Code IF499999

An order of small to medium-sized flatworms (0.5-1.2 mm) living as commensals on the gills or body surface of Crustacea (a few on snails or turtles). The order is restricted to Australia, New Zealand, some Pacific islands, South America, India and the Balkan Peninsula. Temnocephalida are distinctive flatworms with tentacles at the front or on the sides of the body. Some move with a leech-like motion.

There are two families, Temnocephalidae and Scutariellidae, but only the former is recorded in Australia. Williams (1980) reports 15 described and a number of undescribed species.

Specimens having 2-6 pairs of tentacles are all referable to the Temnocephalidae. Specimens having 1 pair of tentacles may be referable either to Temnocephalidae (tentacles conjoined basally; mouth opens downward) or to Scutariellidae (tentacles short, stumpy, on the fronto-lateral margins; mouth opening anteriorly between tentacles).

Other characters include the following: External body surface not ciliated except on the tentacles. Mouth anterior, opening to ventral surface. Pharynx doliiform (barrel-shaped). Gut straight, not ciliated (in Temnocephalidae often wider than it is long, in Scutariellidae longer than wide). One pair of protonephridia opening anteriorly and usually dorsally, in Temnocephalidae into vesicles. Testes compact, usually two pairs in Temnocephalidae, always one pair in Scutariellidae. Ovary single, on right side of body, with paired yolk glands.

Reference:

Williams, W.D. (1980) Australian Freshwater Life: The Invertebrates of Australian Inland Waters. The Macmillan Company of Australia, Melbourne.