Pansteatitis in polluted Olifants River impoundments: nutritional perspectives on fish in a eutrophic lake,Lake Loskop,South Africa

This study compares the aetiology of pansteatitis in Lake Loskop, relative to two other impoundments along the Olifants River. Macroscopic and microscopic pathology, age determination and analysis of stomach content, fatty acids and stable isotopes explain the high prevalence of pansteatitis in Oreochromis mossambicus (Peters) and several other species in Lake Loskop. All the dietary indicator comparisons between pansteatitis‐affected and healthy fish fail to support a systemic cause. Pansteatitis in Lake Loskop was linked to size and weight of O. mossambicus, but not to ontogenic age. Fish in Lake Loskop showed abnormally high omega‐3 to omega‐6 fatty acid ratios normally only found in marine fish with no significant difference in degree of assimilation of these fatty acids between pansteatitis‐affected and healthy fish. This explains the vulnerability to, but not the occurrence of, pansteatitis. As a cause for the pansteatitis, these results point towards sporadic vitamin E‐depleting trigger events, known sporadic fish die‐off occurrences that provide surviving fish with a rich source of rancid fats on which to scavenge. The mechanism ties pansteatitis to eutrophication and trophic cascade effects, the intrinsic drivers of the disease and suggests an adaptive management strategy that might be applied by relevant conservation authorities.     

Single nucleotide polymorphisms in the growth hormone gene of Oreochromis niloticus and their association with growth performance

Polymorphisms in the growth hormone (GH) gene that is associated with the growth rate of farmed fish have been the target of many breeding programmes. The present study aimed to identify single nucleotide polymorphisms (SNPs) in GH gene regions to evaluate the association of SNP variations with the growth rate of two Nile tilapia: Oreochromis niloticus (Linnaeus, 1758) strains. The targeted regions were amplified, sequenced, aligned and screened for the presence of SNPs; thereafter, performance tests were used to check for the association between SNPs and weight. Allele and genotype frequencies were estimated for each SNP and genotype. Genotype blocks or sets of SNP genotypes and frequencies were also estimated. Association between SNPs and growth rate was statistically evaluated using a univariate linear mixed model that included both fixed and random effects. A total of 10 SNPs were identified, nine in the proximal promoter and one located in the 5′ UTR, forming 10 genotype blocks. In all weight recordings, five genotype blocks were significantly associated with the highest weights. Single nucleotide polymorphisms 6‐10 were also found to be significantly associated with growth (p‐value < .05). Genotypes with higher additive genetic values for weight were identified in the Chitralada strain, suggesting a possible impact of these additive effects of the GH SNP genotype on the growth rate of Nile tilapia. These findings may be used as part of marker‐assisted selection in tilapia breeding programmes.     

Application of morphometric measures in estimation of body weight and discrimination of Astyanax lacustris and Astyanax fasciatus

The objective of this study was to verify the direct and indirect correlation between morphometric measures, ratios, body weight and yield in two lambari species Astyanax lacustris and Astyanax fasciatus and whether the discriminant analysis is capable of separating and allocating the species. We used 102 lambari yellow tail and 60 lambari red tail. The fish were weighed and submitted to the evaluation of the morphometric measurements. The direct and indirect effects were evaluated by the method of track analysis, considering weight at slaughter, weight of body parts and body yields as dependent variables and measures and morphometric ratios as explanatory variables. Astyanax lacustris presented higher height and body width, carcass yield and trunk, while A. fasciatus presented higher head yield and viscera weight. The discriminant analysis was able to classify 79.5% of the two species. Track analysis demonstrated that the morphometric measurements can be used for estimation of body and body components’ weight in A. lacustris and A. fasciatus. However, regarding the corporal yield; the morphometric measures were insufficient to explain the yield variations of the species.     

