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The genus Placospongia Gray, 1867 is a group of sponges widely distributed in the world. It currently has 11 valid species, where five of those, Placospongia caribica Rützler et al., 2014, P. cristata Boury-Esnault, 1973, P. intermedia Sollas, 1888, P. ruetzleri van Soest, 2017 and P. giseleae Mácola & Menegola, 2021, are distributed in the Central Western Atlantic. The Colombian Caribbean has the records of P. intermedia and P. ruetzleri. In this research, the taxonomy of the genus Placospongia in Colombia was reviewed, describing four species, two of which are new to science: P. colombiensis sp. nov. and P. soesti sp. nov.; and P. cristata is a new record for the Colombian Caribbean. Therefore, the number of species of the genus is expanded to 13 for the world, to eight for the Western Atlantic, and to five for Colombia, ranking it as the country with the most species of the genus for the Western Atlantic. Some of the misassigned records for Indo‒Pacific species are relocated to species present in the Caribbean. Finally, a taxonomic key is given to identify the species of the Caribbean Sea.

El incremento en la frecuencia e intensidad de eventos oceanicos extremos limita la capacidad de recuperacion de los ecosistemas, amenazando su subsistencia. Con el fin de entender la relacion entre la estructura y salud arrecifal y los eventos extremos ambientales, se analizaron series de datos ambientales de las islas del Rosario ( e.g ., temperatura del mar, caudal y/o salinidad, turbidez), en comparacion con cobertura coralina y signos de deterioro ( e.g ., blanqueamiento, enfermedades). En las series de tiempo de las variables ambientales se calcularon los eventos oceanicos que excedieron un umbral estadistico, estableciendo su intensidad, duracion y frecuencia. Para los atributos de la comunidad, se evaluaron dos estaciones del Sistema Nacional de Monitoreo de Arrecifes Coralinos en Colombia (SIMAC), en dos ventanas temporales (largo plazo, 1998–2013 y corto plazo, 2013 - 2014). Los eventos extremos de temperatura superficial del mar, el caudal de descarga continental y la turbidez asociada fueron las principales variables relacionadas con la reduccion de la cobertura coralina. El blanqueamiento masivo de 2005 y otros eventos posteriores dieron como resultado una reduccion de la cobertura coralina entre 2004 y 2010. En el corto plazo no se registraron fuertes eventos extremos ni cambios en las formaciones coralinas, si bien el estres termico y las reducciones de salinidad en la epoca de lluvias estuvieron asociados con un ligero blanqueamiento en noviembre de 2014. Aunque los signos de deterioro sean bajos, es importante considerarlos, ya que la sinergia entre perturbaciones continuas puede conllevar a una perdida de cobertura del coral. Effect of extreme oceanic events in the coral formations of Islas del Rosario, Colombian Caribbean The increase in frequency and intensity of extreme oceanic events limits the capacity of recovery of ecosystems, threatening their subsistence. Thus, in order to understand the relationship between coral health and extreme environmental events, data on sea temperature, runoff and / or salinity, turbidity were analyzed in the Islas del Rosario in comparison with coral cover, and coral signs of deterioration ( e.g ., bleaching, coral diseases). In the time series of environmental variables, oceanic events that exceeded a statistical threshold were calculated, establishing their intensity, duration and frequency. The attributes of the community were studied through observations in two stations of the National Coral Reef Monitoring System in Colombia (SIMAC), assessed in two time windows (long term, 1998-2013 and short term, 2013-2014). The extreme events of sea surface temperature, river discharge and associated turbidity, were the main variables related to the reduction of coral cover. The massive coral bleaching of 2005 and other subsequent events resulted in a reduction in coral coverage between 2004 and 2010. During the short-term observations there were no strong extreme events or changes in coral formations, although thermal stress and reductions in salinity in the rainy season were associated with a slight bleaching in November 2014. Although the signs of deterioration are low, it is important to consider them, since the synergy between continuous disturbances can lead to a loss of coral cover.

Esta investigacion busco determinar el papel de la herbivoria por parte del caracol Cittarium pica sobre el ensamblaje algal del litoral rocoso en el area de Santa Marta, Colombia. Se realizaron experimentos con jaulas en el mesolitoral superior entre diciembre de 2017 y junio de 2018, con tratamientos de inclusion ( C. pica ), exclusion (sin herbivoros) y controles (2 lados abiertos y sin jaula). La disminucion natural de las algas durante la epoca de lluvia se vio reforzada en abril, cuando se combinaron por varios dias mar calmo y mareas bajas al medio dia, produciendo altas temperaturas y desecacion que generaron mortandad masiva. Se observo una mayor cobertura de algas coralinas incrustantes en los tratamientos con C. pica , insinuando que las favorece el pastoreo, sobre ellas o sobre otros grupos de algas. En general, la herbivoria por C. pica no parecio controlar al ensamblaje algal. Esto podria deberse a que en la poblacion, actualmente dominan ejemplares de tallas pequenas como consecuencia de la sobreexplotacion, lo que los limita fisicamente para la ingesta de algas de mayor tamano y textura firme. Las algas fueron estimuladas principalmente por el afloramiento costero y controladas por factores ambientales, que a veces pueden ser extremos.

