to a paucity of detailed observations covering the entire developmental timeframe. Results Here, we report a detailed comparative description of embryonic and postembryonic development for two representative twin‐tail ornamental goldfish strains and single‐tail common goldfish. Our observations reveal a polymorphic developmental process for bifurcated median fins; disrupted axial skeletal development at early larval stages; and modified bilateral location of the pelvic fin. Conclusions Variations in development of bifurcated median fins and disrupted axial skeletal patterns reflect how artificial selection for adult morphological features influenced molecular developmental mechanisms during the domestication of twin‐tail ornamental goldfish. The polymorphic appearance of bifurcated median fins also implies that, unlike previously proposed hypotheses, the development of these structures is controlled by molecular mechanisms independent of those acting on the pelvic fin. Our present findings will facilitate further study of how modifications of preexisting developmental systems may contribute to novel morphological features. Developmental Dynamics 248:251–283, 2019. © 2019 The Authors. Developmental Dynamics published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists. Key Findings This is the first complete study to describe the developmental progression of twin‐tail goldfish. Disrupted axial skeletal morphology in adults develops from a modified osteogenesis process in vertebral elements. The developmental processes for not only the caudal and anal fins, but also pelvic fin, were changed by artificial selection in twin‐tail goldfish. Polymorphic anal and caudal fin development suggested that in addition to the mutation in the chdA gene, other relevant mutations have accumulated in the twin‐tail goldfish. Our developmental observations pave the way to study how the pre‐existing developmental systems were modified by selective pressure for the formation of a novel morphology.