Cnidarian Pattern Recognition Receptor Repertoires Reflect Both Phylogeny and Life History Traits

Pattern recognition receptors (PRRs) are evolutionarily ancient and crucial components of innate immunity, recognizing danger-associated molecular patterns (DAMPs) and activating host defenses. Basal non-bilaterian animals such as cnidarians must rely solely on innate immunity to defend themselves from pathogens. By investigating cnidarian PRR repertoires we can gain insight into the evolution of innate immunity in these basal animals. Here we utilize the increasing amount of available genomic resources within Cnidaria to survey the PRR repertoires and downstream immune pathway completeness within 15 cnidarian species spanning two major cnidarian clades, Anthozoa and Medusozoa. Overall, we find that anthozoans possess prototypical PRRs, while medusozoans appear to lack these immune proteins. Additionally, anthozoans consistently had higher numbers of PRRs across all four classes relative to medusozoans, a trend largely driven by expansions in NOD-like receptors and C-type lectins. Symbiotic, sessile, and colonial cnidarians also have expanded PRR repertoires relative to their non-symbiotic, mobile, and solitary counterparts. Interestingly, cnidarians seem to lack key components of mammalian innate immune pathways, though similar to PRR numbers, anthozoans possess more complete immune pathways than medusozoans. Together, our data indicate that anthozoans have greater immune specificity than medusozoans, which we hypothesize to be due to life history traits common within Anthozoa. Overall, this investigation reveals important insights into the evolution of innate immune proteins within these basal animals

Cellular Responses in Sea Fan Corals: Granular Amoebocytes React to Pathogen and Climate Stressors

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

Deciphering coral disease dynamics: integrating host, microbiome, and the changing environment

Diseases of tropical reef organisms is an intensive area of study, but despite significant advances in methodology and the global knowledge base, identifying the proximate causes of disease outbreaks remains difficult. The dynamics of infectious wildlife diseases are known to be influenced by shifting interactions among the host, pathogen, and other members of the microbiome, and a collective body of work clearly demonstrates that this is also the case for the main foundation species on reefs, corals. Yet, among wildlife, outbreaks of coral diseases stand out as being driven largely by a changing environment. These outbreaks contributed not only to significant losses of coral species but also to whole ecosystem regime shifts. Here we suggest that to better decipher the disease dynamics of corals, we must integrate more holistic and modern paradigms that consider multiple and variable interactions among the three major players in epizootics: the host, its associated microbiome, and the environment. In this perspective, we discuss how expanding the pathogen component of the classic host-pathogen-environment disease triad to incorporate shifts in the microbiome leading to dysbiosis provides a better model for understanding coral disease dynamics. We outline and discuss issues arising when evaluating each component of this trio and make suggestions for bridging gaps between them. We further suggest that to best tackle these challenges, researchers must adjust standard paradigms, like the classic one pathogen-one disease model, that, to date, have been ineffectual at uncovering many of the emergent properties of coral reef disease dynamics. Lastly, we make recommendations for ways forward in the fields of marine disease ecology and the future of coral reef conservation and restoration given these observations

Complementary approaches to diagnosing marine diseases: a union of the modern and the classic

Linking marine epizootics to a specific aetiology is notoriously difficult. Recent diagnostic successes show that marine disease diagnosis requires both modern, cutting-edge technology (e.g. metagenomics, quantitative realtime PCR) and more classic methods (e.g. transect surveys, histopathology and cell culture). Here, we discuss how this combination of traditional and modern approaches is necessary for rapid and accurate identification of marine diseases, and emphasize how sole reliance on any one technology or technique may lead disease investigations astray. We present diagnostic approaches at different scales, from the macro (environment, community, population and organismal scales) to the micro (tissue, organ, cell and genomic scales). We use disease case studies from a broad range of taxa to illustrate diagnostic successes from combining traditional and modern diagnostic methods. Finally, we recognize the need for increased capacity of centralized databases, networks, data repositories and contingency plans for diagnosis and management of marine disease.Keywords: marine epizootics, aetiology, marine disease, diagnosticsKeywords: marine epizootics, aetiology, marine disease, diagnostic

Sex, War, and Disease: The Role of Parasite Infection on Weapon Development and Mating Success in a Horned Beetle (Gnatocerus cornutus)

While parasites and immunity are widely believed to play important roles in the evolution of male ornaments, their potential influence on systems where male weaponry is the object of sexual selection is poorly understood. We experimentally infect larval broad-horned flour beetles with a tapeworm and study the consequent effects on: 1) adult male morphology 2) male-male contests for mating opportunities, and 3) induction of the innate immune system. We find that infection significantly reduces adult male size in ways that are expected to reduce mating opportunities in nature. The sum of our morphological, competition, and immunological data indicate that during a life history stage where no new resources are acquired, males allocate their finite resources in a way that increases future mating potential

Physiological Chemistry of Pseudopterosin Biosynthesis in Symbiotic Dinoflagellates from the Soft Coral Pseudopterogorgia elisabethae