Slattery & Lesser (2015; Mar Ecol Prog Ser 527:275-279) offer a Comment on our review of the literature for evidence of bottom-up control of sponge communities on Caribbean reefs. We briefly address the criticisms presented in the Comment and reiterate the lack of evi- dence for food limitation, including inter-oceanic comparisons of Caribbean reefs with Indo- Pacific oligotrophic reefs, where sponge communities show strong evidence of food limitation, and past and recent evidence for the importance of dissolved organic carbon (DOC) in sponge nutri- tion. We did not claim that 'predation is the primary process that determines the growth, biomass and biodiversity of sponges on Caribbean coral reefs,' but we identified 3 depth-related factors that influence sponge community structure on Caribbean reefs: turbulence, spatial competition and predation. We agree that multifactorial manipulative experiments are the best way to address the interaction between top-down and bottom-up processes in this system; indeed, one such experiment has been performed, with an outcome that does not support bottom-up effects.

The diversity and biomass of sponges on Caribbean reefs exceeds that of all other benthic organisms. Wilkinson & Cheshire (1990; Mar Ecol Prog Ser 67:285�294) summarized evi- dence that sponge communities on Caribbean reefs were different from those on the Great Barrier Reef, Australia, reflecting food limitation of the latter, but not of the former. Since then, we have learned much about the ecology of sponges, and the concept of food limitation has recently re- emerged, seemingly without substantive reference to past inter-oceanic comparisons or pioneer- ing studies of sponge physiology. Here, we review the literature in an attempt to correct this digression. Based on current knowledge of sponge nutrition and bottom-up resource gradients (particulate food, dissolved organic carbon (DOC), light, turbulence), we predict 4 patterns of sponge abundance that would suggest food limitation on Caribbean reefs. After a critical review of survey data, correlative studies and manipulative experiments, we can find no evidence for food limitation. Although there is good evidence for higher availability of picoplankton at greater depths, sponge abundance does not mirror this gradient, suggesting that other sources of nutrition are also important, and particulate food is not a limiting factor. Recent studies have renewed inter- est in the uptake of DOC by both high and low microbial abundance sponge species, suggesting that the absence of bottom-up effects for sponges on Caribbean reefs may be attributable to this mysterious, and likely ubiquitous, food source. The recent unambiguous demonstration of top- down effects of predation on sponge community composition across the Caribbean may owe its clarity to the relative lack of confounding influences of abiotic and bottom-up effects in this study system.

Three new cases of sponge symbiosis between species of Plakortis and Xestospongia were found in reef caves and mesophotic reef habitats of the Caribbean. Plakortis sp. 1 from the Bahamas associates exclusively with Xestospongia deweerdtae which was originally described living freely on the deep fore-reef and caves of Jamaica. In addition, we found Plakortis sp. 2 from Puerto Rico which associates with both X. deweerdtae and a different Xestospongia sp. Sponge specimens were identified using cytochrome oxidase subunit 1, 28S rRNA and 18S rRNA gene sequence fragments, spicule analysis, and histological sections with SEM. Unlike previous sponge pairs, Xestospongia spp. not only grew as a thin veneer of tissue over the Plakortis host sponge but through the mesohyl, forming inner channels (0.1–1 cm) that may provide a benefit by facilitating more efficient water transport through the dense Plakortis tissue. Symbioses with both Plakortis spp. were documented from an early recruit stage through adulthood. Spicule measurements conducted on symbiotic versus free-living X. deweerdtae revealed significantly smaller spicule sizes for symbiotic individuals, suggesting a cost in terms of silicon availability, or a benefit in terms of a lower investment in skeleton synthesis for support. This study reveals new specialized symbiotic associations between distantly related sponge genera that likely represent an alternative strategy of adaptation for life in reef caves and mesophotic reefs.

Several groups of sponges are able to excavate galleries and tunnels in calcareous substrata such as limestone rock, shells, calcareous algae and coral skeletons. Within the genus Cliona, some species share the common traits of being brown to olive-green in color, and harboring photosynthetic, unicellular dinoflagellates (zooxanthellae). These Cliona spp. have been grouped as the Cliona viridis species complex. Several species of this complex completely encrust the excavated substratum with a thin veneer of tissue and, when colonizing dead exposed parts of live coral colonies, they are able to undermine or overgrow and thus kill live coral tissue as they advance predominantly laterally. In the course of our taxonomic and ecological studies of Caribbean brown to brown-black encrusting Cliona, we found an as yet undescribed species that stands out by having tylostyle megasclere spicules with narrow heads and lacking the usual microsclere spicule complement of spirasters. This species, named and described here Cliona acephala n. sp., has so far been found exclusively in the Santa Marta area, Caribbean coast of Colombia. Previous studies with ITS2 ribosomal DNA showed it to be genetically distinct from other Caribbean encrusting species belonging to the Cliona viridis species complex, vis. Cliona aprica, Cliona caribbaea, Cliona tenuis and Cliona varians, but making it genetically closer to Indo-Pacific Cliona orientalis. An intriguing possibility, to be addressed with further studies, is that C. acephala n. sp. may have been introduced to the Caribbean. However, until proved otherwise, we regard the material presently described as distinct.

