Biomedical Ephemera, or: A Frog for Your Boils

Wild European Hamster - Cricetus cricetus

The European (or Common) Hamster is a close relative to the Golden Hamster (Mesocricetus auratus) of Turkey and Syria, which was the only species able to be successfully domesticated, at first. Unlike the golden hamster, the European hamster is considered a significant pest of cropland, though in many areas, they’re also considered endangered species, due to aggressive eradication efforts.

Like most members of their sub-order (Cricetinae), European hamsters have cheek-pouches, which extend down to their shoulders. They hoard food in times of plenty, and unlike squirrels and many other rodents of the Americas, actually keep track of where they bury or store their surpluses.

Wild Life of the World. Richard Lydekker, 1916.

Bolivian (Southern) Vizcacha - Lagidium viscacia

The vizcachas (viscachas) are the closest relatives of the Chinchillinae genus, and the five vizcacha species combined with the two chinchilla species form the Chinchillidae family.

All members of this family (aside from the Plains vizcacha) live in rocky, mountainous habitats, and are largely herbivorous. The mountains vizcachas (including the Bolivian vizcacha, also known as the "mountain chinchillas") are able to subsist off of lichens and mosses, during months where other vegetation is sparse.

While vizcacha fur is almost as thick and soft as chinchilla fur, they're larger animals, and live higher on mountains than chinchillas, and so have not been raised commercially until recently. Wild vizcachas are also hunted for their pelts, as well, but despite this, the genus Lagidum still seems to be doing fairly well for itself. None are anywhere near as endangered as chinchillas, and most are considered "Least Concern" by the IUCN.

Mountain vizcachas form the majority of the diet of the endangered Andean mountain cat (Leopardis jacobita), so despite their stable population, they are still monitored, as any dip for the species can result in serious consequences for the mountain cat.

Transactions of the Scientific Meetings of the Zoological Society of London, 1835.

Mus muscalis var. nudo plicatus. - "Rhinocerous mouse"

The rhinocerous mouse is a common mouse with a variant on the same gene that's known to cause "standard" hairless mutation (without all the wrinkles). This variant has given us a lot of insight into various aspects of the skin, as the wrinkled and hairless skin is highly susceptible to skin conditions, and they have little-to-no strong bonding between the subdermal tissues and the dermis.

Modern lab mice aside, these guys are really cool on their own - especially since they were discovered in 1854! Despite the mutation causing significant health defects (such as long nails, cysts, and glandular problems, especially with the thymus), the average life-span of rhinoceros mice is still long enough to produce several litters of offspring, each bearing the same genes and of the same mutated phenotype. The naturalist John S. Gaskoin secured several individuals of this appearance, which were living wild behind the paper mills of Maidenhead Bridge, England. When the female gave birth to a litter of pups all resembling her mutation, he remarked that unlike solitary mutations seen previously (such as albino crows, born from and producing black crows), this collection of individuals was remarkable in that it clearly demonstrated the adage "like begets like".

Bear in mind, this was before Gregor Mendel's works on heritability were "re-discovered" in the 1880s. The theories of genetics, inheritance, and parental influence on offspring appearance, especially in mutation cases, were not understood, and the adage of "like begets like" was not necessarily thought to have anything to do with the unchangeable characteristics of the parents.

John S. Gaskoin went on in a later paper to propose that "like begets like" only applied to what something was like at infancy - since these mice were all born wrinkly and nude, they gave birth to wrinkly and nude. While still far from what we know today, it was certainly a big step forward from the common assumptions of the day - for example, if a man was buffed-up and muscular when he impregnated a woman, the offspring would automatically be more muscular because of that.

But these wild-living wrinkly nudist mice, which were so obviously Mus musculus, yet so obviously completely different from normal common mice, were one of the first solid bricks in our wall of genetic knowledge, over half a century before we even started getting a grasp on the mechanics of DNA, and what makes our offspring look the way they do.

Proceedings of the Zoological Society of London. John S. Gaskoin, 1854.

Mus macleari [now Rattus macleari]- Maclear's Rat

This extinct indigenous rat of Christmas Island is thought to have been the primary population control for the local crab species, along with the also-extinct bulldog rat. Between those two rodents, and the local Christmas Island shrew (not sighted since 1908 and presumed extinct), the Christmas Island red crabs that provide a somewhat-unnerving migration spectacle, were kept at a level thought to be about one-half what they were at their height. These days, the aptly-named "yellow crazy ant" that was inadvertently introduced from Australia, has cut the red crab population by a third, but unlike Maclear's and the bulldog rat, the yellow crazy ant has no population control of its own, and may one day entirely wipe out the red crabs.

The Maclear's rat is thought to have gone extinct both due to humans killing them, and the introduction of black rats to the island, when the Challenger expedition landed there in 1876. The black rats carried a trypanosome which affected them to a mild degree, but would have wiped out any non-acclimated species that acquired it in large numbers.

Proceedings of the Scientific Meetings of the Zoological Society of London. 1887.

Rodentia. Capybaras are the largest extant rodents, and live throughout the forested and swampy parts of South America. They love water, and the name "capybara" comes from the Paraguayan Guarani word Kapiÿva, meaning "Master of the Grasses". 

The Handy Natural History. Ernest Protheroe, 1910.

Cat-squirrels. Used to refer to either red squirrel or the Easten gray squirrel, both shown here.

Squirrels are just fancy-dress rats. Trust me here...physiologically, they're basically the same. Squirrels tend to be significantly larger than black rats, but some brown rats can get up to the size of even a grey squirrel. 

Quadrupeds of North America. John James Audubon, 1851.