The diving bell spider builds its own underwater gill to breathe without surfacing
In short: Most spiders avoid water, but Argyroneta aquatica has mastered it. By spinning a silk dome and filling it with air bubbles trapped in its body hairs, this spider creates a permanent underwater sanctuary. It is not just a home; it is a functioning, gas-exchanging gill that allows the spider to thrive.
The diving bell spider, or Argyroneta aquatica, is unique among its kind for spending nearly its entire life submerged in freshwater habitats across Europe and Asia. While other spiders may occasionally dive or live in semiaquatic environments, this species constructs a specialized, dome-shaped silk web between underwater plants. This structure serves as a home, a nursery for its eggs, and a staging ground for hunting aquatic insects and crustaceans.
The spider’s ability to remain underwater for extended periods relies on a sophisticated gas-exchange mechanism. By trapping air bubbles against its abdomen and legs using dense, water-repellent hairs, the spider transports oxygen from the surface to its web. Once inside, the bubble acts as a detachable gill. Because the oxygen concentration in the surrounding water is often higher than that within the bubble, oxygen naturally diffuses inward, while carbon dioxide diffuses out. Research by Roger Seymour and Stefan Hetz has shown that this process is so efficient that the spider can extract oxygen from even stagnant water, allowing it to stay submerged for more than a day without needing to replenish its supply.
Despite this efficiency, the spider must eventually return to the surface. Nitrogen tends to diffuse out of the bubble, causing the bell to shrink over time, which forces the spider to periodically collect more air to maintain the structure's integrity. Interestingly, the species exhibits unusual sexual dimorphism; males are typically 30% larger than females. While females spend most of their time inside their larger bells to care for offspring, males are more active hunters. This size difference is thought to help males overcome water resistance and buoyancy issues, though it imposes higher energy costs on the females who must maintain larger, more complex air-filled nurseries.
The diving bell itself is constructed from silk and a protein-based hydrogel. Beyond its function as a breathing apparatus, the bell is a vital site for mating and development. Before mating, a male may build a bell adjacent to a female's and construct a tunnel to gain entry. Once inside, the female lays between 30 and 70 eggs. This remarkable adaptation allows the spider to live, hunt, and reproduce entirely beneath the surface, turning the water into a permanent home.
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Sources
- Summary by Intellect · source: Water spider | Description, Diving Bell, Adaptations, Life Cycle, Diet, Habitat, & Facts | Britannica
- Also: The diving bell and the spider
- Also: Diving bell spider
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