The pseudopterosins (Ps) are unique diterpene glycosides with potent anti­ inflammatory properties which were isolated from the gorgonian Pseudopterogorgia elisabethae. The relationship of the anti-inflammatory effects of Ps to their endogenous function in the coral-symbiont association is not known. In this study the biosynthetic origins and the potential endogenous physiological function of the Ps within the coral-symbiont complex are investigated.Significant levels of endogenous Ps A, B, C and D were identified within the dinoflagellate symbiont, Symbiodinium sp, isolated from P. elisabethae. Biosynthetic studies using tritiated geranylgeranyl bisphosphate, yielded radiochemically pure Ps A, 8, C and D and the first committed intermediate, elisabethatriene. The photosynthetic production of organic carbon in Symbiodinium sp. was traced with the aid of radiolabelled 14C02 uptake studies. Results indicated that photosynthate is a significant carbon source for the production of the pseudopterosins and their intermediates. Ps constitute 10-15% of the intracellular lipids of Symbiodinium sp. and are biosynthesized at a low daily rate. This is the first report of Ps biosynthesis occurs within the algal symbiont of P. elisabethae, and thus prompted further study of the physiological implications of this biosynthesis.In comparative physiological studies of Symbiodinium sp. isolated from P. elisabethae and in the free-living dinoflagellate Heterocapsa pygmaea, physical sonic injury induced a significant oxidative burst of highly reactive oxygen species (ROS). Symbiodinium sp. cells from P. elisabethae had an attenuated oxidative burst in response to these injuries when compared to H. pygmaea and other related Symbiodinium species. Exogenously added Ps inhibited ROS release in a dose­ dependant manner in physically stressed cells of H. pygmaea and Symbiodinium sp. isolated from P. americana. The reductions in ROS by Ps were not due to direct anti­-oxidant effect indicating that they may provide a protective role to the cell membrane.In studies with gorgonian corals, hydrogen peroxide was identified as signal molecule in response to physical and heat stress. In these experiments P. elisabethae also exhibited a muted stress response when compared to related gorgonian corals. Overall this study demonstrates that the biosynthetic production of Ps in Symbiodinium sp. cells from P. elisabethae occurs in sufficient quantities to confer beneficial effects to both symbiont and host cells

BOOK REVIEW | The Biology of Reefs and Reef Organisms

Walter Goldberg dedicates his new reference book, The Biology of Reefs and Reef Organisms, to "the condition of the reefs the way I remember them, with the hope that they might be that way again someday." He follows this simple, emotional, dedicatory plea with thorough descriptions of reef formation and colorful reef inhabitants, and ends with a note of hope

Physiological Chemistry of Pseudopterosin Biosynthesis in Symbiotic Dinoflagellates from the Soft Coral Pseudopterogorgia elisabethae

The pseudopterosins (Ps) are unique diterpene glycosides with potent anti­ inflammatory properties which were isolated from the gorgonian Pseudopterogorgia elisabethae. The relationship of the anti-inflammatory effects of Ps to their endogenous function in the coral-symbiont association is not known. In this study the biosynthetic origins and the potential endogenous physiological function of the Ps within the coral-symbiont complex are investigated.Significant levels of endogenous Ps A, B, C and D were identified within the dinoflagellate symbiont, Symbiodinium sp, isolated from P. elisabethae. Biosynthetic studies using tritiated geranylgeranyl bisphosphate, yielded radiochemically pure Ps A, 8, C and D and the first committed intermediate, elisabethatriene. The photosynthetic production of organic carbon in Symbiodinium sp. was traced with the aid of radiolabelled 14C02 uptake studies. Results indicated that photosynthate is a significant carbon source for the production of the pseudopterosins and their intermediates. Ps constitute 10-15% of the intracellular lipids of Symbiodinium sp. and are biosynthesized at a low daily rate. This is the first report of Ps biosynthesis occurs within the algal symbiont of P. elisabethae, and thus prompted further study of the physiological implications of this biosynthesis.In comparative physiological studies of Symbiodinium sp. isolated from P. elisabethae and in the free-living dinoflagellate Heterocapsa pygmaea, physical sonic injury induced a significant oxidative burst of highly reactive oxygen species (ROS). Symbiodinium sp. cells from P. elisabethae had an attenuated oxidative burst in response to these injuries when compared to H. pygmaea and other related Symbiodinium species. Exogenously added Ps inhibited ROS release in a dose­ dependant manner in physically stressed cells of H. pygmaea and Symbiodinium sp. isolated from P. americana. The reductions in ROS by Ps were not due to direct anti­-oxidant effect indicating that they may provide a protective role to the cell membrane.In studies with gorgonian corals, hydrogen peroxide was identified as signal molecule in response to physical and heat stress. In these experiments P. elisabethae also exhibited a muted stress response when compared to related gorgonian corals. Overall this study demonstrates that the biosynthetic production of Ps in Symbiodinium sp. cells from P. elisabethae occurs in sufficient quantities to confer beneficial effects to both symbiont and host cells

The presence of multiple phenoloxidases in Caribbean reef-building corals

The melanin-synthesis pathways, phenoloxidase (PO) and laccases, are staple components of invertebrate immunity and have been shown to be vital in disease resistance. The importance of this pathway in immunity is a consequence of the release of oxygen radicals with cytotoxic effects and the production of insoluble melanin, which aids in the encapsulation of pathogens and parasites. Recently, melanization has been demonstrated as a critical immune response in several coral systems, although the biochemical components have not been thoroughly investigated. Coral diseases are posing a serious threat to coral reef survival, necessitating a full understanding of resistance mechanisms. In this study, we take a comparative approach to probe potential pathway components of melanin-synthesis in seven species from four different families of healthy Caribbean reef-building corals. Using different quinone substrates, we tested for the activity of the POs catecholase and cresolase, as well as laccase activity in each coral species. Since many invertebrate POs demonstrate some dependence on cations such as copper, calcium and magnesium, we treated the coral extracts with the chelators EDTA and EGTA to test the reliance of coral catecholase on these cations. The activity of the antioxidants peroxidase, superoxide dismutase and catalase was also tested in each coral and correlated to PO activity. All corals had demonstrable catecholase, cresolase and laccase activities, but only catecholase and cresolase activities varied significantly among species. Catecholase activity in each coral species was reduced by treatment with EDTA and EGTA, although some coral species were less affected than the others. Overall, these data show remarkable heterogeneity among the seven coral species of boulder-like reef building Caribbean coral. These differences may originate from the level of investment of each coral species into immunity and may explain disease ecology on the reef