Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a generalist predatory mirid widely used in augmentative biological control of various insect pests in greenhouse tomato production in Europe, including the invasive tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera, Gelechiidae). However, its biocontrol efficacy often relies on the presence of alternative prey. The present study aimed at evaluating the effect of various prey foods (Ephestia kuehniella eggs, Bemisia tabaci nymphs, Tuta absoluta eggs and Macrosiphum euphorbiae nymphs) on some life history traits of M. pygmaeus. Both nymphal development and adult fertility of M. pygmaeus were significantly affected by prey food type, but not survival. Duration of nymphal stage was higher when M. pygmaeus fed on T. absoluta eggs compared to the other prey. Mean fertility of M. pygmaeus females was greatest when fed with B. tabaci nymphs, and was greater when offered M. euphorbiae aphids and E. kuehniella eggs than when offered T. absoluta eggs. Given the low quality of T. absoluta eggs, the efficacy of M. pygmaeus to control T. absoluta may be limited in the absence of other food sources. Experiments for assessing effectiveness of generalist predators should involve the possible impact of prey preference as well as a possible prey switching.
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Development time and juvenile survival of M. pygmaeus were assessed according to different food sources: (a) T. absoluta eggs, (b) B. tabaci nymphs, (c) M. Euphorbiae nymphs and (d) E. kuehniella eggs. Newly emerged M. pygmaeus nymphs (at stage N1) were individually transferred into 10-ml tubes with one tomato leaflet. Every two days, tubes were checked for nymphal stage. Food was supplied every two days and the quantity offered depended on the nymphal stage of the predator. Food quantity offered to each nymphal stage was estimated following a preliminary experiment in the laboratory. M. pygmaeus nymphal stages N1, N2, N3, N4, and N5, were respectively offered 10, 18, 24, 32, 36 T. absoluta eggs, 8, 12, 16, 24, 24, 28 E. kuehniella eggs, 20, 24, 24, 40, 40 B. tabaci nymphs, and 20, 20, 30, 30, 30 M. euphorbiae nymphs. The tomato leaflet was changed when necessary. Nymphal development and survival were checked daily until either death or adulthood. Nymphs that died on the first day of the experiment were replaced by new ones, as it was assumed that this was not due to prey food. Each test was replicated 30 times.
A significant effect of prey food on the development time (N1 to N5) of M. pygmaeus was observed (F3, 103 = 16.6, P
The present study showed a longer duration of nymphal development and lower fertility of M. pygmaeus when fed with T. absoluta eggs, compared to other prey foods such as E. kuehniella eggs, B. tabaci nymphs and M. euphorbiae nymphs. Our results support a previous study showing that fertility was lower when M. pygmaeus were fed with T. absoluta eggs compared to E. kuehniella eggs [20]. However, authors did not show significant differences between prey foods regarding development time. T. absoluta eggs are probably of low nutritional quality for the generalist predator M. pygmaeus, and its role as a biocontrol agent is probably limited in the absence of other food sources. Other studies showed that M. pygmaeus can exhibit prey switching when foraging in patches with disproportionate densities of T. absoluta and B. tabaci [30]. This particular behavior might result in effective regulation of both prey populations [24,25]. The same phenomenon has been observed for the generalist predator, Orius insidiosus (Hemiptera:Anthocoridae), in presence of the soybean aphid [31,32]. Thus, alternative prey could provide good control of T. absoluta by increasing density of M. pygmaeus populations [25].
(A) Relative abundance of Concholepas concholepas with shell color matching and non-matching the surrounding color recorded in three intertidal microhabitats. The microhabitats were characterized according the most abundant prey item: dark habitats dominated by the mussels Perumytilus purpuratus and Semimytilus algosus, light colored habitat dominated by barnacles of Jehlius cirratus, Notochthamalus scabrosus, Notobalanus flosculus, Balanus laevis, and mixed habitat with both prey taxa. The snails were photographed and then categorized as light, dark and mixed colored. Matching and non-matching snails were considered as those that did or did not have the same color category as the prey on which they were found. Color categorization and the determination of whether they matched the prey color or not were determined by visual inspection. (B) Relationships between the mean RGB values (1 SE) of background and shell of C. concholepas (n = 10). Symbols are filled with the corresponding r(ed), g(reen) and b(lue) analyzed color.
