The multistressor effect of pH reduction, microplastic and lanthanum on sea urchin Arbacia lixula.

pH reduction (Low pH), microplastic (MP), and lanthanum (La) are substantial stressors due to their increasing trends in marine ecosystems and having adverse effects on marine species. This study investigates the single and combined effects of those stressors (Low pH: 7.45, polyethylene MP: 26 µg L-1, and La: 9 µg L-1) on the physiology and histology of sea urchin Arbacia lixula. Regarding physiological results, while the coelomocytes' quantity was slightly affected by stressors, their viability was significantly affected. The coelomocyte count and viability were suppressed most in Low pH-MP-La treatment. The stressors did not impact the respiration rate. According to the histological examination results, the crypt (villi-like structure) was shorter, and epithelial layers were thinner in single and dual stress treatments like MP, Low pH, Low pH-La, and MP-La. Overall, we suggest that the combination of variable types of those stressors causes negative effects on sea urchin's physiology and histology.

Chromosome-level genome assembly and annotation of the black sea urchin Arbacia lixula (Linnaeus, 1758).

The black sea urchin (Arbacia lixula) is a keystone species inhabiting the coastal shallow waters of the Mediterranean Sea, which is a key driver of littoral communities' structure. Here, we present the first genome assembly and annotation of this species, standing as the first Arbacioida genome, including both nuclear and mitochondrial genomes. To obtain a chromosome-level assembly, we used a combination of PacBio high fidelity (HiFi) reads and chromatin capture reads (Omni-C). In addition, we generated a high-quality nuclear annotation of both coding and non-coding genes, by using published RNA-Seq data from several individuals of A. lixula and gene models from closely related species. The nuclear genome assembly has a total span of 607.91 Mb, being consistent with its experimentally estimated genome size. The assembly contains 22 chromosome-scale scaffolds (96.52% of the total length), which coincides with its known karyotype. A total of 72,767 transcripts were predicted from the nuclear genome, 24,171 coding, and 48,596 non-coding that included lncRNA, snoRNA, and tRNAs. The circularized mitochondrial genome had 15740 bp comprising 13 protein-coding genes, 2 rRNA, and 22 tRNA. This reference genome will enhance ongoing A. lixula studies and benefit the wider sea urchin scientific community.

Does the righting behaviour effectively reflect stress in Arbacia dufresnii Arbacioida: Arbaciidae)? / ¿El comportamiento de enderezamiento refleja efectivamente el estrés en Arbacia dufresnii (Arbacioida: Arbaciidae)?

Resumen Introducción: El comportamiento de enderezamiento se ha utilizado como indicador de salud en respuesta a variables estresantes. La aplicación de este parámetro en acuicultura podría ser beneficiosa para reducir la mortalidad y mejorar el bienestar en el cultivo del erizo de mar Arbacia dufresnii. Objetivo: El objetivo de este estudio fue evaluar el efecto del sexo, el diámetro y tres factores estresantes sobre el comportamiento de enderezamiento del erizo de mar A. dufresnii. Métodos: Se midieron un total de 300 animales para evaluar el tiempo de comportamiento de enderezamiento completo (CRB) y 100 de ellos también registraron el tiempo de comportamiento de enderezamiento medio (HRB). Se aplicaron tres factores estresantes a los animales: repeticiones seriadas (tres giros sucesivos), temperatura (shock de 24 horas) e inducción del desove con inyección de KCl. El tiempo se midió con un cronómetro y el diámetro con un calibre de precisión. Resultados: El tiempo de enderezamiento resultó ser dependiente del diámetro, pero independiente del sexo. El límite superior de temperatura de 19 °C tuvo un efecto significativo en el comportamiento de enderezamiento en comparación con las temperaturas de 16 °C y 13 °C, con tiempos de CRB de hasta 150 segundos. Las repeticiones seriadas y el desove no tuvieron un efecto significativo. Sin embargo, con base en los tiempos registrados, se puede deducir que el desove tuvo un impacto en la salud de los animales con tiempos de CRB de hasta 150 segundos en comparación con el control, con tiempos inferiores. Conclusiones: El comportamiento de enderezamiento completo (CRB) parece ser un indicador óptimo para evaluar la salud y condición del erizo de mar A. dufresnii, sin embargo sería óptimo realizar más ensayos para corroborar el efecto del tratamiento control con respecto al desove.

