Airing On Sunday
October 23rd 2016
8:00 pm eastern, 7:00 pm central and 5:00 pm pacific
Tardigrada is one of several littleknown phyla of invertebrates located between the nematodes (roundworms) and the arthropods (crustacea, insects, ticks and mites). They are small, 0.2-0.5 mm in length, about the size of a dot made with a “fine” mechanical pencil. A big tardigrade can be seen with the naked eye, but the light must be just right.The word tardigrade means “slow walker” which describes their rather sluggish, clumsy movement. They use their short legs and claws to cling to a substrate and waddle along like “Water Bears” or “Moss Piglets” (Kinchin 1994). Tardigrades are very common and have been found on every continent (Mcinnes 1994). They have been recorded in every biotope: both salt and fresh water; the humidity of rain forests, the altitude of mountains, the dryness of desserts, and the isolation of remote islands and Antarctic nunatacks. All tardigrades are aquatic. They need to be in water to live, to find food, to breathe, to reproduce, and to move. There are marine, freshwater, and limno-terrestrial species. The latter are the subject of this booklet and live in the water droplets trapped in the space between the leaves of moss cushions, the thalli of lichens, and leaf litter. Here they share a micro-world with other organisms (collembola, mites, rotifers, and nematodes) and endure extreme environmental cycles from flood to drought.Tardigrades look like miniature caterpillars with five body segments and four pairs of clawed legs (Figures 1 & 2). Like “higher” animals they have digestive, excretory, and nervous systems; separate sexes; and welldeveloped muscles. Like “lower” animals, they lack respiratory and circulatory systems. Instead, they breathe through their skin or cuticle and the whole body acts as a pump to circulate fluids.