Squid 1, Shark 0


From HURL http://www.soest.hawaii.edu/HURL/animals/id/mollusks/cephalopods/spac/pages/HURLCephalopods2_001.htm

In the South Pacific, hovering over the peaks of seamounts at depths more than one kilometer deep swims a squid. This dark red squid, Idioteuthis cordiformis, well over one meter in length (3.2 feet) hovers here…waiting.   Other species in the whip lash squid family are diminutive with microscopic suckers. These species likely feed by dangling their tentacles waiting for prey to come near, merely passive predators. But Idioteuthis cordiformis is much larger with suckers so big other whip lash squid blush when they see them. Clearly Idioteuthis cordiformis cannot be a passive predator.


From HURLhttp://www.soest.hawaii.edu/HURL/animals/id/mollusks/cephalopods/spac/pages/HURLCephalopods2_002.htm

New work by Heather Braid and Kathrin Bolstad sequences the gut contents of this squid of the deep to shed light on this large red squid’s eating habits. The sequence data do indeed suggest that Idioteuthis cordiformis is an active predator…sometimes on sharks. DNA sequences in the gut matched the species birdbeak dogfish, Deania calcea, a deep-sea shark that can get over 1.2 meters (nearly 4 feet) and has a hankering for lots of shrimp.

From OceanLab http://www.eu-fp7-coralfish.net/gallery/oceanlab_images_may08/gallery_oceanlab_may09.php

Shark get in the squid’s belly! From OceanLab http://www.eu-fp7-coralfish.net/gallery/oceanlab_images_may08/gallery_oceanlab_may09.php

Braid and Bolstad also examined stable isotopes for Idioteuthis cordiformis. Nitrogen is an important elements obtained from eating other stuff. The old adage “you are what you eat” is actually true to some extent. Each animal has a slightly different signature of stable isotope ratios that reflect the signature of preferred food items. The nitrogen isotopes, specifically Nitrogen-15 (N15), can show how high up the food chain an animal is. As organism eat each other, N15 is transferred to the predator. Thus, top predators have the highest N15 values. Idioteuthis cordiformis? The nitrogen values place this squid much higher than quite a few other squids including Architeuthis dux, the giant squid. Only one squid clearly beats out Idioteuthis cordiformis, the Humboldt squid, Dosidicus gigas, a voracious predatory squid from closer to the surface. Don’t believe just watch this video. Even other squids don’t stand a chance next to the Humboldt squid.

Braid, H., & Bolstad, K. (2014). Feeding ecology of the largest mastigoteuthid squid species, Idioteuthis cordiformis (Cephalopoda, Mastigoteuthidae) Marine Ecology Progress Series, 515, 275-279 DOI: 10.3354/meps11008

Dr. M (1801 Posts)

Craig McClain is the Executive Director of the Lousiana University Marine Consortium. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Additionally, Craig is obsessed with the size of things. Sometimes this translated into actually scientific research. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (http://deepseanews.com/), a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.