EJE, vol. 93 (1996), issue 3

Proceedings of the Second European Workshop of Invertebrate Ecophysiology.


Eur. J. Entomol. 93 (3): 1996


Geographical variation of life cycle in crickets (Ensifera: Grylloidea)


Eur. J. Entomol. 93 (3): 281-302, 1996

Crickets are convenient systems for studying life-cycle evolution. They show a considerable diversity in life-cycle types, being homodynamic in some parts of the tropics and heterodynamic with various kinds of diapause and other regulatory responses in the temperate region. Crickets are relatively free from constraints by food supply, because they are omnivorous. Therefore, their geographical variation may clearly reflect climatic selection as exemplified by latitudinal dines in adult size, egg size and ovipositor length. These morphometric dines are closely related to development time, egg diapause and photoperiodic responses, indicating that crickets...

Geographical variation in thermal requirements for insect development


Eur. J. Entomol. 93 (3): 303-312, 1996

Thermal constants, Lower development threshold (LDT) and sum of effective temperatures (SET) were recalculated from literature data for 335 insect species. Included were only populations whose development rate was ascertained in at least 4 constant temperatures of <=28C. Variation of thermal constants was investigated in relation to geographic origin of the populations to test the prediction that LDT will decrease and SET increase with increasing geographical latitude (Trudgill, 1995). In tropics (at <= 23N or S), LDT was high with little geographic variation. In subtropical and temperate zones there was a significant trend for decreasing average...

Adaptations of insects at high altitudes of Chimborazo, Ecuador


Eur. J. Entomol. 93 (3): 313-318, 1996

Carabid beetles (Coleoptera: Carabidae) were collected from an altitudinal gradient at Chimboraze, Ecuador, in March 1994. Bembidion andinum Bates was the dominant species at 4,800 m, Pelmatellus andium Bates at 4,500 m and Agraphoderus integer Bates at 4,250 m. During daytime, the beetles were sheltering under rocks, but were caught in pitfall traps on open ground during the night. At 0.5 cm depth, soil temperatures from -4 to 41C were recorded at 4,800 m and from -3 to 52C at 4,500 m, but fluctuations were greatlybuffered at 2 and 5 cm depths. All three species had mean supercooling points of -5 to -6C. Rates of water loss...

An altitudinal transect as an indicator of responses of a spittlebug (Auchenorrhyncha: Cercopidae) to climate change


Eur. J. Entomol. 93 (3): 319-324, 1996

A projected global temperature rise of 2-3C can be represented by the change in mean annual temperature experienced over some 10 of latitude or approximately 700 m of altitude in the hills of northern Britain. Using an altitudinal rather than latitudinal transect has the advantage of allowing studies of population dynamics and adaptation of life cycles at the centre and edge of a species' range within the same locality with similar vegetation and photoperiod.

Because of their unusual visibility in spittle masses, spittlebugs offer unusual opportunities to study population change in relation to environmental variables, including climate change.

Cold or drought - The lesser of two evils for terrestrial arthropods?


Eur. J. Entomol. 93 (3): 325-339, 1996

Water is an essential part of all living organisms and terrestrial arthropods are no exception. They have to balance water loss and water gain to and from their bodies, often over a wide range of environmental conditions. Water exists in the arthropod body in two main forms: free, bulk or freezable water (usually forming 65-75% of fresh weight), and unfreezable water (often inappropriately termed bound water) associated with membranes and other macromolecular structures. Many factors influence the body water content of arthropods from the physical environment and climatic effects to feeding activity, metabolism and life stage. Some species are adapted...

The relationship between water content and cold tolerance in the arctic collembolan Onychiurus arcticus (Collembola: Onychiuridae)


Eur. J. Entomol. 93 (3): 341-348, 1996

The arctic collembolan Onychiurus arcticus is freezing intolerant and experiences temperatures below -25C during winter periods of low air temperatures and only light snow cover. Summer-collected individuals have a mean (±SE) supercooling point of -6.1 ± 0.1C. This study was designed to measure the desiccation resistance and subsequent recovery of O. arcticus from partial dehydration and relate these to its cold-hardiness in terms of changes in the supercooling point (SCP) and solute concentration. Drying curves measured with a recording microbalance showed two distinct phases characteristic of the loss of free and chemically...

Anhydrobiosis and cold tolerance in tardigrades


Eur. J. Entomol. 93 (3): 349-357, 1996

A review of the literature regarding anhydrobiosis and cold tolerance in tardigrades is presented. During increasing desiccation, invertebrates like tardigrades, rotifers, nematodes and some collembolans are able to shut down metabolism to undetectable levels. When tardigrades are entering anhydrobiosis, a tun-like structure is formed, facilitated by structural adaptations of the cuticle. Slow dehydration is essential for tun formation, and the accumulation of trehalose during this process may help to stabilize phospholipids and proteins. Wax extrusion on the cuticle surface reduces transpiration. A fraction of 5-15% of the initial body water is retained...

