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Abstract Introduction: The genus Agassizia in Mexico is represented both in the fossil record by the species Agassizia regia† during the Miocene of Chiapas and by the extant species Agassizia excentrica on the Atlantic coast and Agassizia scrobiculata on the Pacific coast. Qualitative diagnosis and descriptions make it hard to distinguish morphological boundaries between species, especially in groups with fossils and recent representatives, increasing the level of complexity by having samples of disparate qualities and quantities. Objective: We propose the use of little explored statistical methods in the comparison of paleontological and biological populations. This methodology allowed us to resolve issues of missing values in a morphometric data set for the genus Agassizia. Methods: Using samples recently collected and specimens already housed in collections, we explore a routine of recovery of missing data MICE and the numerical and graphic analyses PERMANOVA, PCA, and SIMPER to compare morphometric parameters between these species for recognizing diagnostic characters. Results: Our results show a morphological difference in the length of the ambulacrum II and the length and width of the periproct and peristome structures, these being greater in A. scrobiculata, with a consistent pattern in both population samples not previously described. Conclusions: Quantitative morphometric comparisons can be an assertive and complementary tool to determine distinctive differentiation characteristics in species of the same genus. Comparative morphology reviews should be an ongoing exercise to keep taxonomic knowledge on both extinct and extant species up to date. Our research encourage the scientific community studying fossil populations to utilize quantitative and multivariate methods to strengthen their investigations.

Resumen Introducción: El género Agassizia en México está representado tanto en el registro fósil por la especie Agassizia regia† del Mioceno de Chiapas, como por las especies actuales Agassizia excentrica de la costa del Atlántico y Agassizia scrobiculata de la costa del Pacífico. Las descripciones y diagnosis cualitativas dificultan reconocer los limites morfológicos entre especies, especialmente en grupos con representantes fósiles y recientes, e incrementando el nivel de complejidad al tener muestras de cantidad y calidad desiguales. Objetivo: Proponemos el uso de métodos estadísticos poco explorados en la comparación de poblaciones paleontológicas y biológicas. Esta metodología nos permitió resolver problemas de valores faltantes en un conjunto de datos morfométricos para el género Agassizia. Métodos: Usando muestras recolectadas para este fin, así como provenientes de colecciones científicas, exploramos una rutina de recuperación de datos faltantes MICE, y los análisis numéricos y gráficos PERMANOVA, PCA y SIMPER para comparar parámetros morfométricos entre estas especies y reconocer caracteres de diagnóstico. Además, comparamos cuidadosamente los caracteres morfológicos descritos previamente en la literatura taxonómica y la descripción ambiental del hábitat actual de A. scrobiculata. Resultados: Nuestros resultados muestran una diferencia morfológica en la longitud del ambulacrum II y la longitud y anchura de las estructuras del periprocto y peristoma, siendo estas mayores en A. scrobiculata, con un patrón consistente en ambas muestras poblacionales no descrito previamente. El hábitat actual de las muestras de A. scrobiculata en la costa del Pacífico es un sistema costero poco profundo con sedimentos arenosos y temperaturas tropicales. Bahía Chamela comparte varias similitudes con la fauna y las condiciones ambientales previamente descritas en el Mioceno de Chiapas. Conclusiones: Las comparaciones morfométricas cuantitativas pueden ser una herramienta poderosa y complementaria para determinar caracteres distintivos de diferenciación en especies del mismo género. Las revisiones de morfología comparativa deben ser un ejercicio continuo para mantener actualizado el conocimiento taxonómico sobre las especies existentes y extintas. Nuestro trabajo busca incentivar a la comunidad científica que trabaja con poblaciones fósiles a explorar estos y otros métodos cuantitativos y multivariados para fortalecer sus investigaciones.

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The sea urchins Echinothrix calamaris and Echinothrix diadema have sympatric distributions throughout the Indo-Pacific. Diverse colour variation is reported in both species. To reconstruct the phylogeny of the genus and assess gene flow across the Indo-Pacific we sequenced mitochondrial 16S rDNA, ATPase-6, and ATPase-8, and nuclear 28S rDNA and the Calpain-7 intron. Our analyses revealed that E. diadema formed a single trans-Indo-Pacific clade, but E. calamaris contained three discrete clades. One clade was endemic to the Red Sea and the Gulf of Oman. A second clade occurred from Malaysia in the West to Moorea in the East. A third clade of E. calamaris was distributed across the entire Indo-Pacific biogeographic region. A fossil calibrated phylogeny revealed that the ancestor of E. diadema diverged from the ancestor of E. calamaris ~ 16.8 million years ago (Ma), and that the ancestor of the trans-Indo-Pacific clade and Red Sea and Gulf of Oman clade split from the western and central Pacific clade ~ 9.8 Ma. Time since divergence and genetic distances suggested species level differentiation among clades of E. calamaris. Colour variation was extensive in E. calamaris, but not clade or locality specific. There was little colour polymorphism in E. diadema.

