Rikunomizu（Limnology in Tokai Region of Japan）43 : 91 - 94（2010）

Conjugation and zygospores of a filamentous green alga, Spirogyra sp.,propagated in a littoral zone of the north basin of Lake Biwa, Japan
Kentaro NOZAKI1)

Abstract
Photographs of conjugation and zygospores of a filamentous green alga, Spirogyra sp., propagated in a littoral zone of thenorth basin of Lake Biwa were obtained for the first time in this report. Sample containing conjugation and zygospores wascollected at Mizugahama (Oumi-Hachiman City of Shiga Prefecture) located in the eastern coast of the north basin of Lake
Biwa on 23 June 2005. Conjugation formed by two different filaments was scalariform type. Fertile cells inflated both sides.
Zygospores were ellipse-shaped. Since the collected zygospores did not fully ripen, the exact species remains unknown.
Key words: Conjugation, Filamentous green algae, Lake Biwa, Spirogyra sp., Zygospore(Received: 16 September 2008, Accepted: 4 November 2008)
basin of Lake Biwa.

Introduction
Genus Spirogyra is a common group of filamentous green algaeMethods

observed in many freshwater environments. Propagation ofSpirogyra sp. in littoral zones of the north basin of Lake Biwa hasThis study was carried out in a littoral stony zone near Mizugahama

been reported by Nozaki (1999), Nozaki (2001), Nozaki and(Chomeiji, Oumi-Hachiman City of Shiga Prefecture) located on

Mitamura (2002), Nozaki et al. (2003) and Ishida et al. (2006).

the eastern coast of the north basin of Lake Biwa on 23 June 2005.

The development of the Spirogyra sp. community seems to be theMore information about the location of sampling site was described

result of an increase in the nutrient supply from human activities

in Nozaki and Mitamura (2002) and Nozaki (2004). The bottom(Nozaki, 2004).

of the site was covered with gravel (grain diameter 10-20 cm) andBecause the species of Spirogyra was classified by shape andmacrophytes were not present. Water temperature was measured

color of conjugations and fully-ripened zygospores formed inwith a thermometer. Underwater light intensity was measured withsexual reproduction (Yamagishi, 1966; Hirose and Yamagishi,

an underwater illuminance meter (Minolta, T-10).

1977), determination of the exact species is very difficult. Nozaki

Three samples of benthic algae-dominated Spirogyra sp. wereand Mitamura (2002) had been culturing a Spirogyra sp. isolated

collected from stones in the respective quadrates (25 × 25 cm2)from the north basin of Lake Biwa under laboratory conditions

at 32-35 cm depths. The algae were removed from the stones usingfrom September 1999 to August 2000. However, conjugation anda steel brush. All the samples were stored in an ice-box and werezygospores of this alga were not formed. Since neither conjugation

returned to the laboratory within 3 hours after sampling. Eachnor zygospores of this alga have been described in previous studies,sample was filtered on a glass fiber filter (Advantec, GA-100)

the species propagated in Lake Biwa remains unknown. Graham etin preparation for analysis of chlorophyll a (Lorenzen, 1967).

al. (1995) reported the same result as Nozaki and Mitamura (2002)

Filaments of Spirogyra sp. were observed under optical microscopeusing a Spirogyra sp. isolated from Surrey Lake in the United(Olympus, BX 51), and photographs of conjugation and zygospore

States. In order to identify the Spirogyra sp. propagated in the north

were taken by digital camera (Olympus, Camedia C-5060).

basin of Lake Biwa, conjugation and zygospores of this alga should
be collected from field studies.

Results and Discussion

In the present report, photographs of conjugation and zygosporesof the Spirogyra sp. were obtained for the first time in the northWater temperature at the sampling site at 11:00 AM was 23.2 ℃ ,1)
School of Education, Sugiyama Jogakuen University, Hoshigaoka Moto-machi 17-3, Chikusa, Nagoya, Aichi 464-8662, Japan（E-mail: ken@sugiyama-u.ac.jp）

91Kentaro NOZAK
and the underwater light attenuation coefficient (k) was 0.332 m-1.

Nozaki, K. (2004): Development of a filamentous green algal

A filamentous green algal mat formed by Spirogyra sp. covered

community in the littoral zone of Lake Biwa: a mini-review.

with stones had a thickness of 10-20 cm. Chlorophyll a of theKorean Journal of Limnology, 37: 368-372.

-2benthic algal community was 441 ± 55 (mean ± SD) mg m .

