Long-spined Sea Urchin Diadema Antillarum Research Articles

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.

Impacts of hurricanes and disease on Diadema antillarum in shallow water reef and mangrove locations in St John, USVI.

The 1983-1984 mortality event of the long-spined sea urchin Diadema antillarum reduced their population by up to 99% and was accompanied by a phase shift from coral dominated to algal dominated reefs in the Caribbean. Modest rebounds of D. antillarum populations in the Caribbean have been noted, and here we document the impacts of two major hurricanes (2017, Irma and Maria) and the 2022 disease outbreak on populations of D. antillarum found by targeted surveys in the urchin zone at nine fringing reef and three mangrove sites on St. John, USVI. D. antillarum populations at the reef sites had declined by 66% five months after the hurricanes but showed significant recovery just one year later. The impact of recent disease on these populations was much more profound, with all reef populations exhibiting a significant decline (96.4% overall). Fifteen months after the disease was first noted, D. antillarum at reef sites exhibited a modest yet significant recovery (15% pre-disease density). D. antillarum populations in mangrove sites were impacted by the hurricanes but exhibited much higher density than reef sites after the disease outbreak, suggesting that at D. antillarum in some locations may be less vulnerable to disease.

Diurnal predators of restocked lab-reared and wild Diadema antillarum near artificial reefs in Saba.

The long-spined sea urchin Diadema antillarum controls reef dynamics by grazing on algae and increasing coral recruitment. Populations of Diadema never recovered after a mass-die off in 1983 and 1984, and numbers were further reduced by a more recent die-off in 2022. To restore grazing pressure and thereby the resilience of Caribbean coral reefs, multiple Diadema restocking efforts have been performed. Although results vary, relatively low retention is one of the reasons restocking is not considered more often. If causes for the low retention can be identified, suitable measures may be able to increase restocking success. In this study, we monitored restocked lab-reared and wild juvenile Diadema on artificial reefs around Saba, Caribbean Netherlands. To assess the retention of Diadema over time, we conducted diver surveys and used underwater photo time lapse during daylight. Retention of uncaged lab-reared and wild Diadema decreased steadily with less than 30% surviving after 10 days. In total, 138 predator-prey interactions were recorded, of which 99% involved the queen triggerfish Balistes vetula, although other potential predators were present in the area. None of the recorded predator-prey interactions was successful, which suggests that artificial reefs with incorporated shelters may be suitable for juveniles as daytime refuge. However, Diadema that were more often attacked during the day were more likely to be absent the next morning. Because queen triggerfish often visited the experimental site in the first or last hour of daylight, it could be that they were more successful in their attacks when it was too dark to see anything on the photos and when Diadema came out to feed or to look for better shelter opportunities. If Diadema migrated off the artificial reef, they were probably predated during the process, because no Diadema were found on surrounding reefs. Wild Diadema were attacked significantly more often than lab-reared Diadema, possibly because the wild urchins were larger, but this did not significantly affect retention. Future restocking should be performed on natural or artificial reefs with deeper shelters, so Diadema can retract farther into their crevice, and should include night-time monitoring to identify the remaining unknown factors that cause low retention, including migration and nocturnal predation. This knowledge is urgently needed to coral reef managers so they can increase Diadema restocking success by selecting reefs with a lower predator density, protect urchins during an acclimatization period and/or conduct temporary predator control measures.

Cue selection and ontogeny reveal larval settlement dynamics of the long-spined sea urchin Diadema antillarum, a keystone coral reef herbivore

Cue selection and ontogeny reveal larval settlement dynamics of the long-spined sea urchin Diadema antillarum, a keystone coral reef herbivore

The 2022 Diadema antillarum die-off event: Comparisons with the 1983-1984 mass mortality

