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SUMMARY

A number of rare or unknown desmid species wererevealed in samples collected from a range of aquatichabitats in Japan. In the present paper we describe onenew species of the family Desmidiaceae, Staurastrumtsukubicum sp. nov. and report the presence in Japanof two species, Staurastrum levanderi Grönbl. and Cos-marium dilatatum Lütkem. in Järnefelt et Grönblad,previously found only in Europe. One taxon, Euastrumenglerii Schmidle var. madagascariense Bourr. etManguin, is renamed as Euastrum biverrucosum nom.nov. et stat. nov. The morphology of these taxa wasstudied using light and scanning electron microscopyand their taxonomic affinities are discussed.

Key words: desmids, new findings, new species, Japan.

INTRODUCTION

In 1996–1998, planktonic samples were collected froma number of small artificial ponds situated in centralHonshu (Japan). Such eutrophic waterbodies, used forirrigation or recreation, are very common aquatic habi-tats in Japan. The phytoplankton was relatively poor interms of desmid species but in a few samples someunknown or rare species of the family Desmidiaceae,previously not recorded in this part of the world, werefound. Although these algae are characterized by small-sized cells, they possess pronounced morphologicalproperties that differentiate them from allied species.The morphology of these taxa was studied in both thenatural samples and cultures, using light and scanningelectron microscopy. In the present paper a new species,Staurastrum tsukubicum, is described and three desmidspecies are noted for the first time in Japan.

MATERIALS AND METHODS

Samples for the present investigation were collectedfrom May 1996 to July 1998 from small ponds andlakes situated in Ibaraki Prefecture and Kyoto city,Japan. Several formalin-fixed samples collected in July1997 in the neighborhood of Vladivostok city (Russia)were also examined.

Sampling localities

Sampling localities included: 1. Lake Semba, Mito city, Ibaraki Prefecture. An out-line of environmental conditions and some data on algalspecies composition of this eutrophic pond have beenpresented by Gontcharov and Ono (1997).2. A number of small (20–50 × 20–30 m), shallow(1–2 m deep) artificial ponds situated in various resi-dential areas of Tsukuba city and its vicinity, IbarakiPrefecture. All these waterbodies had poorly developedaquatic vegetation with Potamogeton ssp., Hydrilla ver-ticillata Cosp. and Nuphaeae sp.3. Kyoyochi pond at the Ryoanji Temple, Kyoto. A con-siderable part of this 12th century, small (70 × 40 m)reservoir was covered by Nuphaeae sp. and some sub-merged aquatics.4. Horisawa-ike. This medium-sized (500 × 400 m),old, shallow (1–2 m deep) artificial reservoir is situatedin the northern part of Kyoto city. Only a few patches ofNuphaeae sp. were observed in the pond.

The cultures were established by the micropipetwashing method (Pringsheim 1946) and cultured intubes containing 10 mL of C (Ichimura 1971) or CA(Ichimura and Kasai 1985) medium. The cultures wereestablished under a bank of cool fluorescent lamps ona cycle of 16:8 h L:D at 20°C with an incident irradi-ance of 40 µmol m–2 s–1.

For scanning electron microscopy (SEM), the algaewere treated with 2% glutaraldehyde in cacodylatebuffer for 2 h at room temperature and washed severaltimes with distilled water. Cells were then fixed with1% OsO4 in the buffer for 1 h, rinsed with distilledwater and dehydrated in an alcohol series. Finally thecells were dried at critical-point in liquid CO2. Sampleswere coated with gold and examined under HitachiS-4200 (Hitachi Ltd, Japan) or JEOL S-5800 electronmicroscopes (JEOL Ltd, Japan).

Phycological Research 1999; 47: 233–240

Rare and new desmids (Desmidiaceae, Chlorophyta)from JapanAndrey A. Gontcharov1* and Makoto M. WatanabeEnvironmental Biology Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-0053, Japan

*To whom correspondence should be addressed.Email: [email protected] from November 1999: Institute of Biology andSoil Science, Vladivostok-22, 690022, Russia. Email: [email protected] editor: S. Watanabe.Received 4 April 1999; accepted 14 June 1999.

Material was also fixed in 4% formaldehyde anddeposited at the Herbarium, Institute of Biology andSoil Science (VLA), Vladivostok, Russia. Clonal culturesof the species used for the SEM study were depositedat the Microbial Culture Collection of the National Insti-tute for Environmental Studies (NIES), Tsukuba, Japan.

