Echinoid Paracentrotus Lividus Research Articles

Post-metamorphic skeletal growth in the sea urchin Paracentrotus lividus and implications for body plan evolution

BackgroundUnderstanding the molecular and cellular processes that underpin animal development are crucial for understanding the diversity of body plans found on the planet today. Because of their abundance in the fossil record, and tractability as a model system in the lab, skeletons provide an ideal experimental model to understand the origins of animal diversity. We herein use molecular and cellular markers to understand the growth and development of the juvenile sea urchin (echinoid) skeleton.ResultsWe developed a detailed staging scheme based off of the first ~ 4 weeks of post-metamorphic life of the regular echinoid Paracentrotus lividus. We paired this scheme with immunohistochemical staining for neuronal, muscular, and skeletal tissues, and fluorescent assays of skeletal growth and cell proliferation to understand the molecular and cellular mechanisms underlying skeletal growth and development of the sea urchin body plan.ConclusionsOur experiments highlight the role of skeletogenic proteins in accretionary skeletal growth and cell proliferation in the addition of new metameric tissues. Furthermore, this work provides a framework for understanding the developmental evolution of sea urchin body plans on macroevolutionary timescales.

Seasonal variation in bioavailability of trace metals in the echinoid Paracentrotus lividus (Lamarck, 1816) from Algerian coastal waters: Effect of physiological indices

The goal of the present work was to assess the quality of Algerian coastal waters. It is based on the seasonal biomonitoring of the variation of the lead, cadmium, copper and zinc, through the sea urchin Paracentrotus lividus (Lamarck, 1819) collected at selected stations along the Algerian coast. The samples were collected continuously from 2013 (November) to 2014 (February, August, and November) at three sites: “Sidi Mejdoub”, “Willis” (Mostaganem) and “Bateau cassé” (Algiers), seasonally. Individuals of P. lividus were collected by snorkeling at the depths of 1–2 m. The obtained results showed that the physiological indices (gonad index) is influenced by the factor “Location” i.e. site; with a dominance of female sex. The level of metallic contamination does not present high levels. The dilution effect of the gonad index on the content of trace metals was noted. This influence requires adjusting the raw detected concentrations. The so called adjusted concentrations are freed of the physiology of the sea urchin, and the availability of trophic resources, which can therefore be compared with different sites.

Collapse of the echinoid Paracentrotus lividus populations in the Eastern Mediterranean--result of climate change?

The European purple sea urchin (Paracentrotus lividus) is considered to be a key herbivore throughout its distribution range—North-East Atlantic and Mediterranean Sea. It was also abundant in its eastern distributional edge, on rocky habitats of the coastline of Israel, but its populations have recently collapsed, and today it is an extremely rare species in the region. Field and laboratory experiments, that were carried out in order to examine the impact of the recent sea surface temperature rise in the Eastern Mediterranean, showed massive urchin mortality when temperatures crossed 30.5 °C before reaching peak summer values. These results suggest that elevated seawater temperatures in recent years may be a main cause for the disappearance of P. lividus from the southeast Mediterranean Sea, which may indicate distributional range contraction in this region.

Concentrations of As, Cd, Cr, Ni, and Pb in the echinoid Paracentrotus lividus on the coast of Civitavecchia, northern Tyrrhenian Sea, Italy

