JORGE ALMEIDA/FLICKR (CC BY-NC-ND 2.0)

Young Spiders Cannibalise Mum to Get a Leg-Up on Life

MYLES GOUGH
27 APRIL 2015

Most mothers would do just about anything for their kids, and while this can be downright draining, it usually doesn't result in an untimely death.

But this doesn't ring true for all species.For a species of spider called Stegodyphus lineatus, motherhood has some irreversible and gruesome consequences.

 

After giving birth, these spider mothers regurgitate food for their young and then allow themselves to be cannibalised by their babies, making the ultimate sacrifice for reproductive success.

Entomologist Mor Salomon from the Hebrew University of Jerusalem in Israel recently studied this process of self-sacrifice - known as matriphagy - to see what, if any, changes take place in the mother's body as she prepares to be devoured.

Salomon found her spider specimens by seeking out their webs, which the spiders tend to spin in low-lying shrubs. She searched near dry riverbeds in the Negev Desert in southern Israel.

These webs are often attached to conical retreats, which are like silk-spun hollows. This is where the mothers come to lay their batches of eggs.

When the spiderlings hatch, the mother has to pierce the silk cocoon to free them. She then stops eating for the rest of her life - which isn't very far off.

As Susan Milius explains for Science News, "For the next two weeks or so, she feeds the dozens of young by regurgitating a transparent liquid. This slurry mixes what's left of her last meals plus some of her own guts."

The final stage in the process sees the mother become lunch.

But interestingly, Salomon and her team have discovered that the mother's body has begun preparing for this event in advance, with the tissue in her abdomen starting to break down and soften while she's still guarding her eggs.

This means that once her babies hatch, the tissue in her gut is soft enough for them to pierce, and begin eating, even with their juvenile mouth parts. And so, the cannibalisation of mum begins.

Milius from Science News describes the gory scene: "As liquid wells out on mum's face, spiderlings jostle for position, swarming over her head like a face mask of caramel-colored beads." 

Fun times. But for the mother, this's basically what she's been waiting her whole life to do. It's the only reproductive event in her lifetime, and she's going to make damn sure her offspring get the nutrients they need. Even if it means committing suicide. 

"She makes no attempt to escape," Salomon told Science News. "If you touch a leg, she will pull it back. She's definitely alive."

Over a period of several hours, the dozens of hatchlings drain her insides. When all's said and done, the mother has contributed all but 4 percent of her body mass to feeding her spider hatchlings, that now, presumably, have the strength they need to get on in life.

Strangely, the one organ they don't devour is the heart. The team has reported its findings in The Journal of Arachnology

It may sound like a healthy, protein-rich start to life for these young spiders, but it's still creeping me out thinking about it. And scarily enough, there are other freaky creatures that partake in matriphagy. 

Source: Science News