Sponge Xestospongia Muta Research Articles

Together till the end: endosymbiosis of the annelid Haplosyllides floridana in the giant barrel-shaped sponge Xestospongia muta throughout the Tropical Atlantic

Abstract The symbiotic relationship between the syllid polychaete, Haplosyllides floridana Augener, 1922, and the barrel-shaped sponge Xestospongia muta (Schmidt, 1870), originally documented solely in the Caribbean, is presumed to be species-specific. Recently, the host sponge has been found as a single species distributed across approximately 8000 km (from 26°N to 22°S). Herein we addressed new spatial and bathymetric population records of H. floridana to question the persistence of the association with X. muta, and whether, in the case of an association, the polychaete remains as a single species throughout this extensive distribution. Our findings change the restricted distribution of H. floridana, revealing a remarkable association with X. muta from Tropical north-western to south-western Atlantic including records in the Fernando de Noronha Archipelago and the Almirante Saldanha Seamount, at 270 m deep. The populations analysed in this study are morphologically consistent. The study underscores the need for further investigations into the connectivity of Xestospongia species, the presence of Haplosyllides in other ocean basins, and the shared evolutionary history between Xestospongia and Haplosyllides. The observed life cycle completion of H. floridana within the host sponge suggests a potential co-evolutionary relationship, offering insights into the intricate dynamics of symbiotic associations in marine ecosystems.

Comparative analysis of assembly algorithms to optimize biosynthetic gene cluster identification in novel marine actinomycete genomes

Many marine sponges harbor dense communities of microbes that aid in the chemical defense of these nonmotile hosts. Metabolites that comprise this chemical arsenal can have pharmaceutically-relevant activities such as antibacterial, antiviral, antifungal and anticancer properties. Previous investigation of the Caribbean giant barrel sponge Xestospongia muta revealed a microbial community including novel Actinobacteria, a phylum well known for its production of antibiotic compounds. This novel assemblage was investigated for its ability to produce compounds that inhibit M. tuberculosis by using a bioinformatics approach. Microbial extracts were tested for their ability to inhibit growth of M. tb and genomes of the 11 strains that showed anti-M. tb activity including Micrococcus (n=2), Micromonospora (n=4), Streptomyces (n=3), and Brevibacterium spp. (n=2) were sequenced by using Illumina MiSeq. Three assembly algorithms/pipelines (SPAdes, A5-miseq and Shovill) were compared for their ability to construct contigs with minimal gaps to maximize the probability of identifying complete biosynthetic gene clusters (BGCs) present in the genomes. Although A5-miseq and Shovill usually assembled raw reads into the fewest contigs, after necessary post-assembly filtering, SPAdes generally produced the most complete genomes with the fewest contigs. This study revealed the strengths and weaknesses of the different assemblers based on their ease of use and ability to be manipulated based on output format. None of the assembly methods handle contamination well and high-quality DNA is a prerequisite. BGCs of compounds with known anti-TB activity were identified in all Micromonospora and Streptomyces strains (genomes > 5 Mb), while no such BGCs were identified in Micrococcus or Brevibacterium strains (genomes < 5 Mb). The majority of the putative BGCs identified were located on contig edges, emphasizing the inability of short-read assemblers to resolve repeat regions and supporting the need for long-read sequencing to fully resolve BGCs.

Detrimental conditions affecting Xestospongia muta across shallow and mesophotic coral reefs off the southwest coast of Puerto Rico.