This work assessed the levels of As, Cd, Cr, Ni, and Pb in soft tissues (gonads and gut) of specimens of Paracentrotus lividus (Lamarck, 1816) collected from the coast of Civitavecchia, in the northern Tyrrhenian Sea. The average levels, in order of concentration, were 14.64 mg/kg As, 3.58 mg/kg Cr, 1.18 mg/kg Pb, 1.15 mg/kg Ni, and 0.07 mg/kg Cd. Dry weight concentrations described bioaccumulation of As and Cr, and, to a lesser extent, Ni and Pb. A hotspot of As at the station near the delta of Marangone stream reflected the effect of mine waste deposits of galena, pyrite, and marcasite in this basin. The As concentration in the northern part of the study area increased closer to the Mignone delta, and according to the prevailing winds, this could reflect enrichment from the combustion of coal at the Torrevaldaliga power plant. Comparing data with the literature, As in marine sediments show a ratio of 0.7 in the tissues of P. lividus from the Civitavecchia area. These results were also compared to those found in P. lividus in an environmental biomonitoring program currently ongoing to control the emissions from the coal-fired power plant in Torrevaldaliga Nord, highlighting a substantial quantitative correspondence. In view of the presence of various industrial activities in the study area that can influence the enrichment of these elements, this work emphasizes the need for performing further studies aimed at assessing the actual contribution of anthropogenic activities even when the background concentrations in marine sediments and marine organisms are high, because burning coal is considered the major anthropogenic source of many trace elements especially As.

Metabolic activity variations in the sea urchins (Paracentrotus lividus) treated with magnesium and subjected to handling stress and aerial exposure

This study assessed the impact of the use of magnesium chloride as a relaxant for the echinoid Paracentrotus lividus on the metabolic activity of individuals subjected to handling stress and aerial exposure. The variation in the gonad moisture content and biochemical composition was compared in sea urchins (P. lividus) treated with magnesium and untreated controls before transport and during 15 days of laboratory acclimation. Sea urchins treated with magnesium maintained higher levels of protein and carbohydrate throughout the trial in comparison with controls. However, the lipid level and fatty acid percentage remained stable during the experiment and no differences were found between treated or non-treated sea urchins .

Sequential toxicity identification evaluation (TIE) for characterizing toxicity of Venice Lagoon sediments: Comparison of two different approaches

A toxicity identification evaluation phase-I (TIE-1) procedure was carried out on five pore water samples extracted from sediments of the Venice Lagoon previously investigated to assess both chemical contamination and toxic effects on the biota. Two different sequential TIE procedures were tested. A first sequence (TIE-1) provided for adding Na 2S 2O 3, adding Na-EDTA, filtering, elution through a C18-SPE column and removing ammonia using the macroalgae Ulva rigida Agardh 1823, while a second procedure (TIE-2) was set up using U. rigida treatment for ammonia removal as first step, keeping unchanged the sequence of the other manipulations. Two different exposure time to the macroalgae were tested (3-h and 15-h). Sperm-cell toxicity test with the echinoid Paracentrotus lividus and embryotoxicity tests with the bivalves Mytilus galloprovincialis and Crassostrea gigas were performed on pore-water samples to assess the effect of the sequential treatments on the overall toxicity. The results confirmed that ammonia contribution to toxicity is strong in most of the samples and that metals, specially Cu, are of concern at least in three sites. The TIE-2 procedure provided more reliable results for the samples characterized by high ammonia contribution to the overall toxicity, whereas the results of TIE-1 and TIE-2 were equivalent for the samples where ammonia contribution was not prevailing. Chemical analyses and test results showed that a 3-h U. rigida exposure is suitable to remove ammonia toxicity minimizing potential metal up-take.

Characterization of the bacterial communities associated with the bald sea urchin disease of the echinoid Paracentrotus lividus

The microbial communities involved in the bald sea urchin disease of the echinoid Paracentrotus lividus are investigated using culture-independent techniques. Lesions of diseased specimens from two locations in France, La Ciotat (Mediterranean Sea) and Morgat (Atlantic Ocean), are examined by Scanning Electron Microscopy (SEM) and the diversity of their microbiota is analysed by Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rRNA gene clones libraries construction. Microscopic observations demonstrated that only the central area of the lesions is invaded by bacteria but not the peripheral zone and the surrounding healthy tissues. Molecular analysis identified at least 24 bacterial genomospecies in bald sea urchin lesions: 5 are Alphaproteobacteria, 10 are Gammaproteobacteria, 8 are CFB bacteria and 1 is a Fusobacteria. Out of them, 4 are observed in both locations while 10 occur only in the Atlantic Ocean and 10 only in the Mediterranean Sea. Gammaproteobacteria are the most represented in clones libraries from both locations, with respectively 65% and 43% of the total clones. CFB and Alphaproteobacteria accounted for the majority of the remaining clones and were detected by DGGE in virtually all samples from both stations. Our results demonstrate that bacterial communities observed on diseased individuals of the same echinoid species but originating from distinct locations are not similar and thus support the hypothesis that bacteria involved in the worldwide echinoid disease commonly called the bald sea urchin disease are opportunistic and not specific.

