Most spiders inhabit terrestrial environments, but a single species stands out for its unique ability to live almost entirely submerged in water. This exception demonstrates a remarkable adaptation within the arachnid world, challenging common perceptions about where spiders can thrive. The majority of spider species, however, are not equipped for an aquatic existence and can only survive brief encounters with water through temporary measures.
The True Aquatic Spider
The diving bell spider, Argyroneta aquatica, is the only known spider species that spends nearly its entire life cycle underwater. It constructs an elaborate underwater home from silk. This bell is anchored to aquatic plants in freshwater habitats across Europe and Asia.
The spider fills its silk structure with air collected from the water’s surface, carried down by a dense layer of hydrophobic hairs on its abdomen and legs. This trapped air bubble functions as a “physical gill,” allowing the spider to extract dissolved oxygen from the surrounding water and release carbon dioxide. The diving bell serves as a multi-purpose dwelling where the spider rests, consumes prey, mates, lays eggs, and overwinters, only surfacing periodically to replenish its air supply. This unique adaptation enables Argyroneta aquatica to maintain an oxygen-rich environment for extended periods, sometimes for more than a day, allowing it to thrive in its aquatic niche.
Temporary Water Survival Strategies
Many spider species, despite being primarily terrestrial, exhibit various strategies to survive brief periods in or on water. Some spiders can trap a thin film of air around their bodies, held by their hydrophobic hairs, which repels water and keeps their respiratory openings dry. This air film gives their bodies a silvery appearance underwater and provides a temporary oxygen supply.
Other spiders, like fishing spiders or wolf spiders, can walk or glide across the water’s surface due to their lightweight bodies and the water’s surface tension. They may also submerge themselves voluntarily for short durations, often as an escape mechanism from predators. Some species can enter a coma-like state during inundation, reducing their metabolic rate and extending their underwater survival time, sometimes for several hours.
Why Most Spiders Cannot Live Underwater
Most spider species cannot sustain prolonged periods underwater due to physiological limitations. Spiders are air-breathing arthropods, relying on atmospheric oxygen for respiration. They possess specialized respiratory organs, such as book lungs and tracheae, which are designed to exchange gases with air, not water.
Book lungs feature plate-like structures where hemolymph facilitates gas exchange with air through slits on the abdomen. These respiratory systems cannot efficiently extract dissolved oxygen from water, making long-term submersion fatal. An aquatic environment also presents significant challenges for movement, hunting, and reproduction for spiders not specifically adapted for it. Without specialized adaptations like the diving bell, most spiders would quickly succumb to oxygen deprivation if submerged.