Trochilia recta Kahl, 1928

Pan, Hongbo, Ma, Honggang, Hu, Xiaozhong, Al-Rasheid, Khaled A. S. & Al-Farraj, Saleh A., 2013, Taxonomic Studies on Three Marine Ciliates from China, Including a New Species (Ciliophora, Cyrtophorida), Acta Protozoologica 52 (1), pp. 25-33 : 30-33

Syn. Trochilia recta Kahl, 1928

Trochilioides recta is a relatively well-studied species. It was originally described by Kahl (1928) as a member of Trochilia . Subsequently, Kahl (1931) assigned it to the new genus Trochilioides according to its ciliary arrangement though he could not be the author of this genus (as mentioned above). Later it was redescribed twice in more or less details ( Deroux 1976c, Foissner et al. 1991). Therefore we just supply a brief description of the Qingdao population.

Description of Qingdao population: Cells about 35 × 20 μm in vivo. Body broad oval in outline with both ends bluntly rounded ( Fig. 3A, E, G ). Dorsoventrally flattened about 2:1, ventral side flat, in right region slightly concave where the ventral ciliary rows are located; dorsal side somewhat humped ( Fig. 3B, F ). Cytostome ventrally positioned at anterior 1/5 of body length; about six conspicuous nematodesmal rods around it ( Fig. 3A, E ). Cytoplasm colourless, containing some greasily shinning globules (2–3 μm across). Two contractile vacuoles, 5 μm in diameter, located at anterior and posterior 1/4 of cell ( Fig. 3K ). Podite about 6 μm long, caudally positioned ( Fig. 3A, G ). Single ellipsoid macronucleus in central region, about 15 × 10 μm in vivo ( Fig. 3K ).

Infraciliature as shown in Fig. 3C, D, H–J, L, M . 17–20 somatic kineties in total, comprising six right kineties, six to nine left kineties and five postoral kineties. Two right-most kineties, almost equal in length, and extending anteriorly to anterior margin. Postoral and left kineties very short and distributed in anterior body half, the posterior ends of which are progressively shortened from right to left ( Fig. 3J ). Equatorial fragment ( Fig. 3L ) composed of 0–14 basal bodies, while terminal fragment consisting of 4–6 ones ( Fig. 3H ). Usually, five or six kinetosome-like granules present near the base of podite and arranged in a letter “C” pattern ( Fig. 3C, D, I ). Two circumoral kineties and one preoral kinety composed of dikinetids and obliquely arranged ( Fig. 3C, D, H ).

Remarks: According to Kahl (1931), Trochilioides recta is a euryhaline species and it occurs in waters with salinity from 3 to 25‰. Before the detailed infraciliature was first revealed by Deroux (1976c), several forms ( Fig. 4D–F ) had been reported under this name ( Agamaliev 1974, Borror 1972, Dragesco 1966). Among these, Trochilioides recta sensu Agamaliev, 1974 ( Fig. 4D ) was assigned to Orthotrochilia as O. agamalievi by Deroux (1976c), while Trochilioides recta sensu Dragesco, 1966 ( Fig. 4F ) was considered as another species by Foissner et al. (1991). In terms of body size, shape, the number of contractile vacuoles and infraciliature, our isolate resembles the original population ( Fig. 4A, B ) and the population of Deroux ( Fig. 4H ) very well, and they must, therefore, be conspecific.

Foissner (1984) collected a freshwater isolate, namely Trochilioides fimbriatus Foissner, 1984 ( Fig. 4N, O ), whose infraciliature nearly has no difference from T. recta . However, the former has peculiar basket-curtain which is not found in our and previous populations of T. recta and other species of Trochilioides . Additionally, it can be separated from T. recta by the location of the terminal fragment (left of frontoventral kineties vs. right of end of frontoventral kineties) and its orientation (vertical vs. horizontal). So both very likely are distinct species.

