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Protistology 4 (3), 195-201 (2006)
Protistology
New and little known free-living ciliates from the plankton of the Caspian Sea
Ilham Alekperov 1, Edward Buskey 2 and Nataly Snegovaya 1
1 Institute of Zoology NAS of Azerbaijan, Baku, Azerbaijan
2 University of Texas, Marine Sciences Institute, Port Aransas, USA
Summary
Two new for science (Strombidium nabranicum sp. n. and Euplotes khazarica sp. n.) and one little-known (Euplotes alatus Kahl 1932) species of free-living ciliates from the plankton of the Caspian Sea are described.
Key words: free-living ciliates, plankton, Strombidium nabranicum sp. n., Euplotes khazarica sp. n., Euplotes alatus, impregnation, Caspian Sea
Introduction
The Caspian Sea is the largest continental water body on the Earth (Dumont, 1998). It is known for its petroleum resources and sturgeon fisheries. This elongate water body is divided into three parts; a shallow northern basin in which its main freshwater inflow, the Volga River, enters, and two deep basins in the central and southern regions. Average salinity is about 12.8%o, and water temperatures exhibit both a north-south gradient and seasonal changes (Dumont, 1998). Vertical mixing keeps the deep basins oxygenated to the bottom, unlike the Black Sea (Kosarev and Yablonskaya, 1994). Nutrient levels and primary production in the Caspian Sea are generally low, although nutrient influx has increased sharply in recent years (Dumont, 1998).
Although this closed salt-water reservoir has no outlets to the ocean, and possesses many attributes of a sea (Zenkevitch, 1963), its legal status as a lake or sea
remains undefined, and this in turn affects how access to resources are regulated between countries (De Mora and Turner, 2004). The Caspian Sea has a highly endemic biota, characterized by their euryhaline tolerances, with both freshwater species that tolerate salinities of up to 13%o, and marine species that tolerate low salinities (Dumont, 1998). During the past few decades the Caspian Sea has undergone a series of serious environmental challenges including pollution, over fishing, introduction of invasive species and changes in water level (Barannik et al., 2004). These environmental changes make it especially important to increase efforts to characterize the biota of the Caspian Sea.
The Caspian Sea has a diverse ciliate fauna with 460 species of ciliates, including 138 planktonic species (Agamaliev, 1983; Alekperov and Asadullayeva, 1996, 1997, 1999). Planktonic ciliates of the Caspian Sea are represented mainly by marine species (125 species), with only 11 freshwater species, and 2 brackish water species.
© 2006 by Russia, Protistology
In spite of long term investigations of ciliates in the Caspain Sea, several new species have been discovered during a recent sampling program and they are described here. We describe three species of ciliates collected in the near-shore plankton of the central basin of the Caspian Sea in the vicinity of Nabran village (North Azerbaijan). One of them (Euplotes alatus Kahl 1932) is new for the Caspian fauna and the others (Strombidium nabranicum sp. n. and E. khazarica sp. n.) are new for science.
Material and Methods
The topology of kinetomes was determined using the silver impregnation method (Chatton and Lwoff, 1930; Alekperov, 1992). The nuclei were stained with the Feulgen nuclear reaction. All the measurements were made on no less than 10 (usually 15) randomly selected specimens. Morphometric characterization of all described ciliates species is given in the Table 1. The type specimens of the new taxa have been deposited in
the Institute of Zoology, National Academy of Sciences of Azerbaijan, Baku.
Results
Description of species
Strombidium nabranicum sp. n. (Table 1; Figs 1, AB; 5, A-B).
Diagnosis. Size of living cells 60-80 ! m, after fixation up 65 ! m, acontractile. Somatic ciliature consisting of18-20 dikinetid rows. Body surface covered with multiple silverline system. There are 15 anterial (collar) and 14 ventral (adoral) membranelles.
Type location. Littoral plankton of the Middle Caspian Sea (near Nabran village, not far from Azerbaijanian border with Russia).
Type specimens. A holotype and a paratype of S. nabranicum sp. n. on two slides with silver nitrate impregnated cells have been deposited in the collection of microscope slides of the Laboratory of Protistology
Table 1. Morphometric characterization of described ciliates species (after impregnation)*.
Strombidium nabranicum sp. n.
Character Mean M Max Min SD SE n
Length 69 65 80 60 7,66 1,98 15
Width 58 61 65 50 5,86 1,51 15
Collar number of membranells 15 15 16 14 0,54 0,14 15
Ventral number of membrannels 14 14 14 13 0,46 0,12 15
Somatic rows number 34 35 37 31 1,58 0,41 15
Macronucleus length 32 32 35 28 2,56 0,66 15
Diameter of micronucleus 3,7 3,8 4,0 3,1 0,32 0,81 15
Length of ventral membranells 9 9 12 6 2,18 0,56 15
Length of collar membranelles 23 24 26 20 1,96 0,62 10
Euplotes alatus Kahl 1932
Character Mean M Max Min SD SE n
Length 26 28 30 20 4,20 1,08 15
Width 22 22 30 11,5 5,62 1,45 15
Adoral membranelles number 42 42 45 40 2,03 0,52 15
Adoral zone length 27 27 30 24 1,89 0,49 15
Macronucleus length 21 21 25 17 2,93 0,76 15
Fronto-ventral cirri number 10 10 10 10 0 0 15
Caudal cirri number 4 4 4 4 0 0 15
Dorso-lateral kineties number 8 8 8 8 0 0 15
Number of dorsal bristles in the 14 14 18 12 1,62 0,42 15
dorso-lateral rows
Euplotes khazarica sp. n.
