Shallow-water brittle stars (Echinodermata: Ophiuroidea) from Araçá Bay (Southeastern Brazil), with spatial distribution considerations.

The detailed study of arm ossicles, particularly the lateral arm plates, is providing valuable information in the elucidation of ophiuroid taxonomy. The present study describes in detail 16 species of brittle stars from Araçá Bay, Brazil. This information is used to construct the first interactive electronic key, providing a valuable resource for a broad range of researchers. Brittle stars families were divided into three groups based on their spatial distribution: i) infaunal species of intertidal and shallow subtidal belonging to Amphiuridae and Ophiactidae, ii) epizoic species belonging to Amphiuridae, Ophiactidae, and Ophiotrichidae and, iii) epifaunal species of the subtidal belonging to Ophiodermatidae and Hemieuryalidae. In the global context of recent revisions of ophiuroid taxonomy, the present work provides additional characters for use in future phylogenetic studies.

Distribution patterns of ectosymbiont crabs and their sand dollar hosts in a subtropical estuarine sandflat / Patrones de distribución de cangrejos ectossimbiontes y sus equinoideos anfitriones en un banco arenoso de un estuario subtropical

Abstract Encope emarginata (Leske, 1778) are frequently observed aggregated in the sediment and variations in its spatial patterns of distribution may be a function of changes on local hydrodynamic regime. Tiny crabs, Dissodactylus crinitichelis Moreira, 1901 living associate with these irregular echinoids. It is unclear whether the presence of crabs can affect the fitness of hosts and if this effect may be dependent on the abundance of crabs that a sand dollar is capable of hosting. If we consider that sand dollars act as substrate for symbionts then, they are subject to intraspecific competition for space. Based on this assumption, we hypothesize that the abundance of crabs will be positively correlated with sand dollar size. Two sampling campaigns were made, one in September - 2011 and other in May - 2012. Sand dollars were counted and measured in situ at the tidal flat in front of Cobras' Island (25° 29' 5" S - 48° 25' 48" W) in the Paranaguá Bay - Southern, Brazil. Four parallel transects were distributed between depths of 0.5 to 2 m and the number of individuals were counted in a sample area of 4 m². In another moment, 164 sand dollars and their symbionts were measured. We observed 906 specimens of E. emarginata (558 in Sep / 11 and 348 in May / 12). Sand dollar densities range from zero to 20 ind. 4 m-², and had an aggregate distribution pattern with patches of different densities within transects and periods (F2, 15 = 9.466, p < 0.01). Patches were observed near to the coast in Sep / 11 compared with May / 12. The symbionts D. crinitichelis present a more variable distribution pattern if compared with sand dollars. In Sep / 11, crabs were clumped distributed as well as sand dollars. On the other hand, in May / 12 D. crinitichelis was random distributed, displaying a distinct pattern than those observed for E. emarginata hosts. No relationship between size of E. emarginata and the number symbionts was observed (Longitudinal axes: r = - 0.021, p < 0.05; Transverse axes: r = - 0.017, p > 0.05), refuting the hypothesis that space is a limiting resource for the crabs. On the contrary, distribution patterns of D. crinitichelis were seemingly influenced by the distribution of their host population, rather than by one single host specimen. This suggests that other factors (e.g., the spatial distribution and connectivity between patches within a population of sand dollars) may be more important for the population dynamics of D. crinitichelis than competition for space per se. Rev. Biol. Trop. 63 (Suppl. 2): 209-220. Epub 2015 June 01.

