Researchers Find Spiders’ Suicide Mechanism for Sake of Offspring

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The stegodyphus lineatus: making the ultimate sacrifice for their young. Photos by Dr. Mor Salomon

In many animal species the mother is responsible for feeding her family. But for some species of spider in Israel, including the stegodyphus lineatus, the mother’s body also becomes her offspring’s food after she dies, so that they can continue to develop. New Israeli research shows that this is not some sudden hunger attack, rather a process in which the mother’s body gradually prepares itself to be consumed.

The mechanism that allows this remarkable self-sacrifice was studied by Israeli researchers Dr. Mor Salomon, Prof. Moshe Kol, Prof. Yael Lubin and Dr. Eli Aflalo. The results of their research were published two weeks ago in the American publication Journal of Arachnology, under the heading “Dramatic histological changes preceding suicidal maternal care in the subsocial spider Stegodyphus lineatus.” 

The researchers collected female spiders from the northern Negev and Judean Desert and followed the changes occurring in the mother spider’s digestive system during the reproduction stage and while nurturing her offspring, in laboratory conditions. They noticed that while protecting the sperm sacks, the tissues inside the mother’s stomach already begin to break down. During this period the mother spider continues to weave cobwebs and catch prey so as to continue to stock food in their bodies.

After about 80 spiders hatch from the eggs, some of the mother’s stomach tissues become liquefied and are absorbed into her digestive system, including many nourishing substances resulting from consuming the prey. She regurgitates these substances in order to feed her offspring. At this stage she is no longer nourished by prey. "Our work shows that the process [of abdominal tissue degradation] is gradual, possibly in order to allow the female to produce another clutch of eggs in case something goes wrong with the first one," Salomon told the New Scientist. "Basically, most of the abdominal tissues are degenerated and become food for the young, which is quite extraordinary." 

But the process comes to a dramatic end after about two weeks – during which the young spiders double their weight - with the mother’s demise. At this stage the offspring turn to their late mother’s body – which already lost 41 percent of its mass due to the regurgitation - as their source of nutrition. In this way the mother completes the process of ensuring they have a reasonable chance of surviving into adulthood.

The researchers posit that this self-sacrifice mechanism evolved in order to improve the species’ chance of survival in the arid areas in which it lives, which often lack sufficient prey for their development.

The researchers note that there are other species of spider in which the offspring feed on their mother’s body, and intend to study the changes occurring in their digestive systems ahead of their descendant’s last supper.

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