Ovotestis

An ovotestis is a gonad with both testicular and ovarian aspects.^[1][2] In humans, ovotestes are an infrequent anatomical variation associated with gonadal dysgenesis.^[3] The only mammals where ovotestes are not symptomatic of a disorder are moles, wherein females possess ovotestes along with a masculinized clitoris. These ovotestes in nonpregnant female moles secrete eight times as much testosterone as the ovotestes of pregnant moles.^[4] In invertebrates that are normally hermaphroditic, such as most gastropods (snails and slugs) in the clade Eupulmonata, an ovotestis is a common feature of the reproductive anatomy.

In mice, ovotestes are structured such that the central region is testicular tissue while the poles both contain ovarian tissue. Experiments involving the SOX9 gene, which is initiated by the SRY region of the Y chromosome, have shown the gene's requirement for testicular differentiation from the presence of ovotestis formation within XX Sox9 trangenic mice. (6) Ovotestis within B6-XYPOS mice allow for gonadal development research within the same tissue to take place in ways previously unavailable.^[5][6]