Temporal dynamics of bacterial populations in recirculating aquaculture systems for sea urchin production / Dinámica temporal de poblaciones bacterianas en sistemas de recirculación para la producción acuícolas de erizo de mar

Abstract Introduction: Sea urchin aquaculture is a rising industry, and in consequence, there is a need to establish optimal culture parameters to ensure the health of the cultured animals. Objective: To evaluate the bacterial counts in the seawater of sea urchin (Arbacia dufresnii) aquaculture recirculating systems (RAS). Methods: The bacteriological water quality of two RAS containing sea urchins was determined. For approximately two months, weekly water samples were taken. The bacteriological quality was determined by counting total aerobic heterotrophic populations, lactic acid bacteria, enterobacterias and genus Vibrio. Physicochemical parameters were also measured. Results: There was no presence of disease or mortality. Enterobacteria and lactic acid bacteria were not detected from both RAS systems. The number of animals had an important effect on the observed difference in the count of total bacteria and Vibrio spp. In RAS 1 the maximum counts of total bacteria and Vibrio spp. were 2.8 x 105 ± 1.7 x 105 and 1.45 x 105 ± 3.6 x 104 UFC ml-1, respectively. In RAS 2 total bacteria and Vibrio spp. exhibited repetitive behavior over time influenced in part by water exchange and mainly by feeding. The results indicate that periodic water changes ensure a limited growth of bacterial strains as Vibrio and other bacteria. Conclusions: Our results suggests that the bacterial count levels recorded in this study can be used as a threshold or safety limit for Arbacia dufresnii aquaculture.

Resumen Introducción: La acuicultura de erizos de mar es una industria en auge, y en consecuencia, existe la necesidad de establecer los parámetros de cultivo óptimos para garantizar la salud de los animales en cultivo. Objetivo: Evaluar los recuentos bacterianos en el agua de cultivo de los sistemas de recirculación acuícola (RAS) de erizo de mar Arbacia dufresnii. Métodos: Se determinó la calidad bacteriológica del agua de cultivo de dos RAS que contenían erizos de mar. Durante aproximadamente dos meses, se tomaron muestras de agua semanalmente. La calidad bacteriológica se determinó realizando recuento de las poblaciones heterótrofas aerobias totales, bacterias ácido lácticas, enterobacterias y bacterias del género Vibrio. También se midieron parámetros fisicoquímicos. Resultados: No se observaron patologías ni mortalidad. No se detectaron enterobacterias ni bacterias del ácido láctico en ninguno de los sistemas RAS. El número de animales cultivados tuvo un efecto importante en la diferencia observada en el recuento de bacterias totales y Vibrio spp. En el RAS 1 los recuentos máximos de bacterias totales y Vibrio spp. fueron 2.8 x 105 ± 1.7 x 105 y 1.45 x 105 ± 3.6 x 104 UFC ml-1, respectivamente. En RAS 2 los recuentos de bacterias totales y Vibrio spp. exhibieron un comportamiento repetitivo en el tiempo influenciado en parte por el recambio de agua y principalmente por la alimentación. Los resultados indican que los cambios periódicos de agua aseguran un crecimiento limitado de cepas bacterianas como Vibrio y otras bacterias. Conclusiones: Nuestros resultados sugieren que los niveles de recuento bacteriano registrados en este estudio pueden usarse como umbral o límite de seguridad para la acuicultura de Arbacia dufresnii.

