Biology subjects

Baker, D. M.

Publications and source records attributed to Baker, D. M..

3 recordsLinked to original sources

bioRxiv2022

Symbiosis-driven development in an early branching metazoan

Microbes can initiate developmental gene regulatory cascades in animals. The molecular mechanisms underlying microbe-induced animal development and the evolutionary steps to integrate microbial signals into regulatory programs remain poorly understood. In the upside-down jellyfish Cassiopea xamachana, a dinoflagellate endosymbiont initiates the life stage transition from the sessile polyp to the sexual medusa. We found that metabolic products derived from symbiont carotenoids may be important to initiate C. xamachana development, in addition to expression of conserved genes involved in medusa development of non-symbiotic jellyfish. We also revealed the transcription factor COUP is expressed during metamorphosis, potentially as a co-regulator of nuclear receptor RXR. These data suggest relatively few steps may be necessary to integrate symbiont signals into gene regulatory networks and cements the role of the symbiont as a key trigger for life history transition in C. xamachana.

developmental biology↗

bioRxiv2022

The reef-building coral Galaxea fascicularis: a new model system for coral symbiosis

Reef-building corals owe their evolutionary success to their symbiosis with unicellular algae (Symbiodiniaceae). However, increasingly frequent heat waves lead to coral mass-bleaching events and pose a serious threat to the survival of reef ecosystems. Despite significant efforts, a mechanistic understanding of coral-algal symbiosis functioning, what leads to its breakdown and what can prevent it, remains incomplete. The main obstacles are low amenability of corals to experimental handling and, owing to its obligatory nature, the difficulties of manipulating the coral-algal association. Indeed, many studies on the symbiotic partnership are conducted on other cnidarian model organisms and their results may therefore not be fully transferable to tropical reef-building corals. Here, we identify the tropical stony coral species Galaxea fascicularis as a novel candidate coral model system. Individual polyps of this species can be separated, enabling highly replicated genotype studies, and are well suited to experimental investigation of the symbiosis as they can be easily and effectively rid of their algal symbionts (bleached). We show that bleached adult individuals can reestablish symbiosis with non-native symbionts, and we report the completion of the gametogenic cycle ex-situ, with the successful spawning in aquaria over multiple years. These achievements help overcome several of the major limitations to direct research on corals and highlight the potential of G. fascicularis as an important new model system for investigations of symbiosis functioning and manipulation.

systems biology↗

bioRxiv2021

The benefits of herbivory outweigh the costs of bioerosion in a eutrophic coral community

Herbivores play an integral part in maintaining the health of coral reefs by suppressing the growth of algae and accumulation of sediment and facilitating coral growth. However, in predator-depleted systems where densities of herbivores are unnaturally high, grazing can have detrimental effects on corals through excessive bioerosion. Yet, these benefits and costs are rarely investigated concurrently, especially in eutrophic systems where grazers may play a disproportionate role. We used a year-long exclusion experiment to elucidate the effect of natural densities of the dominant herbivore (the sea urchin Diadema setosum) on coral communities in a heavily fished and eutrophic system (Hong Kong, China). To assess benthic community response to grazing, we monitored the survival and growth of three locally abundant coral species (Pavona decussata, Platygyra carnosus and Porites sp.), algal and sediment accumulation, and bioerosion of coral skeletons across seasons. We found that urchins maintained our experimental coral assemblages, and when excluded, there was a 25 to 75-fold increase in algal-sediment matrix accumulation. Contrary to predictions, there was no general response of corals to urchin presence; Porites sp. survivorship increased while P. decussata was unaffected, and growth rates of both species was unchanged. Surprisingly, P. carnosus experienced higher mortality and bioerosion of up to 33% of their buoyant weight when urchins were present. Therefore, under natural densities, sea urchins clear substrate of algae and sediment, increase survival, maintain growth rates and health of coral assemblages, yet can accelerate the bioerosion of species with porous skeletons following mortality.

ecology↗