The new discovery by Vicente et al. (2014) of specialized epizoic symbioses between sponges of the genera Plakortis and Xestospongia revealed the obligate interaction of two new Plakortis spp. associating with Xestospongia deweerdtae and a new Xestospongia sp. In this study we formally describe the two new Plakortis spp. as Plakortis deweerdtaephila sp. nov. (previously reported as Plakortis sp. 1), Plakortis symbiotica sp. nov. (previously reported as Plakortis sp. 2) and describe the new Xestospongia sp. epibiont as Haliclona ( Halichoclona ) plakophila sp. nov. Plakortis deweerdtaephila associates only with X. deweerdtae , and has very small to large straight diods (24.2–233.7 μm long) and triods (26.4–102.6 μm long) that form large ectosomal circular meshes (114–329 μm diameter). P. symbiotica associates with both X. deweerdtae and H. plakophila, has larger curved diods (71.9–141.8 μm long) and triods (20.4–70.6 μm long) that form smaller ectosomal circular meshes (43–121 μm diameter) than P. deweerdtaephila . Phylogenetic analysis of cox1 and cob gene fragments revealed a strongly supported clade that grouped both Plakortis spp. nov. distantly from any other known Plakortis spp. H. plakophila is described as a thin encrusting veneer of tissue with occasional papillae, so far only found associated with P. symbiotica in La Parguera, Puerto Rico. Phylogenetic analysis of 18S rRNA and cox1 gene fragments place it distantly from any known clade of Haplosclerida. We found a new associated morphotype of X. deweerdtae from Bocas del Toro Panama, which completely overgrew P. deweerdtaephila . In addition, free-living morphotypes from Panama produce larger S-shaped and round bracket shaped strongyles never before observed for this species, leading us to redescribe X. deweerdtae . All X. deweerdtae morphotypes shared >99% sequence homology of cox1 , 18S rRNA and 28S rRNA genes with the holotype of X. deweerdtae . This study highlights the highly variable morphological characters of X. deweerdtae influenced by lifestyle and environmental factors. This is also the first time that an obligate symbiosis with a heterospecific sponge is used as a key taxonomic character.

Species complexes – groups of closely related species in which intraspecific and interspecific variability overlap – have generated considerable interest and study. Frequently, members of a species complex do not have complete reproductive isolation; therefore, the complex may go through extensive gene flow. In the Caribbean Sea, some encrusting and excavating sponges of the genus Cliona (Porifera, Hadromerida, Clionaidae) are grouped within the great “ Cliona viridis ” complex because of their morphological similarities. This study examined the evolutionary relationships of the Caribbean members of this complex ( C. caribbaea , C. tenuis , C. aprica and C. varians ) and related taxa based on nuclear (ITS1 and ITS2) and mitochondrial (3′ end of ND6) DNA sequences. The intragenomic ITS variation and its secondary structures were evaluated using a mixed approach of Denaturing Gradient Gel Electrophoresis (DGGE), DNA sequencing and secondary structure prediction. Considerable intragenomic variation was found in all the species, with apparently functional ITS1 and ITS2 secondary structures. Despite the subtle but clear morphological differentiation in these excavating sponges, the intragenomic copies of C. caribbaea , C. tenuis and C. aprica had a polyphyletic placement in the ITS1 and ITS2 genealogies and very low divergence. Therefore, it is clear that these species constitute a species complex (herein called Ct -complex). Genetic distances within the Ct -complex revealed that an important part of the interspecific variation overlapped with intraspecific variation, suggesting either incomplete lineage sorting or extensive gene flow. In contrast, C. varians and an unidentified “ Pione ” species emerged as monophyletic clades, being the closest sister groups to the Ct -complex. Additionally, our results support that C. laticavicola and C. delitrix conform a monophyletic group, but absence of reciprocal monophyly in these species suggests they may be life stages or ecophenotypes of a single species or they have diverged recently. Our work showed that the 3′ end of the ND6 mitochondrial gene was highly conserved and not suitable for phylogenetic analysis at the interspecific level.

The parrotfish Sparisoma viride often grazes live coral from edges undermined by the Caribbean encrusting and excavating sponge Cliona tenuis. To test whether parrotfish biting action has an effect on the dynamics of the sponge– coral interaction, we manipulated access of parrotfishes to the sponge–coral border in two species of massive corals. When parrotfish had access to the border, C. tenuis advanced significantly more slowly into the coral Siderastrea siderea than into the coral Diploria strigosa. When fish bites were prevented, sponge spread into S. siderea was further slowed down but remained the same for D. strigosa. Additionally, a thinner layer of the outer coral skeleton was removed by bioerosion when fish were excluded, a condition more pronounced in D. strigosa than in S. siderea. Thus, the speed of sponge-spread and the extent of bioerosion by parrotfish was coral species-dependent. It is hypothesized that coral skeleton architecture is the main variable associated with such dependency. Cliona tenuis spread is slow when undermining live S. siderea owing to the coral’s compact skeleton. The coral’s smooth and hard surface promotes a wide and shallow parrotfish bite morphology, which allows the sponge to overgrow the denuded area and thus advance slightly faster. On the less compact skeleton of the brain coral, D. strigosa, sponge spread is more rapid. This coral’s rather uneven surface sustains narrower and deeper parrotfish bites which do not facilitate the already fast sponge progress. Parrotfish corallivory thus acts synergistically with C. tenuis to further harm corals whose skeletal architecture slows sponge lateral spread. In addition, C. tenuis also appears to mediate the predator–prey fish–coral interaction by attracting parrotfish biting.

