Deborah J. Gochfeld

Molecular community profiling reveals impacts of time, space, and disease status on the bacterial community associated with the Caribbean sponge Aplysina cauliformis.

Reports of marine sponge diseases have increased in recent years, but few etiologic agents have been identified. Aplysina red band syndrome (ARBS), a condition observed in the Caribbean sponge Aplysina cauliformis, is characterized by a rust-colored leading margin. Culture-independent methods (terminal restriction fragment length polymorphism and clone library analyses) were used to assess bacterial communities associated with healthy and ARBS-affected sponges from two locations over 2 years. Although the bacterial communities associated with healthy and ARBS-affected sponges were significantly different, the sponges maintained a core bacterial community across space, time, and health status. Ten terminal restriction fragments were shown to change significantly between sponge health conditions, with six increasing in abundance with disease and four decreasing. The prevalence of the photosymbiont Synechococcus spongiarum decreased with ARBS infection, suggesting a functional consequence of disease. After cultivating a red-pigmented Leptolyngbya strain from ARBS lesions, transmission studies were conducted to determine whether this organism was the ARBS pathogen. Despite significantly increased abundance of Leptolyngbya spp. in diseased sponges, signs of ARBS were not observed in healthy sponges following 24 days of contact with the cultured strain. Additional work with this model system is needed to increase our understanding of the dynamics of marine diseases.

HYBRID VIGOR IN A TROPICAL PACIFIC SOFT‐CORAL COMMUNITY

Although hybridization is a relatively widespread phenomenon in marine ecosystems, the ecological importance of hybrids is poorly understood. As crosses between two distinct genotypes, hybrids might express fitness characteristics similar to either parent species, or they might produce unique phenotypic attributes that make them more or less fit than either parent species. We identified a potential hybrid zone among soft corals in a back-reef community on Guam, where the broadcast-spawning species Sinularia maxima and S. polydactyla co-occur. Morphological and chemical traits confirmed the intermediate and unique status of the putative hybrid. Laboratory cross-fertilization experiments using S. maxima and S. polydactyla gametes demonstrated that barriers to hybridization are absent and that the laboratory-reared hybrids developed specific characteristics identified in adult hybrid field populations. Changes in the populations of each parent species and the hybrid were monitored over a decade. While popula...

Spatial Variability in Secondary Metabolites of the Indo-Pacific Sponge Stylissa massa

Chemical diversity represents a measure of selective pressures acting on genotypic variability. In order to understand patterns of chemical ecology and biodiversity in the environment, it is necessary to enhance our knowledge of chemical diversity within and among species. Many sponges produce variable levels of secondary metabolites in response to diverse biotic and abiotic environmental factors. This study evaluated intra-specific variability in secondary metabolites in the common Indo-Pacific sponge Stylissa massa over various geographic scales, from local to ocean basin. Several major metabolites were quantified in extracts from sponges collected in American Samoa, Pohnpei, Saipan, and at several sites and depths in Guam. Concentrations of several of these metabolites varied geographically across the Pacific basin, with American Samoa and Pohnpei exhibiting the greatest differences, and Guam and Saipan more similar to each other. There were also significant differences in concentrations among different sites and depths within Guam. The crude extract of S. massa exhibited feeding deterrence against the omnivorous pufferfish Canthigaster solandri at natural concentrations, however, none of the isolated compounds was deterrent at the maximum natural concentrations observed, nor were mixtures of these compounds, thus emphasizing the need for bioassay-guided isolation to characterize specific chemical defenses. Antibacterial activity against a panel of ecologically relevant pathogens was minimal. Depth transplants, predator exclusion, and UV protection experiments were performed, but although temporal variability in compound concentrations was observed, there was no evidence that secondary metabolite concentration in S. massa was induced by any of these factors. Although the reasons behind the variability observed in the chemical constituents of S. massa are still in question, all sponges are not created equal from a chemical standpoint, and these studies provide further insights into patterns of chemical diversity within S. massa.