RESULTS AND DISCUSSION

Cosmarium dilatatum Lütkem. in Järnefeltet Grönblad

As has been mentioned by Coesel (1989), C. dilatatumlinks the genera Cosmarium Corda ex Ralfs and Euas-trum Ehr. ex Ralfs. Traditional morphological char-acters, such as cell shape and pattern of cell wall

ornamentation, do not allow it to be placed objectively.Spine-like extended apical angles and an excavatedapex are typical for the species of Euastrum butalso occur in some taxa of Cosmarium. The similaritybetween representatives of these two genera is not rareand this taxonomic problem has been discussed byCoesel (1984) who applied SEM for the demarcationof problematic taxa. However, a broader survey of thepatterns of cell wall ornamentation in different desmidgenera is needed to define them on the base of thischaracter (Coesel and Delfos 1986).

The morphology of our specimens agrees well withthe diagnosis and illustrations of C. dilatatum (Järnefeltand Grönblad 1960; p. 150, table 1: 1–6). Their dimen-sions (length 8–10 µm, width 10–12.5 µm, width ofisthmus 3–3.5 µm) also correspond to those reported

234 A. A. Gontcharov and M. M. Watanabe

Figs 1–10. Light and scanning electron micrographs of Cosmarium dilatatum and Euastrum biverrucosum. 1–4 Scanning electron micro-

graphs of Cosmarium dilatatum from culture. 1. Face view of a cell with a smooth cell wall. 2,3. Cell with a rugose cell wall. 4. Ver-

tical view of a cell. 5–10. Light and scanning electron micrographs of Euastrum biverrucosum sp. nov. 5,6. Face and vertical views of

a cell from a natural sample. 7. Face view of a cell from culture. 8. Lateral view of a cell showing the pattern of granulation at the

lateral lobes. 9. Vertical view of a cell. 10. Detail of the apex showing a pore pattern at the apex.

in the taxon. A SEM study revealed a nearly smooth cellwall in this species (Figs 1,2). Some specimens boresomewhat rugose cell walls (Figs 2,3), comparable to thatof E. gayanum De Toni (Vyverman 1991). This feature isless pronounced in our alga and may be caused by theSEM preparation procedure. Nevertheless, both taxa havesimilar cell morphology and seem to be related.

Cosmarium dilatatum was found in several localitiesin Japan (ponds in Kyoto) and the Russian Far East(three lakes in the neighborhood of Vladivostok city).This is the first record of the nominal variety of thespecies outside Europe where it has been reportedonly a few times so far (Beijerinck 1926; Järnefeltand Grönblad 1960; Coesel 1989; Kouwets 1998). Theonly infraspecific taxa of the species, var. concavum(Sieminska) Kouwets, was described from the USA(Sieminska 1965), but we regard the differencebetween this variety and Lütkemuller’s alga as minor.

According to Kouwets (1998) C. dilatatum preferslarge meso-eutrophic water bodies. In Japan, it wasfound among the plankton of a relatively small, artificialeutrophic ponds situated in Kyoto, but in Russia werevealed it only in periphyton samples collected inswampy mesotrophic lakes with diverse aquatic vegeta-tion and pH of 6.0–6.5.

Euastrum biverrucosum nom. nov.et stat. nov.

Synonym: E. englerii Schmidle var. madagascarienseBourr. et Manguin 1949, p. 184, pl. 2: 26 (basionym,original description and figure).

The specimens studied have subrectangular cells,the semicells are transversely quadrangular, the apicallobes are short and broad (Fig. 5), the apex truncate,the median notch shallow, opened, with granules at theangles of the notch; the apical angles are furnishedwith a short spine and small granules; the lateral lobesare truncate, furnished with marginal and intramarginalgranules around them; the face of a semicell with a pro-trusion furnished with three to five granules and twowarts above it. The semicells are subcircular in lateralview with marginal and submarginal granules, in verti-cal view oval, with a granulated protrusion and twowarts at each lateral side. Length 12.5–15 µm, width12.5–15 µm, breadth of isthmus 3–4 µm.

