Occurrence of the Siphonous Green Alga Ostreobium in Japan

5 Pages·1992·1.4 MB·English

by  Takaaki Kobara

植物研究雑誌
J. Jpn. Bot.
67: 227-231 (1992)
Occurrence of the Siphonous Green Alga
Ostreobium in Japan
Takaaki KOBARAa a nd Mitsuo CHIHARAb
aSenshu University，Hi gashi-mita，T ama-ku，K awasaki，K anagawa，2 14 JAPAN;
bThe Japanese Red Cross College of Nursing，H iroo，M inato-ku，T okyo，1 50 JAPAN
管状緑藻カイガラミドリイト属(新称)Ostreobiumの日本における生育
高原隆明a，千原光雄b
専修大学 214神奈川県川崎市多摩区東三田 2-1-1
a
日本赤十字看護大学 150東京都港区広尾 4-1-3
b
(Received on February 13，1 992)
The occurrence of the siphonous green alga Ostreobium in Japan is reported for the first time.
The alga was collected in the southern islands of Japan，I riomote and Okinawa. The alga penetrated
into dead corals as its substratum. In culture the alga was shown to be capable of penetrating into
oyster shells. In free-living culture，th e alga produced sporangia-Iike organs with releasing tubes. On
the basis of the morphology of vegetative filaments and the sporangia-like organs，th e alga is identified
as at axon closely related to，if not identical with，O streobium quekettii Bornet et Flahault.
Introduction culture of free-living thal1i of this alga and，c on-
Ostreobium is as iphonous green alga inhabiting sequently，w e confirmed it to be very similar to，
calcium carbonate，s uch as mollusk shells and if not identical with，Os treobium quekettii Bornet
corals，a s the substratum. We have found an et Flahault. This is the first record for the genus
Ostreobium-like alga penetrating dead corals Ostreobium in Jap an.
collected at lriomote and Okinawa Islands in
southern Ja pan.恥1icroscopicallythe alga is fila- Materials and Methods
mentous，s iphonous，no nseptate，a nd it is branched Many dead corals were collected from the
and grass green in color. These features agree with bottom of shaded pools in the low intertidal zone
those of the genus Ostreobium. Although identi- at Toyohara，Ir iomote Island in February，1 979，
fication to generic rank is rather easy，s pecies and at Nashiro，Ok inawa Island in March，19 80.
identification is difficult unless the alga is fertile， Some of them had ap ale green appearance in those
because the thalli are so simple and there are few parts where Ostreobium grew. These pieces were
taxonomic characters detectable. In order to obtain brought back to the laboratory within af ew days，
the fertile specimens，w e established a unialgal and then cultured preliminarily in am edium with
-227-
228 植物研究雑誌第67巻第4号 平成4年8月
GeO 2，F ilaments of Ostreobium grew rapidly and， Thalli are endolithic in dead corals as the
in about two weeks，th e corals became dark green substratum and are filamentous， siphonous，
in color (Fig. 1). nonseptate，a nd laterally or subdichotomously
Free living specimens of Ostreobium were branched (Fig. 2). Filaments are neither con-
obtained by the following method. Corals showing stricted，no r swollen，a nd there is no conspicuous
the dark green color were broken into many small difference in diameter through the entire length.
pieces，ab out one millimetre across，an d these small Primary filaments and branches are almost same
pieces were continuously cultured. Another two in diameter，m easuring 4-10μm. Free-living
weeks afterwards，m any short and thin filaments specimens obtained in culture produced branchelets
grew out radially or irregularly from the sub- irregularly，la terally and above，to form am ass of
stratum. Unialgal cultures of free-living thalli were entangled filaments (Fig. 3). Secondary branchlets
grown from cut off apical portions of the fila- are produced in the same way as the primary
ments，c ultured in am edium without Ge02・ filaments. These branchlets are also similar to the
Specimens of Ostreobium penetrating into primary filament in diameter throughout their
oyster shells as their substratum were obtained length (Fig. 4). Chloroplasts are round or discoid
artificially as follows. Filaments 2-3 mml ong in shape，2 -4μm in length and about 2μm in
were cut off from the free-living cultures，a nd these width (Fig. 5). They do not possess pyrenoids. The
fragments were scattered on the surface of shells alga grown. in culture were shown to be capable
placed on the bottom of culture dishes. of penetrating into oyster shells，f orming green
Cultures obtained in these experiments were all patches on their surface，a nd in an older cultures，
maintained in an incubator，un der the condition of these shells became entirely green due to the
200C and the light regime of 14: 10 (light:dark penetrating filaments (Fig. 6). Primary filaments
cycle)，wi th the light intensity of 2，000-3，000 lux and branches within the substratum are rather
from cool white fluorescent lamps. Allth e cultures slender compared with those of free living
were carried out using PES medium (Provasoli specimens and measured 3-7μm in diameter.