Sponges are fundamental components of coral reef communities and, unfortunately, like other major benthic members, they too have been impacted by epizootic and panzootic events. We report on the prevalence of disease-like conditions affecting populations of the giant barrel sponge Xestospongia muta across shallow and mesophotic coral reefs off La Parguera Natural Reserve (LPNR) and Mona Island Marine Reserve (MIMR) in Puerto Rico. Four different conditions affecting X. muta were observed during our surveys, of which 3 have been previously reported: cyclic spotted bleaching (CSB; apparently non-lethal), Xestospongia-tissue wasting disease (X-TWD; apparently lethal), and sponge orange band disease (SOB; sparsely associated with X-TWD infected individuals). Additionally, we describe a fourth condition, Xestospongia-tissue hardening condition (X-THC), a previously unreported disease recently observed along the insular shelf margin off LPNR and MIMR. Within LPNR, a total of 764 specimens of X. muta were inspected and measured. Of these, 590 sponges (72.2%) had CSB, 25 (3.27%) had signs of X-TWD, 7 (0.92%) had SOB, and the remaining 142 (18.6%) were apparently healthy. Three colonies inhabiting upper mesophotic depths on the LPNR insular shelf showed signs of CSB and X-TWD. At MIMR, video-transect surveys revealed a total of 514 colonies, of which 40 (7.78%) had signs of CSB and/or XTWD, 14 (2.72%) were affected by X-THC, while the remaining 460 (89.5%) showed no external signs of disease and appeared healthy. The presence of 4 concomitant disease-like conditions in barrel sponges of Puerto Rico is alarming, and indicative of the deteriorating status of Caribbean coral reefs.

Seasonal, lunar, and diel patterns in spawning by the giant barrel sponge, Xestospongia muta

Temporal patterns in giant barrel sponge (Xestospongia muta) spawning were compiled from 32 observations spanning 17 years and three Caribbean locations (Florida, Belize, and Haiti). The records were analyzed for patterns in seasonality, lunar periodicity, and diel rhythm to develop a predictive spawning window. Results indicate that spawning is concentrated from mid-April to late May. Most spawning events occurred around the first quarter moon; a smaller pulse occurred just before the third quarter moon. All spawning events were observed in the morning and fell within 779–987 min of the previous night’s sunset. Eggs of X. muta were all negatively buoyant and blanketed the areas within and surrounding the sponge; this limited gamete dispersal may be the driver behind heavily localized genetic retention.

An Ichip-Domesticated Sponge Bacterium Produces an N-Acyltyrosine Bearing an α-Methyl Substituent.

The ichip (isolation chip) was employed for the first time in a marine sponge (Xestospongia muta), and a putatively new bacterial species, Alteromonas sp. RKMC-009, was isolated. Strain RKMC-009 produces a novel N-acyltyrosine (1) that is appended with a rare α-methyl substituent within the aminoacyl moiety and also exhibits Gram-positive antibacterial activity. We determined through an SAR experiment that the α-methyl is necessary for Staphylococcus activity of 1 and that it enhances Enterococcus activity.

Manzamine C, an alkaloid indole as an inhibitor of the cancer cells adapted to nutrient starvation, from an Indonesian marine sponge of Xestospongia muta

Research of Manzamine C, Indole Alkaloids as cancer cell inhibitors in nutrient starvation, from the Indonesian Marine Sponge Xestospongia muta was done on May 2018. The goal of this study is to determine the cytotoxic activity of metabolite compounds of Xetospongia muta under glucose starvation. The active metabolite isolated using bioassay-guided separation with several steps of chromatography. Interpretation of IR data indicates that the active metabolites have the functional group of secondary NH2 at 3435.56 cm1, CH methyl at 2853.39 cm1, CH methylene at 2769.64 cm1 and CN imine at 1637.27 cm1. The LCMS-ESI analysis showed that the active metabolite has a molecular weight [M+H]+ 347.445 m/z which indicates the active metabolite has a molecular formula C23H29N3. The activity of metabolite compounds against PANC-1 cells showed cytotoxic activity under glucose starvation conditions with values IC50=10 μM, whereas no growth inhibition was observed up to 100 μM under the general culture conditions.

Variations in Microbial Diversity and Metabolite Profiles of the Tropical Marine Sponge Xestospongia muta with Season and Depth.

