The influence of natural versus artificial seawater on larval development in Macrobrachium rosenbergii: A perspective based on water-larva microbiota interactions

The giant river prawn ( Macrobrachium rosenbergii ) requires saline water for larval rearing, yet artificial seawater (AS) often underperforms compared to natural seawater (NS). This study investigated how AS and NS influence larval development through water-larva microbial interactions. Larvae were reared in parallel AS and NS systems, with growth performance and microbiota (water and whole-larva samples) analyzed via 16S rRNA sequencing and network analysis. Although larval survival and metamorphosis rates were numerically lower in AS than NS, differences were not statistically significant. Alpha diversity indices did not differ significantly between treatments in either water or larvae. However, beta diversity analysis revealed significant structural divergence in water communities ( p < 0.05), while larval communities remained overall similar ( p > 0.05). Despite this structural stability, AS-reared larvae exhibited relatively higher abundances of potential pathogens like Acinetobacter . Crucially, co-occurrence network analysis showed that AS fostered destabilized microbial networks centered on opportunistic genera, whereas NS maintained stable networks dominated by beneficial taxa. We conclude that AS's inferior performance trend is associated with disrupted water microbial structures and unstable larval-associated microbial networks, potentially facilitating pathogen proliferation. These findings highlight the critical role of microbial network stability—not just diversity or abundance—in larval health and provide a basis for optimizing AS formulations to support sustainable prawn aquaculture. • Artificial seawater reduced larval survival and metamorphosis in M. rosenbergii . • Microbial diversity decreased and pathogens increased in artificial seawater. • Larval gut microbiota showed more conditional pathogens in artificial seawater. • Microbial networks differed between artificial and natural seawater systems. • Water-gut microbiota interaction shaped larval development in artificial seawater.