Taxonomic Characterization of Vorticella fusca Precht, 1935 and

J. Eukaryot. Microbiol., 53(5), 2006 pp. 348–357
r 2006 The Author(s)
Journal compilation r 2006 by the International Society of Protistologists
DOI: 10.1111/j.1550-7408.2006.00112.x
Taxonomic Characterization of Vorticella fusca Precht, 1935
and Vorticella parapulchella n. sp., Two Marine Peritrichs
(Ciliophora, Oligohymenophorea) from China
PING SUN,a WEIBO SONG,a JOHN CLAMPb and KHALED A. S. AL-RASHEIDc
Laboratory of Protozoology, KLM, Ocean University of China, Qingdao 266003, China, and
b
Department of Biology, North Carolina Central University, Durham, North Carolina 27707, USA, and
c
Department of Zoology, College of Science, King Saud University, PO Box 2455, Riyadh 11451, Saudi Arabia
a
ABSTRACT. Two marine peritrich ciliates, Vorticella fusca Precht (1935) and Vorticella parapulchella n. sp. were discovered in the
littoral zone of Qingdao, northern China. Their morphology, infraciliature, and silverline system were described using live observation and
silver impregnation. The poorly known species V. fusca is redescribed, adding information about the oral infraciliature and pellicular
morphology. Vorticella parapulchella n. sp. is superficially similar to Vorticella pulchella Sommer (1951) but is distinguished from it by
being markedly smaller and having much more widely spaced pellicular ridges. The infundibular infraciliature of V. parapulchella is
extremely unusual in having infundibular polykinety 3 reduced to two rows, one of which has almost disappeared.
Key Words. Infraciliature, morphology, new species, taxonomy.
S
PECIES in the genus Vorticella are well-known as stalked,
solitary peritrich ciliates with highly contractile behavior that
have been found worldwide in marine and freshwater biotopes
(Jankowski 1976; Kahl 1935; Kent 1880–1882; Noland and
Finley 1931; Precht 1935; Sommer 1951; Song 1991a, b; Stiller
1971). Over 200 species have been recorded in this genus. However, fewer than one-third have been described using silver impregnation techniques (Foissner, Berger, and Kohmann 1992;
Song 1991a, b; Warren 1986). As demonstrated by some recent
studies, the infraciliature revealed with silver impregnation is
highly species-specific, especially the structure of infundibular
polykineties in the oral apparatus, and this plays an essential role
in determination of species (Clamp 1990a, 1992, 1997; Foissner et
al. 1992; Ji and Song 2004; Ji et al. 2005a, b). Likewise, the
number of pellicular ridges encircling the cell (silverline system)
can be determined accurately only by staining with silver and has
been shown to be important in discriminating species of peritrichs
from one another (Foissner and Schiffmann 1975).
During faunistic surveys of the biodiversity of ciliated protozoa
in marine waters off China, many new or little-known peritrichs
have been isolated and reported (Ji and Song 2004; Ji, Song, and
AL-Rasheid 2003; Ji, Song, and Warren 2004a, b; Ji et al.
2005a, b; Song 1991a, b). In the present study, two marine species of Vorticella isolated from the littoral zone in coastal waters
off Qingdao, China, were investigated using both in vivo and silver impregnation methods. One species was identified as Vorticella fusca Precht (1935) and the other proved to be a species new
to science. It is designated Vorticella parapulchella n. sp.
Living cells were observed with differential interference microscopy. The infraciliature was revealed by staining with protargol according to the method of Wilbert (1975). The silver
nitrate method (Song and Wilbert 1995) was used to demonstrate
the silverline system. Drawings of stained specimens were performed at 1,250 with the aid of a camera lucida.
RESULTS
Vorticella fusca Precht (1935) (Table 1 and Fig. 1–4, 9–16)
Description of Qingdao population. Cell measuring approximately 95–110 55–65 mm in vivo (Table 1), campanulateto barrel-shaped (Fig. 1, 2, 4, 10, 11). Peristomial collar relatively
thin and body constricted deeply beneath it (Fig. 1, 11); maximum
width of cell usually at oral end; peristomial disk flat and obliquely elevated above peristome (Fig. 1, 4, 10, 11). Pellicle striations can be seen above 400 magnification (Fig. 14), but surface
of cell appears completely smooth at low magnifications.
