This study identified the bacterial community composition associated with Barbour's seahorses (Hippocampus barbouri). Seahorses and samples from the surrounding environment (sediment and water) were collected from Cantiasay Island in Surigao del Norte, Philippines. Genomic DNA was isolated from these samples, and the V1–V3 region of the 16S rRNA gene was amplified and sequenced on the Illumina MiSeq platform. There were 929 803 sequence reads corresponding to 859 operational taxonomic units (OTUs), which were obtained from the six genomic libraries. The results showed that the most abundant OTUs were affiliated to the phylum Proteobacteria, particularly those belonging to the genera Shewanella, Pseudomonas, Acinetobacter and Aeromonas, which were found to be dominant in seahorse gut samples. The only exception was for the skin of male seahorses, which was dominated by members belonging to the genus Bacillus (phylum Firmicutes). These findings on bacterial community structure and composition may shed light on therapeutic claims of Barbour's seahorses and help in the conservation of this species.
Mitochondrial DNA signatures based on the control region and 12S rRNA gene were used to assess the impact of conservation measures on the effective management of vulnerable Syngnathiformes (seahorses, pipefishes, and allies) species. Results from phylogenetic inference, polymorphism, neutrality indices, haplotype networks and microhabitat information may justify the establishment of distinct management units for different species. For smooth seahorses, Hippocampus kuda was identified as a species complex that formed three clusters with 20 haplotypes. Based on molecular data, these are the first records of Hippocampus capensis and Hippocampus casscsio in the Philippines. High haplotype diversity (h = 28; Hd = 0.943), yet low nucleotide diversity (Pi:0.18095) for polymorphism, suggests minor differences among haplotypes. Neutrality indices calculated using Tajima's D (−2.00774), with P < 0.05 and Fu's Fs (−11.645), were significant. However, both tests were negative, a signature of rapid population expansion from a small effective population size, which could be attributed to past heavy harvests and habitat destruction, as supported by local data. For pipefishes and their allies, there was high haplotype diversity (h = 22; Hd = 0.875) and low nucleotide diversity of Pi: 0.16671. However, neutrality indices calculated using Tajima's D (−1.68518) and Fu's Fs (11.549) were not significant, with P > 0.05, indicating a balancing selection for this population. Results reveal that the recent population expansion of seahorses proves that current conservation measures are effectively safeguarding populations, while balancing selection is maintaining genetic polymorphism in pipefishes and their relatives, making them resilient to changing environments. Moreover, as revealed by haplotype networks, intraspecific variation suggests distinct management for different species. In addition, underwater surveys show an essential association between microhabitats and species' survival, thus encouraging future initiatives regarding habitat protection, especially coral reefs, seagrass beds, sponge gardens, mangrove areas and estuaries.
Although several studies have described the bacterial community composition associated with marine fish, there is limited information related to seahorses. Moreover, previous studies have demonstrated that the skin microbiota is useful for determining health status and common disorders in the host. This study, therefore, aimed to explore the skin bacterial community composition in Barbour’s seahorse (Hippocampus barbouri) using high-throughput sequencing of 16S ribosomal RNA genes. Water and sediment samples from the surrounding environment were also analyzed for comparative purposes. The results revealed that sequences affiliated with the Shewanellaceae family were dominant in the skin of female Barbour’s seahorses and sediment samples, whereas sequences affiliated with the Bacillaceae family were dominant in the skin of male Barbour’s seahorses. Interestingly, sequences affiliated with the Aeromonas genus were found in the skin of Barbour’s seahorses, whose abundance was slightly similar between the female and male specimens. Further comparative analysis showed that the presence of Aeromonas species in the skin of Barbour’s seahorses was strongly influenced by the surrounding sediment. Given that some Aeromonas species are known to be important pathogens in humans and fish, these results may be used for further research on the dependency of the skin microbial composition on the environment as well as determine whether the presence of Aeromonas and other detected species has implications on seahorse health.
In this study, taxonomic classi cation of intestinal microbiota from healthy Barbour's seahorses (Hippocampus barbouri) was determined as it plays an important role in host nutrition and immunity. Genomic DNA was extracted from the intestinal mucus samples of eleven Barbour's seahorses, which were subjected to high-throughput sequencing of bacterial 16S rRNA genes targeting V1-V3 regions. The results revealed that the most abundant operational taxonomic units (OTUs) were a liated to the genus Shewanella. Our ndings may provide baseline data for further studies in order to explore the potential implications of intestinal microbiota to seahorses in terms of health status, development, growth, and survival.
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