Morphological characteristics and functional investigation of the abocular side skins on head of six pleuronectiformes fishes

In this study, the morphologies of the abocular side skins on head of six pleuronectiformes fishes were investigated by scanning electron microscopy (SEM). The results showed that a large number of free neuromasts were found on the abocular side skins of Cynoglossus semilaevis and Solea senegalensis with more occurring around the anterior nares and the tips. The free neuromasts in C. semilaevis looked like papillae, covered by many skin wrinkles that consisted of epidermis cells and generally appeared in groups with random arrangement. However, the free neuromasts of S. senegalensis skins, exposed on the surface with a linear arrangement, lie under the bud-like epidermis. A small amount of neuromasts scatter on head skins of Platichthys stellatus, whose morphologies were similar to those of C. semilaevis. Except orifices of mucus secretion, there were no special structures found on the skins of abocular sides of Scophthalmus maximus, Limanda yokohamae and Verasper moseri. According to the differences in organization and distribution of free neuromasts, it is inferred that morphological characteristics of the abocular side skins in pleuronectiformes many be closely related to their feeding behaviors. The distribution characters of free neuromasts on the abocular side skins can provide a certain basis for species classification of pleuronectiformes.