Evaluation of in vitro treatments against the causative agent of Diadema antillarum scuticociliatosis (DaSc).

In the 1980s, a mass die-off of the long-spined sea urchin Diadema antillarum occurred on Florida and Caribbean coral reefs. D. antillarum populations largely did not recover, and in 2022, remaining populations experienced another mass mortality event. A ciliate most similar to Philaster apodigitiformis was identified as the causative agent of the 2022 event, which was named D. antillarum scuticociliatosis (DaSc). Here, we investigated possible treatments for this pathogen. We tested the efficacy of 10 compounds at final concentrations of 100, 50, 25, 12.5, 6.25, and 3.13 µM, or a 10-fold serial dilution series, against ciliates cultured from an infected D. antillarum specimen. Of the tested compounds, 8 induced 100% ciliate mortality at some dose after 24 h. The most effective (defined as those requiring the lowest dose to induce 100% ciliate mortality) were quinacrine and tomatine (both effective at 12.5 µM), followed by furaltadone and plumbagin (25 µM), bithionol sulfoxide and 2'4' dihydroxychalcone (50 µM), and oxyclozanide and carnidazole (100 µM). Toltrazuril and a commercially available anticiliate product containing naphthoquinones were not effective at any dose tested. Shortened (15 min) time trials were performed using ciliate cultures reared in natural seawater to better reflect natural environmental conditions, and revealed that 2 of the compounds (quinacrine and tomatine) induced 100% ciliate mortality at 100 µM, with tomatine also effective at 50 µM. This study identified several treatments effective against the causative agent of DaSc in vitro, but their toxicity and utility in vivo remain unknown.

Seventeen-year study reveals fluctuations in key ecological indicators on two reef crests in Cuba.

Reef crests in the Caribbean have lost approximately 80% of the foundational habitat-forming coral Acropora palmata (Lamarck, 1816), with declines registered as early as the 1950s mainly from anthropogenic causes. We studied two reef crests in the northwestern region of Cuba over 17 years (2005 to 2021) to evaluate temporal changes in coral cover, dominated by A. palmata, and their potential drivers. The density of A. palmata generally showed a negative trend at both reefs, with the lowest density recorded in 2021 at 0.2 ± 0.05 col. m-2 at Playa Baracoa and 1.0 ± 0.1 col. m-2 at Rincon de Guanabo. The mean size of the colonies in the two reefs also decreased over time. In Playa Baracoa, the mean diameter of A. palmata colonies decreased from 2012 at 67 ± 5.9 cm to 2013 at 34 ± 2.2 cm, whereas in Rincon de Guanabo, a change in diameter was evident from 2015 at 44.3 ± 2.3 to 2021 at 21.6 ± 0.9 cm. Adult colonies (10 cm-50 cm diameter) predominated in most years on both reefs. The populations of A. palmata on both reefs were healthy, with an average of 70% colonies in good condition during the study period. However, A. palmata cover decreased by almost half by 2021, to 8.6% in Playa Baracoa and 16.8% in Rincon de Guanabo. By contrast, macroalgal cover increased two-fold to 87.1% in Playa Baracoa and four-fold to 77.2% in Rincon de Guanabo. The density of the sea urchin Diadema antillarum was higher in Playa Baracoa than in Rincon de Guanabo. The highest densities were 2.8 ± 0.2 ind. m-2 in Playa Baracoa in 2005 and 0.1 ± 0.03 ind. m-2 in Rincon de Guanabo in 2008. Although our results show an overall decline of A. palmata (density and percent cover) and an increase in macroalgae, these two reef crests are in better condition than most reefs in the Caribbean in terms of the density and health of A. palmata populations, and the density of D. antillarum at Playa Baracoa. Our results are important in establishing a management plan to ensure the condition of these reef crests does not degrade further.

Uneven demographic consequences of the 2022 disease outbreak for the sea urchin Diadema antillarum in Puerto Rico.

Pervasive epizootic events have had a significant impact on marine invertebrates throughout the Caribbean, leading to severe population declines and consequential ecological implications. One such event was the regional collapse of herbivory, partly caused by the Diadema antillarum mortality event in 1983-84, resulting in a trophic cascade and altering the structure of reef communities. Consequently, there was a notable decrease in coral recruitment and an increase in the coverage of macroalgae. Nearly four decades later, in early 2022, the Caribbean basin experienced another widespread mass mortality event, further reducing the populations of D. antillarum. To assess the effects of this recent mortality event on the current demographics of D. antillarum, we surveyed eight populations along the eastern, northeastern, northern, and northwestern coast of Puerto Rico from May to July 2022, estimating their population density, size distribution, and disease prevalence. Additionally, the study compared these population parameters with data from four sites previously surveyed in 2012 and 2017 to understand the impact of the recent mortality event. The survey conducted in 2022 showed varying population densities at the surveyed reefs. Some populations exhibited mean densities of nearly one individual per square meter, while others had extremely low or no living individuals per square meter. The four populations with the highest density showed no evidence of disease, whereas the four populations with the lowest D. antillarum densities exhibited moderate to high disease prevalence. However, when considering all sites, the estimated disease prevalence remained below 5%. Nevertheless, the comparison with data from 2012 and 2017 indicated that the recent mortality event had a negative impact on D. antillarum demographics at multiple sites, as the densities in 2022 were reduced by 60.19% compared to those from the previous years. However, it is still too early to determine the severity of this new mortality event compared to the 1983-84 mortality event. Therefore, it is imperative to continue monitoring these populations.

