A new<Emphasis Type="Italic">Praon</Emphasis> species (Hymenoptera: Braconidae: Aphidiinae) of the<Emphasis Type="Italic">Uroleucon</Emphasis> parasitoid complex from the mediterranean area

A new hymenopteran aphid parasitoid species (Praon uroleucon sp. n.) fromUroleucon sp. infestingCarduus acanthoides L. is described from Yugoslavia. It is diagnosed and illustrated with scanning electron microscope photographs and line drawings. The new species is placed in thePraon dorsale species group, and a key to species of that group is provided. http://www.phytoparasitica.org posting Dec. 9, 2002.     

Osteomalacia as a result of phosphorus deficiency in beef cattle grazing subtropical native pastures in Uruguay

We investigated 2 outbreaks of osteomalacia as a result of phosphorus (P) deficiency in herds of lactating beef cows grazing subtropical native pastures in Uruguay. Cows exhibited pica, difficulty to stand and walk, rib fractures, and body weight loss even with adequate forage availability. Osteopenia and severe osteomalacia were observed on gross and histologic examination. The concentrations of bicarbonate-extractable P in soil (4.0, 4.1 mg P/kg), total P in pasture (0.9, 1.1 g P/kg), inorganic P in serum (1.0, 0.71 mmol P/L), and P in bone (73 mg P/mL) were all low. Although injectable and mineral salt supplements provided additional P in both outbreaks, these supplementary amounts were insufficient to prevent P deficiency. The P ingested by the cows from the pasture and supplements would have provided 20–55% of their daily P requirements of ~21 g P/d. Osteomalacia occurred in cattle at the 2 ranches as a result of severe P deficiency in the soil and forage, and inadequate P supplementation. Following diagnosis, control of P deficiency in beef cattle requires estimation of the amount of pasture P ingested and provision of sufficient additional supplementary P to meet the animals’ requirements.     

Habitat structure and prey aggregation determine the functional response in a soil predator-prey interaction

Functional responses describe the per capita consumption rates of predators depending on prey density, which quantifies the energy transfer between trophic levels. We studied a typical interaction of the litter-soil systems between hunting spiders (Pardosa lugubris; Araneae: Lycosidae) and springtails (Heteromurus nitidus; Collembola: Entomobryidae) at varying habitat structure, i.e. with moss vs. without moss. We found a hyperbolic increase in consumption (functional response type II) in the treatment without habitat structure that was converted into a roller-coaster (or dome-shaped in a broad sense) functional response in treatments with habitat structure. Additional experiments suggest that the reduced per capita consumption rates at high prey densities may be explained by aggregative defence behaviour of the springtails. Experimentally, this behaviour was induced by the presence of habitat structure. We analyzed the net-energy gain of this predator-prey interaction by comparing the predator’s metabolic energy loss to its energy gain by consumption. In treatments with habitat structure, the net-energy gain of the predator was limited at intermediate prey densities where prey aggregation reduced the consumption rates. Our results stress the importance of habitat structure and prey behaviour in shaping the functional response in a typical soil-litter predator-prey interaction.     

Weed management and irrigation are key treatments in emerging black truffle (Tuber melanosporum) cultivation

Interest in conversion of marginal agricultural lands to small oak woodlands for the production of black truffles (Tuber melanosporum Vittad.) is increasing in the native black truffle areas of France, Spain and Italy as well as suitable or amended sites throughout the world due to high economic returns for gastronomically valuable truffles. Successful long-term management of a perennial plantation replacing an annual crop requires understanding the system in all phases of the life cycle, and in the case of truffles this involves understanding the interactive growth of the aboveground host and the belowground symbiotic ectomycorrhizal fungus whose fruitbody is the desired truffle. Here we focus on the pre-production phase, 4 years after establishing the truffle-oak plantation and prior to truffle production. We tested the influence of weed control, irrigation and fertilizer, each at 3 levels, on plant growth and ectomycorrhizal proliferation in three truffle-oaks plantations in northeast Spain. Results show that adequate weed control improves root and shoot dry weight while fertilizer and irrigation treatments did not influence plant growth. The low dose of irrigation (50% of the estimated water deficit for the site) and glyphosate weed control both increased total root tips/plant and T. melanosporum colonized tips (ectomycorrhizae) by approximately two-fold, compared to control treatments. Distribution of the ectomycorrhizae within the soil profile was significantly influenced by the low dose irrigation treatment, with increases observed in the 10?C20 cm and the 20?C30 cm deep layers compared to the control and high irrigation treatments. Four years after planting, T. melanosporum remained the dominant fungal symbiont, despite the presence of 14 other ectomycorrhizal morphotypes from these sites.     

