A Dive into the Diving Spider
The diving spider, or water spider (Argyroneta aquatica) is perhaps one of the most unique arachnid species on Earth, noted for living almost entire life completely underwater. This species is found throughout northern Europe and Asia in clear freshwater ponds, lakes, wetlands, and slow-moving rivers with lots of aquatic vegetation.
Like other spiders, the water spider does breathe air. When submerged, specialized hydrophobic hairs create an air bubble attached to its abdomen, which allows the spider to store oxygen while moving around underwater. In addition, these spiders build a web known as diving-bell webs. These webs, constructed of spider silk, are constructed underwater, and supplied with air bubbles from the surface. A. aquatica spends most of its time in these webs, leaving only to replenish its air supply-- about once every 24 hours-- or to find prey.
The diving bell spider's prey are, unsurprisingly, primarily insects. In particular they feed on water fleas, aquatic isopods, insect larvae, and small crustaceans like shrimp. Individuals catch their prey by hiding inside their webs until prey trips one of the trip-wires constructed in the surrounding vegetation. They then surge out, seize their prey, and drag it back into the air-filled web where the spider can digest it. Predators of water spiders include aquatic beetles, dragonfly larvae, and frogs. Fish can also predate upon water spiders, but they are usually scarce due to the low aquatic oxygen environment in which the spiders live.
Ordinarily, A. aquatica is a fairly plain, brown spider. Males are slightly larger than females; 18.7 mm (0.74 in) to their 13.1 mm (0.51 in) in length; this is a rare phenomenon in spiders, as females are typically larger. Males also have a longer pair of front legs. However, females were found to construct much larger nests, as they must also provide space for their eggs and young.
When a male is ready to mate, which occurs during spring, he will construct several sperm packages that he holds in his palps, or mouth appendages, while he seeks out potential mates. If he finds a receptive mate, the two will engage in a swimming ritual around her web before he gives her one of his sperm packages. Afterwards, the female constructs a sac with 50-100 eggs; she may do this up to 6 times throughout a single year. The eggs hatch 3-4 weeks after laying, and the offspring remain in the nest for another 2-4 weeks. Individuals typically become sexually mature not long after, and may live up to 2 years in the wild.
The water spider can deliver a painful bite, with symptoms of inflammation, vomiting, and fever lasting 5-10 days. However, the bite is not known to be fatal to humans.
Conservation status: The diving bell spider has not been evaluated by the IUCN. The primary threat is likely habitat destruction, although at least one area in South Korea has been designated specifically as protected habitat for the species.
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Photos
Stephan Hetz