Xestospongia muta is among the most emblematic sponge species inhabiting coral reefs of the Caribbean Sea. Besides being the largest sponge species growing in the Caribbean, it is also known to produce secondary metabolites. This study aimed to assess the effect of depth and season on the symbiotic bacterial dynamics and major metabolite profiles of specimens of X. muta thriving in a tropical marine biome (Portobelo Bay, Panamá), which allow us to determine whether variability patterns are similar to those reported for subtropical latitudes. The bacterial assemblages were characterized using Illumina deep-sequencing and metabolomic profiles using UHPLC-DAD-ELSD from five depths (ranging 9-28m) across two seasons (spring and autumn). Diverse symbiotic communities, representing 24 phyla with a predominance of Proteobacteria and Chloroflexi, were found. Although several thousands of OTUs were determined, most of them belong to the rare biosphere and only 23 to a core community. There was a significant difference between the structure of the microbial communities in respect to season (autumn to spring), with a further significant difference between depths only in autumn. This was partially mirrored in the metabolome profile, where the overall metabolite composition did not differ between seasons, but a significant depth gradient was observed in autumn. At the phyla level, Cyanobacteria, Firmicutes, Actinobacteria, and Spirochaete showed a mild-moderate correlation with the metabolome profile. The metabolomic profiles were mainly characterized by known brominated polyunsaturated fatty acids. This work presents findings about the composition and dynamics of the microbial assemblages of X. muta expanding and confirming current knowledge about its remarkable diversity and geographic variability as observed in this tropical marine biome.

Evidence for shifting genetic structure among Caribbean giant barrel sponges in the Florida Keys

The giant barrel sponge Xestospongia muta is a dominant member of Caribbean reef ecosystems. Populations of X. muta that have been monitored annually in plots on Conch and Pickles Reefs in the Florida Keys increased by as much as 122% between 2000 and 2012, raising questions about the processes structuring these growing populations. Microsatellite markers for the closely related Pacific giant barrel sponge X. testudinaria were optimized for X. muta using individuals from Conch and Pickles Reefs (located 5.5 km apart). Further, within one plot on Conch Reef (AQS3 − 20 m depth), each individual of X. muta was mapped and genotyped to investigate fine-scale spatial genetic structuring. Significant spatial autocorrelation was detected at 2-m distance, but the dispersal distance and neighborhood size could not be determined, suggesting that recruitment extends beyond the plot. Finally, sponge samples from Conch Reef (15- and 20-m depth) and Pickles Reefs (15-m depth) were pooled into a single population for Bayesian cluster analyses. Results showed two distinct genetic clusters in the population, Clusters 1 and 2, with a near absence of Cluster 2 sponges among the largest individuals. Comparisons of the microsatellite data with mortality and recruitment data obtained from the plots revealed that the shifting genetic structure is due to disproportionate reproduction or recruitment of Cluster 2 sponges. The selective forces responsible for this genetic shift remain unclear, but it is further evidence of the dramatic changes occurring on coral reefs in the Anthropocene.

Macrocyclic bis-quinolizidine alkaloids from Xestospongia muta

A new stereoisomer Meso-araguspongine C together with nine reported macrocyclic bis-quinolizidine alkaloids araguspongines A, C, E, L, N−P, petrosin, and petrosin A were isolated from marine sponge Xestospongia muta. Stereochemistry of meso-araguspongine C (2) and araguspongines N-P (3−5) were established by their NMR data and conformational analyses. Both araguspongine C (1) and meso-araguspongine C (2) exhibited great cytotoxic activity towards HepG-2, HL-60, LU-1, MCF-7, and SK-Mel-2 human cancer cells (IC50 in the range of 0.43–1.02 μM). At a concentration of 20 μM, isolated compounds (1−10) also showed modest inhibitory effects (from 7.6 to 40.8%) on the NO production in LPS activated RAW264.7 macrophages.

Demography alters carbon flux for a dominant benthic suspension feeder, the giant barrel sponge, on Conch Reef, Florida Keys

