Bull. Natn. Sci. Mus., Tokyo, Ser. B, 32(1), pp. 9–14, March 22, 2006

The Identity of Cyclotella glomerata Bachmann and Discostellanipponica (Skvortzov) Tuji et Williams comb. et stat. nov.
(Bacillariophyceae) from Lake Kizaki, Japan
Akihiro Tuji1 and David M. Williams2
1

Department of Botany, National Science Museum,
Amakubo 4–1–1, Tsukuba, 305–0005 Japan
E-mail: tuji@kahaku.go.jp
2
Department of Botany, The Natural History Museum,Cromwell Road, London SW7 5BD, U.K.

Abstract Type material of Cyclotella glomerata Bachmann and seven recently collected samples
were examined to establish the identity of this species. C. glomerata has a central rimoportula at
the central area of the valve face and forms colonies; several marginal fultoportulae occur on theribs. Thus, this taxon is not a member of the new genus Discostella, which includes the Cyclotellastelligera group, but is similar to other species in Cyclotella.
In addition, isotype material of C. glomerata f. nipponica Skvortzov was examined. It does notshare significant characters with C. glomerata but has characters that place it in Discostella. Thus,
we propose the new combination Discostella nipponica (Skvortzov) Tuji et D. M. Williams.
Key words: Cyclotella glomerata f. nipponica Skvortzov, Discostella nipponica (Skvortzov) Tujiet D. M. Williams, Cyclotella glomerata Bachmann, Discostella glomerata (Bachmann) Houk,
Wolfgangsee

Introduction
Cyclotella glomerata Bachmann was first described by Bachmann (1911) from Zugersee (TheLake of Zug), Switzerland. This taxon has beenreported worldwide as a planktonic species (e.g.
Krammer & Lange-Bertalot 1991, Tuji & Houki
2001, Houk & Klee 2004). Krammer & LangeBertalot (1991) described this taxon as part of
the “Cyclotella stelligera sippen complex”. Tuji& Houki (2001) reported this taxon from Lake
Biwa, illustrated with an SEM, suggesting that it
was a member of the “Cyclotella pseudostelligera group”. Recently, Houk & Klee (2004) transferred this taxon to the new genus Discostella
Houk et Klee, which included the Cyclotella stelligera group. All previous reports of Cyclotella
glomerata have included it in the Cyclotella stelligera / pseudostelligera group.
Bachmann’s original figures (1911: Figs
106–108) and the illustrations offered by Krammer & Lange-Bertalot (1991: Taf. 49), depict

specimens in colonies of many cells. Since thedescriptions of species placed in the genus Discostella have no central rimoportulae nor do they
form colonies, this leaves problems with the inclusion of C. glomerata in Discostella.
In addition, Skvortzow (1936) described theform C. glomerata f. nipponica Skvortzov fromLake Kizaki, Japan. Skvortzov’s original illustration is too simple to be certain of its identity andhis name has not been used in any floral reports
from Japan.
In this study, we have examined specimensfrom Bachmann’s type slide of C. glomerata,
Hustedt’s slides, and several recently collected
samples, from Wolfgangsee, Austria, and isotype
material of C. glomerata f. nipponica, in an attempt to clarify the taxonomy of C. glomerata.
Materials and Methods
A slide prepared by Bachmann from Zugersee,
the type locality of Cyclotella glomerata, and la-10

