Evaluation on the potential of betaine, taurine, nucleotide and nucleoside as feeding stimulant for juvenile marble goby Oxyeleotris marmoratus through behavioural assays

Abstract

This study was conducted to evaluate the potential of betaine, taurine, inosine (INO), inosine 5 0 -monophosphate disodium (IMPÁNa 2 ), and guanosine 5 0 -monophosphate disodium (GMPÁNa 2 ) as a feeding stimulant for juvenile marble goby (Oxyeleotris marmoratus) (total length 6.6-8.5 cm) through behavioural assays using agar gel pellets. All fish were conditioned to accept agar gel pellet before the behavioural assays started. Each chemical substance was tested on 50 replicates of individual fish once, and the overall ingestion rate was calculated as the representative data. The pure agar gel pellet was totally rejected by the fish (0 % ingestion rate). Therefore, any added test substance which can significantly improve the fish ingestion of the agar gel pellet can be the potential feeding stimulant. Of all the chemical substances tested at 0.1 M concentration, the ingestion rates of both INO and IMPÁNa 2 were the highest (both 100 %) and were significantly higher (P \ 0.05) than those of the other chemical substances tested. However, INO was identified as the most potent feeding stimulant as it could function perfectly (100 %) even at the lower concentrations tested (0.01 and 0.001 M). The ingestion rates of IMPÁNa 2 were found significantly decreased (P \ 0.05) at the concentrations of 0.01 and 0.001 M (78 and 2 %, respectively). The ingestion rate of GMPÁNa 2 at 0.1 M was 60 %, hence higher concentration ([0.1 M) may be required to improve its efficiency as the feeding stimulant. Taurine was not a feeding stimulant, and betaine was neither a feeding stimulant nor feed enhancer for the juvenile O. marmoratus.

The taste system in fishes and the effects of environmental variables

“…Thereafter, electrophysiological approaches have become common, especially in the 1970s–1990s and are still commonly used in studies of fish gustation (Caprio, ; Caprio et al, ; Hara, ; Yamashita et al, ). Various behavioural methods that are used for investigation of taste perception in birds and mammals have more recently become popular for use in fishes (Adams et al, ; Aihara et al, ; Appelbaum, ; Hidaka, ; Jones, ; Kasumyan & Døving, ; Lamb & Finger, ; Lim et al ., , ; Mackie et al, ; Mearns et al, ; Oike et al, ). Modern immunological and molecular biology approaches have been used to elucidate of the function of taste receptors and peripheral coding of taste and transduction mechanisms (Kirino et al, ; Liman et al, ).…”

Remarkably high ingestion ratio of acidic food in juvenile marble goby, Oxyeleotris marmorata

“…Subsequently, the mixture was poured into a glass petri dish for cooling and hardening. The hardened mixture were then cut into uniform pellet size (approximately 2 mm 9 2 mm 9 2 mm) and stored in a refrigerator (4°C) until further use (Lim et al 2015(Lim et al , 2016(Lim et al , 2017. For preparing the FT pellet, the distilled water was replaced by the commercial pellet (Otohime EP3) extract.…”

“…Before the behavioral test started, all the fish were conditioned to accept agar gel pellet using the FT pellet. The fish conditioning protocol was the same as described by Lim et al (2016Lim et al ( , 2017. Each individual of fish was conditioned once daily at 04:00 p.m. with three pieces of FT pellet.…”

“…The procedures of the behavioral test used in the present study were adopted from Lim et al (2016Lim et al ( , 2017. The test was started at 04:00 p.m. daily.…”

“…For these reasons, there is a need to find way to improve the acceptability of formulated feeds to O. marmorata. In the previous studies, amino acids mixture and nucleotides were reported as the suitable feeding stimulant through behavioural assays (Lim et al 2015(Lim et al , 2016(Lim et al , 2017 and dietary supplementation of these taste substances can be practiced to improve the weaning of O. marmorata (Lai et al in press). However, amino acid mixture and nucleotides are expensive and supplementation of these taste substances in the practical diet for O. marmorata may not be cost-effective.…”