To date, besides Trochilioides tenuis ( Fig. 4I ), T. recta and T. fimbriatus , there are four species of Trochilioides whose infraciliature are known, namely, Trochilioides dispar Faure-Fremiet, 1965 ( Fig. 4L ), Trochilioides bathybius Jankowski, 1967 ( Fig. 4J, K ), Trochilioides littoralis Jankowski, 1967 ( Fig. 4M ), and Trochilioides trivialis Fenchel, 1965 ( Fig. 4G ). Among these, the pattern of infraciliature of T. trivialis is quite different due to the fact that some of the postoral kineties are subterminally ended ( Fenchel 1965). According to Chen et al. (2011), a critical feature through which it is possible to distinguish Chlamydonyx from Trochilioides is that part of the postoral and all of the left kineties extend to the posterior. Based on this criterion, T. trivialis should be transferred to the genus Chlamydonyx as Chlamydonyx trivialis ( Fenchel, 1965) comb. nov.

A simple key to the identification of Trochilioides spp. with available infraciliature data can be proposed as below:

1 Five frontoventral kineties T. bathybius

1’ Two frontoventral kineties 2

2 Three right kineties 3

2’ Five or six right kineties 4

3 Four left kineties T. tenuis

3’ More than four left kineties T. dispar

4 17 postoral kineties and left kineties in total T. littoralis

4’ 11–14 postoral kineties and left kineties in total 5

5 Absence of basket-curtain T. recta

5’ Presence of basket-curtain T. fimbriatus

Acknowledgements. This work was supported by the National Natural Science Foundation of China (Project Nos. 31201703, 41176119), Innovation Program of Shanghai Municipal Education Commission (Project No. 13YZ095), Research Group Project No. RGP-VPP-083, King Saud University Deanship of Scientific Research, and the Key Laboratory of Mariculture of Ministry of Education, Ocean University of China. Many thanks to Dr. Jiamei Jiang (Laboratory of Protozoology, OUC, China) for her help with sampling. We are also grateful to Dr. Alan Warren (Natural History Museum, UK) for his literature support, and Prof. Foissner and another anonymous reviewer for their constructive comments.

Figures

Fig. 3A–M. Trochilioides recta from life (A, B, E–G, K) and after protargol impregnation (C, D, H–J, L, M). A – ventral view of a typical individual; B, F – right view, arrowhead (F) indicates contractile vacuole; C, D – to show infraciliature, arrows mark kinetosome-like granules at base of podite; E, G – ventral view, arrowheads (E) point to tooth and arrow (G) shows podite; H – anterior portion, double arrowheads point to circumoral kineties, arrow refers to preoral kinety, arrowhead indicates terminal fragment; I – posterior portion, arrow marks kinetosome-like granules at base of podite; J – anterior portion, arrows point to postoral kineties; K – details of cytoplasm, arrows show contractile vacuoles, arrowheads refer to nematodesmal rods; L – right portion of ventral side, arrowhead points to equatorial fragment; M – infraciliature. Co – circumoral kineties, EF – equatorial fragment, FvK – frontoventral kineties, Ma – macronucleus, Pr – preoral kinety, TF – terminal fragment. Scale bars: 20 µm (A, C), 15 µm (E, G, M).

Fig. 4A–O. Trochilioides recta and its congeners whose infraciliature are known. A–C, E, H – Trochilioides recta, A and B from Kahl (1928), C from Kahl (1931), E from Borror (1972), H from Deroux (1976); D – Orthotrochilia agamalievi (syn. Trochilioides recta sensu Agamaliev, 1974), fromAgamaliev (1974); F – Trochilioides recta sensu Dragesco, 1966, from Dragesco (1966); G – Trochilioides trivialis, from Fenchel (1965); I – T. tenuis, from Deroux (1976); J, K – T. bathybius, J from Jankowski (1967), K from Deroux (1976); L – T.dispar, from Fauré-Fremiet (1965); M – T. littoralis, from Jankowski (1967); N, O – T. fimbriatus, from Foissner (1984), arrowhead (O) points to the basket-curtain. Scale bars: 20 µm.