水研センター研報，第16号，9−13，平成18年
Bull. Fish. Res. Agen. No. 16, 9‑13, 2006

短報

Growth of excised pieces containing elongated denticles from the lower
marginal parts ofandgametophytes
Eiji FUJIYOSHI＊1and Norio KIKUCHI＊2

Abstract
andgametophytes have elongated denticles that take the form of small lobes on their lower marginal parts. We investigated the ability of these elongated denticles to form gametophyte lobes, using excised pieces that were freed from the influence of other parts. Gametophytes of the two species werecultured from conchospores for a period of 2 months. Small pieces containing elongated denticles were excised from the lower marginal parts of the gametophytes and cultured at 20℃ and 40μmol photons m −2 s −1 under a photoperiod regime of 10L : 14D（light : dark）. After about 1 month, some of the elongated denticles further developed, and the excised pieces
came to resemble lacerated thalli. These results suggest that the elongated denticles possess
the ability to grow into lobes under natural conditions.
Key words:, denticle, thallus, culture, gametophyte

possess smallthese two species, one with lacerated gametophytes

denticles along the margins of their gametophytes

Some species of the genus

and the other with unlacerated gametophytes, using（foliose thalli）. The role of the denticles has not yet

excised pieces that were freed from the influence

been revealed.

of other parts in reference to the experiments ofShinmuragametophytes are lacerated and have specificelongated denticles that take the form of small

Notoya（1995；1999）.
Gametophytes used in the present study werelobes on their lower marginal parts. Although theinitiated from conchocelis ofelongated denticles ofandwhich. The former originated fromcharacterize this species are expected to grow intoa gametophyte collected at Ginowan, Okinawa

lobes, they reached only a few mm in intact thalli in

Prefecture, Japan, on 26 February, 1998 and the latteran earlier culture study（Shinmura, 1974）. However,

was a cultivar provided by the Saga Prefectural

this result does not preclude the possibility that theAriake Fisheries Research and Development Center.

growth of elongated denticles is limited in intact

Culture methods were conducted as describedthalli, as is lateral bud inhibition in higher plants.

previously（Shinmura, 1974；Migita and Ito, 1987；

Chang et Zheng gametophytes
which are not lacerated also have elongateddenticles（Chang, T. and B. Zheng, 1960）.

Aramaki., 2001）.

Gametophytes were cultured from conchospores
for a period of 2 months at 20℃ and 40μmol

In this study, we investigated the ability of thephotons m −2 s −1 under a photoperiod regime

elongated denticles to form gametophyte lobes inof 10L：14D （light：dark）. Although enriched

2005年12月6日 受理（Received on December 6, 2005）＊1
西海区水産研究所 〒851‑2213 長崎県長崎市多以良町1551‑8（Seikai National Fisheries Research Institute, 1551‑8 Taira-machi, Nagasaki 851‑2213,Japan）＊2
千葉県立中央博物館海の博物館 〒299‑5242 千葉県勝浦市吉尾123（Coastal Branch of Natural History Museum and Institute, Chiba, 123 Yoshio,
Katsuura 299‑5242, Chiba, Japan）

Eiji FUJIYOSHI and Norio KIKUCHI
seawater SWMⅢ（Ogata, 1970）is recommended

one of the elongated denticles reached 3mm（Fig.

（Kito, 1985）forgametophyte culture,2E）. After 24 days, the elongated denticles grew

the enrichments in SWMⅢ are considered to besignificantly and transformed into lobes （Fig.

too concentrate, especially for2F）. After 32 days, the marginal parts of the lobes

gametophyte culture （Fujiyoshi, unpublished）.

had matured and one of them reached nearly 8cm in

Therefore 1/10 modified SWMⅢ medium andlength（Fig. 2G）.

1/2 SWMⅢ medium （Table 1） were used forgametophyte culture ofAlthough the elongated denticles ofandwere hypothesized to grow into, respectively. Gametophytes oflobes, they reached only a few mm in length inandgrew to reach

intact thalli（Shinmura, 1974）. Migita and Ito（1987）

7 0‑9 7cm and 17 2‑36 8cm, respectively （Fig.

reported that the gametophytes of1A, 2A）. As in the previous culture experimentwere torn into many lobes along straight slits in（Shinmura, 1974）, our cultured

culture. In this study, the gametophytes from which

gametophytes were not lacerated（Fig. 1A）. Small

the pieces were excised were not lacerated（Fig.

pieces containing elongated denticles（Fig. 1B‑C,1A）, and elongated denticles on the margin of the2B‑C）were excised from the lower marginal parts

piece grew and transformed into lobes（Fig. 1D‑I）.

of the gametophytes and cultured under the same

These results suggest that the elongated denticles

conditions. For

possess the ability to grow into lobes under natural, a dioecious species, amale gametophyte was used.

conditions as detailed in Shinmuraʼs hypothesis.