Character Mean M Max Min SD SE n
Length 30 30 35 22 3,56 0,93 15
Width 28 29 32 20 4,20 1,09 15
Adoral membranelles number 48 48 50 45 2,09 0,54 15
Adoral zone of membranelles, length 26 26 29 23 1,76 0,45 15
Macronucleus length 27 27 29 25 1,1 0,28 15
Fronto-ventral cirri number 11 11 11 11 0 0 15
Caudal cirri number 4 4 4 4 0 0 15
Transversal cirri number 5 5 5 5 0 0 15
Dorso-lateral kineties number 5 5 5 5 0 0 15
Number of dorsal bristles in the 18 18 19 18 0,46 0,12 15
dorso-lateral rows
* Measurements in ^m. Mean - arithmetic mean, M - Median, Max - maximum, Min - minimum, SD - standard deviation, SE - standard error of mean.
Fig. 1. Strombidium nabranicum sp. n. A - general view from ventral side; showing the collar and ventral adoral membranelles; B - nuclei (Feulgen reaction). Scale bar: 15 ^m.
Institute of Zoology National Academy of Sciences of Azerbaijan, Baku city. Accession number Nab. mar. N4. Dedication. Named after region found. Description. Size in vivo 60-80, after fixation 65 ^m. Body is conical. The peristomal field is confined to the 15 anterior (collar) and 14 ventral membranelles. Anterior membranelles each comprising 3 basal body rows with cilia up to 25 !m long. Ventral membranelles are distinctly different from anterior membranelles, the longest are about 12 ^m, the other gradually shortened.
The silverline system is unusual for Strombidium with a fine net of argyronems. The contractile vacuole is located at the posterior part ofthe body. Macronucleus is elongated (35 !m) with numerous nucleoli and a single spherical micronucleus.
Discussion. The Strombidium genus has been actively investigated over the past 20 years (Montagnes et al., 1988, 1990; Petz and Foissner, 1992; Alekperov and Mamaeva, 1992; Lynn and Gilron, 1993; Petz, 1994).
Our Strombidium nabranicum sp. n. differs from all the remaining species of the genus by its unusual multiple silverline system. It is possible that future examination will show that separation at the genus level is very likely to be appropriate.
Euplotes alatus Kahl 1932 (Table 1; Fig. 2, A-C).
This is a very rare species and as far as we know, there was only one modern reinvestigation of E. alatus using silver impregnation (Borror, 1968). For the fauna of the Caspian Sea it is its first record.
The size of living specimens is 30-45 ^m; after fixation up to 30 ^m. Body is oval and flattened dorso-ventrally. Adoral zone of membranelles contains 40-45 elements and is located on the left and anterior margins. There are 10 fronto-ventral cirri, five transventral and four caudal cirri. On the dorsal side 8 dorsal kineties are located. Two of them can be seen from the ventral side. Each dorsal kinetic row contains 12-18 cilia. Dargyrom - type II "eurystomus".
A contractile vacuole is present at about the level of the transverse cirri. Cytoplasm is colorless with some food vacuoles.
There are several Euplotes species with dargyrom of "double eurystomus" and 10 frontoventral cirri (Table 2).
Fig. 2. Euplotes alatus Kahl 1932. A - ventral side; B - dorsal side (impregnation by silver nitrate); C -nuclei (Feulgen reaction). Scale bar: 15 ^m.
Fig. 3. Comparison of some different populations Euplotes corsica, E. alatus and E. balteatus:
A - Euplotes corsica (Berger and Foissner, 1989), a - ventral side, b - dorsal side; B - Euplotes alatus, Caspian population (present paper), a - ventral side, b - dorsal side, c - nuclei; C - Euplotes alatus, Atlantic population (Borror, 1968), a - ventral side, b - dorsal side, c - "dargyrom"; D - Euplotes balteatus, Antarctic population (Song and Wilbert, 2002), a - ventral side, b - dorsal side; E - Euplotes balteatus, Caspian population (Agamaliev, 1983), a - ventral side, b - dorsal side, c - nuclei; F - Euplotes balteatus, fresh-water population (Alekperov, 1983), a - ventral side, b - dorsal side. Scale bars: A, C, F - 20 ^m, B - 15 ^m, D - 30 ^m, E - 10 ^m.
Table 2. Comparison of some small, morphologically-related marine Euplotes species with dargyrom of
"double eurystomus" and 10 frontoventral cirri.
