Spiders, air-breathing arthropods, often prompt curiosity about their ability to survive underwater. Some species have developed remarkable adaptations allowing them to endure submerged conditions or even thrive in aquatic environments. Their survival hinges on unique biological mechanisms that manage air supply and metabolic processes.
How Spiders Breathe on Land
Spiders primarily breathe using specialized respiratory organs: book lungs and tracheae. Book lungs are internal structures located in the abdomen, composed of stacked, plate-like tissues that resemble the pages of a book. Air circulates between these plates, allowing oxygen to diffuse into the spider’s hemolymph, which is comparable to blood. Many spiders also possess a tracheal system, a network of branching tubes that deliver oxygen directly to their tissues. These systems are designed for efficient gas exchange in air, rendering them ineffective underwater, as spiders require oxygen for survival.
Ingenious Aquatic Adaptations
Some spiders exhibit extraordinary aquatic adaptations. The diving bell spider (Argyroneta aquatica) lives almost entirely underwater. This spider constructs a dome-shaped silken web, often anchored to aquatic plants, which it inflates with air brought from the surface. It transports air bubbles from the water’s surface by trapping them with a dense layer of hydrophobic hairs, creating a silvery film that acts as a temporary air supply.
The submerged air bubble functions as a “physical gill,” facilitating gas exchange with the surrounding water. Oxygen from the water diffuses into the bubble as the spider consumes it, while carbon dioxide, a waste product, diffuses out. This system allows the spider to remain submerged for extended periods, sometimes for more than 24 hours, only occasionally needing to surface to replenish the bubble as nitrogen slowly leaks out. Other semi-aquatic spiders, like fishing spiders, also use hydrophobic hairs to trap an air film, enabling them to submerge briefly for hunting or evasion.
How Long Can Spiders Survive Submerged?
For terrestrial spiders, involuntary submersion can be survived for surprising durations. Their survival time is influenced by several factors. Their low metabolic rate reduces oxygen demand. Some species can further slow their metabolic processes, entering a state of suspended animation to conserve oxygen.
The duration a spider can survive underwater varies significantly by species, water temperature, and oxygen levels in the water. Colder water generally holds more dissolved oxygen, potentially extending survival. Some, like the tropical spider Trechalea extensa, have been observed to hide underwater for up to 30 minutes. The salt marsh wolf spider (Arctosa fulvolineata) can endure submersion for up to 40 hours. Certain marine-associated spiders, such as Desis marina, can survive for as long as 19 days by trapping air in silken retreats and maintaining a very low respiratory rate.