From Genes to Gonads: Molecular Control Points of Reproduction in the Sea Urchin as a Framework for Aquaculture

The economic output of sea urchin aquaculture depends almost entirely on a single organ. Gonads, marketed as uni, determine value through their size, color, texture and flavor, and feed formulations have been optimized empirically for decades with limited reference to the molecular machinery governing gametogenesis, sex differentiation and gonadal maturation in echinoids. This review integrates four lines of mechanistic evidence around the adult gonad, namely developmental gene regulatory networks, sex-biased gonadal transcriptomics, germ-cell and nutritive-phagocyte biology, and endocrine, neuroendocrine and retinoid signaling, and reads them in terms of the control points connecting molecular state to production outcome. Rather than advancing a unified mechanistic model, which the current evidence does not support, each component is classified by the strength of the evidence attached to it: demonstrated in an echinoid, inferred from another taxon, plausible but untested, or hypothetical. The resulting picture is one in which descriptive resources have outpaced functional tests. Candidate sex-determination transcription factors have been identified but none have yet been directly perturbed in an echinoid, the retinoid pathway is architecturally present yet biochemically incomplete, and responses to exogenous steroids remain heterogeneous across species and protocols. Priority experimental directions are ranked by commercial return and by experimental falsifiability.