Abstract A challenge to understanding ecosystem processes is that the functional roles of species are linked with the demography of populations. In many systems, and particularly on coral reefs, the dynamics and structure of populations of many functionally important species has significantly changed over recent decades due to a variety of disturbances, and the changes in the ecological processes mediated by them are poorly understood. Benthic suspension feeders are allogenic ecosystem engineers that contribute to the flow of materials and energy in aquatic systems. There is increasing evidence that sponges dominate this functional group on Caribbean reefs. Using demographic data from 2000 to 2012 and measurements of filtration rates of particulate and dissolved organic carbon, we parameterized a stage‐based matrix model of population‐mediated carbon flux for the Caribbean giant barrel sponge Xestospongia muta on Conch Reef, Florida Keys, to investigate the demographic mechanisms that mediate changes in benthic‐pelagic coupling. Population‐mediated carbon flux increased over time with increasing sponge density and volume, with the largest individuals making the greatest contribution. Elasticity analysis revealed that the growth of sponges in all stages, the survival of sponges in the two largest stages, and the production of new recruits by the largest sponges had the greatest influence on changes in population‐mediated carbon flux. We estimate the mean carbon flux over 2000–2012 for X. muta at Conch Reef was 1575 mg C days−1 m−2, a value that exceeds that of any other single‐species rate. Projections indicated that population‐mediated carbon flux will continue to increase under present conditions; thus, X. muta is expected to play an even larger role in the transfer of carbon from the water column to the benthos on Caribbean coral reefs. Rather than being fixed, the functional role of species within a community are often dynamic and influenced by the demography of populations. The general framework developed here, a conversion of the basic unit of measurement for population models (i.e. the individual) into quantifiable metrics of species traits or activities, may be more broadly applied by further efforts to examine interrelationships between population and ecosystem processes. A plain language summary is available for this article.

The sponge Xestospongia muta offers shelter to the stony coral Madracis auretenra (Northwest Puerto Rico)

Numerous species interactions abound within coral reefs, resulting in either positive, negative, or neutral outcomes. During an exploratory dive on the northwest coast of Puerto Rico, divers observed a colonial field of the yellow pencil coral, Madracis auretenra, engulfing a number of giant barrel sponges, Xestospongia muta. This took place on a reef with strong hydrodynamic forces. The nature of this interaction is complex, and may be an adaptive behavior for the coral, since the sponge offers shelter, additional substrate, and exposure to inhalant currents that may carry food and nutrients. This comes at an expense for the sponge, since it has to modify its typical morphology to accommodate the coral’s growth.

Population Genetic Structure, Abundance, and Health Status of Two Dominant Benthic Species in the Saba Bank National Park, Caribbean Netherlands: Montastraea cavernosa and Xestospongia muta.

Saba Bank, a submerged atoll in the Caribbean Sea with an area of 2,200 km2, has attained international conservation status due to the rich diversity of species that reside on the bank. In order to assess the role of Saba Bank as a potential reservoir of diversity for the surrounding reefs, we examined the population genetic structure, abundance and health status of two prominent benthic species, the coral Montastraea cavernosa and the sponge Xestospongia muta. Sequence data were collected from 34 colonies of M. cavernosa (nDNA ITS1-5.8S-ITS2; 892 bp) and 68 X. muta sponges (mtDNA I3-M11 partition of COI; 544 bp) on Saba Bank and around Saba Island, and compared with published data across the wider Caribbean. Our data indicate that there is genetic connectivity between populations on Saba Bank and the nearby Saba Island as well as multiple locations in the wider Caribbean, ranging in distance from 100s–1000s km. The genetic diversity of Saba Bank populations of M. cavernosa (π = 0.055) and X. muta (π = 0.0010) was comparable to those in other regions in the western Atlantic. Densities and health status were determined along 11 transects of 50 m2 along the south-eastern rim of Saba Bank. The densities of M. cavernosa (0.27 ind. m-2, 95% CI: 0.12–0.52) were average, while the densities of X. muta (0.09 ind. m-2, 95% CI: 0.02–0.32) were generally higher with respect to other Caribbean locations. No disease or bleaching was present in any of the specimens of the coral M. cavernosa, however, we did observe partial tissue loss (77.9% of samples) as well as overgrowth (48.1%), predominantly by cyanobacteria. In contrast, the majority of observed X. muta (83.5%) showed signs of presumed bleaching. The combined results of apparent gene flow among populations on Saba Bank and surrounding reefs, the high abundance and unique genetic diversity, indicate that Saba Bank could function as an important buffer for the region. Either as a natural source of larvae to replenish genetic diversity or as a storehouse of diversity that can be utilized if needed for restoration practices.