Cytoplasm colorless or slightly grayish, and some well-fed cells
packed with many grayish or yellowish food granules (Fig. 2, 4, 10,
11). Single large contractile vacuole dorsally located (Fig. 1, 12,
Table 1. Morphometric characters of Vorticella fusca from Qingdao
(first column) and Vorticella parapulchella (second column).
Character
Vorticella fusca
Mean SD
range, n
Vorticella
parapulchella
Mean SD
range, n
Body length in vivo (mm)
99.8 3.4
95.0–110.0, 11
59.3 2.4
55.0–65.0, 11
37.5 3.8
32.0–45.0, 15
35.2 4.1
28–41, 15
69.2 3.3
67–73, 10
28.4 1.7
25.0–30.0, 9
23.8 1.0
20.0–25.0, 9
18.1 0.8
17–19, 14
17.4 0.7
16–18, 14
10.6 1.1
9–12, 10
MATERIALS AND METHODS
All samples were collected using artificial substrates in the
form of microscope slides, which were immersed under the water
for one to several weeks at the sampling sites.
One population of V. fusca was collected from a beach on the
coast of the Yellow Sea at Qingdao, northern China on November
9, 2004. Salinity was approximately 3%, and pH 5 8.0. Vorticella parapulchella n. sp. was collected on December 6, 2004
from a pond (5 m deep, 50 m long, by 25 m wide), which abutted
the coast of Qingdao. Salinity was approximately 1.9%, and pH
was 8.1.
Corresponding Author: W. Song, Laboratory of Protozoology, KLM,
Ocean University of China, Qingdao 266003, China—Telephone number: 186-532-8203-2283; FAX number: 186-532-8203-2283; e-mail:
[email protected]
Body width in vivo (mm)
Body length after fixation
(mm)
Body width after fixation
(mm)
Number of silverlines from
peristome to aboral
trochal band
Number of silverlines
from aboral trochal band
to scopula
17.0 1.3
16–19, 10
7.9 0.9
7–9, 7
All measurements in mm. Max, maximum; Mean, arithmetic mean; Min,
minimum; n, number of individuals examined; SD, standard deviation.
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SUN ET AL.—TWO SPECIES OF VORTICELLA FROM CHINA
349
Fig. 1–9. Vorticella fusca and similar congeners. 1. Dorsal view of V. fusca from Qingdao in vivo. 2. Living individuals of V. fusca from Qingdao;
representative extended zooids at low magnification. 3. Infundibular infraciliature of V. fusca in dorsal view, arrow with numerals indicates numbering
convention for polykineties and rows of kinetosomes within each polykinety; protargol preparation. 4. Ventral view of V. fusca from Qingdao in vivo.
5. Living individual of V. fusca from Precht (1935). 6. Living individual of Vorticella longiseta from Dietz (1964). 7. Living individual of Vorticella
convallaria from Foissner et al. (1992). 8. Living individual of Vorticella similis from Kahl (1935). 9. Entire oral infraciliature of V. fusca in ventral view,
arrowhead marks epistomial membrane; protargol preparation. G, germinal kinety; H, haplokinety; Po, polykinety; P1–3, infundibular polykinety 1–3.
(Scale bars: Fig. 1–9, 4 5 50 mm; Fig. 2 5 150 mm.).
arrow). Macronucleus long, J-shaped; oral arm of macronucleus
semicircular, oriented transversely to long axis, located immediately below the peristome (Fig. 1); macronucleus extending aborally from oral end and recurved, forming bottom of ‘‘J.’’ Surface of
stalk usually smooth, occasionally with small protuberances.
Spasmoneme approximately 2 mm in diam., with row of highly refractile thecoplasmic granules, 0.6–0.9 mm, which are greenish
(Fig. 13, arrow). Some 0.3 mm grayish granules sparsely distributed among greenish granules (Fig. 13, arrowhead).
