Larval dispersal potential of the tubeworm Riftia pachyptila at deep-sea hydrothermal vents

Abstract

Hydrothermal vents are ephemeral because of frequent volcanic and tectonic activities associated with crust formation. Although the larvae of hydrothermal vent fauna can rapidly colonize new vent sites separated by tens to hundreds of kilometres, the mechanisms by which these larvae disperse and recruit are not understood. Here we integrate physiological, developmental and hydrodynamic data to estimate the dispersal potential of larvae of the giant tubeworm Riftia pachyptila. At in situ temperatures and pressures (2 degrees C and 250 atm), we estimate that the metabolic lifespan for a larva of R. pachyptila averages 38 days. In the measured flow regime at a fast-spreading ridge axis (9 degrees 50' N; East Pacific Rise), this lifespan results in potential along-ridge dispersal distances that rarely exceed 100 km. This limited dispersal results not from the physiological performance of the embryos and larvae, but instead from transport limitations imposed by periodic reversals in along-ridge flows and sustained episodes of across-ridge flow. The lifespan presented for these larvae can now be used to predict dispersal under current regimes at other hydrothermal vent sites.

Larval dispersion along an axially symmetric mid-ocean ridge

“…Along-axis distribution of particles released every 12 minutes from May to October 1999 at 175mab at the ridge crest. These are the same results as presented in the 175mab panel of the top row of Figure 7, plotted as a function of along-axis distance so as to be comparable with Figure 4c of Marsh et al (2001 …”

“…Our results are different from an earlier study (Marsh et al, 2001) day life span, the along-axis distribution of surviving larvae peaked at the along-axis location of their release (x=0 in their Figure 4c). More than 80% of the surviving larvae were located within ±60km of the release site, and the distribution was skewed to the south.…”

“…Moreover, analysis of current meter data along the ridge at 9° 10' N, 9° 30' N, and 9° 50' N suggests coherence of velocity in the along-ridge direction (Thurnherr et al, in preparation). Although the present model is far from complete, we view these simulations as a first step toward implementation of spatially-explicit coupled physical-biological models of larval transport in this complex regime, expanding upon earlier models of larval transport that assumed spatially homogeneous currents (Marsh et al, 2001). 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 Circulation over an idealized 2-d ridge was based on a primitive-equation, baroclinic, hydrostatic, f-plane (latitude = 9.833°N) model described in Lavelle (2006).…”

“…However, physiological studies of Antarctic asteroids have shown that non-feeding larvae may remain viable in the planktonic stage for months, due to lowered metabolism in cold water (Hoegh-Guldberg et al, 1991). The vent tubeworm Riftia pachyptila has been cultured to obtain direct estimates of life span (Marsh et al, 2001); the larvae can live on the order of 30-40 days without feeding. If the larvae are transported as passive neutrally-buoyant particles, they have the potential to disperse distances (Mullineaux et al, 2002).…”

Free-Living Tube Worm Endosymbionts Found at Deep-Sea Vents

“…The presence of free-living symbiotic bacteria at multiple spatial scales within a vent site suggests a potentially large environmental pool of symbionts. During host larval development and the colonization of new vents (17,20,21), an abundant free-living bacterial population would facilitate the initiation of the symbiosis. The environmental transmission of symbionts seems to be a risky strategy for obligate tube worm symbioses, as the survival of the mouthless and gutless adult host requires that developing larvae or juveniles successfully acquire their symbionts from a potentially unstable free-living source population.…”