The question of whether a spider can survive in water is common, often fueled by accidental encounters in sinks or pools. The answer depends entirely on the spider’s species and the duration of the exposure. While most terrestrial spiders cannot live permanently underwater, they possess physical adaptations that allow them to survive temporary submersion. These survival strategies range from passive, short-term mechanisms to highly specialized, long-term habitats.
The Temporary Survival Mechanism
Most non-aquatic spiders rely on a passive, physical defense mechanism to survive short periods of submersion. Their bodies are covered in a dense layer of minute, specialized hairs known as setae. These hairs are extremely hydrophobic, meaning they actively repel water due to their chemical and physical structure.
When a spider is forced underwater, this coating of water-repellent hairs traps a thin, silvery layer of air around its body, particularly over the abdomen where the respiratory openings are located. This trapped air bubble functions as a temporary physical gill, technically referred to as a plastron. The spider’s book lungs and tracheal system draw oxygen from this air reservoir, allowing it to continue breathing while submerged.
This temporary plastron is effective for accidental dunkings, such as being washed down a drain or caught in a brief flood. The layer of air provides a small, mobile oxygen supply that sustains the spider until it can climb out. The air bubble’s efficiency is limited, serving primarily as a mechanism for surviving an unexpected incident rather than prolonged aquatic life.
Spiders Adapted to Live Underwater
A few spider species have evolved beyond temporary defense, adapting to an almost entirely aquatic existence. The most notable example is the Diving Bell Spider, Argyroneta aquatica, which is the only species known to spend virtually its entire life submerged. This spider actively constructs a sophisticated underwater habitat that functions as an external lung.
The spider builds a dome-shaped web of silk anchored to aquatic vegetation. It makes repeated trips to the surface to collect air, transporting the bubbles down and trapping them beneath the structure until the bell is inflated. This silk bell acts as a stable air reservoir, which the spider uses for resting, feeding, mating, and raising its young.
The diving bell functions as a true physical gill. As the spider consumes oxygen, the partial pressure inside the dome drops below the level in the surrounding water. This pressure difference causes dissolved oxygen from the water to diffuse into the bell, constantly replenishing the air supply. Although the bell slowly loses nitrogen, necessitating occasional trips to the surface for a fresh bubble, the diffusion process allows the spider to remain submerged for extended periods.
Water Surface Movement
Spiders often interact with water surfaces without needing to submerge their bodies. Their lightweight structure and hydrophobic leg hairs allow them to utilize surface tension. The water-repellent hairs on their tarsi (feet) prevent the surface tension from breaking, enabling them to stand on the water’s surface film.
Some species, such as Raft Spiders (Dolomedes species), “skate” or walk across the water by pushing their legs against the surface film. This movement creates tiny dimples, and the force exerted against the surface tension propels the spider forward. This behavior is often employed for hunting aquatic prey or escaping predators.
Related to aerial dispersal known as ballooning, some spiders can “sail” across the water. After landing, they raise their legs or abdomen into the air to catch the wind. This posture allows them to use their bodies as a sail, transforming the water surface into a temporary mode of travel for dispersal or survival.
Limits of Submersion Endurance
The limit to a spider’s submersion endurance, even with its temporary air bubble, is the depletion of its oxygen supply. While the trapped air bubble acts as a physical gill, its ability to extract dissolved oxygen from the water is finite. Over time, the oxygen in the bubble is consumed by respiration, and the concentration of carbon dioxide increases.
This process leads to hypoxia, or oxygen deprivation, which is the biological cause of “drowning” for an air-breathing organism. Higher water temperatures accelerate the spider’s metabolic rate, causing it to consume trapped oxygen more quickly and shortening its survival time. Additionally, prolonged submersion can compromise the hydrophobic hair layer, causing the plastron to fail and wetting the respiratory structures.
A terrestrial spider can survive underwater generally from a few hours to a full day, depending on the species and water conditions. Once the trapped air is depleted and the spider cannot reach the surface, its internal respiratory organs fail due to lack of oxygen exchange. This physiological failure marks the limit of its submersion tolerance.