What’s the News: In the squid world, the body size of male spear squid determines the mating strategies they use. Small male squid, which have no chance of physically competing with their larger rivals, must try to get with the females of the species on the sly. Now, researchers in Tokyo have learned that this difference in mating behavior has resulted in the evolution of divergent sperm types, though perhaps not in the way you’d think: diminutive male squid actually produce larger sperm than big male squid.

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“Massive acoustic trauma.” It sounds like an ’80s metal band, but according to scientists at the Technical University of Catalonia in Spain, it’s what happens to squid and other cephalopods when they are exposed to sounds similar to boat noise. After exposing 87 cephalopods to low-volume, low-frequency noises for two hours, the researchers found damaged nerves, lesions, and other trauma in the creatures’ hearing organs. There are some holes in the team’s methods (see below), but if the findings hold, squid will be added to the long list of marine animals (including whales, dolphins, and crustaceans) endangered by human-made noise in the oceans.

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Yesterday we reported on a new study that showed shining a laser on certain neurons in mice brains could make them angry and aggressive. But with squid, you don’t need a laser to make the males get mean. All you need is to expose them to a particular chemical. From DISCOVER blogger Ed Yong:

In a flash, schools of male longfin squid can turn from peaceful gatherings to violent mobs. One minute, individuals are swimming together in peace; the next, they’re attacking one another. The males give chase, ramming each other in the sides and grappling with their tentacles.

These sudden bouts of violence are the doing of the female squid. Males are attracted to the sight of eggs, and females lace the eggs with a chemical that transforms the males into aggressive brutes.

For plenty more about how this chemical whips the males into an angry frenzy—and why—check out the rest of Ed’s post at Not Exactly Rocket Science.

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Chalk up another potential victim of global warming. A new study warns that the jumbo squid (also known as the Humboldt squid) may not fare well in the coming decades, as the oceans get warmer and absorb carbon dioxide from the atmosphere, which makes the water more acidic. Jumbo squid blood carries very little oxygen – with each cycle through its body, the oxygen can be used up entirely. This means they must “recharge” constantly, and makes the animals very dependent on what oxygen is available in the water around them. Yet, the warmer water is, the smaller the amount of oxygen it can hold [New Scientist].

What’s more, the squid’s blood cells can carry less oxygen in acidic water. Their blood-oxygen delivery system is highly sensitive to pH, so “the organisms are thought to live chronically ‘on the edge of oxygen limitation,’” the authors wrote. During the day, the squid descend to lower depths in the ocean to rest, slowing down their metabolism to deal with the lower oxygen levels there. At night, they return to well-oxygenated waters nearer the surface to feed [LiveScience]. However, if surface waters are both warmer and more acidic, the squid trying to feed at the surface will get much less oxygen, which will slow down their metabolisms. And lethargic squid are easy targets for predators like sperm whales, researchers say.

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