Serranus tabacarius Serranidae , the tobaccofish, is a simultaneous hermaphrodite which belongs to a group of seabasses that exhibit a wide variety of social and mating systems. The reproductive behavior of tobaccofish is similar to other hermaphroditic seabasses, with individuals assuming sex-specific spawning behaviors that allow for the assignment of male and female roles in a mating sequence. Virtually all matings involved pairs of individuals, although streaking, an alternative male mating tactic, was observed once. Pairs engage in egg trading, where individuals divide their daily clutch into a series of sequentially released parcels and take turns releasing eggs for their partner to fertilize.

In American slang , baseball metaphors for sex are often used as euphemisms for the degree of physical intimacy achieved in sexual encounters or relationships. Among the most commonly used metaphors is the progress of a batter and base-runner in describing levels of physical intimacy generally from a heterosexual perspective. Definitions vary, but the following are typical usages of the terms: [4]. The metaphors are found variously in popular American culture, with one well-known example in the Meat Loaf song " Paradise by the Dashboard Light ", which describes a young couple " making out ", with a voice-over commentary of a portion of a baseball game, as a metaphor for the couple's activities. She's gonna give the go ahead, the inning isn't over yet for me. Baseball positions are used as a coded reference to the roles played by men who have sex with men : [7]. The sequence of "running the bases" is often regarded as a script, or pattern, for young people who are experimenting with sexual relationships.

Christopher W. Mating behavior in simultaneously hermaphroditic seabasses has been often cited as an example of cooperation among unrelated conspecifics. The predominant mating behavior in this group involves egg trading, where individuals reciprocally fertilize parcels of eggs from a partner. Egg trading has been suggested as a good example of a tit-for-tat cooperative mating strategy. Although simultaneous hermaphroditic fishes are often held up as strong examples of cooperation in mating behavior, a closer examination reveals significant sexual selection and sexual conflict between male and female roles among individuals.

Intersex occurrence in freshwater fishes was evaluated for nine river basins in the United States. The incidence of intersex was greatest in the southeastern United States, with intersex largemouth bass present at all sites in the Apalachicola, Savannah, and Pee Dee River Basins. Total mercury, trans-nonachlor, p,p'-DDE, p,p'-DDD, and total PCBs were the most commonly detected chemical contaminants at all sites, regardless of whether intersex was observed. Although the genotype of the intersex fish was not determined, the microscopic appearance of the gonads, the presence of mature sperm, and the concentrations of sex steroid hormones and vitellogenin indicate the intersex bass were males. Few reproductive endpoints differed significantly among male and intersex bass; plasma vitellogenin concentration in males was not a good indicator of intersex presence.