Association between Turbot (Scophthalmus maximus) Fish Phenotype and the Post-Larval Bacteriome

Abstract

Over the past decade, an increasing number of studies have emphasized the importance of the host microbiome in influencing organismal health and development. Aligned with this understanding, our study aimed to investigate the potential association between the turbot (Scophthalmus maximus) phenotypic traits and the post-larval bacteriome. Turbot post-larvae were sampled from twenty randomly selected production cycles thirty days after hatching (DAH) across multiple post-larval production batches over a three-month period (April to June). Fish were selectively sampled based on five phenotypic traits, namely, normal, large, small, malformed, and depigmented. Our results showed that small-sized post-larvae had significantly higher bacterial phylogenetic diversity in their bacterial communities than all other phenotypes. A more in-depth compositional analysis also revealed specific associations between certain bacterial taxa and fish phenotypes. For example, the genera Aliivibrio and Sulfitobacter were enriched in small-sized post-larvae, while the family Micrococcaceae were predominantly found in larger post-larvae. Furthermore, genus Exiguobacterium was linked to depigmented larvae, and genus Pantoea was more prevalent in normal post-larvae. These observations underscore the importance of further research to understand the roles of these bacterial taxa in larval growth and phenotypic differentiation. Such insights could contribute to developing microbiome modulation strategies, which may enhance turbot post-larval health and quality and improve larviculture production.

Keywords: Cytophagales flatfish; larviculture; malpigmentation; microbiome; skeletal abnormalities.

Figure 1

Ordination showing the first two axes of the principal coordinates analysis (PCoA) of ASV composition. Percentage represents the proportion of variance of each axis as calculated by its eigenvalue. Symbols are color-coded and represent samples from the different categories. Malformed: normal size fish with normal pigmentation and at least one detectable skeletal malformation; Small: small size fish with normal pigmentation with no skeletal malformation; Depigmented: normal size fish with irregular pigmentation and no skeletal malformation; Large: large size fish with normal pigmentation and no skeletal malformation; and Normal: normal size fish with normal pigmentation and no skeletal malformation. Grey symbols represent weighted average scores for ASVs. The symbol size is proportional to abundance (number of sequences reads).

Figure 2

Boxplots of diversity indices Pielou’s J (evenness), Shannon’s H’, Fisher’s alpha, and Faith’s phylogenetic diversity for each category. Maf: normal size fish with normal pigmentation and at least one detectable skeletal malformation; Sml: small size fish with normal pigmentation with no skeletal malformation; Dep: normal size fish with irregular pigmentation and no skeletal malformation; Lrg: large size fish with normal pigmentation and no skeletal malformation; and Nor: normal size fish with normal pigmentation and no skeletal malformation.

Figure 3

Stacked barplot showing the mean relative abundances of the ten most abundant orders in the dataset. Malformed: normal size fish with normal pigmentation and at least one detectable skeletal malformation; Small: small size fish with normal pigmentation with no skeletal malformation; Depigmented: normal size fish with irregular pigmentation and no skeletal malformation; Large: large size fish with normal pigmentation and no skeletal malformation; and Normal: normal size fish with normal pigmentation and no skeletal malformation.

Figure 4

Boxplots of the relative abundances of significantly enriched taxa (EMMEANS p < 0.005; Supplementary File S4). Only taxa that significantly differed in relative abundance in comparison to the Nor category were considered. Supertaxon that were considered redundant were excluded. Maf: normal size fish with normal pigmentation and at least one detectable skeletal malformation; Sml: small size fish with normal pigmentation with no skeletal malformation; Dep: normal size fish with irregular pigmentation and no skeletal malformation; Lrg: large size fish with normal pigmentation and no skeletal malformation; and Nor: normal size fish with normal pigmentation and no skeletal malformation. Y-axis is a logarithmic scale.