Selective feeding by the giant barrel sponge enhances foraging efficiency

AbstractForaging theory predicts the evolution of feeding behaviors that increase consumer fitness. Sponges were among the earliest metazoans on earth and developed a unique filter‐feeding mechanism that does not rely on a nervous system. Once thought indiscriminate, sponges are now known to selectively consume picoplankton, but it is unclear whether this confers any benefit. Additionally, sponges consume dissolved organic carbon (DOC) and detritus, but relative preferences for these resources are unknown. We quantified suspension feeding by the giant barrel sponge Xestospongia muta on Conch Reef, Florida, to examine relationships between diet choice, food resource availability, and foraging efficiency. Sponges consistently preferred cyanobacteria over other picoplankton, which were preferred over detritus and DOC; nevertheless, the sponge diet was mostly DOC (∼70%) and detritus (∼20%). Consistent with foraging theory, less‐preferred foods were discriminated against when relatively scarce, but were increasingly accepted as they became relatively more abundant. Food uptake was limited, likely by post‐capture constraints, yet selective foraging enabled sponges to increase nutritional gains.

Patterns of population structure and dispersal in the long-lived “redwood” of the coral reef, the giant barrel sponge (Xestospongia muta)

Sponges are one of the dominant fauna on Florida and Caribbean coral reefs, with species diversity often exceeding that of scleractinian corals. Despite the key role of sponges as structural components, habitat providers, and nutrient recyclers in reef ecosystems, their dispersal dynamics are little understood. We used ten microsatellite markers to study the population structure and dispersal patterns of a prominent reef species, the giant barrel sponge (Xestospongia muta), the long-lived “redwood” of the reef, throughout Florida and the Caribbean. F-statistics, exact tests of population differentiation, and Bayesian multi-locus genotype analyses revealed high levels of overall genetic partitioning (F ST = 0.12, P = 0.001) and grouped 363 individuals collected from the Bahamas, Honduras, US Virgin Islands, Key Largo (Florida), and the remainder of the Florida reef tract into at minimum five genetic clusters (K = 5). Exact tests, however, revealed further differentiation, grouping sponges sampled from five locations across the Florida reef tract (~250 km) into three populations, suggesting a total of six genetic populations across the eight locations sampled. Assignment tests showed dispersal over ecological timescales to be limited to relatively short distances, as the only migration detected among populations was within the Florida reef tract. Consequently, populations of this major coral reef benthic constituent appear largely self-recruiting. A combination of levels of genetic differentiation, genetic distance, and assignment tests support the important role of the Caribbean and Florida currents in shaping patterns of contemporary and historical gene flow in this widespread coral reef species.

Population dynamics of giant barrel sponges on Florida coral reefs

The structure of coral reef benthic communities has changed significantly in recent decades and will likely continue to change with the increasing frequency and scale of disturbances. Reef-building corals and macroalgae have been regularly included in assessments of coral reef communities, however very little is known about the long-term dynamics of sponge populations. The giant barrel sponge Xestospongia muta is a dominant component of Caribbean coral reef communities, and it was previously reported that populations significantly increased in the Florida Keys over 2000–2006. Using surveys of sponges from the same permanent plots on reefs off Key Largo, Florida, USA, this study extended the investigation of the population dynamics of X. muta for 2000–2012 at three depths (15, 20, 30m). Over 12years, the density of X. muta significantly increased by a mean of 122% (range=53–336%) on Conch Reef and by a mean of 44% on Pickles Reef. Both the cover and volume of X. muta concomitantly increased at all sites and increases in both metrics were greater over 2006–2012 relative to 2000–2006 due to decreased mortality of the largest sponges in the population over time. Population growth accelerated at all sites on Conch Reef due to a significant increase in recruitment and sponge survival, and was greater at deeper relative to shallow depths; on Pickles Reef, recruitment decreased, but survival increased and population growth remained constant over time. Despite mortality due to putative pathogenesis, and in contrast to the persistent decline of reef-building corals, these results suggest that conditions on Florida coral reefs have been increasingly favorable for the growth of barrel sponge populations. Given the long lifespan of X. muta, it remains to be seen whether these results represent a persistent change with broad geographic relevance, or stochastic variation in local demographics.

