Dynowski JF et al. (2016), Computational Fluid Dynamics Analysis of the Fo...

ECB-ART-48272

PLoS One 2016 May 04;115:e0156408. doi: 10.1371/journal.pone.0156408.

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Computational Fluid Dynamics Analysis of the Fossil Crinoid Encrinus liliiformis (Echinodermata: Crinoidea).

Dynowski JF , Nebelsick JH , Klein A , Roth-Nebelsick A .

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Crinoids, members of the phylum Echinodermata, are passive suspension feeders and catch plankton without producing an active feeding current. Today, the stalked forms are known only from deep water habitats, where flow conditions are rather constant and feeding velocities relatively low. For feeding, they form a characteristic parabolic filtration fan with their arms recurved backwards into the current. The fossil record, in contrast, provides a large number of stalked crinoids that lived in shallow water settings, with more rapidly changing flow velocities and directions compared to the deep sea habitat of extant crinoids. In addition, some of the fossil representatives were possibly not as flexible as today''s crinoids and for those forms alternative feeding positions were assumed. One of these fossil crinoids is Encrinus liliiformis, which lived during the middle Triassic Muschelkalk in Central Europe. The presented project investigates different feeding postures using Computational Fluid Dynamics to analyze flow patterns forming around the crown of E. liliiformis, including experimental validation by Particle Image Velocimetry. The study comprises the analysis of different flow directions, velocities, as well as crown orientations. Results show that inflow from lateral and oral leads to direct transport of plankton particles into the crown and onto the oral surface. With current coming from the "rear" (aboral) side of the crinoid, the conical opening of the crown produces a backward oriented flow in its wake that transports particles into the crown. The results suggest that a conical feeding position may have been less dependent on stable flow conditions compared to the parabolic filtration fan. It is thus assumed that the conical feeding posture of E. liliiformis was suitable for feeding under dynamically changing flow conditions typical for the shallow marine setting of the Upper Muschelkalk.

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Genes referenced: LOC100887844 LOC115925415

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	Fig 1. Encrinus liliiformis.(A) Fossil crown from Crailsheim, Germany, showing typical preservation with arms opened to a slight extent (deposited in the collection of the State Museum of Natural History Stuttgart, specimen number SMNS21859). (B) Schematic illustration of morphological features.
	Fig 2. Palaeogeography of the Central European Basin during the upper Muschelkalk (Middle Triassic).Grey colour: terrestrial settings, white colour: marine settings, outline displays state of Baden-Württemberg with S: Stuttgart, Germany. Modified following [38, 43].
	Fig 3. Analyzed 3D models of E. liliiformis.(A) Base model. (B) Pinnules spread. (C) Arms opened. (D) Parts of 3 arms capped.
	Fig 4. CFD setup.(A) Overview of computational mesh of the base model. (B) Detail of (A) illustrating inflation layers on the model surface. (C) Computational domain with inflow from aboral. (D) Computational domain with inflow from oral. (E) Computational domain with inflow from lateral.
	Fig 5. Models used for validation of CFD simulations.(A) Handmade resin-wire model. (B) computer-generated 3D model. Scale bars 20 mm.
	Fig 6. Summarized results of PIV experiments and CFD simulations.(A) Combined contour-vector plot illustrating PIV results at Vinit = 0.14 m/s. (B) Combined contour-vector plot illustrating CFD results at Vinit = 0.14 m/s. (C) Velocity component V and U of PIV experiments for all three inflow velocities, measured along a line parallel to the z-axis (location indicated by dotted line in (A)). (D) Velocity component V and U of CFD simulations for all three inflow velocities, measured along a line parallel to the z-axis (location indicated by dotted line in (B)).
	Fig 7. Flow results for the base model and aboral inflow at Vinit = 0.14 m/s.(A) Overview illustrating model orientation and individual velocity components. (B) Combined contour-vector plot illustrating recirculation on ZX plane in oblique view. (C) Combined contour-vector plot illustrating recirculation on XY plane in oblique view. (D) Combined contour-vector plot illustrating recirculation on ZX plane in top view. (E) Linegraph plot of velocity component u directly behind the end of the arms (location indicated by dotted line in (D)). Negative u values indicate recirculation zone.
	Fig 8. Results of the four different models for aboral inflow at Vinit = 0.14 m/s.(A) Linegraph plots of total velocity parallel to the x-axis, starting at the inner surface of the calyx (location indicated by dotted line in Fig 7D). (B) Linegraph plots of velocity component u parallel to the x-axis, starting at the inner surface of the calyx (location indicated by dotted line in Fig 7D). (C) Isosurface plots of negative u values for the base model. (D) Isosurface plots of negative u values for the model with arms opened.
	Fig 9. Pressure distribution on the base model at Vinit = 0.14 m/s.(A) Contour plot of pstat on the aboral surface of the base model. (B) Contour plot of pstat in top view. (C) Linegraph plot of pstat plotted against x, following the outline of the crinoid model (location indicated in (B)).
	Fig 10. Results of particle tracking simulations for aboral inflow at Vinit = 0.14 m/s.(A) Pathline plot illustrating recirculation of plankton particles (diameter = 150 μm) into the filter apparatus for the base model. (B) Pathline plot illustrating recirculation of plankton particles (diameter = 150 μm) into the filter apparatus for the model with 3 arms capped. (C) Histogram showing number of recirculating particles with different diameters for all four models.
	Fig 11. Flow results for the base model and oral inflow at Vinit = 0.14 m/s.(A) Combined contour-vector plot illustrating flow pattern on XY plane in side view. (B) Combined contour-vector plot illustrating flow pattern on ZX plane in top view. (C) Contourline plot showing velocity distribution on XY plane in side view.
	Fig 12. Results of particle tracking simulations and pressure distribution for oral inflow at Vinit = 0.14 m/s.(A) Pathline plot illustrating straight flow of plankton particles (diameter = 150 μm) through the filter apparatus for the base model. (B) Pathline plot illustrating straight flow of plankton particles (diameter = 150 μm) through the filter apparatus for the model with arms opened. (C) Contour plot illustrating pressure distribution on the oral surface of the base model. (D) Contour plot illustrating pressure distribution on the oral surface of the model with 3 arms capped.
	Fig 13. Results for the base model for lateral inflow.(A) Combined contour-vector plot illustrating flow pattern on XY plane in side view at Vinit = 0.14 m/s. (B) Combined contour-vector plot illustrating flow pattern on ZX plane in top view at Vinit = 0.14 m/s. (C) Pathline plot illustrating straight flow of plankton particles (diameter = 150 μm) through the filter apparatus in side view at Vinit = 0.14 m/s. (D) Pathline plot illustrating straight flow of plankton particles (diameter = 150 μm) through the filter apparatus in top view at Vinit = 0.14 m/s. (E) Pathline of one particle (diameter = 150 μm) that passes the filtering structures 2 times at Vinit = 0.14 m/s in front view. (F) Pathline of the same particle shown in (E)) at Vinit = 0.03 m/s in front view.

References [+] :

Birenheide, Contractile connective tissue in crinoids. 1996, Pubmed, Echinobase