Risk‐taking behaviour may explain high predation mortality of GH‐transgenic common carp Cyprinus carpio

The competitive ability and habitat selection of juvenile all‐fish GH‐transgenic common carp Cyprinus carpio and their size‐matched non‐transgenic conspecifics, in the absence and presence of predation risk, under different food distributions, were compared. Unequal‐competitor ideal‐free‐distribution analysis showed that a larger proportion of transgenic C. carpio fed within the system, although they were not overrepresented at a higher‐quantity food source. Moreover, the analysis showed that transgenic C. carpio maintained a faster growth rate, and were more willing to risk exposure to a predator when foraging, thereby supporting the hypothesis that predation selects against maximal growth rates by removing individuals that display increased foraging effort. Without compensatory behaviours that could mitigate the effects of predation risk, the escaped or released transgenic C. carpio with high‐gain and high‐risk performance would grow well but probably suffer high predation mortality in nature.     

Comparative trophic impacts of two globally invasive cyprinid fishes reveal species‐specific invasion consequences for a threatened native fish

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Effects of predation risk and plant resistance on Manduca sexta caterpillar feeding behaviour and physiology

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Intraspecific variation in diet, growth, and morphology of landlocked Galaxias maculatus during its larval period: the role of food availability and predation risk

Food availability and predation risk have been shown to affect phenotypes during early life history of fishes. Galaxias maculatus, a small fish widely distributed around the southern hemisphere, clearly exhibits a complex trade-off between feeding and predation avoidance during growth over the larval period. We studied the effect of different environmental variables on diet, growth, mortality, and morphology through field surveys and data revision in the literature for limnetic G. maculatus larvae in five oligotrophic lakes of Patagonia. Both number of food categories and prey ingested by larvae were directly related to zooplankton density. Larval growth rate was related with zooplankton density and temperature. Lakes with high zooplankton densities and low predation risk had larvae with deeper bodies and shorter caudal peduncles, while in lakes with less food and high predation risk larvae were slender with shallower bodies and longer peduncles. Food availability and predation risk seem to operate on the swimming performance of G. maculatus larvae through the slenderness of the body and the length of the caudal peduncle. The observed phenotypic variation in growth and morphology could be a key feature that has allowed this species to successfully colonize a wide variety of environments in the southern hemisphere.     

The Effect of Simulated African Wild Dog Presence on Anti‐predator Behaviour of Kudu and Impala

In this study, we examined the behavioural, temporal and spatial effects of simulated African wild dog (Lycaon pictus) presence on its two main prey species: kudu (Tragelaphus strepsiceros) and impala (Aepyceros melampus). We spread African wild dog faeces around waterholes and played African wild dog sounds at different intervals to mimic immediate and non‐immediate predation pressure. We looked at anti‐predator behaviour at both a herd and individual level and distinguished between high‐quality (detracts from all other activities), high‐cost vigilance and low‐quality (used to monitor the surrounding in spare time), low‐cost vigilance to determine costs involved. We found that simulated African wild dog presence had little effect on anti‐predator behaviour of their free‐ranging prey. Only when immediate predation risk was mimicked did kudu invest in (additional) high‐quality vigilance, whereas impala showed no response. Regardless of direct cues of African wild dog presence, behavioural adjustments to reduce predation risk were primarily based on environmental factors such as time of the day and broad‐scale habitat structure. Predators have been shown to utilize waterholes to hunt, and prey species are therefore likely to maximize anti‐predator behaviour in this high‐risk environment based on environmental variables affecting predation risk, the main predator within the system, and water requirements, leaving little flexibility to respond to (simulated) African wild dog presence.     

Relevance of Bt toxin interaction studies for environmental risk assessment of genetically modified crops

In recent years, different Bacillus thuringiensis (Bt) toxin‐encoding genes have been combined or ‘stacked’ in genetically modified (GM) crops. Synergism between Bt proteins may occur and thereby increase the impact of the stacked GM event on nontarget invertebrates compared to plants expressing a single Bt gene. On the basis of bioassay data available for Bt toxins alone or in combination, we argue that the current knowledge of Bt protein interactions is of limited relevance in environmental risk assessment (ERA).     