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Introduction: Density is one of the critical factors in echinoderm larvae for aquaculture purposes. Echinoplutei larvae are very sensitive to overcrowding. High culture density can lead to problems with bacteria or protozoa, decreasing survival and generating abnormal morphotypes. Objective: To evaluate the effect of culture density on survival and larval growth in the sea urchin Arbacia dufresnii. Methods: Two days after fertilization of A. dufresnii we we kept treatments at 1, 3, 5 and 10 larvae.ml-1, with three replicates each. We recorded survival and abnormal morphotypes periodically, as well as growth:somatic rod length, total length, and length of the post oral arms,. we applied generalized linear models. Results: Survival is dependent on density, time and replicates, and their interactions. Larval growth depended on density and time, also with interaction between the variables. The treatment of 5 larvae.ml-1 had the highest survival and larval condition. Conclusions: Larval culture of A. dufresnii had the best results at 5 larvae.ml-1.

Introducción: La densidad es uno de los factores críticos para las larvas de equinodermo para fines de acuicultura. Las larvas de Echinoplutei son muy sensibles al hacinamiento. Una alta densidad de cultivo puede provocar problemas con bacterias o protozoos, disminuyendo la supervivencia y generando morfotipos anormales. Objetivo: Evaluar el efecto de la densidad de cultivo sobre la supervivencia y el crecimiento larvario del erizo de mar Arbacia dufresnii. Métodos: Dos días después de la fertilización de A. dufresnii se mantuvieron los tratamientos a 1, 3, 5 y 10 larvas.ml-1, con tres repeticiones cada uno. Registramos la supervivencia y los morfotipos anormales periódicamente, así como el crecimiento: longitud de la varilla somática, longitud total y longitud de los brazos posorales. aplicamos modelos lineales generalizados. Resultados: La supervivencia depende de la densidad, el tiempo y las réplicas y sus interacciones. El crecimiento larvario dependió de la densidad y el tiempo, también de la interacción entre las variables. El tratamiento de 5 larvas.ml-1 tuvo la mayor supervivencia y condición larvaria. Conclusiones: El cultivo larvario de A. dufresnii tuvo los mejores resultados con 5 larvas.ml-1.

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Introduction: Scutelliforms were diverse and widespread in shallow marine environments during Neogene times in South America. Nevertheless, they have almost never been used as biostratigraphic tools. Objective: To provide a refined stratigraphic frame useful for calibrating temporal dimensions of scutelliform diversity from Argentina and Uruguay and its correlation with the molluscan assemblages previously proposed. Methods: A detailed survey of their geographic and stratigraphic provenance was carried out. We revised both the bibliography and collections (institutional and from our own field work). Results: The group is represented by 14 species belonging to six genera, and four assemblages were identified. Numerical dates of the Neogene marine rocks obtained recently allowed their placement in a chronological scheme: "Iheringiella" sp. A is restricted to the late Oligocene, the genera Camachoaster and "Eoscutella" and the species Monophoraster telfordi to the early Miocene, Abertella gualichensis and Abertella miskellyi to the middle Miocene, and Monophoraster duboisi, Amplaster coloniensis and Amplaster ellipticus to the late Miocene. Non-lunulate scutelliforms are not restricted to the late Oligocene as previously supposed. The oldest occurrence of the genus Monophoraster corresponds to the early Miocene, and along with Iheringiella are long-living taxa that embrace the 25.3 Ma-18.1 Ma (Iheringiella patagonensis) and approximately 15 Ma-6.48 Ma (Monophoraster darwini) intervals. The presence of Iheringiella in the early Miocene of northeastern Patagonia is corroborated, reaching there its northernmost distribution. Monophoraster darwini has a temporal range from the late Miocene (where it was previously thought to be restricted) back to the middle Miocene, since this is the species yielded in the well-known and discussed "Monophoraster and Venericor Beds". Conclusions: The Paleogene-Neogene scutelliforms of Argentina and Uruguay range from the late Oligocene to the late Miocene. There is a good correspondence among the numerical ages, molluscan biozones and scutelliform assemblages.

