Love calls from the bottom

Some men send flowers, others send chocolates. But one species of fish has a rather unusual method of seducing the opposite sex. Researchers at the Centre of Marine Science, University of Algarve, Portugal, have been studying how the peacock blenny fish secretes pheromones – chemical ‘love’ signals – from an anal gland.

Dr Eduardo Barata observed peacock blenny over the breeding season, when males occupy holes and crevices in the bottom of the sea which they use as nesting sites where females come to spawn. During the breeding season, males develop an androgen-dependent anal gland (AG) which is thought to be a source of substances that attract sexually active females to nesting sites.

Dr Barata will present the results of his study at the Society for Experimental Biology conference on Thursday 11 April. By performing attraction and choice tests in aquaria using water from males with or without AG, or water spiked or devoid of extracted AG, Dr Barata was able to show that female fish spent significantly more time with male fish with the anal gland, or with those in water ‘smelling’ of the anal pheromone. The lucky AG males also received more eggs in their nests. Dr Barata concludes that the anal gland plays a significant role in male reproductive success.

“This is the first time that such a phenomenon is demonstrated in fish, an external structure that seems specialised for the production/release of a sex pheromone,” said Dr Barata.