Frontonia acuminata (Ehrenberg, 1833) Bütschli, 1889

Kizildag, Sibel & Yildiz, Ismail, 2019, Morphology and molecular phylogeny of four Frontonia species from Turkey (Protista, Ciliophora), Zootaxa 4609 (3), pp. 548-564 : 553-554

Frontonia acuminata (Ehrenberg, 1833) Bütschli, 1889

Description of the Turkish population: Size about 70–110 × 45–70 µm, usually 80 × 60 µm when live, ratio of length to width about 3:2. When viewed from the ventral or dorsal side, outline is ovoidal with a slightly pointed posterior end, convex left side and concave right side (Figs. 3a, b, d, e; 4a–f); dorso-ventrally compressed about 3–4:1, ventral surface slightly concave in anterior part, dorsal surface distinctly convex in mid part (Fig. 3c). Single ovate macronucleus, 20–25 × 10–12 µm in size and located in anterior body part. Micronucleus 4–5 µm in diameter, usually globular, rarely elliptical in shape, and located in an indentation of the large end of the macronucleus (Figs. 3a; 4b, j, k). Single contractile vacuole with small vesicles located slightly below mid body, opens out with 2–3 excretory pores on the right margin (Figs. 3a–c, e; 4a, 4f). Extrusomes spindle-shaped, about 7–8 µm long, attached perpendicularly to the somatic cortex and forms a dense layer (Figs. 3b, 4g). Cytoplasm colorless with conspicuous dark anterior spot, food vacuoles scattered throughout the cytoplasm and filled with diatoms and filamentous algae (Figs. 3a, 4b–d). Somatic cilia about 8–10-µm-long in vivo, arranged in 40–60 longitudinally ciliary rows of kinetosomes and form sutures (preoral and postoral sutures) in the ventral midline of the cell, 4–5 postoral kineties ( Table 1 ; Figs. 3g, 4b). Preoral suture commences at the vertex of the buccal cavity and extends to the anterior pole and terminates on the dorsal side. Postoral suture extends as a line from the right posterior corner of the buccal cavity to the posterior pole and terminates on the dorsal side (Figs. 3d, e; 4e, f). Oral apparatus is triangular in shape, about 1/4 of the body length, located in the anterior body half, 4 vestibular kineties on the right of the buccal cavity. Three peniculi located of the left wall of the oral cavity, peniculi 1 and 2 composed of 5–6 and peniculus 3–4 kineties. Paroral membrane consists of 1 row of closely spaced kinetosomes, and it surrounds the right margin of the buccal cavity ( Table 1 ; Figs. 3a, d, f; 4e, i). Cells swim moderately fast for short distances and are then motionless for short periods, and rotate around the main body axis as they move.