Akihiro Tuji and David M. Williams

belled AC2/57 in BRM was examined. Anotherslide from Zugersee labelled 136/07 as well as
raw material (E1305, Meister 589, from BRM;
material collected by Meister on 3rd May 1906)
were examined. The slides in BRM with specimens of Cyclotella glomerata, numbered AC1/20
and AC1/21 and prepared by Hustedt from Wolfgangsee material, were also examined. Further,six samples (TNS-AL-55781–55784, 55789–55790 in TNS) collected from Wolfgangsee byA.Tuji on 15th–18th August 2005, were used for
SEM and LM observation of C. glomerata.
Raw material from Lake Kizaki (TNS-AL55512 in TNS), thought to be isotype material of
Skvortzov’s (1936) earlier collection (Tuji 2002,Ohtsuka & Tuji 2002), was used to examine
specimens of C. glomerata f. nipponica Skvortzov.
Results
Specimens of two taxa from Cyclotella (orDiscostella) were observed in slide AC2/57 (pl. 1figs. 1, 3-6), collected from Zugersee (the type
locality of C. glomerata) and Hustedt’s slide
AC1/20 and AC1/21 (pl. 1 fig. 2) from Wolfgangsee. Specimens of one taxon have a circular
central pattern with a central fultoportula (pl. 1fig. 3), the other has a ring and stelligeloid central pattern with no central fultoportulae (pl. 1fig. 4). Both taxa are easily distinguished using
the central pattern and the existence of central
fultoportula(e). The taxon with the central fultoportula agrees with the original description of C.
glomerata and can be identified as such.
The individuals in the slides, AC2/57 (pl. 1figs. 1, 3–6), AC1/20, AC1/21 (pl. 1 fig. 2),136/07 (pl. 1, figs. 7–9) and TNS-AL-55790sa(pl. 1 figs. 10–17), all share the similar dimensions of cell size, density of striae, the form ofcentral area, the possession of one to several
small central fultoportula and the character ofcolony formation characteristics (pl. 1, figs. 1, 2,17) that can be observed on the micrograph in
Krammer & Lange-Bertalot (1991: Taf. 49, fig.
11), except for two points. The figure in Kram-

mer & Lange-Bertalot (1991) were from Wolfgangsee (AC1/20 in BRM). The individuals in
slide 136/07 do not appear to form colonies—although it is possible that they could be destroyed
during the cleaning process. Colonies were notobserved in recently collected material after they
were subjected to the cleaning process. The cellsize of individuals in the slide 136/07 and TNSAL-55790sa are larger than others, but the dimensions overlap. The ultra-structure of the individuals in TNS-AL-55790 from Wolfgangsee
also agree in their main features with the structure of specimens from a slide 136/07 and a material E1305 from Zugersee.
A description is as follows: cells 3–10 m m indiameter, 2.5–4.5 m m in depth, attached at thevalve face, forming colonies with few to manycells (pl. 1 figs. 1, 2, 17). In SEM, one small central fultoportula with two pore covers and cowlings, are present in each valve (pl. 2 figs. 1–6).
Marginal fultoportulae, also with two pore covers
and cowlings, exist close to the valve ends and at
the end of every three to four ribs (pl. 2 figs. 2, 3,6). The ribs on the marginal fultoportulae are
more depressed than the other ribs (pl. 2 figs.
2–4). Rimoportulae occur on the valve face,close to valve face/mantle junction (pl. 2 fig. 4).
C. glomerata f. nipponica is rare in the isotype
material from Lake Kizaki. The specimens thatwere found had cells of 3–4 m m in diameter, withstriae 18 in 10 m m (pl. 3 figs. 1–7). The specimens occur only as unicells, not in colonies. No
central fultoportula was observed in the SEM, although marginal fultoportulae, with long tubes
and two cowlings, occur at the valve face/mantle
junction (pl. 3 figs. 6–7). The ribs branch on thevalve face, while they strongly branch on themantle. A small sessile rimoportula occurs on thevalve/mantle junction (pl. 3 figs. 1–7).
Discussion
It seems appropriate to designate BRM slide
AC2/57 from Zugersee as lectotype for Cyclotella glomerata Bachmann.
Our observations show that C. glomerata

The Identity of Cyclotella glomerata and Discostella nipponica

forms colonies, has one to three central fultoportulae with marginal fultoportulae occurring on
the ribs, observations supported by the original
figures presented by Bachmann (1911). Thesecharacters are not part of the genus Discostella
as described by Houk & Lee (2004). The SEM
image of C. glomerata presented by Houk & Lee(2004: fig. 114) is not of C. glomerata.
We designate as lectotype for C. glomerata f.
nipponica Skvortzov an individual on the slide
TNS-AL-55512sl in TNS, made from isotype
material; TNS-AL-55512. The designated lectotype agrees with the characters of a taxon identified as C. glomerata by Japanese diatomists (e.g.
Tuji & Houki, 2001). Since its characters are of
the genus Discostella and that it differs considerably from C. glomerata f. glomerata, we propose
the new combination Discostella nipponica.
Taxonomic Conclusions
Cyclotella glomerata Bachmann Mitt. Naturfor. Ges.
Luzern 6: 131. f. 106–108, 1911.
(pl. 1 figs. 1–3, 5–17, pl. 2 figs. 1–5)
Lectotype (designated here): An individual in AC2/57 in
BRM. (pl. 1 fig. 1(arrow), fig. 2).
Synonym: Discostella glomerata (Bachmann) Houk etKlee, Diatom Res. 19: 220. 2004.
non: Discostella glomerata sensu Houk et Klee, Diatom
Res. 19. f. 114. 2004.
Cyclotella glomerata sensu Tuji & Houki 2002.
Discostella nipponica (Skvortzov) Tuji et D. M. Williams,
comb. et stat. nov.
(pl. 3 figs. 1-7)
Basionym: Cyclotella glomerata Bachmann f. nipponica
Skvortzov, Philippine J. Sc. 61: 13. pl. 1. f. 12, 1936.
Lectotype (designated here): An individual in TNS-AL-1155512sl in TNS (pl. 3. f. 1–3). England finder: L19.
Isotype (type material): TNS-AL-55512 in TNS.
Type locality: Lake Kizaki, Nagano Pref., Japan.
Synonym: Cyclotella glomerata sensu Tuji & Houki 2002.

