Growth responses and fatty acid composition of juvenile prawns (Macrobrachium rosenbergii) fed a prepared ration augmented with shrimp head oil

A prepared shrimp food was impregnated at 3% by weight with oil extracted from heads of Penaeus setiferus. This procedure brought about a reduction in the level of ω6 fatty acids and an increase in the percentages of ω3 fatty acids and saturated acids in the diet.The lipid-augmented ration was fed to juvenile Macrobrachium rosenbergii for 12 weeks in the laboratory, with the unmodified diet as a control. Prawns fed the augmented diet grew significantly larger than those given the control feed, and this difference was apparent by the sixth week of the study. Final mean biomass (g prawn/m² of tank floor) and efficiency of food utilization in the experimental group were about twice that in the control. Survival in the two groups was similar throughout the study and averaged 71 and 68%, respectively, for the experimental and control animals at the end of the experiment.Prawns fed both rations contained in their tissues about the same percentage of ω3 fatty acids as their diets, indicating conservation of these dietary acids and/or biosynthesis. In contrast, the animals contained substantially less 18:2ω6 (linoleic acid) than their diets, and the data suggested that some of this fatty acid may have been utilized as an energy source. Also, animals fed the augmented diet contained about 15 times more carotenoid pigments than those given the control ration.The study suggests that ω3 fatty acids are important in the nutrition of M. rosenbergii and that prawn diets might be made more effective by increasing the relative proportion of ω3 fatty acids in their composition. Waste shrimp heads may be one suitable source of fatty acids and pigments for use in prepared diets for aquaculture.     

Effects of dietary cottonseed meal protein level on growth, gonad development and plasma sex steroid hormones of tropical fish tilapia Oreochromis sp

Five experimental diets containing increasing proportions of cottonseedmeal (CSM) protein (0, 25, 50, 75 and 100%; diets 1 to 5, respectively) toreplace fish meal (FM) protein were formulated for intensive culture of tilapiaOreochromis sp. Each diet was fed to three replicategroupsof fish (mean weight ± SE = 11.3 ± 3.9 g) in30L aquaria connected as a closed recirculating-water system andmaintained at 27 ± 1 °C. Fish were fed three times adayby hand at a rate of 3% of body weight during four weeks, after which thefeeding rate was gradually decreased to reach 1.5% at 16 weeks. Thesubstitutionof 75 and 100% of FM proteins by CSM proteins resulted in significantly lowerbody weights in both sexes. In both sexes, gonadosomatic indexes and plasmaconcentrations of sex steroids (testosterone, 11-ketotestoterone,estradiol-17 and 17,20-dihydroxy-4-pregnen-3-one) were notsignificantly different among dietary treatments. The concentration ofgossypol,an antifertility agent contained in CSM, was measured in reproductive tissues.The total gossypol concentration in the testis was consistently lower than thatmeasured in the ovaries of the same group. Moreover, in both sexes, theconcentration of the (+)isomer of gossypol was always higher than that of(–)isomer. The total gossypol concentrations in testes increasedsignificantly with the increase of CSM in the diet. The highest levels of the(+)isomer (7.64 ± 0.62 g g^–1)were found in the testes of fish fed diet 4, whereas the (–)isomerreached its highest values in the testes of fish fed diet 5. The highest levelsof both enantiomers of gossypol were found in the ovaries of fish fed diet 4(14.2 ± 2.7 and 5.6 ± 1.5 g g^–1for (+) and (–)isomers, respectively). In both sexes, thehistological analysis of the gonads did not reveal differences among the fishfed different levels of CSM. Although CSM at any levels did not affect thereproductive parameters examined in this study, it cannot be used to substitutemore than 50% of FM since at higher levels growth of tilapia was compromised.     

Alteration of certain blood parameters of freshwater teleost <Emphasis Type="Italic">Mystus vittatus</Emphasis> after chronic exposure to Metasystox and Sevin

Indiscriminate use of pesticides has elevated the risk of contamination of environment and aquatic habitat. Considering the above fact, the present study has been under taken to investigate the alteration of some blood parameters of freshwater teleost Mystus vittatus after chronic exposure to sublethal concentrations of Metasystox (4 ppm.) and Sevin (7 ppm.) individually. The main alterations observed in certain haematological parameters were clotting time (CT), erythrocyte sedimentation rate (ESR), haemoglobin percentage (Hb%), red blood corpuscles (RBCs), white blood corpuscles (WBCs), pack cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC). Alterations in organic constituents of blood, such as glucose, blood urea, total plasma protein and cholesterol, and in inorganic constituents, such as calcium, iron, magnesium, and phosphorus, were also studied. Alteration of enzymes such as glucose-6-phosphatase (G-6-pase), fructose-1-6-diphosphatase (F-1-6-dipase), serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) were also studied, so that the changes in the blood biochemistry due to the pesticidal stress could be understood. Results indicated that CT, WBCs, MCH, MCHC, glucose, blood urea, cholesterol, magnesium and SGOT were increased, whereas other parameters were found to be decreased in both cases. Possible reasons for the above elevation are discussed in the light of available literature.     

