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Morphology and Asexual Reproduction of Vitreochlamys aulata
，
(VolvocalesChlorophyceae)
Atsusi NAKAZAWA and Hisayoshi NOZAKI
Department of Biological Sciences，Gr aduate School of Science，Un iversity of Tokyo，
Hongo，Bu nkyo-ku，To kyo，11 3-0033 JAPAN
(Received on May 28，1 999)
The vegetative morphology and asexual reproduction of the unicellular green
alga Vitreochlamys aulata (Pascher) Batko (= Sphαerellopsis aulata (Pascher) Gerloff)
collected in Kanagawa Prefecture were observed in detail under controlled labora-
tory conditions. Although the vegetative morphology of the Japanese V. aulata ma-
terial agreed with that described by Pascher (1927)，Et tl (1963)，a nd Batko (1970)，
the mode of flagellar formation in newly formed daughter cells differed from that
observed__by Batko (1970). This is the first report on V. aulata from Japan.
Key words: asexual reproduction，C hlorophyceae，m orphology，S haerellopsis，
Vitreochlamys aulata
Vitreochlamys Batko (1970) (Chlamy- Jap anese strains of V. aulata.
domonadaceae，V olvocales，C hlorophyceae)
is au nicellular green flagellate character- Materials and Methods
ized by having as mooth，s wollen cell wall Soil samples used in this study were col-
separated from the protoplast (e.g.，E ttl lected from Tanasawa-paddyfields of Tokyo
1983). This taxon also appears in the litera- University of Agriculture，S himokawairi，
ture under the name Sphaerellopsis Atsugi-shi，K anagawa Prefecture in March
Korschikov (1925) (e.g.，I yengar and 1998. Clonal cultures (Sp'ha-4人Spha-5/，
Desikachary 1981，Et tl 1983，N ozaki 1991)， Spha-6/，a nd Spha-7/1998-39)were estab-
・・
a later homonym of the fungal genus lished by the pipette-washing method
Sphaerellopsis Cooke (1883). Batko (1970)， (Pringsheim 1946) from Petri dishes in
therefore，p roposed the nomen novum which as mall amount of the dried soil
Vitreochlamys for encompassing the algal sample and ab oiled pea (Pisum sativum)
genus Sphaerellopsis. were rewetted with distilled water. The cul-
Approximately twenty-three species of tures were grown in screw-cap tubes
this genus have been described worldwide， (18x150 mm) containing about 12 ml of AF-
mainly on the basis of differences in vegeta- 6 medium (Kato 1982) modified by the
tive morphology (Ettl 1983). Recently， elimination of CaC0and by the addition of
3 o
strains of V. aulata (Pascher) Batko were 400 mg/l MES，k ept at 20C，w ith alternat-
isolated from soils collected in Kanagawa ing periods of 14 hl ight and 10 hd ar!<: at a
Prefecture，Ja pan. This report describes the light intensity of about 150μmol/s/m-pro-
morphology and asexual reproduction of the vided by cool-white fluorescent lamps. Ob-
-42-
February 2000 Journal of Japanese Botany Vol. 75 No. 1 43
servations of vegetative cells were carried subovoid to ellipsoidal with ap ointed ante-
out using actively growing，5 -day-old cul- rior end，s ometimes developing ab eak- like
tures which had originated from inoculations anterior structure. Flagella were as long as
of cultures 4-6daysold. Light microscopy the cell length (Figs. 1，7 ). Two or three
四
was carried out using an Olympus BX50 mト contractile vacuoles were located near the
croscope equipped with Nomarski interfer- base of the flagella (Figs. 5，6) . Chloroplasts
ence opt1cs. were single and cup-shaped，w ith as ingle
basal pyrenoid (Figs. 1b， 2) ，s howing paral-
Observations lel longitudinal striations on the surface
Vegetative cells were solitary，bi flagellate (Figs. la，8 ). The stigma was single and
and broadly ellipsoidal to obovoid in shape nearly ellipsoidal，p ositioned near the
(Figs. 1，2) . The cell wall was swollen and middle of the cell (Figs. 1b ，3 ). The cells
separated from the surface of the protoplast were 10-27μm long and 9-22μm wide.
(Figs. 1，2 ，4 ，7 ). The protoplasts were The protoplasts were 9-24μm long and 9-
凶十
a
''.，
~
10J-lm
Fig. 1. Vegetative cell of Vitreochlamys aulatα(Pascher) Batko，s hown at the same mag-
nification. a. Surface view. Note the longitudinal striations on the chloroplast. b. Opti-
cal section.
44 植物研究雑誌第75巻第1号 平成12年2月
Figs. 2-13. Nomarski interference microscopy of the vegetative phase of Vitreochlamys aulata
(Pascher) Batko. Fig. 2. Optical sections of cells，s howing nucleus (N) and pyrenoid (P). Fig.
3. Surface view of cell，s howing stigma (S). Fig. 4. Median transverse section of cell，s how-
ing nucleus (N). Fig. 5. Top view of cell，s howing two contractile vacuoles (C) at the anterior
pole of the protoplast. Fig. 6. Top view of cell，s howing three contractile vacuoles (C) at the
anterior pole of the protoplast. Fig. 7. Cell with two f1agella (F). Fig. 8. Surface view of the
protoplast，s howing longitudinal striations on the chloroplast. Figs. 9-14. Asexual reproduc-
tion. All at same magnification. Figs. 9. First cell division. Note that the parental f1agella have
become detached from the cell. Fig. 10. Two-celled stage. Figs. 11. Second cell division. Fig.
12-14. Development of four daughter cells. Note new f1agella (F) of daughter protoplasts de-
veloping within the parental cell wall (arrowheads).
