Crecimiento en función de la densidad de poliquetos Diopatra aciculata

Effects of intraspecific density on growth of the tube-building polychaete Diopatra aciculata (Onuphidae) were examined over a three-month period within a marine worm aquaculture facility. Three polychaete densities (500, 1000 and 2000 worms/m2) were represented within triplicate 0.30 m2 boxes containing late juvenile D. aciculata, sandy sediment and recirculating seawater. Daily food ration per worm was held constant across all density levels. Total length, weight and number of segments were recorded for 20 polychaetes randomly removed from each of nine treatment boxes at weeks 1, 7 and 14. Mean daily growth was higher during weeks 1-7 than during weeks 7-14 for all growth variables at each density level. Polychaetes at the highest density level exhibited lower rates of growth and more broken and/or regenerating posterior segments than those at low density. High D. aciculata density was also associated with reduced dissolved oxygen concentrations and high polychaete mortality (20%). At medium polychaete density (1000/m2), D. aciculata exhibited low levels of apparent stress and high biomass return per unit area, both of which are important considerations in the aquaculture rearing of this species. We suggest that further studies focus on age- and size-related factors contributing to density effects on polychaete growth.Durante un período de más de tres meses se examinaron en instalaciones de acuicultura de gusanos marinos los efectos de la densidad interespecífica en el crecimiento del poliqueto tubícola Diopatra aciculata (Onuphidae). Se utilizaron tres niveles de densidad de poliquetos (aproximadamente 500, 1000 y 2000 gusanos/m2) en cajas experimentales de 0,30 m2 replicadas, conteniendo ejemplares juveniles avanzados de D. aciculata y sedimento arenoso, todo ello con recirculación de agua marina. La ración diaria de alimento por gusano se mantuvo constante en todos los niveles de densidad. Se registró la longitud total, el peso, y el número de segmentos en 20 poliquetos extraídos aleatoriamente para cada tratamiento durante las semanas 1, 7, y 14. Para cada uno de los niveles de densidad estudiados, el crecimiento diario promedio durante el período entre la semana 1 y la 7 fue mayor que durante el período entre la semana 7 y la 14 en todas las variables de crecimiento. Los poliquetos cultivados a mayores densidades poblacionales exhibieron menores tasas de crecimiento y un mayor número de segmentos posteriores fragmentados y/o regenerados que aquellos cultivados a menores densidades de población. Asimismo, la alta densidad de D. aciculata provocó menores concentraciones de oxígeno disuelto y un mayor índice de mortalidad de poliquetos (20% promedio). Al nivel medio de densidad de poliquetos (1000/m2), los ejemplares de D. aciculata presentaron un bajo nivel de estrés aparente y una elevada producción de biomasa por unidad de área, dos factores importantes en la crianza mediante técnicas de acuicultura de esta especie. Para posteriores estudios, se propone concentrarse en los efectos de la densidad en el comportamiento interactivo y en la competencia por el alimento. &nbsp

Flood Risk Assessment for Urban Drainage System in a Changing Climate Using Artificial Neural Network

Changes in rainfall patterns due to climate change are expected to have negative impact on urban drainage systems, causing increase in flow volumes entering the system. In this paper, two emission scenarios for greenhouse concentration have been used, the high (A1FI) and the low (B1). Each scenario was selected for purpose of assessing the impacts on the drainage system. An artificial neural network downscaling technique was used to obtain local-scale future rainfall from three coarse-scale GCMs. An impact assessment was then carried out using the projected local rainfall and a risk assessment methodology to understand and quantify the potential hazard from surface flooding. The case study is a selected urban drainage catchment in northwestern England. The results show that there will be potential increase in the spilling volume from manholes and surcharge in sewers, which would cause a significant number of properties to be affected by flooding

Amphipod intersex, metals and latitude: A perspective

Intersexuality has been widely reported in crustaceans with several mechanisms being directly or indirectly held responsible for its occurrence, amongst which pollution. No mechanistic relationship between metals and intersex has ever been established. Also the incidence of intersex in populations of the same invertebrate species in a latitudinal gradient has never been studied so far. Three populations (Iceland,Scotland and Portugal) of the amphipod Echinogammarus marinus were scrutinized. Intersex females from Iceland registered the highest fecundity loss. Only in Scottish samples females with two genital papillae and males with only one genital papillae were observed. Nevertheless, water, biota and sediment samples pointed to equivalent metal levels, and in consonance the prevalence of intersex was not significantly different between locations. An unequivocal relationship between metal presence and intersex induction cannot be presented, but our results advocate the potential role of metals as a direct cause of intersexuality in E. marinus

Ampelisca lusitanica (Crustacea: Amphipoda): new species for the Atlantic coast of Morocco

Background This study reports for the first time the presence of the Lusitanian ampeliscid amphipod Ampelisca lusitanica Bellan-Santini & Marques, 1986 in the northwestern Atlantic coast of Morocco. Methods Specimens were collected in January 2015 from intertidal rock pools along the El Jadida shoreline associated with the brown algae Bifurcaria bifurcata and Sargassum muticum. Results Systematic description of the species is presented, as well as a discussion of its ecological and geographical distribution. Conclusion This new finding extends the geographical distribution from the Lusitanian (Europe) to the Mauritanian (Africa) region and increases knowledge of the ecology and the global distribution of A. lusitanica found, previously, only on Portuguese and Spanish coasts.info:eu-repo/semantics/publishedVersio

Whole Brain Size and General Mental Ability: A Review

We review the literature on the relation between whole brain size and general mental ability (GMA) both within and between species. Among humans, in 28 samples using brain imaging techniques, the mean brain size/GMA correlation is 0.40 (N = 1,389; p < 10−10); in 59 samples using external head size measures it is 0.20 (N = 63,405; p < 10−10). In 6 samples using the method of correlated vectors to distill g, the general factor of mental ability, the mean r is 0.63. We also describe the brain size/GMA correlations with age, socioeconomic position, sex, and ancestral population groups, which also provide information about brain–behavior relationships. Finally, we examine brain size and mental ability from an evolutionary and behavior genetic perspective