Comparison of feeding preferences of herbivorous fishes and the sea urchin Diadema antillarum in Little Cayman.

On Caribbean coral reefs, losses of two key groups of grazers, herbivorous fishes and Diadema antillarum, coincided with dramatic increases in macroalgae, which have contributed to decreases in the resilience of these coral reefs and continued low coral cover. In some locations, herbivorous reef fishes and D. antillarum populations have begun to recover, and reductions in macroalgal cover and abundance have followed. Harder to determine, and perhaps more important, are the combined grazing effects of herbivorous fishes and D. antillarum on the structure of macroalgal communities. Surprisingly few studies have examined the feeding preferences of D. antillarum for different macroalgal species, and there have been even fewer comparative studies between these different herbivore types. Accordingly, a series of in-situ and ex-situ feeding assays involving herbivorous fishes and D. antillarum were used to examine feeding preferences. Ten macrophytes representing palatable and chemically and/or structurally defended species were used in these assays, including nine macroalgae, and one seagrass. All species were eaten by at least one of the herbivores tested, although consumption varied greatly. All herbivores consumed significant portions of two red algae species while avoiding Halimeda tuna, which has both chemical and structural defenses. Herbivorous fishes mostly avoided chemically defended species while D. antillarum consumed less of the structurally defended algae. These results suggest complementarity and redundancy in feeding by these different types of herbivores indicating the most effective macroalgal control and subsequent restoration of degraded coral reefs may depend on the recovery of both herbivorous fishes and D. antillarum.

Lack of recovery of the long-spined sea urchin Diadema antillarum Philippi in Puerto Rico 33 years after the Caribbean-wide mass mortality.

Caribbean populations of the long-spined black sea urchin Diadema antillarum Philippi were decimated by a disease-induced mass mortality in the early 1980's. The present study provides an updated status of the D. antillarum recovery and population characteristics in La Parguera Natural Reserve, Puerto Rico. The last detailed study to assess population recovery in 2001, indicated a slow, and modest recovery, albeit densities remained far below pre-mass mortality levels. Population densities were assessed along three depth intervals in six reef localities and one depth in three lagoonal sea-grass mounds using ten 20 m2 (10 × 2 m) belt-transects at each depth interval. Most of these were previously surveyed in 2001. All individuals encountered along the belt transects were sized in situ with calipers and rulers to characterize the size (age) structure of each population and get insight into the urchin's population dynamics and differences across localities in the area. Habitat complexity (rugosity) was assessed in all depth intervals. No significant differences in population densities between reef zones (inner shelf and mid-shelf) were observed, but significantly higher densities were found on shallow habitats (<5 m depth; 2.56 ± 1.6 ind/m2) compared to intermediate (7-12 m; 0.47 ± 0.8 ind/m2) and deep (>12 m; 0.04 ± 0.08 ind/m2) reef habitats in almost all sites surveyed. Habitat complexity had the greatest effect on population densities at all levels (site, zone and depth) with more rugose environments containing significantly higher densities and wider size structures. Comparison between survey years revealed that D. antillarum populations have not increased since 2001, and urchins seem to prefer shallower, more complex and productive areas of the reef. Populations were dominated by medium to large (5-9 cm in test diameter) individuals and size-frequency distributions indicated that smaller juveniles were virtually absent compared to 2001, which could reflect a recruitment-limited population and explain in part, the lack of increase in population densities. The limited temporal scale of this study, high horizontal movement of individuals along the complex, shallower reef and inshore habitats could also explain the general decline in mean densities. Other extrinsic factors affecting reproductive output and/or succesful recruitment and survival of juveniles likely contribute to the high variablility in population densities observed over time.

Comparison of phagocytosis in three Caribbean Sea urchins.

In 1983 large numbers of the sea urchin Diadema antillarum unexplainably began showing signs of illness and dying in the Caribbean, and over the next year they came close to extinction, making it one of the worst mass mortality events on record. Present evidence suggests a water-borne pathogen as the etiological agent. Decades later Diadema densities remain low, and its near extinction has been a major factor in transforming living coral reefs in the Caribbean to barren algae-covered rock. In the ensuing decades, no solid explanation has been found to the questions: what killed Diadema; why did Diadema succumb while other species of urchins on the same reefs did not; and why has Diadema still not recovered? A recent hypothesis posited by our lab as to Diadema's vulnerability was directed at possible compromised immunity in Diadema, and experimental results found a significantly impaired humoral response to a key component of gram-negative bacteria. Here we use flow cytometry to examine the cellular arm of invertebrate immunity. We performed cytotoxicity and phagocytosis assays as a measure of the cellular immune responses of cells from Diadema and two other species of sea urchins not affected by the die-off. Despite our previous findings of in impaired humoral response, our study found no apparent difference in the cellular phagocytic response of Diadema compared to the other urchin species studied.

