The “Celestial Pearl danio” is a miniature Danio (s.s) (Ostariophysi: Cyprinidae): evidence from morphology and molecules

Abstract

The osteology of the miniature cyprinid Celestichthys margaritatus Roberts, type species of Celestichthys Roberts, is described in detail and briefly compared with that of other members of the Rasborinae (notably Danio (s.s), Danionella, Devario, Esomus, Microrasbora, Paedocypris and Sundadanio). Celestichthys margaritatus possesses an “A” stripe on the anal fin and two pigment stripes on the caudal fin (apomorphic features of Danio sensu Fang, 2003). In addition, C. margaritatus exhibits a median projection on the outer arm of the os suspensorium, a derived feature, present only in species of Danio (including D. erythromicron) amongst the Cyprinidae, and a lateral projection on the lateral face of the dentary (present only in Danio, Sundadanio and Paedocypris). Phylogenetic analysis of 1,494 bp of the RAG1 nuclear gene for 31 rasborine taxa, including 5 species of Danio, places C. margaritatus as the sister group to D. erythromicron, and part of a larger monophyletic group including all other species of Danio included for analysis. Based on characters of morphology and its position in a molecular phylogeny of the Rasborinae it is proposed that Celestichthys be placed in the synonymy of Danio, its only member referred to as Danio margaritatus new combination.