title: Burrowing hard corals occurring on the sea floor since 80 million years ago.
abstract: We describe a previously unknown niche for hard corals in the small, bowl-shaped, solitary scleractinian, Deltocyathoides orientalis (Family Turbinoliidae), on soft-bottom substrates. Observational experiments were used to clarify how the sea floor niche is exploited by turbinoliids. Deltocyathoides orientalis is adapted to an infaunal mode of life and exhibits behaviours associated with automobility that include burrowing into sediments, vertical movement through sediments to escape burial, and recovery of an upright position after being overturned. These behaviours were achieved through repeated expansion and contraction of their peripheral soft tissues, which constitute a unique muscle-membrane system. Histological analysis showed that these muscle arrangements were associated with deeply incised inter-costal spaces characteristic of turbinoliid corals. The oldest known turbinoliid, Bothrophoria ornata, which occurred in the Cretaceous (Campanian), also possessed a small, conical skeleton with highly developed costae. An infaunal mode of life became available to turbinoliids due to the acquisition of automobility through the muscle-membrane system at least 80 million years ago. The newly discovered active burrowing strategies described herein provide new insights into the use of an unattached mode of life by corals inhabiting soft-bottom substrates throughout the Phanerozoic.
authors.affiliation: Seto Marine Biological Laboratory, Field Science Education and Research Center, Kyoto University, 459 Shirahama, Nishimuro, Wakayama 649-2211, Japan.
authors.forename: Asuka
authors.initials: A
authors.lastname: Sentoku
authors.affiliation: Tottori Prefectural Museum, 2-124 Higashimachi, Tottori 680-0011, Japan.|Tottori University of Environmental Studies, 1-1-1 Wakabadaikita, Tottori 689-1111, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tokuda
authors.affiliation: Department of Geosciences, Faculty of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ezaki
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000033:anatomy & histology* / Q000502:physiology*; D019015:Geologic Sediments; D006651:Histocytochemistry; D007564:Japan; D008124:Locomotion; D010140:Pacific Ocean