Abstract
Astropecten marginatus is a sea star widely distributed in Northern and Eastern South America, found on sandy and muddy bottoms, in shallow and deep waters. To describe some of its ecological characteristics, we calculated it spatial-temporal distribution, population parameters (based on size and weight) and diet in the Orinoco Delta ecoregion (Venezuela). The ecoregion was divided in three sections: Golfo de Paria, Boca de Serpiente and Plataforma Deltana. Samples for the rainy and dry seasons came from megabenthos surveys of the "Línea Base Ambiental Plataforma Deltana (LBAPD)" and "Corocoro Fase I (CFI)" projects. The collected sea stars were measured, weighted and dissected by the oral side to extract their stomach and identify the preys consumed. A total of 570 sea stars were collected in LBAPD project and 306 in CFI one. The highest densities were found during the dry season in almost all sections. In LBAPD project the highest density was in "Plataforma Deltana" section (0.007 +/- 0.022 ind/m2 in dry season and 0.014 +/- 0.06 ind/m2 in rainy season) and in the CFI project the densities in "Golfo de Paria" section were 0.705 +/- 0.829 ind/m2 in rainy season and 1.027 +/- 1.107 ind/m2 in dry season. The most frequent size range was 3.1-4.6cm. The highest biomass was found in "Golfo de Paria" section (7.581 +/- 0.018 mg/m2 in dry season and 0.005 +/- 6.542 x 10(-06) mg/m2 in rainy season for 2004-2005 and 3.979 +/- 4.024 mg/m2 in dry season; and 3.117 +/- 3.137 mg/m2 in rainy season for 2006). A linear relationship was found between the sea star size and its weight but no relationship was observed between its size and the depth where it was collected. Mollusks are dominant in the sea star diet (47.4% in abundance). The diet in any of the sections, seasons or between projects or size class was heterogeneous, using multivariate ordinations (MDS) and SIMPER analysis and there was no difference in the prey number or food elements that a sea star can eat. Although A. marginatus has been described as a predator, in this study were also inferred scavenger and detritivorous habits.
Highlights
Astropecten marginatus Gray 1840 es una estrella de mar perteneciente a la Clase Asteroidea, Orden Paxillosida y Familia Astropectinidae
Impacto de las aguas del Río Orinoco es mayor, con un limitado desarrollo de tallas grandes en dicho sector
Se ha planteado que las estrellas presentan una búsqueda activa de la presa y son capaces de excavar en el sustrato hasta conseguirla, presentando también selectividad en el tamaño de la presa, prefiriendo los organismos de tallas más pequeñas (Lera 1980, Bitter & Penchaszadeh 1983, Beddingfield & McClintock 1993, Vala 2005, Caregnato et al 2009)
Summary
Área de estudio: Comprendió la ecorregión Delta del Orinoco, la cual abarca las aguas del Océano Atlántico venezolano, frente a la desembocadura del Río Orinoco y el Golfo de Paria. El proyecto LBAPD fue realizado en dos campañas: una en la época de sequía (octubre 2004) y otra en la de lluvia (finales de mayo y principio de junio 2005), muestreándose 39 estaciones por campaña (con una muestra por estación) en toda la ecorregión: seis en Golfo de Paria, cuatro en Boca de Serpiente y 29 en Plataforma Deltana. Los muestreos del proyecto CFI fueron realizados en tres campañas sólo en el Golfo de Paria, dos durante la época de lluvia (junio y agosto 2006) y una en época de sequía (octubre 2006), habiéndose muestreado 18 estaciones por campaña y tres repeticiones por estación (Cuadro 1). Todas las muestras fueron colocadas en bolsas herméticamente selladas y
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