Developing Toxicity Scores for Embryotoxicity Tests on Elutriates with the Sea Urchin Paracentrotus lividus, the Oyster Crassostrea gigas, and the Mussel Mytilus galloprovincialis

Bioassays are routinely employed for sediment quality assessment. In order to be able to effectively use Bioassays responses in regulatory and management frameworks, toxicity scores, which rank toxicity data in defined classes that are continuous and difficult to interpret, should be reliable and suitable tools to support decisions about the presence or absence of toxicity in tested samples and on how toxic a sample is. A statistical approach is needed to define thresholds for toxicity scores. The Minimum Significance Difference (MSD) criterion allowed the evaluation of toxicity thresholds for each test-matrix and organism pair, based on large sets of experimental data. The MSD values were normalized with respect to the control, ranked in ascending order, and the 90th percentile was identified; the Toxicity Threshold (TT) was calculated by subtracting the 90th percentile from 100 and the Toxicity Limit (TL) was estimated as the percentage of control response multiplied by TT. Taking into account sample responses normalized with respect to control (S), when S > TL, the sample is considered nontoxic; when S <or= TL, toxicity is statistically present. The MSD criterion was applied on a dataset of results from both published and ongoing projects using the validated embryotoxicity tests with the echinoid Paracentrotus lividus, the oyster Crassostrea gigas, and the mussel Mytilus galloprovincialis, on elutriates from sediments of the Venice Lagoon. Once the threshold defining presence or absence of toxicity had been calculated, four other toxicity classes were developed: low (for toxicity data expressed as percentage of effect), medium, high, and very high toxicity (for toxicity data expressed as TU50).

The tube feet of sea urchins and sea stars contain functionally different mutable collagenous tissues

Echinoderms possess mutable collagenous tissues (MCTs), which are capable of undergoing rapid changes in their passive mechanical properties mediated by secretions from a specific cell type, the juxtaligamental cell. In this study, the possible presence of MCTs in the tube feet of the echinoid Paracentrotus lividus and the asteroid Marthasterias glacialis was investigated by measuring their extensibility, tensile strength, stiffness and toughness after different treatments known to influence the physiological state of MCTs. Calcium removal reversibly induced a significant plasticization of the tube feet of both species. When exposed to cell-disrupting solutions, the tube foot stem of sea urchins and sea stars showed a significant increase in strength, stiffness and toughness in the absence of calcium. This response, combined with the ultrastructural observation of juxtaligamental-like cells in the connective tissue, confirms that an MCT is present in both echinoid and asteroid tube feet. It was observed, however, that the tube foot stems of P. lividus and M. glacialis are affected differently by exposure to cell-disrupting solutions in the presence of calcium, indicating that their MCTs could be functionally different. In their soft state, MCTs could assist the muscles in tube foot protraction, bending and retraction; in their stiff state, they could play a role in the energy-sparing maintenance of position; for example, during strong attachment to the substratum to resist hydrodynamically generated loads.

The aboral ring and the development of early gonads in the echinoid Paracentrotus lividus (Echinodermata, Echinoidea)

Abstract. The development of the genital apparatus is described for the echinoid Paracentrotus lividus. This apparatus derives from the aboral ring, an annular structure that includes an inconspicuous coelom and, in juveniles, the germinal rachis. The germinal epithelium grows out from the germinal rachis, and the gonadal wall and coelom in early (tubular) gonads share similarities with their equivalents in the aboral ring. The original germinal rachis regresses to form a genital cord one cell wide in late juveniles. A genital cord was observed in a few field‐collected adult individuals (&gt;40 mm test diameter).