Introducción: Realizamos una síntesis actualizada de la composición taxonómica de las asociaciones de escutélidos del Oligoceno tardío-Mioceno tardío de Argentina y Uruguay. Objetivo: Ubicar los escutélidos en un marco estratigráfico refinado, a los efectos de observar su diversidad a lo largo del tiempo y la correlación de sus ensambles con los ya conocidos de moluscos. Métodos: Revisamos en detalle la procedencia geográfica y estratigráfica de los ejemplares y su asignación taxonómica, basándonos tanto en la bibliografía como en colecciones institucionales y producto de nuestras campañas de colecta. Resultados: El grupo está representado por 14 especies agrupadas en seis géneros, siendo identificadas en cuatro ensambles. Las edades numéricas recientemente obtenidas permitieron su ubicación en un esquema cronológico: "Iheringiella" sp. A se restringe al Oligoceno tardío, Camachoaster y "Eoscutella", y Monophoraster telfordi al Mioceno temprano, Abertella gualichensis y Abertella miskellyi al Mioceno medio, y Monophoraster duboisi, Amplaster coloniensis y Amplaster ellipticus al Mioceno tardío. Los escutélidos sin lúnula no están restringidos al Oligoceno tardío como se suponía. Monophoraster aparece en el Mioceno temprano y junto con Iheringiella abarcan largos períodos de tiempo, encontrándoselos entre los 25.3 Ma-18.1 Ma (Iheringiella patagonensis) y aproximadamente los 15 Ma-6.48 Ma (Monophoraster darwini). Se corrobora la presencia de Iheringiella en el Mioceno temprano del noreste de Patagonia, donde alcanza su punto más septentrional. Monophoraster darwini se encuentra desde el Mioceno medio hasta el Mioceno tardío (lapso para el cual previamente se consideraba restringido), ya que se trata de la especie presente en los bien conocidos "estratos con Monophoraster y Venericor". Conclusiones: Los escutélidos del Paleógeno-Neógeno de Argentina y Uruguay se encuentran desde el Oligoceno tardío hasta el Mioceno tardío. Hay una buena correspondencia entre las edades numéricas, las biozonas de moluscos y los ensambles de escutélidos.

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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).

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In this study, we performed comprehensive pathology examinations on 83 Tripneustes ventricosus from 11 locations on St. Kitts to build baseline data necessary for disease diagnosis in this species. Gross abnormalities were observed in 23/83 (28%) urchins and included spine loss, visceral hyperpigmentation, test discoloration, and test ulceration. Ciliates were the only protists identified in this study via examination of tissue wet mounts and histology, documented in 50/83 (60%) urchins. Microscopic observations associated with visibly abnormal status included muscle necrosis, test and appendage inflammation, appendage (tube feet, spines, and pedicellariae) degeneration, severe coelomocytosis, and generalized hypermelanosis. Enterocyte intranuclear inclusion bodies, microbial aggregates, nerve pigmentation, enteric pigmentation, integument-associated crustaceans, and encysted metazoan parasites were of uncertain pathological significance. The etiology for any lesion was not microscopically apparent, contrasting literature implicating common marine bacteria in urchin diseases. This study highlights the importance of histopathology in urchin disease investigations and facilitates the recognition of disease in T. ventricosus.

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Echinoderms are restricted to the marine environment and are osmoconformer invertebrates. However, some species live in unstable environments. Especially those species, and those of larger body size, tend to show variable, albeit transient, ionic gradients between their coelomic fluid and external seawater. In order to further examine how sea urchin size relates to apparent ionic permeability of their body wall/epithelia, specimens of Echinometra lucunter, Lytechinus variegatus, Paracentrotus gaimardi, and Arbacia lixula-A. lixula of two distinct populations, Rio de Janeiro and Santa Catarina-were abruptly transferred from 35 psu to either 25 or 45 psu. Sodium, chloride, magnesium, and potassium concentrations were assayed in their coelomic fluids after 0, 1, 2, and 3 hr of exposure. Relative area of putative permeable (i.e., cross section areas of soft tissues, or test holes) surfaces (PPS) was estimated in empty tests as the sum of the peristomial area (oral hole in the empty test) and the total cross-section area of ambulacral holes, divided by the total volume (TV) of the test. L. variegatus and E. lucunter, the largest species, had PPS/TV values similar to that of the much smaller P. gaimardi. A. lixula was the "most putatively-permeable and conformer" among them all, especially urchins from the Santa Catarina population. Internal ionic levels equilibrated faster with external water in 45 than in 25, and differences among ions were observed. Body size is relevant, among many other factors, to aid conformers such as sea urchins to dwell in intertidal unstable habitats.

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A new species of monophorasterid sand dollar, Monophoraster telfordi n. sp., is described from the Early Miocene basal horizons of the Chenque Formation of Patagonia, Santa Cruz Province, in southern Argentina. The new taxon raises the number of known species in the family to six, and represents first unequivocal record of the genus for the Early Miocene of South America. It is therefore also the oldest member of the genus. M. telfordi is characterized by its test width to length ratio, which is much higher than for the other two described species in the genus, but less than that known for the extremely wide members of the sister taxon, Amplaster. M. telfordi is also unusual among monophorasterids in lacking broad continuity between basicoronal and post-basicoronal plates in the oral interambulacra. A key is provided to all the known species of Monophorasteridae.

