The Anabantoid Genera Ctenops, Luciocephalus, Parasphaerichthys, and Sphaerichthys (Teleostei: Perciformes) as a Monophyletic Group: Evidence from Egg Surface Structure and Reproductive Behaviour

The surface structures of eggs of the anabantoid species Ctenops nobilis, Luciocephalus pulcher, Parasphaerichthys ocellatus and Sphaerichthys osphromenoides are described for the first time after observations with scanning electron microscope. Eggs of these species share a distinctive surface pattern which is not found in any other anabantoid species or even in any other teleost. It consists of a system of almost equidistant ridges. They originate at the vegetal pole and run parallel towards the animal pole where they end in a counter-clockwise spiral near the micropyle. This peculiar pattern presents strong evidence for the monophyly of a group which consists of the genera Ctenops, Luciocephalus, Parasphaerichthys and Sphaerichthys. In addition, the derived pear shape of the eggs of Luciocephalus and Sphaerichthys indicates that they are more closely related to each other than either is any to Ctenops. Due to the lack of information about the egg shape of spawned eggs of Parasphaerichthys the precise phylogenetic placement of that genus within the monophyletic four-taxon-group remains open. The monophyletic origin of that group is further corroborated by the shared mouthbreeding behaviour in Ctenops, Luciocephalus and Sphaerichthys. To date the reproductive behaviour of Parasphaerichthys is unknown.