Chemical signaling lobster urine

Breithaupt T, Atema J (2000) The timing of chemical signaling with urine in dominance fights of male lobsters (Homarus americanus). Behav Ecol Sociobiol 49 67-78... 

This section reviews the complex currents lobsters generate to eliminate metabolites and broadcast chemical signals and the return currents from which they obtain chemical signals and metabolic energy. Lobsters are examples of hard-shelled animals that store urine and feces, allowing them to be chemically "quiet" when necessary. 

Together, the two lobster-generated currents that can be measured around the animal s anterior end are complex and carefully controlled. They are ideally suited to carry urine, urine pheromones, and gill metabolites away from the lobster to specified directions. Simultaneously, the water displaced by these outgoing currents results in incoming currents with chemical signals from the environment that can be sampled by the antennular chemoreceptors. 

One may wonder why lobsters appear to use urine as a dispersal solvent for chemical signals, whereas terrestrial arthropods such as the well-studied insects use direct release of gland products into the air. Perhaps the answer is that small animals in air (such as insects) are always in danger of desiccation. By contrast, marine lobsters and crabs are relatively large and may experience only minor water loss problems due to osmosis. Thus, it may not be difficult for a 500-g lobster to store 10 ml of urine and release it during a dominance battle at a rate of up to 1 ml/min (27). The advantage of urine-carried pheromones is that the dispersal mechanism already exists urine is injected into the gill current, which in turn injects into ocean currents. 

More recent studies of crayfish chemical communication suggest that similar to lobsters and crabs (Atema and Steinbach 2007) many chemical signals are contained within the urine. Urine is released anteriorly through a pair of nephro-pores (Fig. 13.1). The anterior position is advantageous as it facilitates the frontal dispersal of pheromones towards conspecifics (see Fig. 13.2). As in other crustaceans the nephropores are opened and closed by a sphincter muscle (Bushmann and... 

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