Fitorremediación de efluentes acuícolas mediante el uso de seis microalgas marinas: aportes de sustentabilidad en la industria acuícola del erizo de mar en Argentina / Phytoremediation of aquaculture effluents through the use of six marine microalgae: sustainability contributions in the sea urchin aquaculture industry in Argentina

Resumen Introducción: La industria acuícola está en constante crecimiento, registrando una producción mundial de casi 88 millones de toneladas para el año 2020. Esta industria trae consigo problemas ambientales si sus efluentes no son debidamente tratados. En el 2020, se constituyó la primera empresa de base tecnológica del CONICET en la Patagonia Argentina cuyo propósito es la producción acuícola del erizo verde de mar, Arbacia dufresnii con la finalidad de elaborar una gama de productos nutracéuticos. Su sistema de cultivo conlleva un compromiso de sustentabilidad desde su creación, y sin embargo genera efluentes con niveles altos de nitratos y fosfatos. Objetivo: Ante este escenario, y valorizando la biorremediación como herramienta de tratamiento de aguas, se propone en este trabajo la utilización de las microalgas marinas como agentes fitorremediadores del efluente acuícola. Métodos: Se utilizaron las microalgas Chaetoceros gracilis, Navicula sp., Tetraselmis suecica., Rhodomona salina., Nanochloropsis galvana y Cylindrotheca closterium, las cuales son usadas como alimento de las larvas del erizo en el proceso productivo. Se diseñó un experimento que compara el crecimiento microalgal y la capacidad de remoción de los nutrientes en el efluente en contraste con el medio de cultivo artificial actualmente usado en el ciclo productivo. Resultados: Es posible remediar el efluente de la industria acuícola mediante las microalgas seleccionadas, con porcentaje de eficacia de remoción del 100 % del nitrato y un porcentaje de eficacia de remoción promedio de 50 % para todas las microalgas testeadas. Asimismo, se obtuvieron valores de biomasa microalgal significativamente mayores cuando el cultivo fue realizado en el efluente respecto del cultivo en el medio artificial. Conclusiones: Los avances en investigación proporcionados en este trabajo ponen de manifiesto que es posible el aprovechamiento de un descarte para cultivar las microalgas, incluso mejorando la productividad microalgal para su uso como alimento, disminuyendo los costos involucrados en el sector de producción microalgal cambiando el uso del tipo de medio de cultivo actual (F/2) por el proveniente de un descarte. Estos avances si son escalados y validados, pueden mejorar los estándares de sustentabilidad de la industria en el marco de una economía circular.

Abstract Introduction: The aquaculture industry is constantly growing, registering a global production of almost 88 million tonnes by 2020. This industry brings environmental problems if its effluents are not properly treated. In 2020, the first technology-based company of CONICET was established in Argentine Patagonia whose purpose is the aquaculture production of the green sea urchin, Arbacia dufresnii to develop a range of nutraceutical products. Its cultivation system entails a commitment to sustainability since its creation, and yet it generates effluents with high levels of nitrates and phosphates. Objective: Given this scenario, and valuing bioremediation as a water treatment tool, the use of marine microalgae as phytoremediating agents of aquaculture effluent is proposed in this work. Methods: The microalgae Chaetoceros gracilis, Navicula sp., Tetraselmis suecica, Rhodomona salina, Nanochloropsis galvana and Cylindrotheca closterium were use; which are used as food for sea urchins larvae in the production process. An experiment was designed that compares the microalgal growth and the removal capacity of nutrients in the effluent in contrast to the artificial culture medium currently used in the production cycle. Results: It is possible to remedy the aquaculture industry's effluent by employing the selected microalgae, with a percentage of removal efficiency of 100 % of the nitrate and an average removal efficiency percentage of 50 % for all the microalgae tested. Likewise, significantly higher microalgal biomass values were obtained when the culture was carried out in the effluent the culture in the artificial environment. Conclusions: The advances in research provided in this work show that it is possible to take advantage of a discard to cultivate microalgae, even improving microalgal productivity for use as food, reducing the costs involved in the microalgal production sector by changing the use of the type of current culture medium (F/2) for that from a current discard. These advances, if scaled and validated, can improve industry sustainability standards within the framework of a circular economy.

Effects of artificial light at night on the feeding behaviour of three marine benthic grazers from the Adriatic Sea are species-specific and mostly short-lived.

