Entoprocta

The freshwater lophophorate species do not form a monophyletic unit, but comprise two separate phyla, the Ectoprocta (Bryozoa) and the Entoprocta (Entoprocta).

Description
Resemblance with the Ectoprocta is only superficial, while entoprocts may also be mistaken for hydroids. Within the Entoprocta, the anus is situated on the circular lophophore (originally the ventral surface of the free-living larva), and a simple protonephridial system is present. The zooids are on branched or unbranched stalks, sometimes forming stoloniferous colonies. The stalk is composed of sclerotized urn-shaped segments, and usually ends in a pad-like basal plate, which in some forms sends out lateral stolons. The tentacles can not be retracted within the zooecium, but are folded into a central depression. The stalk bends at the muscular urn-shaped segments, limiting movement to a quick flitting.

Taxonomy
All four entoproct families are marine except for the freshwater genus Urnatella Leidy (1852) belonging to the predominantly marine family Barentsiidae (synonym: Urnatellidae).

Distribution
Species usually with a wide geographical distribution, the genus Urnatella being reported from the United States and from central Europe to India.

(after Meglitsch, 1972; Wiebach and d'Hondt, 1978; Nielsen, 1982)

Kingdom Animalia
Phylum Entoprocta

Meglitsch, P.A., 1972 (1979). Invertebrate zoology. (ed. 2), Oxford University Press: 834 pp.

Nielsen, C., 1982. Entoprocta. In: Parker, S.P. [ed.], Synopsis and Classification of Living Organisms. Vol. 2. McGraw-Hill Book Company: pp. 771-772.

Wiebach, F. and d'Hondt, J.-L., 1978. Bryozoa. In: Illies, J. [ed.], Limnofauna Europaea (ed. 2). Gustav Fischer Verlag, Stuttgart, New York; Swets and Zeitlinger B.V., Amsterdam: pp. 492-493.

entoproc.jpg (Urnatella gracilis, a freshwater species)