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Lanthonia gen. nov. Coppard 2016 is a genus of clypeasteroid sand dollar whose members inhabit shallow, sandy waters from Mexico (including the Gulf of California) to Colombia in the tropical and subtropical eastern Pacific. Lanthonia includes Lanthonia longifissa (Michelin, 1858) and Lanthonia grantii (Mortensen, 1948), with L. longifissa hereby designated as the type species. Both L. longifissa and L. grantii were previously placed in the genus Mellita (L. Agassiz, 1841). However, levels of genetic divergence between a lineage containing L. longifissa and L. grantii and a lineage containing all other species of Mellita, including the type species M. quinquiesperforata (Leske, 1778), indicate genus level differentiation. The systematic interpretation of this group also supports the designation of this new genus as it allows the tree topology to be recovered from the nomenclature and clarifies the historical biogeography of these clades. This has resulted in members of both lineages today being sympatric in the eastern Pacific. Members of Lanthonia are morphologically differentiated from the type species of Mellita and all Pacific Mellita in having very narrow ambulacral regions between the food grooves and the ambulacral lunules on the oral surface, these being very broad in both M. quinquiesperforata and M. notabilis. The dentation of the bidentate pedicellariae also differentiate these genera, with small peripheral teeth present along the edge of the blade in species of Lanthonia and one to three enlarged intersecting teeth present distally in all species of Mellita.

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Knowledge of mortality rates is crucial to the understanding of population dynamics in populations of free-living fish and invertebrates in marine and freshwater environments, and consequently to sustainable resource management. There is a well developed theory of population dynamics based on age distributions that allow direct estimation of mortality rates. However, for most cases the aging of individuals is difficult or age distributions are not available for other reasons. The body size distribution is a widely available alternative although the theory underlying the formation of its shape is more complicated than in the case of age distributions. A solid theory of the time evolution of a population structured by any physiological variable has been developed in 1960s and 1970s by adapting the Hamilton-Jacobi formulation of classical mechanics, and equations to estimate the body size-distributed mortality profile have been derived for simple cases. Here I extend those results with regards to the size-distributed mortality profile to complex cases of non-stationary populations, individuals growing according to a generalised growth model and seasonally patterned recruitment pulses. I apply resulting methods to two cases in the marine environment, a benthic crustacean population that was growing during the period of observation and whose individuals grow with negative acceleration, and a sea urchin coastal population that is undergoing a stable cycle of two equilibrium points in population size whose individuals grow with varying acceleration that switches sign along the size range. The extension is very general and substantially widens the applicability of the theory.

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Aging in many animals is characterized by a failure to maintain tissue homeostasis and the loss of regenerative capacity. In this study, the ability to maintain tissue homeostasis and regenerative potential was investigated in sea urchins, a novel model to study longevity and negligible senescence. Sea urchins grow indeterminately, regenerate damaged appendages and reproduce throughout their lifespan and yet different species are reported to have very different life expectancies (ranging from 4 to more than 100 years). Quantitative analyses of cell proliferation and apoptosis indicated a low level of cell turnover in tissues of young and old sea urchins of species with different lifespans (Lytechinus variegatus, Strongylocentrotus purpuratus and Mesocentrotus franciscanus). The ability to regenerate damaged tissue was maintained with age as assessed by the regrowth of amputated spines and tube feet (motor and sensory appendages). Expression of genes involved in cell proliferation (pcna), telomere maintenance (tert) and multipotency (seawi and vasa) was maintained with age in somatic tissues. Immunolocalization of the Vasa protein to areas of the tube feet, spines, radial nerve, esophagus and a sub-population of circulating coelomocytes suggests the presence of multipotent cells that may play a role in normal tissue homeostasis and the regenerative potential of external appendages. The results indicate that regenerative potential was maintained with age regardless of lifespan, contrary to the expectation that shorter lived species would invest less in maintenance and repair.

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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.

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Resumen El ciclo gametogénico y el índice gonadosomático (IG) del erizo negro Echinometra lucunter fue examinado entre junio de 2010 y noviembre de 2011 en el noreste de Venezuela (Isla de Lobos, Península de Araya y Ensenada de Turpialito, Golfo de Cariaco). Las gónadas están integradas por extensos acinos ramificados, recubiertos por tejido conectivo, seguido de una capa delgada de células que se diferencian en fagocitos nutritivos y gametos, los cuales cambian en sus proporciones y tamaños con los estadios de maduración. Generalmente, en ambas localidades se presentaron varios estadios de maduración, con desoves simultáneos. En Isla Lobos predominaron los individuos en estado de reserva con un corto período de madurez sexual, mientras que en la Ensenada de Turpialito predominaron organismos maduros y desovados. El IG sugiere que los desoves están asociados a las precipitaciones estacionales de la región; mostrando una estrategia reproductiva conservadora, acumulando reservas energéticas en el periodo de mayor producción primaria asociada a los periodos de surgencia costera, cuando la energía de los fagocitos nutritivos es transferida a los gametos hasta su maduración y expulsión al medio ambiente. Las características biológicas y reproductivas de los organismos en Turpialito mostraron elevados IG y mayor tejido gonadal para consumo comercial.

