Cambrian cinctan echinoderms shed light on feeding in the ancestral deuterostome.
Reconstructing the feeding mode of the latest common ancestor of deuterostomes is key to elucidating the early evolution of feeding in chordates and allied phyla; however, it is debated whether the ancestral deuterostome was a tentaculate feeder or a pharyngeal filter feeder. To address this, we evaluated the hydrodynamics of feeding in a group of fossil stem-group echinoderms (cinctans) using computational fluid dynamics. We simulated water flow past three-dimensional digital models of a Cambrian fossil cinctan in a range of possible life positions, adopting both passive tentacular feeding and active pharyngeal filter feeding. The results demonstrate that an orientation with the mouth facing downstream of the current was optimal for drag and lift reduction. Moreover, they show that there was almost no flow to the mouth and associated marginal groove under simulations of passive feeding, whereas considerable flow towards the animal was observed for active feeding, which would have enhanced the transport of suspended particles to the mouth. This strongly suggests that cinctans were active pharyngeal filter feeders, like modern enteropneust hemichordates and urochordates, indicating that the ancestral deuterostome employed a similar feeding strategy.
School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK imran.rahman@bristol.ac.uk.
Imran A
IA
Rahman
Instituto Geológico y Minero de España, C/Manuel Lasala, 44 - 9° B, Zaragoza 50006, Spain.
Samuel
S
Zamora
School of Natural Sciences and Psychology, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK.
Peter L
PL
Falkingham
School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK.
Jeremy C
JC
Phillips
D000818:Animals; D005075:Biological Evolution; D003198:Computer Simulation; D004447:Echinodermata / Q000502:physiology*; D005247:Feeding Behavior; D005580:Fossils; D057446:Hydrodynamics
computational fluid dynamics; deuterostomes; echinoderms; evolution; feeding; functional morphology