Assessing the herbivore role of the sea-urchin Echinometra viridis: Keys to determine the structure of communities in disturbed coral reefs.

Echinometra viridis previously was considered a cryptic species unable to control the development and growth of macroalgae on coral reefs. Its role as a herbivore was seen as minor compared to other grazers present on the reef. However, the present disturbed state of some reefs has highlighted the role played by this sea-urchin. Combining field data with experiments on the Caribbean coast of Panama, we demonstrate that the current community organization on disturbed coral reefs in the Mesoamerican Caribbean is largely due to the action of E. viridis. It is the most abundant sea-urchin species, together with two others (Diadema antillarum and Echinometra lucunter). Field data also indicate that the relationship between its density and the abundance of macroalgae is stronger and it is more negative in impact than those of the other two. However, the niche this urchin exploits most efficiently is confined to leeward reefs with low levels of sedimentation. Outside these habitats, their populations are not decisive in controlling macroalgal growth. Grazing experiments showed that E. viridis consumes more fresh macroalgae per day and per weight of sea-urchin, and is a more effective grazer than D. antillarum or E. lucunter. E. viridis showed food preferences for early-successional turf macroalgae (Acanthophora spicifera), avoiding the less palatable late-successional and fleshy macroalgae (Lobophora variegata, Halimeda opuntia). However, it becomes a generalist herbivore feeding on all varieties of macroalgae when resources are scarce. H. opuntia is the macroalga that most resists E. viridis activity, which may explain its wide distribution.

Actividad antibacteriana y antifúngica de la estrella de mar Oreaster reticulatus (Valvatida: Oreasteridae) y de los erizos de mar Mellita quinquiesperforata (Clypeasteroida: Mellitidae) y Diadema antillarum (Diadematoida: Diadematidae) del Caribe Colombiano / Antibacterial and antifungal activity of the starfish Oreaster reticulatus (Valvatida: Oreasteridae) and the sea urchins Mellita quinquiesperforata (Clypeasteroida: Mellitidae) and Diadema antillarum (Diadematoida: Diadematidae) from the Colombian Caribbean

Resumen Como organismos bentónicos, estrellas de mar y erizos de mar están constantemente expuestos a un gran número de bacterias, hongos y virus, algunos de ellos potencialmente dañinos. Para sobrevivir, estos equinodermos dependen de su sistema inmunológico, que ha desarrollado una serie de compuestos que actúan como estrategias de defensa antimicrobianos. En este trabajo se evaluaron las actividades antibacteriana y antifúngica de los extractos metanólicos de la estrella de mar Oreaster reticulatus y de los erizos de mar Mellita quinquiesperforata y Diadema antillarum recolectados en el Caribe Cordobés, frente a las bacterias Escherichia coli, Staphylococcus aureus y Klebsiella pneumoniae, y frente a los hongos fitopatógenos Fusarium sp., Scleortium sp., y Rhizoctonia sp. Los resultados obtenidos mostraron que O. reticulatus y D. antillarum, son organismos capaces de producir compuestos con capacidad antibiótica generando inhibición bacteriana a bajas concentraciones (< 100 µg / ml), mientras que M. quinquiesperforata no presentó inhibición a ninguna de la concentraciones evaluadas. Específicamente, la cepa de S. aureus fue la que presentó mayor susceptibilidad frente a los extractos evaluados, es decir, los metabolitos producidos por los equinodermos inhiben con mayor facilidad las bacterias Gram +. Por su parte, solo el extracto de diclorometano de D. antillarum presentó inhibición frente a Fusarium sp., con porcentajes de inhibición de 78.2 % y 56.5 % a concentraciones de 2 000 y 100 µg / ml. Se encontró que las cepas de los hongos Sclerotium sp. y Rhizoctonia sp., presentaron resistencia frente a todos los.extractos de los organismos estudiados, con excepción del extracto de diclorometano de D. antillarum.

Abstract As benthic organisms, sea stars and sea urchins are constantly exposed to a large number of bacteria, fungi and viruses, some of them potentially harmful. To survive, these echinoderms depend on their immune system, which has developed a number of compounds which act as antimicrobial defense strategies. In this work, the antibacterial and antifungal activities of the extracts of the starfish Oreaster reticulatus and sea urchins Diadema antillarum and Mellita quinquiesperforata collected in the Caribbean Cordobés were evaluated against the bacteria Escherichia coli, Staphylococcus aureus and Klebsiella pneumoniae and against the phytopathogenic fungi Fusarium sp., Scleortium sp., and Rhizoctonia sp. Our results show that O. reticulatus and D. antillarum produce compounds producing bacterial inhibition at low concentrations (< 100 μg / ml), while, M. quinquiesperforata extracts showed no inhibition at any of the concentrations tested. Specifically, the strain of S. aureus was the one with greater susceptibility to the extracts evaluated, i.e. the metabolites produced by echinoderms inhibit more easily gram + bacteria. Only the D. antillarum dichloromethane affected Fusarium sp. with inhibition of 78.2 % and 56.5 % at concentrations of 2 000 and 100 μg / ml. Strains of the fungi Sclerotium sp. and Rhizoctonia sp. had resistance to all extracts. Rev. Biol. Trop. 63 (Suppl. 2): 329-337. Epub 2015 June 01.

