Brief exposure to intense turbulence induces a sustained life-history shift in echinoids

Abstract

In coastal ecosystems, attributes of fluid motion can prompt animal larvae to rise or sink in the water column and to select microhabitats within which they attach and commit to a benthic existence. In echinoid (sea urchin and sand dollar) larvae living along waveexposed shorelines, intense turbulence characteristic of surf zones can cause individuals to undergo an abrupt life-history shift characterized by precocious entry into competencethe stage at which larvae will settle and complete metamorphosis in response to local cues. However, the mechanistic details of this turbulencetriggered onset of competence remain poorly defined. Here, we evaluate in a series of laboratory experiments the time course of this turbulence effect, both the rapidity with which it initiates and whether it perdures. We found that larvae become competent with turbulence exposures as brief as 30 s, with longer exposures inducing a greater proportion of larvae to become competent. Intriguingly, larvae can remember such exposures for a protracted period (at least 24 h), a pattern reminiscent of long-term potentiation. Turbulence also induces short-term behavioral responses that last less than 30 min, including cessation of swimming, that facilitate sinking and thus contact of echinoid larvae with the substratum. Together, these results yield a novel perspective on how larvae find their way to suitable adult habitat at the critical settlement transition, and also open new experimental opportunities to elucidate the mechanisms by which planktonic animals respond to fluid motion.

Diversity of cilia-based mechanosensory systems and their functions in marine animal behaviour

“…For example, oyster larvae stop swimming and sink in response to the turbulent layer near the substrate (ca 1 cm from the surface) [278]. In some echinoderm larvae, turbulence may induce competence to settle [273,337,338].…”

Do stranded sand dollars indicate hydrodynamic conditions of sandy beaches?

“…The size of the sand dollars was another favorable factor for their use as an indicator of the hydrological dynamics of Praia de Santos. Figure 4 shows a predominance of adult animals, with higher chances of reproducing before being released to the supra coast and dying [29][30][31][32][33][34] found that water turbulence induces behavioral responses to the transition of Pacific sand dollar larvae (Dendraster excentricus) from the planktonic to the benthic phase. This same phenomenon may not occur with the larvae of Melitta quinquesperforata, seen by the absence of younger individuals (below 4cm) that possibly occupy places distant from the surf zone of Santos beach.…”