Assessment of transgene flow in tomato and potential effects of genetically modified tomato expressing Cry3Bb1 toxins on bumblebee feeding behaviour

One of the concerns surrounding the commercial release of genetically modified (GM) crops is the escape of transgenes into agricultural or semi‐natural habitats through vertical gene flow, as this may cause environmental or economic problems. There is also the concern that GM crops may affect pollinators and the pollination services they provide. Despite the growing commercial interest of GM tomato (Solanum lycopersicum), gene flow has been assessed only sparsely in tomato. To evaluate the likelihood of gene flow from GM tomato plants to sexually compatible plants, and to assess whether bumblebee activity is affected by GM tomato, three experiments were conducted under greenhouse conditions, using a Bt‐tomato expressing the insecticidal Cry3Bb1 protein as model system: (a) artificial crosses between a GM tomato line, two wild tomato relatives (Solanum hirsutum and Solanum nigrum) and a non‐GM tomato variety; (b) bumblebee‐mediated crosses between GM and non‐GM tomato plants and (c) visual observations of bumblebees' feeding behaviour. No hybrids were obtained between the GM tomato line and S. hirsutum and S. nigrum. In an experimental design where non‐GM receptor plants outnumbered GM plants by approximately 3:1, the bumblebee‐mediated cross‐fertilisation rate between GM and non‐GM tomato plants was measured at 4.3 ± 5.47%. No significant differences in feeding behaviour of bumblebees foraging on GM and non‐GM tomato plants were observed. Therefore, we conclude that: (a) the probability of transgene introgression between the GM tomato line used in this study and its wild relatives S. hirsutum and S. nigrum is negligible; (b) bumblebee activity can mediate cross‐fertilisation between GM and non‐GM tomato and (3) the Cry3Bb1‐expressing tomato line tested does not adversely affect the feeding behaviour of bumblebees.     

Compensatory growth following transient intraguild predation risk in predatory mites

Compensatory or catch‐up growth following growth impairment caused by transient environmental stress, due to adverse abiotic factors or food, is widespread in animals. Such growth strategies commonly balance retarded development and reduced growth. They depend on the type of stressor but are unknown for predation risk, a prime selective force shaping life history. Anti‐predator behaviours by immature prey typically come at the cost of reduced growth rates with potential negative consequences on age and size at maturity. Here, we investigated the hypothesis that transient intraguild predation (IGP) risk induces compensatory or catch‐up growth in the plant‐inhabiting predatory mite Phytoseiulus persimilis. Immature P. persimilis were exposed in the larval stage to no, low or high IGP risk, and kept under benign conditions in the next developmental stage, the protonymph. High but not low IGP risk prolonged development of P. persimilis larvae, which was compensated in the protonymphal stage by increased foraging activity and accelerated development, resulting in optimal age and size at maturity. Our study provides the first experimental evidence that prey may balance developmental costs accruing from anti‐predator behaviour by compensatory growth.     

Experimental assessment of predation risk for juvenile green sturgeon,Acipenser medirostris,by two predatory fishes

Predation is a common cause of early life stage mortality in fishes, with reduced risk as individuals grow and become too large to be consumed by gape-limited predatory fishes. Large-bodied species, such as sturgeon, may reach this size-refuge within the first year. However, there is limited understanding of what this size threshold is despite the value of this information for conservation management. We conducted laboratory-based predation experiments on juvenile green sturgeon, Acipenser medirostris, to estimate vulnerability to predation during outmigration from their natal reaches in California to the Pacific Ocean. Two highly abundant and non-native predatory fish species (largemouth bass, Micropterus salmoides, and striped bass, Morone saxatilis) were captured in the wild to be tested with developing juvenile green sturgeon from the UC Davis Green Sturgeon Broodstock Program. Experimental tanks, each containing five predators, received thirty prey for 24-hr exposures. Between sturgeon prey trials, predators were exposed to alternative prey species to confirm predators were exhibiting normal feeding behaviors. In addition to green sturgeon mortality data, trials were video recorded and predatory behaviors were quantified. Overall, these predator species displayed much lower rates of predation on juvenile green sturgeon than alternate prey. Predation decreased with green sturgeon size, and predation risk diminished to zero once sturgeon reached a length threshold of roughly 20–22 cm total length, or between 38% and 58% of predator total length. Behavioral analyses showed low motivation to feed on green sturgeon, with both predators attempting predation less frequently as sturgeon grew. Results of this study imply that optimizing growth rates for larval and juvenile sturgeon would shorten the time in which they are vulnerable to predation. Future experiments should assess predation risk of juvenile green sturgeon by additional predator species common to the Sacramento-San Joaquin watershed.     

