The Pacific seahorse Hippocampus ingens is an economically important species in the Pacific coast of Mexico. Aquaculture represents a viable alternative to reduce the impact of fisheries on the natural populations of H. ingens. However, in order to improve and optimize the culture protocols and ecological relationships, an important step is to describe their associated microbiota.
To achieve this goal is essential to determine which microbial organisms conform the microbiota in healthy sea horses and which bacterial organisms can harm them. We were able to access H. ingens juveniles from a commercial producer (INGENS Cultivos Marinos) in Mazatlán, Mexico, in three health statuses: i) healthy (normal swimming and feeding activity), ii) disease (lethargic, non-feeding, and mostly in the bottom of the tank), and iii) post-disease (recovered from the disease stage). Five individuals were selected for each condition and euthanized with an overdose of anesthetic solution (4% phenoxyethanol). Individuals in every heath status were dissected in two main sections: cephalic and body (in the body section the digestive tract was dissected and analysed).
Cephalic and body sections from each health status were pooled and labeled as: cephalic healthy individuals (HCH); body healthy individuals (HBH); cephalic disease individuals (HCD); body disease individuals (HBD); cephalic post-disease individuals (HCpD); and body post-disease individuals (HBpD). Every pool was processed for total DNA extraction and the resulting extracted nucleic acids were sequenced for 16S rDNA V3 region. From all samples sequenced we kept 443854 high-quality paired-end-assembled reads and analyzed only those 415860 reads assigned to bacteria, based on the 16S ribosomal RNA. We determine the bacterial diversity, richness, and evenness in the hippocampus bacterial communities related to each condition (healthy, disease, and post-disease) and body section through rarefaction (interpolation) and extrapolation (R/E) sampling curves analysis.
The results showed differences related with the health status in two main groups: healthy (HCH, HBD) and disease related (HCD, HBD, HCpD , and HBpD). The rarefaction (interpolation) and extrapolation (R/E) sampling curve analysis showed a possible effect of health status over the bacterial community structures of the juveniles. The dominant phylum in samples from healthy sea horses was Cyanobacteria (49.6% - 54.8%). T he dominant phylum for disease-related samples was Proteobacteria exhibiting a distribution from 61.5% to 85.4% .
The structural differences in the bacterial c ommunity between healthy and disease-related seahorses strongly suggest a direct effect of health status over a differential bacterial proliferation. However, more studies are required to determine how bacterial organisms are directly related to the health status of the Pacific seahorse juveniles