Influence of Diadema antillarum populations (Echinodermata: Diadematidae) on algal community structure in Jardines de la Reina, Cuba

The 1983-1984 mass mortality of Diadema antillarum produced severe damages on Caribbean reefs contributing to substantial changes in community structure that still persist. Despite the importance of Diadema grazing in structuring coral reefs, available information on current abundances and algal-urchin interactions in Cuba is scarce. We analyzed spatial variations in Diadema abundance and its influence on algal community structure in 22 reef sites in Jardines de la Reina, in June/2004 and April/2005. Urchins were counted in five 30x2m transects per site, and algal coverage was estimated in randomly located 0.25m side quadrats (15 per site). Abundances of Diadema were higher at reef crests (0.013-1.553 ind/m²), while reef slope populations showed values up to three orders of magnitude lower and were overgrown by macroalgae (up to 87%, local values). Algal community structure at reef slopes were dominated by macroalgae, especially Dictyota, Lobophora and Halimeda while the most abundant macroalgae at reef crests were Halimeda and Amphiroa. Urchin densities were negatively and positively correlated with mean coverage of macroalgae and crustose coralline algae, respectively, when analyzing data pooled across all sites, but not with data from separate habitats (specially reef crest), suggesting, along with historical fish biomass, that shallow reef community structure is being shaped by the synergistic action of other factors (e.g. fish grazing) rather than the influence of Diadema alone. However, we observed clear signs of Diadema grazing at reef crests and decreased macroalgal cover according to 2001 data, what suggest that grazing intensity at this habitat increased at the same time that Diadema recruitment began to be noticeable. Furthermore, the excessive abundance of macroalgae at reef slopes and the scarcity of crustose coralline algae seems to be due by the almost complete absence of D. antillarum at mid depth reefs, where local densities of this urchin were predominantly low. Rev. Biol. Trop. 59 (3): 1149-1163. Epub 2011 September 01.

A pesar de la importancia del forrageo de Diadema en la estructuración de los arrecifes de coral, la información disponible sobre la actual abundancia de algas y de las interacciones de erizos en Cuba es escasa. Por lo tanto, se analizan las variaciones espaciales en la abundancia de Diadema antillarum y su influencia sobre las algas en 22 arrecifes en Jardines de la Reina, en junio/2004 y abril/2005. Los erizos se muestrearon en recorridos de 30x2m (5/sitio) y las algas en cuadrículas de 0.25m de lado (15/sitio). Las densidades de Diadema fueron mayores en las crestas arrecifales (0.013-1.553ind/m²) mientras que las pendientes mostraron valores hasta tres ordenes de magnitud menor y presentaron un cubrimiento excesivo de macroalgas (hasta 87%), siendo las más abundantes Dictyota, Lobophora y Halimeda. Las densidades de erizos estuvieron correlacionadas negativa y positivamente con el cubrimiento de macroalgas y algas costrosas, respectivamente, en el análisis global, pero no en hábitats separados (especialmente en crestas), sugiriendo, conjuntamente con la biomasa histórica de peces, que la estructura de las comunidades en las crestas está determinada por la acción sinérgica de otros factores (herbivoría de peces) más que por la influencia de Diadema solo. No obstante, se observaron indicios del forrajeo de Diadema, y el cubrimiento de macroalgas disminuyó desde 2001, lo cual sugiere que la intensidad de la herbivoría aumentó al mismo tiempo que el reclutamiento de Diadema.

Monitoring coral reefs, seagrasses and mangroves in Costa Rica (CARICOMP)

The coral reefs, seagrasses and mangroves from the Costa Rican Caribbean coast have been monitored since 1999 using the CARICOMP protocol. Live coral cover at Meager Shoal reef bank (7 to 10m depth) at the Parque Nacional Cahuita (National Park), increased from 13.3% in 1999, to 28.2% in 2003, but decreased during the next 5 years to around 17.5%. Algal cover increased significantly since 2003 from 36.6% to 61.3% in 2008. The density of Diadema antillarum oscillated between 2 and 7ind/m2, while Echinometra viridis decreased significantly from 20 to 0.6ind/m2. Compared to other CARICOMP sites, live coral cover, fish diversity and density, and sea urchin density were low, and algal cover was intermediate. The seagrass site, also in the Parque Nacional Cahuita, is dominated by Thalassia testudinum and showed an intermediate productivity (2.7±1.15 g/m2/d) and biomass (822.8±391.84 g/m2) compared to other CARICOMP sites. Coral reefs and seagrasses at the Parque Nacional Cahuita continue to be impacted by high sediment loads from terrestrial origin. The mangrove forest at Gandoca, within the Refugio Nacional de Vida Silvestre Gandoca-Manzanillo (National Wildlife Refuge), surrounds a lagoon and it is dominated by the red mangrove, Rhizophora mangle. Productivity and flower production peak was in July. Biomass (14kg/m2) and density (9.0±0.58 trees/100m2) in Gandoca were relatively low compared to other CARICOMP sites, while productivity in July in Costa Rica (4g/m2/d) was intermediate, similar to most CARICOMP sites. This mangrove is expanding and has low human impact thus far. Management actions should be taken to protect and preserve these important coastal ecosystems. Rev. Biol. Trop. 58 (Suppl. 3): 1-22. Epub 2010 October 01.