Oral infraciliature. Haplokinety (H) and polykinety (Po) complete approximately one circuit together around peristome and
continue into infundibulum, where they separate and make a complete circuit on opposite walls of the passageway before ending at
or near the cytostome (Fig. 3, 9, 16). Polykinety 1 (P1) accompanied by two additional polykineties (P2, P3) in infundibulum.
All infundibular polykineties composed of three rows of kinetosomes spread sufficiently far apart to be distinct. Adstomal ends of
rows in P1 terminate at slightly different levels; row 1 shortest;
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Fig. 10–16. Photomicrographs of Vorticella fusca from Qingdao. 10. Living zooid under low magnification. 11. Living zooid at 400 magnification. 12. Living zooid at 1,000 magnification; arrow indicates the contractile vacuole positioned close to the peristome. 13. Detail of stalk. Arrow
indicates highly refractile greenish granules; arrowhead marks grayish granules. 14. Living zooid at high magnification focused to show the pellicular
ridges. 15. Silverline system; silver nitrate preparation. Dark spots are pores; arrowheads indicate aboral trochal band. 16. Detail of infundibular polykineties; protargol preparation. P1–3, infundibular polykinety 1–3. (Scale bars: Fig. 10 5 80 mm; Fig. 11, 11, 12 5 40 mm.).
row 3 slightly longer than row 1; row 2 several kinetosomes longer than other two rows. P2 terminating between and above adstomal ends of P1 and P3, with row 3 slightly separated from other
two at abstomal end. P3 with three rows, of which rows 1 and 2 are
conspicuously shorter than row 3. Adstomal end of row 3 of P3
terminating near cytostome at same level as row 3 of P1. Germinal
kinety (G) lying parallel to the haplokinety within upper half of
infundibulum (Fig. 9). Epistomial membrane short and located
near opening of the infundibulum (Fig. 9, arrowhead).
Aboral trochal band composed of single band of loosely
arranged, paired kinetosomes encircling cell near aboral end
(Fig. 15, arrowheads).
Silverline system consisting of many parallel, transversely oriented pellicular striations, numbering 67–73 between peristomial
area and aboral trochal band and 16–19 between aboral trochal
band and scopula, with many sparsely distributed pellicular pores
(Fig. 15). Pellicular striations unevenly arranged: approximately
0.9 mm apart between aboral trochal band and scopula and 0.6 mm
apart in oral part of cell.
Vorticella parapulchella n. sp. (Table 1 and Fig. 17–23,
27–37)
Description of Qingdao population. Fully extended cell
approximately 25–30 20–25 mm in vivo, ratio of length to width
approximately 1:1. Body rotund in shape, widest at the midregion
of zooid and constricted below wide, swollen peristomial collar,
which measures approximately 15 mm in diam. (Fig. 17, 18, 28).
Peristomial disk prominently arched above peristomial collar.
Pellicle has distinct, widely spaced striations when viewed at
the 400 magnification (Fig. 21, 31).
Cytoplasm colorless or grayish, usually containing several refractile granules which are 2–4 mm in diam. (Fig. 17, 18, 23, 28, 29).
One contractile vacuole near the ventral wall of the infundibulum,
slightly above midbody (Fig. 17, 28). Macronucleus large,
C-shaped and oriented longitudinally (Fig. 17, 35). Micronucleus
not observed. Stalk is 60–100 mm long, relatively slender, approximately 4 mm wide; spasmoneme approximately 2 mm in diam.,
with numerous, 0.4 mm, dark gray thecoplasmic granules along its
length (Fig. 19, 30, arrowheads). Somatic myonemes extending
SUN ET AL.—TWO SPECIES OF VORTICELLA FROM CHINA
351
Fig. 17–27. Vorticella parapulchella n. sp. and similar congeners. 17. Dorsal view of typical zooid in vivo. 18. Extended zooid at low magnification.
