Bdelloid Rotifer Fauna of Germany and adjoining countries: Habrotrocha annulata Murray 1905, Habrotrochidae/ Bdelloidea/ Rotifera/ Syndermata.

Habrotrocha cf. annulata Murray 1905

Habrotrocha cf. annulata, two specimens whirling in the lobules of the liverwort Frullania dilatata.

Habrotrocha cf. annulata, the right specimen from the above image, dorsoventral view.

Habrotrocha cf. annulata, head of the left specimen from the above image. The characteristic plication of the ventral side of the head and neck is visible.

Habrotrocha cf. annulata, dorsal view of a whirling specimen.

Original text of Murray (TRANS. ROY. SOC. EDIN., VOL. XII. PART II. (NO. 15).1905:

"Specific characters. —Small, colourless, in lateral view pitcher-shaped, the lower hip spout-like. Dises inclined towards mouth, their surfaces parallel to long axis of body.
Oral segment much elongated, marked by annular plicae, which are stronger towards the base. First neck segment with similar plica. Antenna very small, its length equal to of the diameter of the neck. Teeth, seven or eight in each jaw. Food moulded into pellets. Foot short, of three joints.
Spurs, short cones, meeting at base. Reproduction oviparous.
General description.— Length about 1/100 inch when feeding. Oral segment twice as long as broad. Discs reniform, separated by very narrow sulens. Neck and gullet very long. Rostrum short and broad, with small lamellae. Stomach large, nearly filling the trunk, containing clear rounded pellets of uniform size.
Resembling C. angusticollis in size and general form, it may be easily distinguished from that species by the smaller lower lip, greater forward inclination of the discs, longer oral segment, with annular pliere and without thickenings, numerous teeth, larger foot, and lack of protecting case. Some examples carried large oval eggs. Intestine, glands, and vibratile tags were not observed.
Habits.—Being unable to secrete a case for itself, as is done by C. eremita and other species, it seeks shelter, like the hermit crab, in the empty shells of other animals.
Shells of Difflugia, Nebela, and other Rhizopods are commonly occupied. It was first observed in cases of C. angusticollis, the original occupants of which had died, leaving only the tough jaws behind. The presence of those jaws, with their pairs of teeth, led to the two species being confused for some time. It also frequently takes cover in the pitchers of Frullania and other Hepatics. It is often found creeping about without protection of any sort, but it has never been seen to feed unless when in a shelter of some kind. When feeding it is not timid. It may frequently be observed, in detached pitchers of Frullania, whirling rapidly about, regardless of collisions.
Habitat.— Among aquatic mosses growing in Loch Morar, October 1903, Loch Ness, 1904. Not confined to lakes. Common on Hepatics, Fort-Augustus, Blantyre Moor."