Species Body size AZM number Fronto- ventral cirri Transversal cirri Caudal cirri Dorsal kineties number Number of basal body pairs in the dorsal rows References
E. balteatus 45-50 35-40 10 5 4 7 13-14 Alekperov, 1983
E. balteatus 40-70 27-33 10 5 2+2 * 8-10 11 Song and Wilbert, 2002
E. alatus 20-30 40-45 10 5 4 8 12-15 Present paper
E. alatus 36-43 Probably 30 10 5 4 8 10-11 Borror, 1968
E. corsica 29-42 22 10 5 3-4 7-8 6-9 Berger and Foissner, 1989
* Song and Wilbert (2002) differs two caudal and two marginal cirri.
Fig. 4. Euplotes khazarica sp. n. A - ventral side; B - dorsal side and nuclei (impregnation by silver nitrate). Scale bar: 25 ^m.
According to Song and Wilbert (2002) Euplotes alatus Kahl 1932 is possibly a junior synonym of E. balteatus Dujardin 1842.
In Fig. 3 we show 3 populations of E. balteatus, described from different regions and different water salinity. In our opinion all this Euplotes balteatus populations clearly differs from Euplotes alatus, described by Borror (1968) and at the present paper in the shape and size of the body and arrangement of fronto-terminal cirri, especially on the frontal part. That is why we agree with Borror (1968) that E. balteatus is really different from E. alatus in cirrus pattern and the shape of its buccal overture and that is why E. alatus appears to be valid separate species.
In our opinion species E. corsica described by Berger and Foissner (1989) is very probably conspecific with the E. alatus Kahl 1932 and differs shape and size of the body and the number of dorsal rows. These two species (E. corsica and E. alatus) has more similarity, than Euplotes balteatus.
Euplotes khazarica sp. n. (Table 1; Figs 4, A-B; 5, C-D).
Diagnosis. Size of living cells is 40-55 ^m, after fixation - up to 35 ^m. Body oval, flattened dorsoventrally. Adoral zone of membranelles contains 45-50 elements and occupies the left margin of the ventral side. There are 11 frontoterminal cirri: near two of them which locate upper 5 transversal cirri there is small unciliated argentophilic plate. Four caudal cirri. Ventral argyrom fine with small argyroconts with polygonal shapes. On the dorsal side there are five ribs with 5 dorsal kineties with 18-19 cilia. Dargyrom - type E. "muscicola"III.
Endoplasm is clear and uncolored. Macronucleus C-like with small ledge. A spherical micronucleus is located nearby.
Type location. This species was found in the Caspian Sea plankton near Nabran village coast (Not far from Azerbaijan-Russia border).
Type specimens. A holotype and a paratype of E. khazarica sp. n. as two slides of silver nitrate impregnated cells have been deposited in the collection of the Institute of Zoology NAS of Azerbaijan. Accession number Nab.mar. N8.
Discussion. There have been many new descriptions and redescriptions of the representatives of Euplotes genus published in recent years (Dragesco and Dragesco--Kerneis, 1986; Berger and Foissner, 1989; Hill et al., 1986; Augustin and Foissner, 1989; Agatha and Wilbert, 1990; Valbonesi and Luporini, 1990a, 1990b; Al-Rasheid, 2001; Song and Wilbert, 2002).
According to Borror (1968) the basis for identification of member of Euplotes genus are:
1. cortical sculpturing;
2. arrangement of all ciliary organelles, including dorsal and endoral cilia;
3. details of the silverline system.
Euplotes khazarica sp. n. described above differs from other representatives ofthis genus by its maximal number of frontoventral cirri - 11 and minimal number of dorsal cilia rows. From E. trisulcatus Kahl 1932, E. khazarica differs in body shape, with a much longer adoral zone of membranelles, smaller on two number of dorsal rows and other type dargyrom.
Dedication. Named after ancestral Caspian Sea name (Khazarian Sea).
M M JUZ Æ. V V m» " 4 JÏ Il * MIB '/ W * f'/ \ v r* JJ I ê .ß.
I^ /v Y •> % V ' - •- W % _ ' ' . v /jSSSlL • • j1 4 ^ T ‘ r; *: if: -i
Fig. 5. Silver impregnation of Strombidium nabranicum sp. n. and Euplotes khazarica sp. n. A - Strombidium nabranicum, ventral surface showing ventral adoral membranelles; B - S. nabranicum, dorsal surface with somatic kinetic rows and silverline system; C - Euplotes khazarica, ventral side; D - E. khazarica, dorsal side. Scale bars: AB - 15 ^m, C-D - 25 ^m.
Acknowledgements
The study was supported by the "CRDF Azerbaijan - US Bilateral Grants Programs" Project N 3100.
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Address for correspondence: Ilham Alekperov. Laboratory of Protistology, Institute of Zoology, Azerbaijan National Academy of Sciences, Baku, 370073 Azerbaijan. E-mail: [email protected]
Editorial responsibility: Sergei Fokin