19. Detail of stalk, showing thecoplasmic granules in spasmoneme. 20. Silverline system; silver nitrate preparation. 21. Surface of living individual in
profile showing widely spaced pellicular ridges. 22. Detail of infundibular polykineties, arrow indicates highly reduced row 2 of P3; protargol preparation. 23. Representative extended and contracted zooids in vivo. 24. Living individual of Vorticella striata from Song (1991a). 25. Living individual of
Vorticella jaerae from Precht (1935). 26. Living individual of Vorticella pulchella from Sommer (1951). 27. Entire oral infraciliature in ventral view;
protargol preparation. ATB, aboral trochal band; EM, epistomial membrane; G, germinal kinety; H, haplokinety; Po, polykinety; P1–3, infundibular
polykinety 1–3. (Scale bars: Fig. 17 5 15 mm.).
from scopula to oral area (Fig. 37), and linking there to each other
to form an encircling strand just beneath peristomial collar.
Zooids often closely grouped together and forming pseudocolonies of up to 30 zooids (Fig. 23). Telotroch stage was not observed.
Peristomial part of oral infraciliature consisting of typical haploand polykinety, which are parallel to one another and make one- and
one-quarter turns on edge of peristome. Epistomial membrane short,
located at opening of oral cavity (Fig. 27, 32, arrow). After entering
infundibulum, haplo- and polykinety spiral on opposite walls and
end at border of cytostome. Infundibular part of haplokinety
accompanied by germinal kinety in abstomal half (Fig. 27, 33).
Within infundibulum, polykinety transforming into P1, which is
accompanied for part of its length by P2 and P3 (Fig. 27, 33).
P1 consists of three rows of kinetosomes that extend to the edge of
the cytostome, ending there at the same level. P2 conspicuously
shorter than that of most other peritrichs; abstomal end of P2
terminating far short of infundibular entrance and not converging
with abstomal end of P1 (Fig. 22, 27, 33). Row 2 of P3 consisting of
only few kinetosomes, and lying next to abstomal end of row 1 (Fig.
22, arrow; 33, arrowhead). Row 1 of P3 extending abstomally
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Fig. 28–37. Photomicrographs of Vorticella parapulchella n. sp. 28. Typical zooid in vivo showing the contractile vacuole. 29. Living zooid at low
magnification. 30. Detail of stalk, arrowheads indicate thecoplasmic granules. 31. Living zooid at high magnification focused to show the pellicular
ridges. 32. Apical view of zooid, arrow marks epistomial membrane; protargol preparation. 33. Dorsal view of zooid showing the infraciliature. Arrows
mark aboral trochal band. 34. Silverline system; silver nitrate preparation. 35. Lateral view of zooid showing the macronucleus; protargol preparation.
36. Silverline system, arrowhead indicates the aboral trochal band; silver nitrate preparation. 37. Protargol preparation showing myonemes. G, germinal
kinety; Ma, macronucleus; P1–3, infundibular polykinety 1–3. (Scale bars: Fig. 28 5 20 mm; Fig. 29 5 40 mm.).
almost to abstomal end of P2, extending adstomally almost to cytostome (Fig. 22, 27).
Aboral trochal band composed of three rows of kinetosomes
encircling cell at approximately 1/6 of body length from scopula
(Fig. 20, 36).
Silverline system typical of genus, and pellicular striae widely
spaced. Approximately nine to 12 pellicular striations between
peristomial area and aboral trochal band, seven to nine pellicular
striations between aboral trochal band and scopula, and many
sparsely distributed pellicular pores (Fig. 20, 34, 36).
DISCUSSION
Comparison of Vorticella fusca to similar congeners. Vorticella fusca was originally discovered by Precht (1935) in the
Kieler Bucht near the entrance to the Baltic Sea attached to a
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Table 2. Morphometric comparison between Vorticella fusca and related species.
Species
Body length
in vivo (mm)
Body width
in vivo (mm)
Number of
pellicle striations
Habitat
Source of data
Vorticella fusca
V. convallaria
96–106
40–95
56–64
22–53
83–92
89–117
Marine
Freshwater
V. similis
V. similis
40–90
55–80
?
?
?
98–112
Freshwater
Freshwater
V. similis
V. nebulifera
V. longiseta
52–80
30–67
82
?
17–33
50
103–114
43–51
?
