Some records of tardigrades in Yorkshire

摘要

Tardigrades, sometimes known as water bears, are microscopic animals 0.1mm-1.5mm long, usually transparent and with four pairs of stumpy legs (See Plate II, centre pages). They are to be found in marine, freshwater and terrestrial environments.Tardigrades were included in the phylum Arthropoda prior to 1962 but since that date they have been allocated their own phylum - the Tardigrada (Ramazzotti, 1962). The phylum is split into two Classes, the Heterotardigrada and the Eutardigrada. The former is broken down into two Orders, the Arthrotardigrada, which includes all the typical marine species, and the Echiniscoida which, with one exception, are from terrestrial environments. The exception Echiniscoides sigismundi is to be found on some species of marine algae and within some barnacles and mussels. This Order also includes Echiniscus, a genus whose species are covered with sclerotized plates and distinctive cirri. The Class Eutardigrada comprises typical terrestrial species which lack the sclerotized plates, having an elastic, transparent cuticle.