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Protistology 3 (4), 219-222 (2004)
Protistology
Stylonychia harbinensis sp. n., a new oxytrichid ciliate (Ciliophora, Hypotrichia) from the Heilongjiang Province, China
Shi Xin-Bai1 and Dieter Ammermann2
Stylonychia harbinensis sp. n. is widely distributed in fresh waters around Harbin, China. It belongs to the S. mytilus-complex (S. mytilus, S. lemnae and S. ammermanni). It is 142 x 58 ^m in size (Protargol-impregnated cells) and usually has 2 large micronuclei (5 ^m in diameter). S. harbinensis sp. n. has much smaller cells than S. mytilus and S. lemnae, and larger micronuclei than S. ammermanni. The new species also has a unique pattern of dorsal bristles. S. harbinensis sp. n. does not conjugate either with other species of the S. mytilus complex or with other Stylonychia species.
Introduction
Stylonychia is a widely distributed and well known freshwater oxytrichid ciliate genus. According to Foissner and others (1991), the first description of a Stylonychia species (S. mytilus) was published by Müller (1773). In his famous work Kahl (1932) recognized 11 species of the genus Stylonychia. Berger (1999), in his detailed review of the family Oxytrichidae, also validated 11 species. Most recently a new species, S. ammermanni, has been described from India (Gupta et al., 2001).
In this paper we describe a new species, S. harbinensis sp. n., which is widely distributed in fresh waters around Harbin, China. Preliminary reports of this species were presented earlier at “The second Asian
Conference on Ciliate Genetics, Cell Biology and Molecular Biology” (Shanghai, 1986) and in the “Proceedings of the 4th Symposium of the Chinese Protozoological Society” (Guang Zhou, 1987). However, the species had not been described in sufficient detail and Berger (1999, p. 599) therefore listed this name as “nomen nudum”.
Material and methods
Stylonychia harbinensis sp. n. was found in several ponds and small rivers around Harbin (126°80 E, 45°70 N). Most of the clones researched in preparation of the present paper were isolated from a pond in the Sun Island, located on the Song-Hua River in the northern part of Harbin. This pond is connected to and fed by
© 2004 by Russia, Protistology
the Song-Hua River. S. harbinensis sp. n. was also found in the river itself. The holotype slide contains Protargol-impregnated cells from this location. This is therefore the type locality (“Terra typica”) of the new species. This slide is deposited at the “Biology Centre of the upper Austrian Museum”, J.-W.-Klein. Str. 73, A-4040 Linz, Austria (Collection “Evertebrata varia”, no. 2003/45). Paratype slides are deposited at the Laboratory of Protozoology of the Harbin Normal University (Harbin 150080, China) and at the “Zoolo-gische Schausammlung” of the University of Tuebingen, Sigwartstr. 3, D-72076 Tuebingen.
The cells were grown in sterilized pond water (or Pringsheim’s solution) and fed with the phytoflagellate Chlorogonium elongatum or the saprozoic flagellate Chilomonas paramecium. They were studied either alive or fixed and impregnated with Protargol. The modified Protargol method described in Shi and Frankel (1990) was used, except that the step “3” was changed to soaking the cells in albumin-glycerine-water (50 parts of distilled water with 2 parts of fresh egg albumin and
Stylonychia harbinesis sp. n. (Figs 1-4) possesses a rigid body, 18 frontal-ventral-transverse (FVT)-cirri, two rows of marginal cirri distinctly separated posteriorly and a large peristome (about a half of the cell length). It clearly belongs to the S. mytilus complex, a group of similar species (S. mytilus, S. lemnae and S. ammer-manni). In general appearance it looks like a small S. mytilus. The characteristics of Protargol-stained cells are listed in Table 1. The new species is certainly not easy to distinguish from the other three species of the mytilus-group, but the combination of three characteristics allows a clear identification:
S. harbinensis sp. n. has large Mi: 7 ^m in diameter in living cells, 5 ^m in Protargol-impregnated cells. This is the same size range as that of the S. mytilus Mi, while S. lemnae has slightly smaller Mi (6 ^m in living cells, 4 ^m after Progargol) (Ammermann and Schlegel, 1983). The Mi of S. ammermanni are considerably smaller: 2.62 ^m after Protargol (Gupta et. all., 2001); 4 ^m in living cells (own measurements).