Soil
Marine
Marine
Present paper
Foissner, Berger, and
Kohmann (1992)
Kahl (1935)
Foissner and Schiffmann
(1975)
Foissner (1981)
Song (1991a)
Dietz (1964)
? data not available.
species of the green alga Enteromorpha (Fig. 5). His description
consisted only of short references to characters of the living organism; nothing about the infraciliature or silverline system was
included. Our population of V. fusca from Qingdao is virtually
identical to the species described by Precht, based on the general
features seen in vivo (e.g. size and shape of the body, presence of
refractile granules on the spasmoneme, J-shaped macronucleus)
and the fact that both are found in marine habitats.
In terms of its large size and bell-shaped body, V. fusca is similar
to the freshwater form, Vorticella convallaria sensu Foissner et al.
(1992). The former differs from the latter in its habitat (marine vs.
freshwater), the larger cell size (95–110 55–65 mm vs. 40–
95 22–53 mm), the position of the contractile vacuole (dorsal
vs. ventral), lower number of pellicular striations (67–73, 16–19 vs.
70–90, 19–27) and the structure of P3 (rows 1 and 2 considerably
shorter than row 3 vs. all three rows approximately equal in length)
(Table 2 and Fig. 7) (Foissner et al. 1992).
Vorticella fusca resembles Vorticella campanula in shape and
size of the body but differs from it by having a lower number of
silverlines from aboral trochal band to scopula (16–19 vs. 27–33),
a different pattern of rows in P3 (rows 1 and 2 considerably shorter than row 3 vs. all three rows approximately equal in length),
and a marine vs. freshwater habitat (Table 2 and Fig. 39, 48)
(Foissner et al. 1992).
Vorticella fusca seems most similar to Vorticella similis (Precht
1935). The silverline system and infraciliature of the latter have
been investigated by Foissner and Schiffmann (1975) and Foissner (1981) based on a freshwater population and a terrestrial isolate, respectively. Vorticella similis can be clearly separated from
V. fusca by its smaller size (50–80 mm vs. 95–110 mm), greater
number of pellicular striations (75–80 vs. 67–73 from peristomial
region to aboral trochal band; 28–34 vs. 16–19 from aboral trochal
band to scopula) and different biotope (freshwater vs. marine)
(Table 2 and Fig. 38). In addition, the P3 in V. similis is a tworowed structure (Fig. 44) vs. three rows in V. fusca (Fig. 3). Vorticella fusca matches V. similis sensu Kahl (1935) (Fig. 8) in some
aspects, e.g. in cell shape and in some other morphological characters (Table 2); however, the former can be identified by its
larger size (95–110 mm vs. 40–90 mm) and different habitat (marine vs. freshwater) (Kahl 1935).
The well-known marine form, Vorticella nebulifera also seems
to be similar to our species. It can be clearly identified by its
conspicuously smaller size (30–67 mm vs. 95–110 mm) and lower
number of transverse silverlines (35–39, 8–12 vs. 67–73, 16–19 in
V. fusca) (Table 2 and Fig. 40) (Song 1991a).
One incompletely described species (infraciliature unknown),
Vorticella longiseta Dietz (1964), has the large body size, bellshaped body, and marine habitat characteristic of V. fusca and
therefore should be compared with it. Vorticella longiseta can be
distinguished from V. fusca by its smaller cell size (82 50 mm
vs. 100 60 mm in vivo), conspicuously more slender body shape
(vs. bell shaped) and shape of macronucleus (C-shaped vs. Jshaped) (Table 2 and Fig. 6) (Dietz 1964).
Vorticella fusca Precht (1935)
(Table 1 and Fig. 1–4, 9–16)
Emended diagnosis. This diagnosis incorporates previously
undescribed features of the infraciliature and silverline system.
Large marine Vorticella, measuring approximately 100 60 mm
in vivo; zooid bell-shaped with thin peristomial collar; macronucleus J-shaped; one contractile vacuole dorsally positioned; number of transverse silverlines from scopula to aboral trochal band
16–19 and from aboral trochal band to peristomial area 67–73;
rows of infundibular polykinety 1 (P1) unequal in length, row 2 of
P1 longer than other two rows; abstomal end of row 3 of P2 diverging slightly from other two rows; rows 1 and 2 of P3 much
shorter than row 3 of P3, ending adstomally far short of adstomal
ends of row 3 of P3 and rows of P1.
