Some male cuttlefish seem to squirt out ink to enhance their courtship displays, offering the first evidence that cephalopod ink has uses beyond just fighting and defence against predators.
Andrea cuttlefish (Sepia andreana) are unusual among cuttlefish because males sport a pair of long arms that aren鈥檛 seen in females. But despite these strong sex-associated characteristics, little was known about this species鈥� reproduction, says at the University of Tokyo.
In lab aquaria, the researchers recorded and categorised male and female Andrea cuttlefish behaviours during courtship and discovered that they were unlike any previously documented.
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Some males would guide a female to the sandy aquarium bottom and stroke her back and head with their long arms, occasionally stopping to squirt small blobs of ink above her. The researchers think the dense blobs may spook the female and keep her closer to the bottom during the male鈥檚 dance.
For his big finale, the male dispersed a larger cloud of ink and swam through it, like a stage performer emerging through theatrical fog. He then turned pale and iridescent, dramatically stretching his long arms and body like pulled taffy, and pulsed dark bands of colour along one of the long arms.
At first, the researchers thought it was just a coincidence that a male used ink during the courtship performance, says Nakayama. But since they then discovered that all the males released ink in the same way, the researchers now believe it is a key part of the courtship.
The diffuse ink cloud may act like mood lighting, temporarily darkening the area and obscuring the surroundings, which might visually magnify the male鈥檚 flamboyant patterning and colouration, says Nakayama.
at the Marine Biological Laboratory in Woods Hole, Massachusetts, is particularly fascinated by how the male cuttlefish stroke the females with their long, extended arms during the display. This is highly unusual behaviour for cephalopods.
鈥淭his touchy-feely thing, cephalopods don鈥檛 do that,鈥� says Hanlon, except when they are fighting over food or mates, or touching briefly when guarding a mate.
鈥淏irds have some of the most exotic and complex male courtship displays known in the animal kingdom,鈥� says Hanlon. 鈥淭he courtship displays in this paper show comparable complexity, something that is generally not expected in invertebrate animals.鈥�
Ecology and Evolution
