Bull. Natl. Mus. Nat. Sci., Ser. B, 37(3), pp. 113–115, August 22, 2011

Transfer of Cymbella koidzumiana Skvortsov to the genus Navicula
Akihiro Tuji
Department of Botany, National Museum of Nature and Science,
Amakubo 4–1–1, Tsukuba, Ibaraki 305–0005, Japan
E-mail: tuji@kahaku.go.jp(Received 13 May 2011; accepted 22 June 2011)

Abstract Cymbella koidzumiana Skvortsov is transferred to Navicula. Cymbella hybrida
Grunow reported by Skvortsov from Japan is considered to be identical with this taxon.
Key words : Cymbella hybrida, Navicula alisoviana, Navicula koidzumiana, new combination.

Introduction
B. V. Skvortsov (=B. W. Skvortzow) reported
Cymbella hybrida Grunow from several lakes inJapan (Skvortzow, 1936a, b, 1937). However, thematerial used in the reports does not agree with
the isotype individual of C. hybrida presented by
Krammer and Lange-Bertalot (1986, fig. 145: 3).
Furthermore, it differs from the form of Navicula
viridula var. linearis and N. viridula var. slesvicensis (as N. slesvicensis Grunow) presented in
Krammer and Lange-Bertalot (1986).
Tuji (2003) considered that the taxon was
Navicula viridula var. alisoviana Skortzov andmade a new combination, Navicula alisoviana(Skvortsov) Tuji, for this taxon. However, after
the publication, I found that Cymbella koidzumiana described by Skvortsov in Skvortsov andNoda (1971) agrees with Navicula alisoviana(Skvortsov) Tuji. C. koidzumiana has a priority
for Navicula alisoviana in species rank. Therefore, Cymbella koidzumiana Skvortsov is transferred to Navicula.
Materials and Methods
The material used in Skvortzow (1936a) is an
isotype material for C. koidzumiana. Raw material from Lake Kizaki (TNS-AL-55512m in TNS),
thought to be isotype material of Skvortzow’s(1936a) earlier collection (Tuji, 2003; Tuji andWilliams, 2006), was used to examine specimensof C. koidzumiana.
The Raw material from Lake Biwa (TNS-AL53965m in TNS), thought to be an isotype material of Skvortzow’s (1936b) earlier collection(Tuji 2002), and a material (TNS-AL-54418 inTNS) from Lake Biwa used in Tuji (2003) werealso examined for this taxon.
Results and Discussion
Navicula koidzumiana (Skvortsov) Tuji, comb. nov.
Basionym: Cymbella koidzumiana Skvortsov inSkvortsov and Noda, Sci. Rep. Niigata Univ.,
Ser. D. (Biology). 8: 20. pl. 3. f. 9. 1971. Type
locality: Lake Kizaki, Nagano Pref., Japan.
Holotype slide: unknown.
Cymbella hybrida Grunow sensu Skvortzow,
Philipp. J. Sci. 61: 49. pl. 5. f. 23. 1936.
Navicula viridula var. alisoviana Skvortsov,
Mem. South. Ussuri Branch State Russian Geogr.
Soc. 22. Pl. 4, f. 22, syn. nov. Navicula alisoviana (Skvortsov) Tuji sensu Tuji, Bull. Natn.
Sci. Mus., Tokyo, Ser. B 29: 67, 2003.
Distribution and ecology: Lake Kizaki(Skvortzow, 1936a as C. hybrida), Lake Biwa
(Skvortzow, 1936b as C. hybrida), Lake Ikeda(Skvortzow, 1937 as C. hybrida). Probably
epipelic in large lakes.

114

Akihiro TujiFigs. 1–5. Navicula koidzumiana (Skvortsov) Tuji. 1. Original illustration of Cymbella hybrida Grunow in
Skvortzow (1936a) from Lake Kizaki. 2. Original illustration of Cymbella koidzumiana Skvortsov in
Skvortsov and Noda (1971: plate 3, figure 9). 3, 4. LM. Newly taken sample from south basin of Lake Biwa
(TNS-AL-54418 in TNS). 5. SEM. Original material of Skvortzow (1936b) from Lake Biwa (TNS-AL53965m in TNS).