Abstract Several species of sea urchins are a potential resource for the production of gonads for consumption in Venezuela. We studied the gametogenic cycle and the gonadosomatic index (GSI) of the rock boring urchin Echinometra lucunter between June 2010 and November 2011 in northeastern Venezuela (Isla Lobos, Península de Araya and Turpialito, Gulf of Cariaco). The gonads are composed of long ramified acini, covered by connective tissue, followed by a thin layer of cells that differentiate into nutritive phagocytes and gametes, which change in their proportion and size with the maturity stage. Generally, several maturity stages were observed in both locations, showing simultaneous spawning. At Isla de Lobos the individuals in reserve stage predominated with a short period of sexual maturity, while mature and spawned individuals predominated in Turpialito. The GSI suggests that the greatest spawning activity is associated to the rainy season; showing a conservative reproductive activity, accruing energetic reserves during the period of higher primary productivity associated to coastal upwelling, when the energy of nutritive phagocytes is transferred to gametes, for gamete development and spawning. The biological and reproductive characteristics of individuals at Turpialito showed higher GSI having more gonadal tissue for commercial consumption. Rev. Biol. Trop. 63 (Suppl. 2): 273-283. Epub 2015 June 01.

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Resumen En el presente estudio se evaluó la densidad poblacional, patrón de distribución espacial y mortalidad natural del erizo de mar Toxopneustes roseus, así como la relación entre la densidad poblacional y algunas variables ambientales. De octubre 2009 a septiembre 2011 se realizaron muestreos mensuales utilizando transectos de banda en tres localidades de la costa de Oaxaca, México: Estacahuite, Dos Hermanas e Isla Cacaluta. Adicionalmente se registró in situ la temperatura, salinidad y pH en cada localidad. Los registros de irradiación y precipitación pluvial se obtuvieron de bases de datos. El patrón de distribución se caracterizó mediante el Índice de Morisita, los modelos de probabilidad de Poisson y Distribución Binomial Negativa. La mortalidad natural se estimó utilizando el método modificado de Berry. Se aplicó un análisis de regresión lineal múltiple paso a paso para evaluar la relación entre la densidad poblacional y las variables ambientales. La densidad promedio (± DE) fue 0.12 ± 0.02 ind m-2 (Estacahuite), 0.05 ± 0.01 ind m-2 (Dos Hermanas) y 0.04 ± 0.01 ind m-2 (Isla Cacaluta). El patrón de distribución espacial fue agregado en la mayoría de los meses muestreados en las tres localidades. En Estacahuite la mortalidad natural fue 0.54 y en Dos Hermanas 0.46, para Isla Cacaluta no fue posible calcular la mortalidad natural. De las variables ambientales registradas, la precipitación pluvial mostró una relación directa pero no determinante con la densidad poblacional de T. roseus en Isla Cacaluta. Se concluye que los factores que podrían determinar la dinámica poblacional de T. roseus son: áreas con mayor extensión en general y el aporte de sedimentos por la presencia de ríos en las localidades, ya que Isla Cacaluta fue la única localidad en la que se evidenció una relación importante con la precipitación pluvial y esta localidad se ve influenciada por los ríos Copalita y Coyula, los cuales producen un importante incremento en la tasa de sedimentación en esta localidad, afectando a la comunidad bentónica en general durante la temporada de lluvias.

Abstract The sea urchin Toxopneustes roseus is widely distributed along the east coast of the tropical Pacific, from Mexico to northern Peru. In our study we evaluated population features of this species, such as population density, spatial distribution pattern and natural mortality, as well as the relationship between population density and several environmental variables. From October 2009 to September 2011 monthly sampling was carried out using belt transects in three localities of the coast of Oaxaca, Mexico: Estacahuite, Dos Hermanas and Isla Cacaluta. Additionally we recorded in situ temperature, salinity and pH in each locality. Records of irradiation and pluvial precipitation were obtained from databases. Distribution pattern of the urchins was characterized using the Morisita´s Index and the models of Poisson´s probability and Negative Binomial Distribution. Natural mortality was estimated using the modified method of Berry. A step by step analysis of Multiple Lineal Regression was applied to evaluate the relationship between population density and the recorded environmental variables. Mean (± SD) density was 0.12 ± 0.02 ind·m-2 (Estacahuite), 0.05 ± 0.01 ind·m-2 (Dos Hermanas) and 0.04 ± 0.01 ind·m-2 (Isla Cacaluta). The pattern of spatial distribution of T. roseus was aggregated in most of the sampled months in all the localities. In Estacahuite natural mortality was 0.45 and in Dos Hermanas it was 0.46, it was not possible to calculate mortality for Isla Cacaluta. Of the recorded environmental variables, pluvial precipitation showed a direct but not determinant relationship with population density of T. roseus only in Isla Cacaluta. As a result of the differences observed in the three localities we assume that the factors that could determine the population dynamics of T. roseus are: A larger extension of the area in general, and the contribution of sediments by the presence of rivers in the localities, since Isla Cacaluta was the only locality where there was evidence of an important relationship with pluvial precipitation, and this locality undergoes the influence of the rivers Copalita and Coyula, which produce an important increase in sedimentation rates at this community, affecting the entire benthic community during the rainy season. Rev. Biol. Trop. 63 (Suppl. 2): 121-133. Epub 2015 June 01.

