Concept of Ex-situ Conservation
Ex-situ conservation refers to the preservation of components of biological diversity outside their natural habitats. It includes various scientific and technical approaches to conserve endangered or rare species of flora and fauna in controlled environments such as zoos, aquariums, botanical gardens, seed banks, and gene banks.
This method plays a crucial role in protecting biodiversity, especially in scenarios where in-situ conservation (conservation within the natural habitat) is not feasible due to habitat destruction or environmental changes. Ex-situ conservation is particularly important for species that are highly threatened, have limited populations, or are difficult to protect in the wild.
Importance of Ex-situ Conservation
- Habitat loss is a major threat to biodiversity due to expanding agricultural land, rapid urbanization, industrialization, and dam construction.
- Ex-situ conservation provides a backup strategy for the survival of species outside their native ecosystem.
- It ensures safety, research, breeding, and education, supporting the restoration and reintroduction of species into the wild when conditions improve.
- Ex-situ techniques are especially helpful in preserving rare, endangered, or medicinal plants and threatened animal species.
Methods of Ex-situ Conservation
1. Botanical Gardens
Botanical gardens are scientific institutions where a wide variety of plants are grown and maintained for research, education, conservation, and ornamental purposes. These gardens often host species from different geographic regions and include rare, endangered, wild, and medicinal plants.
A well-developed botanical garden typically includes:
- Greenhouses and nurseries
- Libraries and herbaria
- Research laboratories
- Collections of specimens, illustrations, and reference materials
2. Zoos and Aquariums
Zoos and aquariums help conserve animal biodiversity by maintaining and breeding endangered animal species under controlled conditions. They also play an essential role in public awareness and education.
3. Gene Banks and Seed Banks
Gene banks are used for the long-term storage of genetic material like seeds, pollen, or DNA samples. Seed banks conserve genetic diversity of crop species and wild relatives for future agricultural use.
Concept of In-vitro Repositories
In-vitro repositories are a form of ex-situ conservation that involves preserving living cells, tissues, or organs of plants or animals under artificial laboratory conditions. This method is particularly effective for conserving genetic material under cryogenic conditions (extremely low temperatures).
In animals, cryopreservation is used to store embryos, sperm, oocytes, or tissues that can potentially regenerate a living individual in the future. In plants, meristematic tissues or shoot tips are often stored to ensure regeneration.
Significance of In-vitro Repositories
- Essential for critically endangered species where traditional conservation methods are not viable.
- Helps maintain an adequate gene pool for future breeding, research, and genetic improvement programs.
- Reduces the risk of total extinction, offering a genetic safety net.
Cryopreservation: The Core of In-vitro Conservation
Cryopreservation is the technique of preserving biological samples at ultra-low temperatures (typically −196°C in liquid nitrogen) to halt all metabolic activities and prevent degradation. The process involves six key steps:
1. Selection of Material
- Ideal materials are young, meristematic, small cells that are highly cytoplasmic, non-vacuolated, and thin-walled.
2. Use of Cryoprotectants
- Chemicals like sugars, glycerol, polyethylene glycol (PEG), proline, and other cryoprotectants are added to minimize cellular damage during freezing.
- It is recommended to use a mixture of cryoprotectants in low concentrations to reduce toxicity (Bajaj, 1987).
3. Freezing
- Controlled freezing is necessary to prevent intracellular ice crystal formation.
- A regulated cooling rate or pre-freezing step is used for safe transition to freezing temperatures.
4. Storage in Liquid Nitrogen
- Cultures are stored in liquid nitrogen at -196°C to halt all biochemical reactions.
- Long-term storage is only effective when temperatures are below -130°C.
5. Thawing
- The frozen vials are thawed rapidly between 35°C and 40°C until ice crystals disappear, then shifted to 0°C water bath (Popov, 1985).
6. Washing and Reculturing
- After thawing, tissues are washed to remove toxic cryoprotectants and then cultured again under optimal growth conditions.
Conclusion
The concept of ex-situ conservation & in-vitro repositories is a modern and essential approach to biodiversity conservation. These techniques provide a safety reservoir of genetic resources that can be restored when natural conditions become favorable or used in scientific advancement. As threats to natural ecosystems continue to rise, ex-situ strategies like botanical gardens, gene banks, and cryopreservation will play a critical role in ensuring long-term survival of endangered species.