Dead Squid Moms Are a Gift to the Ocean Floor

By Elizabeth Preston | December 22, 2017 11:29 am

Image captured from a video camera mounted on underwater remotely operated vehicle DocRicketts on dive number 344. The original MBARI video tape number is D0344-02HD. This image is from timecode 01:18:55:10 and time Sun Feb 26 14:51:02 2012 GMT. The recorded edited location and environmental measurements at time of capture are Lat= 24.409134 Lon= -109.883450 Depth= 1252.64 m Temp= 3.537 C Sal= 34.575 PSU Oxy= 1.915 ml/l Xmiss= 86.75%. The Video Annotation and Reference system concept: associations for this image is 'Gonatidae: identity-reference 3, life-stage dead, image-quality good'.

Animals living on the ocean floor, where it’s too dark for anything to grow, have to wait for food to fall on them. Mostly this means they eat “marine snow,” a steady drift of tiny life forms and detritus from the ocean’s surface. But robotic expeditions off the coast of Mexico have revealed what might be another major dining option on the ocean floor: dead squid moms.

The Monterey Bay Aquarium Research Institute (MBARI) sent one of its remotely operated vehicles to explore deep basins in the Gulf of California between 2012 and 2015. With its cameras, the robotic submarine captured a surprising number of squid carcasses.

Eleven out of 80 dives came across sites where squid had fallen to the ocean floor. In the videos, researchers saw not just squid bodies, but crumpled black sheets that had fallen with the squid, as in the photo above. These were the remains of squid egg sheets. Certain squid called gonatids carry these sheets—embedded with developing embryos, and apparently darkened with ink—in their arms until their babies hatch.

Gonatids, like other squid, have short life spans. Male and female squid both die after they’ve reproduced. Some types of female squid start to physically disintegrate while they’re still making their eggs, then float to the surface and are eaten by birds after they’ve released the eggs. But in the Gulf of California, many squid moms appear to sink after their babies hatch, still clutching their egg sheets. The researchers also found squid egg sheets on the ocean floor without carcasses, and assumed these sheets fell with squid that had already been eaten.

Between carcasses and empty egg sheets, the researchers saw the remains of 64 squid on these dives. They spotted sea stars, crabs, and other scavengers feasting on the carcasses—though the scientists note that these animals weren’t as enthusiastic about eating the egg sheets, which may be “less palatable.”

Extrapolating to the whole region, the authors calculate that fallen squid may be a major and overlooked part of the ocean-floor food chain. As climate change seems to be increasing squid populations, that means expired squid moms may be more and more on the menu.


Image: MBARI

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Inkfish

Like the wily and many-armed cephalopod, Inkfish reaches into the far corners of science news and brings you back surprises (and the occasional sea creature). The ink is virtual but the research is real.

About Elizabeth Preston

Elizabeth Preston is a science writer whose articles have appeared in publications including Slate, Nautilus, and National Geographic. She's also the former editor of the children's science magazine Muse, where she still writes in the voice of a know-it-all bovine. She lives in Massachusetts. Read more and see her other writing here.

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