The Caribbean sponge Cliona delitrix is among the strongest reef space competitors; it is able to overpower entire coral heads by undermining coral polyps. It has become abundant in reefs exposed to organic pollution, such as San Andres Island, Colombia, SW Caribbean. Forty-four sponge-colonized coral colonies were followed-up for 13 months to establish the circumstances and the speed at which this sponge advances laterally into live coral tissue and the coral tissue retreats. Cliona delitrix presence and abundance was recorded at seven stations to interpret current reef space and coral species colonization trends. The spread of C. delitrix on a coral colony was preceded by a band of dead coral a few millimeters to several centimeters wide. However, the sponge was directly responsible for coral death only when live coral tissue was within about 2 cm distance; coral death became sponge advance-independent at greater distances, being indirectly dependent on other conditions that tend to accelerate its retreat. Cliona delitrix advanced fastest into recently killed clean coral calices; however, sponge spread slowed down when these became colonized by algae. The lateral advance of C. delitrix was slower than other Cliona spp. encrusting excavating sponges, probably owing to the greater depth of its excavation into the substratum. Cliona delitrix prefers elevated portions of massive corals, apparently settling on recently dead areas. It currently inhabits 6–9% of colonies in reefs bordering San Andres. It was found more frequently in Siderastrea siderea (the most abundant local massive coral), which is apparently more susceptible to tissue mortality than other corals. Current massive coral mortality caused by C. delitrix could initially change the relative proportions of coral species and in the long-term favor foliose and branching corals.

The fatty acid composition of whole phospholipids from marine sponges collected from the Colombian Caribbean Sea was determined as part of our studies on the order Halichondrida: Halichondria magniconulosa , Halichondria lutea, Petromica ciocalyptoides, Axinyssa ambrosia, Didiscus oxeata and Dragmaxia undata . Structure elucidation was accomplished by means of gas chromatography retention parameters and GCMS. Eight new fatty acids were identified by their methyl esters and N-acylpyrrolidide derivatives (i.e. 5-methyl-6-octadecenoic, 16-methyl-11-heptadecenoic, 8-methyl-4-tetracosenoic, 8,17-dimethyl-5-octadecenoic, 23-methyl-8-tetracosenoic, 20-methyl-18-tetracosenoic, 4,17-tetracosadienoic and 22,27-dimethyl-5,9-octacosadienoic acids). These findings establish alternative fatty acid biosynthetic possibilities for these organisms.

The Caribbean encrusting and excavating sponge Cliona tenuis successfully competes for space with reef corals by undermining, killing, and displacing live coral tissue at rates of up to 20 cm per year. The crude extract from this sponge, along with the more polar partitions, kills coral tissue and lowers the photosynthetic potential of coral zooxanthellae. We used a bioassay-guided fractionation of the extract to identify the compound(s) responsible. The crude extract, the aqueous partition, and compound 1, herein named clionapyrrolidine A [(-)-(5S)-2-imino-1-methylpyrrolidine-5-carboxylic acid], when incorporated into gels at close to natural volumetric concentrations, killed coral tissue when brought into forced contact with live coral for periods of 1-4 days. This is the first report of a pure chemical produced by a sponge that kills coral tissue upon direct contact. The results are consistent with the localized coral death that occurs when C. tenuis-colonized coral fragments are thrown forcibly against live coral during storms. However, healed C. tenuis fragments placed directly onto live coral were killed readily by coral defenses, and fragments placed in close proximity to coral did not have any effect on the adjacent coral tissue. Solutions of clionapyrrolidine A in sea water were only slightly toxic against live coral. Hence, the coral death naturally brought about by C. tenuis when undermining live coral does not occur through external release of allelochemicals; below-polyp mechanisms must be explored further. N-acetylhomoagmatine (2), originally isolated from Cliona celata from the Northeastern Atlantic, was also assayed for comparison purposes because of its structural similarity to siphonodictidine, a toxic compound produced by a coral excavating sponge of the genus Aka. The lack of activity of N-acetylhomoagmatine at close to natural concentrations seems to indicate that the guanidine moiety, which is also present in siphonodictidine, is not a sufficiently strong structural motif for activity against corals.

