Interspecies Behavioral Variability of Medaka Fish Assessed by Comparative Phenomics

Recently, medaka has been used as a model organism in various research fields. However, even though it possesses several advantages over zebrafish, fewer studies were done in medaka compared to zebrafish, especially with regard to its behavior. Thus, to provide more information regarding its behavior and to demonstrate the behavioral differences between several species of medaka, we compared the behavioral performance and biomarker expression in the brain between four medaka fishes, Oryzias latipes, Oryzias dancena, Oryzias woworae, and Oryzias sinensis. We found that each medaka species explicitly exhibited different behaviors to each other, which might be related to the different basal levels of several biomarkers. Furthermore, by phenomics and genomic-based clustering, the differences between these medaka fishes were further investigated. Here, the phenomic-based clustering was based on the behavior results, while the genomic-based clustering was based on the sequence of the nd2 gene. As we expected, both clusterings showed some resemblances to each other in terms of the interspecies relationship between medaka and zebrafish. However, this similarity was not displayed by both clusterings in the medaka interspecies comparisons. Therefore, these results suggest a re-interpretation of several prior studies in comparative biology. We hope that these results contribute to the growing database of medaka fish phenotypes and provide one of the foundations for future phenomics studies of medaka fish.

A review of studies on Oryzias dancena

Oryzias dancena (Beloniformes; Teleostei), is a euryhaline teleost that mainly inhabits the brackish or freshwater of river mouths and estuaries around the Bay of Bengal and the Malay Peninsula. It also has a short interval between generations, with spawning possibilities just 60 days after hatching. The aim of this paper is to provide a review for the study of O. dancena based on the studies collected so far, and could form the basis for a wide category of researches including zootoxy, cytogenetics, anesthesia, tagging, salinity tolerance, reproduction, fish disease, chromosome engineering, and trnasgenesis in order to highlight the recent progress in different fields of study using this species.