The 1983-1984 die-off of the long-spined sea urchin Diadema antillarum stands out as a catastrophic marine event because of its detrimental effects on Caribbean coral reefs. Without the grazing activities of this key herbivore, turf and macroalgae became the dominant benthic group, inhibiting coral recruitment and compromising coral reef recovery from other disturbances. In the decades that followed, recovery of D. antillarum populations was slow to non-existent. In late January 2022, a new mass mortality of D. antillarum was first observed in the U.S. Virgin Islands. We documented the spread and extent of this new die-off using an online survey. Infected individuals were closely monitored in the lab to record signs of illness, while a large population on Saba, Dutch Caribbean, was surveyed weekly before and during mortality to determine the lethality of this event. Within four months the die-off was distributed over 1,300 km from north to south and 2,500 km east to west. Whereas the 1983-1984 die-off advanced mostly with the currents, the 2022 event has appeared far more quickly in geographically distant areas. First die-off observations in each jurisdiction were often close to harbor areas, which, together with their rapid appearance, suggests that anthropogenic factors may have contributed to the spread of the causative agent. The signs of illness in sick D. antillarum were very similar to those recorded during the 1983-1984 die-off: lack of tube feet control, slow spine reaction followed by their loss, and necrosis of the epidermis were observed in both lab and wild urchins. Affected populations succumbed fast; within a month of the first signs of illness, a closely monitored population at Saba, Dutch Caribbean, had decreased from 4.05 individuals per m2 to 0.05 individuals per m2. Lethality can therefore be as high as 99%. The full extent of the 2022 D. antillarum die-off event is not currently known. The slower spread in the summer of 2022 might indicate that the die-off is coming to a (temporary) standstill. If this is the case, some populations will remain unaffected and potentially supply larvae to downstream areas and augment natural recovery processes. In addition, several D. antillarum rehabilitation approaches have been developed in the past decade and some are ready for large scale implementation. However, active conservation and restoration should not distract from the primary goal of identifying a cause and, if possible, implementing actions to decrease the likelihood of future D. antillarum die-off events.

First Record and Massive Spread of Tropical Long-Spined Sea Urchin Diadema antillarum in the Mediterranean Sea (Syrian Coast)

The biological structure of the Syrian marine environment still shows a rapid and steady increase in the number of warm water species, many of which have become dominant and invasive. In the latest field data during 2020-2021, the presence of the black sea urchin Diadema antillarum (Philippi, 1845) was recorded for the first time in several locations in Latakia and Ras al-Bassit coast, and its massive spread at depths of 5-8 m, accompanied by invasive species of macroalgae, sponges, crustaceans and mollusks.. It is noteworthy that this species is one of the most widespread and important species of sea urchins in some tropical areas, and this is the first record in the Mediterranean Sea and the Syrian coast It is important as it prey on macroalgae and has an effective role in the health of some of the most important areas of biodiversity in the world.

The role of algal chemical defenses in the feeding preferences of the long-spined sea urchin Diadema antillarum

The role of algal chemical defenses in the feeding preferences of the long-spined sea urchin Diadema antillarum

A novel system for intensive Diadema antillarum propagation as a step towards population enhancement

The long-spined sea urchin Diadema antillarum was once an abundant reef grazing herbivore throughout the Caribbean. During the early 1980s, D. antillarum populations were reduced by > 93% due to an undescribed disease. This event resulted in a lack of functional reef herbivory and contributed to ongoing ecological shifts from hard coral towards macroalgae dominated reefs. Limited natural recovery has increased interest in a range of strategies for augmenting herbivory. An area of focus has been developing scalable ex situ methods for rearing D. antillarum from gametes. The ultimate use of such a tool would be exploring hatchery origin restocking strategies. Intensive ex situ aquaculture is a potentially viable, yet difficult, method for producing D. antillarum at scales necessary to facilitate restocking. Here we describe a purpose-built, novel recirculating aquaculture system and the broodstock management and larval culture process that has produced multiple D. antillarum cohorts, and which has the potential for practical application in a dedicated hatchery setting. Adult animals held in captivity can be induced to spawn year-round, with some evidence for annual and lunar periodicity. Fecundity and fertilization rates are both consistently very high, yet challenges persist in both late stage larval development and early post-settlement survival. Initial success was realized with production of 100 juvenile D. antillarum from ~ 1200 competent larvae. While the system we describe requires a significant level of investment and technical expertise, this work advances D. antillarum culture efforts in potential future hatchery settings and improves the viability of scalable ex situ production for population enhancement.