Artificial light at night (ALAN) has the potential to change the day-night activity of marine benthic grazers, and can therefore alter the top-down control they exert on macroalgal communities. In laboratory experiments, we investigated the influence of three realistic ALAN regimes on food consumption and feeding rhythmicity in the sea urchins Arbacia lixula and Paracentrotus lividus as well as in the snail Cerithium spp. from the Adriatic Sea. Food consumption was assessed in assays with algal pellets, while feeding rhythms were documented with 24 h time-lapse photography. Both was done in ALAN-acclimated and in non-acclimated animals. We observed temporary and potential long-term changes in the feeding rhythms of Cerithium spp. and Paracentrotus lividus, respectively, but found no lasting influence of ALAN on consumption rates. Effects were weaker when ALAN was applied only part-night, which suggests a possible mitigation measure to reduce the impact of nighttime lighting on coastal ecosystems.

Simultaneous recording of multiple cellular signaling events by frequency- and spectrally-tuned multiplexing of fluorescent probes.

Fluorescent probes that change their spectral properties upon binding to small biomolecules, ions, or changes in the membrane potential (Vm) are invaluable tools to study cellular signaling pathways. Here, we introduce a novel technique for simultaneous recording of multiple probes at millisecond time resolution: frequency- and spectrally-tuned multiplexing (FASTM). Different from present multiplexing approaches, FASTM uses phase-sensitive signal detection, which renders various combinations of common probes for Vm and ions accessible for multiplexing. Using kinetic stopped-flow fluorimetry, we show that FASTM allows simultaneous recording of rapid changes in Ca2+, pH, Na+, and Vm with high sensitivity and minimal crosstalk. FASTM is also suited for multiplexing using single-cell microscopy and genetically encoded FRET biosensors. Moreover, FASTM is compatible with optochemical tools to study signaling using light. Finally, we show that the exceptional time resolution of FASTM also allows resolving rapid chemical reactions. Altogether, FASTM opens new opportunities for interrogating cellular signaling.

Blue growth: Sea urchin sustainable aquaculture, innovative approaches / Crecimiento azul: acuicultura sostenible de erizos de mar, enfoques innovadores

Introduction: "Blue Economy" refers to ocean-based economies with a sustainable approach. It focuses in smaller carbon footprints and efficiency, principles that can be applied to aquaculture. However, it has been difficult to develop successful blue economy projects in sea urchin aquaculture. Objective: To compare URCHINOMICS (Norway) and ARBACIA (Argentina), two aquaculture projects with different business models. Methods: We used publicly available information to compare both companies on the basis of their value proposition and tensions (e.g. cultural, social economic and technological). Results: To be successful, sea urchin aquaculture requires development of appropriate technology, open innovation and cooperation of people with different academic, business and organizational backgrounds. Conclusion: The ultimate success of these and similar companies will depend on free interaction of experts from multiple fields and on technological innovation.

Introducción: "Economía azul" se refiere a las economías basadas en el océano con un enfoque sostenible. Se enfoca en menores huellas de carbono y eficiencia, principios que se pueden aplicar a la acuicultura. Sin embargo, ha sido difícil desarrollar proyectos exitosos de economía azul en la acuicultura de erizos de mar. Objetivo: Comparar URCHINOMICS (Noruega) y ARBACIA (Argentina), dos proyectos de acuicultura con diferentes modelos de negocio. Métodos: Utilizamos información disponible públicamente para comparar ambas empresas sobre la base de su propuesta de valor y tensiones (por ejemplo, culturales, socioeconómicas y tecnológicas). Resultados: Para tener éxito, la acuicultura de erizos de mar requiere el desarrollo de tecnología adecuada, innovación abierta y cooperación de personas con diferentes antecedentes académicos, empresariales y organizativos. Conclusión: El éxito final de estas y otras empresas similares dependerá de la libre interacción de expertos de múltiples campos y de la innovación tecnológica.

Copper oxide nanoparticles induce the transcriptional modulation of oxidative stress-related genes in Arbacia lixula embryos.

