Contrasting the development of larval and adult body plans during the evolution of biphasic lifecycles in sea urchins.

Biphasic lifecycles are widespread among animals, but little is known about how the developmental transition between larvae and adults is regulated. Sea urchins are a unique system for studying this phenomenon because of the stark differences between their bilateral larval and pentaradial adult body plans. Here, we use single-cell RNA sequencing to analyze the development of Heliocidaris erythrogramma (He), a sea urchin species with an accelerated, non-feeding mode of larval development. The sequencing time course extends from embryogenesis to roughly a day before the onset of metamorphosis in He larvae, which is a period that has not been covered by previous datasets. We find that the non-feeding developmental strategy of He is associated with several changes in the specification of larval cell types compared to sea urchins with feeding larvae, such as the loss of a larva-specific skeletal cell population. Furthermore, the development of the larval and adult body plans in sea urchins may utilize largely different sets of regulatory genes. These findings lay the groundwork for extending existing developmental gene regulatory networks to cover additional stages of biphasic lifecycles.

From molecules to morphology: How food supply influences the larvae of sea urchins across all levels of biological organization.

An important goal of many studies in molecular ecology is to utilize molecular tools to elucidate how critical traits like metabolism and growth are affected by environmental stressors and how organisms offset these stresses by adaptive molecular-level responses. Stress from food deprivation may be critical for early developmental stages that require a continued supply of substrates for energy metabolism and growth if development is to be completed. In a 'From the Cover' article in this issue of Molecular Ecology, Li et al. (2023) examined the effects of withholding food (unicellular algae) on 10 traits of larvae of the purple sea urchin (Strongylocentrotus purpuratus), ranging from the molecular level (gene expression) to morphology. Overall, this study sheds new light on the plasticity of larval development and the tight linkages that exist among traits as they respond to changes in food availability. Importantly, shifts in the sources of food utilized under different dietary treatments show the plasticity of these larvae to alter reliance on endogenous energy stores and dissolved organic matter (DOM) as algae deprivation continues. The effects of global change on the amounts and phenology of productivity in the seas make this type of integrated, multi-level analysis an important tool for predicting the future states of marine ecosystems.

Effects of macroalgae and sea urchin grazing pressure on zoantharians growth under laboratory conditions.

In the context of ocean warming, thermophilic organisms such as zoantharians are expanding and altering shallow benthic habitats. Here, a four-month laboratory experiment was performed to examine the influence of three types of macroalgae morphotypes common in the Canary Islands (turf algae, Lobophora spp., and crustose coralline algae) on the growth of two zoantharian species, Palythoa caribaeorum and Zoanthus pulchellus. Additionally, the grazing effects of echinoids Diadema africanum and Paracentrotus lividus were assessed as facilitators of substrate colonization by means of controlling macroalgae cover. Colony and algal coverages were measured at the beginning, middle and end of the experiment, and increments were calculated. Results indicated a general decrease in zoantharian colony sizes in contact with different algal types in the absence of sea urchins. However, P. caribaeorum colonies showed significant growth in the presence of D. africanum, highlighting the ecological importance of sea urchins in zoantharian population proliferation and subsequent community modification. This study represents the first investigation into zoantharian-macroalgae interactions under controlled conditions.

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.

Variation of the diet of the sea urchin (Diadema mexicanum (Diadematoida: Diadematidae)) according to its size in the Eastern Tropical Pacific / Variación de la dieta del erizo de mar (Diadema mexicanum (Diadematoida: Diadematidae)) según su tamaño en el Pacífico Tropical Oriental

Abstract Introduction: The sea urchin Diadema mexicanum, due to its bioerosion activity, is considered of ecological importance. This phenomenon could negatively or positively affect coral reef ecosystems. The bioerosion process varies according to the abundance and size of the sea urchin. Objective: Juvenile organisms possess different metabolic needs compared to adults, so knowing their stomach content according to size allows us to quantify the selection of substrate bioeroded. Methods: To determine this, D. mexicanum individuals were collected in 12 sites from January 2009 to September 2010 along the Eastern Tropical Pacific coast. The stomach content was categorized in Carbonated Fraction (CF), Non-Carbonated Fraction (NCF), and Organic Matter (OM). Stomach content was analyzed according to a) juvenile (< 2.5 cm) or adult (> 2.5 cm) stage and b) locality. Results: Juveniles presented the following stomach content average percentages: 20.7 % OM, 12 % NCF and 67.9 % CF; and adults: 11.4 % OM, 14.8 % NCF and 73.8 % CF. Based on a Wilcoxon test and a Kendall linear regression, the following results were obtained. The carbonated fraction in the stomach increased by 0.47 units on average for every cm of growth (p < 0.05). OM consumed by D. mexicanum increases only 0.05 units for every cm of growth (p < 0.05). We found a difference of stomach content depending on the site (p < 0.05) and life stage (p < 0.05). Localities like Huatulco and Coco presented significant differences that could be related to local oceanographic conditions. Conclusions: We relate these changes of the stomach fractions to the necessity of the juvenile sea urchins for nutrients to maintain their growth. The amount of OM is crucial for the development of early stages, meaning that there is a difference in substrate selection associated with growth.