Acknowledgements
We extend our thanks to Richard Crawford andFriedel Hinz of the Friedrich Hustedt Study Centre for Diatoms, Alfred Wegener Institut furPolar—und Meeresforschung (BRM) for help intheir herbarium and the gift of specimens.
ReferencesBachmann, H. 1911. Das Phytoplankton des Süsswassers
mit besonderer Berüchsichtigung des Vierwaldstättersees. 213p 15 pls. (col.), text ill 8 pp.
Houk, V. & Klee, R. 2004. The stelligeroid taxa of thegenus Cyclotella (Kützing) Brébisson (Bacillariophyceae) and their transfer into the new genus Discostella gen. nov. Diatom Research, 19: 203–28.
Krammer, K. & Lange-Bertalot, H. (eds.) 1991. Bacillariophyceae. 3. Teil: Centrales, Fragilariaceae, Eunotiaceae. Gustav Fischer Verlag, Jena.
Ohtsuka, T. & Tuji, A. 2002. Lectotypification of somepennate diatoms described by Skvortzow in 1936 fromLake Biwa. Phycological Research, 50: 243–9.
Skvortzow, B. W. 1936. Diatoms from Kizaki Lake, Honshu Island, Nippon. Philippine Journal of Science,
61: 9–73, 16 pl.
Tuji, A. 2002. Observations on Aulacoseira nipponica
from Lake Biwa, Japan, and Aulacoseira solida from
North America (Bacillariophyceae). Phycological Research, 50: 313–6.
Tuji, A. & Houki, A. 2001. Centric diatoms in Lake Biwa.
Lake Biwa Research Institute, Otsu, 90 pp.

12Akihiro Tuji and David M. Williams

Plate 1. 1–3, 5–17. Cyclotella glomerata Bachmann. LM. 4. Discostella sp. 3–17. Bar10 m m. 1, 3–6. AC2/57
in BRM, specimens collected from Zugersee. 1. arrow and 3: lectotype, designated here. 2. AC1/21 in BRM,specimens collected Wolfgangsee. 7–9. 136/07 in BRM, specimens collected from Zugersee. 10–17. TNSAL-55790sa in TNS, specimens collected from Wolfgangsee.

The Identity of Cyclotella glomerata and Discostella nipponica

Plate 2. 1–6. Cyclotella glomerata Bachmann. SEM. 1-3. TNS-AL-55790 in TNS, specimens collected fromWolfgangsee. 1–2. Bar2 m m. 3. Bar0.5 m m. 4–6. E1305 in BRM, specimens collected from Zugersee. 4.
Bar2 m m. 5, 6. Bar1 m m. 1, 4, 5. External view of valve face. 2–3, 6. Inner view of valve face showing
valve face fultoportulae, marginal fultoportulae on the ribs and the rimoportula on valve face close to valve
face/marginal junction.

13

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Akihiro Tuji and David M. Williams

Plate 3 1–7. Discostella nipponica (Skvortzov) Tuji et D. M. Williams, comb. et stat. nov. 1–4. TNS-AL55512sl in TNS. Bar10 m m. LM. 1–3. Lectotype. 5–7. TNS-AL-55512 in TNS. SEM. Bar1 m m. 5. External view of valve face. 6–7. Inner view of valve face showing marginal fultoportulae on the rib and a rimoportula on valve face close to valve face/marginal junction; no valve face fultoportulae are evident.