Nematodes are microscopic roundworms found in nearly every environment on Earth, including diverse aquatic habitats. Their survival in water is highly dependent on a range of factors.
Nematode Lifespan in Water
The duration nematodes remain active in water varies considerably among species. Many free-living nematodes live from a few days to several weeks, and some may even persist for months under optimal conditions. Beneficial nematodes, used in pest control, typically survive a few hours in a water solution once mixed, though this can extend to several days or weeks if kept refrigerated in a moist medium.
Environmental Factors Influencing Survival
Several environmental factors influence nematode survival in aquatic environments. Temperature plays a substantial role; warmer water shortens active lifespans, while colder temperatures extend them. Extreme temperatures, both hot and cold, can be detrimental.
Dissolved oxygen is important for most nematodes, as they require it for energy. Insufficient oxygen can severely limit survival, sometimes to just a few hours. Nutrient availability, such as bacteria, algae, and organic matter, provides necessary food sources.
Water purity and toxins also affect nematode survival; pollutants, chemicals, or extreme pH levels can be lethal. Salinity is another consideration, as freshwater species cannot tolerate high salt concentrations, while marine species are adapted to them. Predators and pathogens can further reduce populations.
Strategies for Surviving Water Extremes
Some nematodes possess remarkable biological mechanisms that allow them to endure adverse water conditions, or even its complete absence, extending their survival far beyond their active lifespan. Anhydrobiosis is one such strategy, where certain species can enter a dormant state by losing almost all their body water, forming a protective “tun” structure. This allows them to survive extreme desiccation and rehydrate when water becomes available again.
Cryptobiosis is a broader term encompassing various states of suspended metabolism in response to environmental stressors, including desiccation, freezing (cryobiosis), and lack of oxygen (anoxybiosis). In this state, metabolic processes slow to nearly undetectable levels, preventing reproduction and development. A notable example includes nematodes revived after 46,000 years in Siberian permafrost, demonstrating the remarkable potential of cryptobiosis for long-term survival. Diapause, a period of suspended development often triggered by environmental cues, also helps some species persist through unfavorable water conditions by pausing their life cycle until conditions improve.
Handling Nematodes in Water
Practical considerations arise when handling nematodes, particularly beneficial species used in agriculture and gardening. Live beneficial nematodes are often shipped in a moist medium and should be stored in a refrigerator, where they can remain viable for two to three months, or sometimes up to 20 months, before use. Once mixed into a water solution for application, these nematodes should be used promptly, ideally within three to four hours, as they can drown in non-aerated water.
When applying beneficial nematodes, using chlorine-free or dechlorinated water is important, as chlorine can harm them. The treated area should be kept moist for several weeks after application to allow the nematodes to move and establish themselves in the soil. In home environments, nuisance nematodes might occasionally appear in standing water, such as in drains or plant saucers, though these are typically harmless and their survival duration depends on the water quality and presence of food sources. Water treatment facilities work to remove nematodes from drinking water, as they can sometimes shelter bacteria and resist disinfectants, underscoring the need for effective filtration and treatment processes.