Establishing a Diagnostic Technique for Coelomocentesis in the Long-Spined Sea Urchin Diadema antillarum.

Coelomic fluid aspiration has been utilized in echinoderms in research and clinical settings. Detailed procedural descriptions for coelomic fluid sampling in sea urchins (class Echinoidea) are lacking, and samples are prone to contamination. The objectives of this study were to (1) standardize a technique for coelomic fluid collection in long-spined sea urchin Diadema antillarum that optimizes the diagnostic quality of the sample utilizing diagnostic imaging, (2) identify coelomic fluid bacterial isolates (using Biolog GEN III MicroLog and 16s rDNA sequencing), and (3) compare positive cultures to animal weight, holding time prior to sampling, water temperature, and gross fluid appearance. Seventy Diadema antillarum from the Florida Keys collected in two groups (March and September 2015) were utilized. Positive cultures for bacterial contamination were identified in 5% and 44%, respectively, of animals in the sampling groups. Vibrio spp. was the predominant genus identified. Positive cultures were more frequent in the group with smaller-sized animals, increased holding times, and elevated water temperatures. Deviation from clear-pink gross coelomic fluid appearance did not reliably predict bacterial contamination. A standardized technique for coelomocentesis was defined. The use of the proposed coelomocentesis methodology may facilitate improved health evaluations of sea urchins and may be applicable to research, conservation efforts, and disease investigations.

Reef fish associations with sea urchins in an Atlantic oceanic island

Many reef fish are known to be associated with particular microhabitats that provide food and refuge, such as branching corals, gorgonians, macroalgal beds and sea urchins. We investigate the association of reef fishes with the long-spined sea urchin Diadema antillarum in shallow reefs of Trindade Island, southeastern Brazil. A total of 1283 fish individuals from seven families and nine species were associated with 495 sea urchins. Sea urchins provide important shelter especially for juveniles of the Noronha wrasse, Thalassoma noronhanum. Larger fishes were found at higher densities associated to sea urchins with larger spines. At reefs lacking structurally complex organisms, such as branching corals, sea urchins can be an important refuge for juveniles or small-bodied reef fish species, influencing their distribution and acting as ecosystem engineers.

Interacting effects of temperature, habitat and phenotype on predator avoidance behaviour in Diadema antillarum: implications for restorative conservation

Caribbean long-spined sea urchin Diadema antillarum populations crashed following a mass mortality event in 1983-1984 with cascading effects on reef health. Population restoration efforts may be hampered by unknown effects of short- and long-term elevated sea surface temperature (SST). We investigated how a key behavioural trait, predator avoidance behaviour (PAB; percentage of long defensive spines that moved in response to shadow stimuli), was affected by elevated SST in 180 individuals from 2 contrasting Honduran reefs: Utila (flattened reef structure, dearth of predation refugia) and Banco Capiro (complex reef structure, abundant refugia). Initiation of PAB is mediated by melanin, which breaks down at elevated water temperatures; thus, as SST rises, D. antillarum may become vulnerable to predation. We compared local current SST (CSST; 29.7°C) with 2 IPCC predicted long-term climate change scenarios under laboratory conditions. PAB decreased by 13.98-15.37% at CSST +1.4°C and 31.67-42.44% at CSST +3.1°C. Trial temperatures were similar to maxima recorded in the Caribbean during the 2016 El Nino, so our results also represent likely responses to worst-case short-term acute temperature anomalies. Juveniles maintained higher PAB than adults, indicating increased reliance on anti-predation behaviours. White-spined phenotypes from Utila’s flattened reef maintained higher PAB than black-spined counterparts, likely due to increased conspicuousness to visual predators. Habitat complexity may mitigate temperature-driven losses in natural behavioural defences. D. antillarum may be resilient to near-term (<2039) SST increases and periodic temperature stresses but may struggle under long-term, worst-case scenario conditions. Restoration of D. antillarum populations must be coupled to augmented reef complexity to improve future resilience.

Does Slow and Variable Recovery of Diadema antillarum on Caribbean Fore-Reefs Reflect Density-Dependent Habitat Selection?

