![]() You have to maintain colonies of many different critters (potential hosts to “sacrifice” to the parasites) to keep the life cycle going. Usually, doing lab-based experiments on parasites like the hairworms, which infect different species of hosts throughout its life cycle, is a logistical hardship. While the hairworm’s tolerance for deep freezing allows it to complete its life cycle regardless of seasonal changes, this is also a boon for scientists who study them. People become infected by this worm when consuming raw or under-cooked fish and while it would prefer infecting marine mammals, it can still cause a really nasty stomach ache or even an anaphylactic reaction. Thankfully such feats of cold tolerance are rare - deep freezing at temperature of -35☌ or colder for extended period is actually recommended as an effective way of getting rid of Anisakis simplex, a nematode parasite also known as sealworm, which is sometimes found in fish. nativa infects mammals that maintain a consistently warm body temperature, it needs to be eaten by a predator or (more likely) a scavenger to complete its life cycle, so it has to stay alive while trapped in a frozen cadaver until liberated by a potential host. During winter the wood frog simply turns into an ice block and its organs are protected from freeze injuries by chemicals like glucose and urea - perhaps the frog’s parasites have similar ways of dealing with the cold.Īnother species of roundworm, Trichinella nativa, which infects the muscles of arctic mammals such as arctic foxes and polar bears can also survive being frozen at -18☌ for up to four years and still remain viable. The hairworm is not the only parasite which can survive freezing conditions - so can some roundworms and fluke larvae that infect the wood frog Rana sylvatica. When it thaws out, it is still fully capable of infecting the next host. In fact, a recent study showed that it can tolerate being frozen at -30☌ or even -70☌ for weeks. ![]() But the hairworm Paragordius varius is not at all bothered by snow, ice and freezing conditions - it simply shrugs it all off and waits it out. ![]()
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