Resumen Encope emarginata se agrupa con frecuencia y las variaciones observadas en los sedimentos y en sus patrones espaciales de distribución pueden ser en función de los cambios en el régimen hidrodinámico local. Asociados con estos equinoideos irregulares viven pequeños cangrejos Dissodactylus crinitichelis. Si se considera que los equinoideos actúan como sustrato para sus simbiontes, estos están sujetos a competición intraespecífica por espacio. Basándose en esta suposición, fue creada la hipótesis de que la abundancia de cangrejos y el tamaño del equinoideo se correlacionan positivamente. Se hicieron dos muestreos, uno en septiembre de 2011 y otro en mayo de 2012. Los equinoideos fueron contados y medidos in situ, en la llanura de marea frente a Isla de las Cobras (25° 29' 5" S - 48° 25' 48" W) en la Bahía de Paranaguá - Sur, Brasil. Fueron distribuidos cuatro transectos en paralelo a la playa entre profundidades de 0,5 a 2m, y el número de organismos se contaron en un área de 4 m-2. Después, 164 equinoideos se midieron aleatoriamente (ejes longitudinales y transversales en la vista oral) y la cantidad de simbiontes por anfitrión fue contada. Observamos 906 especímenes de E. emarginata (558 en septiembre / 11 y 348 en mayo / 12), las densidades de equinoideos van de cero a 20 ind.4m-2. Los equinoideos siguieron un patrón de distribución agrupado con manchas de diferentes densidades dentro de los transectos y puntos (F2, 15 = 9.466, p < 0.01). En septiembre / 11 fueron observadas manchas más cerca de la costa en comparación con mayo / 12. El simbionte D. crinitichelis muestra un patrón de distribución más variable cuando se compara con sus anfitriones. En septiembre / 11 los cangrejos eran agrupados, así como los equinoideos. Mientras en mayo / 12 D. crinitichelis se distribuyeron al azar, mostrando un patrón distinto de que los observados para E. emarginata. No se observó relación entre el tamaño de E. emarginata y el número de simbiontes (eje longitudinal: r = - 0.021, p < 0.05; eje transversal: r = - 0.017, p > 0.05), rechazando la hipótesis de que espacio es un recurso limitante para los cangrejos. Al contrario, los patrones de distribución de D. crinitichelis fueron aparentemente influenciados por la distribución de la población de los anfitriones, en lugar de por un solo espécimen. Esto sugiere que otros factores (por ejemplo, la distribución espacial y la conectividad entre manchas en las poblaciones de equinoideos) pueden ser más importantes para la dinámica poblacional de D. crinitichelis de que la competición por espacio en sí.

Seasonal variation in body size and diet of the sea star Astropecten marginatus (Paxillosida, Astropectinidae) off coast of Paraná, Southern Brazil.

The sea star Astropecten marginatus has a neotropical distribution and is a highly abundant and frequent species in shrimp trawling by-catchin many places along the Brazilian coast. This has caused its threat to extinction and in addition, its bio-ecological aspects are poorly known. Thus, the main objective of this study was to analyze the seasonal variations of population length structure and feeding habits of the sea stars A. marginatus inhabiting off state of Paraná, Southern Brazil. The analyzed specimens were collected in February (summer), April (fall), June (winter) and October (spring) of 2008 from shrimp by-catch trawling. In the laboratory, each individual had its length measured and then weighed on an analytical scale. Afterwards, the stomach contents of 10 individuals of each of two most frequent length classes were seasonally analyzed. The relative frequency and abundance for each prey category was determined and, then combined into an index of alimentary importance. A total of 994 individuals of A. marginatus were collected with length ranging from 7.0 to 56.2mm, but most individuals were in the 20.1-25mm length classes. Individuals larger than 40mm were only collected in the spring while a few recruits (<10mm) were found in fall and winter. The total weight of individuals ranged from 0.1 to 15.3g and the weight-length relationships showed a negative allometric growth (b<2.54). Regarding its food consumption, this sea star explored eleven food items, with cumaceans and mollusks as the most frequent items. High frequency of empty stomach was recorded at fall. Seasonal differences in the amount explored preys and ingested items as well as in the prey composition were also observed. Higher amount of explored prey categories and ingested items were recorded at winter-spring than summer-fall periods. Predominance in prey category changed from gastropods (summer and fall) to cumaceans (winter and spring). The importance of gastropods as main prey category at summer and fall should be carefully considered since it was coincidently observed with high frequency of empty stomach and low amount of ingested items. The observed seasonal differences in feeding behavior pattern were mainly associated to low prey availability and to changes in the sea star feeding rates, and probably reflected in some biological traits such as small body size of the population inhabiting waters off the Paraná coast, Southern Brazil.

