January 30, 2017 by Domino Joyce, The Conversation
The males of some species go to extraordinary lengths to attract females – but some simply cheat. Take African cichlid fish. Many males build underwater "sandcastle" structures that the females use to judge the quality of their potential mates. But, as my colleagues and I found out during a recent study, some males don't bother with this show of construction prowess, and instead are able to father offspring by engaging in "sneaky mating".
There are hundreds of species of colourful cichlid fish in Lake Malawi, Africa, and about two hundred of these build pit- or volcano-shaped structures known as "bowers" out of sand. Each species builds a slightly different type of sand bower, and they function as a signal of male quality, both to other males, and to females.
The females are what are known as mouthbrooders. After courtship with their male partners, which takes place on top of the bower, the females lay eggs and pick them up in their mouths. The males then fertilise the eggs while they are still in the females' mouths.
The females then carry the eggs for about three weeks until they hatch into baby fish known as "fry". The male contributes no parental care, nothing but his genetic material. So the females need to ensure they choose high quality males, and they use the shape of his bower to do this.
The males even help the females to do this by congregating in breeding arenas called "leks". The females can then visit a lek and judge a large number of males at once, usually laying only a handful of eggs with each chosen male. The ability to build and defend a bower in this hotbed of male activity is thought to demonstrate the quality of the male to the females. It takes two to three weeks for each male to build his bower and he has to work hard to maintain it over a breeding season of several weeks