The water conserving physiological compromise of desert insects


Eur. J. Entomol. 93 (3): 359-367, 1996

Insects living in arid tropical areas may spend long periods without access to free water, and at the end of the dry season they may be severely dehydrated. To survive under such conditions insects have developed a highly restrictive water economy, and tenebrionid beetles from arid tropical areas may lose water at a rate which is a hundred-fold lower than those of insects from humid habitats.

In most insects the dominant route of evaporative water loss is across the cuticle. In dry habitat tenebrionid beetles cuticular water permeability has been reduced so much that the water loss accompanying the exchange of respiratory gases across the spiracles...

Insect cold hardiness: A matter of life and death


Eur. J. Entomol. 93 (3): 369-382, 1996

It has often been stated that insects survive at low temperature by one of two main strategies, freeze tolerance and freeze avoidance by supercooling. Apart from the observation that the risk of freezing and its consequences is not the only injurious and possibly lethal effect of low temperature, it is interesting to consider a closely related question. If insects survive at low temperature by tolerating or avoiding freezing, under what circumstances do they die? A survey of the literature suggests there are five reasonably distinct situations representing decreasing levels of cold tolerance where death occurs (1) at some temperature below the freezing...

The wider integration of studies on insect cold-hardiness


Eur. J. Entomol. 93 (3): 383-403, 1996

Further progress in understanding insect cold-hardiness requires a broader perspective than hitherto. Such a broader approach is feasible, given the range of information now available on cold-hardiness and the variety and quality of equipment to study it. Comprehensive information on individual species is required, using the full range of available techniques, instead of piecemeal investigations. Comparisons of species must likewise be based on how their complete cold-hardiness strategies are structured, rather than on any particular contrasts between individual elements. Most importantly, a well based understanding of cold-hardiness requires wider...

Regulation of supercooling and ice nucleation in insects


Eur. J. Entomol. 93 (3): 405-418, 1996

Since most insects are unable to survive internal ice formation a key factor in their overwintering survival is the regulation of the temperature at which they spontaneously freeze, termed the supercooling point or temperature of crystallization. Most insects enhance their supercooling capacity during the winter by eliminating endogenous ice nucleators, accumulating low-molecular-weight polyols and sugars, and synthesizing hemolymph antifreeze proteins. In the absence of heterogeneous ice nucleators, small body size promotes supercooling to temperatures 25C or more below the freezing point of their body fluids. Although susceptibility to inoculative...

Tracking the profile of a specific antifreeze protein and its contribution to the thermal hysteresis activity in cold hardy insects


Eur. J. Entomol. 93 (3): 419-433, 1996

This study summarizes some important new directions in research on antifreeze protein biosynthesis and regulation. It describes the recent development and availability of essential biochemical and cellular tools that make possible more direct cellular investigations, and an assessment of the relationship between thermal hysteresis protein (THP) levels and antifreeze activity (both thermal hysteresis and recrystallization inhibition [RI]). These tools include: 1) the isolation of a specific THP of high activity designated Tm 12.86), and an additional endogenous activating factor of this antifreeze protein; 2) the ability to track the cellular and secretory...

Influence of temperature acclimation on respiration-temperature relationship in Tetrodontophora bielanensis (Collembola: Onychiuridae)


Eur. J. Entomol. 93 (3): 435-442, 1996

CO2 output in Tetrodontophora bielanensis was measured in the temperature range 0 to 20C using gas chromatography after acclimation to 5, 13 and 19C in the laboratory. The effect of acclimation temperature on mean CO2 output was not significant. The relationship between respiration and experimental temperature was found to vary depending on the acclimation temperature. It was not possible to obtain a significant mathematical description of the relationship after acclimation to 5C. The relationship was exponential at acclimation temperature 13C and linear after acclimation to 19C. The importance of acclimation to temperature...

Tolerance of soil-dwelling Collembola to high carbon dioxide concentrations


Eur. J. Entomol. 93 (3): 443-450, 1996

The tolerance of soil inhabiting Collembola to high carbon dioxide concentrations has been assessed in two collembolan life-forms: the surface-dwelling species Allacma fusca, Orchesella cincta and Tomocerus flavescens as well as Folsomia candida, a species from deeper soil layers. Behavioural changes within the former group could be observed during short-term exposure (one hour) to 5 and 10% CO2, respectively. In contrary, the limit of the tolerable carbon dioxide concentration of the latter species was only reached at 25% CO2. Long-term tolerances expressed as survival times of the half number of specimens...