Seasonal variation in body size and diet of the sea star Astropecten marginatus (Paxillosida, Astropectinidae) off coast of Paraná, Southern Brazil / Variaciones estacionales en el tamaño corporal y dieta de la estrella de mar Astropecten marginatus (Paxillosida, Astropectinidae) frente a la costa de Paraná, sur de Brasil

The sea star Astropecten marginatus has a neotropical distribution and is a highly abundant and frequent species in shrimp trawling by-catchin many places along the Brazilian coast. This has caused its threat to extinction and in addition, its bio-ecological aspects are poorly known. Thus, the main objective of this study was to analyze the seasonal variations of population length structure and feeding habits of the sea stars A. marginatus inhabiting off state of Paraná, Southern Brazil. The analyzed specimens were collected in February (summer), April (fall), June (winter) and October (spring) of 2008 from shrimp by-catch trawling. In the laboratory, each individual had its length measured and then weighed on an analytical scale. Afterwards, the stomach contents of 10 individuals of each of two most frequent length classes were seasonally analyzed. The relative frequency and abundance for each prey category was determined and, then combined into an index of alimentary importance. A total of 994 individuals of A. marginatus were collected with length ranging from 7.0 to 56.2mm, but most individuals were in the 20.1-25mm length classes. Individuals larger than 40mm were only collected in the spring while a few recruits (<10mm) were found in fall and winter. The total weight of individuals ranged from 0.1 to 15.3g and the weight-length relationships showed a negative allometric growth (b<2.54). Regarding its food consumption, this sea star explored eleven food items, with cumaceans and mollusks as the most frequent items. High frequency of empty stomach was recorded at fall. Seasonal differences in the amount explored preys and ingested items as well as in the prey composition were also observed. Higher amount of explored prey categories and ingested items were recorded at winter-spring than summer-fall periods. Predominance in prey category changed from gastropods (summer and fall) to cumaceans (winter and spring). The importance of gastropods as main prey category at summer and fall should be carefully considered since it was coincidently observed with high frequency of empty stomach and low amount of ingested items. The observed seasonal differences in feeding behavior pattern were mainly associated to low prey availability and to changes in the sea star feeding rates, and probably reflected in some biological traits such as small body size of the population inhabiting waters off the Paraná coast, Southern Brazil.

La estrella de mar Astropecten marginatus presenta una distribución neotropical y debido a su abundancia es frecuente encontrarla como captura incidental durante actividades de pesca de arrastre; actividad por la cual se encuentra amenazada en muchos lugares a lo largo de la costa brasileña. En este estudio se analizaron las variaciones estacionales de la estructura de la población y se determinaron los principales componentes de la dieta de A. marginatus frente a la costa de Paraná, sur de Brasil. Las muestras analizadas provinieron de las capturas de la pesca de arrastre recogidas en febrero (verano), abril (otoño), junio (invierno) y octubre (primavera) 2008. De cada individuo se midió la longitud y se pesó, posteriormente se analizó el contenido estomacal de 10 organismos de cada una de las dos clases de talla más frecuentes por cada temporada. Se analizaron 994 ejemplares de A. marginatus, los cuales presentaron una longitud que varió entre 7.0-56.2mm, con mayor frecuencia de individuos entre 20.1-25mm. Los organismos mayores (>40mm) se encontraron solamente en la primavera, mientras aquellos con talla inferior a los 10mm se obtuvieron durante el otoño y el invierno. El peso de los individuos se mantuvo entre los 0.1-15.3g. La relación entre el peso y talla mostró un crecimiento alométrico negativo (b<2.54). En cuanto a la dieta, esta especie consumió un total de once presas, de las cuales los cumáceos y moluscos fueron los grupos más consumidos. Una mayor cantidad de presas exploradas se registró en el invierno-primavera de los períodos de verano-otoño. El predominio de la presa cambió de gasterópodos (verano y otoño) a cumáceos (invierno y primavera). Las diferencias estacionales en el patrón de alimentación podrían estar asociadas a una baja disponibilidad de presas y a los cambios en las tasas de alimentación, lo cual se ve reflejado en algunos rasgos biológicos, como el pequeño tamaño del cuerpo esta población.