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Resumen La localización geográfica de México, entre las influencias oceánicas del Atlántico centro-occidental y del Pacífico centro-oriental, explica en gran medida su enorme diversidad biológica y ecosistémica. Las investigaciones sobre equinodermos en México comenzaron a mitades del siglo XIX, si bien aún no existe un trabajo sobre los equinoideos irregulares que habitan sus aguas. En este trabajo se presenta por primera vez una revisión taxonómica de los equinoideos irregulares de México. En este sentido, se usaron los ejemplares de equinoideos irregulares para México albergados en cuatro colecciones: 1) Colección Nacional de Equinodermos "Ma. Elena Caso Muñoz", del Instituto de Ciencias del Mar y Limnología (ICML), Universidad Nacional Autónoma de México (UNAM); 2) Invertebrate Zoology Collection, Smithsonian Museum of Natural History, Washington, D.C., United States of America (USA); 3) Invertebrate Collection, Museum of Comparative Zoology, University of Harvard, Boston, Massachusetts, USA and 4) Invertebrate Zoology, Peabody Museum, Yale University, New Haven, Connecticut, USA. Los organismos fueron reidentificados, se corroboró la identidad taxonómica de las especies y se ubicaron taxonómicamente. Además, se realizó un análisis de biogeografía ecológica tomando en cuenta el listado de especies obtenido y la regionalización ecológica de Norteamérica. Se presenta un total de 69 especies incluidas en 6 órdenes, 17 familias, y 36 géneros distribuidas en 34 ecorregiones biogeográficas; 11 de la costa Atlántica y 23 de la costa Pacífica. Se delimitan cuatro regiones biogeográficas Atlánticas y cinco Pacíficas. En la costa Atlántica, los factores ambientales que determinan la distribución de los equinoideos irregulares son, principalmente los sedimentos y las corrientes oceánicas, mientras que en la costa Pacífica son principalmente la profundidad y las corrientes oceánicas.

Abstract Mexico owns 643 species of echinoderms, almost 10% of the known echinoderm species in the planet. Its geographic location -between the oceanic influences of the Western Central Atlantic and the Eastern Central Pacific- largely explains its enormous biological and ecological diversity. Research on echinoderms in Mexico began in the late nineteenth century; however, there are no reviews on its irregular echinoids. This work reviews the taxonomic and geographic information of irregular echinoids from Mexico, housed in four collections: 1) Colección Nacional de Equinodermos "Ma. Elena Caso Muñoz" from the Instituto de Ciencias del Mar y Limnología (ICML), Universidad Nacional Autónoma de México (UNAM); 2) Invertebrate Zoology Collection, Smithsonian Museum of Natural History, Washington, D.C., United States of America (USA); 3) Invertebrate Collection, Museum of Comparative Zoology, University of Harvard, Boston, Massachusetts, USA and 4) Invertebrate Zoology, Peabody Museum, Yale University, New Haven, Connecticut, USA. Specimens were reidentified and classified; geographic distribution data were subjected to a parsimony analysis of endemisms (PAE) using the ecological regionalization of North America proposed by Wilkinson et al. (2010). A total of six orders, 17 families, 35 genera and 68 species are reported, distributed in 34 ecoregions, 11 from the Atlantic coast and 23 from the Pacific coast. Nine biogeographic regions were delimited, four in the Atlantic coast and five in the Pacific coast. The biogeographic analysis suggests that the oceanic currents and sediments are the environmental factors that determine the distribution of irregular echinoids in the Mexican Atlantic coast; on the other hand, oceanic currents and depth are the environmental factors that determine the distribution of irregular echinoids in the Mexican Pacific coast. Rev. Biol. Trop. 63 (Suppl. 2): 59-75. Epub 2015 June 01.