1966). In the preliminary culture，G e02 was added Sporangia-like organs produced in free-living
at ar ate of 1m g per one liter of medium. cultures were sac-shaped，5 0-150μm in size.
They possessed one or two tubes，p resumably
Observations related to zoospore release (Fig. 7-8). The organs
Ostreobium quekettii Bornet et Flahault，Bu ll. were borne at terminal ends of branches and not
Soc. Bot. Fr. 36: 161，P 1. IX，fi gs. 5-8，1 889; separated by septa (cell wall) from the vegetative
Kornmann & Sahling，H elgolander Meersunters. filament.
34: 115，1 980. Habitat. Endolithic in both dead and living
Japanesename. Kaigara-midori-ito (nom. nov.). corals and shells of mollusks below low tide level.
Figs. 1-8. Ostreobium quekettii.
1: A portion of coral，in which the filaments of O. quekettii penetrate. Specimen was collected from
Toyohara，Ir iomote Island，Fe bruary，19 79.2: Filaments penetrating into api ece of coral as the substratum.
3: Free-living filaments in culture，fo rming “green entangled threads". 4: Part of filaments with branches.
5: Part of af ilament，sh owing chloroplasts with no pyrenoid. 6: Oyster shells，wi th penetrating filaments
of Ostreobium. 7-8: Sporangia-like organ with tube，p roduced at the terminal end of ab ranch.
August 1992 Journal of Japanese Botany Vol. 67 No. 4 229
230 植物研究雑誌第67巻第4号 平成4年8月
Type locality. Le Croisic，F rance. and o. reineckei，b oth having thin filaments，
Specimen examined. Toyohara，I riomote Isl. usually less than 10μm in diameter. When he des-
(Feb. 1979)，N ashiro，O kinawa Isl. (Mar. 1980); cribed O. reineckei，B ornet (1896) used the pattern
Ayamaru Point，A mami Isl. (Mar. 1985)，K an- of branching as one of the main characteristics to
minato，H achijo Isl. (May 1988). distinguish his alga from the type species，O .
Geographical distribution. Possibly widely quekettii. Setchell (1924) distinguished the two
distributed in temperate to tropical regions. species as follows: in O. reineckei，th e “network"
Ostreobium quekettii，t he type species of the of the thallus is not at rue network，s ince the
genus，wa s described by Bornet and Flahault (1889) recurved ultimate branches do not unite but form
on the basis of as pecimen collected at Le Croisic af lattened design similar to an etwork without any
in France，o n the North Atlantic Ocean coast. The anastomosis. However，L ukas (1974) does not
type specimen was found penetrating old oyster agree with these authors and considered all the
shells. Later，Bo rnet (1896) described O. reineckei Ostreobium filaments he collected and examined
on the basis of as pecimen collected at Samoa from both the Atlantic and Pacific Oceans did not
Islands in the South Pacific. This species was found show characteristic differences noted by Setchell
penetrating into corals. In 1932，W eber-van Bosse (1924) and others such as Wainwright (1963).
added three species to the genus from the Indo- Lukas (1974)，co nsequently，re garded two taxa as
Pacific region; O. duerdenii，O . brabantium，a nd conspecific. More recently，K ornmann and Sahling
O. okamurai. All were found mainly penetrating (1980) cultured O. quekettii from Helg01and and
corals. Recently，th e sixth species，O. constrictum， observed that the alga produced sac-like sporangia，
was described by Lukas (1974) on the basis of a releasing quadriflagellate zoospores. The sporangia
specimen collected from the Caribbean. This of their alga differed in shape from those of O.
