Resumen de Movimiento del fluido alrededor de las conchas de los hipurítidos: efectos de la orientación de las conchas en el suministro y concentración de partículas en las corrientes de alimentación
Eulàlia Gili Folch, Michael LaBarbera
We looked at water flow patterns in a flume around models ofhippuritids. Models oriented vertically or inclined upstream showed flow patterns identical to those previously described for cylindrical objects projecting through a boundary layer. Models inclined downstream generate an intense vortex that lifts water off the substrate to bathe the cap (equivalent to the hippuritid left valve). It was hypothesized that a downstream-inclined orientation would have been advantageous in nutrient poor waters because the quantity and variety of available organic particles would have been enhanced. We tested this prediction in a modern marine environment by deploying paired models in subtidal sediments. Model hippuritids were similar to those used in our previous laboratory experiments but equipped with a 1.5 pm filter. Paired models were placed in various orientations and configurations; water was drawn through the pores in the left valve and through the filter of each model. Vertical and upstream-tilted models in unidirectional flow caught similar quantities of organics; downstream-tilted models caught significantly more than both. In oscillating flows, inclined models, either solitary or in aggregations, captured more organics than vertical models.
Models in aggregations caught more organics than solitary models; models on the edge of aggregations captured more than those in the center. We conclude that an inclined orientation permitted hippuritids to exploit resources unavailable to vertically-oriented rudists.