Recovery of the Caribbean long-spined sea urchin Diadema antillarum from the pathogen-induced mass mortality event of 1983 has been slow and variable. Multiple studies indicate that post-mortality population densities are greatest in sheltered lagoon and back reef habitats, and that recovery is limited on forereefs where pre-mortality densities were also high [1-5]. We carried out detailed surveys of a recovering population of D. antillarum in Curacao to document an ongoing influence of habitat type on population density, and to explore what ecosystem characteristics might drive observed recovery patterns. We quantified D. antillarum population density, larval settlement rates, herbivorous fish biomass, algal turfs, macroalgae and predatory fish biomass in sites with and without structural complexity on reefs in sheltered lagoon and backreef locations, and on the forereef, using an orthogonal survey design. D. antillarum densities were greatest in sheltered lagoon and backreef locations, with high structural complexity. However, densities were significantly lower than those reported prior to the mass mortality event. Larval settlement rates were greater in sheltered lagoon and backreef locations but did not fully account for observed patterns in urchin density. Sheltered lagoon and backreef habitats had more turf algae and fewer herbivorous fish than forereef habitats. Predator abundance was generally low and did not differ significantly among habitat types. In light of our results, we hypothesize that patterns of D. antillarum recovery in Curacao are consistent with dynamics expected in the presence of density-dependent habitat selection. More algal resources and fewer herbivorous fish provide a mechanism for increased fitness and habitat suitability in sheltered, lagoon and backreef habitats. Forereefs, by contrast, offer reduced habitat suitability and, we hypothesize, will only be re-colonized once the carrying capacity of more favourable habitats is exceeded. We propose a number of testable predictions to explore this theory further, and advocate for including sheltered lagoon and backreef habitats in D. antillarum population surveys to monitor recovery, as well as protecting populations found in these habitats where necessary. We predict that when current populations return to pre-mortality densities, range expansion may allow for a return of D. antillarum to Caribbean forereefs.

Diadema antillarum Population Status Assessment in Dominican Republic 30 Years after the Mass Mortality Event

The long-spined sea urchin Diadema antillarum plays an important role in the coral reef community dynamics and geomorphology of the Caribbean. A dramatic dieoff event in 1983-84 reduced its population by as much as 95-99% throughout the Caribbean resulting in dramatic changes in the benthic community. This study aims to report population density; bathymetric distribution and population size structure of this sea urchin in four localities of Dominican Republic: Bayahibe, Punta Cana, Samana and Sosua. For this study, 15 m2 transects were conducted using a 0.5 x 0.5 (0.25) m2 quadrants at Acropora cervicornis restored reef sites. Transects were laid in and out the restored plots. The benthic cover was also estimated and classified in 5 main categories: macroalgae, coralline algae, corals, sand/rock/rubble and sponges. The mean density of D. antillarum obtained for the entire study was 0.89±0.11 Ind·m-2 (Mean ± SE, n=48). The distribution of this sea urchin was mostly limited to depths comprised from 1-10 m of the sublittoral; no significant differences were observed in the vertical distribution by age. The mean benthic cover found for the four localities was: Coral 6.75%, Macroalgae 22.66%, Coralline Algae 24.99%, Sand/Ruble/Rock 41.75% and Sponges 2.68%; although substrate communities vary significantly at different sites even within same localities, depending on multiple factors affecting the area. A discrete slow patchy recovery of D. antillarum has been observed in Dominican Republic.

Arrested recovery of Diadema antillarum population: Survival or recruitment limitation?

Densities of the long-spined sea urchin Diadema antillarum remain significantly below pre mass-mortality levels at most Caribbean localities. The arrested recovery of this formerly abundant herbivore has been attributed to low supply of recruits and high post settlement mortality. There is, however, some debate as to which of these factors is determinant of the local dynamics of this echinoid. In this study, we use demographic modeling to analyze the contribution of recruitment and post settlement survival on the dynamics of D. antillarum in four localities of Puerto Rico Archipelago. Our results indicate relatively high adult survival, and low stasis but high growth transition in the small individuals. Recruitment rates were low and exhibited high spatial and temporal variability. The four populations exhibited asymptotic growth rates (λ) below 1.0, with λ varying from 0.918 to 0.964. The elasticity analysis showed that the survival of large-sized Diadema can potentially contribute most to the changes in λ for all sites. Numerical projections of the populations indicate that no site would exhibit an increase in density under current recruitment rates, but doubling recruitment would produce an increase in sea urchin density in three of the four sites. Recovery of D. antillarum populations would require the spatial and temporal co-occurrence of high recruitment and survival rates.

