Diving Bell Spider: Aquatic Spiderman?


Introduction

Under the water, the Diving Bell spider or water spider (Argyroneta aquatica) displays a silvery appearance due to the presence of the air bubble surrounding its abdomen. Outside of the water, the water spider has a brown cephalothorax and a dark velvety abdomen. Like other spiders, the abdomen is covered with hairs, however the water spider uses these hairs to capture a bubble of air around its abdomen. Since the respiratory organs of spiders are located on their abdomens, the bubble serves as a supply of oxygen.


The water spider is the only spider that lives its life entirely underwater. It has been found to live in eutrophic lakes and ponds as well as marshes, swamps, and slow-moving streams in water of relatively low pH and dissolved oxygen concentration. Water spiders need water plants as anchors for their “bubble nests” as well as an attachment site after diving down in the water.


Development / Size

Males range from 7.8 to 18.7 mm in length, while females range from 7.8 to 13.1 mm. The tendency of males to be larger than females in this species is an anomaly amongst most spiders. This trend in the water spider is believed to occur because larger males have mobility advantages over smaller males in dense water environments. Larger body size in males is thought to have developed due to the male’s tendency toward increased mobility in hunting and seeking out mates.


Reproduction

The mating season starts in mid to late spring. Following copulation, the female produces a dense white egg sac holding 50-100 eggs, which completely fills the upper half of the nest. Although the number of viable offspring per egg sac decreases per laying event, water spiders are able to produce six egg sacs from one copulation event throughout a year. However, females that engage in more than one copulation event tend to be more reproductively successful by avoiding a sperm deficit. After she produces her egg sac the female also produces a thick partition separating the eggs from the lower half of the nest, where she continues to live. The female is left to guard the brood until they hatch, which in captivity was found to take three to four weeks. During this time, the female seldom leaves the bell and narrows the entrance by drawing together the edges.


After egg-laying the female water spider guards her brood until they leave her nest. Offspring leave their mother's nest between two and four weeks after hatching to build their own nests.



Predation & Food

Argyroneta aquatica is a carnivorous animal with a diet differing upon location but typically including water fleas, aquatic isopods such as Asellus aquaticus, insect larvae, fairy shrimp and even other water spiders. While males tend to be active hunters, females are sessile ambush predators.


Due to their superior diving and swimming ability, male water spiders tend to spend more time outside of the safety of the diving bell than females. In order to avoid predation, female and juvenile water spiders are known to spend more time in the diving bell, only leaving at night. Some predators of Argyoneta aquatica include adult and larval beetles, dragonfly larvae, frogs, and fish. Because water spiders can live in water of low pH and low dissolved oxygen concentration where many predatory fish cannot survive.


Random Facts

1. Water spiders have been found to live in captivity for two years.

2. Water spiders are helpful in reducing the number of mosquito larvae that survive to adulthood.

3. There are no known adverse effects of Argyroneta aquatica on humans, except a painful bite. :)


Video of Water Spider: https://www.nationalgeographic.com/science/phenomena/2011/06/09/the-diving-bell-and-the-spider/



Sourced From/More Information: Article: https://animaldiversity.org/accounts/Argyroneta_aquatica/ Images 1: https://www.nationalgeographic.com/science/phenomena/2011/06/09/the-diving-bell-and-the-spider/

Images 2: https://www.wired.com/2014/09/absurd-creature-week-incredible-spider-lives-entire-life-underwater/

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