Study of the cell wall ornamentation of this algarevealed that it possesses very few pores of type 4 andmore numerous pores of type 5 (Neuhaus and Kier-mayer 1982) associated with granulation at the lobesand a central pore complex (Figs 7,9,10). Their distri-bution is similar, but not identical to that of E. dentic-ulatum Gay (Neuhaus and Kiermayer 1982). Latterspecies possess some pores of type 5 at the apicalnotch base that are absent in our alga. Moreover, E. denticulatum is distinguished from the alga underconsideration by having numerous pores of type 2 scat-

tered at the face of the semicells, which make theirsurface somewhat scrobiculated. In our alga, the cellwall looks smooth except for granulation at the lobesand central protrusion. The warts above the central pro-trusion recorded in our taxon also have pores that canbe characterized as a type 5 (Fig. 7).

The SEM photograph of E. denticulatum, presentedby Vyverman (1991; pl. 138a) shows a slightly differ-ent type of cell wall ornamentation as has been notedin the species (Neuhaus and Kiermayer 1982). Theplant illustrated by Vyverman does not have any gran-ules at the base of the apical notch and pores of type2 seem to be absent. There is a single big scrobicle ateach lateral lobe, but according to Neuhaus and Kier-mayer (1982) these scrobicles are numerous in thisspecies. We can assume that the specimen depicted byVyverman (1991) corresponds to some species otherthan E. denticulatum.

The cell wall of E. gayanum, a species having com-parable morphology to the alga under consideration, ischaracterized by reticulate ornamentation at the distalpart of the semicells and venate ornamentation at theirproximal sides (Vyverman 1991). This feature strictlysegregates E. gayanum from our specimens which hadthe type of cell wall other than described above. Gran-ules at the lobes of E. gayanum have quite a differentappearance compared with those of our plant and pre-sumably are not provided with pores. Such a distinctivecell wall ornamentation of the species raises questionsabout the taxonomic affiliation of its infraspecific taxa,var. angulatum Krieg. and var. huberi Krieg. These taxacan not be regarded as varieties of E. gayanum if theypossess a cell wall that differs from the reticulate.

Our specimens resemble several taxa. Cells of asimilar shape with granulated lobes were described inE. englerii var. madagascariense, E. gayanum var. angu-latum Krieg., E. denticulatum var. rectangulare W. etG.S. West, E. pseudoboldtii Grönbl. and E. boldtiiSchmidle. All these taxa are characterized by short andbroad apical lobes and patterns of granulation at theapical and lateral lobes. Granules at the base of theapical notch differentiate E. denticulatum var. rectan-gulare from the other species mentioned. AlthoughRuzicka (1981) excluded this taxon from E. denticula-tum no other suggestions were made about its taxo-nomic affiliation. Bigger dimensions and the pattern ofthe cell wall ornamentation differentiate E. boldtii fromour alga. Usually this species bears a large supra-isthmal granule in each semicell which is clearly seenin the lateral view (Ruzicka 1981; pl. 80: 2, 5, 7).Similar decoration is present in E. pseudoboldtii butthere are no granules or warts below the central pro-trusion in the specimens concerned (Figs 7,8). Theremaining two taxa, E. gayanum var. angulatum and E. englerii var. madagascariense, are similar to eachother and according to Bourrelly and Couté (1991) canhardly be distinguished. Despite their similar appear-

235Rare and new desmids

ance, however, the latter taxon can be easily differenti-ated from all other mentioned species by the presenceof two granules on each side of the central protrusion.The cell morphology, pattern of the cell wall ornamen-tation and dimensions recorded in our alga are nearlyidentical to those of E. englerii var. madagascarienseand we, therefore, attributed it to this taxon.

The presence of two warts (sometimes splitting upinto a few granules) above the central protrusion is adecisive feature of the latter taxon. This character iseasily detectable in both front and vertical views evenunder low magnification and can hardly be overlooked(Fig. 6). Bourrelly and Couté (1991; pl. 13: 6) depicteda specimen of E. englerii var. madagascariense with-out this granulation and we suggest that, in fact, itrepresents another species. At the same time, algaillustrated by Rino (1972; figs 9,10) as E. denticula-tum var. rectangulare possess warts as described aboveand resemble more closely E. englerii var. madagas-cariense than the taxon to which it was attributed.

Euastrum englerii var. madagascariense has a muchlower length:width ratio, closed sinus and somewhatsmaller dimensions than those of the nominal variety ofthe species. In our opinion, there is no substantial rela-tionship between these two taxa. Variety presented byBourrelly and Manguin (1949) can hardly be matched

with some other species and we prefer to distinguishit at the species level. As there is already anotherspecies named E. madagascariense (W. et G.S. West)Krieg., we designated this alga as E. biverrucosumnom. nov. et stat. nov. The epithet, Latin bi (two),verrucosus (warty), denotes the presence of two wartson the cell surface.

