Reduced survival associated with precopulatory mate guarding in male Asellus aquaticus (Isopoda)

Precopulatory mate-guarding in aquatic crustaceans is known to have immediate costs for the guarding male. The extent to which guarding behavior may reduce future reproductive opportunities, however, is less established. We examined the survival and antennae length, suggested to be important in detecting receptive females, in male freshwater isopods (Asellus aquaticus) collected paired or unpaired. Antennae length to body size relationships suggested that large, paired males had broken antennae more commonly than large, unpaired males. Moreover, broken antennae seem to be associated with increased mortality. Males collected paired had lower survival than males collected unpaired, and this reduction in survival was greatest in larger individuals. In pairing trials, males usually attempted pair formation regardless of their size, female size, or previous pairing status. Our results suggest that some costs associated with male guarding behavior may extend beyond the actual guarding episode, though the consequences for mating decisions remain to be determined.