Dynamic simulations of feeding and respiration of the early Cambrian periderm-bearing cnidarian polyps

Abstract

Although fossil evidence has been suggested the existence of the early muscular system in the ancient cnidarian jellyfish from the early Cambrian Kuanchuanpu biota (ca. 535 Ma), south China, the mechanism of feeding and respiration of the early jellyfish is conjecture. Recently, the polyp inside the periderm of olivooids was proven to be the calyx-like, most likely bearing short tentacles and bundles of coronal muscles at the edge of the calyx, thus presumably contributing to feeding and respiration. We simulate here the contraction and expansion of the microscopic periderm-bearing olivooid Quadrapyrgites via the dynamic, fluid–solid interactions (FSI) method to investigate their feeding and respiratory activities. The hydrostatic simulations show that the rate of water inhalation by the polyp subumbrella is positively correlated with the rate of contraction and expansion of the coronal muscles, consisting with the previous feeding and respiration hypothesis. The dynamic simulations also show that the frequent inhalation/exhalation of water through the periderm polyp expansion/contraction conducted by the muscular system of Quadrapyrgites, most likely represents the ancestral feeding and respiration patterns of Cambrian sedentary medusozoans that predated the rhythmic jet-propelled swimming of the modern jellyfish. It will be a remarkable step to apply the dynamic fluid simulation to other early Cambrian cnidarians and metazoans to enlighten their behaviours during the Cambrian explosion.