Other distinguishing markers: The buccal cirrus in S. harbinensis sp. n. is located more posteriorly compared to S. ammermanni: the distance from the anterior end of the S. harbinensis sp. n. cell to the buccal cirrus is 27% of the cell length (Table 1), compared to 18% in S. ammermanni (according to Fig. 1A in Gupta et al., 2001). This is another small difference between these two species.
S. harbinensis sp. n. can also be distinguished by its
The number of micronuclear chromosomes, examined in young macronucleus enlages of early exconjugants, is about 950 in S. harbinensis sp. n. (in S. lemnae 2n = 360, Ammermann, 1987). Similar data from other species are not available.
The macronucleus is bipartite, as in all members of the S. mytilus group.
S. harbinensis sp. n. has a high division rate: the cells divide every 9 hours at room temperature (21° C) in the laboratory. The same rate is found in S. ammermanni (Sapra, pers. comm.). The length of cell cycle in S. mytilus and S. lemnae is 12 hours.
The pattern of division morphogenesis of S. harbinensis sp. n. is similar to that described for other members ofthe S. mytilus-group(Wirnsberger et al., 1986; Gupta et al., 2001). Therefore, we do not give any details.
Attempts to cross mature strains of S. harbinensis with other species from our collections, viz. S. mytilus, S. lemnae, S. ammermanni, S. pustulata, S. putrina, S. notophora, S. pusilla and S. vorax did not yield any conjugants (Sapra, personal communication and our own experiments). However, S. harbinensis sp. n. has mating types. Strains from different ponds mate with each other.
Comparison with other Stylonychia species.
The distinguishing characteristics of S. harbinensis sp. n. have already been described and a comparison
Protistology ■ 221
Figs. 1-3. Stylonychia harbinensis sp. n. 1 - Living cell, dorsal view; 2-3 - Protargol-impregnated cells, ventral (2) and dorsal (3) view, with 1-6 = kineties. Scale bars: 25 ^m.
Table 1 Morphometric characterization of Stylonychia harbinensis n. sp.
Fig. 4. Stylonychia harbinensis sp. n. Line diagram, ventral view.
with the other three species of the S. mytilus-complex has been made. However, it may be helpful to compare the new species with other species of the genus Stylonychia because the differences can be quite subtle.
Character Mean ± S.D. n
Cell length (^m) 142 і 6 ^m 15
Cell width (^m) 58 і 3 ^m 15
Cell length/width 2.54 і 0.85 15
Peristome length in % from cell length 51.5 % і 2.17 15
Distance anterior end/buccal cirrus
in % from whole length 27.2 % і 1.66 15
No. of adoral membranelles 45 і 4 10
No. of left marginal cirri 19 і 2 10
No. of right marginal cirri 27 і 4 10
No. of dorsal bristles in row 1 40 і 3.6 10
(see Fig. 3) 2 39 і 2.9 10
Mi number 2.1 і 0.5 20
Mi diameter, ^m, 5 і 0.25 ^m 10
Ma size (^m), length 22 і 3.5 ^m 20
Ma size (^m), with 11 і 2.0 ^m 20
Notes: The data were taken from Protargol impregnated cells. S.D. - standard deviation, n = number of specimens measured, x) could not be counted
in S. pseudograndis is also much shorter than in S. harbinensis sp. n.
Acknowledgements
We thank Prof. Dr. G. R. Sapra, Dept. of Zoology, University of Delhi, Delhi, India, for valuable advice and help. We also thank Dr. H. Berger, Salzburg (Austria) for some comments on the manuscript.
References
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Ammermann D. and Schlegel M. 1983. Characterization of two sibling species of the genus Stylonychia (Ciliata, Hypotricha): S. mytilus Ehrenberg, 1838 and S. lemnae n. sp. I. Morphology and reproductive behavior. J. Protozool. 30, 290-294.
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Wirnsberger E., Foissner W. and Adam H. 1986. Biometric and morphogenetic comparison of the sibling species Stylonychia mytilus and S. lemnae, including a phylogenetic system for the oxytrichids (Ciliophora, Hypotrichida). Arch. Protistenkd. 132, 167-185.
Address for correspondence: Dieter Ammermann, Lindenstr. 17, D 72119 Ammerbuch, Germany. E-mail: dieter.ammermann@uni-tuebingen.de
Editorial responsibility: Sergei Fokin
