Distribution of adult fish and spawning nests of estuarine-dependent amphidromous goby (

Abstract

Adults of the marine-originated amphidromous goby (Gymnogobius petschiliensis) inhabit both freshwater and brackish-water areas, unlike many other amphidromous species, which spend their entire lives, except the larval stage, in freshwater. Furthermore, adult G. petschiliensis individuals incur higher osmoregulatory costs in freshwater than those in hypertonic brackish water under laboratory conditions, suggesting that the ecology of the species is largely dependent on high-salinity (ancestral) environments. Therefore, a detailed information on the ecology of G. petschiliensis will help elucidate the diversity and evolution of amphidromy. Here, this study assessed the habitat use and freshwater dependency of G. petschiliensis in two streams in central Japan. Year-round surveys showed that adult density was higher in freshwater than in brackish water during the non-spawning season. This implies that adults chose salinity habitats according to ecological conditions (e.g. inter- and intraspecific competition, and predation risk) without being bound by physiological preferences. Conversely, most egg clutches were found in brackish water. Furthermore, adult density in brackish water increased with the increase in spawning events, suggesting that the adults migrated downstream for spawning. This preference for spawning in brackish water rather than in freshwater may be attributed to the constraints of their reproductive physiology.

A key evolution in gene expression plasticity for freshwater colonisation in early life stage of fish

“…2, S2). Since amphidromousGymnogobius species are observed to migrate from the sea to freshwater areas while juveniles (Oto, 2021), the increase in Sr/Ca ratios is considered to reflect this juvenile migration. On the other hand, otolith Sr/Ca ratios of one remaining UE individual and all the specimens from the UA (n = 5) and UB (n = 9) populations were constantly low (about 2 × 10 -3 ), suggesting that these individuals were freshwater forms.…”

“…However, a longer-term rearing experiment is necessary to determine whether the larval freshwater tolerance identified in this study or other factors (e.g. those associated with subsequent growth) are critically responsible for landlocking because the larval period of amphidromous Gymnogobius species potentially lasts for a few months (Dotu, 1955;Ishino, 2005;Oto, 2021).…”

Morphological characteristic and truss morphometric analysis of amphidromous goby (‘nike') (Teleostei: Gobiiformes) in Bone River, Gorontalo, Indonesia

“…Subsequently, they return to freshwater after a certain period. The goby is frequently documented as a species with amphidromous behavior such as Redigobius bikolanus (Tran et al 2018), Gymnogobius petschiliensis (Oto 2020;Oto 2021), Rhinogobius nagoyae (Iida et al 2021), and Sicyopterus lagocephalus (Teichert et al 2021). Other amphidromus goby species have also recently been reported to be recorded in Indonesian waters, such as Sicyopus auxilimentus on Sangihe Island , Sicyopus discordipinnis in Central Sulawesi (Nurjirana et al 2022a), Belobranchus segura in the south of Java (Hasan et al 2023a) and Sumatera (Hasan et al 2023b), Stiphodon surrufus (Ndobe et al 2022) and Stiphodon annieae (Gani et al 2021) in Sulawesi.…”