Los arrecifes coralinos, pastos marinos y manglares de la costa Caribe de Costa Rica han sido monitoreados desde 1999 siguiendo el protocolo de CARICOMP. La cobertura de coral vivo en el arrecife de Meager Shoal (7 a 10m de profundidad) en el Parque Nacional Cahuita, aumentó de 13.3% en 1999, a 28.2% en 2003, pero después bajó, por los siguientes 5 años, a aproximadamente 17.5%; la cobertura de algas aumentó significativamente de 36.6% en 2003 a 61.3% en 2008. La densidad de Diadema antillarum osciló entre 2 y 7 ind/m2 mientras que Echinometra viridis decreció significativamente de 20 a 0.6 ind/m2. Comparado con otros sitios CARICOMP, la cobertura de coral vivo, diversidad y densidad de peces, y densidades de erizos de mar fueron bajas y la cobertura algal intermedia. El sitio de pastos marinos, también en el Parque Nacional Cahuita, está dominado por Thalassia testudinum y tiene una productividad (2.7±1.15g/m2/d) y biomasa (822.8±391.84g/m2) intermedia comparado a otros sitios CARICOMP. Los arrecifes coralinos y pastos marinos en el Parque Nacional Cahuita continúan siendo impactados por sedimentos terrígenos. El bosque de manglar en Laguna Gandoca, dentro del Refugio Nacional de Vida Silvestre Gandoca-Manzanillo, está bordeado por una laguna y predomina el mangle rojo, Rhizophora mangle. El pico de productividad y producción de flores fue en julio. La biomasa (14 kg/m2) y densidad (9.0±0.58 árboles/100 m2) en Gandoca fueron relativamente bajas comparadas con otros sitios CARICOMP, mientras que la productividad en julio en Costa Rica (4g/m2/d) fue intermedia, similar a la mayoría de los sitios CARICOMP. Este manglar se está expandiendo y tiene muy poco impacto humano hasta ahora. Se deben tomar acciones de manejo para proteger y preservar estos importantes ecosistemas costeros.

Temporal and Spatial Distribution Patterns of Echinoderm Larvae in La Parguera, Puerto Rico

This study describes temporal and spatial abundance patterns of echinoderm larvae in La Parguera, Puerto Rico. For the temporal study, larvae were sampled by a series of monthly tows taken with a 64μm mesh net between the new and full moon from April 2005 to July 2006, September 2006 and August 2007. In order to measure spatial variation of echinoderm larval bundances, oblique tows were taken with 64 and 202μm mesh nets at seven different sites within the shelf, at the shelf-edge, and at a nearby oceanic stations during August 2007. Overall, Echinoidea (sea urchin) exhibited the highest abundance with a total of 11 921 larvae, representing 52.5% of the total collection. Ophiuroidea (brittle star) ranked second in abundance with 45.6% of the total larvae. Holothuroidea (sea cucumber) and Asteroidea larvae (sea star) accounted for less than 2% of the total echinoderm larval collection. Early larval stages (2-8 day old) of Diadema antillarum represented 20% of the total Echinoidea larvae. There was no marked seasonal trend of echinoderm larval abundance; Echinoidea and Ophiuroidea larvae were present in all monthly samples indicating that reproduction occurs year-round. Peak abundances of later-stage Echinoidea larvae were observed during January, July and October and of later-stage Ophiuroidea larvae during June, August and October. The observed peaks of later-stage larval abundances may be indicative of higher recruitment activity during these months. There was a significant difference of echinoderm larval abundance between spatial stations, with higher abundances collected at the shelf-edge. Later-stage (~24 day old) D. antillarum larvae were mostly collected at shelf-edge and oceanic locations. In addition, the 64mm mesh net was more efficient for collection of echinoderm larvae than the 202mm mesh net. Rev. Biol. Trop. 58 (Suppl. 3): 81-88. Epub 2010 October 01.