Deposition of specimens. One slide of protargol-impregnated
specimens was designated as a neotype and deposited in the Lab-
Table 3. Morphometric comparison between Vorticella parapulchella and related species.
Species
Vorticella parapulchella
V. pulchella
V. astyliformis
V. costata
V. striata
V. jaerae
? data not available.
Body length
in vivo (mm)
Body width
in vivo (mm)
Number of
pellicle striations
Habitat
Source of data
25–30
46
30–50
20–28
22–40
40–53
20–25
40
?
?
16–24
?
16–21
?
20–35
18–30
34–39
?
Marine
Freshwater
Soil
Freshwater
Marine
Marine
Present paper
Sommer (1951)
Foissner (1981)
Foissner (1979)
Song (1991a)
Precht (1935)
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Fig. 38–50. Vorticella similis, Vorticella campanula, Vorticella nebulifera, Vorticella astyliformis, Vorticella costata and representative
infraciliature of Vorticella species whose oral infraciliature has been described. 38–42. Living individual of V. similis (38, from Foissner and Schiffmann 1975), V. campanula (39, from Foissner et al. 1992), V. nebulifera (40, from Song 1991a), V. astyliformis (41, from Foissner 1981) and V. costata
(42, from Foissner 1979). 43–46. Infraciliature of V. astyliformis (43, from Foissner 1981), V. similis (44, from Foissner 1981), Vorticella infusionum
(45, from Foissner et al. 1992) and Vorticella aquadulcis (46, from Foissner et al. 1999). 47–49. Infundibular polykineties of V. vernalis (47, from
Foissner, et al. 1999), V. campanula (48, from Foissner et al. 1992), Vorticella chlorellata (49, from Wang, Shi, and Hu 2004). 50. Infraciliature of
Vorticella convallaria from Foissner et al. (1992). P1–3, infundibular polykinety 1–3.
oratory of Protozoology, OUC, China (Registration number
040110901). An additional slide of material stained with silver
nitrate was also deposited in the same collection (Registration
number 04110902).
Comparison of Vorticella parapulchella n. sp. to similar congeners. Vorticella pulchella Sommer (1951) is morphologically
similar to V. parapulchella and was originally found as an epibiont attached to the crustacean, Cyclops sp. (Sommer 1951) (Fig.
26). Excellent illustrations and detailed descriptions of the living
organism provided by Sommer (1951) enabled us to determine
with certainty that our organism was not V. pulchella. Vorticella
parapulchella can be distinguished from V. pulchella by its smaller size (25–30 20–25 mm vs. 46 40 mm), narrower peristomial
collar (15 vs. 28 mm in width) and different habitat (marine vs.
freshwater) (Table 3) (Sommer 1951).
Another marine species of Vorticella that is also small
(26 29 mm), with a spherical cell shape and low number of
transverse silverlines (25), was reported by Song (1991a) as V.
pulchella. The differences between Sommer’s (1951) original de-
SUN ET AL.—TWO SPECIES OF VORTICELLA FROM CHINA
355
Fig. 51a–r. Infundibular polykineties of Vorticella, Pseudovorticella, Carchesium, and Epicarchesium species whose oral infraciliature has been
described. 51a–j. Infundibular polykineties of Vorticella campanula (51a, after Foissner et al. 1992), Vorticella convallaria (51b, after Foissner et al.
