The snapping shrimp Alpheus is the genus with most species in the Alpheidae family. In this study, the mitochondrial genome of Alpheus brevicristatus De Haan, 1844 has been sequenced and analyzed. The circular mitogenome was 15,705 bp in length with an A+T content of 62.64%. It contained 37 genes typically found in metazoans, and one non-coding region. Phylogenetic analysis highly supported the placement of A. brevicristatus within Alpheidae. This study provides important mitochondrial genome data that could be used for further phylogenetic and evolutionary study of caridean snapping shrimps.

Based on multi-seasonal surveys (2020–2022) in Beihai Silver Beach, this study examined phytoplankton community dynamics and environmental drivers. Results showed persistent diatom dominance, with Skeletonema costatum as the predominant species and a major bloom in autumn 2021. Species richness peaked in summer and was lowest in winter, while abundance hotspots were associated with the Fengjia River estuary. Generalized Additive Models identified reactive phosphate as the primary driver, exhibiting nonlinear relationships with species richness (R² = 0.91) and diversity (R² = 0.436). Dissolved oxygen also had significant nonlinear effects. A counterintuitive positive correlation between lead concentration and species richness highlighted complex stressor interactions. This study emphasizes phosphorus control for eutrophication mitigation and demonstrates GAMs’ utility in detecting nonlinear ecological responses, supporting science-based management of coastal ecosystems.

Candidatus Hepatincolaceae is a poorly characterized family of obligate Alphaproteobacterial symbionts that are widely detected in ecdysozoans. They were previously assumed to play a nutrient-scavenging role in the gut lumen. In this study, two high-quality metagenome-assembled genomes (MAGs, 1.39 Mb and 1.48 Mb in size) were recovered from the gut of the snapping shrimp Alpheus brevicristatus via metagenomic sequencing. Phylogenetic and whole-genome similarity analyses confirm that these two MAGs represent two novel, undescribed genera within the family Ca. Hepatincolaceae. Metabolic reconstruction reveals that they not only retain the canonical nutrient-scavenging pathways conserved across all Hepatincolaceae members, but also encode previously undocumented functional modules for antioxidant defense, vitamin B₁ and B₂ biosynthesis, and short-chain fatty acid production. They maintain a high oxygen-affinity cytochrome bd terminal oxidase to thrive in the anoxic gut microenvironment. Consistent with their symbiotic lifestyle, their genomes exhibit typical signatures of reductive evolution, such as reduced genome size, low GC content, and gene loss in amino acid and nucleotide de novo biosynthesis pathways. This study presents the first reported high-quality genomes of marine Ca. Hepatincolaceae symbionts, which are predicted to possess multiple metabolic functions extending beyond nutritional mutualism.