Dispersal and colonisation processes at deep-sea vents

Organisms living in the hydrothermal environment are subject to great instability on various spatial and temporal scales (Haymon et al., 1993; Hessler et al., 1988; Lalou, 1991). Catastrophic and chaotic extinctions in populations (Tunnicliffe et al., 1990) forces vent animals to disperse continuously and colonise new active sites (Shank et al., 1998; Tunnicliffe et al., 1997). Population genetics demonstrate exchanges between well-separated populations growing on distant vents along ridges (Vrijenhoek, 1997). The distances over which these genetic exchanges maintain contact between populations differ among vent species. This could be partly due to different dispersal and colonisation capabilities, which are therefore central issues in hydrothermal ecology (Mullineaux and France, 1995; Van Dover et al., 2002). Indeed, since many hydrothermal vent organisms are either sessile or highly sedentary as adults, dispersal processes must mainly be ensured by larvae. Although knowledge of larval life is essential to an understanding of dispersal and colonisation processes, we currently have only glimpses of the early lifehistory biology of hydrothermal vent endemic organisms (Tyler and Young, 1999). Collection of early life stages from deep waters has presented considerable challenges. Larvae of probable vent origin have been collected in plankton tows (Berg and Van Dover, 1987; Kim et al., 1994; Mullineaux et al., 1995), pumps (Kim and Mullineaux, 1998) and sediment traps (Khripounoff The Journal of Experimental Biology 208, 1551-1561 Published by The Company of Biologists 2005 doi:10.1242/jeb.01567