Redescriptions of Euplotes encysticus and E. rariseta (Protist: Ciliophora: Euplotida)
Author
Kim, Eun-Hee
Department of Environment and Energy Engineering, Kyungnam University, Changwon 51767, Republic of Korea & W & S Ecosystem Assessment Institute, Masanhappo-gu, Changwon 51745, Republic of Korea
Author
Lee, Won Je
Department of Environment and Energy Engineering, Kyungnam University, Changwon 51767, Republic of Korea
wonje@kyungnam.ac.kr
text
Journal of Species Research
2019
8
1
128
135
journal article
10.12651/JSR.2019.8.1.128
2713-8615
8120462
1.
Euplotes encysticus
Yonezawa, 1985
(
Figs. 1
a-d, 2, 3)
Material examined.
Korea
: Dokdo (
37°14
ʹ
22
ʺ
N
,
131° 52
ʹ
08
ʺ
E
),
27 September 2017
, from a freshwater pond (Mulgol), collected by
Jong Soo Park.
Type
strain, live cells are kept with the
Korean Culture Collection of Protists
,
Kyungnam University
,
Korea
, reference ‘KF403’.
Fig. 3.
Micrographs of excystment of
Euplotes encysticus
.
(a) Cyst of cell 1, (b-j) time series lasting 6 minutes 52 seconds documenting excystment of cell 2, (i) empty cyst and trophozoit, (j) trophozoit. All images are DIC images. Scale bar in (j) = 25 μm.
Description.
Cells are 63-79 × 41-61 μm in vivo and 44-56 × 28-38 μm in protargol, asymmetrically oval with posterior portion slightly wider than anterior, and dorso-ventrally flattened. The peristome is narrow and extremely long, extending approximately 72% of cell length and surrounded by 31-36 adoral membranelles. Adoral zone of membranelles (AZM) curved (
Figs. 1a, 1b
,
2a, 2d, 2f
). Cytoplasm colourless, often filled with many light reflecting granules and few food vacuoles (
Fig. 2a
). Single contractile vacuole located to right of transverse cirri (TC) (
Fig. 2a
). Seven dorso-lateral ridges (
Figs. 2b
, arrowheads; 2e). Dorsal kineties (DK) inserted in concaves down the ridges (
Figs. 1c
,
2e
). The kinetosome number of the mid-dorsal kinety is 19- 22. Cirri usually strong; 9 fronto-ventral, 5 transverse, 2-3 (mostly 2) caudal and 2 left marginal cirri. Paroral membrane (PM) about 10 μm long. Macronucleus (Ma) usually C-shaped, with the anterior and posterior ends sometimes curving (
Figs. 1d
,
2d, 2f
). Micronucleus (Mi) small, nearly spherical and located in the upper right half of the macronucleus (
Figs. 1b, 1d
,
2d
). The cells are capable of encystment and excystment (
Fig. 3
). Move by crawling on crumb or substrate.
Remarks.
Euplotes encysticus
was originally reported by
Yonezawa (1985)
as a freshwater form. We performed the inoculation of our strain KF403 into well plates containing seawater (15 and 30 psu) with barley grains. The strain grew well in the seawater, thus this species is adaptable to both seawater and freshwater. Our observations are in accord with those of
Yonezawa (1985)
and
Fan
et al.
(2010)
.
Euplotes encysticus
is very similar to
E. muscorum
in general appearance, but according to several researchers (e.g.,
Dragesco, 1970
; Dragesco and Dragesco Kernéis, 1986;
Jo and Shin, 2003
) they can be distinguished from each other because (1) no cyst has been observed so far in
E. muscorum
, (2) the obvious dorsal-lateral ridges and the granules surrounding the dorsal cirri have not observed in
E. muscorum
, (3) the AZM of
E. encysticus
outspreads more broadly than that of
E. muscorum
, and (4) the AZM covers 3/4 body length in
E. encysticus
, and 2/
3 in
E. muscorum
. Our strain has all of these characters specific to
E. encysticus
. Additionally, these two species are clearly distinguished by the differences in their 18S rRNA gene sequences, of which
E. encysticus
differs from
E. muscorum
by 2.04% (
Fan
et al.
, 2010
).
Euplotes encysticus
is similar to
E. petzi
,
E. roscoffensis
and
E. sinicus
in cell length, but the numbers of AM, DK and dikinetids in mid-DK in
E. encysticus
are higher than those in
E. petzi
.
Euplotes roscoffensis
and
E. sinicus
have higher number of AM than that of
E. encysticus
(
Tables 1
,
2
).
Euplotes sinicus
has 11-16 dikinetids in mid-DK (vs 5-7) (
Tables 1
,
2
).
NCBI BLASTN search result shows that the closest strains to our strain KF403 are
E. encysticus stains
[GenBank Accession Nos. FJ346569, EF535728, LN864512; Identity 99%]. The 18S rRNA sequence of our stain is 1,663 bp in length.
Habitat.
Marine and Freshwater
d e f
Fig. 4.
Micrographs of
Euplotes rariseta
strain KM401 (a-c) in vivo and strain KM444 (d-f) after protargol impregnation. (a) Dorsal ridges (arrowheads) of
E. rariseta
, (b) ventral view showing longitudinal ridges (arrowheads), (c) ventral view showing FVC and TC, (d) ventral view showing AZM (adoral zone of membranelles), FVC (fronto-ventral cirri), TC (transvers cirri), PM (paroral membrane), (e) dorsal view showing dorsal kineties, (f) ventral view showing ventral kineties and Ma (macronucleus). Scale bars in (c) for (a-c) represent 20 μm and in (f) for (d-f) represent 10 μm.
Distribution.
Freshwater habitats:
Korea
(Dokdo, this study),
Japan
(
Yonezawa, 1985
) Marine habitats:
China
(Daya Bay,
Fan
et al.,
2010
)
Deposition.
National Institute of Biological Resources,
Korea
(NIBRPR0000109440)
NCBI GenBank Accession Number
: MK026950