Trait-mediated ecosystem impacts: how morphology and size affect pumping rates of the Caribbean giant barrel sponge

Sponges are a dominant component of Caribbean coral reef suspension-feeding communi- ties. Understanding how pumping rates are affected by sponge size and morphology, as well as the en - vironment, is fundamental to understanding the ecological interactions that are mediated by sponge filtration. In a comprehensive in situ investigation of sponge pumping, the excurrent seawater velocities of 274 specimens of the largest Caribbean species, the giant barrel sponge Xestospongia muta, were measured at sites in the Bahamas and Florida Keys to investigate (1) the relationship between excurrent velocity distributions and sponge morphology, (2) the scaling relationship between pumping and sponge size, and (3) temporal variation of pumping and sensitivity to environmental changes. Excurrent velocity distributions across the osculum showed peak velocities at the center and diminishing veloci- ties near the edges of the osculum. The degree of center-weighting was explained by the distribution of sponge biomass relative to the spongocoel. Volu- metric pumping rates scaled isometrically with sponge size and averaged 0.06 ± 0.04 l s −1 l −1 sponge tissue, but were reduced for extremely large sponges. Pumping activity was relatively constant over short temporal scales, but varied over longer scales; how- ever, variations in pumping rates, in cluding periods of cessation, were asynchronous across the pop - ulation and uncorrelated with changes in environ- mental conditions. We estimate that populations of X. muta in the Florida Keys and Bahamas process a volume of water equivalent to a layer 1.7 to 12.9 m thick each day and overturn the water column every 2.3 to 18.0 d.

Antimalarial dipeptide from a Streptomyces sp. associate of the sponge Xestospongia muta

Antimalarial dipeptide from a Streptomyces sp. associate of the sponge Xestospongia muta

Nitrogen Biogeochemistry in the Caribbean Sponge, Xestospongia muta: A Source or Sink of Dissolved Inorganic Nitrogen?

BackgroundSponges have long been known to be ecologically important members of the benthic fauna on coral reefs. Recently, it has been shown that sponges are also important contributors to the nitrogen biogeochemistry of coral reefs. The studies that have been done show that most sponges are net sources of dissolved inorganic nitrogen (DIN; NH4 + and NO3 −) and that nitrification, mediated by their symbiotic prokaryotes, is the primary process involved in supplying DIN to adjacent reefs.Methodology/Principal FindingsA natural experiment was conducted with the Caribbean sponge Xestospongia muta from three different locations (Florida Keys, USA; Lee Stocking Island, Bahamas and Little Cayman, Cayman Islands). The DIN fluxes of sponges were studied using nutrient analysis, stable isotope ratios, and isotope tracer experiments. Results showed that the fluxes of DIN were variable between locations and that X. muta can be either a source or sink of DIN. Stable isotope values of sponge and symbiotic bacterial fractions indicate that the prokaryotic community is capable of taking up both NH4 + and NO3 − while the differences in δ 15N between the sponge and bacterial fractions from the NH4 + tracer experiment suggest that there is translocation of labeled N from the symbiotic bacteria to the host.Conclusions/SignificanceNitrogen cycling in X. muta appears to be more complex than previous studies have shown and our results suggest that anaerobic processes such as denitrification or anammox occur in these sponges in addition to aerobic nitrification. Furthermore, the metabolism of this sponge and its prokaryotic symbionts may have a significant impact on the nitrogen biogeochemistry on Caribbean coral reefs by releasing large amounts of DIN, including higher NH4 + concentrations that previously reported.

