My scientific investigations have focused on the evolution of reproductive strategies in animals. I carried out field research on marine and terrestrial crustaceans as well as on tropical anurans. The research focused on strategies for maximizing reproductive success, sperm competition and investment in offspring, for example through intensive brood care.
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This inconspicuous fellow, the male ghost crab Inachus phalangium, has a tiny brain, but when it comes to dating with its ladies, it demonstrates an extraordinary memory.
In my study area near Banyuls-sur-Mer (F), the Leach's spider crab lives under the protection of the stinging sea anemone Anemonia viridis. Adult female spider crabs remain in the same place, on the same anemone, for their entire lives and continue to lay eggs until they die. The last copulation partner before spawning is the father of the entire next brood.
A spider crab male can maximise the number of his offspring if he copulates with many females shortly before they spawn.
But these potential reproductive partners live widely scattered in a fragmented, rocky habitat and each has its own spawning season. This is when the large territory holders show what they are made of: They remember the exact location and spawning date of every female in their territory and arrive in time to fertilise the new clutch.
This ability is known in science as episodic memory.
When it comes to radiation and speciation, Jamaica rivals the Galapagos at least for terrestrial crabs, snails and frogs.
Studies of the Jamaican crabs, by me and my students over a 20-year period, show how this came about and where it went.
3-4 Mya ago, the ancestor of the Jamaican crabs became independent of saltwater in the ocean and its descendants invaded new freshwater habitats. They adapted to caves, streams and rivers, the forst underground and the canopy of rainforest trees.
Over 13 endemic species have emerged that have solved the problem of terrestrial reproduction in very different ways.
Jamaica holds the world record for endemic crab species per square kilometer.
The Jamaican bromeliad crab, Metopaulias depressus, has a unique reproductive and social behavior among crustaceans. For crabs, reproduction in a terrestrial habitat presents the greatest challenge. As a relatively recent species in this habitat, the survival of the larvae and young is crucial. The bromeliad crab has developed a set of adaptations for this.
She spends her entire life in bromeliads. There, in the leaf axils, it finds water and food. The brood is cared for by the mother, fed and protected from predators.
Young crabs stay with their mother and siblings for up to 2 years. The bromeliad crab lives in a family clan on its own bromeliad.
The Jamaican "snail crab", Sesarma jarvisi, is another survivor in an inhospitable habitat for crabs and it has evolved an incredible behavior to do so.
Although I found this hidden living species occasionally in my explorations in the rugged limestone hills, it took years before it revealed its nursery to me.
This small crab lives under rock debris in the forest underground. Permanent water is hardly available, but without water, larval and juvenile development is impossible. However, the shells of large Landsnails were handy to her here.
For more than 13 years, myself and my students Martina Schuh, Diethard Horst, Gernot Bäurle, Christoph Schubart and Jens Reimer have been researching various aspects of the evolution of
Jamaican Sesarminae, i.e. what I call Jamaican crabs.
The focus was on the question of when and how the colonisation of land took place, i.e. the independence from a marine planktonic larval development and the colonization of limnic and terrestrial habitats and their radiation and evolutionary adaptation to the many new habitats, especially in reproduction.
The Jamaican cave breeding frog, Eleutherodactylus cundalli, is one of 21 frogs endemic to Jamaica. During the breeding season, it penetrates deep into Limeston caves, where males emitt advertise from small territories, where mating takes place, the females lay a cluch of eggs and take care of the brood until the froglets hatch.
E. cundalli was described by us as the first cave breeding frog worldwide.