Resumen Introducción: El erizo de mar Diadema mexicanum, por su actividad de bioerosión, es considerado de importancia ecológica. Este fenómeno podría afectar negativa o positivamente a los ecosistemas de arrecifes de coral. El proceso de bioerosión varía según la abundancia y el tamaño del erizo de mar. Objetivo: Los organismos juveniles poseen diferentes necesidades metabólicas en comparación con los adultos, por lo que conocer el contenido estomacal según el tamaño, nos permite cuantificar la selección de sustrato bioerosionado. Métodos: Para determinar esto, se recolectaron individuos de D. mexicanum en 12 sitios desde enero de 2009 hasta septiembre de 2010 a lo largo de la costa del Pacífico Tropical Oriental. El contenido estomacal se clasificó en Fracción Carbonatada (FC), Fracción No Carbonatada (NCF) y Materia Orgánica (MO). El contenido estomacal se analizó según a) estadio juvenil (< 3 cm) o adulto (> 3 cm) y b) localidad. Resultados: Los juveniles presentaron los siguientes porcentajes promedio del contenido estomacal: 20.7 % OM, 12 % NCF y 67.9 % CF; y adultos: 11.4 % OM, 14.8 % NCF y 73.8 % CF. Con base en una prueba de Wilcoxon y una regresión lineal de Kendall, se obtuvieron los siguientes resultados. La fracción carbonatada en el estómago aumentó en promedio 0.47 unidades por cada cm de crecimiento (p < 0.05). La MO consumida por D. mexicanum aumenta solo 0.05 unidades por cada cm de crecimiento (p < 0.05). Encontramos una diferencia en el contenido estomacal según el sitio (p < 0.05) y el estadio de vida (P < 0.05). Localidades como Huatulco y Coco presentaron diferencias significativas que podrían estar relacionadas con las condiciones oceanográficas locales. Conclusiones: Relacionamos estos cambios de la composición porcentual del contenido estomacal con la necesidad de los erizos de mar juveniles de nutrientes para mantener su crecimiento. La cantidad de MO es crucial para el desarrollo de las primeras etapas, lo que significa que existe una diferencia en la selección de sustrato asociada con el crecimiento.

Fatty acid composition and metabolic pathways in Arbacia dufresnii (Arbaciidae: Arbacioida) gametes: implications of shrimp byproducts in aquaculture feeds / Composición de ácidos grasos y vías metabólicas en los gametos de Arbacia dufresnii (Arbaciidae: Arbacioida) implicaciones de los subproductos de langostinos en los alimentos de acuicultura

Abstract Introduction: Care towards nutrition is essential for the quality of a sustainable aquaculture product. Since the balance in food affects the growth and production of gametes. The circular economy is made possible through the use of discarded materials. Objective: The aim of this research was to study the fatty acid composition and metabolic pathways in the gametes of Arbacia dufresnii, with a focus on the implications of incorporating shrimp byproducts into aquaculture feeds. Methods: Four different treatments were designed to maintain optimal nutritional quality, particularly in lipids and proteins, based on previous studies. The fatty acid profiles of the feeds and gametes were analyzed by using gas-chromatography, and statistical analyses were conducted to determine significant differences. Results: Significant differences were observed in the abundance (%) of omega-3 (ω-3) and omega-6 (ω-6) fatty acids. The (ω-3) metabolic pathway was more pronounced in the gametes of wild animals and those fed with the experimental feeds. In contrast, the (ω-6) metabolic pathway was less relevant in these groups. The (ω-3) /(ω-6) ratio was highest in the gametes of wild animals. Feeds enriched in fatty acids enhanced their bioaccumulation in the gametes reaching higher concentrations than wild animals. The availability of fatty acids in foods allowed their bioaccumulation in gametes, with concentrations equal to or higher than those observed in animals in their natural environment for certain fatty acids. Conclusions: Incorporating shrimp byproducts in aquaculture feeds demonstrated a promising strategy for resource utilization and organic input generation. The fatty acid composition in the gametes of A. dufresnii was influenced by the diet, highlighting the potential of balanced feeds to enhance the bioaccumulation of essential fatty acids. These findings provide valuable insights for the development of sustainable aquaculture practices and the production of nutritionally enriched seafood products.

Resumen Introducción: El cuidado hacia la nutrición es fundamental para la calidad de un producto acuícola sostenible. Ya que el balance en los alimentos afecta el crecimiento y producción de los gametos. A partir del aprovechamiento de materias de descarte se posibilita la economía circular. Objetivo: El objetivo de este estudio fue investigar la composición de ácidos grasos y las vías metabólicas en los gametos de Arbacia dufresnii, centrándose en las implicaciones de la incorporación de subproductos de camarones en los alimentos de acuicultura. Métodos: Se diseñaron cuatro tratamientos diferentes para mantener una calidad nutricional óptima, especialmente en lípidos y proteínas, basándose en estudios previos. Se analizaron los perfiles de ácidos grasos de los alimentos y los gametos mediante cromatografía de gases, y se realizaron análisis estadísticos para determinar diferencias significativas. Resultados: Se observaron diferencias significativas en la abundancia (%) de ácidos grasos omega-3 (ω-3) y omega-6 (ω-6). La vía metabólica de (ω-3) fue más pronunciada en los gametos de los animales en su entorno natural y aquellos alimentados con los piensos experimentales. Por el contrario, la vía metabólica de (ω-6) tuvo menos relevancia en estos grupos. La relación (ω-3) /(ω-6) fue más alta en los gametos de los animales en su entorno natural. La disponibilidad de ácidos grasos en los alimentos permitió su bioacumulación en los gametos, con concentraciones iguales o superiores a las observadas en los animales en su entorno natural para ciertos ácidos grasos. Conclusiones: La incorporación de subproductos de camarones en los alimentos de acuicultura demostró ser una estrategia prometedora para la utilización de recursos y la generación de insumos orgánicos. La composición de ácidos grasos en los gametos de A. dufresnii fue influenciada por la dieta, destacando el potencial de los alimentos balanceados para mejorar la bioacumulación de ácidos grasos esenciales. Estos hallazgos brindan información valiosa para el desarrollo de prácticas sostenibles en acuicultura y la producción de productos marinos enriquecidos nutricionalmente.