Lethal concentration of Cymbopogon citratus (Poaceae) essential oil for Dolops discoidalis and Argulus sp. (Crustacea: Argulidae)

This study investigated the acute toxicity (LC_50-24 hr) effects of the essential oil of Cymbopogon citratus for adult Argulus sp. and Dolops discoidalis, before and during oviposition. In vitro acute toxicity (LC_50-24 hr) was tested using 20, 40, 60, 80, 100, 120, 140 and 160 μg/L of C. citratus essential oil, and two control groups (one with cultivation tank water and one with cultivation tank water + alcohol) were used. Specimens of Argulus sp. and D. discoidalis submitted to acute toxicity were evaluated using histological procedures. The major chemical compounds of C. citratus essential oil were geranial (47.5%), neral (35.6%) and myrcene (6.7%). The LC_50-24 hr for Argulus sp. adults was 67.97 μg/L, while for D. discoidalis it was 59.55 µg/L. In the oviposition of both species of argulids, maximum mortality began with treatments of 140 μg/L, while the LC_50-24 hr for Argulus sp. and D. discoidalis was 83.98 μg/L and 82.48 μg/L, respectively. In both argulid species exposed to C. citratus essential oil, morphological alterations were observed only in the eyes, and they occurred in the ommatidium and rhabdomeres and were dependent on the concentration of C. citratus essential oil and the parasite species.     

Unraveling the morphological patterns of a subantarctic eelpout: a geometric morphometric approach

Phenotypic variation in organisms depends on the genotype and the environmental constraints of the habitat that they exploit. Therefore, for marine species inhabiting contrasting aquatic conditions, it is expected to find covariation between the shape and its spatial distribution. We studied the morphology of the head and cephalic sensory canals of the eelpout Austrolycus depressiceps (4.5–22.5 cm TL) across its latitudinal distribution in South Pacific (45°S–55°S). Geometric morphometric analyses show that the shape varied from individuals with larger snout and an extended suborbital canal to individuals with shorter snouts and frontally compressed suborbital canal. There was size variation across the sampled populations, but that size does not have a clear latitudinal gradient. Only 8% of the shape variation relates to this size variation (allometry), represented by a decrease in the relative size of the eye, and a depression of the posterior margin of the head. There were spatial differences in the shape of the head, but these differences were probably caused by allometric effects. Additionally, 2 of the canals of the cephalic lateralis pores and the head shape showed modularity in its development. This study shows that the morphology of marine fish with a shallow distribution varies across distances of hundreds of kilometers (i.e., phenotypic modulation).     

Physicochemical and Structural Properties of Recovered Elastin from Jumbo Squid (Dosidicus gigas) By-Products

Physicochemical and structural properties of soluble jumbo squid (Dosidicus gigas) elastin recovered from skin by-products were evaluated. The molecular weight of isolated elastin was ~40 kDa with an isoelectric point (pI) between 9 and 10. Aspartic, glutamic, arginine, proline, glycine, and lysine amino acids were the most abundant in squid elastin, whereas the hydroxyproline absence, ~0.7% cysteine content, and the calculated 0.35 isoleucine/leucine ratio were used as purity index. Total and reactive sulfhydryl contents were similar (247.0 ± 5.1 vs 242.0 ± 7.5 μmol mg^?1 of protein, P ≥ 0.05) in purified squid elastin but surprisingly higher than previously reported in other elastins. On the other hand, the secondary structures of squid elastin analyzed by Fourier transform infrared spectroscopy (FTIR) were ~45% β-sheets, ~15% α-helices, ~10% β-turns, and ~30% undefined structures. In addition, squid elastin experienced glass transition at 82.01 ± 0.01ºC, denaturation temperature at 110.45 ± 0.64ºC, and aggregation at 197.5 ± 0.23ºC. In conclusion, the prevalence of charged amino acids and pI of squid elastin can facilitate its solubilization in hydrophilic systems, whereas the secondary structure profile and thermostability are desirable features in proteins used for biopolymer designs such as food biofilms or barrier systems.     

Impacts of population growth, economic development, and technical change on global food production and consumption

Over the next decades mankind will demand more food from fewer land and water resources. This study quantifies the food production impacts of four alternative development scenarios from the Millennium Ecosystem Assessment and the Special Report on Emission Scenarios. Partially and jointly considered are land and water supply impacts from population growth, and technical change, as well as forest and agricultural commodity demand shifts from population growth and economic development. The income impacts on food demand are computed with dynamic elasticities. Simulations with a global, partial equilibrium model of the agricultural and forest sectors show that per capita food levels increase in all examined development scenarios with minor impacts on food prices. Global agricultural land increases by up to 14% between 2010 and 2030. Deforestation restrictions strongly impact the price of land and water resources but have little consequences for the global level of food production and food prices. While projected income changes have the highest partial impact on per capita food consumption levels, population growth leads to the highest increase in total food production. The impact of technical change is amplified or mitigated by adaptations of land management intensities.     

