Cuttlefish sex ratio

(written by lawrence krubner, however indented passages are often quotes). You can contact lawrence at: lawrence@krubner.com

I wonder why some species have such lopsided ratios of male/female?

Male cuttlefish challenge one another for dominance and the best den during mating season. During this challenge, no direct contact is usually made. The animals will threaten each other until one of them backs down and swims away. Eventually, the larger male cuttlefish mate with the females by grabbing them with their tentacles, turning the female so that the two animals are face-to-face, then using a specialized tentacle to insert sperm sacs into an opening near the female’s mouth. The male then guards the female until she lays the eggs a few hours later.

On occasion, a large competitor arrives to threaten the male cuttlefish. In these instances, the male will first attempt to intimidate the other fish. If the competitor does not flee, the male will eventually attack it to force it away. The cuttlefish that can paralyze the other first, by forcing near its mouth, wins the fight and the female. Since there are, on average, four or five ( and sometimes as many as ten) males for every female, this kind of behavior is inevitable.

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