Copper oxide nanoparticles (CuO NPs) are widely used in various industrial applications, i.e. semiconductor devices, batteries, solar energy converter, gas sensor, microelectronics, heat transfer fluids, and have been recently recognized as emerging pollutants of increasing concern for human and marine environmental health. Therefore, the toxicity of CuO NPs needs to be thoroughly understood. In this study, we evaluated the potential role of oxidative stress in CuO NP toxicity by exploring the molecular response of Arbacia lixula embryos to three CuO NP concentrations (0.7, 10, 20 ppb) by investigating the transcriptional patterns of oxidative stress-related genes (catalase and superoxide dismutase) and metallothionein, here cloned and characterized for the first time. Time- and concentration-dependent changes in gene expression were detected in A. lixula embryos exposed to CuO NPs, up to pluteus stage (72 h post-fertilization, hpf), indicating that oxidative stress is one of the toxicity mechanisms for CuO NPs. These findings provide new insights into the comprehension of the molecular mechanisms underlying copper nanoparticle toxicity in A. lixula sea urchin and give new tools for monitoring of aquatic areas, thus corroborating the suitability of this embryotoxicity assay for future evaluation of impacted sites.

Food Modulation Controls Astaxanthin Accumulation in Eggs of the Sea Urchin Arbacia lixula.

The carotenoid astaxanthin has strong antioxidant properties with beneficial effects for various degenerative diseases. This carotenoid is produced by some microalgae species when cultivated in particular conditions, and, interestingly, it is a predominant carotenoid in aquatic animals throughout a broad range of taxa. Recently, astaxanthin was detected in the eggs of the sea urchin Arbacia lixula in relevant concentrations when this organism was maintained in culture. These results have paved the way for deeper research into astaxanthin production by this species, particularly in regards to how astaxanthin production can be modulated by diet. Results showed that the highest content of astaxanthin in eggs was observed in sea urchins fed on a diet enriched with Spirulina platensis. This result was confirmed by the high antioxidant activity recorded in the egg extracts of these animals. Our results suggest that (i) the sea urchin A. lixula is able to synthesize astaxanthin from precursors obtained from food, and (ii) it is possible to modulate the astaxanthin accumulation in sea urchin eggs by modifying the proportions of different food ingredients provided in their diet. This study demonstrates the large potential of sea urchin cultivation for the eco-sustainable production of healthy supplements for nutraceutical applications.

Size, growth, and density data for shallow-water sea urchins from Mexico to the Aleutian Islands, Alaska, 1956-2016.

Size, growth, and density have been studied for North American Pacific coast sea urchins Strongylocentrotus purpuratus, S. droebachiensis, S. polyacanthus, Mesocentrotus (Strongylocentrotus) franciscanus, Lytechinus pictus, Centrostephanus coronatus, and Arbacia stellata by various workers at diverse sites and for varying lengths of time from 1956 to present. Numerous peer-reviewed publications have used some of these data but some data have appeared only in graduate theses or the gray literature. There also are data that have never appeared outside original data sheets. Motivation for studies has included fisheries management and environmental monitoring of sewer and power plant outfalls as well as changes associated with disease epidemics. Studies also have focused on kelp restoration, community effects of sea otters, basic sea urchin biology, and monitoring. The data sets presented here are a historical record of size, density, and growth for a common group of marine invertebrates in intertidal and nearshore environments that can be used to test hypotheses concerning future changes associated with fisheries practices, shifts of predator distributions, climate and ecosystem changes, and ocean acidification along the Pacific Coast of North America and islands of the north Pacific. No copyright restrictions apply. Please credit this paper when using the data.

Comparative toxicity of seven rare earth elements in sea urchin early life stages.

The widespread use of rare earth elements (REEs) in a number of technological applications raises unanswered questions related to REE-associated adverse effects. We have previously reported on the multiple impact of some REEs on the early life stages of the sea urchin Paracentrotus lividus. The present investigation was to evaluate REE toxicity to early life stages in two unrelated sea urchin species, Sphaerechinus granularis and Arbacia lixula. The comparative toxicities were tested of seven REEs, namely yttrium, lanthanum, cerium, neodymium, samarium, europium and gadolinium as chloride salts at concentrations ranging from 10-7 to 10-4 M. The evaluated endpoints included developmental defects and cytogenetic anomalies in REE-exposed embryos/larvae, and decreased fertilization success and offspring damage following sperm exposure. The results showed different toxicity patterns for individual REEs that varied according to test species and to treatment protocol, thus showing toxicity scaling for the different REEs. Further, the observed effects were compared with those reported for P. lividus either following embryo or sperm exposures. S. granularis showed a significantly higher sensitivity both compared to A. lixula and to P. lividus. This study provides clear-cut evidence for distinct toxicity patterns among a series of REEs. The differences in species sensitivity at micromolar REE levels may warrant investigations on species susceptibility to impacts along polluted coasts.