Este estudio describe patrones de abundancia temporal y espacial de larvas de equinodermos en La Parguera, Puerto Rico. La distribución temporal de equinodermos se caracterizó mediante una serie de arrastres mensuales entre la luna nueva y luna llena, entre abril y julio 2005, en septiembre 2006 y agosto 2007. Para evaluar la distribución espacial de las larvas de equinodermos se llevaron a cabo arrastres oblicuos con mallas de 64 y 202mm en siete estaciones dentro de beríl, en el beríl y mar afuera (oceánica) durante agosto 2007. En total, los equinoideos exhibieron la mayor abundancia con un total de 11 921 larvas colectadas, de las cuales 52.5% eran de Echinoidea (erizos). Las de Ophiuroidea (estrellas quebradizas) representaron el 45.6% del total de larvas colectadas. Larvas de Holothuroidea (pepino del mar) y Asteroidea (estrella del mar) constituyeron menos del 2% del total de larvas. Estadíos larvales tempranos (2-8 días) de Diadema antillarum fueron el 20% del total de larvas de equinoideos. No se observaron patrones estacional es de larvas de equinodermos, larvas de equinoideos y ofiuroideos se observaron en todos los muestreos mensuales, indicando reproducción continua durante todo del año. Se observó una alta abundancia de larvas de equinoideos en estado avanzado durante los meses de julio, octubre y enero, y en los meses de junio, octubre y agosto para ofiuroideos. El incremento observado de abundancia de larvas en estos meses puede ser indicativo de una alta actividad de reclutamiento durante este periodo. Hubo una diferencia significativa de abundancia larval entre estaciones a través del gradiente costero-oceánico, resultando ser el beril donde la abundancia fue más alta. Larvas de D. antillarum en estado avanzado (~24 días) se colectaron mayormente en el beril y localidades oceánicas. Estos patrones de distribución mar afuera pueden estar inhibiendo una recuperación de las poblaciones de D. antillarum mar adentro. La malla de 64mm fue más eficiente para colectar larvas de equinodermos en este estudio.

Abundance, distribution and size structure of Diadema antillarum (Echinodermata: Diadematidae) in South Eastern Cuban coral reefs

The 1983-1984 mass mortality event of Diadema antillarum affected more than 93% of the total Caribbean population. Although there are no records about the status of Diadema populations before and after die-off on Cuban reefs, anecdotal information suggests that populations were struck. We analyzed spatial variation in the abundance and size structure of D. antillarum in 22 reefs sites in Jardines de la Reina, from June 2004 to September 2005. Counts of Diadema were performed in five 30x2m transects at each sampling site and sampling time, and test diameters were measured in September 2005 at the same fore reefs. Abundances were higher at reef crests (mean densities 0.08-2.18 ind./m²), while reef slope populations reached a maximum site level of 0.13 ind./m² at only one site and showed values up to three orders of magnitude lower than those from reef crests. Highest abundance occurred at the west margin of major channels between keys where larval recruitment seems to be favored by local oceanographic features and facilitated by the abundance of Echinometra lucunter. The size frequency distribution of D. antillarum indicates that recruitment began to be noticeable three years before September 2005, suggesting these populations were depleted in the past and they are recovering now. Rev. Biol. Trop. 58 (2): 663-676. Epub 2010 June 02.

La mortalidad de Diadema antillarum en 1983-1984 afectó más del 93% de la población del Caribe. Aunque no existen datos publicados sobre el estado de sus poblaciones en arrecifes cubanos antes y después de la mortalidad, se conoce anecdóticamente que fueron afectadas. En el presente trabajo se analizan las variaciones espaciales de la abundancia y estructura de tallas de D. antillarum en 22 arrecifes frontales en Jardines de la Reina, para lo cual se realizaron cinco recorridos de 30x2m en cada sitio entre Junio de 2004 y Septiembre de 2005. Las densidades de Diadema fueron mayores en las crestas arrecifales (0.08-2.18 ind./m²) mientras que en las pendientes fueron hasta tres órdenes de magnitud menor y la densidad máxima fue 0.13 ind./m². Las crestas con mayor abundancia de Diadema están ubicadas en los márgenes de las grandes pasas existentes entre cayos donde el reclutamiento parece estar favorecido por las condiciones oceanográficas locales y facilitado por la abundancia de Echinometra lucunter. La distribución de frecuencia de tallas de Diadema sugiere que el reclutamiento comenzó a ser notable aproximadamente tres años antes del muestreo, indicando que en el pasado sus poblaciones estuvieron afectadas y ahora están recuperándose.

A recent increase in the abundance of the echinoid Diadema antillarum in Dominica (Lesser Antilles): 2001-2005 / Un aumento reciente en la abundancia del equinoideo Diadema antillarum en Dominica (Antillas Menores): 2001-2005