Ethics and Welfare in invertebrates: a stepping-stone to research and animal production / Ética y bienestar en invertebrados: una piedra fundamental en investigación y producción animal

Abstract Introduction: Even though only a few species are considered to be dangerous, pests or vectors, the majority of invertebrates produce a feeling of aversion in humans. This has contributed to the delay in the development of ethical considerations as regards this group in contrast with vertebrates, with the exception of cephalopods. Objective: In the present study, we provide an overview of the current situation on animal ethics and welfare in order to contribute to the development of a framework for ensuring invertebrate welfare. Methods: Today, animal welfare is multidisciplinary in nature to a very high degree as it includes ethology, physiology, pathology, biochemistry, genetics, immunology, nutrition, cognitive-neural, veterinary medicine, and ethics. Animal welfare is a complex concept, difficult to achieve successfully from one perspective. Results: As a consequence, we propose to include the five domains (nutrition, environment, health, behaviour and mental state) along with the three conceptions (basic health and functioning, affective state and natural living), as well as the 5R Principle (Replace, Reduction, Refinement, Respect and Responsibility) in seeking to achieve a comprehensive welfare state. Conclusions: We consider that in both research and animal production, the individual and collective ethical concerns coexist and, in fact, the main moral concern to account for is the collective one and that, within that collective view, the individual moral concern should be applied with responsibility and respect for the individual. Finally, we propose a practical example of invertebrate welfare production in sea urchin aquaculture with the aim of including animal production of invertebrates in this important discussion.

Resumen Introducción: Aunque sólo unas pocas especies son consideradas peligrosas, plagas o vectores, la mayoría de los invertebrados producen un sentimiento de aversión en el ser humano. Esto ha contribuido al retraso en el desarrollo de consideraciones éticas respecto a este grupo en comparación con los vertebrados, a excepción de los cefalópodos. Objetivo: En el presente trabajo, proporcionamos una visión general de la situación actual en materia de ética y bienestar animal con el fin de contribuir al desarrollo de un marco para garantizar el bienestar de los invertebrados. Métodos: Hoy en día, el bienestar animal es de naturaleza multidisciplinaria en un grado muy alto, ya que incluye etología, fisiología, patología, bioquímica, genética, inmunología, nutrición, cognitivo-neural, medicina veterinaria y ética. El bienestar animal es un concepto complejo, difícil de lograr con éxito desde una sola perspectiva. Resultados: Como consecuencia, proponemos incluir los cinco dominios (nutrición, ambiente, salud, comportamiento y estado mental) junto con las tres concepciones (Salud básica y funcionamiento, estado afectivo y vida natural), así como el Principio 5R (Reemplazar, Reducir, Refinar, Respetar y Responsabilidad) en la búsqueda de alcanzar un estado de bienestar integral. Conclusiones: Consideramos que tanto en la investigación como en la producción animal coexisten las preocupaciones éticas individuales y colectivas y, de hecho, la principal preocupación moral a dar cuenta es la colectiva y que, dentro de esa visión colectiva, se debe aplicar la preocupación moral individual. con responsabilidad y respeto por la persona. Finalmente, proponemos un ejemplo práctico de producción de bienestar de invertebrados en la acuicultura de erizos de mar con el objetivo de incluir la producción animal de invertebrados en esta importante discusión.

Planktonic Duration of the Bryozoan Cyphonautes Larva and Limits on Growth Rate Imposed by Its Form-Limited Maximum Clearance Rate.

AbstractThe form of the cyphonautes larva of bryozoans changes little during development. The ciliated band that generates the feeding current increases nearly in proportion to body length, so that the maximum rate of clearing planktonic food from a volume of water becomes increasingly low relative to body protein. This development is unlike the other larvae that produce a feeding current with bands of simple cilia. The cyphonautes' growth rate has therefore been predicted to be unusually low when food is scarce. As predicted, cyphonautes larvae of a species of Membranipora starved at concentrations of food that supported growth of pluteus larvae. Comparisons between the cyphonautes and plutei of a sand dollar were for growth from first feeding to metamorphosis, with a mix of two algal species. Another comparison was for growth of cyphonautes at an advanced stage and plutei of a regular sea urchin at an early stage, with food in seawater at a reduced concentration. The low maximum clearance rate did not prevent rapid growth and development of some cyphonautes from egg through metamorphosis when food was abundant. Twenty-nine days for development to metamorphosis in the laboratory with abundant food was close to Yoshioka's estimate of larval duration from the time lag between adult zooid density and larval abundance in a population in the Southern California Bight. Despite individual variation in growth rates and other physiological and environmental influences, simple measures of larval form predicted the differences in larval performance: scarce food extended larval duration for the cyphonautes more than for plutei.

