A study of brown lanternsharks in Suruga Bay by Yano and Tanaka (1989) found a 23% prevalence of hermaphroditism within the population.
Clinically exploring 'a richly diversified collection of erotic endowments and inclinations: hermaphroditism, pedophilia, sodomy, fetishism, exhibitionism, sadism, masochism, coprophilia, necrophilia' among them, Freud concluded that 'all humans are innately perverse'.
True synchronous hermaphroditism with external fertilization is known in Evermannella indica and Odontostomops normalops, and the former species appears to spawn throughout the year.