Some exclusion cages do not exclude predators

Exclusion techniques, such as cages, are the most frequently used means of evaluating the efficiency of natural enemies in suppressing the abundance of their prey. The growth rates and peak densities of aphid populations within cages are usually larger than those in uncaged populations. However, cages change the microenvironment and prevent aphids from emigrating. Attempts were made to avoid the change in the microenvironment by using cages with a large (8 mm) mesh. Here we test the hypothesis that because of the large mesh size, predators can easily penetrate into such cages during an experiment. Our results have shown that cages with a large (8 mm) mesh size do not prevent predators from entering the cages and therefore cannot be used as “exclusion cages” for measuring the effect of predators on aphid numbers. Other methods of assessing the effectiveness of natural enemies in reducing the abundance of their prey, like removing the predators or direct observations, should be used instead

Influence of species composition of biocorridors on the abundance of aphids in cereal fields

Agriculture intensification in most European countries over the last 50 years resulted in a significant loss of biodiversity in agro-ecosystems. Attempts are now being made to restore originally complex agricultural landscapes by splitting large fields into smaller units using biocorridors, which are linear elements consisting of trees and shrubs. Such non-crop habitats can act as refuges both for insect predators that may potentially act as biocontrol agents and for insect pests. Bird cherry, Prunus padus (L.), is a winter host of a cereal pest and vector of cereal virus, the aphid Rhopalosiphum padi (L.), and is commonly planted in these biocorridors. The question arises, whether and to what extent the presence and distribution of P. padus in biocorridors influences the abundance of R. padi in nearby fields. This was addressed by monitoring spatial and temporal population dynamics of R. padi in two fields each adjacent to the newly established biocorridor but adjacent to parts of the corridor with different species compositions (only one with P. padus). Our results showed that this aphid colonized the field adjacent to that part of the corridor with P. padus but not the other field. In the second field colonization started close to one edge distant from the corridor and with no P. padus in the vicinity. After excluding the variability explained by spatial and temporal factors we also tested for the effect of environmental factors (weather conditions) on the remaining variability. Of the environmental factors tested, humidity accounted for most of the variability

Nonlinearities lead to qualitative differences in population dynamics of predator-prey systems.

Since typically there are many predators feeding on most herbivores in natural communities, understanding multiple predator effects is critical for both community and applied ecology. Experiments of multiple predator effects on prey populations are extremely demanding, as the number of treatments and the amount of labour associated with these experiments increases exponentially with the number of species in question. Therefore, researchers tend to vary only presence/absence of the species and use only one (supposedly realistic) combination of their numbers in experiments. However, nonlinearities in density dependence, functional responses, interactions between natural enemies etc. are typical for such systems, and nonlinear models of population dynamics generally predict qualitatively different results, if initial absolute densities of the species studied differ, even if their relative densities are maintained. Therefore, testing combinations of natural enemies without varying their densities may not be sufficient. Here we test this prediction experimentally. We show that the population dynamics of a system consisting of 2 natural enemies (aphid predator Adalia bipunctata (L.), and aphid parasitoid, Aphidius colemani Viereck) and their shared prey (peach aphid, Myzus persicae Sulzer) are strongly affected by the absolute initial densities of the species in question. Even if their relative densities are kept constant, the natural enemy species or combination thereof that most effectively suppresses the prey may depend on the absolute initial densities used in the experiment. Future empirical studies of multiple predator - one prey interactions should therefore use a two-dimensional array of initial densities of the studied species. Varying only combinations of natural enemies without varying their densities is not sufficient and can lead to misleading results

The Potential Impacts by the Invasion of Insects Reared to Feed Livestock and Pet Animals in Europe and Other Regions: A Critical Review

