Identifying Sexually Dimorphic Circulating MicroRNAs in Gonochoristic and Hermaphroditic Marine Fish Species

Area of Science:

• Aquatic biology
• Molecular biology
• Genomics

Background:

• Distinguishing sexes in juvenile fish is challenging, hindering aquaculture and conservation efforts.
• Current methods for fish sex determination can be invasive or impractical for live specimens.
• Molecular markers are needed for efficient and non-invasive sex identification in fish.

Purpose of the Study:

• To investigate the potential of circulating microRNAs (miRNAs) as biomarkers for sex determination in gonochoristic fish.
• To explore miRNA profiles for identifying sexual transition stages in hermaphroditic fish species.
• To identify specific miRNAs correlated with sex and sexual development in fish.

Main Methods:

• Small RNA sequencing of plasma samples from multiple fish species (European seabass, Turbot, Red drum, Blue Runner, Gilthead seabream).
• Analysis of circulating miRNA expression patterns to differentiate sexes and sexual stages.
• Bioinformatic prediction of miRNA targets involved in fish sexual development.

Main Results:

• Circulating miRNAs successfully differentiated fish species.
• Specific miRNAs (miR-21a-3p, miR-18a-3p, miR-29-1a-5p) were differentially expressed between sexes in immature and mature fish.
• miR-21a-3p and miR-125b-2/3-5p were implicated in the male-to-female transition in Gilthead seabream.
• Predicted mRNA targets included genes crucial for sexual development (wnt4, esrrb, hsd17b1).

Conclusions:

• Circulating miRNAs offer a promising, minimally invasive tool for sexing fish and monitoring sexual development.
• Identification of key miRNAs can advance aquaculture, fisheries management, and conservation strategies.
• This approach provides a novel molecular method for understanding fish reproductive biology.