Encrusting and excavating Caribbean sponges Cliona aprica, C. caribbaea and C. tenuis (Hadromerida: Clionaidae) aggressively undermine and displace live coral tissue. To estab- lish modes and rates of lateral advance into neighboring organisms, 171 sponge individuals were studied for 13 mo. Sponge advancement into live coral, via excavation underneath boundary polyps, occurred only when the 2 confronted at an angle of ≥180°. Sponges stopped or retreated when coral upward and inward growth at the boundary closed the angle between the coral and sponge, placing polyps out of reach of excavating tissue. At a straight angle of confrontation, C. tenuis advanced into coral at higher rates than the other 2 sponge species. Its advance was more pronounced into Diploria strigosa than into Siderastrea siderea. Sponge undermining continuously opened space for transient settlement of turf algae and for accumulation of sediments. Corallivory at the sponge-coral boundary did not imply greater rates of sponge advance, but probably did contribute to coral bioerosion. Mas- sive corals escaped sponge undermining by upward growth, their ability to do so depended partly on defensive mechanisms. Foliose and platy corals escaped by overtopping. Rates of sponge advance into substrata incrusted and overgrown by algae were in general lower than into live coral, while sponges lost space to some encrusting invertebrates.

Some sponges of the genus Cliona (Porifera, Hadromerida, Clionidae) simulta- neously excavate and encrust calcareous substratum, competing aggressively for illuminated space with corals and other organisms. To interpret current trends of reef space occupation, the patterns of distribution and size of three Caribbean species were examined at San Andres Island and Islas del Rosario in Colombia. While Cliona aprica was ubiquitous, C. caribbaea (¼ C. langae) preferred deep and protected reef zones, and C. tenuis shallow and wave-exposed settings. In contrast to the effect on other excavating sponges, chronic exposure to raw sew- age did not significantly increase the abundance of the studied sponges. Substra- tum occupation/availability ratios showed a positive tendency of the sponges toward certain coral skeletons, and a negative or neutral tendency toward calcar- eous rock, indicating that establishment may be easier on clean, recently dead coral than on older, heavily incrusted substratum. High relief generally limits sponge size to that of the illuminated portions of the substratum. A generally lower proportion of small individuals than of larger ones indicates currently low recruitment rates and low subsequent mortality. Successful events of higher recruitment seem to have occurred for C. tenuis. These are related to the massive acroporid coral die-off in the early 1980s and to asexual dispersion during storms, resulting in a current 10% substratum cover. Reefs with high coral mor- tality were and/or are thus more susceptible to colonization and subsequent space occupation by these sponges, although relief may prevent space monopolization.

Para evaluar el papel del sedimento sobre la alta produccion primaria de una laguna costera tropical, Cienaga Grande de Santa Marta (Caribe, Colombia), se midio el flujo de nitrogeno y fosforo (inorganico disuelto, particulado) en la interfase agua-sedimento. Entre 1996 y 1997 se incubaron nucleos de sedimento en el laboratorio y se ubicaron trampas de particulas en campo, en dos estaciones contrastadas por la influencia de aguas dulces y marinas. Los flujos tuvieron una alta variabilidad espacial y temporal pero no mostraron esquemas claros en su direccion e intensidad en relacion con las caracteristicas de los sedimentos o de la columna de agua de las dos estaciones. Esto evidencia una alta heterogeneidad en la naturaleza y actividad de los organismos responsables de los procesos biogeoquimicos. Los sedimentos liberaron en promedio al agua 1643 μmolNm -2 d -1 de amonio y 1.3 μmolNm -2 d -1 de nitrito, aportando a la columna el 1.90-3.41 % de lo requerido en la produccion. En condiciones oxicas normales, el sedimento actuo como sifon del fosforo, absorbiendo en promedio 178 μmolPm -2 d -1 disueltos y recibiendo 36277 μmolPm -2 d -1 particulados. Pero el fosforo se mantiene en exceso en la columna, en parte, por liberacion desde el sedimento en condiciones anoxicas durante florecimientos microalgales masivos. Flux of nitrogen and phosphorus at the water-sediment boundary in a tropical coastal lagoon (Cienaga Grande de Santa Marta, Colombian Caribbean) To evaluate the role of the sediment in the high primary production of a tropical coastal lagoon, "Cienaga Grande de Santa Marta" (Caribbean, Colombia), the flux of nitrogen and phosphorous (dissolved, inorganic, particulate) in the water-sediment boundary was measured. From 1996 to 1997 sediment cores were incubated in the laboratory and sediment traps were deployed in the field, in two sites contrasted by the influence of fresh and marine waters. The fluxes were spatially and temporally highly variable but did not show clear patterns in their direction and intensity in relation to the sediment or water column characteristics at the two sites. This evidences a high heterogeneity in the nature and activity of the organisms responsible of the biogeochemical processes. The sediments liberated to the water on average 1643 μmolNm -2 d -1 of ammonium and 1.3 μmolNm -2 d -1 of nitrite, offering 1.90-3.41 % of the amount required in production. In normal oxic conditions, the sediment acted as a phosphorous sink, absorbing on average 178 μmolPm -2 d -1 dissolved and receiving 36277 μmolPm-2d-1 particulate. But the phosphorous is maintained in excess in the column, in part, due to its liberation from the sediment in anoxic conditions during massive algal blooms.

