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Diaspis echinocacti (Bouché) poses a significant threat to Opuntia spp. worldwide, highlighting the critical need for effective control measures. This study examines predation potential across various life stages of D. echinocacti at temperatures ranging from 15 to 35 °C, functional responses using Holling and Rogers models, and mutual interference among coleopteran species (Chilocorus bipustulatus, Exochomus nigripennis, Scymnus interruptus, and Cybocephalus nipponicus) in the management of D. echinocacti. The results consistently showed a preference for 1st instar nymphs across all tested species and temperatures, with peak consumption values observed for E. nigripennis at 26 °C for 1st instar nymphs (46.4), 2nd instar nymphs (41.3), and adult females (35.4). Functional response analysis indicated a Type-II response for all species, with E. nigripennis demonstrating efficiency with a lower attack rate (0.4 h–1), and handling time (0.6 h) and higher max attack rate (131.2) in both models. AIC values indicate a better fit for Holling's model for C. nipponicus (253.2478) and C. bipustulatus (269.3266). Scymnus interruptus (284.4563) and E. nigripennis (340.6273) showed similar AIC values for both models, suggesting model flexibility for these ladybeetles. Mutual interference studies showed a consistent decrease in prey consumption and discovery area as predator density increased. The estimated mutual interference constants (m) for C. nipponicus, S. interruptus, C. bipustulatus, and E. nigripennis were 1.60, 1.60, 1.61, and 1.63, respectively. The findings highlight the role of E. nigripennis and C. bipustulatus in mitigating the impact of D. echinocacti on Opuntia spp., providing valuable insights for effective pest management strategies. [ABSTRACT FROM AUTHOR]

Predatory bacteria, which prey on other bacteria, have significant functions in microbial ecosystems and have attracted increasing attention for their biotechnological use. However, knowledge of the characteristics of wild-type environmental predatory bacteria remains limited. This study isolated two predatory bacteria, Bacteriovorax stolpii HI3 and Myxococcus sp. MH1, from a freshwater pond and characterized their predation capabilities. Determination of the prey range using 53 potential prey strains, including 52 environmental strains, revealed that B. stolpii HI3 and Myxococcus sp. MH1 could prey on a wide spectrum of Gram-negative bacteria and a broader range of bacteria, irrespective of phylogeny, in accordance with the common characteristics of Bdellovibrio and like organisms and myxobacteria, respectively. Liquid culture assays also found that although predation by B. stolpii HI3 rapidly and largely occurred, the prey bacteria regrew, possibly through plastic phenotypic resistance to predation. In contrast, predation by Myxococcus sp. MH1 occurred at relatively low efficiency but was longer lasting. The two strains exhibited slightly distinct temperature preferences but commonly preferred slightly alkaline pH. The novel findings of this study provide evidence for the coexistence of predatory bacteria with diverse predation capabilities in the natural aquatic environment. [ABSTRACT FROM AUTHOR]

Predatory bacteria, which prey on other bacteria, have significant functions in microbial ecosystems and have attracted increasing attention for their biotechnological use. However, knowledge of the characteristics of wild-type environmental predatory bacteria remains limited. This study isolated two predatory bacteria, Bacteriovorax stolpii HI3 and Myxococcus sp. MH1, from a freshwater pond and characterized their predation capabilities. Determination of the prey range using 53 potential prey strains, including 52 environmental strains, revealed that B. stolpii HI3 and Myxococcus sp. MH1 could prey on a wide spectrum of Gram-negative bacteria and a broader range of bacteria, irrespective of phylogeny, in accordance with the common characteristics of Bdellovibrio and like organisms and myxobacteria, respectively. Liquid culture assays also found that although predation by B. stolpii HI3 rapidly and largely occurred, the prey bacteria regrew, possibly through plastic phenotypic resistance to predation. In contrast, predation by Myxococcus sp. MH1 occurred at relatively low efficiency but was longer lasting. The two strains exhibited slightly distinct temperature preferences but commonly preferred slightly alkaline pH. The novel findings of this study provide evidence for the coexistence of predatory bacteria with diverse predation capabilities in the natural aquatic environment.