1992), Vorticella chlorellata (51c, after Wang et al. 2004), V. fusca (51d, after original paper), V. vernalis (51e, after Foissner et al. 1999), V. similis (51f,
after Foissner 1981), Vorticella infusionum (51g, after Foissner et al. 1992), Vorticella aquadulcis (51h, after Foissner et al. 1999), Vorticella astyliformis
(51i, after Foissner 1981), V. parapulchella (51j, after original paper). 51k–o. Infundibular polykineties of P. monilata (51k, after Foissner et al. 1992),
P. clampi (51l, after Ji et al. 2005b), P. sinensis (51m, after Ji et al. 2003), P. elongata (51n, after Leitner and Foissner 1997), P. paracratera (51o, after Ji
et al. 2004a). 51p–r. Infundibular polykineties of C. polypinum (51p, after Lom 1964), E. granulatum (51q, after Leitner and Foissner 1997), E. abrae
(51r, after Ji et al. 2004b). Arrow with numerals indicates numbering convention for polykineties and rows of kinetosomes within each polykinety.
scription and that of Song’s (1991a) convince us that the population of V. pulchella reported by Song was a misidentification and
should be considered conspecific with V. parapulchella.
Different from Vorticella astyliformis, our new species is a
marine form (vs. soil), is smaller (25–30 vs. 30–50 mm), has different number of pellicular striations (9–12 vs. 17–30 from peristomial region to aboral trochal band; 7–9 vs. 3–5 from aboral
trochal band to scopula in V. astyliformis), and has a different
pattern of P3 (row 2 extremely short vs. two rows about equal
length) (Table 3 and Fig. 41, 43) (Foissner 1981).
Vorticella costata (Fig. 41) is also similar to our new species
considering body shape and general appearance in vivo, but it can
be clearly recognized by the freshwater habitat (vs. marine) and
different number of pellicular striations (14–25, 4–5 vs. 9–12, 7–
9) (Table 3 and Fig. 42) (Foissner 1979).
Vorticella parapulchella can be distinguished clearly from
Vorticella striata, another small form, by its conspicuously spher-
ical body shape (vs. cylindrical body shape of V. striata) and the
quite different number of pellicular striations (9–12, 7–9 vs. 29–
32, 5–7 in the latter) (Table 3 and Fig. 24) (Song 1991a). Vorticella jaerae Precht (1935) is also small but is characterized by a
larger body size than in V. parapulchella (40–53 vs. 25–30 mm)
and different body shape (bell-shaped vs. spherical in shape in V.
parapulchella) (Table 3 and Fig. 25) (Precht 1935).
Vorticella parapulchella n. sp.
(Table 1 and Fig. 17–23, 27–37)
Synonymy. Vorticella pulchella sensu Song (1991a, p. 122).
Diagnosis. Small marine Vorticella, measuring approximately
30 mm 25 mm in vivo; zooid spherical in shape with a wide,
swollen peristomial collar; macronucleus C-shaped; single contractile vacuole ventrally positioned; pellicular ridges prominent;
number of transverse silverlines from peristome to aboral trochal
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band 9–12, from aboral trochal band to scopula 7–9; P2 extremely
short, abstomal end of P2 terminating far short of infundibular
entrance and not converging with abstomal end of P1; P3
with only two rows, row 2 extremely short and lying at abstomal
end of row 1.
Etymology. The specific epithet refers to the superficial similarity in body shape between this species and V. pulchella.
Type specimens. One holotype slide with protargol-impregnated specimens and one paratype slide of silver nitrate-impregnated specimens have been deposited in the Laboratory of
Protozoology, OUC, China (registration numbers: 04120601,
04120602).
Variability of the oral infraciliature in vorticellid peritrichs. Commonly accepted criteria for characterization of species in peritrich ciliates traditionally have been body shape and
size, appearance of the body surface (especially prominence of
pellicular ridges), characteristics of the stalk (if present), characteristics of the lorica (if present), number and location of the contractile vacuole, structure of the oral apparatus, and the habitat
(Clamp 1990a, b, 1992, 1997; Foissner et al. 1992; Kahl 1935;
Song 1991a, b). To this suite of characters have been added features of silverline system (number of silverlines and spacing)
(Foissner and Schiffmann 1975) and the oral infraciliature (Clamp
1990a, b; Lom 1964).