The role of spine length in crustacean and fish associations with echinoids at Los Cabos, Baja California Sur, Mexico / El papel de la longitud de la espina en la asociación de crustáceos y peces con equinoideos en Los Cabos, Baja California Sur, México

Introduction: Echinoids (sea urchins) provide shelter for a variety of facultative or obligatory ectosymbionts. Objective: To evaluate the hypothesis that decapods and fishes prefer to associate with echinoid individuals and species that have longer spines. Methods: We visually studied the frequency of decapod crustaceans and fishes associated with echinoids in shallow water (< 4 m) and deeper water (5-20 m) at Los Cabos, Baja California Sur, Mexico, during 1-6 January 2019. Results: We inspected 1 058 echinoids of six species. Five decapod species associated with three species of echinoids. When compared with other echinoid species, in shallow water, decapods associated 5.1 times more often with the longest-spined echinoid Diadema mexicanum (7.0 times more decapods per individual D. mexicanum); in deeper water, association frequency was similar for all echinoid species. Fourteen fish species associated with four echinoid species. In shallow water, fishes associated 2.6 times more with D. mexicanum (4.5 times more fishes per individual). There was no preferred echinoid species in deeper water. Longer-spined D. mexicanum had more decapods and fishes. Associations were more frequent in shallow water. Multiple individuals and species of decapods and fish often associated together with a single D. mexicanum. The decapod that presumably is Tuleariocaris holthuisi showed a possible obligatory association with one of the equinoids (D. mexicanum); the other decapods and all fish species are facultative associates. Conclusion: Our results support the hypothesis that decapods and fishes associate most frequently with echinoids with the longest spines, presumably to reduce the risk of predation.

Introducción: Los equinoideos (erizos de mar) brindan refugio a una variedad de ectosimbiontes facultativos u obligatorios. Objetivo: Evaluar la hipótesis de que los decápodos y los peces prefieren asociarse con individuos y especies de equinoideos con espinas más largas. Métodos: Estudiamos visualmente la frecuencia de crustáceos decápodos y peces asociados con equinoideos en aguas poco profundas (< 4 m) y aguas más profundas (5-20 m) en Los Cabos, Baja California Sur, México, del 1-6 de enero 2019. Resultados: Examinamos 1 058 equinoideos de seis especies. Cinco especies de decápodos se asociaron con tres especies de equinoideos. Al comparar con otras especies de equinoideos, en aguas poco profundas, los decápodos se asociaron 5.1 veces más frecuentemente con la especie de equinoideo de espinas más largas, Diadema mexicanum (7.0 veces más decápodos por individuo en D. mexicanum); en aguas más profundas, la frecuencia fue similar para todas las especies de equinoideos. Catorce especies de peces se asociaron con 4 especies de equinoideos. En aguas poco profundas, los peces se asociaron 2.6 veces más con D. mexicanum (4.5 veces más peces por individuo). No hubo preferencia por una especie de equinoideo en aguas más profundas. Individuos de D. mexicanum con espinas largas tuvieron más asociación con decápodos y peces. Las asociaciones se dieron con mayor frecuencia en aguas poco profundas. Múltiples individuos y especies de decápodos y peces a menudo se asociaron con un solo D. mexicanum. Un decápodo que presumiblemente es Tuleariocaris holthuisi mostró una posible asociación obligatoria con uno de los equinoideos (D. mexicanum); las otras especies de decápodos y todas las especies de peces presentaron asociaciones facultativas. Conclusión: Nuestros resultados apoyan la hipótesis de que los decápodos y los peces se asociaron con mayor frecuencia con los equinoideos con las espinas más largas, presumiblemente para reducir el riesgo de depredación.

Ion Pathways in Biomineralization: Perspectives on Uptake, Transport, and Deposition of Calcium, Carbonate, and Phosphate.

Minerals are formed by organisms in all of the kingdoms of life. Mineral formation pathways all involve uptake of ions from the environment, transport of ions by cells, sometimes temporary storage, and ultimately deposition in or outside of the cells. Even though the details of how all this is achieved vary enormously, all pathways need to respect both the chemical limitations of ion manipulation, as well as the many "housekeeping" roles of ions in cell functioning. Here we provide a chemical perspective on the biological pathways of biomineralization. Our approach is to compare and contrast the ion pathways involving calcium, phosphate, and carbonate in three very different organisms: the enormously abundant unicellular marine coccolithophores, the well investigated sea urchin larval model for single crystal formation, and the complex pathways used by vertebrates to form their bones. The comparison highlights both common and unique processes. Significantly, phosphate is involved in regulating calcium carbonate deposition and carbonate is involved in regulating calcium phosphate deposition. One often overlooked commonality is that, from uptake to deposition, the solutions involved are usually supersaturated. This therefore requires not only avoiding mineral deposition where it is not needed but also exploiting this saturated state to produce unstable mineral precursors that can be conveniently stored, redissolved, and manipulated into diverse shapes and upon deposition transformed into more ordered and hence often functional final deposits.

