Construction of a reproductive stem cell bank for rare Indonesian fish species: Aiming to preserve valuable genetic resources forever (preliminary survey)

Indonesia is a country rich in biodiversity, home to approximately 20% of the world’s plant and animal species. Its biodiversity index ranks second only to Brazil, which is home to the Amazon rainforest. In aquatic ecosystems, over 5,000 species have been recorded, including around 1,300 species of freshwater fish. This number is the third largest number of species in the world after Brazil and China. Furthermore, 142 of these species are listed as endemic species.

Sulawesi, part of the Wallacea group of islands, is home to an ancient lake system known as the Malili Lake Group, which supports a high number of endemic species. In these waters, Oryzias species are undergoing rapid speciation, with 20 out of the 30 known species found here.

Although Indonesia has such a rich biota, deforestation and construction of huge dams using overseas capital is rapidly progressing, and in some areas the aquatic environment is steadily deteriorating. The increase or decrease in the biomass of the above-mentioned freshwater fish, especially endemic species, is not clear as there have been almost no reports, but there is a concern that the impact of environmental degradation will occur.

Meanwhile, looking at the waters, Indonesian coelacanth (Latimeria menadoensis) lives in the waters around Sulawesi. It was believed that this species was extinct at the end of the Cretaceous period, but in the 20th century, the living organism of Latimeria chalumnae was discovered in the Comoros Islands, and in 1997 the life of Latimeria menadoensis was also confirmed. Both species are thought to be ancestors of quadrupeds and are known as "living fossils." Recent studies have reported that Latimeria chalumnae has a long lifespan of around 100 years, with five years gestational periods and 55 years to launch the spring. Furthermore, the number of larvae for fish is extremely small, and is reported to be 3-30. The life history of Latimeria menadoensis has been largely unclear, but these facts suggest that the two species of coelacanths may be particularly vulnerable to environmental changes.

In this way, Indonesia has valuable genetic resources for fish in both freshwater and seawater areas, but to date, no long-term preservation system has been established. The representatives were the first in the world to freeze and preserve in liquid nitrogen germline stem cells present in the ovaries and testes of fish, and further succeeded in developing a technology in salmonids to produce eggs and sperm from frozen cells by transplanting these frozen germline stem cells into surrogate parent host individuals. By applying this technology, we have been able to steadily produce eggs and sperm of the endangered species of the cyprinid Pseudorhodeus tanago (Miyakotanago) and the gasterosteid Puntigius sp.4 (Musashitomiyo), as well as the eggs and sperm of the wild extinct species, the salmonid Oncorhynchus kawamurae (Kunimasu), and, in turn, their next-generation individuals. This method allows cells to be preserved for a long period of time (theoretically permanently) without passage, and since these cells can be used to regenerate individuals at any time, it avoids alteration of the genetic composition of the population associated with passage. Taking these points into consideration, this method could be decisive for the long-term preservation of genetic resources of endangered species.

Therefore, this project aims to cryopreserve germ stem cells from rare Indonesian fish (building germ stem cell banks), and to establish a system to spread this technique to local researchers, with the aim of conducting a preliminary investigation.

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Principal investigator

Dr. Goro YOSHIZAKI: Professor, Tokyo University of Marine Science and Technology

Collaborators

Japan	Mr Yuichi Amano (Tokyo University of Marine Science and Technology) Dr Yutaka Takeuchi (Kanazawa University) Mr Yuta Horiuchi (Kanazawa University)
Indonesia	Dr Kawilarang Warouw Alex Masengi (Sam Ratulangi University) Ixchel Feibie Mandagi (Sam Ratulangi University) Dr Alimuddin (Institut Pertanian Bogor) National Research and Innovation Agency

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Nagao Natural Environment Foundation
4-20-9 Midori, Sumida-ku
Tokyo 130-0021 Japan
Phone : +81-3-6659-2070
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