Transfer of Cymbella koidzumiana Skvortsov to the genus Navicula

Raw material: ? TNS-AL-55512 in TNS (Department of Botany, National Museum of Natureand Science) (see Tuji and Williams, 2006).
Although twenty slides from the isotype material (TNS-AL-55512) have been examined, nosuitable specimens was found in these slides.
Skvortsov described many rare taxa in his publications. However, it is very difficult to find thesetaxa in newly made isotype slides (Tuji pers.
obs.).
The individuals from the south basin of Lake
Biwa (Tuji, 2003, Figs. 8, 9 as Naviculaalisoviana) (Figs. 3, 4) and the SEM micrographtaken from the Skvortzow’s material from Lake
Biwa (Fig. 5) agree with N. koidzumiana in its
outline, but slightly wider (10 and 11 m m) andmore coarse density of striae (7 and 8 per 10 m m)than the orignial descripton of this taxon (width:8.5 m m, striae 9 per 10 m m). Since this taxon israre and the morphological variation of this taxon
is not clear, I identified these individuals as N.
koidzumiana in this paper. It might be a different
variety of this species, and further study shouldbe needed.
Navicula koidzumiana is very similar to Cymbopleura hybrida group (Krammer, 2003) invalve outline and circled and large central area,
but it differs by the ?-shape raphe distal ends.
This taxon should not belong to Cymbella group,
but to Navicula viridula species complex.
The illustration of N. koizumiana (Fig. 2)
seems to be different from that of Cymbella hybrida (Fig. 1). However, the size “lg. 68 micr. lt.
85 micr.” in Skvortsov and Noda (1971) and“Length, 0.068 mm; breadth, 0.0085” in Skvortzow (1936a) and density of striae “9 in 10 micr.”
in Skvortsov and Noda (1971) and “9 in 0.01 mm”
in Skvortzow (1936a) are completely identical inboth species. The difference between the illustrations of both species is probably due to the over-115

simplification of the illustrations in Skvortsov
and Noda (1971).
Navicula koidzumiana is also similar to N.
viridula species complex including N. viridula(Kütz.) Ehrenb., N. rostellata Kütz. and N. rhynchocephala Kütz. However, N. koidzumiana islarger and having more coarse striae density thanother similar taxa.
References
Krammer, K. 2003. Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella. 530 pp. In:
Lange-Bertalot, H. (ed.), Diatoms of Europe. Vol. 4. A.
R. G. Gantner Verlag K.G., Ruggell.
Krammer, K. and Lange-Bertalot, H. 1986. Süßwasserflora von mitteleuropa. Bacillariophyceae. 1. Teil: Naviculaceae. 876 pp. In: Ettl, H., Gerloff, J., Heynig, H. andMollenhauer, D. (eds.), Süßwasserflora von Mitteleuropa 2 (1). G. Fischer, Stuttgart and Jena.
Skvortzow, B. W. 1936a. Diatoms from Kizaki Lake,Honshu Island, Nippon. Philippine Journal of Science
61: 9–73, 16 pls.
Skvortzow, B. W. 1936b. Diatoms from Biwa Lake, Honshu Island, Nippon. Philippine Journal of Science 61:253–296, 8 pl.
Skvortzow, B. W. 1937. Diatoms from Ikeda Lake, Satsuma Province, Kiusiu Island, Nippon. Philippine Journal of Science 62: 191–218, 5 pls.
Skvortsov, B. V. and Noda, M. 1971. On recent and fossil
freshwater diatoms from Japan II. Science Reports ofthe Niigata University, Biology Series D 8: 13–27, pl.
2–3.
Tuji, A. 2002. Observations on Aulacoseira nipponica
from Lake Biwa, Japan, and Aulacoseira solida fromNorth America (Bacillariophyceae). PhycologicalResearch 50: 313–316.
Tuji, A. 2003. Freshwater diatom flora in the bottom sediments of Lake Biwa (Sough Basin): Navicula sensu
lato. Bulletin of the National Science Museum, Series
B 29: 65–82.
Tuji, A. and Williams, D. M. 2006. The identity of Cyclotella glomerata Bachmann and Discostella nipponica (Skvortzov) Tuji et Williams comb. et stat. nov.
(Bacillariophyceae) from Lake Kizaki, Japan. Bulletinof the National Science Museum, Series B 32: 9–14.