The proximate cause of the eye beat behaviour in the Pacific white shrimp (Penaeus vannamei)
Résumé
The well-being of farmed animals needs to be considered to improve zootechnical performances. Animal welfare can be assessed by measuring stress behaviours. The shrimp Penaeus vannamei is one of the most bred crustacean species in the world. Studies on P. vannamei reported an increase in the number of loops and tail flips in stressful situations. One study identifies the eye beat behaviour – in which the shrimp strike their eyes together above their head – as a stress marker whereas another suggested that this behaviour had a function of cleaning. In a recent study, we found that in a stressful situation (intense light condition) the number of loops and tail flips increased, but not that of eye beats, suggesting that this behaviour may not be related to stress. The objective of this study is thus to investigate the proximate causes of the eye beat behaviour in P. vannamei shrimp. Twenty PL20 P. vannamei shrimp were filmed in each of the four conditions: alone, alone with a mirror, separated from a conspecific with a plexiglass wall and in dyads in the same tank. Two light conditions were tested: white and infra-red lights. The number of eye beats was measured for each shrimp in each condition. Given the economic importance of P. vannamei, a better understanding of the eye beat behaviour is paramount to distinguish stress behaviours from other behaviours, to improve well-being in farm conditions.