Navigation: Some people believe that the alignment of stars and constellations will dictate their future. For some species of newts, this couldn’t be more true as the orientation of stars and constellations help guide them every spring to their breeding pond. This enables them to successfully reproduce each year. While the stars are a helpful tool for some species, the red-spotted newt is instead able to sense the magnetic poles of the earth. Using this, they are able to sense which direction they are facing and orient themselves towards their pond. The exact mechanism that allows them to sense the magnetic field remains unknown although there are a number of hypothesizes. One hypothesis is that the geomagnetic field influences radical-pair reactions in the photoreceptors of the eyes. Special proteins called cryptochromes in the photoreceptors react to create radical pairs, which have unpaired electrons that can have differing spins influenced by the magnetic field. These reactions activate the cryptochrome to varying degrees, stimulating the retinal neurons in the eyes, creating visual cues that allow the newt to visually sense the magnetic field. This method is also believed to be used by some migratory birds.
Toxicology: red-spotted newts are coated in tetrodotoxins, a poison often found in pufferfish and is even more potent than cyanide. In large enough doses, tetrodotoxins block electrical signal in the body such as those from the brain to other organs, effectively stopping these organs from functioning. While small predators of the newt such as small rodents and snakes may experience health problems, the dosage of the toxin is too low to cause anything more than slight indigestion in humans
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Regional Variation: Upon leaving the water and going through metamorphosis, most newts of eastern North America go through a “red eft” stage where their bright orange to red colour warns predators of their distasteful poison. Newts eventually lose this colour in favour of a more drab olive. The newts on Pelee Island however, are unusual in that they skip the red eft stage altogether and are instead a dark charcoal-like colour with a dark orange underbelly which lends them the common name of black eft. One hypothesis for this difference in colour is to deter predators. When threatened, some newt species will expose their contrasting underparts as a warning of their toxins. This, known as the unken reflex, allows these species to camouflage while also able to expose warning colours when needed. While this behaviour has not been personally observed in the Pelee Island population, other populations of red-spotted newt have been recorded performing this defensive behaviour. The unken reflex may be selected for by the influx of migratory birds or introduced pheasants which may feed on brightly coloured food items. The newts become camouflaged to avoid detection and when disturbed are able to show their bright contrasting underbelly as a secondary defense.
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Sources:
Muheim, Rachel, and Miriam Liedvogel. "The Light-Dependent Magnetic Compass." Research Gate, Photobiology: The Science of Light and Life, Nov. 2015, www.researchgate.net/publication/273776387_The_Light-Dependent_Magnetic_Compass. Accessed 4 Nov. 2021. "Red-Spotted Newt." Ontario Nature, 2021, ontarionature.org/programs/community-science/reptile-amphibian-atlas/red-spotted-newt/. Accessed 4 Nov. 2021. Sinsch, Ulrich. "Orientation and Navigation in Amphibia." Taylor & Francis Online, Marine and Freshwater Behaviour and Physiology, 21 Aug. 2006, www.tandfonline.com/doi/full/10.1080/10236240600562794?scroll=top&needAccess=true. Accessed 4 Nov. 2021. |