Higher population densities of the sea urchin Diadema antillarum linked to wave sheltered areas in north Puerto Rico Archipelago

The long-spined sea urchin Diadema antillarum has been the focus of multiple studies since the mass mortality event in the 1980s. The recovery of this key herbivore in the wider Caribbean is essential for the well-being of coral reefs. This study examined the population density and structure of D. antillarum at seven northern fringing reefs of Puerto Rico between 2011 and 2013. The total mean density of the sea urchins in northern Puerto Rico was 0.9 ±0.3 ind m−2. Densities of D. antillarum significantly differed among sites, but not temporally. Differences in mean sizes were significant among sites and seasons. Areas with higher densities of D. antillarum showed lower cover of non-calcareous algae. Wave exposure was correlated with the abundance of the sea urchin. This study indicates that the observed abundance of D. antillarum has not yet returned to pre-mortality levels. However, densities showed some degree of recovery when compared with previous studies, enabling at least some degree of control on fleshy macroalgae communities. No significant changes in density occurred between 2011 and 2013, and sites with higher densities were generally located in leeward areas. The low relative abundance of small size individuals points towards recruitment limitation as an explanation for the limited recovery of D. antillarum.

Historical reconstruction of population density of the echinoid &lt;I&gt;Diadema antillarum&lt;/I&gt; on Florida Keys shallow bank-barrier reefs

The 1983-1984 caribbean-wide mass mortality of the once ubiquitous long-spined sea urchin Diadema antillarum Philippi, 1845, is one of several factors considered responsible for coral reef change throughout the region. Unfortunately, there is a paucity of pre-mortality event density data for D. antillarum in the Florida Keys, making it difficult to determine pre-1983 population density levels. results from surveys conducted during 1970-1973 in the lower Florida Keys, in shallow (<12 m) fore reef habitats, yielded relatively abundant and widespread D. antillarum densities in qualitative transects at five reefs prior to the 1983-1984 die-off. In quantitative surveys at one reef, Middle sambo reef in 1972, up to 7.9 individuals m-2 were recorded using quadrats in high-relief spur and groove habitat. A second mortality event in the Florida Keys, beginning in April 1991, again depressed urchin densities that had begun to recover from the 1983-1984 mass mortality. by 1992, D. antillarum densities (<0.01 m-2) were two orders of magnitude lower than pre-die-off estimates (range of 0.07-0.57 m-2 from several spur and groove reefs in the lower Florida Keys) and remained so through 2009. The pre-mortality echinoid density estimates detailed in the Florida Keys provide a baseline to compare with their current population status and should help inform managers about realistic recovery or restoration targets for D. antillarum.