Volume regulation of intestinal cells of echinoderms: Putative role of ion transporters (Na(+)/K(+)-ATPase and NKCC).

Echinoderms are exclusively marine osmoconformer invertebrates. Some species occupy the challenging intertidal region. Upon salinity changes, the extracellular osmotic concentration of these animals also varies, exposing tissues and cells to osmotic challenges. Cells and tissues may then respond with volume regulation mechanisms, which involve transport of ions and water into and/or out of the cells, through ion transporters, such as the Na(+)/K(+)-ATPase and NKCC. The goal of this study was to relate the cell volume regulation capacity of echinoderm intestinal cells Na(+)/K(+)-ATPase and NKCC activities, in three echinoderm species: Holothuria grisea, Arbacia lixula, and Echinometra lucunter. Isolated cells of these species displayed some control of their cell volume upon exposure to anisosmotic media (isolated intestinal cells, calcein fluorescence as indicator of volume change), with a distinct higher capacity shown by H. grisea, which did not swell even upon 50% hyposmotic shock. The holothuroid cells showed indirect evidence (effect of furosemide) of the participation of NKCC in this process, with a secretory function, and of a secondary role by the NKA (effect of ouabain). Other mechanisms are probably responsible for this function in the urchins. Variable expression of these transporters, and others not examined here, may to some extent account for the variability in cell volume regulation capacity in echinoderm cells.

TRICAINE METHANESULFONATE (MS-222) SEDATION AND ANESTHESIA IN THE PURPLE-SPINED SEA URCHIN (ARBACIA PUNCTULATA).

The purple-spined sea urchin ( Arbacia punctulata ) is commonly found in shallow waters of the western Atlantic Ocean from the New England area of the United States to the Caribbean. Sea urchins play a major role in ocean ecology, echinoculture, and biomedical research. Additionally, sea urchins are commonly displayed in public aquaria. Baseline parameters were developed in unanesthetized urchins for righting reflex (time to regain oral recumbency) and spine response time to tactile stimulus. Tricaine methanesulfonate (MS-222) was used to sedate and anesthetize purple-spined sea urchins and assess sedation and anesthetic parameters, including adhesion to and release from a vertical surface, times to loss of response to tactile stimulus and recovery of righting reflex, and qualitative observations of induction of spawning and position of spines and pseudopodia. Sedation and anesthetic parameters were evaluated in 11 individuals in three circumstances: unaltered aquarium water for baseline behaviors, 0.4 g/L MS-222, and 0.8 g/L MS-222. Induction was defined as the release from a vertical surface with the loss of righting reflex, sedation as loss of righting reflex with retained tactile spine response, anesthesia as loss of righting reflex and loss of tactile spine response, and recovery as voluntary return to oral recumbency. MS-222 proved to be an effective sedative and anesthetic for the purple-spined sea urchin at 0.4 and 0.8 g/L, respectively. Sodium bicarbonate used to buffer MS-222 had no measurable sedative effects when used alone. Anesthesia was quickly reversed with transfer of each individual to anesthesia-free seawater, and no anesthetic-related mortality occurred. The parameters assessed in this study provide a baseline for sea urchin anesthesia and may provide helpful comparisons to similar species and populations that are in need of anesthesia for surgical procedures or research.

Effect of silver nanoparticles on Mediterranean sea urchin embryonal development is species specific and depends on moment of first exposure.