Predation risk affects the levels of maternal immune factors in avian eggs

Predation risk is an environmental stressor that can induce changes in prey behavior and physiology. Perception of predation risk may indirectly affect offspring traits and future fitness prospects via impacts on the condition of parents. Females may influence the survival of their offspring via maternal effects, especially when breeding in stressful conditions. We investigated the effects of continuous predation risk perceived by mothers on the maternal allocation of immune factors and carotenoids in eggs of the pied flycatcher Ficedula hypoleuca. We collected eggs from wild pied flycatchers that bred in the vicinity of a predator nest (pygmy owl Glaucidium passerinum), were exposed to cues of a mammalian nest predator (urine of least weasel Mustela nivalis), or received appropriate controls for these two groups. Pied flycatchers transferred more immunoglobulin in eggs under high predation risk in both owl and mammalian predator treatments. The presence of owl nests also lowered the level of lysozyme transferred in the eggs in one of the two study years. Predation risk did not modify egg size or overall carotenoid levels. Our results show that continuous predation risk perceived by females during egg‐laying affects egg composition. This different allocation of maternal immune factors may be an adaptive response evolved to increase the probability of offspring survival.     

Increased mortality of growth‐enhanced transgenic common carp (Cyprinus carpio L.) under short‐term predation risk

There is strong evidence that genetic capacity for growth evolves toward an optimum rather than an absolute maximum. This implies that fast growth has a cost and that trade‐offs occur between growth and other life‐history traits. In this study, we conducted a series of predation trials with a paired‐contrast design to test the differences in anti‐predator ability between growth‐enhanced transgenic and non‐transgenic common carp (Cyprinus carpio L.). We showed that young transgenic fish suffered higher predation mortality than control carp in both small‐bodied and large‐bodied size‐matched trials, and thus possessed lower anti‐predator ability. Our results suggest that a trade‐off exists between growth rate and survival such that rapid growth entails a cost in terms of mortality.     

Global patterns and clines in the growth of common carp Cyprinus carpio

This review provides a meta‐analytical assessment of the global patterns and clines in the growth of Cyprinus carpio as measured by length‐at‐age (L_t) or von Bertalanffy growth function (VBGF) parameters, mass–length relationship (W–L_t) and condition factor, based on literature data. In total, 284 studies were retrieved spanning 91 years of research and carried out on 381 waterbodies–locations in 50 countries in all five continents. Although native C. carpio achieved larger (asymptotic) size relative to its non‐native counterpart, the latter grew faster during the first 7 years of life. Lentic populations (especially in natural lakes) also achieved larger sizes relative to lotic ones and the same was true for populations in cold and temperate v. arid climates. Unlike previous studies (on much more restricted datasets), only weak latitudinal clines in instantaneous growth rate, L_t at age 3 and mortality were observed globally and this was probably due to the presence of counter‐gradient growth variation at all representative age classes (i.e. 1–10 years). Slightly negative allometry was revealed by the W–L_t and the related form factor tended to distinguish the more elongated and torpedo‐shaped body typical of the wild form from the deeper body of feral‐domesticated C. carpio. Existing population dynamics models for C. carpio will benefit from the comprehensive range of waterbody type × climate class‐specific VBGF parameters provided in the present study; whereas, more studies are needed on the species' growth in tropical regions and to unravel the possibility of confounding effects on age estimation due to both historical and methodological reasons.     

Predation risk and habitat complexity modify intermediate predator feeding rates and energetic efficiencies in a tri‐trophic system

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Non‐native fishes and climate change: predicting species responses to warming temperatures in a temperate region

1. Temperate regions with fish communities dominated by cold‐water species (physiological optima <20 °C) are vulnerable to the effects of warming temperatures caused by climate change, including displacement by non‐native cool‐water (physiological optima 20–28 °C) and warm‐water fishes (physiological optima >28 °C) that are able to establish and invade as the thermal constraints on the expression of their life history traits diminish. 2. England and Wales is a temperate region into which at least 38 freshwater fishes have been introduced, although 14 of these are no longer present. Of the remaining 24 species, some have persisted but failed to establish, some have established populations without becoming invasive and some have become invasive. The aim of the study was to predict the responses of these 24 non‐native fishes to the warming temperatures of England and Wales predicted under climate change in 2050. 3. The predictive use of climate‐matching models and an air and water temperature regression model suggested that there are six non‐native fishes currently persistent but not established in England and Wales whose establishment and subsequent invasion would benefit substantially from the predicted warming temperatures. These included the common carp Cyprinus carpio and European catfish Silurus glanis, fishes that also exert a relatively high propagule pressure through stocking to support angling and whose spatial distribution is currently increasing significantly, including in open systems. 4. The potential ecological impacts of the combined effects of warming temperatures, current spatial distribution and propagule pressure on the establishment and invasion of C. carpio and S. glanis were assessed. The ecological consequences of C. carpio invasion were assessed as potentially severe in England and Wales, with impacts likely to relate to habitat destruction, macrophyte loss and increased water turbidity. However, evidence of ecological impacts of S. glanis elsewhere in their introduced range was less clear and so their potential impacts in England and Wales remain uncertain.     