The elongated denticles on the margin of anexcised piece ofWhen most of the thallus is cut off, for example,

were smaller thanby natural wave action, it seems that elongated

1mm in length（Fig. 1D）. Ten days later, one of thedenticles on the margin of the remaining lower

cut edges became umbilicate, with the appearance

part freed from the influence of the upper partof rhizoids, and the elongated denticles resembled

grow significantly. However, torn‑like wild thallilobes（Fig. 1E）. After 15 days, the lobes that had

as reported by Migita and Ito（1987）have beendeveloped from elongated denticles reached 3mm inobserved at Ginowan. Further study is needed tolength（Fig. 1F）. After 30 days, the marginal parts

reveal the mechanism by which lobes are formed inof the lobes had matured（Fig. 1H）. However, lobes

nature.

grew larger, and one of the lobes reached nearly
3cm in length after 38 days（Fig. 1I）.
The elongated denticles on the margin of anexcised piece ofgametophytes, which are notconsidered to be lacerated, have characteristic
elongated denticles （Chang, T. and B. Zheng,were smaller than1960）. In this study the elongated denticles on the0 5mm in length （Fig. 2D）. Eleven days later,

margin of the excised piece grew and transformed

Table 1. Contents of 1/2 and 1/10 modified SWMⅢ media.

Growth of elongated denticles ofgametophytesFig. 1. Gametophytes of, and growth of a piece containing elongateddenticles that was excised from the lower marginal part.（A）Intact thalli grown from conchospores
after 2 months in culture.（B）Microscopic denticles on the middle marginal part.（C）Elongateddenticles on the lower marginal part.（D）Excised piece containing elongated denticles（a-d）. Arrows
indicate cut edges.（E-I）Successive stages of the excised piece（D）in culture, showing developmentof the denticles（a-d）.（E）10 days later.（F）15 days later.（G）20 days later.（H）30 days later.（I）38
days later. Scale bars : A, 1 cm ; B-C, 100 μm. ; D-F, 1 mm ; G-I, 1 cm.

Eiji FUJIYOSHI and Norio KIKUCHI

Fig. 2. Gametophytes of, and growth of a piece containing elongated denticles
that was excised from the lower marginal part.（A）Intact thalli grown from conchospores after 2
months in culture.（B）Microscopic denticles on the middle marginal part.（C）Elongated denticles
on the lower marginal part.（D）Excised piece containing elongated denticles（a-d）. Arrows indicate
cut edges.（E-G）Successive stages of the excised piece（D）in culture, showing development of thedenticles（a-d）.（E）11 days later.（F）24 days later.（G）32 days later. Scale bars : A, 5 cm ; B-C, 100
μm ; D-E, 1 mm ; F-G, 1 cm.

into lobes （Fig. 2D‑G） in the same way as did

lobes in culture, and the pieces came to resemble. This result suggests there may

lacerated thalli. These results suggest that theexist lacerated thalli ofin nature;

however, we do not have any clear information inelongated denticles possess the ability to grow intolobes under natural conditions.

this regard.
Notoya （1995, 1999） cultured small excised
pieces from

Acknowledgements

gametophytes, andreported regeneration of bladelets on the cut edge

We thank Dr. Marcy N. Wilder, Japan Internationalof the upper side, but did not report the growth

Research Center for Agricultural Sciences, andof denticles. Denticles growth does not seem to beDr. Makoto Yamasaki, Seikai National Fisheries

typical for theResearch Institute, for correcting and editing thein which gametophytes

possess denticles.

manuscript. We are grateful to Dr. Takeshi Toma,

Elongated denticles on the margin of the excised
pieces fromandgametophytes developed and transformed into

former President of the Okinawa Prefectural
Deep Sea Water Research Center, and Dr. Yoshio
Kawamura, Saga Prefectural Ariake Fisheries

Growth of elongated denticles ofResearch and Development Center, for theircooperation in collecting materials.

gametophytes
English abstract）

Kito, H., 1985：Isolation and development ofprotoplast inReferences, 8, 20‑24.（In Japanese）
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Aramaki H., Yokoo K. and Kawamura, Y., 2001：
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,Ogata, E., 1970：About new enriched seawater
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