18μm wide. Asexual reproduction was ac- once (Figs. 9，1 0)，t wice (Figs. 11-14) or
complished by zoospore formation (Figs. 9- three times successively to form two，f our，
14). After the two flagella had become de- or eight daughter protoplasts，r espectively，
tached from the cell，t he protoplast divided within the parental cell wall. Each daughter
February 2000 Journal of Japanese Botany Vo .l75 No. 1 45
protoplast then grew two equal flagella and division is completed. In the present study，
secreted ac ell wall which soon became however，t he parental cell lost its flagella
swollen (Fig. 14). The daughter cells were just prior to the cell division (Fig. 9)，a nd
subsequently released from the parental cell new flagella developed only after successive
wall. divisions of the protoplast within the paren-
tal cell wall (Figs. 11-14). This disagree-
Discussion ment may have been due to the difference in
The vegetative morphology of the present the Vitreochlamys materials examined. How-
Ja panese alga agreed well with that of ever，d evelopment of the flagella of the
Vitreochlamys aulata reported by Pascher newly formed daughter cells within the pa-
(1927)，Et tl (1963) and Batko (1970) with rental cell wall in the present Ja panese
regard to the single basal pyrenoid，t he strains is essentially the same as in other
shape of the protoplast，a nd the parallellon- unicellular volvocalean species (see Ettl
gitudinal striations on the surface of the 1983).
chloroplast. Based on these features，V.
aulatαdiffers from other Vitreochlamys References
(Sphaerellopsis) species. In addition，ve geta Batko A. 1970. A new Dangeardia which invades
tive cells of V. aulαta sometimes show three田 motile Chlamydomonadaceous monads. Acta.
Mycologica. vol. VI. 2: 407-435.
contractile vacuoles near the base of the fla-
Cooke M. C. 1883. New American fungi，G revillea
gella (Ettl 1963，B atko 1970) (Fig. 6). This
12: 22-23.
situation may be one of the morphological Ettl H. 1963. Uber zwei Sphaerellopsis-Arten. Nova
diagnoses of this species. However，s ome Hedwigia 5: 255-262.
morphological differences were recognized 一一一 1983.Chlorophyta 1. Phytomonadia. In: Ettl H.，
between the Polish material of Batko (1970) GerIoff J. and乱1011enhauerD. (Eds.)，
Suswasserflora von Mitteleurpa，B d. 9. xiv+807
and the present Japanese strains of V. aulata.
pp. Gustav Ficher Verlag，S tuttgart.
According to Batko (1970)，th e cell was al- Iyengar M. O. P. and Desikachary T. V. 1981.
most spherical and the flagella were 11/2 Volvocales. xiv+524 pp. Indian Council of Agricul-
times longer than the cell length (including tural Research，N ew Delhi.
the cell wall). Ont he other hand，th e flagella Korschikov A. 1925. Beitrage zur Morphologie und
Systematik der Volvocales. 1. Russk. Arch.
in the present Japanese strains were nearly
Protistol. 4: 153-197.
as long as the cell，a nd the cells were obo-
Nozaki H. 1991. Order Volvocida France，1 894 (Or-
void with ab road anterior face. Whether der Volcales). In: Mizuno T. and Takahashi E.
such morphological differences should be (Eds.)，A n illustrated guide to freshwater zooplank-
treated as species diagnoses or intraspecific ton in Japan. pp. 463-485. Tokai Univ. Press，T o-
kyo.
variation remains to be determined on the
一一一， Ohta N.，M orita E. and Watanabe M. M. 1998.
basis of comparative morphology and/or
Toward an atural system of species in Chloro-
molecular phylogenetic analysis using a
gonium (Volvocales，C hlorophyta): ac ombined
large number of related strains of analysis of morphological and rbcL gene sequence
Vitreochlamys (see Nozaki et al. 1998). data. J. Phycol. 34: 1024ー1037.
Batko (1970) reported that in asexual re- Kato S. 1982. Laboratory culture and morphology of
Colacium vesiculosum Ehrb. (Euglenophyceae).
production of Vitreochlamys aulata each of
Jpn. 1. Phycol. 30: 63-67 (in Japanese with English
the daughter protoplasts bears two equal fla-
abstract).
gella even when the first division of the Pascher A. 1927. Die Suswasser-Flora Deutschlands，
parental protoplast is incomplete，a nd that Osterreichs und der Schweiz. Heft 4: Volvo-
these flagella of the daughter protoplast cales=Phitomonadinae. Flagellate IV=Chloro-
project through the parental cell wall until phyceae 1. vi+506 pp. Gustav Fischer，J ena.
46 植物研究雑誌第75巻第l号 平成12年2月
Pringsheim E. G. 1946. Pure Cultures of Algae. 119 pp. Cambridge University Press，L ondon.
中沢敦，野崎久義:日本新産種 Vitreochlamys
aulata (緑藻網，オオヒゲマワリ目)の形態と無性
生殖 (Pascher) Batkoを採取し，その栄養細胞の形態と
Vitreochlamys Batko (= Sphaerellopsis Korschikov) 無性生殖の過程を培養条件下で詳細に観察した.
は単細胞性の淡水藻で，緑藻網 (Chlorophyceae)， その結果，栄養細胞の形態は Pascher(1927)，Et tl
オオヒゲマワリ目 (Volvocales)，クラミドモナス手斗 (1963)及びBatko(1970)の記載と基本的に一致し
(Chlamydomonadaceae)に分類されている.筆者等 たが，無性生殖時における新しい鞭毛の形成様式
は最近神奈川県厚木市にある棚沢水田(東京農業 がBatko(1970)のそれと異なった.
大学)より日本新産種 Vitreochlamysaulata (東京大学大学院理学系研究科生物科学専攻)
