Cellular muscle growth and molecular cloning and expression of growth-related gene of Malaysian Mahseer Tor tambroides larvae fed with live and formulated feeds in indoor nursery rearing system

•Effects of three live feeds (LF) and a formulated feed (FF) on cellular muscle growth and growth-related gene expression of Tor. tambroides were evaluated.•Growth rate was significantly highest in post-larvae fed FF compared to any of the LF tested.•Increased growth rate in FF dietary treatment was mostly governed by muscle fibers hypertrophy rather than hyperplasia.•Partial nucleotide sequence MyoD and myogenin gene were cloned from T. tambroides larvae.•FF dietary treatment upregulated the mRNA expression of MyoD and myogenin genes that promote muscle growth in the T. tambroides larvae.

The influences of live and formulated feeds on growth performances, muscle fibers morphometry and muscle growth-related gene expression of Malaysian mahseer, Tor tambroides larvae were evaluated in indoor nursery rearing system. Quadruplicate groups of T. tambroides larvae (0.07 ± 0.01 g, mean ± SE) were stocked in sixteen aquaria (60 × 30 × 30 cm), randomly arranged in four dietary treatments viz. larvae fed artemia (LA), moina (LM), daphnia (LD) and formulated feed (FF) with stocking density of 34 larvae per aquarium. The larvae were fed to visually near satiation in two equal feedings per day, seven days per week for 75 days. The growth-related parameters (mean weight gain and specific growth rate) were significantly highest in treatment FF, followed by treatment LA and the lowest in treatment LD or LM. Histological observation and muscle morphometric analysis revealed that mosaic hyperplasia was observed after 50 days of the feeding trial. Hypertrophic (diameter class 50 = 40 > d ≤ 50 μm and class 60 = d > 50 μm), but not hyperplastic (diameter class ≤10 μm), muscle fibers frequencies were significantly highest in larvae fed FF compared to those fed live feeds. The entire open reading frame cDNA sequences of two important growth-related genes, myogenin and MyoD, were successfully amplified and cloned from T. tambroides larvae. The nucleotide sequences alignment using CLUSTAL W in BioEdit program of both MyoD and myogenin genes showed the sign of existence of isoforms and highly conserved with other cyprinid fishes. Real-time PCR data demonstrated that myogenin and MyoD gene expressions were significantly upregulated in larvae fed FF. The results of the present experiment concluded that the nursery rearing of T. tambroides larvae with formulated feed showed augmented muscle growth and upregulated growth-related gene expression than feeding live feeds.