The Use of Larval Sea Stars and Sea Urchins in the Discovery of Shared Mechanisms of Metazoan Whole-Body Regeneration.

The ability to regenerate is scattered among the metazoan tree of life. Further still, regenerative capacity varies widely within these specific organisms. Numerous organisms, all with different regenerative capabilities, have been studied at length and key similarities and disparities in how regeneration occurs have been identified. In order to get a better grasp on understanding regeneration as a whole, we must search for new models that are capable of extensive regeneration, as well as those that have been under sampled in the literature. As invertebrate deuterostomes, echinoderms fit both of these requirements. Multiple members regenerate various tissue types at all life stages, including examples of whole-body regeneration. Interrogations in two highly studied echinoderms, the sea urchin and the sea star, have provided knowledge of tissue and whole-body regeneration at various life stages. Work has begun to examine regeneration in echinoderm larvae, a potential new system for understanding regenerative mechanisms in a basal deuterostome. Here, we review the ways these two animals' larvae have been utilized as a model of regeneration.

Precise regulation of presenilin expression is required for sea urchin early development.

Presenilins (PSENs) are widely expressed across eukaryotes. Two PSENs are expressed in humans, where they play a crucial role in Alzheimer's disease (AD). Each PSEN can be part of the γ-secretase complex, which has multiple substrates, including Notch and amyloid-ß precursor protein (AßPP) - the source of amyloid-ß (Aß) peptides that compose the senile plaques during AD. PSENs also interact with various proteins independently of their γ-secretase activity. They can then be involved in numerous cellular functions, which makes their role in a given cell and/or organism complex to decipher. We have established the Paracentrotus lividus sea urchin embryo as a new model to study the role of PSEN. In the sea urchin embryo, the PSEN gene is present in unduplicated form and encodes a protein highly similar to human PSENs. Our results suggest that PSEN expression must be precisely tuned to control the course of the first mitotic cycles and the associated intracellular Ca2+ transients, the execution of gastrulation and, probably in association with ciliated cells, the establishment of the pluteus. We suggest that it would be relevant to study the role of PSEN within the gene regulatory network deciphered in the sea urchin.

New techniques for creating parthenogenetic larvae of the sea urchin Lytechinus pictus for gene expression studies.

BACKGROUND: Sea urchins are model organisms for studying the spatial-temporal control of gene activity during development. The Southern California species, Lytechinus pictus, has a sequenced genome and can be raised in the laboratory from egg to egg in 4 to 5 months. RESULTS: Here, we present new techniques for generating parthenogenetic larvae of this species and include a gallery of photomicrographs of morphologically abnormal larvae that could be used for transcriptomic analysis. CONCLUSIONS: Comparison of gene expression in parthenogenotes to larvae produced by fertilization could provide novel insights into gene expression controls contributed by sperm in this important model organism. Knowledge gained from transcriptomics of sea urchin parthenogenotes could contribute to parthenogenetic studies of mammalian embryos.

The nanoscale organization of the Wnt signaling integrator Dishevelled in the vegetal cortex domain of an egg and early embryo.

Canonical Wnt/ß-catenin (cWnt) signaling is a crucial regulator of development and Dishevelled (Dsh/Dvl) functions as an integral part of this pathway by linking Wnt binding to the Frizzled:LRP5/6 receptor complex with ß-catenin-stimulated gene expression. In many cell types Dsh has been localized to ill-defined cytoplasmic puncta, however in sea urchin eggs and embryos confocal fluorescence microscopy has shown that Dsh is localized to puncta present in a novel and development-essential vegetal cortex domain (VCD). In the present study, we used super-resolution light microscopy and platinum replica transmission electron microscopy (TEM) to provide the first views of the ultrastructural organization of Dsh within the sea urchin VCD. 3D structured illumination microscopy (SIM) imaging of isolated egg cortices demonstrated the graded distribution of Dsh in the VCD, whereas higher resolution stimulated emission depletion (STED) imaging revealed that some individual Dsh puncta consisted of more than one fluorescent source. Platinum replica immuno-TEM localization showed that Dsh puncta on the cytoplasmic face of the plasma membrane consisted of aggregates of pedestal-like structures each individually labeled with the C-terminus specific Dsh antibody. These aggregates were resistant to detergent extraction and treatment with drugs that disrupt actin filaments or inhibit myosin II contraction, and coexisted with the first cleavage actomyosin contractile ring. These results confirm and extend previous studies and reveal, for the first time in any cell type, the nanoscale organization of plasma membrane tethered Dsh. Our current working hypothesis is that these Dsh pedestals represent a prepositioned scaffold organization that is important for the localized activation of the cWnt pathway at the sea urchin vegetal pole. These observations in sea urchins may also be relevant to the submembranous Dsh puncta present in other eggs and embryos.

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.