Local population disappearance follows (20 yr after) cycle collapse in a pivotal ecological species

Populations of the echinoid Paracentrotus lividus have undergone spectacular population fluctuations over the last 40 yr at Lough Hyne, SW Ireland, Censuses in 2000 and 2001, reported here, show no individuals present in the South Basin of Lough Hyne, for what is believed to be, the first time since observations began in the late 1920s. As with many echinoids, R lividus was considered to have a pivotal role in benthic ecology through control of algae by grazing, The discontinuation of P. lividus in South Basin of Lough Hyne is significant for 3 reasons. First, the database was 1 of the longest running censuses of a discrete echinoid population anywhere, Second, some corresponding environmental and population size structure data had been recorded over several decades. Third, P lividus was very important in structuring the shallow benthic community of the oldest marine reserve in Europe.

Effects of PCBs on Reactive Oxygen Species (ROS) Production by the Immune Cells of Paracentrotus lividus (Echinodermata)

The impact of four PCB congeners: 3,3 ′,4,4 ′-tetrachlorobiphenyl (IUPAC congener #77), 3,3 ′,4,4 ′,5-pentachlorobiphenyl (IUPAC #126), 2,2 ′,4,4 ′,5,5 ′-hexachlorobiphenyl (IUPAC #153) and 3,3 ′,4,4 ′,5,5 ′-hexachlorobiphenyl (IUPAC #169) was investigated on the reactive oxygen species (ROS) production by coelomocytes of the echinoid Paracentrotus lividus, an important species in marine benthic ecosystems. PCBs were found to increase ROS production and to delay the time of peak production. These effects were stronger on bacteria-stimulated cells and were congener-specific: coplanar congeners (#77, 126 and 169) had more effect than the non-coplanar PCB #153. Among coplanar congeners, PCB #169 showed dose-dependent effects whereas PCB #77 and 126 were more toxic at high and low doses, respectively. The relative immunotoxicity of the different PCB congeners is discussed in the light of their structural properties and biological affinities.

Effects of delayed metamorphosis and food rations on the perimetamorphic events in the echinoid Paracentrotus lividus (Lamarck, 1816) (Echinodermata)

Effect of delayed metamorphosis and food ration on late (competent) larvae and postlarvae of Paracentrotus lividus were investigated. Metamorphosis of competent larvae was either not delayed or delayed from 1 up to 4 days. Larvae were starved or submitted to two different food rations of the algal species Phaeodactylum tricornutum. Larvae during the prolonged competence period and the resulting postlarvae were characterised by: (1) the size of the larval body, (2) the size of the rudiment, (3) the rate of metamorphosis, (4) the size of postlarvae 24 h after metamorphosis, (5) the rate of opening of mouth and anus, (6) the rate of survival, and (7) the growth rate of early postmetamorphic individuals. Both the width of the larval body and the diameter of the echinus rudiment grew in competent larvae that were fed. Unfed larvae did not grow. There was no significant difference in growth between the two food rations. The rate of metamorphosis was higher with larvae that metamorphosed soon after they became competent. Lower capacity of larvae to metamorphose during the delay period was associated with treatments yielding a greater larval width and rudiment diameter during the same period. Postlarval development was affected by a delayed metamorphosis treatment inflicted on competent larvae before metamorphosis. Acquisition of exotrophy happened earlier in postlarvae issued from prolonged competent larvae whatever the larval food rations. The delay treatment negatively affected the development of the digestive tract though it positively affected the growth of early postmetamorphic individuals during the first 6 days following metamorphosis. However, selective mortality occurred afterwards as bigger individuals died preferentially.

