When it comes to aquatic spiders, there is one species that stands out: Argyroneta aquatica, the diving bell spider. This species is the only spider that spends its entire life under water. However, it is not a plastron breather, meaning its gas gill is compressible, and that although it spends its entire life under water, it must frequently make trips to the surface to replenish its bubble (Seymour and Hetz 2011).
It survives under the water by building a dome shaped web among underwater plants, and filling this “diving bell”, so named for its bell shape's nest, with air that it continuously collects from the surface of the water. This bell then does the same thing that the physical gill does for other species of aquatic insects and spiders: oxygen from the water diffuses in, providing the oxygen supply for the spider’s metabolic functions (Seymour and Hetz 2011).
Watch the diving bell spider in action:
The spider uses this air dome to perform many activities that require an increase in metabolic activity, including feeding, copulation, and oviposition (Seyyar and Demir 2009).
Although this spider is unique, it still demonstraits the same advantages of physical use gill as other gas gill respirators. In an investigation of the diving bell spider in Turkey, it was found that the diving bell spider was mostly found in ponds and small lakes with low pH and low dissolved oxygen (Seyyar and Demir 2009). Thus, this investigation of the diving bell spider supports the idea that the use of the physical gill allows the spider to exploit a niche not available to other animals with real gills that exchange gas directly with the water, as discussed previously.
The fact that the diving bell spider spends its entire life under water is not the only thing that makes this species of spider unique. It is also a unique species in that the males are larger than the females; this is a unique feature for a spider species (Schutz and Taborsky 2005).
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Pair of Diving bell spiders (♀ left, ♂ right), found at Wien Prater park in Vienna, Austria (Photo credit: Norbert Schuller Baupi)
This image illustrates the reversal in relative sizes of males and females in diving bell spiders.
The fact that the spider relies on a physical gill to spend its entire life underwater and its reversal of relative gender sizes of the diving bell spider are most likely related. In an investigation of sexual conflict within this species by Schutz and Taborsky (2005), they found that some of the limitations of the physical gill and limitations to life under water in general may be linked to the reversed sexual dimorphism in these spiders. Schutz and Taborsky found that females build larger bells than the males of this species, and concluded that it is possible that females may be smaller than the males due to the cost associated with building a larger bell (Schutz and Taborsky 2005). In one of their investigations, Schutz and Taborsky found that females bring fresh air from the surface to their bells more frequently than males. Because bell volume increases so greatly with body size, this may be a major limiting factor in female body size (Schutz and Taborsky 2003).
