Vitamin C (ascorbic acid) requirements of Heterobranchus longifilis fingerlings

A feeding experiment was conducted to quantify the minimum dietary vitamin C requirement of Heterobranchus longifilis fingerlings. Fish were fed a basal diet with 42.5% crude protein for a conditioning period of 2 weeks. Following conditioning, fingerlings with initial mean weight, 2.3 ± 0.3 g were stocked as groups of 20 fingerlings into 30 litre tanks in a mini-flow through experimental system. Graded levels (0, 50, 100, 150, 200 and 250) mg of L-ascorbic acid kg-1 diet was included into the basal diet by replacing part of the silica component and fed to triplicate groups for 20 weeks. Fish fed the control (0 mg vitamin C kg-1) diet exhibited deficiency signs including lordosis, caudal fin deformity,skin erosion and significantly (P < 0.05) suppressed weight gain and higher condition factor. Protein efficiency ratio and specific growth rate were significantly (P < 0.05) improved with increasing levels ofvitamin C up to 200 mg kg-1 diets. Tissues (liver, kidney, gills and muscle) ascorbate concentration generally reflected dietary inclusion levels with significant (P < 0.05) lowest level occurring in thecontrol groups. The dietary requirement based on least mean squares error regression analysis of weight gain and specific growth rate data on inclusion level of vitamin C was 82.2 ± 0.2 mg vitamin C kg-1 diet which corresponds to 100 mg of vitamin C kg-1 diet

Toxicity of cassava wastewater effluents to African catfish: Clarias gariepinus (Burchell, 1822)

The relative lethal and sublethal toxicity of cassava wastewater effluents from a local food factory were investigated on Clarias gariepinus fingerlings using a renewable static bioassay. The physico-chemical characteristics of the cassava wastewater effluents showed a number of deviations from the standards of the Federal Environmental Protection Agency (FEPA) on the guidelines for effluent discharges. Considering the pollutants of the effluent, cyanide (CN) is suspected to be primarily responsible for the toxicity, although synergistic effect of other pollutants cannot be ruled out. At each exposure, in the two tests, the test-organisms showed signs of serious stress, swimming pattern changed and mortality increased over relatively small increase in concentration. The LC50 for lethal and sublethal tests were 0.024 mg1-1 and 0.0064 mg1-1, respectively. The differences observed in the mortalities and bioconcentration of metals in fish muscles of varying concentrations were significant (

On the development of a coupled regional climate–vegetation model RCM–CLM–CN–DV and its validation in Tropical Africa

This paper presents a regional climate system model RCM-CLM-CN-DV and its validation over Tropical Africa. The model development involves the initial coupling between the ICTP regional climate model RegCM4.3.4 (RCM) and the Community Land Model version 4 (CLM4) including models of carbon-nitrogen dynamics (CN) and vegetation dynamics (DV), and further improvements of the models. Model improvements derive from the new parameterization from CLM4.5 that addresses the well documented overestimation of gross primary production (GPP), a refinement of stress deciduous phenology scheme in CN that addresses a spurious LAI fluctuation for drought-deciduous plants, and the incorporation of a survival rule into the DV model to prevent tropical broadleaf evergreens trees from growing in areas with a prolonged drought season. The impact of the modifications on model results is documented based on numerical experiments using various subcomponents of the model. The performance of the coupled model is then validated against observational data based on three configurations with increasing capacity: RCM-CLM with prescribed leaf area index and fractional coverage of different plant functional types (PFTs); RCM-CLM-CN with prescribed PFTs coverage but prognostic plant phenology; RCM-CLM-CN-DV in which both the plant phenology and PFTs coverage are simulated by the model. Results from these three models are compared against the FLUXNET up-scaled GPP and ET data, LAI and PFT coverages from remote sensing data including MODIS and GIMMS, University of Delaware precipitation and temperature data, and surface radiation data from MVIRI and SRB. Our results indicate that the models perform well in reproducing the physical climate and surface radiative budgets in the domain of interest. However, PFTs coverage is significantly underestimated by the model over arid and semi-arid regions of Tropical Africa, caused by an underestimation of LAI in these regions by the CN model that gets exacerbated through vegetation dynamics in RCM-CLM-CN-DV