Reproduction of the sea urchin Tripneustes depressus (Camarodonta: Toxopneustidae) in Bahía de La Paz, Baja California Sur, Mexico / Reproducción del erizo de mar Tripneustes depressus (Camarodonta: Toxopneustidae) en Bahía de La Paz, Baja California Sur, México

Introduction: Sea urchin gonads (roe or uni) are considered a culinary delicacy worldwide. However, only a few species are considered edible and commercialized. The sea urchin Tripneustes depressus has generated the interest of producers in Baja California Sur, Mexico, due to the quality of its gonads. A biological basis for designing a management strategy is key to consider its commercial exploitation. Objective: To determine the reproductive season of T. depressus through description of the gonad stages and reproductive cycle, and to establish its relationship with environmental factors. Methods: We collected monthly samples (October 2016-September 2017), recording in-situ temperature and photoperiod. We evaluated a sample of 1 055 specimens for demographic characteristics, using total weight (g) and test diameter (cm). We also did a histological analysis of gonads from 178 individuals. Results: Average test diameter was 9.70 ± 0.03 cm (5-12.50 cm). Based on the proportion into the gonad of sexual (gametes) and somatic (nutritive phagocytes) cells, we propose five gonad stages (growing, premature, mature, spawning, and intergametic) for both sexes. There were two times of the year when gonads were heaviest and closely corresponded to the growing stage, coinciding with the highest proportions of nutritive phagocytes. Gonad development (growing and premature stages) peaks in the months with the longest daylight periods, with spawning in the shortest daylight periods. Conclusions: Gonad wet weight and adjusted gonad weight are good indicators of the reproductive season of T. depressus. The lowest gonad wet weights were matched the spawning peak in the shortest daylight period (January and March).

Introducción: Las gónadas de erizo de mar (huevas o uni) se consideran un manjar culinario en todo el mundo. Sin embargo, solo unas pocas especies se consideran comestibles y se comercializan. El erizo de mar Tripneustes depressus ha generado el interés de productores de Baja California Sur, México, por la calidad de sus gónadas. Una base biológica es clave para diseñar una estrategia de manejo para T. depressus para considerar su explotación comercial. Objetivo: Determinar la época reproductiva de T. depressus a través de la descripción de los estadios de las gónadas y del ciclo reproductivo, y establecer su relación con factores ambientales. Métodos: Recolectamos muestras mensuales (octubre de 2016 a septiembre de 2017), registrando in-situ la temperatura y el fotoperiodo. Evaluamos una muestra de 1055 especímenes para las características demográficas, utilizando el peso total (g) y el diámetro de testa (cm). También hicimos el análisis histológico de las gónadas de 178 individuos. Resultados: El diámetro de la testa promedio fue de 9.70 ± 0.03 cm (5-12.50 cm). Con base en la proporción en la gónada de células sexuales (gametos) y somáticas (fagocitos nutritivos), proponemos cinco estadios gonádicos (crecimiento, prematuro, maduro, desove e intergamético) para ambos sexos. Hubo dos épocas del año en que las gónadas eran más pesadas y se correspondían estrechamente con la etapa de crecimiento, coincidiendo con las proporciones más altas de fagocitos nutritivos. El desarrollo de las gónadas (etapas de crecimiento y prematuro) alcanza su punto máximo en los meses con los periodos de luz más largos, con desove en los periodos de luz más cortos. Conclusiones: El peso húmedo de las gónadas y el peso ajustado de las gónadas son buenos indicadores de la temporada reproductiva de T. depressus. Los pesos húmedos más bajos de las gónadas coincidieron con el pico de desove en el período con luz diurna más corto (enero y marzo).

How can an infaunal brooding echinoid be maintained in the laboratory? A case study with Cassidulus mitis (Echinoidea: Cassiduloida) / ¿Cómo se puede mantener un equinoide infantil en el laboratorio? Un estudio de caso con Cassidulus mitis (Echinoidea: Cassiduloida)

Introduction: Cassiduloids play a prominent role in echinoid evolutionary history because they probably are the ancestral group of clypeasteroids. Some extant species are brooding and rare in the environment. Consequently, there are no studies on their maintenance in the laboratory. Objective: Establish an efficient aquarium system for C. mitis, endemic to Brazil, for ontogenetic studies. Methods: Four aquarium systems were built, with 3 replicates each one: (1) with seawater flow [F]; (2) with seawater flow and air injection into sediment [FA]; (3) without seawater flow but with air injection into the sediment [A]; and (4) without both seawater flow and air injection into the sediment [C]. Each experimental aquarium (three per treatment) had two adults. Each of the two sets of experiments lasted about 60 days. Results: We observed low mortality in the first 30 days in all systems and, after 30 days, it was higher in those with air-pumped into the sediment (system A in the first set of experiments, and system FA in the second one). Conclusions: For experiments lasting 30 days, our four systems are suitable. For longer periods, we recommend aquaria with seawater flow and without air-pumps into the sediment.

Introducción: Los casiduloides desempeñan un papel destacado en la historia evolutiva de los equinoides porque probablemente son el grupo ancestral de clipeasteroides. Algunas especies existentes son inquietantes y raras en el medio ambiente. En consecuencia, no existen estudios sobre su mantenimiento en laboratorio. Objetivo: Establecer un sistema de acuario eficiente para C. mitis, endémica de Brasil, para estudios ontogenéticos. Métodos: Se construyeron cuatro sistemas de acuarios, con 3 réplicas cada uno: (1) con flujo de agua de mar [F]; (2) con flujo de agua de mar e inyección de aire en el sedimento [FA]; (3) sin flujo de agua de mar pero con inyección de aire en el sedimento [A]; y (4) sin flujo de agua de mar ni inyección de aire en el sedimento [C]. Cada acuario experimental (tres por tratamiento) tenía dos adultos. Cada uno de los dos conjuntos de experimentos duró aproximadamente 60 días. Resultados: Observamos una baja mortalidad en los primeros 30 días en todos los sistemas y, después de 30 días, fue mayor en aquellos con aire bombeado al sedimento (sistema A en el primer conjunto de experimentos y sistema FA en el segundo). Conclusiones: Para experimentos de 30 días, nuestros cuatro sistemas son adecuados. Para períodos más largos, recomendamos acuarios con flujo de agua de mar y sin bombas de aire en el sedimento.