Normal expression of insect-resistant transgene in progeny of common wild rice crossed with genetically modified rice: its implication in ecological biosafety assessment

Transgene outflow from genetically modified (GM) rice to its wild relatives may cause undesirable ecological consequences. Understanding the level of transgene expression in wild rice following gene flow is important for assessing such consequences, providing that transgene escape from GM rice cannot be prevented. To determine the expression of a transgene in common wild rice (Oryza rufipogon), we analyzed the content of Cry1Ac protein in three GM rice lines containing a Bt transgene, their F₁ hybrids with common wild rice and F₂ progeny at different growth stages, using the sandwich enzyme-linked immunosorbent assay. The average content of Cry1Ac protein in leaf samples of the wild rice lines ranged between 0.016 and 0.069% during the entire growth period, whereas that in stems varied between 0.12 and 0.39%. A great variation in Cry1Ac protein content was detected among individuals of F₁ hybrids and F₂ progeny, with some wild individuals showing higher level of Bt toxin than the cultivated GM rice. The results suggest that the Bt transgene can express normally in the interspecific hybrids between insect-resistant GM rice and common wild rice, and may have similar effects on the target insects as in GM rice.     

Physiological advantages may contribute to successful invasion of the exotic Cyprinus carpio into the Xingyun Lake, China

Feeding and growth traits of Cyprinus carpio and Cyprinus pellegrini (both at age-0) were compared in three experiment, in an attempt to analyze potential causes for the displacement of the native C. pellegrini in the Xingyun Lake, Yuxi, Yunan, China. Experiment I was conducted in water which fluctuated between 15 and 20°C. Experiment II and III were conducted in a laboratory and water temperature was maintained between 20°C and 25°C, respectively. Three common trends were noted for all three experiments: (1) feeding rate of C. carpio was lower than that of C. pellegrini, and this difference was found to be significant in experiment I; (2) growth rate of C. carpio was higher than C. pellegrini, and the difference was found to be significant in experiment II; (3) food conversion efficiency and energy retention efficiency for C. carpio were higher than those of C. pellegrini, and significant differences were noted in experiment I and II. Since the growth period for fish in the Xingyun Lake generally occurs when water temperatures are between 15 and 25°C, it can be suggested that C. carpio has advantages over C. pellegrini in growth and food utilization efficiency, and lower food consumption than C. pellegrini. These physiological traits of C. carpio might allow this species to be more resistant to food shortage and predation, and may be partially responsible for the displacement of C. pellegrini by C. carpio.     

Fish predation on Notonecta (Hemiptera): relationship between prey risk and habitat utilization

Summary Prey risk was examined in the laboratory to compare the ability of 6 Notonecta species to coexist with insectivorous fishes (Lepomis cyanellus, L. gibbosus). Because of their smaller size, lighter color, greater tendency to remain motionless in the presence of the predator, greater ability to avoid capture when attacked, and predicted lower profitability as prey, N. lunata and N. petrunkevitchi were estimated to have the lowest prey risk and greatest chance of coexisting with insectivorous fishes in nature. The 2 largest notonectids, N. irrorata and N. insulata, both highly melanistic and rapidly discovered by foraging sunfishes, were judged to be the most susceptible to predation by large fishes. The presence of vegetation as a potential refuge tended to decrease prey risk but did not significantly alter the relative risk among the prey species. Finally, the relative prey risk measured in the laboratory was consistent with the general distribution of these species in relation to fishes in local habitats. We suggest that fish predation is an important determinant of Notonecta habitat utilization patterns.     

Larvae of cryptic species of Anopheles gambiae respond differently to cues of predation risk

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Upper thermal tolerance of wild‐type,domesticated and growth hormone‐transgenic coho salmon Oncorhynchus kisutch

In coho salmon Oncorhynchus kisutch, no significant differences in critical thermal maximum (c. 26·9° C, C_Tmax) were observed among size‐matched wild‐type, domesticated, growth hormone (GH)‐transgenic fish fed to satiation, and GH‐transgenic fish on a ration‐restricted diet. Instead, GH‐transgenic fish fed to satiation had significantly higher maximum heart rate and Arrhenius breakpoint temperature (mean ± s.e. = 17·3 ± 0·1° C, T_AB). These results provide insight into effects of modified growth rate on temperature tolerance in salmonids, and can be used to assess the potential ecological consequences of GH‐transgenic fishes should they enter natural environments with temperatures near their thermal tolerance limits.