Gut microbiota and metabolic function in leeches with distinct feeding niches

Background The gut microbiota has co-evolved with its host and plays a vital role in maintaining physiological homeostasis and health. Understanding the composition of microbial communities in leech guts may reveal important insights into their ecological adaptations and feeding strategies. Objective This study aimed to compare the gut microbiota of hematophagous (blood-feeding) and non-hematophagous leeches, to identify microbial signatures associated with dietary divergence and niche specialization. Methods Gut contents were collected from representative species of hematophagous and non-hematophagous leeches. Microbial community composition was analyzed via 16S rRNA gene sequencing. Results A total of 751 microbial species were identified, encompassing 535 genera, 332 families, 203 orders, 86 classes, and 39 phyla. At the phylum level, Proteobacteria and Firmicutes were significantly higher relative more abundant in hematophagous leeches, whereas Bacteroidetes predominated in non-hematophagous counterparts. At the genus level, hematophagous leeches exhibited higher abundances of Elstera , norank_f__Rhodospirillaceae, Aeromonas , f__Rhodospirillales, o__Peptostreptococcales-Tissierellales, and unclassified_o__Oscillospirales. In contrast, unclassified_f__Comamonadaceae, Nubsella , Cetobacterium , Mucispirillum , norank_f__Peptostreptococcaceae, and Bacteroides were enriched in non-hematophagous leeches. Functional prediction analysis revealed significant differences in five key metabolic pathways between the two groups: lipid transport and metabolism, amino acid transport and metabolism, nucleotide transport and metabolism, translation and ribosomal structure biogenesis, and coenzyme transport and metabolism. Conclusion Distinct taxonomic and functional profiles characterize the gut microbiota of hematophagous and non-hematophagous leeches. These results provide microbiological evidence for dietary specialization in leeches and offer a scientific basis for guiding domestication and artificial breeding strategies.