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12. Seasonal activity-profiles of enzymes involved in cryoprotectant biosynthesis in Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)
- Creator:
- Tollarová, Michaela
- Type:
- article, model:article, and TEXT
- Subject:
- Diapause, overwintering, metabolism, enzymes, polyols, Heteroptera, and Pyrrhocoris apterus
- Language:
- English
- Description:
- The activities of three enzymes involved in polyol biosynthesis (aldose reductase, AR; ketose reductase, KR; and polyol dehydrogenase, PDH) were studied in adult females of the linden bug, Pyrrhocoris apterus, collected from the field during 2005/2006. While the activities of three enzymes were low in reproductive females, activities greater by one or two orders were seen in reproductively arrested females. AR and KR showed similar seasonal trends in activity. Activities were low during diapause initation and later increased and stabilized during autumnal diapause development. Further increases of AR and KR activities were seen during low temperature quiescence and finally the activities sharply decreased during vernal resumption of direct development. The activity of PDH was relatively high (but fluctuating) during diapause, then decreased in quiescent insects and almost disapeared in reproductively active females. Insects collected in February were subjected to laboratory de-acclimation (exposure to high temperatures) followed by re-acclimation (exposure to low temperatures) which resulted in loss of activity in all three enzymes and no regain. High activities of AR, KR and PDH in reproductively arrested females thus conform well with their previously observed high capacity to synthesize and accumulate polyol cryoprotectants.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
13. Seasonal adaptations of green lacewings (Neuroptera: Chrysopidae)
- Creator:
- Canard, Michel
- Type:
- article, model:article, and TEXT
- Subject:
- Chrysopidae, green lacewing, seasonal adaptation, diapause, voltinism, overwintering, cycle synchronization, and wintering chambers
- Language:
- English
- Description:
- Seasonal adaptations of green lacewings (Neuroptera: Chrysopidae) and their role in the control of aphid populations are discussed. The chrysopids of temperate zones face seasonal changes and must escape cyclic adversity. One way is via the number of broods per year. Most green lacewings are facultatively multivoltine, with the succession of generations most often regulated by photomediated diapause. Others are univoltine and some extend their life-cycle to two years in cold or dry environments. Synchronization is an important feature of seasonality, often starting in spring. In univoltine species, it is sometimes the result of subtle mechanisms, such as double contradictory signals (short plus long day lengths) for reactivation in spring, or a multi-receptivity of the preimaginal instars to photoperiod throughout a year, combined with photo-controlled and synchronized egg laying in late summer. Only one North American species is known to enter a surnumerary food-mediated diapause in summer. Every postembryonic instar may undergo diapause depending on the species. The timing and impact of the spring resumption in aphid consumption depends on their overwintering strategy. As far is known, chrysopids are intolerant of freezing, but their supercooling points are low enough to enable them to endure hard frost. The numbers of overwintering specimens of green lacewings in the field depend on the structure of the assemblages in the previous growing season. Three examples are used to show that the overwintering populations are different in the different biotopes and dependent on the way the dominant species overwinter. Artificial chambers proposed for overwintering adults of common green lacewings afford them protection during diapause and enhance their predatory efficiency in spring.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
14. Sexual dimorphism in winter survival rate differs little between damselbug species (Heteroptera: Nabidae)
- Creator:
- Roth, Steffen and Reinhardt, Klaus
- Type:
- article, model:article, and TEXT
- Subject:
- Winter survival, overwintering, low temperature experiment, sexual dimorphism, Nabidae, Heteroptera, Nabis rugosus, and N. ericetorum. N. pseudoferus
- Language:
- English
- Description:
- The winter survival of three closely related univoltine heteropterans that overwinter as adults, Nabis rugosus, N. ericetorum and N. pseudoferus was investigated. After 150 days of low temperature treatment (3-5°C, 16L : 8D, r.h. 70-80%) more males than females died. The mortality rate ranged from 88.8 to 93.8% in males and from 54.2 to 60.7% in females. However, these sexual differences in mortality did not differ significantly across the three species and populations of different geographic origin. It remains a general question whether this considerable evolutionary stability in the sex-specific investment into reproduction and survival phylogenetically conserved or frequently evolves anew to similar levels in separated populations and species. In Nabis rugosus, the relative loss of body mass during overwintering was up to 37.8%. This reflects dramatic somatic costs of adult overwintering and indirectly supports the hypothesis that food supply during overwintering is important for some heteropteran predators. However, body mass before overwintering did not significantly explain the survival pattern in N. rugosus in either sex. The similar sex-specific survival rate of overwintering adult nabids regardless of species and geographic origin can be useful for studies on population dynamics of nabids in agroecosystems and biocontrol.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
15. Size-related mortality during overwintering in cavity-nesting ant colonies (Hymenoptera: Formicidae)
- Creator:
- Mitrus, Sławomir
- Format:
- print, počítač, and online zdroj
- Type:
- article, články, journal articles, model:article, and TEXT
- Subject:
- Zoologie, Hymenoptera, Formicidae, Temnothorax crassispinus, survival rate, snow cover, social insects, overwintering, 2, and 59
- Language:
- English
- Description:
- The ongoing process of climate change will result in higher temperatures during winter and therefore might increase the survival of overwintering invertebrates. However, the process may also lead to a reduction in snow cover and expose overwintering invertebrates to lower temperatures, which could result in higher mortality. During a field experiment, I investigated the effects of a reduction in snow cover on the survival of the ant Temnothorax crassispinus, which overwinters in nests located on the ground. Ant colonies differed in the survival rate of the workers in the experimental (from which snow cover was removed) and control group. In the control group, the survival rate was unrelated to colony size. However, in the experimental group, from which snow was removed after each heavy snowfall, worker survival was lower in small colonies. Such colony size related mortality may affect the fusion of colonies before winter. and Sławomir Mitrus.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