29 pages.-- This is an open access article distributed under the Creative Commons Attribution LicenseWhile the use of alien insect species for food and feed can help to alleviate protein shortage and provide for a more sustainable feed production, their invasive potential should be considered since invasive alien species represent one of the five main global threats to biodiversity. In the European Union (EU), eight insect species have already been authorized to be used as feed ingredients for aquaculture organisms, pets, poultry, and pigs. These species were selected based on available national risk assessments, as most of them are non-native to Europe. However, it is not clear how these risk assessments truly consider all EU bioregions, given that the information used was mostly biased towards northern European regions. As a large proportion of invasive alien species already present in the EU were introduced unintentionally, it is therefore crucial to understand and manage the potential pathways of such introductions in a more effective way. Here, we provide a critical overview of the potential risks of rearing alien insect species as feed or as pet food (for both livestock and exotic pets) in the EU. The results showed that some of these insect species have an invasive potential, either due to their reproductive capacity in different climates or due to the fact that they have already established populations in areas where they were introduced, with negative effects on local ecosystems or causing economical losses. For this reason, it is recommended that risk assessments should be performed in other EU bioregions as well as monitoring programs to control the spread of insect species with invasive potential. In addition, other available native insect species with potential to be used as feed ingredients should be consideredThanks are due to FCT/MCTES for the financial support to CESAM (UIDP/50017/2020+UIDB/50017/2020+LA/P/0094/2020), through national funds and to the project SUShI (CENTRO-01-0145-FEDER-030818) co-funded by Centro 2020 program, Portugal 2020, through the European Regional Development Fund, through FCT/MCTES, and to PORBIOTA—Portuguese E-Infrastructure for Information and Research on Biodiversity (POCI-01-0145-FEDER-022127), financed by FCT through PIDAC national funds and co-funded by the FEDER. Thanks also due to the project IN607B 2020/04 funded by Xunta de Galicia, Galician Agency for Innovation, GAIN. F.S.L. is supported by a PhD grant (PD/BD/150577/2020) funded by FCT/MCTES. O.M.C.C.A. is funded by national funds (OE), through FCT, in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of 29 August, changed by Law 57/2017, of 19 JulyPeer reviewe

Improving the Lipid Profile of Black Soldier Fly (Hermetia illucens) Larvae for Marine Aquafeeds: Current State of Knowledge

14 pages, 5 figures, 1 table.-- This is an open access article distributed under the Creative Commons Attribution LicenseThe replacement of fish meal and fish oil by insect-based ingredients in the formulation of marine aquafeeds can be an important step towards sustainability. To pursue this goal, the modulation of the lipid profile of black soldier fly larvae (Hermetia illucens) has received great attention. While its nutritional profile can shift with diet, the ability to modulate its lipidome is yet to be understood. The present work provides an overview of the lipid modulation of H. illucens larvae through its diet, aiming to produce a more suitable ingredient for marine aquafeeds. Marine-based substrates significantly improve the lipid profile of H. illucens larvae, namely its omega-3 fatty acids profile. An improvement of approximately 40% can be achieved using fish discards. Substantial levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), two essential fatty acids for marine fish and shrimp species, were recorded in H. illucens larvae fed on fish discards and coffee silverskin with Schyzochytrium sp. Unfortunately, these improvements are still deeply connected to marine-based bioresources, some still being too costly for use at an industrial scale (e.g., microalgae). New approaches using solutions from the biotechnology toolbox will be decisive to make H. illucens larvae a feasible alternative ingredient for marine aquafeeds without having to rely on marine bioresourcesThanks are due to FCT/MCTES for the financial support to CESAM (UIDP/50017/2020+UIDB/50017/2020+LA/P/0094/2020), through national funds and to the project SUShI (CENTRO-01-0145-FEDER-030818) co-funded by Centro 2020 program, Portugal 2020, through the European Regional Development Fund, through FCT/MCTESand Xunta de Galicia (Grupos de Potencial Crecimiento, IN607B 2018/19). D.P.R. is funded by a PhD grant attributed by FCT/MCTES (PD/BD/143093/2018). O.M.C.C.A. is funded by national funds (OE), through FCT, in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree-Law 57/2016, of 29 August, changed by Law 57/2017, of 19 JulyPeer reviewe

Average (±SE) numbers of aphids recorded in the different sub-treatments started with different initial numbers of aphids (40, 120, 240 and 400).

<p>Arrows indicate: a - first count, b - appearance of first larvae and mummies and c - final count.</p

Average (±SE) number of aphids recorded at the first count (A), at the instant when the first mummies and larvae appeared (B) and in the last count (C).

<p>For each of the initial number of aphids used (40, 120, 240, 400 - indicated on the horizontal axis), different letters represent differences between the means recorded in the different sub-treatments.</p

Average (±SE) maximum number of aphids recorded in each treatment.

<p>For each of the initial numbers of aphids used (40, 120, 240, 400 - indicated on the horizontal axis) different letters at the tops of the columns indicate significant differences between the means recorded in the different sub-treatments.</p

Initial numbers of aphids, parasitoids (<i>Aphidius colemani</i>) and predators (<i>Adalia bipunctata</i>) used in the experiment.

<p>There were 3 replicates for each treatment (initial aphid density) in each sub-treatment (“Predators”, “Predators+Parasitoids” and “Parasitoids”).</p

Repeated-measures two-way ANOVA of the recorded aphid numbers with treatment (initial aphid densities) and sub-treatment (“Predators”, “Predators+Parasitoids” and “Parasitoids”) counted as main effects.

*<p>Fraction values of degrees of freedom were corrected for sphericity using the Greenhouse-Geisser correction.</p