Diadema antillarum populations at many Caribbean locations have failed to recover from the pathogen-induced mortality events of the 1980s. It has become clear that the massive decline of this herbivorous urchin and the wide-spread absence of a population recovery lead to numerous long-term ecological consequences and reef degradation. While few quantitative studies on pre-mortality exist, great effort has been put forth to monitor remaining populations and their recovery. However, the patchy distribution of D. antillarum coupled with paucity of long-term studies based on the same methods applied at the same locations undermines the value of local as well as regional comparisons. In Dominica, ongoing quantitative assessments of D. antillarum began in 2001. Surveys of D. antillarum abundance are being carried out in 4-month intervals at six 100 m² sites; spread over 38 km along the west coast. The density of D. antillarum has differed significantly between sites, ranging from 0.81(SD= 0.04) to 3.13 m-2 (SD= 2.10), and increased by 61.11% during the first five years of this study. Seasonal fluctuations, possibly related to spawning aggregations, are also evident. The current abundance of D. antillarum on Dominican reefs contrasts that of Caribbean locations with recorded incidents of mass mortality events, and in some cases resembles pre-mortality densities from the early 1970s. Prior to this study, no systematic quantitative assessments of D. antillarum were carried out in Dominica. It is thus unclear in what way Dominica’s D. antillarum were affected by the mass mortality events observed elsewhere in the 1980s. The increase in D. antillarum density so far observed may thus be the recovery from a pathogen-induced disturbance or from Hurricane Lenny in November 1999. Locally, D. antillarum is important grazer on Dominican’s reefs, where over-fishing has drastically reduced the number of herbivorous fishes. On a regional scale, the island’s D. antillarum may represent a source of larvae for downstream islands, given the duration of the echinoplutei stage and a range of larval dispersal of hundreds of kilometers. Rev. Biol. Trop. 54 (Suppl. 3): 97-103. Epub 2007 Jan. 15.

Las poblaciones de Diadema antillarum de muchas localidades del Caribe, no se han recuperado después de los eventos de mortandad, inducidos por un patógeno, en la década de 1980. Se ha podido demostrar que la muerte masiva de este erizo herbívoro y la ausencia de recuperación, han tenido consecuencias ecológicas que han producido la degradación de los arrecifes. Existen pocos estudios pre-mortalidad, pero se han realizado grandes esfuerzos para monitorear las poblaciones restantes y su recuperación. Sin embargo, la distribución en parches de D. antillarum combinado con pocos estudios a largo plazo usando la misma metodología en los mismos sitios, mina la posibilidad de comparaciones locales y regionales. En Dominica, el monitoreo cuantitativo de D. antillarum empezó en 2001. Cada cuatro meses se realizan determinaciones de abundancia de D. antillarum en seis sitios de 100 m²; distribuidos a lo largo de 38 km de la costa oeste. La densidad de D. antillarum, fue significativamente diferente entre sitios, con ámbitos de 0.81 (SD= 0.04) a 3.13 m-2 (SD= 2.10), y aumentó 61.11% durante los primeros cinco años de estudio. Fluctuaciones estacionales, posiblemente relacionadas con agregaciones reproductivas, son evidentes. La abundancia actual de D. antillarum en los arrecifes de Dominica contrasta con otros sitios en el Caribe que sufrieron mortandades masivas y en algunos casos se parece a densidades pre-mortalidad de inicios de la década de 1970. Antes de este trabajo, no se había realizado ningún estudio sistemático de Diadema en Dominica, por lo que no es claro como fueron afectadas las poblaciones en este sitio. El aumento en la densidad de D. antillarum observado hasta ahora puede deberse a recuperación tras una perturbación por un patógeno o por el Huracán Lenny de noviembre 1999. Localmente, D. antillarum es un herbívoro importante en los arrecifes de Dominica donde la sobrepesca ha disminuido el número de peces herbívoros. En escala regional, las poblaciones de D. antillarum de la isla de Dominica pueden representar una fuente de larvas corriente abajo, dada la duración de estadio equiinopluteo y el ámbito de dispersión de las larvas, que es de cientos de kilómetros.

Abundancia de Diadema antillarum (Echinodermata: Echinoidea) en las costas de Venezuela / Abundance of Diadema antillarum (Echinodermata: Echinoidea) in the coasts of Venezuela

Diadema antillarum is a shallow-water sea-urchin from the tropical Atlantic whose populations almost disappeared in 1983-84 because of widespread mortalities which reached 87-100 %. In Venezuela, urchin population densities before the mortality event were comparable to those of other Caribbean regions; however, later abundancies remain unknown. The objectives of this study were to evaluate the recent densities of certain D. antillarum populations along the Venezuelan coasts and compare the densities at the Parque Nacional Mochima before and after the mortality. At each location urchin densities were determined by means of transects using 1 m2-quadrats as sampling units. The highest mean densities were observed at the sites on the central coast: Ensenada de Oricao, 0.28 ind/m2 (2002) and 1.05 ind/m2 (2003), and Chichiriviche de la Costa, 0.84 ind/m2 (2002) and 0.74 ind/m2 (2003). In Mochima, the mean density before the mortality for D. antillarum oscillated between 0.28 and 4 ind/m2, after the mortality event the mean density varied between 0.15 ind/m2 (2000) and 0.47 ind/m2 (2000). The populations of D. antillarum studied at Parque Nacional Morrocoy and Refugio de Fauna Silvestre Cuare showed highest densities at Playuela (0.43 ind/m2) and Cayo Sur (0.95 ind/m2) respectively, whereas other sites showed densities below 0.1 ind/m2. The density registered at Playuela in 2003 is lower than that reported before the mortality event (0.58-3.64 ind/m2). The density for Parque Nacional Archipiélago de Los Roques, specifically for the Arrecife de Herradura remained constant between 2002 and 2003 with values between 0.22-0.23 ind/m2 respectively. To conclude, the sea urchin abundancies observed at most of the Venezuelan coastal sites that we studied were higher than those reported for other areas of the northern Caribbean, even though the values have not yet returned to those preceding the 1984 mass-mortality event, due to the slow recovery of the populations.