Changes in shell color of early settlers (mean pooled RGB scores, 1 SD, n = 12) and post-metamorphic of Concholepas concholepas (mean pooled RGB scores, 1 SD, n = 6). Early settlers were reared over time from 2 days after metamorphosis to 28 days on different colored diets. Three sets of snails were reared during the experiment with light (barnacles stands), dark (mussels beds) and mixed (both taxa) colored prey (A). Two sets of snails were reared during the first week with one type of prey and then switched (arrow) to the alternative color prey. The right box plot shows the distributional characteristics of averaged RGB values recorded in natural habitats dominated by the experimental prey (B). Postmetamorphic larvae were reared from settlers to 56 days old with different colored diets. Two sets of snails (n = 6) were reared during the entire period with light (barnacles) and dark (mussels) prey (C). Two sets of snails (n = 6) were reared for the first 28 days with one type of prey and then switched (arrow) to the alternative prey (D).
In the mid-rocky intertidal of central Chile the crab Acanthocyclus hassleri prey on barnacles, mussels and small C. concholepas (12, 13). We used this crab to test the effect of cryptic shell coloration on the survivorship of newly metamorphosed and small juveniles of C. concholepas, with average peristomal length of 1.73 mm (0.09 SD) and 16.2 mm (1.90 SD) respectively. Dark newly metamorphosed snails were collected from the rocky intertidal zone of Calfuco dominated by mussels. However, small dark juveniles were obtained in the laboratory by culturing them from newly metamorphosed fed on P. purpuratus.
We equipped 21 female SES from the Kerguelen Archipelago with loggers and recorded their movements during post-breeding foraging trips at sea. From accelerometry, we estimated the number of prey encounter events (nPEE) and used it as a reference for feeding intensity. We also extracted several track- and dive-based movement metrics and evaluated how well they explain and predict the variance in nPEE. We conducted our analysis at two temporal scales (dive and day), with two dive profile resolutions (high at 1 Hz and low with five dive segments), and two types of models (linear models and regression trees).
Foraging has a central role in the evolution of species as it directly affects the fitness of individuals via the probability of survival and reproduction [1]. A key question behavioral ecologists have been interested in is how organisms adopt a hierarchical decision-making process to improve foraging efficiency [2]. For instance, foragers can increase their energy intake rate while minimizing some costs, such as the time searching, capturing, and handling prey, or the risk of predation. In conservation, understanding the spatiotemporal variation of foraging behavior in response to resource distribution is fundamental for the protection and management of endangered species [3, 4]. And yet, direct observations of the interaction between predators and their prey in free-ranging species are often challenging or impossible for a variety of reasons such as remoteness and large home ranges. The development of bio-logging technologies in the last decades has helped address some of these challenges [5].
Movement metrics inferring feeding behavior have been developed based on the optimal foraging theory, which posits that foraging animals improve their fitness when adjusting their behavior in a way that maximizes their net rate energy intake in response to environmental constraints [17]. One aspect of the optimal foraging theory focuses on movement patterns that animals adopt while foraging [17]. Animals should adopt an area-restricted search (ARS) to maximize resource encounter rate and minimize costs of movement [18]. The ARS has two distinct search modes. First, an intensive search mode, triggered by resource encounters or environmental cues, that is characterized by slow speeds and large turning angles (i.e., tortuous movement). In the intensive search mode, foragers remain in the same area and thus increase the probability of encountering and consuming additional food items. Second, foragers switch to an extensive search mode after repeated unsuccessful resource encounters for which they increase speed and move in a relatively straight line to find another resource patch [19]. Therefore, movement metrics infer feeding intensity by quantifying search intensity along the track assuming a high correlation between feeding and search behavior [7]. 2ff7e9595c
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