Cultivation of Paracentrotus lividus (Echinodermata: Echinoidea) on extruded feeds: digestive efficiency, somatic and gonadal growth

This study assessed the use of extruded feeds, in the form of pellets, for the growing of echinoid Paracentrotus lividus within a closed-culture system. Two feed types, one with soya-bean protein, the other with both soya-bean and fish protein were compared with dried Lessonia sp. and fresh Laminaria sp. as food sources. Pellets present a very high conversion efficiency (about 80%) against about 50% for Laminaria and 35% for Lessonia. However, as pellets are less absorbed, somatic growth (SG) is statistically equivalent for the sea urchins fed with pellets and Laminaria between 2 and 2.2% g soma day–1. Sea urchins fed with pellets produced significantly more gonadal tissue in a shorter time, resulting in a gonadal index (GI) twice higher (6.5%) than Laminaria (3%) in the second month of the experiment. Dry Lessonia does not promote gonadal growth (GG). This study shows that extruded feeds are well assimilated by P. lividus and promote both SG and production of gonadal tissue.

Sea temperature variability and Paracentrotus lividus (Echinoidea) population fluctuations

Observations and censi of the echinoid Paracentrotus lividus over 40 y at Lough Hyne marine nature reserve have revealed population fluctuations of &gt;4 orders of magnitude. The P. lividus population has been anomalously low since the mid 1980s. The population age–size structure has also changed considerably and is now dominated by older individuals. Sea temperature is a known and important determinant of spawning (and recruitment) in this species. In certain years sea surface temperatures (SST) may not reach critical values for P. lividus mass-spawning to be triggered. In addition, toxic dinoflagellate blooms may have been responsible for large-scale mortalities within short periods. Years of anomalously low SSTs match the timing of critical decreases in the Lough Hyne P. lividus population. Years with low maximum SSTs coincide with the timing of major El Niňo Southern Oscillation (ENSO) events. We suggest a SST and possibly ENSO link to unfished (Lough Hyne) P. lividus population changes and propose such links as potential aggravating factors in the decline of the fisheries.

Proteins and Saccharides of the Sea Urchin Organic Matrix of Mineralization: Characterization and Localization in the Spine Skeleton

Properties of the echinoderm skeleton are under biological control, which is exerted in part by the organic matrix embedded in the mineralized part of the skeleton. This organic matrix consists of proteins and glycoproteins whose carbohydrate component is specifically involved in the control mechanisms. The saccharide moiety of the organic matrix of the spines of the echinoid Paracentrotus lividus was characterized using enzyme-linked lectin assays (ELLAs). O-glycoproteins, different types of complex N-glycoproteins, and terminal sialic acids were detected. Sialic acids are known to interact with Ca ions and could play an important role in the mineralization process. Some of the carbohydrate components detected by ELLAs as well as two organic matrix proteins (SM30 and SM50) were localized within different subregions of the spine skeleton using field-emission scanning electron microscopy. The mappings show that some of these components are not homogeneously distributed in the different skeletal subregions. For example, some N-glycoproteins were preferentially located in the putative amorphous subregion of the skeleton, whereas some O-glycoproteins were localized in the subregion where skeletal growth is inhibited. These results suggest that the biological control exerted on the skeletal properties can be partly modulated by local differences in the organic matrix composition.

Ultrastructure of Sea Urchin Calcified Tissues after High-Pressure Freezing and Freeze Substitution

The improvements brought by high-pressure freezing/freeze substitution fixation methods to the ultrastructural preservation of echinoderm mineralized tissues are investigated in developing pedicellariae and teeth of the echinoid Paracentrotus lividus. Three freeze substitution (FS) protocols were tested: one in the presence of osmium tetroxide, one in the presence of uranyl acetate, and the last in the presence of gallic acid. FS in the presence of osmium tetroxide significantly improved cell ultrastructure preservation and should especially be used for ultrastructural studies involving vesicles and the Golgi apparatus. With all protocols, multivesicular bodies, suggested to contain Ca2+, were evident for the first time in skeleton-forming cells. FS in the presence of gallic acid allowed us to confirm the structured and insoluble character of a part of the organic matrix of mineralization in the calcification sites of the tooth, an observation which modifies the current understanding of biomineralization control in echinoderms.

