Meeting Abstract
The typical benthic marine organism releases its propagules for a minutes- to months-long dispersal stage before they settle again onto the seafloor. In those animals with a relatively lengthy dispersal period (weeks or more), the primary dispersing form is a feeding larva whose time in the plankton can be divided into three phases:
1) immature larva, physically incapable of transforming to the juvenile stage;
2) pre-competent larva, mature but non-responsive to settlement inducers; and
3) competent larva, that will settle when exposed to local settlement inducers, such as a bacterial biofilm or seawater containing cue from conspecifics.
An additional level of complexity can arise during the competent phase. Some larvae follow a ‘death before dishonor’ strategy: such larvae will never settle unless they receive a high quality indicator of suitable juvenile habitat. At the other extreme is so called ‘desperate larvae’, that will accept increasingly inferior settlement conditions as the competence phase proceeds. In previous work, we showed that brief exposure of pre-competent sea urchin and sand dollar larvae to intense fluid turbulence characteristic of waves breaking on the shoreline causes them to become competent to settle. Here we show that such turbulence exposure in competent larvae modulates their level of larval ‘desperation.’ Specifically, competent Pacific sand dollar larvae (Dendraster excentricus) settle more rapidly and into lower quality substrates if they have first been exposed to fluid turbulence. We observed a similar response in the Daisy brittle star, Ophiopholis aculeata. These results add to our growing understanding of how larvae use environmental information to modulate key life history decisions.