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Resumen Astropyga pulvinata es un diademátido que posee cinco pares de series de puntos iridiscentes presentes en los interambulacros. A partir de la observación 20 individuos in vivo a través de un estereoscopio y el análisis con un Microscopio Electrónico de Barrido se identificaron los pedicelarios, las espículas y las rosetas calcáreas de los pies ambulacrales. Los pedicelarios presentes en A. pulvinata son trivalvados y de tres tipos: claviformes (oficéfalos) presentes en ambulacro; tridentados distribuidos en el peristoma; y trifoliados presentes en toda la testa excepto en los interambulacros. Los pedicelarios claviformes son los únicos que no están unidos por un pedúnculo calcáreo de tipo diadematoide. Se obtuvieron diez tipos de espículas de diversos tejidos blandos: uno del intestino; tres de la membrana anal y seis del peristoma, dos de las cuales no han sido descritas hasta el momento. Uno de estos nuevos tipos de espículas reportados posee forma de basto y otro de media luna. De las observaciones in vivo se encontraron puntos iridiscentes más pequeños presentes en el ambitus constituidos por aproximadamente ocho células.

Abstract Astropyga pulvinata is a sea urchin of the family Diadematidae that have five pairs of series of blue iridescent spots on interambulacral zones, from in vivo observation of 20 individuals under stereo-microscope and Scanning Electron Microscope analysis identification, the pedicellariae, spicules, and calcareous rosettes. The pedicellariae of A. pulvinata have three valves and are of three types: claviform, present on ambulacres; tridentates present on peristome and triphyllous present all over the test except in interambulacral areas. So ophicephalous pedicellariae are not bounded with a calcareous stalk. Ten types of spicules were observed from different soft tissues: one type from the intestine; three from the anal membrane; and six from the peristome, two of them constitute new diagnostic characters. One of them having a bat-shaped form and the other one with a waning crescent shape. In vivo observations showed that the blue iridescent spots were present on interambulacral areas as group of 35 cells bounded, and that other smaller spots were present on the ambitus, composed by eight cells. Rev. Biol. Trop. 63 (Suppl. 2): 49-58. Epub 2015 June 01.

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The genus Diadema presently consists of seven species, two of which are known from the Brazilian coast: D. antillarum and D. ascensionis. The first is usually known for shallow coastal areas, while the second was apparently restricted to oceanic islands. In February 2011, a dense population of D. ascensionis was observed on the coastal reefs of Praia do Francês (Alagoas State, northeastern Brazil). Five specimens were collected and transported to the laboratory where morphological studies of the test and pedicellariae were conducted. Subsequently, visits were made to scientific collections in order to compare and confirm species identifications. Our observations confirm the presence of tridentate pedicellariae with narrow and strongly curved valves. The axial cavity in the tips of the spines is filled with dense nonreticular tissue. This taxonomic data confirms the occurrence of D. ascensionis in coastal areas. On the coastal reefs of Praia do Francês, animals were observed from the beach to the reef formations about 200 m offshore in areas with a sandy substrate and in reef cavities, usually in clear and well illuminated waters. Solitary individuals or groups of up to 15 individuals formed dense populations in the area. We stress the importance of pedicellariae for the specific identification of the Diadematidae, considering that they are quite constant and reliable at this taxonomic level. Our results demonstrate that D. ascensionis is not restricted to insular environments and that this species may be common in shallow coastal habitats.

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The genus Diadema presently consists of seven species, two of which are known from the Brazilian coast: D. antillarum and D. ascensionis. The first is usually known for shallow coastal areas, while the second was apparently restricted to oceanic islands. In February 2011, a dense population of D. ascensionis was observed on the coastal reefs of Praia do Francês (Alagoas State, northeastern Brazil). Five specimens were collected and transported to the laboratory where morphological studies of the test and pedicellariae were conducted. Subsequently, visits were made to scientific collections in order to compare and confirm species identifications. Our observations confirm the presence of tridentate pedicellariae with narrow and strongly curved valves. The axial cavity in the tips of the spines is filled with dense nonreticular tissue. This taxonomic data confirms the occurrence of D. ascensionis in coastal areas. On the coastal reefs of Praia do Francês, animals were observed from the beach to the reef formations about 200 m offshore in areas with a sandy substrate and in reef cavities, usually in clear and well illuminated waters. Solitary individuals or groups of up to 15 individuals formed dense populations in the area. We stress the importance of pedicellariae for the specific identification of the Diadematidae, considering that they are quite constant and reliable at this taxonomic level. Our results demonstrate that D. ascensionis is not restricted to insular environments and that this species may be common in shallow coastal habitats.