Diadema antillarum es un erizo de aguas someras del Atlántico tropical cuyas poblaciones fueron diezmadas entre los años 1983-1984 con mortandades de hasta 87-100 %. En Venezuela, las densidades registradas antes de la mortalidad presentaban valores similares a los de otras regiones del Caribe, sin embargo se desconoce las abundancias posteriores al evento. Los objetivos del presente estudio fueron evaluar las densidades recientes de algunas poblaciones de D. antillarum a lo largo de las costas de Venezuela y comparar las densidades de la Bahía de Mochima antes y después de la mortandad. Se utilizaron transectos, y cuadrantes de 1m2 como unidad muestreal. Se registraron las mayores densidades promedio en las localidades del litoral central: Ensenada de Oricao con 0.28 ind/m2 (2002) y 1.05 ind/m2 (2003), y Chichiriviche de la Costa con 0.84 ind/m2 (2002) y 0.74 ind/m2 (2003). En la Bahía de Mochima, la densidad promedio antes de la mortandad de D. antillarum osciló entre 0.28 y 4 ind/m2, luego del evento de mortandad la densidad promedio varió entre 0.15 ind/m2 (2000) y 0.47 ind/m2 (2002). Las poblaciones de D. antillarum estudiadas en el Parque Nacional Morrocoy y Refugio de Fauna Silvestre Cuare presentaron las densidades promedio más altas en Playuela (0.43 ind/m2) y Cayo Sur (0.95 ind/m2), mientras que las demás áreas presentaron densidades inferiores a 0.1 ind/m2. La densidad registrada en Playuela en el 2003 es menor a la informada antes del evento de mortandad (0.58-3.64 ind/m2). La densidad del Parque Nacional Archipiélago Los Roques, específicamente en el Arrecife de Herradura, se mantuvo constante durante 2002-2003, con valores entre 0.22 y 0.23 ind/m2 respectivamente. En conclusión, las abundancias registradas en la mayoría de las localidades evaluadas en Venezuela son superiores a las informadas para áreas al norte del Caribe, aunque todavía no se ha alcanzado los niveles anteriores a la mortalidad de 1984 por el lento incremento de las poblaciones.

Recruitment-limitation in open populations of Diadema antillarum: an evaluation.

Empirical evidence from studies of the sea urchin Diadema antillarum suggests that this organism widely disperses its offspring, that both recruitment and mortality rates are independent of local densities, and that local food availability does not regulate local population sizes. These attributes would indicate that local populations are generally open and recruitment-limited. Given that current populations have been devastated by a 1983-1984 mass mortality event which spread throughout the range of this species, we examine current population trends and evaluate the prospects for population recovery under the assumptions of recruitment-limitation and density-independent rates of recruitment and mortality. Specifically, we evaluate the dynamics of five, local populations at Lameshur Bay, St. John, U.S.V.I. in order to 1) determine current rates of recruitment and mortality, 2) predict population densities based on the above assumptions, 3) compare predicted densities against observed 1984-1988 densities, and 4) predict future population densities based on current trends. We estimate current recruitment rates at 0.02-0.11 individuals/m2/yr and per capita mortality rates at 0.27-0.47 deaths/yr. Over the period 1985-1988, predicted densities based on these annual rates did not differ significantly from actual observed densities. Therefore, the assumptions that recruitment and mortality rates are density-independent and that local populations are recruitment-limited are sufficient, at present, to adequately predict current population trends. These trends indicate no recovery towards pre-mass mortality densities. The above description of the dynamics of open, recruitment-limited populations may be appropriate for a wide variety of organisms. We note the prevalence of animals with extensive larval dispersal capabilities. Populations located near the limits of their distribution, in freshwater streams and ponds, mountain tops, or other similarly isolated populations may also be subject to recruitment-limitation. Remote, recruitment-limited populations are likely to be more susceptible to local extinction than less remote populations. Dispersal distances and the scale of the processes controlling recruitment and mortality are important determinants of the degree of openness of local populations.

Density-dependent size regulation and negative growth in the sea urchin Diadema antillarum Philippi.

This study documents size- and density-dependent growth (positive and negative), in the sea urchin Diadema antillarum. In the summer of 1983, an inverse relationship was found between Diadema test diameter and population density at seven sites in Lameshur Bay, St. John, United States Virgin Islands. The regression of this relationship improved when test diameter was plotted against density per unit grazing area. A field experiment demonstrated that 1) Diadema has the ability to reduce skeletal body size, and 2) direction (growth or shrinkage) and rate of growth can be predicted accurately based on the urchin's body size and population density. The ability to adjust body size as density fluctuates may allow Diadema to persist when density increases, by shrinking and reducing metabolic costs, and to take advantage of decreases in density, by increasing in size and fecundity.