Chemical investigation of lipids of a marine sponge Spirastrella vagabunda

Sponges are among the simplest of multicellular animals and are often described as the most primitive of all. Study of sponge lipids is as important as other secondary metabolites and has been well documented in a series of extensive reviews by Berge and Barnathan, Rod kina, etc. [1, 2]. Regular research into lipids of sponges began in the 1970s [3] and continues till today because they have the greatest diversity of fatty acids, sterols etc. Studies on fatty acids and sterols as lipid components of sponges and other organisms have been elaborately taken up by a number of investigators [4, 5]. There are only a few investigations on this species, Spirastrella vagabunda. The aqueous extract of this species has shown high phospholipase A2 catalytic activity [6]. The bacteria isolated from this sponge produced acetylcholinesterase, an essential enzyme [7], but no investigation on the chemistry of this species has been done so far. This paper presents a study of the fatty acid profile and sterol composition of the total lipid of S. vagabunda for the first time (Table 1). A significant number of fatty acids were identified by GC-MS. The fatty acids were characterized by linear saturated fatty acids, monobranched saturated fatty acids, polybranched saturated fatty acid, monounsaturated fatty acids, and polyunsaturated fatty acids. The percentage of straight-chain fatty acids was 28.22% of the total fatty acids. Generally, among the saturated fatty acids, C16:0 and C18:0 dominated in most of the sponges. In the present investigation, the main saturated fatty acids are also C16:0 (6.37%) and C18:0 (5.77%). It is interesting that long-chain saturated fatty acids like C23:0, C24:0, C25:0, and C28:0 are present in good quantity in S. vagabunda. S. vagabunda contains the highest percentage of monomethyl branched fatty acids, i.e., 45.5% of the total fatty acid content, as in the marine sponge species Geodia gibberosa, which also contains 40–50% of branched fatty acids [8]. Among these branched fatty acids the amount of 11-methyloctadecanoic acid was significantly high, i.e., 13.31% of the total FA. A long-chain branched fatty acid, i.e., br-24-methylhexacosanoic acid, is also present in good quantity (8.97%). The identification of 11-methyl-18:0 and 24-methyl-26:0 (ante-iso) acids was finally confirmed by comparing their key mass fragments (11-methyl-18:0: m/z 312 M+, 269, 213, 185, 143; 24-methyl-26:0: m/z 424 M+, 381, 339, 199, 266, 143) obtained by GC-MS analysis with their literature data. The presence of saturated isoand ante-iso acids (branched fatty acids) is known to have a bacterial origin [9, 10]. So, the presence of symbiotic bacteria cannot be excluded. 3,7,11-Trimethyldodecanoic acid, a very rarely found polymethyl branched fatty acid, which was earlier identified from the marine sponge Xestospongia muta [11], was reported to be present in S. vagabunda, which is an important finding. The identification of 3,7,11-trimethyldodecanoic acid was confirmed by the key mass fragments at m/z 101 and at m/z 171, which indicate the methyl branching at 3 and 7 position [11]. Generally in various sponge species, the percentage of monoenes varies from 2% to 50% of the total FA content. But in the present investigation, only one monoenic acid C18:1 (2.42%) is identified. C18:1 (9) and C18:1 (11) are the principal isomers of C18 monoenes in sponges [2]. The GC-MS spectrum of the C18:1 showed important mass fragments at m/z 296 (M+), 264, 221, 180, 123, 109, and 96, and by comparing with the literature data, the monoenic acid is identified as C18:1 (9). The polyunsaturated FA of this species is represented by one diene and one trienoic acids with total content of 17.91%.

Bleaching of the giant barrel sponge Xestospongia muta in the Florida Keys

The giant barrel sponge Xestospongia muta is now the dominant habitat‐forming organism on many Caribbean coral reefs and has been observed to undergo cycles of bleaching similar to those seen for reef‐building corals. We examined bleaching of X. muta at 15‐m, 20‐m, and 30‐m depths over 2000–2005 on Conch Reef, Key Largo, Florida, to determine the spatial and temporal patterns of bleaching, whether bleaching affected sponge mortality, and whether there was a relationship between bleaching and seawater temperatures. Bleaching increased significantly with depth and was greater in autumn than spring, but the response was not uniform across the sponge population. Bleaching of X. muta did not result in sponge mortality, corroborating the conclusion that cyanobacterial symbionts of the sponge provide little or no benefit to the host. There was greater sponge bleaching with higher minimum daily seawater temperature anomalies within 30 d of surveys in the spring. For both the spring and autumn, there was greater bleaching with a higher number of positive 0.5°C daily anomalies within 14 d before surveys. Anomalously warm seawater temperatures fail to completely explain the variability of the observed bleaching response, however, and additional work would be required to conclusively determine whether a causal relationship between bleaching and temperature exists. As has been described for corals, bleaching of X. muta is likely a complex response that may be affected by multiple factors, including light availability and differences in bleaching susceptibility among Synechococcus symbionts.