Kregting LT et al. (2013), Effects of oscillatory flow on fertilization in...

ECB-ART-43066

PLoS One 2013 Jan 01;89:e76082. doi: 10.1371/journal.pone.0076082.

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Effects of oscillatory flow on fertilization in the green sea urchin Strongylocentrotus droebachiensis.

Kregting LT , Bass AL , Guadayol Ò , Yund PO , Thomas FI .

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Broadcast spawning invertebrates that live in shallow, high-energy coastal habitats are subjected to oscillatory water motion that creates unsteady flow fields above the surface of animals. The frequency of the oscillatory fluctuations is driven by the wave period, which will influence the stability of local flow structures and may affect fertilization processes. Using an oscillatory water tunnel, we quantified the percentage of eggs fertilized on or near spawning green sea urchins, Strongylocentrotus droebachiensis. Eggs were sampled in the water column, wake eddy, substratum and aboral surface under a range of different periods (T = 4.5-12.7 s) and velocities of oscillatory flow. The root-mean-square wave velocity (rms(u(w))) was a good predictor of fertilization in oscillatory flow, although the root-mean-square of total velocity (rms(u)), which incorporates all the components of flow (current, wave and turbulence), also provided significant predictions. The percentage of eggs fertilized varied between 50-85% at low flows (rms(u(w)) <0.02 m s(-1)), depending on the location sampled, but declined to below 10% for most locations at higher rms(u(w)). The water column was an important location for fertilization with a relative contribution greater than that of the aboral surface, especially at medium and high rms(u(w)) categories. We conclude that gametes can be successfully fertilized on or near the parent under a range of oscillatory flow conditions.

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Species referenced: Echinodermata
Genes referenced: adv LOC100887844 LOC100893907 ptfa1

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	Figure 1. Diagram of the oscillatory water tunnel (OWT).The OWT chamber was used to determine the effects of oscillatory flow on fertilization of the green sea urchin Strongylocentrotus droebachiensis. The drive mechanism that attaches to the paddle (via two coupled hydraulic pistons driven by a flywheel attached to an electric motor powered by an adjustable frequency drive) has been omitted from the figure.
	Figure 2. Hydrodynamic characterisation of the oscillatory water tunnel.(A) Sample wave form with underlying current (u, v, and w velocities (m s−1)) from an ADV positioned with the x probe oriented with the dominant current direction and the sample volume 0.04 m above the substrate (corresponding to the average height of the female sea urchins used in the trials). (B) Range of hydrodynamic conditions explored in the experimental trials, with both rms(u w) (m s−1) and period (s) manipulated independently. (C) Test section velocity profiles in the absence of the female sea urchin. Mean longitudinal velocity (ū) normalized by mean longitudinal velocity of the maximum probe height (ū m) from the tank floor (0.18 m) from three velocity profiles representative from each of the rms(u w) categories: LOW [< 0.03 m s−1], MEDIUM [> 0.03<0.06 m s−1], HIGH [> 0.06 m s−1]

	Figure 4. Variation in fertilization as a function of flow.Mean percent fertilization (PF) is plotted as a function of rms(u w) (m s−1) in the four sampling locations: water column, wake eddy, substrate, and aboral surface. Symbols represent weighted mean of all the time points. Lines represent a nonlinear curve fit to the untransformed data. PF was strongly dependent on rms(u w) (m s−1) for all sampling locations (Table 1).
	Figure 5. Importance of location for egg fertilization.Estimate of (A) the percentage of the total number of eggs spawned that were fertilized (PTF) and (B) the relative contribution to overall fertilization (RCO) at the aboral surface and water column as a function of rms(u w) categories: LOW (<0.03 m s−1), MEDIUM (>0.03<0.06 m s−1) and HIGH (>0.06 m s−1).

References [+] :

Babcock, Sperm Diffusion Models and In Situ Confirmation of Long-Distance Fertilization in the Free-Spawning Asteroid Acanthaster planci. 1994, Pubmed, Echinobase