Urine release in freely moving catheterised lobsters (Homarus americanus) with reference to feeding and social activities

Previous studies suggest that urine-borne pheromones play an important role in lobster agonistic and sexual behaviour. This paper investigates the pat tern of urine release in catheterised, but otherwise freely moving, adult l obsters with respect to feeding, social and non-social activities. Lobsters on average released 4.1 ml (1% of body mass) of urine over a 12 h period; this more than doubled to 10.6 ml over the 12 h period after feeding. Hourl y monitoring revealed that most urine was released in the first hour after feeding (2.84 ml). With the exception of the first hours after feeding, uri ne release was intermittent, with pauses lasting up to 17 h. The probabilit y of urine release per hour in unfed lobsters was 0.34 (median); this value increased during agonistic interactions elicited by the introduction of a conspecific (median 0.63) and during activity initiated by non-social distu rbance (median 0.56). Mean urine volume during output hours in unfed lobste rs amounted to 1.09 ml h(-1). This volume was significantly increased by th e presence of a conspecific (1.88 ml h(-l)) and decreased during activity i nitiated by non-social disturbances (0.56 ml h(-1)). No sex-specific differ ences in urine release were found. The data demonstrate that lobsters contr ol their urine release in a manner dependent on behavioural context. This s upports recent findings suggesting the use of urine for chemical signalling in agonistic interactions.