Performance of four <Emphasis Type="Italic">Trichogramma</Emphasis> species (Hymenoptera: Trichogrammatidae) as biocontrol agents of <Emphasis Type="Italic">Heliothis virescens</Emphasis> (Lepidoptera: Noctuidae) under various temperature regimes

Trichogramma spp. are major parasitoids of lepidopteran pest eggs, but there is large variation in efficacy toward a given pest among the numerous described Trichogramma species. It is important to select the Trichogramma species that most effectively parasitize and develop in target pest eggs for biological control. In this context, Trichogramma pretiosum, T. exiguum, T. atopovirilia and T. acacioi were studied in Heliothis virescens eggs under different thermal conditions. The parasitoids were reared at constant temperatures of 20, 25 and 30°C and tested at these respective temperatures, while parasitoids reared at 25°C were also tested at 20 and 30°C, for a total of 20 species–temperature combinations. About 30 H. virescens eggs were offered to the parasitoids for 24 h. Among the four species, parasitism rate by T. atopovirilia was highest at all temperature conditions, whereas T. acacioi had the lowest rates of parasitism at 25°C and 25/30°C. Parasitism ranged from 13.8 to 43.8% among all species–temperature combinations. Viability (emerged parasitoids) ranged from 80.8 to 98.4%, and was deemed satisfactory. The emergence rates of T. exiguum and T. acacioi were affected by temperature. Temperature also affected the sex ratio of T. exiguum at 25/30°C, whereas T. pretiosum and T. acacioi produced females predominantly independent of temperature. Overall, the parasitoid T. atopovirilia was the most efficient in parasitizing H. virescens eggs, though the levels of parasitism obtained might not ensure its successful use in biological control programs. The temperature-related differences in biological traits observed in the four Trichogramma species tested hint at the importance of making careful choices regarding climatic conditions where the parasitoid is going to be used when selecting a species for biological control programs.     

Genetic variation and environmental stability of grain mineral nutrient concentrations in <Emphasis Type="Italic">Triticum dicoccoides</Emphasis> under five environments

Nineteen wild emmer wheat [Triticum turgidum ssp. dicoccoides (Körn.) Thell.] genotypes were evaluated for the grain concentrations of phosphorous (P), potassium (K), sulfur (S), magnesium (Mg), calcium (Ca), zinc (Zn), manganese (Mn), iron (Fe) and cooper (Cu) under five different environments in Turkey and Israel. Each mineral nutrient has been investigated for the (1) genotype by environment (G × E) interactions, (2) genotype stability, (3) correlation among minerals and (4) mineral stability. Among the macronutrients analyzed, grain concentrations of Ca (range 338–2,034 mg kg^?1) and S (range 0.18–0.43%) showed the largest variation. In the case of micronutrients, the largest variation was observed in the grain Mn concentration (range 13–87 mg kg^?1). Grain concentrations of Fe and Zn also showed important variation (range 27–86 and 39–115 mg kg^?1, respectively). Accessions with higher nutrient concentrations (especially Zn and Fe) had also greater grain weight, suggesting that higher grain Zn and Fe concentrations are not necessarily related to small grain size or weight. Analysis of variance showed that environment was the most important source of variation for K, S, Ca, Fe, Mn and Zn, explaining between 44 and 78% of the total variation and G × E explained between 20 and 40% of the total variation in all the minerals, except for S and Zn where its effect accounted for less than 16%. Genotype was the most important source of variation for Cu (explaining 38% of the total variation). However, genotype effect was also important for Mg, Mn, Zn and S. Sulfur and Zn showed the largest heritability values (77 and 72%, respectively). Iron exhibited low heritability and high ratio value between the G × E and genotype variance components \( \left( {\sigma_{\text{GE}}^{2} /\sigma_{G}^{2} } \right) \), suggesting that specific adaptation for this mineral could be positively exploited. The wild emmer germplasm tested in the current study revealed some outstanding accessions (such as MM 5/4 and 24-39) in terms of grain Zn and Fe concentrations and environmental stability that can be used as potential donors to enhance grain micronutrient concentrations in wheats.