Lovelorn fish show they have feelings, too

FISH separated from their mates pine for each other and become pessimistic, scientists have found, challenging the belief that sexual emotional attachment is unique to humans.

Researchers at the University of Burgundy in France allowed 33 convict cichlids to spend two days choosing a mate, then monitored their behaviour for three weeks when paired with a fish they had not picked.

Experiments showed that when females were kept from their preferred mate they spawned later, spent less time looking after their eggs and had fewer fry. In a second test, the fish were taught to open a black box of food, but leave a white box that was empty.

However, when presented with an ambiguous grey box, the separated fish took nearly twice as long to look inside, proving their feelings were less optimistic, the scientists said.

“There is increasing evidence that non-human animals experience similar emotions to humans,” wrote lead author Dr Chloé Laubu in the journal Royal Proceedings of the Royal Society B.

“Our results suggest that the relationship between affective state and pair-bonding has evolved not only in humans but also in at least one other monogamous species – the convict cichlid.”

The convict cichlid Amatitlania siquia, which is native to Central America, was chosen because it is a monogamous fish that forms long-lasting pairings, with strong cooperation between the parents for parental care.