This alga was found in several localities in Japan andin the Russian Far East. In Japan it was revealed in theplankton of eutrophic Lake Semba and in artificialponds in Kyoto. In Russia the taxon occurred in threeswampy mesotrophic lakes with a diverse aquatic vege-tation (pH 6.0–6.5). It is interesting that in one Japan-ese and two of the three Russian localities C. dilatatumwas also present. Perhaps these two species havesimilar ecologic requirements.

Staurastrum levanderi Grönbl.

This taxon is a member of the group of small-sizedbiradiate species that are characterized by obverselytrapeziform or cup-shaped semicells possessing slenderdiverging spinate processes usually terminating inthree small spines. The representatives of the group, S. levanderi, S. chaetopus Hinode, S. hollandicumCoesel et Joosten, S. pseudolevanderi Coesel et Joosten


Figs 11–17. Light and scanning

electron micrographs of Staurastrumlevanderi. 11,12. Face view of the

cells from natural samples. 13,14.

Face and vertical view of a cell from

a culture having a similar appear-

ance but smaller dimensions than

the natural sample. 15. Face view

of a cell from a culture with granula-

tion at the apex and processes

only. 16. A cell from culture with

two additional transverse rows of

the granules at the semicell body.

17. A cell from culture with trans-

verse rows of bifurcate spines across

bases of the processes and two rows

of spines with dilated bases at the

semicell body.

and S. multinodulosum Grönbl., form a cluster of simi-lar, probably closely related taxa, that evolved in aeutrophic, planktonic environment (Coesel and Joosten1996). The species within the group are distinguishedfrom each other mainly by the pattern of cell wall orna-mentation and, to some extent, semicell shape (Coeseland Joosten 1996). However, from our point of view,these differences are often not evident.

In many samples collected from such habitats,specimens resembling the species mentioned abovewere found (Figs 11,12). In culture they retained thecell morphology and pattern of cell wall ornamentationtypical of the natural populations but their processesbecame shorter (Figs 13,14). Cell length with and with-out processes remained constant both in naturalsamples and culture, 27.5–32.5 µm and 17.5–20 µm,respectively, whereas cell width with processes declinedfrom 45–50 µm in the natural samples to 35–37 µm inculture. The cell wall ornamentation was more pro-

nounced under the culture condition and variable tosome extent. All plants observed possessed cup-shapedsemicells with convex biundulated apices provided withtwo apical rows of spines (Fig. 15). In some specimens,two or four transverse rows (two to four spines in eachrow) across the semicell body were present (Fig. 16).In the specimens with the greatest manifestation of cellwall ornamentation, these spines were often bifurcateand had dilated basal parts (Fig. 17). Depending onthe expression of cell wall ornamentation, cells werefusiform or hexagonal in vertical view.

Due to the morphological similarity between theabove mentioned taxa, the taxonomic affiliation of ouralga is not obvious. A globular or somewhat fusiformshape of the semicells in lateral view and absence ofsupraisthmal ornamentation differentiates our plant from S. hollandicum. The latter character also distinguishesit from another closely related species, S. chaetopus,and, from our point of view, this feature separates


Figs 18–27. Light and scanning electron micrographs of Staurastrum tsukubicum sp. nov. from culture. 18,19. Face and vertical view

of a triradiate cell. 20,21. Face and vertical view of a dichotypic cell. 22. Cells stained with indian ink showing a thin layer of mucilage

around them. 23. A chain of the cells connected by mucilage. 24,25. Face and vertical view of a triradiate cell. 26. A cell showing

a pattern of cell wall decoration. 27. A dichotypic cell.

both mentioned taxa from other members of the group.Another species that has a similar appearance to thealga under discussion, S. multinodulosum, is differen-tiated from it by the presence of an excavated apex andthe pattern of cell wall ornamentation (Grönblad 1926;p. 30, pl. 3: 113, 114). However, this species has also been illustrated with a convex biundulated apex(Thomasson 1974; fig 5:7,8; Parra 1975; pl. 45: 150).

Morphological properties recorded in our speci-mens overlap those of two species, S. levanderi andS. pseudolevanderi. The similarity between these twotaxa has already been mentioned by Prescott et al.(1982), however, Coesel and Joosten (1996) expressedthe opposite point of view regarding these species. Webelieve that the difference in the pattern of cell wallornamentation between these species is minor and, asis shown in the present study, is a variable character.Keeping this in mind, we designated the alga underconsideration as S. levanderi.