O gênero Diadema é composto por sete espécies, das quais duas são conhecidas para o litoral brasileiro: D. antillarum e D. ascensionis. A primeira é principalmente conhecida em áreas costeiras, enquanto que a segunda está aparentemente restrita a ilhas oceânicas. Em fevereiro de 2011, uma densa população de D. ascensionis foi observada nos recifes costeiros da Praia do Francês, no Estado de Alagoas, Região Nordeste do Brasil. Cinco espécimes foram coletados e transportados ao laboratório, onde estudos morfológicos da carapaça e das pedicelárias foram desenvolvidos. Subsequentemente, foram realizadas visitas a coleções científicas para a comparação e a confirmação da espécie. As observações, neste trabalho, evidenciaram a presença de uma pedicelária tridentada com valvas estreitas e fortemente curvadas. A cavidade axial nas pontas dos espinhos é preenchida por um denso tecido não reticular. Estes dados taxonômicos confirmam a ocorrência de D. ascensionis em áreas costeiras. Nos recifes costeiros da Praia do Francês, os animais foram observados a partir da praia em direção às formações recifais localizadas a 200 m da praia, em áreas de substrato arenoso, e nas cavidades do recife, geralmente em águas claras e bem iluminadas. Os indivíduos estavam solitários ou formando grupos de até 15 indivíduos. Destaca-se a importância das pedicelárias na sistemática dos Diadematidae, tendo em vista que as mesmas são bastante constantes e confiáveis para a identificação em nível específico. Os resultados do presente trabalho demonstram que D. ascensionis não está restrita a ambientes insulares e que esta espécie pode ser comum em habitats costeiros rasos.

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RESUMEN

The genus Diadema presently consists of seven species, two of which are known from the Brazilian coast: D. antillarum and D. ascensionis. The first is usually known for shallow coastal areas, while the second was apparently restricted to oceanic islands. In February 2011, a dense population of D. ascensionis was observed on the coastal reefs of Praia do Francês (Alagoas State, northeastern Brazil). Five specimens were collected and transported to the laboratory where morphological studies of the test and pedicellariae were conducted. Subsequently, visits were made to scientific collections in order to compare and confirm species identifications. Our observations confirm the presence of tridentate pedicellariae with narrow and strongly curved valves. The axial cavity in the tips of the spines is filled with dense nonreticular tissue. This taxonomic data confirms the occurrence of D. ascensionis in coastal areas. On the coastal reefs of Praia do Francês, animals were observed from the beach to the reef formations about 200 m offshore in areas with a sandy substrate and in reef cavities, usually in clear and well illuminated waters. Solitary individuals or groups of up to 15 individuals formed dense populations in the area. We stress the importance of pedicellariae for the specific identification of the Diadematidae, considering that they are quite constant and reliable at this taxonomic level. Our results demonstrate that D. ascensionis is not restricted to insular environments and that this species may be common in shallow coastal habitats.

O gênero Diadema é composto por sete espécies, das quais duas são conhecidas para o litoral brasileiro: D. antillarum e D. ascensionis. A primeira é principalmente conhecida em áreas costeiras, enquanto que a segunda está aparentemente restrita a ilhas oceânicas. Em fevereiro de 2011, uma densa população de D. ascensionis foi observada nos recifes costeiros da Praia do Francês, no Estado de Alagoas, Região Nordeste do Brasil. Cinco espécimes foram coletados e transportados ao laboratório, onde estudos morfológicos da carapaça e das pedicelárias foram desenvolvidos. Subsequentemente, foram realizadas visitas a coleções científicas para a comparação e a confirmação da espécie. As observações, neste trabalho, evidenciaram a presença de uma pedicelária tridentada com valvas estreitas e fortemente curvadas. A cavidade axial nas pontas dos espinhos é preenchida por um denso tecido não reticular. Estes dados taxonômicos confirmam a ocorrência de D. ascensionis em áreas costeiras. Nos recifes costeiros da Praia do Francês, os animais foram observados a partir da praia em direção às formações recifais localizadas a 200 m da praia, em áreas de substrato arenoso, e nas cavidades do recife, geralmente em águas claras e bem iluminadas. Os indivíduos estavam solitários ou formando grupos de até 15 indivíduos. Destaca-se a importância das pedicelárias na sistemática dos Diadematidae, tendo em vista que as mesmas são bastante constantes e confiáveis para a identificação em nível específico. Os resultados do presente trabalho demonstram que D. ascensionis não está restrita a ambientes insulares e que esta espécie pode ser comum em habitats costeiros rasos.

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A new species of abertellid sand dollar, Abertella miskellyi n. sp., is described from the Miocene Camarones Formation of Patagonia, southern Argentina. The new taxon corroborates the existence of the genus in South America, given that Abertella is most common in the southeastern USA and the eastern coast of Central America. It is characterized by a unique basicoronal circle, in which the interambulacral basicoronal plates are very heterogeneous in size (small in interambulacrum 5, largest in interambulacra 2 and 3). Additionally, it features disjunct oral interambulacra involving two ambulacral plates in some of the interambulacra rather than one, thus being the most disjunct of all known species of Abertella. A key to the species of the genus is provided.

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