Egg Surface Morphology of Pseudochromoids (Perciformes: Percoidei), with Comments on its Phylogenetic Implications

Differences in shape and arrangement of chorionic projections on the demersal eggs of pseudochromoids were examined using scanning electron microscopy. Eggs of the Pseudochromidae vary from the plesiomorphic condition of pseudochromines, in which filaments attach to the chorion via oblong structures, to the derived condition in pseudoplesiopines and anisochromines, in which the filaments form a tight cluster opposite the micropyle. Congrogadines are further derived, possessing few filaments but having numerous cruciform hooks. The Opistognathidae, Grammatidae, and the plesiopid genus Plesiops all have filaments arranged around the micropyle. However, differences in filament attachment and other egg surface characteristics suggest that the condition is not homologous. The plesiopid genera Fraudella, Paraplesiops, and Trachinops have eggs that possess anchor-shaped hooks. This might be a synapomorphy, but the absence of a definitive outgroup makes character polarizations difficult. The eggs of remaining plesiopid genera are similar to those of the Acanthoclinidae, which possess stalked, filament-bearing structures evenly distributed over the chorion. Two other families of marine perciforms that have demersal eggs with adhesive filaments were also examined. In the Apogonidae, the filaments spiral down the long axis of the egg from the micropylar end. Pomacentrids also produce threads at the micropyle, but have two layers, an outer net-like sheet and an inner layer of filaments similar to those of other taxa in this study. The egg types of neither apogonids nor pomacentrids are homologous with those of pseudochromoids. The difficulty in determining homology between the different egg morphologies, along with the problem of designating outgroups, makes character polarization difficult and phylogenetic hypotheses speculative. Whether or not mouthbrooding is primitive in pseudochromoids cannot be resolved at present.