Effects of predation upon the long-spined sea urchin Diadema antillarum by the spotted spiny lobster Panulirus guttatus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 495:185-191 (2014) - DOI: https://doi.org/10.3354/meps10568 Effects of predation upon the long-spined sea urchin Diadema antillarum by the spotted spiny lobster Panulirus guttatus Meredith D. Kintzing1,2, Mark J. Butler IV1,* 1Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529, USA 2Present address: University of North Carolina at Chapel Hill, Department of Marine Sciences, Chapel Hill, North Carolina 27599, USA *Corresponding author: mbutler@odu.edu ABSTRACT: Sea urchins, important herbivores in marine ecosystems, are strongly impacted by both the direct and indirect effects of predation, and the long-spined sea urchin Diadema antillarum is no exception. Once abundant on Caribbean coral reefs, D. antillarum populations were decimated by disease in the early 1980s, and only where their natural predators have been overfished has D. antillarum recovery been observed. Spiny lobsters (Palinuridae) are predators of sea urchins, and although there are several species of spiny lobster in the Caribbean, only the spotted spiny lobster Panulirus guttatus is restricted to coral reefs where D. antillarum dwells. We investigated the direct and indirect impacts of P. guttatus on D. antillarum mortality, foraging, and behavior in a series of laboratory experiments. We found that P. guttatus prey on D. antillarum, especially small urchins. D. antillarum also consumed significantly less algae in the presence of P. guttatus and fled when exposed to the odor of P. guttatus but apparently not the scent of the Caribbean spiny lobster P. argus. The altered foraging and avoidance behaviors displayed by D. antillarum are strong evidence that predation by P. guttatus has played an important, but underappreciated, role in the evolutionary history of D. antillarum and perhaps its recovery on Caribbean coral reefs. KEY WORDS: Diadema antillarum · Panulirus guttatus · Florida Keys · Predation · Trait-mediated interactions · Coral reefs Full text in pdf format PreviousNextCite this article as: Kintzing MD, Butler IV MJ (2014) Effects of predation upon the long-spined sea urchin Diadema antillarum by the spotted spiny lobster Panulirus guttatus. Mar Ecol Prog Ser 495:185-191. https://doi.org/10.3354/meps10568 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 495. Online publication date: January 09, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Population status of the long-spined urchin &lt;I&gt;Diadema antillarum&lt;/I&gt; in Puerto Rico 20 years after a mass mortality event

A mass mortality event of the long-spined sea urchin Diadema antillarum (Philippi, 1845) occurred during 1983-1984 across the western Atlantic. Recovery to pre-mortality densities has been slow throughout most of the Caribbean as current stocks remain low, existing at a small fraction of previously recorded levels. To measure population recovery at Puerto Rico, we surveyed 26 localities around the island during 2003-2004. At each reef, we deployed 15 × 2 m belt transects (n = 12) to detect and quantify the presence of D. antillarum and obtain data on benthic cover. Density of D. antillarum varied significantly among geographic regions and localities, though variability was high. The highest density was documented in the Culebra Island region (0.44 ind m-2), followed by the northern region of Puerto Rico (0.23 ind m-2). No individuals of D. antillarum were found in 11 of the 26 surveyed localities. These densities are still substantially lower than pre- and post-mortality estimates from Puerto Rico. Most of the reefs were characterized by high macroalgal cover and horizontal water transparency < 3 m. Urchin densities were significantly and positively correlated with percentage of coral cover, percentage of coralline algae, and water transparency

Can one species determine the structure of the benthic community on a temperate rocky reef? The case of the long-spined sea-urchin Diadema antillarum (Echinodermata: Echinoidea) in the eastern Atlantic

We sampled 36 coastal rocky reefs throughout the overall Canarian Archipelago and consider (1) the daily macroalgal consumption of the long-spined sea urchin Diadema antillarum and (2) the daily net production of macroalgae along temperate rocky-substrates, to provide evidence that Diadema antillarum plays an important role in the structure of the shallow benthic environment of the eastern Atlantic. D. antillarum was found to be the main key-herbivore species, as it controls by its own the algal assemblages, with negligible contribution of other grazing species.

Patterns of nocturnal movement of the long-spined sea urchin Diadema antillarum (Philippi) in Gran Canaria (the Canary Islands, central East Atlantic Ocean)

We tagged individuals of the sea urchin Diadema antillarum (Philippi) around the island of Gran Canaria (The Canary Islands) during winter 2001–2002 using a new technique, consisting of the insertion of a hook fastened to a fishing line into the aboral pole (periproctal membrane). This allowed individual identification of tagged sea urchins. The goals were: (1) to quantify nocturnal movements and the homing behaviour of this echinoid on shallow rocky bottoms, and (2) to assess short term spatial and temporal variability of these movements. Tagged sea urchins displayed clear homing behaviour. The mean distance travelled at night was 3.7±1.2 m (range 1.0–5.1 m). Mean speed of nocturnal movement was 33±26 cm h−1 (range 5–110 cm h−1). We observed greater movement at midnight than at the beginning and the end of the night.