Frontonia schaefferi Bullington, 1939

Pan, Xuming, Liu, Weiwei, Yi, Zhenzhen, Fan, Xinpeng, Al-Rasheid, Khaled A. S. & Lin, Xiaofeng, 2013, Studies on Three Diverse Frontonia Species (Ciliophora, Peniculida), with Brief Notes on 14 Marine or Brackish Congeners, Acta Protozoologica 52 (1), pp. 35-49 : 42-44

Frontonia schaefferi Bullington, 1939 ( Fig. 4 ; Tables 1, 2)

When this species was first described by Bullington (1939), neither the details of its living morphology, nor a clearly-outlined diagnosis was given. Hence, an improved diagnosis based on both previous and present studies is supplied here.

Improved diagnosis: Marine or brackish Frontonia , about 95–120 × 50–65 μm in vivo, elliptical or reniform with anterior end broad and posterior end slightly narrowed; small buccal field about 20% of body length; about 59–80 somatic kineties; three vestibular and five postoral kineties; peniculi 1 and 2 each with four rows, peniculus 3 with two rows; macronucleus ellipsoidal, located in central region of body; one contractile vacuole, positioned on right-dorsal side at about 3/5 distance down body length and with about eight, long collecting canals.

Description of Shenzhen population: Size in vivo about 95–100 × 50–55 μm. Elliptical or reniform in outline with anterior end broad and posterior end slightly narrowed ( Fig. 4A, B, H, I, K ). Dorsoventrally flattened about 3:2 ( Fig. 4M ). Buccal cavity small and shallow, elliptical to triangular in outline, about 20 µm × 10 µm, which corresponds to about 20% of body length ( Fig. 4J ). Cytoplasm colourless to slightly grayish, often with many small black granules (3–4 µm across) at anterior end of body ( Fig. 4A, H, I ). A few small blue crystal granules (1–3 μm in diameter) distributed randomly in cytoplasm ( Fig. 4A, H, I ). Macronucleus ellipsoidal, about 25 × 15 μm, located in body centre ( Fig. 4A ). No micronucleus observed. One contractile vacuole, about 10 µm in diameter, positioned on right-dorsal side at about three-fifths distance down body length, with about eight long collecting canals ( Fig. 4A, H ): one contractile vacuole pore located on right-ventral surface ( Fig. 4F ). Extrusomes spindle-shaped, about 5 µm long, densely arranged beneath pellicle ( Fig. 4L ), approximately 20 µm long when extruded ( Fig. 4N ). Somatic cilia approximately 6 µm long. Locomotion by crawling slowly on substrate or by swimming in water with clockwise rotation about long body axis.

General infraciliature as shown in Fig. 4E–G, O–Q . Anterior and postoral sutures conspicuous, both extending onto dorsal side ( Fig. 4E, F ). About 59 to 80 somatic kineties. Five postoral kineties with dikinetids, beginning below the oral and terminating on the postoral suture ( Fig. 4E, F ). Three vestibular kineties with densely arranged kinetosomes extending from anterior vertex of buccal cavity and terminating at postoral suture ( Fig. 4G, O ). Three conspicuous peniculi, about half of the length of the buccal cavity: peniculi 1 and 2 about equal in length, each composed of four rows of kinetosomes, about half length of buccal cavity; peniculus 3 slightly curved to right at anterior end, composed of two shorter kineties which are about equal in length ( Fig. 4G, O ). Single-rowed paroral membrane on right edge of buccal cavity running from anterior to posterior edge of buccal overture, with well-developed oral pharyngeal fibres in the buccal area ( Fig. 4G, Q ).

Comparison and remarks: Frontonia schaefferi Bullington, 1939 was originally reported by Bullington (1939) with only its infraciliature described. The Shenzhen population closely resembles that described by Bullington (1939) except for a minor difference in the body size in vivo (120 × 65 µm vs. 100 × 55 µm in Shenzhen population) which we believe is population-dependent.

Figures

Fig. 4. Frontonia schaefferi in vivo (A–C, H–N) and after protargol (E–G, O–Q) and silver nitrate (D) impregnation. A, H – ventral view of a typical individual, arrow shows the single contractile vacuole and arrowhead shows a large algal cell; B – different body shapes; C – single contractile vacuole with about 8 long collecting canals; D – part of argyrome; E, F – infraciliature in ventral and dorsal views, macronucleus, and contractile vacuole pore; G – infraciliature of the buccal area; I, K – ventral view of two individuals showing different shapes; J – buccal area, arrows show anterior suture; L – extrusomes (arrows) beneath pellicle; M – lateral view; N – extruded extrusomes; O-Q – structure of buccal region, arrow on P depicts paroral membrane, arrows on Q depict cytopharyngeal fibers. CF – cytopharyngeal fibres; CVP – contractile vacuole pore; Ma – macronucleus; P1–P3 – peniculi 1, 2, 3; PM – paroral membrane; PK – postoral kineties; VK – vestibular kineties. Scale bars:A = 40 μm, E, F = 50 μm, H, I, K, M = 70 μm.