To analyze and extract phylogenetic information from chemical characters, the 3b-hydroxysterol composition of 12 sponge species of various families of the Poriferan order Halichondrida (sensu lato), was determined. The current definition of the order is ambiguous, and its classification remains in a state of flux and hence, further chemical characters may aid in stabilizing it. Axinella corrugata, Pseudaxinella reticulata, P. explicata, Ptilocaulis walpersi, Dragmaxia undata (family Axinellidae), Myrmekioderma rea, M. gyroderma(family Desmoxyidae), Scopalina ruetzleri (family Dictyonellidae), Halichondria lutea, H. magniconulosa, Topsentia ophiraphidites and Petromica ciocalyptoides (family Halichondriidae) were collected in the Santa Marta area, Colombian Caribbean. Cladistic principles were used to advance a hypothesis of genealogical relationship among the studied species and to contrast current classifications at various taxonomic ranks. Sterol identity and various sterol properties (number of carbons, nuclei type, saturations and substitutions of the lateral chain) were coded as discrete characters according to their relative abundance in 4% ranges, for each of the studied species, and for an out group of 41 species of nine orders whose sterol fractions had been published. Of more than 300 codified characters, 74 constituted unique evolutionary novelties within the studied in group. Fifty-one of these characters (including 15 sterols) uniquely defined six species. Twelve sets of novel characters were shared exclusively by two or more species of the studied group and were thus informative in a phylogenetic sense. The cladogram, built by hand, had seven characters that were compatible with each other and were shared by two or more species (i.e. synapomorphies) and five that were incompatible with two or more. However

Caribbean sponges of the genus Ircinia contain high concentrations of linear furanosesterterpene tetronic acids (FTAs) and produce and exude low-molecular-weight volatile compounds (e.g., dimethyl sulfide, methyl isocyanide, methyl isothiocyanate) that give these sponges their characteristic unpleasant garlic odor. It has recently been suggested that FTAs are unlikely to function as antipredatory chemical defenses, and this function may instead be attributed to bioactive volatiles. We tested crude organic extracts and purified fractions isolated from Ircinia campana, I. felix, and I. strobilina at naturally occurring concentrations in laboratory and field feeding assays to determine their palatability to generalist fish predators. We also used a qualitative technique to test the crude volatile fraction from I. felix and I. strobilina and dimethylsulfide in laboratory feeding assays. Crude organic extracts of all three species deterred feeding of fishes in both aquarium and field experiments. Bioassay-directed fractionation resulted in the isolation of the FTA fraction as the sole active fraction of the nonvolatile crude extract for each species, and further assays of subfractions suggested that feeding deterrent activity is shared by the FTAs. FTAs deterred fish feeding in aquarium assays at concentrations as low as 0.5 mg/ml (fraction B, variabilin), while the natural concentrations of combined FTA fractions were >5.0 mg/ml for all three species. In contrast, natural mixtures of volatiles transferred from sponge tissue to food pellets and pure dimethylsulfide incorporated into food pellets were readily eaten by fish in aquarium assays. Although FTAs may play other ecological roles in Ircinia spp., these compounds are effective as defenses against potential predatory fishes. Volatile compounds may serve other defensive functions (e.g., antimicrobial, antifouling) but do not appear to provide a defense against fish predators.

On Caribbean reefs, the excavating sponge Cliona tenuis opportunistically colonized dead skeletons of the elkhorn coral Acropora palmata after its massive die-off in the 1980s. Further C. tenuis population increase occurred by colonization of other coral species, causing coral tissue death through undermining of live tissue and lateral growth. To follow up on a previous (2001) characterization of the abundance and size structure of C. tenuis at Islas del Rosario (Colombia), these factors were again estimated in 2014, along with its substratum utilization. The fate of sponge individuals colonizing massive coral colonies marked in 2001–2004 was also followed. By 2014 C. tenuis was still disproportionally occupying dead A. palmata branches, but its abundance and density, and the cover of other benthic elements, had not significantly changed over the 13-year period, suggesting that a stasis has been reached. Cliona tenuis was thus initially favored in the 1980s, but substratum monopolization did not occur. From 2001 to 2014, small individuals increased in number and very large ones decreased, suggesting not only that new recruitment is occurring, but also that larger sponges are shrinking or fragmenting. Marked sponges continued killing corals over the first few years, but over longer times they retreated or died, allowing corals to resume upward growth. However, it could not be ascertained whether the sponge retreat was age-related or the result of some environmental effect. The apparent preference for recently dead clean coral by larvae of C. tenuis and its current dynamics of recruitment, growth, fragmentation and mortality have stabilized its space occupation at Islas del Rosario.

Sterol compositions of the cold water ophiuroids Ophioplocus januarii and Ophionotus victoriae and of the tropical ophiuroids Ophiocoma echinata and Ophiocoma wendtii are reported. The four sterol mixtures contain Δ 5 mono- and di-unsaturated common 3β-hydroxy-sterols. Ophioplocus januarii and O. victoriae contain 24-methylcholesta-5,24(28)-dien-3β-ol and 24ζ-ethylcholesta-5,24(28)-dien-3β-ol in higher abundance than in O. echinata . These sterols were not found in O. wendtii . An interesting finding is the presence of Δ 5,24(28) -24- n -propylidenecholesterol in 7.6% in Ophionotus victoriae .

