Sex Determination and Trans-Sexual Specimen In Chameleons

20/09/2019

The appearance of male-like females and female-like males (transsexual specimens) is a phenomenon which is quite rare and noone has ever got deeper insight, but it is very likely more frequent nowadays than we think, especially in the widespread captive bred species.

A.
First, we need to understand what is actually "sex"?, as it has several components.

1. To be male or female, depens from the genetics, and in C. calyptratus and the whole genus Furcifer, sex has been proven to be determined by sexual chromosomes, so called heterochromosomes.

2. Based on the genetics, to be a male or female, depends from the presence/absence of the so called internal primary sexual characteristics, it means gonades (testes in males, ovaries in females) together with pertinent adjacent structures and ducts, which have the basic function of producing sexual reproductive cells, the gametocytes (ova or eggs in females and spermatocytes or spermatozoids in males), and, to produce sex-specific hormones (or better to say to produce the sex-specific ratio of hormones, as both types are necessary for both sexes, only in different mutual ratio and volume). We speak here mainly about progesterone in females and testosterone in males. The issue is, all these organs are actually developing from the same base and are analogous. So, at early stage of development, it is not clear, whether a group of cells will develop to be testes or ovaries, it is determined during the embryonic development later.


3. To be a male or female depends also from primary external sexual characteristics, the copulatory organs: hemipenis (2 in number in squamates) in males and analogous hemiclitoris (also 2) in females.

4. To be a male or female depends also from the way how the different sexes "look like" or better "appear", it means how they are physically expressed in the physical world to be perceived by sensory organs of the same and opposite sex: in chameleons, the most important aspect is the "appearance", it means size, body form, spurs, pattern, coloration, horns, casques, skin derivates, crests etc., because the main and predominant sensory organ is the eye and the main sense is vision. In other animals, also other aspects are expressed like sex-specific smell for detection by vomerolfaction or olfaction; taste, texture, sound etc. These additional ones seem to play a minor to none role in chameleons, based on current research.


5. To be a male or female depends also from how the specimens of different sex specifically behave: how they move, how they interact, how aggressive or submissive they are in certain situations, how they build a pair and how they mate etc...

B.
We need to understand now, how the sex is determined. For its determination, there are basically three groups of processes:

1. Genetic determination. It happens in the moment when the spermatocyte enters the ovum (egg-cell) and fertilizes it in the form of fusing the content of its head with the genetic material of the Nucleus of the Ovum. From that moment, the physical sex of the organism is set and can not be changed during further ontogenetic development.

2. Environmental determination. Except of genetic sex, all other aspects are influenced by environmental factors and hormones and their development depends on them in certain extent. The most important environmental factor seems to be temperature: so in absolute terms (a concrete temperature or temperature span) as well as in relative terms (diapause, temperature circadian and annual and seasonal fluctuations, peeks, flow, vicariance etc.). So, at some temperatures (as a rule lower ones), the animals tend to look more like females and at the other ones (as a rule higher ones), the appearance is more male-like. Other environmental factors (but poorly studied, so more for comprehension but not for further explanation) are the humidity, air pressure, level of oxygen in the air etc.


3. Hormonal determination. In the relation to the environmental factors or without, the produced hormones, especially those of the gonads, have a great influence on the development of the features of "appearance" and behavior.

C.
We need to understand now, how it comes that male-like females and female-like males appear.
There are mainly three simple yet complex mechanisms.

1. Incubation temperature. Regardless at what temperature you incubate the eggs, the split between sexes will be approximately 50:50. BUT depending on the incubation temperature, you can produce more male-looking animals or female-looking animals. It means, in the sample, where more female characteristics appear, some if the "females" will be in fact males and vice versa! The more you move to the extrem low or high of the still viable incubation temperature, the more this phenomenon will be expressed. There will be males that behave like females and females behaving like males. Breeders sometimes purposefully - to earn more money - produce more "males"'or "females", depending from what they sell for better price. The result of this questionably ethical behavior is, they produce partly "transsexual" specimens with no reproductive value. Often, we incubate the eggs at too high temperatures, the result is the same. Feral populations of Veileds in Florida have this same problem also, unnaturally low or high incubation temperatures lead to transsexual specimens.

2. Hormones. If there is a hormonal disbalance, caused e.g. by surgical removal of oviducts and ovaries, the original female develops male-like characteristics like high casque or even full male-like appearance!


3. Disease, mistake, malnutrition, aberration. Due to diseases, e.g. tumors of gonades, or inflammatory processes, or wrong husbandry or random mistake and aberration, strengthened nowadays by extensive inbreeding, the effects can be same as above described.

Determinate the sex of the specimens presented at the two enclosed pictures...