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研究成果

Development of Seed Production Technology for Ocean Farming Using Gametophytes of the Red Alga Asparagopsis taxiformis
—Expected Contribution to Stable Feed Production for Methane Reduction from Cattle Burps—

press202527.pdf2 MB

2026-03-10
Japan International Research Center for Agricultural Sciences (JIRCAS)

Key Points

  • Established the temperature and daylength conditions (water temperature 25°C, photoperiod 8h light : 16h dark) under which sporophytes of Asparagopsis taxiformis release tetraspores that serve as "seeds" of gametophytes.
  • Successfully cultured young gametophytes germinated from tetraspores and raised them as seedlings for aquaculture.
  • Expected contributions include stable production of A. taxiformis feedstock, known for mitigating methane emissions from cattle, and improved productivity in marine cultivation.

Overview

JIRCAS, in collaboration with Nagasaki University, has developed a technology to artificially manipulate the life cycle of Asparagopsis taxiformis1  by controlling temperature and photoperiod, and to artificially produce gametophytes that can be used as seedlings for marine aquaculture2.

This seaweed contains large amounts of bromoform3, a compound that inhibits microbial methane fermentation in the rumen of cattle and other ruminants, thereby reducing methane emitted as burps. A. taxiformis grows into two generations4, called sporophytes and gametophytes, each of which has a different morphology. Sporophytes are tiny and are primarily cultivated in laboratories or land-based facilities, but land-based aquaculture requires high facility maintenance costs and is not suitable for mass production. Gametophytes, on the other hand, can grow to about 10 cm, making them suitable for marine aquaculture, which allows for large-scale development. However, stable artificial production of gametophytes had not been established.

By focusing on the alternation of generations5 observed in seaweeds, the researchers found that culturing sporophytes under a water temperature of 25℃ and short-day conditions (8 hours light, 16 hours dark) effectively induces the release of tetraspores. They also identified conditions that shorten the time required for spore release. Furthermore, by aerating cultures of young gametophytes germinated from these tetraspores, they were able to stably produce vigorous gametophytes rich in bromoform.

This achievement establishes a fundamental technology that enhances the productivity and stable supply of A. taxiformis for aquaculture. It represents a significant step toward the practical application of livestock feed that can reduce methane emissions from ruminant animals.

The research findings were published as an open access article in the international scientific journal Marine Biotechnology (online, July 21, 2025, JST).

Related Information

Funding
Grant-in-Aid for Scientific Research (KAKENHI) “Elucidating the Bromoform Synthesis Mechanism of the Red Alga Asparagopsis taxiformis—Can Its Cultivation Coexist with Other Seaweeds?” (Project No. 25K09257)

Publication Information

Authors
MATSUDA Ryuya, KUWANO Kazuyoshi
Title
A demonstration of bromoform-producing gametophyte culture for a red alga, Asparagopsis taxiformis in laboratory conditions
雑誌
Marine Biotechnology
DOI: https://www.doi.org/10.1007/s10126-025-10493-2

Contact

JIRCAS President: KOYAMA Osamu

Program Director：
FUJITA Yasunari
Research Staff：
MATSUDA Ryuya (Fisheries Division)
Press Coordinator：
OMORI Keisuke (Head, Information and Public Relations Office)
Press e-mail : info-pr@jircas.go.jp

Terminology

1) Asparagopsis taxiformis
A species of red seaweed distributed from tropical to temperate marine regions, also found naturally along the coasts of Japan. In Australia, this species and its close relatives are already being used as feed for cattle. Asparagopsis taxiformis belongs to a group of red-pigmented seaweeds known as “red algae,” which also includes species like Gelidium and other seaweeds used to produce agar and edible nori.
2) Seedlings for marine aquaculture
In aquaculture, “seedlings” generally refers to juvenile fish or shellfish raised in sea or land-based facilities. Those collected from the wild are called “natural seedlings,” while those hatched and raised artificially are called “artificial seedlings.” The same concept applies to seaweed, and in this study, the release of spores was artificially induced and the subsequent raising of seedlings was successful, so this falls under the category of artificial seedling production technology.
3) Bromoform
An organic halogenated compound in which a single carbon atom is bonded to three bromine atoms and one hydrogen atom. Bromoform inhibits methane metabolism in anaerobic microorganisms. Many seaweeds can synthesize bromoform, but A. taxiformis has specialized gland cells that store large amounts of it, making this species particularly effective in suppressing methane production.
4) Generations
Many seaweeds have two distinct life stages differing in chromosome number: the gametophyte (n generation) with a single set of chromosomes, and the sporophyte (2n generation) with two sets. Gametophytes develop when spores (tetraspores) produced by sporophytes through meiosis undergo cell division. Sporophytes, in turn, arise from the fusion of gametes produced by gametophytes.
5) Alternation of generations
The alternating development of sporophyte and gametophyte stages is called “alternation of generations.” In A. taxiformis, the two generations differ markedly in size and form, a pattern known as heteromorphic alternation of generations. The entire sequence of these alternating life stages constitutes the organism’s life cycle.

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