Form variation of the rotifer Brachionus variabilis (Hempel, 1896) from the Orinoco River (Venezuela)

Zooplankton abundance in the lower Orinoco River, Venezuela

Zooplankton were sampled quantitatively in the lower Orinoco River and three major tributaries (Apure, Caura, Caroni). Dominant taxa were euplanktonic, which suggests origin from standing waters. In the Orinoco, densities for rotifers (mean, 7.6 ind. liter -I) were greater than those for cladocerans (0.9 ind. liter-I) or copepods (1.2 ind. liter-‘), but cladocerans accounted for more than half ...

the effect of traffic density on the accident externality from driving the case study of tehran

در این پژوهش به بررسی اثر افزایش ترافیک بر روی تعداد تصادفات پرداخته شده است. به این منظور 30 تقاطع در شهر تهران بطور تصادفی انتخاب گردید و تعداد تصادفات ماهیانه در این تقاطعات در طول سالهای 89-90 از سازمان کنترل ترافیک شهر تهران استخراج گردید و با استفاده از مدل داده های تابلویی و نرم افزار eviews مدل خطی و درجه دوم تخمین زده شد و در نهایت این نتیجه حاصل شد که تقاطعات پر ترافیک تر تعداد تصادفا...

A new species of Crenicichla (Perciformes: Cichlidae) from the Ventuari River, Upper Orinoco River Basin, Amazonas State, Venezuela

We describe a new species of the genus Crenicichla Heckel, 1840, from the Ventuari River, a tributary of the Orinoco River in southern Venezuela. Crenicichla zebrina is distinguished from all other species in the genus by its unique coloration pattern, including the combination of a large, dark, vertically oriented, more or less oval-shaped humeral spot, and thin, dark bars, separated by narrow...

Polychaeta Diversity in the Continental Shelf Off the Orinoco River Delta, Venezuela

Causes of seasonality in the chemistry of a lake on the Orinoco River floodplain, Venezuela’

Lake Tinco, which lies on the Orinoco floodplain, passes through four seasonal phases (filling, through-flow, drainage, and isolation), during which the lake volume changes 20-fold. During filling and through-flow, when the lake is inundated by river water, floating grasses (Paspalum repens) and phytoplankton grow rapidly, causing depletion of inorganic N and P between inflow and outflow, altho...