When a female fish leaves eggs with a male she is trusting him not to abandon or eat them. But the females of one species do not leave this to chance. To choose the most caring father for their offspring, they set males a 'good parenting test'.
Prospective fathers of a species of mediterranean blenny (Aidablennius sphynx) are given a trial sample of eggs to look after. When a female returns a day or two later, she will not mate with the male if the eggs have gone (Animal Behaviour, vol 43, p 865).
Sarah Kraak and Eric van den Berghe studied the blenny both in the wild and in the laboratory. The biologists placed glass tubes in the rock crevices where males nested, to serve as artificial nests. The males took to the tubes, often guarding them for months on end.
Kraak and van den Berghe counted the eggs ...
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