This species seems to be rather common in Japan,at least in central Honshu and was revealed in theplankton of nearly all sampled localities. It is surprisingthat the only alga with a similar morphology andecology, S. chaetopus, has been recorded in Japan onlyonce so far (Hinode 1967). We speculate that increas-ing eutrophication of aquatic habitats may be causingchanges in the desmid flora of Japan.

This is the first time this species has been reportedoutside Europe where it was initially described.However, a specimen that can be attributed to S. levan-deri has been recorded in South America as S. tectumBorge var. ayayense Grönbl. f. nana Tell (Capdevielle1982; pl. 4: 6).

Staurastrum tsukubicum sp. nov.

Description: Cellulae minutae, profunde constrictae;semicellulae obverse triangulares vel obverse trapezi-formes; superficies granula (aliquando emarginatae)2–4 in ordinibus verticalibus dispositis; parte basalielongato interdum inflato; apicibus rectis, angulis api-calibus productis in prosessus attenuatos undulatosdivergentes, apicibus truncatis et spinis 4 brevibusordinatis, prosessus ad basim seriebus transversisgranulorum praeditis. Cellulae a vertice visae triradiataevel rhombeae, tribus granulis (aliquando emarginatis)intra marginem lateralem unumquemque; semicellulaetortae.

Dimensions: Longitudo sine processibus 10–12.5 µm,latitudo cum processibus 12–25 µm, isthmi latitudo3–4 µm.

Holotype: Figura 28.Etymology: The species is named after the locality

where it occurred, Tsukuba city, Japan.Cells small, deeply constricted semicells conversely

triangular or trapeziform, their surface with two to fourgranules (sometimes emarginate) in a vertical row;

the basal part elongated and sometimes slightlyinflated; apex straight; apical angles extended intotapering, undulated diverging truncate process tipped with four short teeth, base of each process pro-vided with transverse rows of granules. Cells in verticalview triradiate or rhomboid with three granules (some-times emarginate) at either side; the semicells twisted.Length without processes 10–12.5 µm, width withprocesses 12–22.5 µm, breadth of isthmus 3–4 µm.

In culture, S. tsukubicum forms rather long chains (upto 20–30 cells), surrounded by mucilage (Figs 22,23).

This species has some similarity with S. tetracerum(Kütz.) Ralfs ex Ralfs, S. micron W. et G.S. West andsome other small-sized Staurastrum taxa. In culture, S. tsukubicum always produced a mixture of tri- andbiradiate cells and often dichotypic plants occurred(Figs 20,21,27). Similar variability in radiation hasbeen recorded in S. tetracerum (Teiling 1950). Twistedsemicells are typical for the latter taxon (Brook 1959)and these two characters link it with the presentedspecies. However, S. tsukubicum is clearly distin-guished in such characters as an elongated basalportion of the semicell (Figs 18,24) and the pattern ofcell wall ornamentation (Fig. 26). The latter feature ofthe new species is very distinctive. The number of therows of granules across the semicell body is alwayseven and the central row of granules is very prominent(Figs 19,25). A similar pattern of granulation wasdescribed in S. pseudotetracerum (Nordst.) W. et G.S. West but this species is ornamented with verysmall granules.

There are several species in the genus with elon-gated basal parts of the semicells but they have dif-ferent appearances, types of cell wall ornamentationand usually bigger dimensions.

The species was found in a small, artificial pondsituated at the territory of the National Institute forEnvironmental Studies, Tsukuba city. This algaoccurred all year round in the pond but was most abun-dant during the cold months. Such a habitat is commonin Japan and we speculate that this species may befound elsewhere. However, extensive sampling carriedout in the neighborhood of Tsukuba did not reveal addi-tional localities for the species.


Fig. 28. Staurastrum tsukubicum sp. nov. holotype.

ACKNOWLEDGEMENTSThe authors are much indebted to Drs R. Lenzenweger(Ried/Innkreis, Austria) and D. B. Williamson (Leister,UK) for their comments on some species and to Dr B.Robertson (NIES, Japan) for correcting the English. Dr P. Coesel (University of Amsterdam, Netherlands) is acknowledged for his helpful comments on the manu-script. This study was supported by a grant to A.A.G.from the Science and Technology Agency (Japan).

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