Feeding of the spider crab Maja squinado in rocky subtidal areas of the Ría de Arousa (north-west Spain)

The diet of the spider crab, Maja squinado, was studied in the rocky subtidal areas of the Ría de Arousa (Galicia, north-west Spain), by analysing the gut contents of crabs caught in the summer and winter of 1992. The highly diverse diet was made up primarily of macroalgae and benthic invertebrates that were either sessile or had little mobility. The most important prey were the seaweeds Laminariaceae (43% of the frequency of occurrence and 15% of the food dry weight), Corallina spp. (38% and 3%), molluscs [the chiton Acanthochitona crinitus (15% and 1%), the gastropods Bittium sp. (30% and 2%), Trochiidae and others and the bivalve Mytilus sp. (32% and 12%)], echinoderms [the holothurian Aslia lefevrei (32% and 18%) and the echinoid Paracentrotus lividus (16% and 7%)] and solitary ascidians (18% and 6%). The variability in diet composition was determined by the season (Laminariaceae, Corallina spp., P. lividus, Mytilus sp., gastropods and chitons appeared in greater frequency in winter, while the solitary ascidians and A. lefevrei were consumed to a greater extent in summer) in addition to sexual maturity (prey such as Bittium sp. or Trochiidae were more common in juveniles). Moreover, the changes in the food consumption rate were linked primarily to the moult stage. Feeding activity plummeted during the phases immediately preceding and following ecdysis (stages D0–D3–4 and A), and the diet was less diverse during these phases. No feeding differences were found that could be linked to sex. The composition of the diet of Maja squinado appears to be determined by the seasonal abundance of the different prey in subtidal rocky areas and by their availability (depending on their behavioural and anatomical characteristics, mainly mobility and the presence of hard external structures). Moreover, life history factors have little importance in the variability of the diet composition and only the moult cycle has a considerable effect on feeding rate.

Ultrastructural localization of proteins involved in sea urchin biomineralization.

Three skeletal tissues of the adult echinoid Paracentrotus lividus (the pedicellaria primordium, the test, and the tooth) were immunolabeled with three sera raised against the total mineralization organic matrix and two specific matrix proteins (SM30 and SM50) from the embryo of the echinoid Strongylocentrotus purpuratus. Two conventional chemical fixation protocols and two high-pressure freezing/freeze-substitution protocols were tested. One conventional protocol is recommended for its good preservation of the ultrastructure, and one high-pressure freezing/freeze-substitution protocol is recommended for its good retention of antigenicity. Immunolabeling was obtained in the three adult tissues. It was confined to the active skeleton-forming cells and to the structured organic matrix. The results indicate that the matrix proteins follow the classical routes of secretory protein assembly and export and suggest that SM30 and SM50 are a part of the tridimensional network formed by the organic matrix before the onset of mineralization. They show that the genetic program of part of skeletogenesis is conserved among different calcification models and developmental stages.

Reproductive cycle of the echinoid Paracentrotus lividus: analysis by means of the maturity index

Summary The gonad and maturity index cycles of the echinoid Paracentrotus lividus and their relations with environmental abiotic parameters are assessed after 2 years of observation in southern Brittany, France. The gonadal cycle is briefly described and eight gonadal stages are characterized. The annual cycle, the time of spawning and the period of gonadal growth are well established, suggesting they are controlled externally. The reproductive cycle has three main phases: the growing phase (late autumn and winter) when gonads accumulate reserve material; the maturation phase (spring and early summer) in which gametogenesis then spawning take place; and the spent/regenerating phase when relict gametes are resorbed by the nutritive phagocytes, the gonads being virtually devoid of sexual cells. The maturity index based on the histological diagnosis of gonads and the use of circular data and polar graphical representation make it possible to reliably determine the spawning period, the rate of gametogenesis and the synchronization of males and females among the echinoid population. From this analysis, we can reasonably say that the gonadal cycle (represented by the gonad index), the rate of gametogenesis, and the end of the spawning period are influenced by temperature whereas the first spawning event appears to be triggered by day length.