Comparative Studies on a New Brackish Water Euplotes, E. parawoodruffi n. sp., and a Redescription of Euplotes woodruffiGaw, 1939 (Ciliophora; Hypotrichida)

The morphology, nuclear apparatus, infraciliature, and silverline system of two populations of the Euplotes woodruffi-complex, one from brackish water off Pamlico Sound, North Carolina (USA), and the other from a freshwater pond in Qingdao (P.R. China), have been examined in vivo and with silver nitrate and protargol impregnations. A comparison of the two forms reveals marked differences in structure sufficient to separate the two morphotypes into two species. Euplotes parawoodruffi n. sp. (syngen 1 of E. woodruffi) is characterized by a strongly arched dorsum, regular double-eurystomas type silverline system, an adoral zone of ca. 80 membranelles extending over 4/5 of the cell length; 9 frontoventral, 2 marginal, and 2 caudal cirri; marine/brackish biotope; macronucleus irregularly T-shaped. Its T-shaped macronucleus with a short right arm differs from that of E. woodruffi, in which the right arm is longer than the left. The general body shape of E. parawoodruffi, broad anteriorly and tapering posteriad, differs from the ovoid shape of E. woodruffi. Its domed dorsum without longitudinal grooves differs from the flattened dorsum with shallow grooves of E. woodruffi. The presence of a longer AZM formed of consistently more membranelles and the absence of a pre-oral pouch (an invagination on the dorsal wall of the buccal field anterior to the cytostome, always present in E. woodruffi) further separates E. parawoodruffi from the latter.