Source tracking of larval bacterial community of Pacific white shrimp across the developmental cycle: ecological insights for microbial management and pathogen prevention in larviculture

Health of postlarvae (as products of larviculture) of Pacific white shrimp ( Penaeus vannamei ) is critical to subsequent culture. Larval microbiota establishment has potential long-term impact on host health, but bacterial sources of larval shrimps remain largely unexplored. We investigated the larviculture cycles of two shrimp strains by utilizing 16S rRNA gene sequencing alongside mainstream microbial source-tracking tools. Our goal was to evaluate the contributions of environmental elements, feeds, and internal succession to larval bacterial community. Regardless of shrimp strains or tools, the mouth opening marked a pivotal shift in bacterial source composition of larvae, with a notable contribution from the rearing water at the beginning of mouth opening, followed by enhanced internal succession, emphasizing the critical role of early microbiota establishment. Notably, the dominance of external sources at zoea II highlights the necessity for ensuring microbial safety due to the prevalence of zoea -II syndrome at this vital stage. Source tracking of specific bacterial groups suggests regulatory timing and routes of Roseobacteraceae (with potential probiotics) and frozen Artemia as a major source of vibrios (with opportunistic pathogens). The determinism-dominated assembly of bacteria, sourced either internally or externally, highlights strong host selection. This process exhibits overall similarities in taxonomic preferences for internal succession, while differences in taxonomic preferences from external sources reflect the influence of the genetic backgrounds of shrimp strains. Our work presents the first systematic assessment on bacterial sources of P. vannamei larvae across the complete developmental cycle, providing new insights that facilitate microbial management and pathogen prevention in larviculture.