Evolutionary History of Syngnathid Fishes

Abstract

The family Syngnathidae diverged from other teleosts approximately 48 Mya; they originated from Indo‐Pacific regions and then diversified and spread globally. Subsequently, a unique animal group, fishes with ‘male pregnancy’, emerged. Together with their morphological traits, syngnathid fishes established a specialised evolutionary position. Interestingly, all 300 species in this family lost their pelvic fin, which is directly correlated to the absence of the tbxt4 gene. In this family, pregnancy relies on the attached brood pouch in males, and the structure of the pouch varies dramatically within the family owing to their independent evolutionary history. Some species, such as seahorses, have a fully enclosed brood pouch with robust functions. The phylogenomics and adaptive evolution of the species in the family Syngnathidae might elucidate further mechanisms involved in their morphology and male pregnancy. Key Concepts Phylogeny and evolutionary morphology in the family Syngnathidae. Syngnathidfishes represent the endless beauty of the evolution of marine organisms. Syngnathids origin from the Indian‐Pacific and spread globally. Comparative genomics elucidate the genetic basis of the specialized morphology of syngnathids. ‘Male pregnancy’ could be implemented in syngnathids by evolving a complex brood structure and the evolution of genes.