Unusual Features

One remarkable feature of some members of the family Onychiuridae is that some male-only specialized setae on the venter of the abdomen achieve full development only several molts after sexual maturity. Their function is unknown.

Many species of Collembola, almost entirely of the families Isotomidae and Hypogastruridae, go through a period of reduced activity, wherein they develop a unique morphology, often associated with the development of heavy abdominal spines and wrinkled surface and reduced mouthparts and digestive systems. When this is associated with particular ecological conditions (most commonly drying or elevated temperature), it is termed ecomorphosis: feeding ceases and the structural changes are usually striking. The cessation of the causal conditions results in a quick molt and return to normal anatomy and activity. When these conditions are part of a regular cycle the process is called cyclomorphosis.

A number of Collembola are also capable of anhydrobiosis, that is, they can become completely dry without dying. In some (but not all) instances these animals forms small balllike capsules around themselves before entering this state. If wetted, the animal resumes normal activity in an hour or two. Recent studies with sand dune Collembola suggest that this capacity may be more widespread than currently established. Another unusual feature of Collembola is the ability of some species to live very long periods without food. This characteristic appears to be best developed in some cave forms, and in several instances animals reproduced after not being fed for 30 weeks. The longest survival was a specimen of Onychiurus, which lived over a year without food and was then accidentally killed.

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