Alejandro Martínez, 27 year-old Spanish evolutionary biologist, works at the Marine Biological Section of the University of Copenhagen at Helsingør (Denmark). He is a PhD student of Dr. Katrine Worsaae. Both researchers have been doing impressive research on the annelid diversity of marine caves.
Specifically, Alejandro and his colleagues are interested in a special type of marine caves called anchialine caves. Since they are isolated from the open sea, those caves can be colonised by new organisms that may then adapt to the new ecological conditions. These adaptations can involve remarkable changes in morphology.
The main site of study is the island of Lanzarote (Spain), where Alejandro and his team are supported by the local administration, including the Lanzarote's Biosphere Reserve. The team has explored as well marine caves from other islands such as Sardinia, Majorca, and the Azores. The project also involves main scientists at an international level, such as Prof. Gonzalo Giribet (Harvard University), Prof. Thomas Iliffe (TAMUG), Dr. Maikon Di Domenico (Federal University of Paraná), and Prof. Greg Rouse (SCRIPPS).
August 30th 2012, 12:00 h, Ed. de Servicios Centrales de Investigación, Campus de Elviña s/n, A Coruña.
«Sous les pavés, la plage»: Evolutionary tales on interstitial annelids, cave annelids… and interstitial cave annelids.
Alejandro Martínez, Katrine Worsaae.
A unique animal assemblage inhabits the extreme environment among the sand grains in the sea: the interstitial fauna. Tight spaces, oxygen and light limitations, capillary forces affecting the water flow and, in many instances, the relentless agitation of waves or currents, are characteristic of this environment, suitable only for highly specialised forms. Annelids are among the several groups that flourish in this environment, including some entirely interstitial families, such as Protodrilidae or Nerillidae. Protodrilids are small noodle-like worms, with paired short cephalic 'tentacles'; whereas nerillids resemble tiny teddy bears, with reduced number of segments and very characteristic club-shaped palps. All species in those lineages are simple, possibly, due to a secondary loss of structures. Although very extreme as well, the environmental conditions in marine caves differ a lot from those among the sand grains. The big spaces among rocks favour the water flow and water currents carry suspended particles and organic matter. Annelids are rare in that habitat, dominated instead by crustaceans such as remipedes, thermosbaenacans and certain amphipods, ostracods or copepods. Due to those very different conditions especially regarding water flow, an interstitial animal, as a protodrilid or a nerillid, would have small chances to survive in those environments…. But, surprisingly, they are there! Some of them survive in located spots inside caves where sediments accumulate, like in small subterranean 'beaches'… but others, swim in the water column, side by side to the most specialised cave animals, feeding on suspended organic matter. Which morphological changes make possible this ecological shift? Are those animals isolated in the caves, or do they interact with the outside world? Do they belong to ancient lineages dragged into caves by cataclysmic events that killed their marine relatives, or rather represent fool highly derived lineages, that started diving into the subterranean adventure only during recent times? What can we learn from studying those small creatures about the origin and evolution of other Metazoa?