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Cellular responses in sea fan corals: granular amoebocytes react to pathogen and climate stressors.

Mydlarz LD, Holthouse SF, Peters EC, Harvell CD - PLoS ONE (2008)

Bottom Line: Melanosomes were detected in amoebocytes adjacent to protective melanin bands in infected sea fans; neither was present in uninfected fans.The observed amoebocyte responses indicate that sea fan corals use cellular defenses to combat fungal infection and temperature stress.The ability to mount an inflammatory response may be a contributing factor that allowed the survival of even infected sea fan corals during a stressful climate event.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Texas at Arlington, Arlington, Texas, United States of America. Mydlarz@UTA.edu

ABSTRACT

Background: Climate warming is causing environmental change making both marine and terrestrial organisms, and even humans, more susceptible to emerging diseases. Coral reefs are among the most impacted ecosystems by climate stress, and immunity of corals, the most ancient of metazoans, is poorly known. Although coral mortality due to infectious diseases and temperature-related stress is on the rise, the immune effector mechanisms that contribute to the resistance of corals to such events remain elusive. In the Caribbean sea fan corals (Anthozoa, Alcyonacea: Gorgoniidae), the cell-based immune defenses are granular acidophilic amoebocytes, which are known to be involved in wound repair and histocompatibility.

Methodology/principal findings: We demonstrate for the first time in corals that these cells are involved in the organismal response to pathogenic and temperature stress. In sea fans with both naturally occurring infections and experimental inoculations with the fungal pathogen Aspergillus sydowii, an inflammatory response, characterized by a massive increase of amoebocytes, was evident near infections. Melanosomes were detected in amoebocytes adjacent to protective melanin bands in infected sea fans; neither was present in uninfected fans. In naturally infected sea fans a concurrent increase in prophenoloxidase activity was detected in infected tissues with dense amoebocytes. Sea fans sampled in the field during the 2005 Caribbean Bleaching Event (a once-in-hundred-year climate event) responded to heat stress with a systemic increase in amoebocytes and amoebocyte densities were also increased by elevated temperature stress in lab experiments.

Conclusions/significance: The observed amoebocyte responses indicate that sea fan corals use cellular defenses to combat fungal infection and temperature stress. The ability to mount an inflammatory response may be a contributing factor that allowed the survival of even infected sea fan corals during a stressful climate event.

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Amoebocytes in mesoglea (connective tissue) of naturally diseased sea fan corals.A) Healthy coral with granular amoebocytes dispersed in mesoglea as indicated by arrows. B) Diseased coral with an increase in granular amoebocytes in the mesoglea. Scale bar = 25 µm.
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pone-0001811-g002: Amoebocytes in mesoglea (connective tissue) of naturally diseased sea fan corals.A) Healthy coral with granular amoebocytes dispersed in mesoglea as indicated by arrows. B) Diseased coral with an increase in granular amoebocytes in the mesoglea. Scale bar = 25 µm.

Mentions: The cellular component of the sea fan's immune response to pathogen infection was quantified by calculating the area of mesoglea (tissue between the polyps) occupied by amoebocytes from histological images. We detected a sizeable and dramatic increase of the granular amoebocytes in tissue infected with fungus, indicative of a classic inflammatory response. In healthy corals the amoebocytes comprise an average of 15.2% of the mesogleal tissue area and appear uniformly interspersed in the tissue (Figure 2A). In diseased corals there are more amoebocytes aggregated in the mesoglea adjacent to areas with fungal infections and they occupy a greater surface area (24.5%) (Figure 2B, Figure 3, n = 8, X2 = 28.93, p<0.0001).


Cellular responses in sea fan corals: granular amoebocytes react to pathogen and climate stressors.

Mydlarz LD, Holthouse SF, Peters EC, Harvell CD - PLoS ONE (2008)

Amoebocytes in mesoglea (connective tissue) of naturally diseased sea fan corals.A) Healthy coral with granular amoebocytes dispersed in mesoglea as indicated by arrows. B) Diseased coral with an increase in granular amoebocytes in the mesoglea. Scale bar = 25 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2267492&req=5

pone-0001811-g002: Amoebocytes in mesoglea (connective tissue) of naturally diseased sea fan corals.A) Healthy coral with granular amoebocytes dispersed in mesoglea as indicated by arrows. B) Diseased coral with an increase in granular amoebocytes in the mesoglea. Scale bar = 25 µm.
Mentions: The cellular component of the sea fan's immune response to pathogen infection was quantified by calculating the area of mesoglea (tissue between the polyps) occupied by amoebocytes from histological images. We detected a sizeable and dramatic increase of the granular amoebocytes in tissue infected with fungus, indicative of a classic inflammatory response. In healthy corals the amoebocytes comprise an average of 15.2% of the mesogleal tissue area and appear uniformly interspersed in the tissue (Figure 2A). In diseased corals there are more amoebocytes aggregated in the mesoglea adjacent to areas with fungal infections and they occupy a greater surface area (24.5%) (Figure 2B, Figure 3, n = 8, X2 = 28.93, p<0.0001).

Bottom Line: Melanosomes were detected in amoebocytes adjacent to protective melanin bands in infected sea fans; neither was present in uninfected fans.The observed amoebocyte responses indicate that sea fan corals use cellular defenses to combat fungal infection and temperature stress.The ability to mount an inflammatory response may be a contributing factor that allowed the survival of even infected sea fan corals during a stressful climate event.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Texas at Arlington, Arlington, Texas, United States of America. Mydlarz@UTA.edu

ABSTRACT

Background: Climate warming is causing environmental change making both marine and terrestrial organisms, and even humans, more susceptible to emerging diseases. Coral reefs are among the most impacted ecosystems by climate stress, and immunity of corals, the most ancient of metazoans, is poorly known. Although coral mortality due to infectious diseases and temperature-related stress is on the rise, the immune effector mechanisms that contribute to the resistance of corals to such events remain elusive. In the Caribbean sea fan corals (Anthozoa, Alcyonacea: Gorgoniidae), the cell-based immune defenses are granular acidophilic amoebocytes, which are known to be involved in wound repair and histocompatibility.

Methodology/principal findings: We demonstrate for the first time in corals that these cells are involved in the organismal response to pathogenic and temperature stress. In sea fans with both naturally occurring infections and experimental inoculations with the fungal pathogen Aspergillus sydowii, an inflammatory response, characterized by a massive increase of amoebocytes, was evident near infections. Melanosomes were detected in amoebocytes adjacent to protective melanin bands in infected sea fans; neither was present in uninfected fans. In naturally infected sea fans a concurrent increase in prophenoloxidase activity was detected in infected tissues with dense amoebocytes. Sea fans sampled in the field during the 2005 Caribbean Bleaching Event (a once-in-hundred-year climate event) responded to heat stress with a systemic increase in amoebocytes and amoebocyte densities were also increased by elevated temperature stress in lab experiments.

Conclusions/significance: The observed amoebocyte responses indicate that sea fan corals use cellular defenses to combat fungal infection and temperature stress. The ability to mount an inflammatory response may be a contributing factor that allowed the survival of even infected sea fan corals during a stressful climate event.

Show MeSH
Related in: MedlinePlus