Many species of fish, like the kobudai, are known as “sequential hermaphrodites”: they can switch sex permanently at a specific point in their lives. The majority of “sequential hermaphrodites” are known as “protogynous” (Greek for “female first”): they switch from female to male.
A hermaphrodite is an organism (plant or animal) having both male and female reproductive organs. A plant hermaphrodite, for example, has both staminate and carpellate organs. In animals such as some pulmonate and opisthobranch snails and slugs can act as either the male or female in sexual reproduction.
Clown fish begin life as males, then change into females, and kobudai do the opposite. Some species, including gobies, can change sex back and forth. The transformation may be triggered by age, size, or social status.
The threes sexes of the Pleodorina starrii algae are male, female, and a third sex that researchers call bisexual in reference to the fact that it can produce both male and female sex cells in a single genotype and exists due to normal expression of the species' genes.
Roughgarden posits that while animals come in only two sexes, many species have more than two genders. How can this be? Sex refers to the size of the gametes, and, quibbling exceptions aside, sexually reproducing species have only two types of gamete, big and small (eggs and sperm).
The split gill mushroom, Schizophyllum commune, is a species estimated to have 20,000 or more distinct sexes.
Frogs can change their sex even in pristine, pollution free settings. Past research suggested that male-to-female sex changes happening in frogs in suburban ponds may be caused by increased levels of estrogen released into the water. They found more female frogs than males in suburban areas.
Reproduction. Octopus vulgaris has individuals of both sexes. During mating, the male approaches the female, who fends him off for a while, but then accepts him. He sits next to her or mounts her, inserting the hectocotylus in her mantle cavity to pass the spermatophores.
As stated here, they don't change gender. Rabbits are one of those species whose gender is difficult to tell, especially in young animals, and therefore are regularly misidentified. Related How to tell sex and spay/neutered of rabbit?
Seahorses are not one of those animals who change their sex. The female lays the eggs and the male carries the fertilized eggs on his back. They remain male and female.
Snails called slipper limpets begin life as males, and become female as they grow. A new Smithsonian study shows that when two males are kept together and can touch one another, the larger one changes to female sooner, and the smaller one later.
In the animal kingdom, males and females often take on different roles when it comes to reproduction. Most animals take on “conventional” sex roles, where males compete for access to females, females can afford to be choosy about a partner, and then take on the majority of the parental duties in raising offspring.
Ambiguous genitalia is a rare condition in which an infant's external genitals don't appear to be clearly either male or female. In a baby with ambiguous genitalia, the genitals may be incompletely developed or the baby may have characteristics of both sexes.
Cross-Dressing Cephalopods
Cephalopods, specifically octopuses and squids, often employ a variety of gender-bending techniques when mating.
Clown fish are all born male, but that doesn't mean they simply do without female counterparts.
Squids reproduce sexually with females producing eggs and males producing sperm. Squids go through elaborate courtship displays with males passing sperm packets to the females, who then deposit hundreds of gelatinous eggs on the ocean, often in communal areas.
Octopuses do the darndest things. Like kill their mate during mating—by strangling him with three arms, according to new observations from the wild. Enterprising scientists Christine Huffard and Mike Bartick watched wild octopuses in action. They found that, for males, mating can be a dangerous game.
Slugs, starfish, and other creatures also switch gender when it works to their advantage. However, the cues that trigger the change vary from species to species.
IT is well known that sex-change in the native oyster (O. edulis) occurs at some period of its life. This mollusc apparently always begins life as a male, and may change into a female at the age of one or two years. Very little is, however, known about the change of sex afterwards.
It is possible for a female chicken to take on external characteristics of a male, a phenomenon referred to as sex reversal. (To date, spontaneous sex reversal from male to female has not been reported.)
One species of fungi, Schizophyllum commune, really shines when it comes to gender diversity. The white, fan-shaped mushroom has more than 23,000 different sexual identities, a result of widespread differentiation in the genetic locations that govern its sexual behavior.
Oral sex has been observed throughout the animal kingdom, from dolphins to primates. Bonobos have been observed to transition from a simple demonstration of affection to non-penetrative genital stimulation. Animals perform oral sex by licking, sucking or nuzzling the genitals of their partner.
Probably not. Ethical considerations preclude definitive research on the subject, but it's safe to say that human DNA has become so different from that of other animals that interbreeding would likely be impossible.