Trade-Offs in Defensive Metabolite Production But Not Ecological Function in Healthy and Diseased Sponges

Diseases of marine organisms, and sponges in particular, are increasingly reported worldwide. Prior research indicates that the survival of sponges on reefs is due largely to their production of biologically active secondary metabolites that provide protection from a diversity of stressors. Aplysina Red Band Syndrome (ARBS) is an emerging disease affecting Caribbean rope sponges (Aplysina spp.), but it is not known whether secondary metabolites play a role in disease susceptibility and resistance. To investigate whether differences in secondary metabolites may explain variability in susceptibility to ARBS in Aplysina cauliformis, we used high performance liquid chromatography (HPLC) to generate chemical profiles from healthy tissue in both healthy and diseased sponges, and quantified peak areas for 15 metabolites. Analyses of healthy and diseased sponges revealed qualitative and quantitative differences in their chemical profiles. Aplysamine-1 and fistularin-3 were produced in significantly higher concentrations by healthy sponges, whereas aerothionin and 11-oxoaerothionin were found only in diseased sponges. At natural concentrations, extracts from both healthy and diseased sponges deterred feeding by an omnivorous reef fish. Fistularin-3 deterred feeding at concentrations found in healthy sponges, but not at concentrations found in diseased sponges. Aerothionin deterred feeding at concentrations found in diseased sponges, and may at least partially replace the loss of fistularin-3 as a feeding deterrent compound following pathogenesis, suggesting a trade-off in the production of feeding deterrent compounds. Extracts from healthy and diseased sponges inhibited bacterial growth, and both aplysamine-1 and fistularin-3 displayed selective antibacterial activity. Despite differences in secondary metabolite production between healthy and diseased sponges, the stress associated with ARBS does not appear to compromise the ability of A. cauliformis to maintain defenses against some of its natural enemies.

Chemical Constituents of the Deep Reef Caribbean Sponges Plakortis angulospiculatus and Plakortis halichondrioides and Their Anti-inflammatory Activities

Chemical investigations of two collections of the deep reef Caribbean sponge Plakortis angulospiculatus resulted in the isolation of a new compound (1) along with the known compound spiculoic acid B (2) belonging to the spiculoic acid class and four other new compounds (3-6) belonging to the zyggomphic acid class. Three new aromatic compounds (7-9) were isolated from the Caribbean sponge Plakortis halichondrioides. The structural determination of the compounds was based on extensive NMR and mass spectroscopic analysis. The isolated compounds 1-7 were tested for their anti-inflammatory activity using in vitro assays for inhibition of inducible nitric oxide synthase and nuclear factor kappa B (NFκB) activity, as well as inhibition of intracellular reactive oxygen species generation as a result of oxidative stress. The cytotoxicity of these compounds was also evaluated to determine the selectivity index of their bioactivity with respect to cytotoxicity. Compounds 1 and 4 were more potent than the positive control in inhibiting NFκB activity and had IC(50) values of 0.47 and 2.28 μM, respectively.

Variability in chemical defense across a shallow to mesophotic depth gradient in the Caribbean sponge Plakortis angulospiculatus

The transition between shallow and mesophotic coral reef communities in the tropics is characterized by a significant gradient in abiotic and biotic conditions that could result in potential trade-offs in energy allocation. The mesophotic reefs in the Bahamas and the Cayman Islands have a rich sponge fauna with significantly greater percent cover of sponges than in their respective shallow reef communities, but relatively low numbers of spongivores. Plakortisangulospiculatus, a common sponge species that spans the depth gradient from shallow to mesophotic reefs in the Caribbean, regenerates faster following predation and invests more energy in protein synthesis at mesophotic depths compared to shallow reef conspecifics. However, since P. angulospiculatus from mesophotic reefs typically contain lower concentrations of chemical feeding deterrents, they are not able to defend new tissue from predation as efficiently as conspecifics from shallow reefs. Nonetheless, following exposure to predators on shallow reefs, transplanted P. angulospiculatus from mesophotic depths developed chemical deterrence to predatory fishes. A survey of bioactive extracts indicated that a specific defensive metabolite, plakortide F, varied in concentration with depth, producing altered deterrence between shallow and mesophotic reef P. angulospiculatus. Different selective pressures in shallow and mesophotic habitats have resulted in phenotypic plasticity within this sponge species that is manifested in variable chemical defense and tissue regeneration at wound sites.

