The diving bell spider, Argyroneta aquatica, stands out among arachnids as the only known spider to spend its entire life submerged underwater. This remarkable creature navigates its aquatic world by constructing and maintaining a unique air-filled habitat, often referred to as a “diving bell.” This ingenious adaptation allows the spider to survive in an environment where most spiders would perish, prompting curiosity about how it manages to feed and thrive within this unusual setting.
A Unique Aquatic Environment
The diving bell spider’s survival hinges on its specialized underwater dwelling. This structure is a silk web anchored to aquatic vegetation, into which the spider transports air from the surface, creating a dome-shaped bubble. Functioning as a physical gill, the bell allows the spider to extract dissolved oxygen from the surrounding water, reducing its need to frequently surface for air. This air supply serves as its home, a breathing apparatus, and a base for all its activities, including molting, mating, and egg-laying. The bell’s integrity and oxygen exchange capabilities are important for the spider’s underwater life.
The Diving Bell Spider’s Diet
The diving bell spider’s diet consists primarily of small aquatic invertebrates found within its freshwater habitat. Common prey items include mosquito larvae, water fleas (Daphnia), aquatic isopods such as Asellus aquaticus, and other small crustaceans. Phantom midge larvae, water mites, and mayfly nymphs are also consumed. While they mainly feed on these smaller organisms, they have also been observed to prey on small fish, tadpoles, and even other water spiders. Their diet is influenced by the availability of prey in their local ponds, slow-moving streams, or marshy environments.
Capturing and Consuming Prey
The diving bell spider employs hunting techniques adapted to its underwater lifestyle. It waits within or near its air bell, extending silk threads into the surrounding water. These threads act as snare lines, detecting vibrations from passing aquatic prey. When a vibration is sensed, the spider darts out from its bell to ambush the invertebrate.
Once captured, prey is brought back into the diving bell for consumption. Inside the bell, the spider injects venom through its fangs, which paralyzes and liquefies the prey’s internal tissues. The spider then consumes the liquefied contents, benefiting from the air-filled environment of the bell to prevent dilution of digestive juices. This method allows the spider to process its meals efficiently without leaving its underwater home.