Sexual reproduction of the reef-building coral Montastrea cavernosa was studied in the Santa Marta area, Caribbean coast of Colombia, from October 1990 to October 1991. The area is subjected to a seasonal upwelling-outwelling regime. From microscopical analysis of tissue sections sampled each lunar month around the full moon, it was confirmed that this is a gonochoric, broadcasting species, with a single game- togenic cycle per year, and a 1:1 sex ratio. Oogenesis began a few weeks after spawning, and extended for 11 mo. The onset of spermatogenesis occurred just be- fore the full moon of June, later than at other localities where sea-water temperatures during the first half of the year are not as low. The amount of reproductive tissue strongly increased in both sexes after July, in association with an increase in sea-water temperature and a decrease in photoperiod. The gonad index of fully mature female colonies was about four times lower than at other lo- calities, perhaps due to the stressful seasonal regime. The male gonad index was lower than that of the female, indicating sex-related dierences in the rates of biomass allocation to reproduction. As in other Caribbean lo- calities, spawning occurred after the full moons of Au- gust and September. However, there was some evidence of a third spawning episode after the full moon of Oc- tober, possibly associated with a delay in the occurrence of maximum sea-water temperatures in near-equatorial localities compared to higher latitudes. The probability of cross-fertilization in this species with a gonochoric breeding system and a broadcasting mode of re- production is favored by its balanced sex ratio, its usually high within-reef zone abundance, and by local- ized and repeated spawning episodes, synchronized by lunar phase.

Although there is a long history of taxonomic investigation in Caribbean sponges, there are still many undescribed species. Furthermore, field observations and corroborating morphological analyses are revealing that what was believed to be single, somewhat variable species, may consist of two or more species, often easier to distinguish once well characterized. This is the case for Dragmacidon reticulatum (Ridley & Dendy, 1886) (Porifera, Demospongiae, Axinellida, Axinellidae), a rather well-known sponge, with an ample distribution and presence in rocky and reef environments of the tropical and subtropical Western Atlantic, with local records in the majority of the countries of the area, from Bermuda to Brazil. Field observations and a detailed review of material from different areas, including some type specimens, led us to the distinction of two different species in terms of external morphology, size of spicules, and skeletal architecture. The distinction was confirmed in the Bahamas and Santa Marta, Colombia, where the two species coexist. One of the species is Dragmacidon reticulatum sensu stricto, but for the other there is need to erect a new name, for which we propose Dragmacidon alvarezae n. sp. The purpose of the present work is to describe, illustrate and compare these two species.

Recruitment of demosponges (Porifera, Demospongiae) was monitored bimonthly for one year (March 1987 – March 1988) on acrylic plates, and compared to cover of adults, in six rocky and coral reef habitats at Santa Marta, Colombian Caribbean, an area subjected to seasonal, upwelling-outwelling regimes. According to suggestive but not significant trends, recruitment rates are more positively influenced by the total sponge cover near groups of plates than by cover at a larger (habitat) scale; recruit mortality is lower where recruitment is higher. These findings are in agreement with a model of higher settlement (probably due to short-distance dispersal) and lower postsettlement mortality within a few meters of adult sponges. Recruitment varied seasonally, being relatively high from May to November-December during the rainy, outwelling season, when seawater temperature was warmer, water turbidity higher, and benthic algal density lower; it was very low from January to April during the dry, upwelling season.

Phylogenetic relationships of symbiotic dinoflagellate lineages, distributed in all tropical and subtropical seas, suggest strategies for long distance dispersal but at the same time strong host specialization. Zooxanthellae (Symbiodinium: Dinophyta), which are associated to diverse shallow-water cnidarians, also engage in symbioses with some sponge species of the genus Cliona. In the Caribbean, zooxanthellae-bearing Cliona has recently become abundant due to global warming, overfishing, and algae abundance. Using molecular techniques, the symbionts from five excavating species (Cliona caribbaea, C. tenuis, C. varians, C. aprica and C. laticavicola) from the southern and southwestern Caribbean were surveyed. Several DNA sequence regions were used in order to confirm zooxanthellae identity; 18S rDNA, domain V of chloroplast large subunit (cp23S), internal transcribed spacer 2 (ITS2), and ITS2 secondary structure. Sequence analyses corroborated the presence of three zooxanthellae clades: A, B, and G. Presence of clades A and B in common boring sponges of the Caribbean fit with the general pattern of the province. The discovery of clade G for the first time in any organism of the Atlantic Ocean leads us to consider this unusual finding as a phylogenetic relict through common ancestors of sponge clades or an invasion of the sponge from the Indo-Pacific.

18S ribosomal DNA and internal transcribed spacer 2 (ITS-2) full-length sequences, each of which was sequenced three times, were used to construct phylogenetic trees with alignments based on secondary structures, in order to elucidate genealogical relationships within the Aplysinidae (Verongida). The first poriferan ITS-2 secondary structures are reported. Altogether 11 Aplysina sponges and 3 additional sponges (Verongula gigantea, Aiolochroia crassa, Smenospongia aurea) from tropical and subtropical oceans were analyzed. Based on these molecular studies, S. aurea, which is currently affiliated with the Dictyoceratida, should be reclassified to the Verongida. Aplysina appears as monophyletic. A soft form of Aplysina lacunosa was separated from other Aplysina and stands at a basal position in both 18S and ITS-2 trees. Based on ITS-2 sequence information, the Aplysina sponges could be distinguished into a single Caribbean–Eastern Pacific cluster and a Mediterranean cluster. The species concept for Aplysina sponges as well as a phylogenetic history with a possibly Tethyan origin is discussed.