Effects of interaction between temperature and CO2 on life-history traits of two Drosophila species (Diptera: Drosophilidae)


Eur. J. Entomol. 93 (3): 451-459, 1996

The effects of interaction between continuous exposure to different low CO2 concentrations (0% and 5%) and temperatures (14 and 25C) on several life-history traits were studied in the two sibling species D. melanogaster and D. simulans. The various combinations of the two factors were applied during egg-to-adult development and during adult life.

Developmental duration was increased by CO2, particularly at low temperature (14C), and viability reduced. At low temperature, body size was increased, although wing-length variation was reduced by CO2 in this condition. The fecundity of flies reared...

The multiple stressor approach in ecophysiology as exemplified by studies on temperate Collembola


Eur. J. Entomol. 93 (3): 461-466, 1996

Focussing on one stressor in ecophysiological research, such as low temperature or water shortage, may be practical but is unrealistic, and extrapolation based on these data e.g. to biogeographical distribution patterns, may fail. Ecophysiological research on temperate Collembola during estivation and overwintering serve as an example to show the importance of multiple stressor studies, including the simultaneous effects of food and water shortage and those of food shortage and low temperature. it is advocated to perform multiple stressor studies including toxic substances, such as heavy metals and organic toxicants.

Effects of heavy metals and fluorine on phagocytosis and phenoloxidase activity in Mamestra brassicae (Lepidoptera: Noctuidae)


Eur. J. Entomol. 93 (3): 467-473, 1996

Phagocytic response to injected iron saccharate and yeast cells (heat-killed Saccharomyces cerevisiae or viable Candida tropicalis) and haemolymph phenoloxidase (PO) activity were studied im Mamestra brassicae larvae fed on diets contaminated by copper, lead, cadmium of fluorine ions. In copper-stressed larvae, increased and reduced percentage of plasmatocytes and granular cells, respectively, and a reduced phagocytosis of iron saccharate were found. Cadmium- and fluorine-treatment reduced phagocytosis of S. cerevisiae. Cadmium showed a stimulatory effect, copper an inhibitory effect on phagocytosis of C. tropicalis....

Diapause development, diapause termination and the end of diapause


Eur. J. Entomol. 93 (3): 475-487, 1996

A workshop is an occasion to raise also ''nonproductive'' questions as stimuli for discussion between specialists from different fields: (1) What do we know about the processes leading to the end of diapause, and how can we discriminate this diapause end? (2) Is the diapause ''normally'' completed also when the ''natural'' diapause development is ''substituted'' by (re)activation?

It seems premature to search for criteria to directly monitor diapause end. We have to rely on the events of post-diapause development which can be recorded only after exposure to permissive environmental conditions. It should be defined clearly, in a study, whether...

Overwintering strategies of terrestrial invertebrates in Antarctica - the significance of flexibility in extremely seasonal environments


Eur. J. Entomol. 93 (3): 489-505, 1996

Antarctic terrestrial communities are characterised by their geographical isolation and the survival of extreme environmental stresses. Of particular significance to life history strategies of organisms in continental and maritime. Antarctic zones is the pronounced seasonality, with short (1-4 month) cold summers and long (8-11 month) winters. Activity and growth are largely limited to the summer period, although maintenance costs, undetectable in the short-term, may become significant over winter. Sub-Antarctic invertebrate communities experience a less rigorous regime, as climatic extremes are ameliorated by their oceanic environment, with positive...

Univoltinism and its regulation in some temperate true bugs (Heteroptera)


Eur. J. Entomol. 93 (3): 507-518, 1996

Various types of univoltine life cycle and its regulation were studied in Heteroptera. Very often, univoltinism was ensured by obligatory diapause in the species-specific stage. Obligatory egg diapause has been known in mirids Leptopterna dolobrata and Calocoris roseomaculatus. Obligatory nymphal diapause was investigated in Coptosoma scutellatum and obligatory adult diapause with quantitative photoperiodic regulation of nymphal growth was found in Coreus marginatus and Palomena prasina. Univoltinism occurs also in polyvoltine species. For example, in Arma custos and Pyrrhocoris apterus the univoltine...

Recurrent photoperiodic response in Graphosoma lineatum (Heteroptera: Pentatomidae)


Eur. J. Entomol. 93 (3): 519-523, 1996

Photoperiodic response was studied in a pentatomid bug, Graphosoma lineatum (L.). When insects were reared from eggs under constant temperature of 26C and long-day (18L : 6D) conditions, they developed into reproductive adults and started oviposition about 30 days after ecdysis. Short-day (12L : 12D) conditions and 26C induced adult diapause. Both diapausing and reproductive adults displayed the photoperiodic response. Reproductive adults stopped oviposition about 10 days after the transfer to short-day conditions, and diapause adults started oviposition about 40 days after the transfer to long-day conditions.

Adults from the field...