A histological description of shortspine thornyhead, Sebastolobus alascanus, ovaries: structures associated with the production of gelatinous egg masses

The ovarian structure of the shortspine thornyhead, Sebastolobus alascanus (Scorpaeniformes), which is similar to the ovarian structure previously described only for the pigmy lion fish, Dendrochirus brachypterus (Scorpaeniformes), is specialized for the production and expulsion of pelagic gelatinous egg masses. The germinative tissue and oocytes of S. alascanus encircle a mass of spongy stroma that is located within the center of the ovary. The stroma is attached to the ovary wall only at the anterior end of each ovarian lobe; hence, the ovarian lumen surrounds the stroma, germinative tissue, and oocytes. Secondary oocyte development takes place on the ends of vascularized peduncles that are protrusions of the ovarian stroma. A gelatinous material is simultaneously secreted into the ovarian lumen by a single row of specialized cells that line the ovary wall. Eggs detach from peduncles and ovulate into the gelatinous material.