Cnidarian Immunity: From Genomes to Phenomes

Cnidarians rely on the innate immune defenses based on self/non-self recognition, signaling and effector responses to kill pathogens and heal wounds. Like other invertebrates, the immune system of cnidarians can be classified into several functional components and many of these elements have now been described in various cnidarian model systems. These include recognition receptors, toll-like receptors and peptidoglycan binding proteins, prophenoloxidase and melanin synthesis for an impermeable melanin barrier, anti-microbial proteins and molecules, reactive oxygen-producing and scavenging systems and wound repair and cellular systems. This chapter will summarize the current state of knowledge of cnidarian immune pathways and mechanisms. We will summarize the available data, guiding the reader through the steps of initiating and executing an immune response: recognition, signaling, effector and repair mechanisms. We will also explore the current research of constitutive immunity observed in healthy organisms and elicited immune responses seen in naturally infected organisms or organisms exposed to live pathogens or pathogen associated molecular patterns. We will connect these known immune pathways with how they are expressed and regulated and how this may influence the wide variation in disease resistance observed in the field, both within and between species. The overarching goal of this chapter is to take the reader from a genomic to phenotypic perspective, while keeping pathways and mechanisms in a whole organism and ecological context, whenever possible.

Chlorinated didemnins from the tunicate Trididemnum solidum.

Chemical investigation of the tunicate Trididemnum solidum resulted in the isolation of two new chlorinated compounds belonging to the didemnin class, along with two known compounds didemnin A and didemnin B. The structural determination of the compounds was based on extensive NMR and mass spectroscopic analysis. The isolated compounds 1–4 were tested for their anti-inflammatory activity using in vitro assays for inhibition of inducible nitric oxide synthase (iNOS) and nuclear factor-kappa B (NF-κB) activity. The anti-cell proliferative activity of the above compounds was also evaluated against four solid tumor cell lines.

Hard coral (Porites lobata) extracts and homarine on cytochrome P450 expression in Hawaiian butterflyfishes with different feeding strategies

Dietary specialists tend to be less susceptible to the effects of chemical defenses produced by their prey compared to generalist predators that feed upon a broader range of prey species. While many researchers have investigated the ability of insects to detoxify dietary allelochemicals, little research has been conducted in marine ecosystems. We investigated metabolic detoxification pathways in three species of butterflyfishes: the hard coral specialist feeder, Chaetodon multicinctus, and two generalist feeders, Chaetodon auriga and Chaetodon kleinii. Each species was fed tissue homogenate of the hard coral Porites lobata or the feeding deterrent compound homarine (found in the coral extract), and the expression and catalytic activity of cytochrome P450 (CYP) 3A-like and CYP2-like enzymes were examined after one-week of treatment. The P. lobata homogenate significantly induced content and catalytic activity of CYP2-like and CYP3A-like forms, by 2-3 fold and by 3-9 fold, respectively, in C. multicinctus. Homarine caused a significant decrease of CYP2-like and CYP3A-like proteins at the high dose in C. kleinii and 60-80% mortality in that species. Homarine also induced CYP3A-like content by 3-fold and catalytic activity by 2-fold in C. auriga, while causing non-monotonic increases in CYP2-like and CYP3A-like catalytic activity in C. multicinctus. Our results indicate that dietary exposure to coral homogenates and the feeding deterrent constituent within these homogenates caused species-specific modulation of detoxification enzymes consistent with the prey selection strategies of generalist and specialist butterflyfishes.

Aposematic coloration does not deter corallivory by fish on the coral Montastraea cavernosa

Abstract Predation on corals by visual predators is a significant source of partial or total mortality on coral reefs, and corals have evolved strategies, including chemical defenses, to deter predation. One mechanism that organisms use to communicate the presence of chemical defenses is aposematic coloration, or the display of bright coloration as a warning to visual predators such as fish. Corals exhibit multiple colors, and it has been hypothesized that one role for this variability in coloration is as an aposematic warning of adverse palatability. Here, we test green and orange color morphs of the Caribbean coral Montastraea cavernosa for the presence of chemical defenses and whether their differences in coloration elicited different feeding responses. While M. cavernosa is chemically defended, there is no difference in feeding deterrence between color morphs; thus, the different color morphs of this coral species do not appear to represent an example of aposematic coloration.