Thinly encrusting sponges are diverse and ecologically important, but their taxonomy is challenging. In the Greater Caribbean, the recognition of species of Clathria (Thalysias), most of which are encrusting, is still problematic. Here we describe and clarify the taxonomy of eight species, three new to science, from material collected mostly in Colombia. These are C. (T.) virgultosa, C. (T.) curacaoensis, C. (T.) venosa, C. (T.) minuta, C. (T.) oxeota, C. (T.) sulfocleistochela n. sp., C. (T.) chelosigmoidea n. sp., and C. (T.) opalina n. sp. Underwater color photographs are provided, together with drawings of spicules and skeleton, and SEM images of spicules. Two other well-established Caribbean species of the subgenus, vis. C. (T.) isodictyoides and C. (T.) collosclera (both from Curacao) were not found in the studied material. A key for their identification is provided. Three more records, C. (T.) fascicularis Topsent, 1889, C. (T.) procera (Ridley, 1884) and C. (T.) basiarenacea (Boury-Esnault, 1973) are outlined for further study.

The genus Agelas comprises a group of tropical and subtropical reef sponges that contains large, long-lived, often brightly colored and conspicuous species, distributed throughout the tropica l western Atlantic, temperate northern At lantic (Mediterranean Sea), and western and central Indo-Pacific Realms. Among tropical sponge genera, Agelas is one with similar species richness in the Greater Caribbean in comparison to the Indo Pacific. The presence of verticillated acanthostyle spicules and a fibroreticulate skeleton of spongin fibres cored and/or echinated by spicules characterize this group. Taxonomic identification relies on a combination of characters, where external morphology and color play a key role, owing to the paucity of microscopical characters. Thus, there is still a great deal of taxonomic confusion, even for the more common species. We carried out a detailed revision of Agelas species throughout the Greater Caribbean area using classic taxonomic tools. Samples a nd observations covered Colombia, Belize, Jamaica, the Ba hamas, Barbados, Curacao and Venezuela, and included type material from major museum collections. According to our results, the genus Agelas in the Caribbean has at least thirteen valid species, viz. Agelas sceptrum (Lamarck, 1815); A. dispar Duchassaing & Michelotti, 1864; A. dilatata Duchassaing & Michelotti, 1864; A. clathrodes (Schmidt, 1870); A. cervicornis (Schmidt, 1870); A. conifera (Schmidt, 1870); A. schmidti Wilson, 1902; A. tubulata Lehnert & van Soest, 1996; A . wiedenmayeri Alcolado, 1984; A. citrina Gotera & Alcolado, 1987; A. sventres Lehnert & van Soest, 1996; A. repens Lehnert & van Soest, 1998; and A. cerebrum Assmann et al ., 2001. We found that variation of microscopic characteristics like skeleton arrangement, number of verticills and their spines, and spicule length and width, can be used as taxonomic tools, but only in a thorough comparison with other species in the same sub-regional context. Thus, a certain degree of familiarity with the genus’ regional variation is often required. The richness and distribution of these species in the Caribbean area show north/south differences and other ecological patterns are evident.

The volatile constituents of the marine sponge Ircinia felix were obtained by dynamic headspace extraction and analyzed by HRGC, HRGC-MS and HRGC-Odor at sniffing port. Fifty-nine volatiles were identified for the first time in the odor of this sponge. Hydrocarbons (32.9%), alcohols (17.8%) and carbonyl compounds (16.0%) predominated in the sponge volatile profile, followed by esters (11.6%), halogen compounds (8.6%), ethers (7.7%), nitrogen and/or sulfur compounds (4.6%) and carboxylic acids (0.8%). Among the identified volatiles, thiobismethane (commonly known as dimethylsulfide), methyl isocyanide and methyl isothiocyanate were found to be responsible for the nauseating and toxic smell emitted by the sponge and for the antimicrobial activity detected in the volatile extract. Exudation experiments in aquarium and in situ conditions revealed that thiobismethane, methyl isocyanide and methyl isothiocyanate are continuously released by the sponge. Upon injury, the concentration of these volatiles increased strongly. Hence, these substances form a chemical protective barrier which may help these sponges avoid fouling, compete for space, prevent infection in the short term, and/or signal generalist predators regarding the existence of other toxic substances in the internal tissues.

Direct field observations often reveal distinct morphotypes within sponge species that had been described on the basis of preserved material from different locations. The genus Axinyssa von Lendefeld, 1897 was revised for the Caribbean by Diaz et al . (1993), defining a single species, Axinyssa ambrosia (de Laubenfels, 1936), with several junior synonyms, some of which varied in the predominant spicule complement. At Santa Marta, Colombia, we found two morphotypes of Axinyssa living sympatrically, with consistent differences in morphology and spiculation. Revision of types and part of Diaz et al . (1993) material confirmed these differences, leading to the distinction of two species whose valid names are Axinyssa ambrosia and Axinyssa yumae (Pulitzer-Finali, 1986). The purpose of this note is to redescribe these two species.