Nutritional and physiological responses of young growing rats to diets containing raw cowpea seed meal,protein isolate (globulins), or starch

The nutritional and physiological effects of raw cowpea (Vigna unguiculata (L) Walp.) seed meal, protein isolate (globulins), or starch on the metabolism of young growing rats have been evaluated in 14-day trials. Wet and dry weight gain, feed conversion efficiency, and lipid and protein accretion were significantly reduced as a result of inclusion of seed meal, globulins, or starch in the diet, with growth retardation being most marked with the seed meal. The proportional weights of the small intestine and pancreas were increased by meal diets, and serum cholesterol levels were slightly reduced. The globulins and raw starch also increased relative small intestine weights but had no effect on the pancreas or serum constituents. The effects of cowpeas on rats appeared to be due primarily to the combined actions of globulins, resistant starches, protease inhibitors, and possibly fiber and non-starch polysaccharides on intestinal and systemic metabolism.     

A new<Emphasis Type="Italic">Aphidius</Emphasis> species (Hymenoptera: Braconidae: Aphidiinae) from high-montane areas of southeastern Europe

Aphidius montenegrinus sp.n. from Serbia and Montenegro is described and illustrated. It parasitizedAcyrthosiphon daphnidis Ilharco, onDaphne alpina L. The parasitoid was described and illustrated using scanning electron microscope photographs and line drawing. The new species is a member of theAcyrthosiphon aphid parasitoid guild and was collected from Zabojsko Jezero Lake in Montenegro. The parasitoid and the hyperparasitoid spectrum ofA. daphnidis are presented for the first time. http://www.phytoparasitica.org posting April 30, 2004.     

Effect of the addition of Chaetoceros calcitrans,Navicula sp. and Phaeodactylum tricornutum (diatoms) on phytoplankton composition and growth of Litopenaeus vannamei (Boone) postlarvae reared in a biofloc system

The aim of this study was to evaluate the effect of the addition of Chaetoceros calcitrans, Navicula sp. and Phaeodactylum tricornutum (diatoms) on phytoplankton composition and the growth of Litopenaeus vannamei postlarvae reared in a biofloc system . Four treatments were used: BFT (biofloc system without feed and no addition of diatoms); BFT‐F (biofloc system with feed and no addition of diatoms); BFT‐D (biofloc system with the addition of diatoms and no feed); and BFT‐FD (biofloc system with the addition of feed and diatoms), all in triplicate. The shrimp (16 ± 0.02 mg) were stocked at 2500 postlarvae m^?3 and fed a commercial feed. Diatoms were added on the 1st, 5th, 10th and 15th day at a density of 5 × 10⁴ cells mL^?1 for each species. No significant differences (P > 0.05) between treatments were observed for gross primary production, net ecosystem production and water column respiration rate. However, significant differences (P < 0.05) were observed for nitrite, orthophosphate, alkalinity, final weight, weight gain, yield, feed conversion ratio (FCR), phytoplankton and cyanobacteria composition. The BFT‐FD treatment had better performance parameters for final weight (270 mg), weight gain (254 mg), yield (0.67 Kg m^?3) and FCR (0.61), indicating the benefits of the diatoms C. calcitrans, Navicula sp. and P. tricornutum for decreasing cyanobacteria and improving growth of L. vannamei postlarvae reared in biofloc systems.