What are hermaphrodites? Give examples Animals Hermaphrodites - Science

Definition of Hermaphrodites

A hermaphrodite is an organism that has complete or partial reproductive organs and produces gametes normally associated with both male and female sexes. Many animals do not have separate sexes. In these groups, a form of sexual reproduction occurs in which either partner can act as the "female" or "male". For example, a large number of tunicates, pulmonate snails, opisthobranch snails, earthworms, and slugs are hermaphrodites. Hermaphroditism is also found in some fish species and plants too, called monoecious or bisexual. Most hermaphroditic species show some degree of self-fertilization.

Different types of hermaphroditism include Sequential hermaphrodites, simultaneous hermaphrodites, and pseudohermaphroditism.

->Sequential hermaphrodites or dichogamy occur in species in which the individual is born as one sex, but can later change into the opposite sex. Sex can be changed only once. It is commonly seen in fish (mostly teleost fish), many gastropods, and some flowering plants.

->Simultaneous hermaphrodites are those in which the individual may possess fully functional male and female genitalia. Mostly, self-fertilization occurs. For example, banana slugs, earthworms, hamlets, mangrove killifish, etc.

->Pseudohermaphroditism occurs in spotted hyenas. The males have a penis and the females have an enlarged clitoris which is sometimes mistaken to be a penis. Their gender is difficult to determine until they reach sexual maturity. When a female spotted hyena gives birth, they pass the cub through the cervix internally, but then pass it out through the elongated clitoris.

Note: In humans, the term is used to describe an individual having both male and female organs. However, that individual may not be considered a true case of hermaphroditism since usually one of the two gonads present may not be functional.

Causes of Normally Dimorphic Hermaphrodites

In sexually dimorphic organisms, a hermaphrodite may arise because of variations in the genetic code. In humans, hermaphrodites are caused by a variety of genetic conditions. In one form, a hermaphrodite or intersex person is created when two fertilized eggs fuse together, giving the zygote two X chromosomes and one Y chromosome. Other cases of hermaphrodites are caused by the SRY gene, the gene responsible for testosterone and male genitals, being transferred to the X chromosome during meiosis, resulting in both male and female genitals.

LIST OF HERMAPHRODITE ANIMALS

Many invertebrates and a significantly smaller number of vertebrates are hermaphrodites. A hermaphrodite possesses both male and female reproductive organs during their life span. Some of these animals self-fertilize, while others require a partner. Hermaphroditism is a varied mode of reproduction that manifests differently depending on the affected species.

Snails

Most snails are hermaphrodites. The only exceptions include certain freshwater and marine species, such as apple snails and periwinkle snails. In addition to hermaphroditism, snails are also early bloomers; they are sexually mature by the time they reach a year old. The giant African land snail, Achatina fulica, is the largest species of snail on earth and is capable of laying up to 500 eggs at once. As hermaphrodites, they primarily mate with partners, but are also capable of self-fertilization in rare instances.

Echinoderms

Echinoderms are marine invertebrates. They include sea stars, sea cucumbers, sea urchins and sand dollars. Some of the most well known echinoderms are also hermaphrodites. Certain species of sea star, like the common cushion star (Asterina gibbosa), are sequential hermaphrodites -- changing gender from male to female. A cushion sea star spends its first three years as a male and the next three as a female. While sea cucumbers -- elongated, squishy echinoderms -- and sea urchins are usually divided into separate, distinct sexes, hermaphrodites can exist throughout different species.

Worms

Another class of invertebrates, worms, adds to the proliferation of hermaphroditism. Some worms can fertilize themselves, but for the most part worms need a mate to reproduce. Consider the earthworm’s mating ritual. During fertilization, earthworms join together with their heads facing opposite directions and pass sperm and eggs between themselves into a joined cocoon. Their reproductive process can occur either above or below the soil when an earthworm emits a pheromone that signals it’s ready to reproduce.

Fish

Around 21 families of fish are natural hermaphrodites. These unique hermaphroditic vertebrates include snook, clown fish, wrasse, angelfish, grouper, goby, parrot fish, sea bass and anthias. Synchronous fish, hermaphrodites that are male and female the same time, are much less common than sequential hermaphrodites. Sea bass are one example of a synchronous hermaphrodite, though they cannot self-fertilize. The more common sequential hermaphrodites include species of wrasse, which will often turn from female to male when the dominant male in their group dies.