Document Type


Publication Date

Spring 5-14-1958


The primary purpose of this investigation was to establish the probable number of ecdyses in the life history Macrobiotus islandicus Richters under natural conditions. An Isolated patch of moss taken from the Colorado montane zone yielded 800 individuals of Macrobiotus islandicus which were induced to undergo asphyxy by allowing them to remain In water for at least 24. hours. In this condition the tardigrades became completely extended and could be accurately measured after mounting in glycerin. Body length and buccal apparatus length were measured and length—frequency curves constructed. Each curve showed a series of high and low points; each peak represented an instar and each low point corresponded to an ecdysis. Six such ecdyses were suggested. The correlation coefficient between length of buccal apparatus and body length was shown to be very high. Eleven Individuals In the population were positively shown to be in the process of molting at the moment they were killed; their lengths correlated precisely with the suggested points of ecdysis in the curves. Colorado tardígrades found in this investigation included: Macrobiotus islandicus Richters, Hypsibius granulifer (Thulin), and Echiniscus granulatus (Doyére) (all new to North America); Macrobiotus harmsworthi J. Murray, Hypsibius scoticus (J. Murray), and H. tuberculatus (Plate) (new to the United States); Macrobiotus hufelandi S. Sohultze and Milnesium tardigradum Doyere (previously reported from this country).