Frontonia guangdongensis, Pan & Liu & Yi & Fan & Al-Rasheid & Lin, 2013

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 : 36-39

Frontonia guangdongensis spec. nov. ( Fig. 1 ; Tables 1, 2)

Diagnosis: Brackish water Frontonia , about 160 × 35 μm in vivo, elongated body shape with right margin depressed in anterior third of body; length to width ratio about 4:1 to 5:1; small buccal field about 10 to 12% of body length; 62–75 somatic kineties; three or four vestibular kineties, four or five postoral kineties; peniculi 1 and 2 each with four rows, peniculus 3 with two rows; macronucleus ellipsoidal and located in central region of body; one contractile vacuole in mid-body region right of cell median.

Type locality: A coastal shrimp-culturing area in Nansha (23°43′N, 113°33′E), Guangdong province .

Deposition of type slides: One slide containing the holotype (registration no. LWW-08110901-01) and several paratype slides (registration no. LWW-08110901-02) with protargol-impregnated specimens are deposited in the Laboratory of Protozoology , Ocean University of China, China .

Etymology: The species name ‘ guangdongensis ’ refers to the location where this organism was first isolated.

Description: Cell in vivo distinctly elongate, usually about 150–170 × 35–40 μm, with ratio of length to width about 4:1 to 5:1 ( Fig. 1A, H ). Right margin slightly depressed in anterior third of body ( Fig. 1A, B, H, I ). Dorsoventrally flattened about 5:4. Buccal cavity small and shallow, elliptical to triangular in outline, about 20 × 11 µm in size, 10 to 12% of body length ( Fig. 1G ). Cytoplasm grayish with many large (6–10 µm across), black, polygonal crystal granules. Food vacuoles (10– 12 µm across) and ingested algae distributed randomly in cytoplasm ( Fig. 1A, K ). Macronucleus ellipsoidal, about 20 μm × 15 μm, located in mid-region of body ( Fig. 1A, O ). Single micronucleus located near end of macronucleus, spherical, about 5 µm in diameter ( Fig. 1O ). Single contractile vacuole in mid-body region right of cell median, about 7 μm in diameter, contracting at about one minute intervals ( Fig. 1A, K ); no collecting canals observed; one contractile vacuole pore located on right-dorsal surface ( Fig. 1F ). Two types of extrusomes, spindle (about 8 µm long) and round (2 µm across), densely arranged beneath pellicle ( Fig. 1C, D, M ); somatic cilia generally about 6 µm long, cilia in caudal region being longer than others at approximately 10 µm long ( Fig. 1M ). Locomotion by gliding on substrate or by swimming while rotating about long body axis.

Somatic ciliature as shown in Fig. 1E, F, G, P–T . About 52 to 65 longitudinal somatic kineties, commencing at anterior end of cell, forming a conspicuous anterior suture that extends from anterior end of buccal cavity to dorsal side ( Fig. 1E, F, P, S ); posterior part of somatic kineties terminating below posterior region of oral apparatus forming the postoral suture ( Fig. 1G, Q, T ). Three to four vestibular kineties with close-set dikinetids ( Fig. 1G, R ). Four or five postoral kineties left of postoral suture, beginning anteriorly below buccal cavity and gradually shortening from left to right ( Fig. 1G, R ).

Buccal apparatus as shown in Fig. 1G, N, R . Three conspicuous peniculi (P1–3) located on left wall of shallow buccal cavity, slightly curved to right at anterior end. Peniculi 1 and 2 about equally long, parallel to each other, and each composed of four rows of kinetosomes. Peniculus 3 composed of two kineties, right one of which extends entire length of buccal cavity, left one extending only to about anterior 4/5 of cavity length ( Fig. 1G, N ). Double-rowed paroral membrane on right side of buccal cavity: inner row composed of densely arranged monokinetids, outer row composed of loosely arranged dikinetids ( Fig. 1G, R ).

Comparison and remarks: There are three species that closely resemble Frontonia guangdongensis spec. nov. in terms of the conspicuously elongated body shape: F. mengi Fan, 2011 , F. pallida Czapik, 1979 and F. microstoma Kahl, 1931 .

Frontonia mengi differs from F. guangdongensis in three respects. Firstly, its body size in vivo is larger (250 × 45 μm vs. 160 × 35 μm); secondly, it has more kinety rows in peniculi 1 and 2 (each row has five in F. mengi vs. four in F. guangdongensis ): thirdly, the contractile vacuole of F. mengi is located in the posterior third of the cell, whereas in F. guangdongensis it is located in the mid-body region ( Fan et al. 2011a).

Frontonia pallida can be clearly distinguished from F. guangdongensis by the following combination of characteristics: F. pallida has three kinety rows in peniculus 2, whereas F. guangdongensis has four; F. pallida has a funnel-shaped cytopharynx (vs. absent in F. guangongensis ); F. pallida ’s contractile vacuole is to the left of the cell median, whereas it is to the right in F. guangdongensis ( Czapik 1979, Dragesco and Dragesco-Kernéis 1986).

Frontonia guangdongensis spec. nov. can also be easily separated from F. microstoma Kahl, 1931 in having only a single contractile vacuole with no canals whereas the latter has two contractile vacuoles with associated canals. Frontonia guangdongensis also has fewer somatic kineties (52–65 vs. 110–120 in F. microstoma ) and fewer kinety rows in peniculus 3 (2 vs. 3 or 4) ( Roque 1961, Carey 1992).

Figures

Fig. 1. Frontonia guangdongensis spec. nov. in vivo (A–D, H–M), after protargol (E–G, N–Q, S) and silver nitrate (R, T) impregnation. A, H – ventral view of a typical individual; B, I – different body shapes; C – part of a pellicle, to show extrusomes; D – extrusomes; E, F – infraciliature in ventral and dorsal views, macronucleus, and contractile vacuole pore of a holotype specimen; G – infraciliature of the buccal area; J – buccal area; K – ventral view, arrows show polygonal crystal granules, double arrowhead marks the single macronucleus, arrowhead exhibits the contractile vacuole; L – anterior end of cell, arrowheads mark the anterior suture; M – posterior part of the cell, arrowheads mark the caudal cilia, arrows show extrusomes; N, R – structure of the buccal region, arrows on R depict postoral kineties and arrowheads mark vestibular kineties; O – macronucleus and micronucleus, arrow marks micronucleus and arrowhead shows ingested algae; P, Q, T – anterior suture (arrowhead in P) and postoral suture (arrowheads in Q, T); S – somatic kineties. CVP – contractile vacuole pore; Ma – macronucleus; Mi – micronucleus; P1–P3 – peniculi 1, 2, 3; PK – postoral kineties, PM – paroral membrane; VK – vestibular kineties. Scale bars:A = 60 μm, E, F = 40 μm, H, I = 70 μm, J = 20 μm.