When mom serves herself as dinner

Spider’s extreme motherhood ends with fatal family feast

KIDS TODAY  Tiny yellow spiderlings (shown close up) crowd over their gray mother, whom they will eventually eat.

Jorge Almeida/Flickr (CC BY-NC-ND 2.0)

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In a less squeamish universe, Mother’s Day cards would have a spider on them. She’s extreme in her generosity and sacrifice: tireless regurgitation, liquefying guts and the personal touch in family dinners.

Female Stegodyphus lineatus spiders spin loosely woven webs “like a ping-pong net,” says Mor Salomon of the Israel Cohen Institute for Biological Control in Yehud-Monosson, Israel.  She finds the webs in shrubbery along dry river beds in the Negev Desert. Protected inside a spider-size cave spun at one end of the web, a female creates what looks like a tiny silk hockey puck filled with 70 to 80 yellowish eggs.

When spiderlings hatch, they’re trapped in the puck. Mom pierces the protective silk to free them — and then she stops eating for the rest of her life. 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 mother’s midgut had already started breaking down while she guarded the eggs, Salomon and her colleagues report in the April Journal of Arachnology. And by the time the pale youngsters hatch, liquefied gut suitable for baby mouthparts is building up in her abdomen. 

As liquid wells out on mom’s face, spiderlings jostle for position, swarming over her head like a face mask of caramel-colored beads. This will be her sole brood of hatchlings, and she regurgitates 41 percent of her body mass to feed her spiderlings.

But her young take even more,possibly at her invitation. “She makes no attempt to escape,” Salomon says. Spiderlings pierce her abdomen with their mouthparts and over the course of several hours drain her innards.

At the beginning of the feeding, Salomon says, “if you touch a leg, she will pull it back. She’s definitely alive.” By the end, of course, she’s not. And she has contributed all but 4 percent of her body mass to offspring feeding. The liquefaction process that makes this possible proceeds in an orderly way, dissolving organs as they become expendable. One organ that remains till the end is mom’s heart.

The sticky, loose netting of a web spun by a female S. lineatus spider leads to her elongated, more tightly woven nest (center). Hanging in the web are husks of insects left over from her previous meals. M. Salomon
Spiderlings plump as beads jostle for position to feed on clear fluid (a regurgitated mix of past meals and liquefying maternal tissue) welling out of mom’s mouthparts. M. Salomon
Not much will be left of mom after spiderlings finish this final meal sucking her liquefied innards out. What triggers matriphagy in S. lineatus spiders isn’t clear, but in related species, mothers and offspring send web vibrations that apparently determine the start of the dinner. M. Salomon and Trine Bilde

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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