Water temperature is a key environmental factor shaping sex determination in many gonochoristic fishes, with direct consequences for population responses to climate warming. This study is the first examination of temperature effects on sex determination in an atherionid fish, a family belonging to a taxonomic group (Atheriniformes) with abundant examples of temperature-dependent sex determination (TSD). It integrates field obs...

We redescribe Hemitrygon akajei (Bürger in Müller and Henle 1841) based on the lectotype and newly collected specimens, and describe Hemitrygon ariakensis sp. nov. from western Japan. Owing to their considerable morphological similarity and sympatric distribution, these two species have been subject to longstanding taxonomic confusion, with one remaining unrecognized as a cryptic species for over 160 years prior to the availab...

Understanding how genetic differentiation is maintained between closely related species with overlapping habitats is a central question in evolutionary biology. The sticklebacks Gasterosteus aculeatus and Gasterosteus nipponicus occur in sympatry with reproductive isolation on the Pacific coast of Hokkaido Island. However, their distributions and hybridization patterns in more northern regions remain largely elusive. Here, we...

A new ophidiid fish, Sirembo quinquefasciatus , is described based on the holotype and 13 paratypes, 125–172 mm in standard length, collected from the southern South China Sea (Gulf of Thailand, off the east coast of Peninsular Malaysia and off the west coast of Borneo). The new species can be distinguished from all other congeners by having two dark longitudinal bands on the anal fin, one along its base, the other submarginal...

Sex changes in fish are commonly driven by social or reproductive advantages associated with body size, and protogyny is particularly prevalent in species exhibiting male territoriality or haremic mating systems. Within the family Serranidae, several species exhibit sexual dimorphism and protogyny; however, in the genus Selenanthias , only Selenanthias analis Tanaka 1918 has been reported to exhibit sexual dimorphism. The pres...