Use of diet and body condition assessments as intermediate indicators of translocation success in the Critically Endangered Philippine crocodile (Crocodylus mindorensis)

1. Intermediate metrics of translocation success are useful for long-lived, slow to mature species where survival and reproduction happen over decades.
2. With fewer than 150 individuals in the wild, the Critically Endangered Philippine crocodile (Crocodylus mindorensis) is one of the most threatened species on Earth. This study presents the first analysis of diet and body condition of wild Philippine crocodiles and headstarted (i.e. captive-reared) individuals released into the wild over the last decade, and uses these results to show how diet and body condition can be pertinent intermediate metrics of translocation success.
3. Analyses of stomach contents revealed 17 different aquatic and terrestrial invertebrate and vertebrate prey species. Interestingly, 70% of Philippine crocodiles showed snails to be the predominent prey type, followed by fish (36.7%), birds (33.3%) and reptiles (33.3%). More than 50% of crocodiles consumed the invasive golden apple snail, a leading agricultural pest. Regardless of crocodile history (wild vs. headstarted) or size class (juvenile vs. adult), no evidence was found for dietary differences in percentage occurrence, percentage composition or prey diversity.
4. Body condition was significantly higher in wild compared with headstarted individuals when analysed together in a pooled group, although neither group differed significantly from the standardized expectation, and headstarted individuals were not significantly different when body condition was derived independently for the two groups.
5. This study provides a working example of how assessing the convergence of diet and body condition between translocated and wild individuals can provide complementary monitoring parameters to demonstrate post-release establishment of translocated crocodylians. The congruent dietary composition and comparable body condition observed in this study suggest that headstarted crocodiles adapt well following release.
6. Crocodylus mindorensis survives in an agricultural landscape and is likely to play an ecologically important role by exploiting invasive species, reinforcing the importance of this species to local communities.

     

The Value of Seed Potatoes from Four Systems in Kenya

Although potatoes are the second most valuable crop in Kenya, poor seed potato quality has limited industry expansion. The objectives of this study were to describe the seed potato system, identify problems, determine use of high-quality seed and estimate farmer willingness to pay (WTP) for different types of seed. Data was collected from interviews, forums and surveys. A contingent valuation method (CVM) model was also developed to analyze the factors that influence farmer WTP. It was found that the seed system consists of three sub-components: Formal, Semi-Formal and Farmer. More than 96 % of Kenya seed potatoes were produced in the Farmer category, and were considered to be poor quality. Growers identified bacterial wilt, viral diseases and late blight as the most serious problems. The WTP model revealed that farmer age, distance to seed source, potato training, gender and region were statistically significant explanatory variables. The study recommends that training be conducted to increase production of “clean seed” and “positively-selected seed” in the Semi-Formal part of the seed system.     

Rhizosphere microbiomes can regulate plant drought tolerance

Beneficial root-associated rhizospheric microbes play a key role in maintaining host plant growth and can potentially allow drought-resilient crop production. The complex interaction of root-associated microbes mainly depends on soil type, plant genotype, and soil moisture. However, drought is the most devastating environmental stress that strongly reduces soil biota and can restrict plant growth and yield. In this review, we discussed our mechanistic understanding of drought and microbial response traits. Additionally, we highlighted the role of beneficial microbes and plant-derived metabolites in alleviating drought stress and improving crop growth. We proposed that future research might focus on evaluating the dynamics of root-beneficial microbes under field drought conditions. The integrative use of ecology, microbial, and molecular approaches may serve as a promising strategy to produce more drought-resilient and sustainable crops.     

Multi-scale factors affecting bird use of isolated remnant oak trees in agro-ecosystems

With recent emphasis on sustainable agriculture, conservation of native biota within agricultural systems has become a priority. Remnant trees have been hypothesized to increase biological diversity in agro-ecosystems. We investigated how remnant Oregon white oak (Quercus garryana) trees contribute to conserving bird diversity in the agro-ecosystem of the Willamette Valley, Oregon, USA. We compared bird use of isolated oak trees in three landscape contexts - croplands, pastures, and oak savanna reserves - and ranked the relative importance of four factors thought to influence bird use of individual trees: (i) tree architecture; (ii) tree isolation; (iii) tree cover in the surrounding landscape; and (iv) landscape context, defined as the surrounding land use. We evaluated species-specific responses and four community-level responses: (i) total species richness; (ii) richness of oak savanna-associates; (iii) tree forager richness; and (iv) aerial and ground forager richness. We documented 47 species using remnant oaks, including 16 species typically occurring in oak savanna. Surprisingly, landscape context was unimportant in predicting frequency of use of individual trees. Tree architecture, in particular tree size, and tree cover in the surrounding landscape were the best predictors of bird use of remnant trees. Our findings demonstrate that individual remnant trees contribute to landscape-level conservation of bird diversity, acting as keystone habitat structures by providing critical resources for species that could not persist in otherwise treeless agricultural fields. Because remnant trees are rarely retained in contemporary agricultural landscapes in the United States, retention of existing trees and recruitment of replacement trees will contribute to regional conservation goals.     

Photostabilization of biocontrol agents by berberine

We studied the photostabilizing effect of the isoquinoline alkaloid berberine on the following three model photounstable biocontrol agents: the bacterium Bacillus thuringiensis ( Bt ), the baculovirus Spodoptera littoralis nucleopolyhedrosis virus ( SlNPV ), and the entomopathogenic fungus Beauveria bassiana . The photoprotection provided by berberine was evaluated following various periods of simulated sunlight-UV irradiation. Insecticidal activity of Bt and SlNPV , as well as the rate of B. bassiana spore germination served as parameters for the photostabilizing effects. Only a berberine- Bt complex is effective, as practically no photostabilization was evident by just mixing the two components. The UV-sensitive SlNPV and B. bassiana spores were considerably photostabilzed by berberine. The role of the cationic nature of the berberine molecule and the importance of its absorbance spectrum in photostabilization of biocontrol agents are discussed.