species also occurred in corals. When he described reineckei，a s illustrated by Setchell (1924). They
this new species，L ukas also provided ak ey to the were not remarkably swollen but rather spindle-
species of Ostreobium. According to Lukas，O . shaped and had at erminal aperture. In the alga
constrictum is characterized by the presence of described here the sporangia-like organs were
constrictions of the filament. In O. duerdenii，t he swollen and sac-like shaped with releasing tubes
primary filament and branches differ in diameter， (Figs. 7-8). They appear to be fundamentally the
the former measuring up to 140μm，wh ile the latter same as those in O. quekettii as illustrated in Korn-
measuring 8-26μm (Weber-van Bosse 1932). The mann and Sahling (1980). On the basis of the
branching pattern of this species is also above，w e conclude that alga is very similar to，if
characteristic: in the illustration of Weber-van not identical with，O streobium quekettii Bornet et
Bosse (1932，P l. 11，F igs. 1-2)，t he filament Flahault. Kornmann and Sahling (1980) have ex-
branches subdichotomously but one of each branch pressed doubts about whether material considered
pair remains short. In O. okamurai，f ilaments are as O. quekettu by authors such as Lukas (1974)
8-10(-'-40)μm in diameter and the sporangia-like is identical with the type species. As already noted，
organs are always separated by septa from the the type locality of O. quekettii is in relatively cold
primary filaments (Weber-van Bosse 1932). waters where the alga penetrates oyster shells，
With respect to the diameter of the filaments， whereas the alga described here was found in the
the material described here is similar to O. quekettii warm seas and penetrating corals. In laboratory
August 1992 Journal of Japanese Botany Vol. 67 No. 4 231
culture，ou r alga penetrated both oyster shells and of marine algae. In Watanabe A. and Hattori A. (eds.)
Cultures and collections of algae. pp. 63-75. Jpn. Soc.
corals，b ut it grew slowly and did not form
Plant Physio ，.lTokyo.
sporangia-like organs at 150C，th e temperature at Weber-van Bosse A. 1932. Algues. Resultats Scientifique
du Voyage aux lndes Orientales Neerlandaises de LL.
which Kornmann and Sahling (1980) obtained
AA. RR.le Prince et la Princesse Leopold de Belgique.
good culture for O. quekettii. The exact identifica- Mus. Roy. Hist. Natur. (Belgique) Mem. Hors Ser. 6(1):
1-28.
tion of the Japanese Ostreobium from subtropical
Wainwright S. A. 1963. Skeletal organization in the coral
regions，c an be resolved only with further study. Poci!/opora damicornis. Quart. J. Microscop. Sci. 104:
169-183.
We are grateful to Dr. Robert J. King， 要 旨
University of NewS outh Wales，Au stralia，fo r his
管状緑藻の Ostreobiumを日本新産属として報
reading of the manuscript.
告した.この藻は西表島と沖縄本島から得たもの
で，いずれも潮間帯のタイドプールの底から採取
References
Bornet E. 1896. Ostreobium Reineckei. In Reinbold T.， したサンゴの破片に穿孔して生育していた.培養
ed. Flora Samoa lnseln，En gler's Bot. Jahrb. 23: 269. の結果，その藻はカキの員殻にも穿孔する能力を
一一一一一andFlahault C. 1889. Sur quelques plantes vivant
もつこともわかった.フリーリビングの糸状体は，
dans le test calcaire des mollusques. Bull. Soc. Bot. Fr.
36: 147-176. 遊走子嚢と恩われる生殖器官を枝の先端部に形成
Kornmann P. and Sahling P.-H. 1980. Ostreobium
した.天然から得た標本の形態と培養で得た遊走
quekettii (Codiales， Chlorophyta). Helgolander
Meeresunters. 34: 115-122. 子嚢様の器官の形態から，本藻を O.quekettii
Lukas K. J. 1974. Two species of the chlorophyte genus Bornet et Flahaultと同定し，新和名「カイガラ
Ostreobium from skeletons of Atlantic and Caribbean
ミドリイト」を与えた.
reef corals. J. Phycol. 10: 331-335.
Provasoli L. 1966.恥1ediaand prospects for the cultuvation