Different animals all over the world have different body specifications; exhibit different behavioral body characteristics, eat different types of food and even have different mating procedures. Different animals have different ways of determining their sex. Males and females of numerous classes exhibit different features for instance, the sizes of their bodies, the colors of their body, decorations as well as weaponry. In vertebrate species, sex is determined basing on unlike features on their gametal structures. This paper will focus on the different ways of determining sex in amphibians.
Currently, most researchers disregard the impact of temperatures towards the sexual patterns in amphibians. This information openly mismatches with the ancient research. However, this is considered as a larger progression in the field of research as nowadays, sex in amphibians is explained in terms genetic as well as epigenetic factors. In this case, the sexes of amphibians are going to be determined in terms of their genetic composition. The genetic composition of amphibians depends to a larger extent on the species of the amphibians. Some species of amphibians exhibit the XX/XY while some other species exhibit the ZZ/ZW (Smith & Voss 548).
Considering the genotypic sex determination in amphibians, to begin with is the cytogenetic analysis that was performed for the purpose of exposing the mismatch that existed between the sexual characteristics chromosomes. Precisely, the dissimilarity between the sex chromosomes entails the sizes of the chromosomes, the patterns of binding, the centrometric index, the heterochromatin characterization as well as the transcription loops of lampbrush chromosomes.
By any chance, the researcher discovers either an expression of an isozyme that is sex linked or an appearance of an H-Y antigen plus the inclusion of a sex-ratio progeny examination that may result into individuals who are sex reversed, and then the heterogamety of either being a male or female could have been verified to be present. However, some other articles argue out that the amphibian sex chromosomes are imperceptibly differentiated thus making the cytogenetic sex identification method totally difficult (Hofrichter 24). However, few species were incorporated when the researchers drove to this conclusion.
Sex determination among various species of amphibians can thus be determined by looking at the different in chromosome pairs such as pairs 4, 7, 8 or even 11(Smith & Voss 548). The variation in the structure of the Y or W chromosome is what brings about the difference in the sexual structures of the amphibians. This is because of the amassing of recurring sequences of the nuclear on the chromosomes. This results into reduction of the chances of These accumulations would lower the occurrence of chromosomes with similar genetic information from crossing over in the process of meiosis. This increases the discrepancy in paired chromosomes (King 322).
The morphological variations for instance, size, shape and color plus the amphibians whose behavior, physiology and demography are the different have been proven to have an effect on the on the sex determination among the organisms. For instance, one Japanese frog whose scientific name is Rana rugosa, from the North, exhibits the ZW chromosomes. From this, it can be noted that Z and W are heteromorphic thus they exhibit different morphological and genitival characteristics.
However, the three southern types reveal the XX/XY in which two of them exhibit the homomorphic X and Y. marsupial frogs (Gastrotheca pseustes) existing within the same population has two discrete male genotypes. The genotypes have dissimilar telomeric regions on the elongated Y chromosome. Considering the males of Rana narina, two heteromorphic chromosome pairs (1 and 8) are recognized to exist.
Furthermore, similar results were observed in another type of frog identified as Leiopelma hochstetteri that is found in the New Zealand. A female frog in the North Island was discovered to be carrying the most unique univalent W chromosome that had inter-individual porlymorphism. This may be written mathematically as, 2n=22+W which has a genotype of 00/W0 (Asashima 24). It is however widely known that the chromosome does not exist in the Great Barrier Island. Therefore the genetical composition on the structure of a chromosome influences the sex of an organism, whether male or female (Smith & Voss 546).
The temperature is believed to have no impact to the primary sex ratio of amphibians in the species of Xenopus laevis. However temperature has a great impact as on the hybrid forms of polyloidy. This refers to those organisms that have been bred in the laboratory. According to the research of these organisms, during the seasons of low temperatures, these organisms tend reproduce a large number of male organisms. The reverse happens when the temperatures are high. These organisms tend to produce a larger number of females than males. In spite the fact that the impact of temperature to some extent has become limited with time, it still plays a major role in determining of the sex of some species of amphibians.
To be precise, “between the fourth stage and twelve weeks of the larval development, is the period when the effect of temperature on the determination of sex is considered” (King 325). As a result of temperature, the W chromosome of amphibians could “encode a factor leading to the activation of aromatase synthesis, whereas the Y chromosome could encode a factor leading to repression of aromatase synthesis” (Asashima 23). The demerit of the effect of temperature is that the fluctuation in temperatures is not mentioned. However, temperature plays a major role in determining the sex of various amphibian species.
Works Cited
Asashima, Malacinski. “Surgical manipulation of embryos”. In: Armstrong JB, Malacinski GM. eds. Developmental Biology of the Axolotl. New York: Oxford University Press, 1989. Print.
Hofrichter, Robert. Amphibians: the world of frogs, toads, salamanders and newts. Virginia: Firefly books, 2000. Print.
King, Helen. “Studies on sex-determination in amphibians”. Journal of Experimental Zoology 12.3 (1912): 319–336. Print.
Smith, Jeremiah and Voss, Randall. “Amphibian Sex Determination: Segregation and Linkage Analysis Using Members of Tiger Salamander Species Complex.” Heredity 102 (2009): 542-548.