Bdellovibrio and like organisms (BALOs) are obligate predatory bacteria commonly encountered in the environment. In dual predator–prey cultures, prey accessibility ensures optimal feeding and replication and rapid BALO population growth. However, the environmental prey landscape is complex, as it also incorporates non-prey cells and other particles. These may act as decoys, generating unproductive encounters which in turn may affect both predator and prey population dynamics. In this study, we hypothesized that increasing decoy:prey ratios would bring about increasing costs on the predator's reproductive fitness. We also tested the hypothesis that different BALOs and decoys would have different effects. To this end, we constructed prey landscapes including periplasmic or epibiotic predators including two types of decoy under a large range of initial decoy:prey ratio, and mixed cultures containing multiple predators and prey. We show that as decoy:prey ratios increase, the maximal predator population sizes is reduced and the time to reach it significantly increases. We found that BALOs spent less time handling non-prey (including superinfection-immune invaded prey) than prey cells, and did not differentiate between efficient and less efficient prey. This may explain why in multiple predator and prey cultures, less preferred prey appear to act as decoy. [ABSTRACT FROM AUTHOR]

Accessing information efficiently is vital for animals to make the optimal decisions, and it is particularly important when they are facing predators. Yet until now, very few quantitative conclusions have been drawn about the information dynamics in the interaction between animals due to the lack of appropriate theoretic measures. Here, we employ transfer entropy (TE), a new information-theoretic and model-free measure, to explore the information dynamics in the interaction between a predator and a prey fish. We conduct experiments in which a predator and a prey fish are confined in separate parts of an arena, but can communicate with each other visually and tactilely. TE is calculated on the pair’s coarse-grained state of the trajectories. We find that the prey’s TE is generally significantly bigger than the predator’s during trials, which indicates that the dominant information is transmitted from predator to prey. We then demonstrate that the direction of information flow is irrelevant to the parameters used in the coarse-grained procedures. We further calculate the prey’s TE at different distances between it and the predator. The resulted figure shows that there is a high plateau in the mid-range of the distance and that drops quickly at both the near and the far ends. This result reflects that there is a sensitive space zone where the prey is highly vigilant of the predator’s position.

Extensive livestock ranching is one of the main drivers of habitat degradation in terrestrial communities in the dry Chaco forest (Argentina). Grazing intensity could differentially affect native mammals and their interactions, which could impact both, native mammal communities and livestock production systems. Here, we determined how the activity index of grey foxes Lycalopex gymnocercus and capture abundance and richness of small mammals vary along a grazing intensity gradient in a particular region of the dry Chaco forest (Copo National Park, Argentina). Track plots were used to estimate the activity index of foxes and cattle, and Sherman traps for small mammals. Fresh scats were collected to analyse the diet of foxes and to assess possible changes in predator-prey dynamics. Fruit availability and shrub density were measured in 6 plots of 2 m × 50 m. We used generalized linear mixed models, Spearman's nonparametric rank correlation, Chi-squared test, and Spearman's partial correlation coefficient to analyse the potential effects of grazing intensity. We found that the activity index of foxes increased (0.06 ± 0.018) while small mammal abundance (-0.08 ± 0.024) and species richness decreased (r s = -0.94) with increasing grazing intensity. However, the proportion of scats with mammalian remains decreased with increasing grazing intensity. Also, we did not find a strong partial correlation between foxes and small mammals when we controlled for grazing intensity. This suggests that the abundance and diversity of small mammals in the study area are determined more by grazing intensity than by predator-prey interactions. Grazing intensity could negatively affect small mammals, but not through changes in fruit availability or shrub density, but possibly by affecting grass cover. Consequently, foxes' activity could increase to meet caloric intake requirements. Our results suggest that specific cattle management recommendations depend on the wildlife species that serves as a conservation target. We recommend testing whether reducing cattle load can make this productive activity compatible with wildlife conservation in dry Chaco forests. [ABSTRACT FROM AUTHOR]

To evaluate the potential of Podisus maculiventris (Say) (Heteroptera: Pentatomidae) as a biological control agent against viburnum leaf beetle, Pyrrhalta viburni (Paykull) (Coleoptera: Chrysomelidae), laboratory trials were conducted to measure prey consumption of P. maculiventris over nymphal development. Field trials tested the impact of augmentative releases of P. moculiventris nymphs on populations of P. viburni, using both open shrubs and caged branches of Viburnum trilobum. In the laboratory, P. maculiventris nymphs successfully developed while preying on P. viburni larvae and adults. Each nymph consumed an average of 100.6 larvae or 16.9 adults. Immature development duration was comparable between nymphs feeding on P. viburni adults and those given Galleria mellonella (L.) (Lepidoptera: Pyralidae) larvae as prey. In field trials, inundative releases of 30 P. maculiventris nymphs on naturally infested V. trilobum shrubs significantly reduced pest defoliation on shrubs infested with <3,000 larvae but had no effect on shrubs with heavier infestations. On caged branches, individual nymphs successfully developed when feeding only on P. viburni larvae. These results show that P. viburni larvae and adults are suitable prey for P. maculiventris and this predator could potentially be developed as a biological control agent against P. viburni. [ABSTRACT FROM AUTHOR]