Symbiophagy as a cellular mechanism for coral bleaching

Downs, Craig A.; Kramarsky‐Winter, Esti; Martinez, Jon; Kushmaro, Ariel; Woodley, Cheryl M.; Loya, Yossi; Ostrander, Gary K.

doi:10.4161/auto.5.2.7405

Cited by 112 publications

(141 citation statements)

References 21 publications

(31 reference statements)

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“…In contrast, under the thermal stress conditions, large numbers of the normal form Symbio dinium were expelled from the corals, and the phenomenon apparently results in coral discoloration. Under these circumstances, few degraded Symbiodinium were expelled in contrast to the report by Downs et al (2009) in which the digestion of Symbiodinium in the coral tissue was promoted by heat stress. In another study, degraded Symbio dinium accumulated in coral tissues in naturally bleached corals (Brown et al 1995).…”

Section: Discussioncontrasting

confidence: 46%

Expulsion of zooxanthellae (Symbiodinium) from several species of scleractinian corals: comparison under non-stress conditions and thermal stress conditions

Fujise

Yamashita

Suzuki

et al. 2013

Galaxea, Journal of Coral Reef Studies

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Corals expel zooxanthellae (Symbiodinium) not only under thermal stress conditions, but also under nonstress conditions. To better understand the significance of this, we compared cell numbers, morphologies and photosynthetic activities of the expelled Symbiodinium under different temperatures for six species of scleractinian corals; Acropora selago, Acropora muricata, Heliofungia actiniformis, Ctenactis echinata, Oxypora lacera and Pocil lopora eydouxi, kept in aquariua. During the eight day aquarium experiment, every coral expelled two types of Symbiodinium morphologies, normal and degraded form, and the ratios of these forms differed depending on the temperature. Under a non-stress, initial temperature condition of 27℃, mainly degraded cells were expelled. In contrast, when the water temperature was increased and reached to 32℃, the expulsion rates drastically increased,

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Section: Discussioncontrasting

confidence: 46%

Expulsion of zooxanthellae (Symbiodinium) from several species of scleractinian corals: comparison under non-stress conditions and thermal stress conditions

Fujise

Yamashita

Suzuki

et al. 2013

Galaxea, Journal of Coral Reef Studies

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“…Reduced biomass of bleached colonies compared with non-bleached colonies (50% less tissue per surface area; data not shown) may indicate that the colonies catabolize their tissue in order to maintain metabolic activities such as gametogenesis (Szmant & Gassman 1990, Mendes & Woodley 2002. Indeed, Downs et al (2009) showed that corals digest their zooxanthellae via the autophagic pathway, a pathway known to recycle cellular components during periods of high irradiance and temperature.…”

Section: Suggestions For Alternative Energy Resourcesmentioning

confidence: 99%

Repeated bleaching events may result in high tolerance and notable gametogenesis in stony corals: Oculina patagonica as a model

Armoza-Zvuloni¹,

Segal²,

Kramarsky‐Winter³

et al. 2011

Mar. Ecol. Prog. Ser.

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Coral bleaching events (BEs) are occurring in coral reefs worldwide and are expected to become annual, triggered by seasonal changes in water temperature. The stony coral Oculina patagonica experiences repeated seasonal BEs along the Israeli Mediterranean coast. It thus constitutes a good model for assessing the potential effects of expected repeated BEs on coral physiology. Previous studies have shown that the overlap between bleaching and reproduction seasons in O. patagonica impedes gametogenesis. In the present study, we assessed the effect of bleaching on gametogenesis of populations commonly undergoing repeated seasonal BEs, and compared it with the effect of first and second summer BEs on gametogenesis of a population that has not experienced a summer BE in recent years. Interestingly, we found no differences between bleached and non-bleached colonies in most of the reproductive parameters tested in populations undergoing repeated seasonal BEs. We did find, however, that a population that experienced a summer BE for the first time presented significantly lower reproductive parameters in bleached colonies when compared to non-bleached colonies. Furthermore, in the following year, such bleached colonies showed an improvement in reproductive performance when compared to the previous year. The remarkable differences in gametogenesis between colonies experiencing first summer BE and those experiencing repeated seasonal BEs may be the result of improved utilization of alternative energy sources. This study provides the first evidence for notable gametogenesis in corals undergoing repeated bleaching, and suggests that adjustment processes may increase tolerance levels and may play a role in the ability of corals to overcome the expected repeated BEs.

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“…It has been hypothesized that, during a stress event, the mechanism maintaining symbiosis is destabilized and symbiophagy is activated, ultimately resulting in the phenomenon of bleaching. This work was focused on the Symbiodinium cell as the initiator of the bleaching cascade (Downs et al 2009).…”

Section: Autophagy Induced By Environmental Stress On Aquatic Invertementioning

confidence: 99%

Autophagy as a defense strategy against stress: focus on Paracentrotus lividus sea urchin embryos exposed to cadmium

Chiarelli

Martino

Agnello

et al. 2016

Cell Stress and Chaperones

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Autophagy is used by organisms as a defense strategy to face environmental stress. This mechanism has been described as one of the most important intracellular pathways responsible for the degradation and recycling of proteins and organelles. It can act as a cell survival mechanism if the cellular damage is not too extensive or as a cell death mechanism if the damage/stress is irreversible; in the latter case, it can operate as an independent pathway or together with the apoptotic one. In this review, we discuss the autophagic process activated in several aquatic organisms exposed to different types of environmental stressors, focusing on the sea urchin embryo, a suitable system recently included into the guidelines for the use and interpretation of assays to monitor autophagy. After cadmium (Cd) exposure, a heavy metal recognized as an environmental toxicant, the sea urchin embryo is able to adopt different defense mechanisms, in a hierarchical way. Among these, autophagy is one of the main responses activated to preserve the developmental program. Finally, we discuss the interplay between autophagy and apoptosis in the sea urchin embryo, a temporal and functional choice that depends on the intensity of stress conditions.

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Symbiophagy as a cellular mechanism for coral bleaching

Cited by 112 publications

References 21 publications

Expulsion of zooxanthellae (Symbiodinium) from several species of scleractinian corals: comparison under non-stress conditions and thermal stress conditions

Expulsion of zooxanthellae (Symbiodinium) from several species of scleractinian corals: comparison under non-stress conditions and thermal stress conditions

Repeated bleaching events may result in high tolerance and notable gametogenesis in stony corals: Oculina patagonica as a model

Autophagy as a defense strategy against stress: focus on Paracentrotus lividus sea urchin embryos exposed to cadmium

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