With the ever growing use of nanoparticles in a broad range of industrial and consumer applications there is increasing likelihood that such nanoparticles will enter the aquatic environment and be transported through freshwater systems, eventually reaching estuarine or marine waters. Due to silver's known antimicrobial properties and widespread use of silver nanoparticles (AgNP), their environmental fate and impact is therefore of particular concern. In this context we have investigated the species-specific effects of low concentrations of 60 nm AgNP on embryonal development in Mediterranean sea urchins Arbacia lixula, Paracentrotus lividus and Sphaerechinus granularis. The sensitivity of urchin embryos was tested by exposing embryos to nanoparticle concentrations in the 1-100 µg L(-1) range, with times of exposure varying from 30 min to 24 h (1 h-48 h for S. granularis) post-fertilisation which corresponded with fertilized egg, 4 cell, blastula and gastrula development phases. The most sensitive species to AgNP was A. lixula with significant modulation of embryonal development at the lowest AgNP concentrations of 1-10 µg L(-1) with high numbers of malformed embryos or arrested development. The greatest impact on development was noted for those embryos first exposed to nanoparticles at 6 and 24 h post fertilisation. For P. lividus, similar effects were noted at higher concentrations of 50 µg L(-1) and 100 µg L(-1) for all times of first exposure. The S. granularis embryos indicated a moderate AgNP impact, and significant developmental abnormalities were recorded in the concentration range of 10-50 µg L(-1). As later post-fertilisation exposure times to AgNP caused greater developmental changes in spite of a shorter total exposure time led us to postulate on additional mechanisms of AgNP toxicity. The results herein indicate that toxic effects of AgNP are species-specific. The moment at which embryos first encounter AgNP is also shown to be an important factor in the development of abnormalities, and future applications of the sea urchin embryo development test for nanoparticle toxicity testing should carefully address the specific phase of development of embryos when nanoparticles are first introduced.

Morphological plasticity in the Aristotle's lantern of Arbacia dufresnii (Phymosomatoida: Arbaciidae) off the Patagonian coast / Plásticidad morfológica en la linterna de Aristoteles en Arbacia dufresnii (Phymosomatoida: Arbaciidae) en la costa Patagónica

Abstract The relative size of the Aristotle's lantern of most sea urchins varies in relation to the food availability and it is often used to infer the availability of food of the environment. The aim of our study was to evaluate the lantern morphology plasticity of Arbacia dufresnii in populations with different environmental characteristics, either mussel beds or disturbed areas, by the invasive alga Undaria pinnatifida along the Patagonian Atlantic coast. The test diameter of the sea urchins along with the weight and height of the lanterns, the jaw lenght and rotula lenght were measured. Classic and geometric morphometric analyses were performed to test differences among populations. The length of the jaw was the best indicator of relative changes in size of the lantern. The largest length of the jaw was measured in individuals from disturbed areas dominated by the invasive algae U. pinnatifida. The rotula shape changed with the increase of the diameter of the sea urchins, it tends to be more elongated with larger sea urchins. Rev. Biol. Trop. 63 (Suppl. 2): 339-351. Epub 2015 June 01.

Resumen El tamaño relativo de la linterna de Aristóteles en la mayoría de las especies de erizos de mar varía en relación con la disponibilidad de alimentos y se utiliza a menudo para inferir la disponibilidad de alimentos en el medio ambiente en que los erizos de mar habitan. El objetivo de este estudio fue evaluar la plasticidad morfológica de la linterna de Aristóteles de Arbacia dufresnii en poblaciones con diferentes características ambientales, ya sean con bancos de mejillones o áreas modificadas por el alga invasora Undaria pinnatífida, a largo de la costa patagónica atlántica. Se midió el diámetro del caparazón, el peso y el alto de las linternas, la longitud de la semipirámide y la longitud de la rótula. Los datos se analizaron utilizando técnicas de morfometría clásica y geométrica con el objetivo de probar diferencias entre las poblaciones. La longitud de la semipirámide fue el mejor indicador para describir los cambios relativos en el tamaño de la linterna. La mayor longitud de la semipirámide se observó en las poblaciones que habitan áreas dominadas por el alga invasora U. pinnatifida. La forma de la semipirámide no varía entre las poblaciones ni con el tamaño de los erizos de mar, mientras que la forma de la rótula cambia en relación al tamaño de los erizos, siendo más alargada cuando el tamaño de los individuos es mayor.

Distribution of sea urchins living near shallow water CO2 vents is dependent upon species acid-base and ion-regulatory abilities.