16. The aphidophagous predator Harmonia axyridis (Coleoptera: Coccinellidae) in Greece, 1994-1999
- Creator:
- Kontodimas, Dimitrios, Stathas, George J., and Martinou, Aggeliki
- Type:
- article, model:article, and TEXT
- Subject:
- Harmonia axyridis, invasive ladybirds, native ladybirds, biocontrol agents, Greece, overwintering, Aphis fabae, Toxoptera aurantii, Aphis gossypii, and Aphis spiraecola
- Language:
- English
- Description:
- During the years 1994-1999, several hundreds of thousands of H. axyridis adults were released at various cultivations infested by aphids (citrus, vegetable and bean crops, maize etc.) and on ornamental plants in urban settings in central and southern Greece (mainly Attica and Peloponessos region) as well as on several islands. Between 1995-1999, spring sampling was conducted in some areas, just prior to releases, in order to determine if H. axyridis overwintered in the field. No presence of H. axyridis was recorded in any of the orchards where the predator had been released save in spring of 1998 and 1999 when small colonies (<50 individuals) of overwintered H. axyridis adults were observed in the Attica region. The above results suggest an inability of released H. axyridis populations to establish in Greece, although in some areas this species became an important biocontrol agent during the growing season.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
17. The effects of flooding on survivorship in overwintering larvae of the large copper butterfly Lycaena dispar batavus (Lepidoptera: Lycaenidae), and its possible implications for restoration management
- Creator:
- Nicholls, Colin N. and Pullin, Andrew S.
- Type:
- article, model:article, and TEXT
- Subject:
- Butterfly, Lycaena dispar batavus, larvae, overwintering, flooding, submergence, restoration, and Broadland
- Language:
- English
- Description:
- Previous work suggests that submergence of Lycaena dispar larvae during overwintering may play a significant role in this butterfly's population dynamics. Since potential re-introduction sites in eastern England are prone to regular seasonal flooding, we further studied the species' submergence tolerance with a view to formulating management protocols conducive to larval survivorship under periodic flood conditions. Simulated flooding regimes using captive-reared larvae showed that enforced submergence has a twofold effect: firstly, a direct increase in mortality after 28 days under water and, secondly, a longer term, post-diapause increase in mortality; manifest either as an inability of larvae to resume feeding, or a failure to complete development. Additionally, there was a marked difference in the response of "early" and "late" diapause larvae; the latter generally succumbing after shorter periods under water, and suffering higher total mortalities. Behavioural investigations suggest that, if afforded the opportunity, diapausing larvae can evade submergence by climbing onto the exposed sections of partially flooded host plants. Significantly, survival on partially flooded plants was found to be comparable to that on unflooded controls. Further re-introductions of L. dispar in the U.K. will probably necessitate a direct translocation of wild Dutch stock. As the flood tolerance of this source population remains largely undetermined, and given that re-introduction site hydrology will be generally unamenable to conservation-oriented manipulation, it is recommended that restoration management be directed towards creating structural diversity in the vegetation of overwintering habitats, thereby providing potential "flood refugia" for hibernating larvae.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
18. Winter climates and coldhardiness in terrestrial insects
- Creator:
- Turnock, William J. and Fields , Paul G.
- Type:
- article, model:article, and TEXT
- Subject:
- Winter climates, snow-cover, overwintering, terrestrial insects, winter climatic zones, freeze-tolerance, freeze-susceptibility, non-freezing mortality, supercooling point, and coldhardiness
- Language:
- English
- Description:
- Overwintering insects must avoid injury and death from the freezing of tissues and from metabolic disruptions associated with exposure to low, non-freezing temperatures. The winter climates of the world are classified in relation to insect overwintering on the basis of their minimum temperatures and the duration of the winter (when temperatures are below the thermal range for activity and development). Outside the Tropical Wet zone, the severity of exposure to cold (temperature, snowfall, duration of exposure, predictability, variability) can vary from a few days at 0°C to months below -20°C with extremes as low as -60°C. The severity of the temperature exposure may be ameliorated by the selection by insects of overwintering sites (exposed, partly-exposed, protected). The relationships among overwintering habitats, the minimum winter temperature in climatic zones, and the supercooling points (SCP) of over 350 terrestrial insects from published reports were examined. Variability in the SCP among insects within each climatic zone and habitat was wide. Among the freeze-susceptible species that overwintered in exposed or partly-protected habitats the SCP and the cold severity of climate were correlated. This was not the case for insects that overwintered in protected habitats. The SCP's of freeze-tolerant insects were generally higher than the freeze-susceptible insects, and the SCP's were not tightly linked with the cold severity of climatic zone. Insects, both freeze-susceptible and freeze-tolerant, overwintering in exposed habitats had lower SCP's than insects from habitats that offered some protection from ambient temperatures. Thirty-eight species had reports of SCP's for different geographical locations. Although there were occasionally differences in the SCP's, there was no consistent pattern of insects having lower SCP's when overwintering in colder habitats. The incidence of freeze-tolerance was higher in boreal and polar climatic zones than in climatic zones with warmer winters. Holometabola insects had a higher incidence of freeze-tolerance than hemimetabola insects. Suggestions for future research directions are outlined.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public