MATERNAL-CARE IN THE BROMELIAD CRAB, METOPAULIAS-DEPRESSUS - PROTECTION OF LARVAE FROM PREDATION BY DAMSELFLY NYMPHS

Metopaulias depressus (Decapoda, Grapsidae) is a crab that breeds in water-storing leaf axils of large Jamaican bromeliads. This study examined whether and how maternal care protects crab larvae from predation by damselfly nymphs. The nymph of the bromeliad-breeding damselfly, Diceratobasis macrogaster, is the major predator on bromeliad crab larvae. Laboratory tests revealed that a nymph kills on average five larvae per day. Both the damselfly and the bromeliad crabs prefer the bromeliad Aechmea paniculigera as a breeding site. Nymphs were abundant: 87% of the A. paniculigera held 1-16 nymphs. Bromeliad crabs release on average 50 larvae into a prepared nursery axil where they develop for 9-10 days into young crabs. In field experiments maternal care reduced larval mortality from predation by 60%. A calculation based on predator abundance and killing potential suggests that female brood desertion would lead to 54-100% loss of their reproductive investment, depending on the female's body size and age (egg number is positively correlated with body size). Protected broods showed on average only 22% mortality during the larval period. In the bromeliad crab, predation on larvae exerts strong selection on the maintenance of maternal care for larvae. © 1992 The Association for the Study of Animal Behaviour.