Embryonic and larval development is conditioned by water temperature and maternal origin of eggs in the sea urchin Arbacia dufresnii (Echinodermata: Echinoidea) / El desarrollo embrionario y larvario está condicionado por la temperatura del agua y el origen materno de los huevos en el erizo de mar Arbacia dufresnii (Echinodermata: Echinoidea)

Introduction: Embryonic and larval development in sea urchins is highly dependent on maternal nutritional status and on the environmental conditions of the seawater. Objective: To compare the development of Arbacia dufresnii in two different water temperatures and in progeny with varying maternal origins. Methods: We induced A. dufresnii females and males from Nuevo Gulf to spawn, collected the eggs of each female individually (progeny), separated them into two seawater temperatures (12 and 17 °C), and fertilized them. We recorded the percentage of fertilized eggs and embryos per developmental stage according to time, temperature and progeny. We measured larval growth by total length (TL) and midline body length (M) according to time post fecundation (DPF), temperature, and progeny. Results: Temperature did not affect fertilization, but embryo development was faster and more synchronized in the high temperature treatment. The generalized linear models indicate that embryo development depends on a quadruple interaction between the embryonic stage, time (h), seawater temperature and progeny. Larval growth was faster, producing larger larvae at the highest temperature. Larval growth depends on a triple interaction between time (DPF), seawater temperature and progeny. Conclusions: We found a temperature and progeny impact during embryonic and larval development and, in both cases, these factors generate a synergistic effect on developmental timing and larval size. This probably provides a survival advantage as a more rapid speed of development implies a decrease in the time spent in the water column, where the sea urchins are vulnerable to biotic and abiotic stressors.

Introducción: El desarrollo embrionario y larvario de los erizos de mar depende en gran medida del estado nutricional materno y de las condiciones ambientales del agua de mar. Objetivo: Comparar el desarrollo de Arbacia dufresnii en dos temperaturas de agua diferentes y en progenies con diferentes orígenes maternos. Métodos: Indujimos a las hembras y machos de A. dufresnii del Golfo Nuevo a desovar, recolectamos los huevos de cada hembra individualmente (progenie), los separamos en dos temperaturas de agua de mar (12 y 17 ° C) y los fertilizamos. Registramos el porcentaje de óvulos fecundados y el porcentaje de embriones por etapa de desarrollo según tiempo, temperatura y descendencia. Medimos el crecimiento larvario según la longitud total (TL) y la longitud corporal de la línea media (M) de acuerdo con el tiempo en días post fecundación, la temperatura y la progenie. Resultados: La temperatura no afectó la fertilización, pero el desarrollo del embrión fue más rápido y más sincronizado en el tratamiento de alta temperatura. Los modelos lineales generalizados indican que el desarrollo del embrión depende una interacción cuádruple entre el estadio embrionario, el tiempo (h), la temperatura del agua de mar y la progenie. El crecimiento larvario fue más rápido, produciendo larvas más grandes a la temperatura más alta. El crecimiento de las larvas depende de una triple interacción entre el tiempo (DPF), la temperatura del agua de mar y la progenie. Conclusiones: Encontramos un impacto en la temperatura y en la progenie durante el desarrollo embrionario y larvario y, en ambos casos, estos factores generaron un efecto sinérgico sobre el tiempo de desarrollo y el tamaño de las larvas. Esto probablemente proporciona una ventaja de supervivencia, ya que una velocidad de desarrollo más rápida implica una disminución en el tiempo que pasan en la columna de agua, donde los erizos de mar son vulnerables a los factores estresantes bióticos y abióticos.

Efecto de la temperatura sobre la morfología y reproducción en el erizo de mar Arbacia dufresnii (Echinodermata: Echinoidea) / Effect of temperature on morphology and reproduction of sea urchin, Arbacia dufresnii (Echinodermata: Echinoidea)

Introducción: El aumento de los valores del CO2 atmosférico y el consecuente calentamiento del agua de mar constituyen factores de estrés para los ecosistemas marinos, renovando el interés en la fisiología de los equinoideos. El equinoideo Arbacia dufresnii es una especie ampliamente estudiada y con amplia distribución en los golfos norpatagónicos. Objetivo: Evaluar el efecto de temperatura del agua de mar sobre su morfología y reproducción. Métodos: Individuos de A. dufresnii fueron expuestos durante 10 semanas (Abril-Junio 2016) a tres tratamientos de temperatura (13 °C control, 15 °C y 17 °C) de acuerdo con las condiciones actuales del agua de mar y los valores esperados para el próximo siglo, según diferentes escenarios estimados. Al finalizar el experimento, diámetro y peso del individuo así como los pesos de los órganos internos fueron estadística e histológicamente analizados. Resultados: Se observó una mayor mortalidad en los individuos expuestos a las mayores temperaturas lo que podría deberse a un estrés en el individuo. Para el tratamiento control y el de 17 °C no se observaron cambios en los pesos secos de gónadas e intestino. En cambio, los individuos expuestos a 15 °C presentaron un aumento en el diámetro del caparazón y en el peso seco de gónadas e intestino. Los estadios gonadales aesta temperatura (15 °C) para machos fueron similares al ambiente a diferencia de las hembras que se observaron estadios más avanzados. Conclusiones: Esto indicaría que 15 °C podría ser la temperatura óptima para la asimilación del alimento y obtención de energía. A esta temperatura se observan cambios a corto plazo en los órganos de metabolismo rápido pero no en los órganos calcificados (caparazón y linterna de Aristóteles).

