Cellular adaptations leading to coral fragment attachment on artificial substrates in Acropora millepora (Am-CAM)

Abstract

Reproductive propagation by asexual fragmentation in the reef-building coral Acropora millepora depends on (1) successful attachment to the reef substrate through modification of soft tissues and (2) a permanent bond with skeletal encrustation. Despite decades of research examining asexual propagation in corals, the initial response, cellular reorganisation, and development leading to fragment substrate attachment via a newly formed skeleton has not been documented in its entirety. Here, we establish the first "coral attachment model" for this species ("Am-CAM") by developing novel methods that allow correlation of fluorescence and electron microscopy image data with in vivo microscopic time-lapse imagery. This multi-scale imaging approach identified three distinct phases involved in asexual propagation: (1) the contact response of the coral fragment when contact with the substrate, followed by (2) fragment stabilisation through anchoring by the soft tissue, and (3) formation of a "lappet-like appendage" structure leading to substrate bonding of the tissue for encrustation through the onset of skeletal calcification. In developing Am-CAM, we provide new biological insights that can enable reef researchers, managers and coral restoration practitioners to begin evaluating attachment effectiveness, which is needed to optimise species-substrate compatibility and achieve effective outplanting.

Photo-physiological responses and thermal tolerance of regionally endemic/rare and morphologically different corals of the Western Indian Ocean

“…observation), the sampling site for G. fascicularis. For example, certain corals are now capable of withstanding elevated temperatures (>2°C) provided that they have enhanced resilience through dynamic host-symbiont communities (Ziegler et al 2018) by reshuffling of Symbiodiniaceae (Bhagooli and Hidaka 2003;Fitt et al 2009;Guest et al 2012) heterotrophy (Grotolli et al 2006, shade from algal assemblages giving rise to photo acclimatization most potentially in the case of S. hystrix (Lewis et al 2022) which are essential adaptive criteria for local thermal resistance and acclimatization.…”