Over the last four decades, it has become apparent that details
of the kinetosomal rows making up the infundibular polykineties
of the oral infraciliature are especially diagnostic at the species
level (Clamp 1990a, b; Lom 1964). The general pattern in sessiline peritrichs is to have three infundibular polykineties (P1–P3)
consisting of three rows of kinetosomes each, a pattern that can be
summarized as 31313. As far as is known, no sessilines have lost
rows from P1 or P2; however, loss of one row from P3 has occurred in some genera (e.g. Vorticella, Fig. 51 and Lagenophrys
[Clamp 1990a, b]), a pattern that can be summarized as 31312.
Beyond this primary type of variation in the infundibular polykineties, there are also differences between species with respect to
position of entire polykineties relative to one another. Some species of Vorticella and Pseudovorticella have P1 and P2 closely
parallel to one another (Fig. 51). In other species of these two
genera, P1 and P2 are separated by a wide gap. This same type of
variation is also known from Lagenophrys (Clamp 1990a, b, 1991,
1992, 1997). Furthermore, the same sort of variation exists in the
position of P3 relative to P2, with some species of Vorticella,
Pseudovorticella, Carchesium, and Epicarchesium having P3 lying close to P2 and other species of these genera having P3 separated from P2 by a noticeable gap (Fig. 51). Finally, species show
differences in the length of individual rows with a polykinety relative to one another (Fig. 51).
Rows of infundibular polykineties, especially P3, of species of
Vorticella and Pseudovorticella vary more between species (Fig.
43–50, 51a–o) (Foissner 1981; Foissner et al. 1992; Foissner, Berger, and Schaumburg 1999) than in some other genera (e.g. Lagenophrys) (Clamp 1990a, b, 1991, 1992, 1997). Some species in
both genera have three rows of kinetosomes in P3, with all three
rows approximately equal to one another (Fig. 51a, b, k, l). Others
have the 31313 pattern but with row 1 or both rows 1 and 2 of P3
shorter than other rows (Fig. 51c–e, m–o).
Vorticella parapulchella represents an extreme modification of
P3, having only two rows but with row 2 reduced to a vestige (Fig.
51j). In essence, V. parapulchella is close to having only one row
of kinetosomes in P3. Also unusual is the fact that it is row 2 of P3
that is reduced in V. parapulchella. This is opposite to the pattern
seen in other species with reduced rows in P3 which have the first
one or two rows shortened (Fig. 51c–e, h, m–o, q, r).
Strong similarities in the pattern of infundibular polykineties
between species in the same genus and in different genera also can
be found. For example, the infraciliatures of Vorticella chlorellata
(Fig. 51c), Pseudovorticella sinensis (Fig. 51m), Pseudovorticella
elongata (Fig. 51n), and Epicarchesium granulatum (Fig. 51q) are
virtually identical. In short, the pattern of infundibular polykineties in each species of peritrichs is species-specific; but not necessarily unique, however, species and genera with similar
infundibular polykineties still can be separated clearly from one
another by other morphological differences.
Aside from their role in determining taxonomic assignments of
species, the infundibular polykineties will surely have some important part to play in future phylogenetic studies. Similarities
such as the one between P. sinensis and P. elongata may indicate
a closer evolutionary relationship between these two species than
between other members of Pseudovorticella. Likewise, similar
congruence can be recognized between the infundibular polykineties of V. fusca (Fig. 51d) and Vorticella vernalis (Fig. 51e) on one
hand and between those of Vorticella infusionum (Fig. 51g),
Vorticella aquadulcis (Fig. 51h), and V. astyliformis (Fig. 51i)
on the other hand. Similar patterns of infraciliature in species of
different genera (e.g. Vorticella chlorellata, Fig. 51c and Pseudovorticella sinensis, Fig. 51m) are probably the result of evolutionary convergence, but this would have to be confirmed by a
comprehensive phylogenetic study including molecular evidence.
ACKNOWLEDGMENTS
This work was supported by the Natural Science Foundation of
China (project number: 30430090) and a publication fund from
the King Saud University, Saudi Arabia, awarded to AL-Rasheid.
Thanks are due to Mr. Dapeng Xu, Laboratory of Protozoology,
OUC, for making protargol preparation of Vorticella parapulchella and collecting samples.
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Received: 12/14/05, 03/08/06, 04/17/06; accepted: 04/20/06