Rapid Hydrogen Peroxide release from the coral Stylophora pistillata during feeding and in response to chemical and physical stimuli.

Rachel Armoza-Zvuloni,Daniel Sher,Yeala Shaked,Avi Schneider

doi:10.1038/srep21000

Abstract

Corals make use of different chemical compounds during interactions with prey, predators and aggressors. Hydrogen Peroxide (H2O2) is produced and released by a wide range of organisms as part of their defense against grazers or pathogens. In coral reefs, the large fluxes and relatively long half-life of H2O2, make it a potentially important info-chemical or defense molecule. Here we describe a previously unstudied phenomenon of rapid H2O2 release from the reef-building coral Stylophora pistillata during feeding on zooplankton and in response to chemical and physical stimuli. Following stimuli, both symbiotic and bleached corals were found to rapidly release H2O2 to the surrounding water for a short period of time (few minutes). The H2O2 release was restricted to the site of stimulus, and an increase in physical stress and chemical stimuli concentration resulted in elevated H2O2 release. Omission of calcium (a key regulator of exocytotic processes) from the experimental medium inhibited H2O2 release. Hence we suggest that H2O2 is actively released in response to stimuli, rather than leaking passively from the coral tissue. We estimate that at the site of stimulus H2O2 can reach concentrations potentially high enough to deter predators or motile, potentially pathogenic, bacteria.

Highlights

Other oxidants, known as an oxidative burst, is used by microorganisms, plants and mammalian immune cells as a defense against pathogenic bacteria and fungi[11,14]
We probed for H2O2 release during feeding by adding Artemia salina nauplii to the water surrounding S. pistillata coral fragments suspended in 100 mL glass beakers
When conducting the same experiment in a calcium free artificial seawater we found that H2O2 did not increase significantly following all treatments (p > 0.05, one way Repeated Measures ANOVA) and that the number of discharged cnidocytes increased only slightly in response to Fetal Bovine Serum (FBS) (Fig. 3b, note the different scale of the y-axis; Fig. S4)

Summary

Introduction

Other oxidants, known as an oxidative burst, is used by microorganisms, plants and mammalian immune cells as a defense against pathogenic bacteria and fungi[11,14]. H2O2 and other active oxygen molecules, commonly termed reactive oxygen species (ROS), have been studied in the context of the symbiosis between the coral host and its resident algae – the zooxanthellae[15]. We identified and characterized a flow-induced long term release of H2O2 and superoxide (O2−) from the coral Stylophora pistillata[20,21,22], occurring on a time-scale of hours. We explore another yet unstudied phenomenon, namely short term H2O2 release from S. pistillata which occurs on time-scales of minutes in response to various stimuli. By applying localized stimuli and frequent sampling we found that the response is limited to the site of stimulus (rather than whole colony response) and that its duration is limited to few minutes

Methods

Results

Conclusion