Keratella (spined rotifer)

Keratella spp. · Aquatic life

Under the microscope · Photo: CC0

NativeRotifer

Also called Keratella quadrata, Spined rotifer, Keratella cochlearis, Loricate rotifer

How to identify Keratella (spined rotifer)

Too small to see by eye, about 0.1 to 0.3 mm
Stiff shell (lorica) with a tiled or mosaic pattern on the back
Six spines on the front edge and zero, one or two spines at the back depending on species and form
No foot; swims with a ring of cilia at the head end
Often one of the most numerous rotifers in lab counts

Similar species

Brachionus also has a stiff shell with front spines but has a smooth back and a movable foot; Kellicottia has one very long rear spine and long, uneven front spines.

Profile

Season	Present all year, even under ice; numbers peak in spring and again in summer.
Starts	Any water temperature
Depth	Open water
How it spreads or reproduces	Females clone themselves through the season; tough resting eggs survive drying and travel on birds, wind and equipment
Habitat	Open water of nearly every pond, lake and reservoir, from clean mountain lakes to nutrient rich ponds.

Why it matters in a lake

A tiny grazer of small algae, bacteria and detritus and a key first food for newly hatched fish. Very high rotifer counts with few water fleas often point to heavy fish predation or nutrient rich water.