Sex Determination: Northern green frogs can change their sex! Traditionally, chromosomes determine the sex of most animals, this is true of green frogs with two X chromosomes causing the body to develop ovaries and become female while an X and Y chromosome cause testes to form, creating a male frog. What’s been found however is that sex in green frogs can change in natural environments free of certain chemicals like Atrazine which is known to effect frog development. Some frogs with two X chromosomes were found to instead develop testes and an otherwise male exterior while some with an X and Y chromosome were developing into female frogs instead of males. It’s believed that this sex-reversal occurs when they are still developing, in their tadpole phase and in some populations, can occurs in up to 10% of individuals. The cause of this is not yet fully understood but could be due to temperature, nutrient availability or perhaps it’s more of a personal choice, which is valid.
Colour and Morphs: Axanthism Axanthic frogs appear blue due to a pigment mutation where they are unable to produce yellow pigment. Green frogs traditionally get their green colour from mixing blue and yellow. For blue, green frogs have iridophores in their skin, minute structures that reflect a blue wavelength of light. Producing blue pigment takes up a large amount of energy and many animals avoid this by reflecting the blue light instead, a process similar to iridescence. Without the yellow pigment, only the blue remains visible in axanthic individuals. This unusual colouration may make them to be more detectable to predators, leading to a higher mortality rate. Thus creating challenges when determining the frequency of this particular mutation in different populations.
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Colour and Morphs: Heterochromia Northern green frog have been known to display heterochromia. Heterochromia is a pigment irregularity mainly effecting the colour of the eye and often manifests as one iris being a different colour than the other. This can be caused by either mosaicism or chimerism. Chimerism occurs when two fertilized zygotes, each with their own unique genes, fuse together during early development. The resulting organism displays the genes from either zygote on different sides of the body, usually split down the middle. In contrast, mosaicism can occur when different cells in the body contain different colour mutations, this occurs after being a zygote and can cause uneven distributions of these mutations. While these developmental anomalies can cause Heterochromia, other factors such as disease and injury can also cause similar symptoms.
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Sources:
Folse, Harmony. "What Causes Heterochromia." The Tech Interactive, Stanford University, 24 Sept. 2018, genetics.thetech.org/ask-a-geneticist/heterochromia. Accessed 4 Nov. 2021. "Green Frog." Ontario Nature, 2021, ontarionature.org/programs/community-science/reptile-amphibian-atlas/green-frog/. Accessed 4 Nov. 2021. Lindemann, Scott B., et al. "Axanthism in Green Frogs (Lithobates clamitans) and an American Bullfrog (Lithobates catesbeianus) in Maine." The Canadian Field-Naturalist, 19 Dec. 2019, file:///C:/Users/Mac/Downloads/2285-Article%20Text-10311-1-10-20200226.pdf. Accessed 20 Jan. 2023 Main, Douglas. "Healthy Frogs can Mysteriously Reverse their Sex." National Geographic, 21 Mar. 2019, www.nationalgeographic.com/animals/article/frogs-reverse-sex-more-often-than-thought?cmpid=org=ngp::mc=social::src=facebook::cmp=editorial::add=fb20190321animals-frogsexreversal::rid=&sf209705. Accessed 4 Nov. 2021. |