Distribution and habitat
Gallery of three unnamed marine relatives of Arachnula impatiens recently isolated by researchers. © D Bass and C Berney
Vampire amoebae are commonly found in all habitats around the globe. Most are aquatic organisms found in:
- oceans
- freshwater lakes, rivers and ponds
But some species like Arachnula impatiens can be found in soils and on moss and lichens. They still need water to live, and exist inside the very thin water film around soil particles or on the surface of plants’ leaves.
However, like many other groups of protozoa, they have evolved a way of surviving temporary dryness. When the conditions become inhospitable, they go into a resting stage:
- the cell builds a protective, spherical shell-like structure around itself called a cyst (see figure 3)
- once it is protected in the cyst, Arachnula impatiens stays inactive for days or months
- when conditions improve (eg when it rains) the cell emerges from the cyst and starts moving in search of food.
Being able to form a cyst has made it possible for many protozoa to colonize soils and allow them to survive in even the most arid environments such as deserts and the tundra.