Rummynose tetras shed light on schooling


A study undertaken on the Brilliant rummynose tetra has shed new light on the ways in which fish use their lateral line sensory system in helping them to school.

The lateral line system in fishes is of key importance in helping them to school, according to a study by scientists from the Université de Liège, Belgium published in the most recent issue of the journal Animal Behaviour.  

Karine Faucher and coauthors examined the role of the laterosensory system in schooling of the Brilliant rummy-nosed tetra (Hemigrammus bleheri).

While the lateral line system has been known to be important for the maintenance of a school in fishes, it is thought that sight is just as important.  

Previous studies have demonstrated that cutting the lateral line in fishes does not prevent them from schooling properly unless the fishes had also been blinded.  

However, this conclusion had been based on experiments where only the trunk (body) laterosensory system was inactivated, leaving the head laterosensory system intact.

The study by Faucher et al. inactivated the entire laterosensory system of the subject fish with aminoglycoside antibiotics, and observing their schooling behaviour via video recordings.  

The schooling behaviour of the experimentally treated fish and the sham-treated controls were quantified using the following parameters: nearest distance to the first, second and third neighbours, shoal radius, shoal order parameter and the number of collisions between individuals.  

The authors found that the fishes with the inactivated laterosensory system formed looser aggregations, had fewer fish swimming in the same direction and collided more frequently with each other, implying that fish totally deprived of the laterosensory system (both trunk and head) cannot maintain a school, and that they move apart instead of moving closer.  This indicates that the laterosensory system is more crucial to schooling than previously supposed.

The authors also confirmed damage to the superficial neuromasts (the sensory cells that make up the laterosensory system) by examining the treated fishes under a scanning electron microscope.  

The antibiotic-induced damage was temporary, and the fishes recovered both normal neuromasts and schooling behaviour in about a month.

For more information, see the paper: Faucher, K, E Parmentier, C Becco, N Vandewalle and P Vandewalle (2010) Fish lateral system is required for accurate control of shoaling behaviour. Animal Behaviour 79, pp. 679–687.