Spiders are primarily terrestrial creatures. While their presence near water might seem counterintuitive, some spider species exhibit remarkable capabilities, allowing them to survive, and even thrive, beneath the surface. This raises the question of how long these arachnids can persist in an aquatic environment, a duration that varies significantly depending on their biological adaptations.
How Spiders Breathe
Spiders possess specialized respiratory systems designed for air breathing, including book lungs and tracheae. Book lungs are located in cavities within the abdomen, featuring thin, stacked plates that facilitate gas exchange. Many spiders also have tracheae, a system of small tubes that transport air directly to tissues, opening to the exterior through spiracles. These air-dependent systems necessitate atmospheric oxygen; when submerged, they cannot extract oxygen from water, posing a threat to respiration. Water can block spiracles and flood book lungs, leading to suffocation.
Ingenious Aquatic Adaptations
Despite their air-breathing nature, certain spiders have evolved adaptations for underwater survival. One common mechanism involves dense, water-repellent (hydrophobic) hairs covering their bodies, particularly on the abdomen and legs. When submerged, these hairs trap a thin layer of air around the spider, creating a silvery film or “plastron.” This trapped air acts as a physical gill, allowing oxygen to diffuse from the surrounding water into the bubble while carbon dioxide diffuses out.
The diving bell spider, Argyroneta aquatica, found in freshwater habitats across Europe and Asia, exemplifies aquatic adaptation. This spider constructs a dome-shaped web, or “diving bell,” anchored to submerged plants, which it then fills with air carried from the surface. This silk structure functions as a permanent underwater habitat and a physical gill, continuously exchanging gases with the water. The spider only needs to surface occasionally to replenish the air in its bell, enabling it to hunt, eat, mate, and lay eggs entirely underwater.
Factors Influencing Underwater Lifespan
The duration a spider can survive underwater varies greatly between species and circumstances. For most terrestrial spiders, accidental submersion results in a short survival time, often minutes or less. However, some species, like certain tropical spiders, can endure submersion for up to 30 minutes by maintaining a film of air around their bodies. The salt marsh wolf spider can survive up to 40 hours underwater by entering a state of suspended animation, reducing its metabolic rate. For truly aquatic species like the diving bell spider, survival extends, with individuals living their entire lives underwater and reaching lifespans of up to two years in captivity.
Several factors influence their underwater lifespan. The size of the spider’s air bubble or diving bell directly impacts its oxygen reserves and gas exchange capacity; larger bubbles support longer submersion. The dissolved oxygen content of the water is also important, as higher concentrations facilitate oxygen uptake. Water temperature plays a role, with colder water holding more dissolved oxygen and slowing the spider’s metabolic rate, thereby reducing its oxygen consumption. A spider’s activity level affects its underwater endurance; an active spider consumes oxygen more rapidly, shortening its survival time, and nitrogen diffusion out of the air bubble causes gradual shrinkage, necessitating periodic replenishment from the surface.