We have transgender among human beings. Are there transgender among animals?

K.D. Viswanathan, Coimbatore, Tamil Nadu

In animals gender identity is a sense of identification with either the male or female sex, as manifested in appearance, behavior, and other aspects of a individual’s life. It is very strong in mammals since sex is determined genetically on the basis of sex chromosomes called allosomes (X and Y chromosomes). In man the gender identity emerges by the age of two or three and is influenced by a combination of biological and sociological factors reinforced at puberty. Once established, it is generally fixed for life.

Transgender in human is the state of one's "gender identity" not matching one's "assigned sex". The transgender may be transsexual, bigendered transgender or intersexed transgender.

The transsexual humans may be trans-women or trans-men. Trans-woman is a male-to-female (MTF) transsexual. Such person is identified as male but shows female appearance and behaviors. A trans-man is a female-to-male (FTM) transsexual. Such person is identified as female but shows male appearance and behaviors. In man transsexual is considered as a syndrome caused due to allosomal anupolidy, an abnormality in the sex chromosome number.

Bigendered transgender individuals may identify with both genders, or as some combination of both. Some express their bigender identity through cross dressing others may adopt a strictly masculine or feminine appearance and experience the shift between genders on a purely mental or only subtly physical level.

An intersexedindividual has one of the many long-established biological conditions whereby a child is born with reproductive organs, genitalia and/or sex chromosomes that are not exclusively male or female. The previous word for intersex is hermaphrodite.

Many animals of lower phyla are hermaproditic animals having both sexes in them. The simpler animals like Hydra and Sponges are best examples. No advanced organism uses hermaphroditic methods. The human hermaphrodites born through genetic abnormalities or syndromes are not fertile as like hermaphroditic lower animals.

In some nematodes (Caenorhabditis elegans) there are actually two genders hermaphrodites and males. The hermaphrodites are “XX”, producing both eggs and sperm (each has an X), and self-fertilize internally (the eggs are already fertilized when they are laid). The males have only one X chromosome. They are designated as “XO”. They are produced by nondisjunction (improper movement of sex chromosomes towards the poles during cell division). Males arise at a pretty low rate normally (about 1/1000). They can mate with the hermaphrodites, and when this happens, the sperm from the male are used preferentially (more cross-progeny than self-progeny) and the next generation is 50% male (only half of the male sperm have an X).

Even though XX-female XY-male pattern of sex determination is found in Drosophila (the fruit fly) as like in human beings the primary sex determination in these animals does not involve the Y chromosome but instead is determined by the ratio of the number of X chromosomes to autosomal (nonsex) chromosomes. By examining individuals with unusual numbers of various chromosomes it has been determined that in Drosophila those with one or fewer X chromosomes per diploid autosome set develop as males while those with two or more X chromosomes develop as females. Individuals with intermediate ratios such as those with two X chromosomes and a triploid set of autosomes develop as intersexes with both male and female characteristics.

In some animals there is “within-sex polymerism”. Such animals are called multiple gendered animals. There are hundreds of fish species that have two distinct types of males. The Californian singing fish (Porichthys notatus), for instance, have one large and one small type of males. The large male defends territories and guard eggs. A large male guards a big collection of eggs laid by several females. The small males defend no territories. They dart in to fertilize eggs laid in the large male's territory. The North American bluegill sunfish (Lepomis macrochirus) has no less than three male genders, of different sizes and different colors and markings. They are the large males, medium sized feminine looking males and small ones. The large males try to repel the small ones from their territories. The females spawn readily with the small males while the large male is busy with all his chasing. The feminine looking medium sized males may be schooling with the females.

In the Russian flycatcher bird (Ficedula hypoleuca) also there are three types of males, the black and white large masculine male, black and white small male and brown feminine like male. The female-like males gain an advantage because they are in control of when to initiate a fight because of the opponent's poor sex recognition ability. The masculine male is therefore fooled into believing the feminine male is a peaceful girl.

White-throated sparrows (Zonotrichia albicollis) of Ontario have two male and two female genders (one white-striped and another one tan-striped in each sex). In both males and females the white-striped individuals are more aggressive than the tan-striped individuals. Still, they can all find mates.

Similarly the male red deer or elk (Cervus elaphus) has a secondary type of males that have no antlers. They may at times be more successful at mating.

Some reptiles have evolved the temperature method of determining the sex and the sex chromosomes are not as important. All classes other than Aves and Mammals are heterothermic. Enzymes operate at specific temperatures including the ones that determine sex. This explains clearly why sex differences take place in the heterothermic animals like reptiles. Males develop due to a series of chemical changes that once begun, result in the chemical sequences that result in the male structures. This series of reactions once started there is no going back. In reptiles, the enzymes that will bring about the initial reactions to begin the male development will only operate if the temperature is conducive to allow the enzyme that begins the male development. If it is not conducive the enzyme(s) responsible for male determinants fail to start and you go to the default sex; a female. Mammals and birds are homothermic, so this will never happen for all the enzymes have evolved to operate at a specific temperature.

Even in humans we find that there are females with XY chromosomes (very rare) that the male "startup" gene (called the sry gene found in Y chromosome) apparently did not work. The default is purely genetical not due to temperature variations as in reptiles.

S. Palaniappan

Editor, Research Journal of Biological Sciences

J.J. College of Arts and Science,

Sivapuram Post, Pudukkottai-622422

More In: Sci-Tech | Science