Mutualism between euryhaline tilapia Sarotherodon melanotheron heudelotii and Chlorella sp.—Implications for nano-algal production in warmwater phytoplankton-based recirculating systems

The West-African euryhaline tilapia, Sarotherodon melanotheron heudelotii shift from visually feeding on zooplankton when juveniles to mostly filter feeding on phytoplankton when adults. When reared using an appropriate ration in intensive aquaculture systems, S. m. heudelotii also consume algal-based detritus, and contribute to sediment mineralization, clean up their environment, and ultimately stimulate and sustain algal growth. We analysed such practical advantages for phytoplankton-based recirculating systems, using S. m. heudelotii and Chlorella sp. as biological material originating from the prototype of such a system operated in Senegal. We performed a 24-h factorial design experiment in 36 tubs, cross-classifying three levels of S. m. heudelotii (fishless control, unfed fish, and fed fish) with four levels of Chlorella initial density.Chlorella overall mean density increased significantly from fishless, to unfed fish, and fed fish treatments, and with Chlorella initial density. S. m. heudelotii did not alter nitrogen nor phosphorus concentrations, only affected by algal initial densities. Most ammonia excreted by fish was probably uptaken by Chlorella. Bacteria-mediated diurnal nitrification was possibly an alternative ammonium loss mechanism at highest oxygen concentrations. Algae were not limited by nitrogen or phosphorus but most likely by low dissolved organic carbon availability. Chlorella differential responses with fed vs. unfed Sarotherodon suggest that CO₂ supplied by heterotrophic S. m. heudelotii respiration played a key role. Observed Chlorella growth rates were similar to the highest rates obtained in algal mass cultures, enriched with CO₂, nitrate and phosphate, under artificial lighting.Our results suggest the existence of a Sarotherodon-Chlorella mutualism in our systems, where S. m. heudelotii provide CO₂, the major limiting factor of Chlorella growth, whereas Chlorella oxygenate and detoxify the water media from ammonia, promoting S. m. heudelotii production. This mutualism could be used to optimize photosynthetic suspended-growth aquaculture systems, particularly in the Tropics where light is abundant and temperature is continuously high.     

Chronic cryptosporidiosis in Australian elapid snakes: control of an outbreak in a captive colony

An outbreak of chronic cryptosporidiosis resulting in hypertrophic gastritis occurred in a captive colony of Australian elapid snakes. Two species of the genus Notechiswere involved: Notechis ***ater(Black Tiger Snake) and Notechis scutatus (Eastern or Mainland Tiger Snake). The infection was eventually fatal in all 9 affected snakes. Typical histopathological findings of the stomach included mucosal thickening with cystic dilatation of gastric glands, moderate oedema and fibrosis of the lamina propria, and a mild to moderate patchy infiltration of inflammatory cells. Procedures implemented to contain the outbreak included the use of a formaldehyde-based disinfectant, prompt removal of faecal matter, uneaten and regurgitated food from enclosures, and examination of faecal specimens for Cryptosporidium oocysts and other pathogens.     

How to enhance crop production and nitrogen fluxes? A result-oriented scheme to evaluate best agri-environmental measures in Veneto Region,Italy

The cost-effectiveness of adopting agri-environmental measures (AEMs) in Europe, which combine agricultural productions with reduced N losses, is debated due to poorly targeted site-specific funding that is allocated regardless of local variability. An integrated DAYCENT model-GIS platform was developed combining pedo-climatic and agricultural systems information. The aim was to evaluate best strategies to improve N fluxes of agro-ecosystems within a perspective of sustainable intensification. Indicators of agronomic efficiency and environmental quality were considered. The results showed that agronomic benefits were observed with a continuous soil cover (conservation agriculture and cover crops), which enhanced nitrogen use efficiency (+17%) and crop yields (+34%), although in some cases these might be overestimated due to modelling limitations. An overall environmental improvement was found with continuous soil cover and long-term change from mineral to organic inputs (N_Leach < 10 kg ha^?1 a^?1, N-N₂O emissions < 1 kg ha^?1 a^?1, soil C stock > 45 Mg ha^?1), which were effective in the sandy soils of western and eastern Veneto with low SOM, improving the soil-water balance and nutrients availability over time. Results suggest that AEM subsidies should be allocated at a site-specific level that includes pedo-climatic variability, following a result-oriented approach.     

Daily illumination exposure and melatonin: influence of ophthalmic dysfunction and sleep duration

Background  

Ocular pathology lessens light's efficacy to maintain optimal circadian entrainment. We examined whether ophthalmic dysfunction explains unique variance in melatonin excretion of older adults over and above the variance explained by daily illumination, medical, and sociodemographic factors. We also examined whether ophthalmic dysfunction influences relationships between ambient illumination and melatonin.     

Bacterial community structure of glacier forefields on siliceous and calcareous bedrock

Forefields of retreating glaciers represent unique opportunities to investigate the initial phases of soil formation and microbial interactions with mineral surfaces. An open question concerns the physical and chemical driving‐factors affecting the establishment of microbial communities in these young ecosystems. In this study we compared the bacterial community structure of six glacier forefield soils belonging to two contrasting bedrock categories (calcareous and siliceous) through T‐RFLP profiling of the 16S rRNA gene. The community profiles were correlated with an array of physical (soil texture, water holding capacity, hours of sunshine, temperature, rainfall and exposure) and chemical (TC, TN, DOC, extractable nutrients and pH) factors using canonical correspondence analysis (CCA). A first comparison of the T‐RFLP profiles suggested that the degree of operational taxonomic unit (OTU) diversity of these soils was similar, and that community structure was dominated by ubiquitous taxa. CCA showed that both physical (e.g. hours of sunshine or rainfall) and chemical factors (e.g. SO²⁻₄ or PO³⁻₄) played an equal role in shaping the soil bacterial communities. OTUs unique to specific sites appeared to be strongly influenced by the climatic regime and by texture. Overall, the community structure of the six glacial forefields showed no clear dependence on the bedrock categories.     

Comparative performance of the red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae) on different plant diets

Tribolium castaneum is a pest of stored foods that causes serious economic losses. Understanding insect nutritional requirements and the effects of different diets on insect development can provide tools for developing strategies to control insect and integrated pest management systems. In this work we studied the performance of the T. castaneum on different plant diets composed of Vigna unguiculata, Phaseolus vulgaris and wheat flours. The diets interfered differentially with development and insect survival. Larvae size was reduced about 60 % in larvae fed with V. unguiculata flour. A delay in pupae formation was also observed. The larval mortality of 100 % was observed in the P. vulgaris diet. Carbohydrate and triglyceride showed variations during development and with different diets. Larvae fed with wheat diets showed a high concentration of carbohydrates 21 days after hatching (DAH) and triglyceride at 15 and 21 DAH. Larvae fed with wheat diets showed α-amylase activity during development. At 15 DAH the activity of larvae fed with V. unguiculata increased about 50 %. Cysteine protease activity in larvae fed with wheat remained high throughout development. Serine protease activity also varied according to diets. These results show that the nutritional state of developing larvae varies greatly with respect to triglycerides, carbohydrate and digestive enzymes depending on the diet and larval stage. Altogether, these results show that changes in dietary nutrients can interfere with insect physiology. Therefore changes in diet composition that may deprive insects of essential nutrients or include toxic compounds might be a good control strategy for stored product pests.