Introduction: The increase in atmospheric CO2 values and the consequent warming of seawater constitute stressors for marine ecosystems, renovating interest in echinoid physiology. The echinoid Arbacia dufresnii is a widely studied species with a wide distribution in the North Patagonian gulfs. Objective: Evaluate the effect of seawater temperature on its morphology and reproduction. Methods: Individuals were exposed for 10 weeks (April-June 2016) to three temperature treatments (13 °C control, 15 °C and 17 °C) according to the current conditions of seawater and the expected values for the next century. At the end of the experiment, diameter and weight of the whole individual and of its internal organs were statistically and histologically analyzed. Results: Individuals exposed to higher temperatures died in greater numbers. The control, and the 17 °C treatment, had no changes in dry gonad and intestine weights. However, the 15 °C group had wider diameter of test and a higher dry weight of gonads and intestine. At this temperature, the gonadal stages for males were similar to the environment, but females had more advanced stages. Conclusions: Temperature of 15°C could be optimal for assimilating food and obtaining energy. Gonads and intestine would be showing changes in the short term, unlike the calcified organs (test and Aristotle's lantern).

Photoperiod in aquaculture of the sea urchin Arbacia dufresnii (Echinodermata: Echinoidea): Effects on gamete production and maturity / Fotoperiodo en la acuicultura del erizo de mar Arbacia dufresnii (Echinodermata: Echinoidea): El efecto en la producción y madurez de gametas

Introduction: Photoperiod is, together with temperature and food availability, one of the main stimuli in the regulation of gametogenesis in a wide variety of species. Objective: To evaluate the effect of photoperiod on the production of mature gametes in cultured Arbacia dufresnii. Methods: An experiment was carried out with three varying light-dark regimes/treatments: constant light (24 h light), neutral photoperiod (12 h light, 12 h darkness), and constant darkness (24 h darkness). Twenty females were used in each treatment. All were induced to spawn and, ten randomly selected females from each treatment were induced to spawn again after 30 days. After 60 days, spawning was induced in the remaining females. The gametes were collected in filtered seawater, fixed in Davidson solution, quantified and measured per individual in triplicate in a Sedgewick-Rafter chamber. To determine maturation, fertilization success was evaluated 30 minutes after fertilization. Results: Our results showed that in the aquaculture system, after only two months, mature gametes were obtained, and in the neutral light regime there were 10 times more gametes than the number produced in wild sea urchins during the spawning period in question. We also found that with a greater exposure to light, a lower number of mature gametes was produced. Conclusions: This study suggests the viability of the production of mature gametes in a short period of time as regards Arbacia dufresnii.

Introducción: El fotoperiodo es, junto con la temperatura y la disponibilidad de alimentos, uno de los principales estímulos para el desarrollo de la gametogénesis en una amplia variedad de especies. Objetivo: Evaluar el efecto del fotoperiodo en la producción de gametas maduras de Arbacia dufresnii en un sistema de recirculación cerrado para determinar el mejor fotoperiodo para una acuicultura novedosa, enfocada en la producción de gametas con alta concentración de pigmentos para usos biotecnológicos. Métodos: Se realizó un experimento con tres regímenes/tratamientos diferentes de luz y oscuridad: luz constante (luz durante 24 h), fotoperiodo neutro (12 h de luz, 12 h de oscuridad) y oscuridad constante (oscuridad durante 24 h). Se utilizaron veinte hembras en cada tratamiento. Se indujo a todas las hembras a desovar al comienzo del experimento. Después de 30 días, diez hembras seleccionadas al azar de cada tratamiento fueron inducidas a desovar nuevamente. Al final del experimento, después de 60 días, se indujo el desove a las hembras restantes en cada tratamiento. Las gametas se recolectaron en agua de mar filtrada, se fijaron en solución de Davidson, se cuantificaron y midieron por triplicado en una cámara Sedgewick-Rafter. Para determinar la maduración, se evaluó el éxito de la fecundación después de 30 minutos de fertilización, calculando el porcentaje de huevos fertilizados. Resultados: Nuestros resultados muestran que, en el sistema acuícola, en solo dos meses se obtuvieron gametas maduras y casi 10 veces más la cantidad producida por los erizos de mar en su ambiente natural usando el fotoperiodo neutro (12 h luz:12 h oscuridad). También encontramos que la mayor exposición a la luz produce la menor cantidad de gametas maduras. Conclusión: Este estudio sugiere la viabilidad de la producción de gametos maduros en un corto período de tiempo en Arbacia dufresnii.