Nozaki, K. and O. Mitamura (2002): Seasonal change in aCell numbers of a Spirogyra sp. were 85500 ± 16000 (mean ±filamentous green-algal community in the littoral zone of Lake-2SD) cells cm . From comparison with previous studies (Nozaki,Biwa: examination of temperature effect on its summer decline.

2001; 2003), the Spirogyra sp. was considered to propagate well

Verhandlungen der Internationale Vereinigung f翰r Theoretischeon the sampling date.

und Angewandte Limnologie, 27: 2660-2664.

Figure 1 shows the filament (a) and rhizoid (b) of a Spirogyra

Nozaki, K., K. Darijav, T. Akatsuka N. Goto and O. Mitamura

sp. propagated at the sampling site. Width and length of cylindrical(2003): Development of filamentous green algae in the benthic

cells were about 30-50 μm and 120-240 μm, respectively. The

algal community in a littoral sand-beach zone of Lake Biwa.

cells contained four chloroplasts and plane end walls. The same

Limnology, 4: 161-165.

type of alga was observed at Kita-Komatsu (Nozaki, 1999; 2001,

Yamagishi, T. (1966): Studies on the genus Spirogyra collected2004) and Kaizu-Oosaki (Nozaki, unpublished observation; studyin Japan. Scientific Report of Tokyo Kyoiku Daigaku, Section

site of Ishida et al., 2006). Figure 2a ( × 100) and 2b ( × 200)

Biology, 12: 73-105.

show the conjugation and zoospores of a Spirogyra sp. Conjugation(Editor: Dr. Tetuo MURAKAMI, Professor of Nagoya Women’s

formed by two different filaments was scalariform type. FertileUniversity)

cells inflated both sides. Zygospores were ellipse-shaped, and thepattern of medium spore wall was probably smooth. Diameters

摘and lengths of the zygospores were 30-40 μm and 60-80 μm,

要respectively. The collected zygospores did not fully ripen, so the

琵琶湖北湖沿岸帯で繁茂するアオミドロ（Spirogyra sp.）のspecies could not be confirmed.

接合体と接合胞子In order to definitively identify the Spirogyra sp., factors affecting
the conjugation and zygospores formation should be detected from

野崎健太郎

field and laboratory studies.
琵琶湖北湖の沿岸帯で繁茂する糸状緑藻アオミドロ（Spirogyra sp.）の接合体と接合胞子の写真を初めて記載しReferencesた。試料は琵琶湖北湖東岸の水が浜（滋賀県近江八幡市）でGraham, J. M., C. A. Lembi, H. L. Adrian and D. F. Spencer

2005 年 6 月 23 日に採集された。接合の型は，異なる 2 本の(1995): Physiological responses to temperature and irradiance

糸状体による梯子接合であった。雌性配偶子嚢は，両側に膨in Spirogyra (Zygnematales, Charophyceae). Journal of張した。接合胞子の形はだ円であった。採集された接合胞子

Phycology, 31: 531-540.

は完熟ではなく種名の決定には至らなかった。

Hirose, H. and T. Yamagishi (1977): Illustrations of the Japanese

キーワード：アオミドロ，糸状緑藻，接合体，接合胞子，Fresh-water Algae. Uchida Rokakuho, Tokyo (in Japanese).

琵琶湖

Ishida, N., O. Mitamura. and M. Nakayama (2006): Seasonalvariation in biomass and photosynthetic activity of epilithic（椙山女学園大学教育学部〒 464-8662 愛知県名古屋市千種区

algae on a rock at the upper littoral area in the north basin of星ヶ丘元町 17-3）

Lake Biwa. Limnology, 7: 175-183.
Lorenzen, C. J. (1967): Determination of chlorophyll and pheopigments: spectrophotometric equations. Limnology andOceanography, 12: 343-346.
Nozaki, K. (1999): Algal community structure in a littoral zone in
the north basin of Lake Biwa. Japanese Journal of Limnology,
60: 139-157.
Nozaki, K. (2001): Abrupt change in primary productivity in alittoral zone of Lake Biwa with the development of a filamentous
green-algal community. Freshwater Biology, 46: 587-602.

92Conjugation and zygospores of Spirogyra sp., in Lake Biwa, Japan(a)100 �m(b)100 �mFig. 1. Photographs of filament (a × 200) and rhizoid (b × 200) of a Spirogyra sp.

93

Kentaro NOZAK(a)200 �m(b)100 �mFig. 2. Photographs of conjugation and zoospores of a Spirogyra sp. (a) × 100, (b) × 200.

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