What's new at Basel Zoo

A very special kind of brood care is currently on show in the Vivarium – a fish with only a Latin name, Bujurquina oenolaemus, is practically taking its children sledging. Piscine brood care is incredibly diverse, ranging from simple spawning to mouth breeding to even giving birth to live young among certain fish species (as well as mammals).

The Bujurquina cichlid from Bolivia has a style of its very own when it comes to reproduction. The female lays up to 400 eggs, which she sticks to fallen leaves on the river bottom. First, the cichlid parents select a leaf and give it a thorough cleaning. They have a very good reason for this: the eggs themselves are sticky and, when laid carefully and simultaneously fertilised, adhere instantly to the ‘clean’ surface. This adhesion then makes the eggs extremely easy to guard and they are not carried away by the current. The eggs are also mobile so that when under threat, by a predator for example, the Bujurquina cichlids can grab the egg-laden leaf and whisk it away. It almost looks like a happy family outing with a pram or sledge.

An unusual way to protect their fry

This is indeed very unique behaviour for fish! After a few days, the eggs will have developed enough to hatch into tiny larvae. They still have a large yolk sac under their bellies which serves as a food reserve. The parents take even more care of the brood at this point. They watch over the tiny fry and take them into their mouths. There, they are protected from other hungry fish and can grow in their mother’s mouth until they become independent.

Stocks believed to be endangered

The Bujurquina cichlid was discovered by King Leopold III of Belgium (!) in 1977 but was only described scientifically in 1987. They are only found in a small distribution area in Bolivia and are believed to be endangered. The DCG (German Cichlid Society) has therefore launched a conservation programme. Aside from a few viviparous species, all fish lay eggs. The eggs are usually simply laid in the water and then left to their own devices. Unprotected, most of these eggs and the young hatchlings are eaten. This is why species that do not protect their young produce a large number of eggs. The more eggs that are laid, the better the chances that a few of them will survive to develop into adult fish. Other species invest in very different, sometimes even exotic, forms of brood care. The more intensive the brood care, the higher the reproductive success, which means that fewer eggs have to be laid.

Various types of brood care behaviour

Fish demonstrate an incredible wealth of different brood care behaviours. Salmon and trout dig shallow pits in the river bottom, where they lay and fertilise their eggs and where these then develop on their own. Angelfish ‘mount’ sticky eggs onto water plants and then guard and clean them regularly. Shell dwelling cichlids rear their young in empty snail shells, and cardinalfish brood their modest number of eggs in their mouths.

Bujurquina cichlids can be seen in aquarium 34 and there are usually dozens of other examples of brood care to be seen in the zoo’s other aquariums!