title: Comparison of the Visual Capabilities of an Amphibious and an Aquatic Goby That Inhabit Tidal Mudflats.
abstract: The mudskipper Periophthalmus modestus and the yellowfin goby Acanthogobius flavimanus are gobiid teleosts that both inhabit the intertidal mudflats in estuaries. While P. modestus has an amphibious lifestyle and forages on the exposed mudflat during low tide, the aquatic A. flavimanus can be found at the same mudflat at high tide. This study primarily aimed to elucidate the differential adaptations of these organisms to their respective habitats by comparing visual capacities and motor control in orienting behavior during prey capture. Analyses of retinal ganglion cell topography demonstrated that both species possess an area in the dorsotemporal region of the retina, indicating high acuity in the lower frontal visual field. Additionally, P. modestus has a minor area in the nasal portion of the retina near the optic disc. The horizontally extended specialized area in P. modestus possibly reflects the need for optimized horizontal sight on the exposed mudflat. Behavioral experiments to determine postural and eye direction control when orienting toward the object of interest revealed that these species direct their visual axes to the target situated below eye level just before a rapid approach toward it. A characteristic feature of the orienting behavior of P. modestus was that they aimed at the target by using the specialized retinal area by rotating the eye and lifting the head before jumping to attack the target located above eye level. This behavior could be an adaptation to a terrestrial feeding habitat in which buoyancy is irrelevant. This study provides insights into the adaptive mechanisms of gobiid species and the evolutionary changes enabling them to forage on land.
authors.affiliation: Graduate School of Biosphere Science, Hiroshima University, Hiroshima, Japan.
authors.forename: Tomo
authors.initials: T
authors.lastname: Takiyama
authors.forename: Sawako
authors.initials: S
authors.lastname: Hamasaki
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yoshida
mesh_terms: D000818:Animals; D005075:Biological Evolution; D017753:Ecosystem; D063366:Estuaries; D000072458:Orientation, Spatial / Q000502:physiology*; D010473:Perciformes / Q000502:physiology*; D011235:Predatory Behavior / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000166:cytology*; D013045:Species Specificity; D014792:Visual Acuity / Q000502:physiology*; D053833:Wetlands