To reduce the negative effect of climate change on Biodiversity, the use of geological CO2 sequestration has been proposed; however leakage from underwater storages may represent a risk to marine life. As extracellular homeostasis is important in determining species' ability to cope with elevated CO2, we investigated the acid-base and ion regulatory responses, as well as the density, of sea urchins living around CO2 vents at Vulcano, Italy. We conducted in situ transplantation and field-based laboratory exposures to different pCO2/pH regimes. Our results confirm that sea urchins have some ability to regulate their extracellular fluid under elevated pCO2. Furthermore, we show that even in closely-related taxa divergent physiological capabilities underlie differences in taxa distribution around the CO2 vent. It is concluded that species distribution under the sort of elevated CO2 conditions occurring with leakages from geological storages and future ocean acidification scenarios, may partly be determined by quite subtle physiological differentiation.

Interactions of plant stress and herbivory: intraspecific variation in the susceptibility of a palatable versus an unpalatable seaweed to sea urchin grazing.

Interactions among environmental stresses, plant defensive characteristics, and plant nutrient status may significantly affect an alga's susceptibility to herbivores. Following desiccation, the palatable seaweed Gracilaria tikvahiae was less susceptible to grazing by the sea urchin Arbacia punctulata while the unpalatable alga Padina gymnospora became more susceptible. Increased grazing on desiccated Padina appeared to result from a loss of chemical defenses following desiccation. Palatable plants treated with organic extracts from desiccated Padina plants were consumed at more than twice the rate of plants treated with extracts from undesiccated plants. Increased susceptibility of Padina did not correlate with changes in protein content of the alga; reduced grazing on desiccated Gracilaria was associated with a decrease in protein content. When Padina was grazed by Arbacia or mechanically damaged to mimic urchin grazing, its susceptibility to Arbacia decreased within 1 to 5 days. These results demonstrate that history of physical or biological stress may affect a plant's susceptibility to herbivory. We hypothesize that urchins cue primarily on attractiveness features (e.g. nutrient content) of highpreference algae and deterrent features (e.g. chemical defenses) of low-preference algae. Stresses may therefore increase, decrease, or not affect a plant's susceptibility to herbivory depending upon the primary feeding cues used by the herbivore, the defensive mechanisms used by the plant, and the way these are altered by various environmental stresses.

Associational plant refuges: convergent patterns in marine and terrestrial communities result from differing mechanisms.

An associational plant refuge occurs when a plant that is susceptible to herbivory gains protection from herbivory when it is associated with another plant. In coastal North Carolina, the abundance of the palatable red alga Gracilaria tikvahiae is positively correlated with the abundance of the unpalatable brown alga Sargassum filipendula during times of increased herbivore activity. To see if grazing by the sea urchin Arbacia punctulata could generate this pattern, controlled experiments were conducted in out-door microcosms and in the laboratory. Gracilaria beneath a canopy of Sargassum was eaten significantly less than Gracilaria alone. When Arbacia were excluded, Gracilaria alone grew significantly more than Gracilaria beneath Sargassum, demonstrating that Sargassum is a competitor of Gracilaria. Experiments investigating Sargassum's deterrent role indicated that Sargassum decreased the foraging range of Arbacia and the rate at which it fed on Gracilaria. Additional experiments with plastic Sargassum mimics indicated that the decreased grazing on Gracilaria was not a result of Sargassum morphology, but was probably attributable to some chemical characteristic of Sargassum. The pattern of increased grazing in monocultures (only Gracilaria present) versus polycultures (both Gracilaria and Sargassum present) demonstrated in this study also has been demonstrated for plant-insect interactions in terrestrial communities. In these communities, insect density is higher in monocultures than in polycultures because insects find and immigrate to monocultures more rapidly, and once in a monoculture, they emigrate from them less often than from polycultures. In this study, urchins did not find and immigrate to monocultures more rapidly, nor did they tend to stay in them once they were found; in fact, they emigrated from monocultures of Gracilaria more rapidly than from Gracilaria and Sargassum polycultures. Increased grazing in Gracilaria monocultures resulted from increased rates of movement and feeding of individual herbivores, not from increased herbivore density as has been reported for terrestrial systems.