Changes in the ovaries of olive flies (Dacus oleae (Gmelin)) during the summer, and their relationship to temperature, humidity and fruit availability

Abstract. 1. Examination of the ovaries of female olive flies ( Dacus oleae ) from wild populations on Corfu during the summer months of 1975 indicated that all were non-gravid for a period of several weeks during June and July and the terminal follicles were resorbed.
2. Experiments in outdoor cages indicated that olive fruits could stimulate ovarian development during the summer months.
3. Experiments in constant temperature cabinets indicated that high temperatures (i. e. 26–29°C) in conjunction with a low humidity (45 ± 5°%) inhibited ovarian maturation.
4. Whereas the presence of olive fruits offset the effects of temperature and humidity on ovarian development at 26°C in all flies, at 29°C very few were able to mature their ovaries.
5. It is suggested that it is the interaction of temperature, humidity and access to fruit which determine when ovarian maturation ceases and recommences during the summer months.     

Seasonal changes in the common dab, Limanda limanda (L.) in Isle of Man Waters

Otolith accretion was greatest in summer when opaque bands were laid down and slowest in winter when hyaline rings were formed. Food intake was minimal in winter and maximal in summer. Liver weight was high in summer and winter and low in spring after spawning. Growth in length was higher in summer than winter. Gonad weight was greatest in winter for both sexes. Spawning occurred from February to April. After spawning males recovered earlier than females and testes ripened earlier than the ovaries. From winter to summer, the sea temperature increased from 7.5–13.0°C; the day length from 7–17h; and the salinity varied from 34.07−34.36%.     

The immune responses of dace Leuciscus leuciscm (L.) to injected antigenic materials

The fundamental features of the primary responses of dace Leuciscus leuciscus (L.), a freshwater cyprinid, to a number of standard antigens—haemocyanin, bovine serum albumin, horse serum, a bacterial antigen and an erythrocyte suspension, were examined. The fish were capable of producing either precipitating or agglutinating antibody in response to each of these antigens. Determinations of latent periods of antibody production by dace over a range of temperatures −18, 10, 5 and 2°C, showed that although the latent periods of the primary response increased with decreasing temperature, fish were able to produce antibodies to the erythrocyte antigen at 2°C and to the Salmonella and horse serum protein antigens at 5°C. The demonstration of antibodies at 5 and 2°C suggests that the fish are capable of producing antibodies over the complete range of their normal environmental temperatures.     

The effect of reduced temperature and salinity on the blood physiology of juvenile Atlantic cod

The osmolality and ionic composition of the blood of juvenile Atlantic cod Gadus morhua and their response to conditions of reduced temperature and salinity in summer‐ and winter‐acclimated individuals was investigated. Haematocrit percentage was relatively stable throughout the experimental procedures. Summer‐acclimated juvenile Atlantic cod had higher plasma osmolality than winter‐acclimated fish in ambient conditions. Plasma Na⁺ levels were, however, higher in winter conditions, while Cl⁻ did not vary between seasons. Temperature reduction (12, 9 and 6° C in summer and to 6 and 4° C in winter) induced a significant response in plasma osmolality and Na⁺ levels in summer, but only in Na⁺ levels in winter‐acclimated fish. A pronounced effect was seen in the summer 6° C treatment. Salinity treatments (24, 16 and 8) had a significant effect on almost all the variables in both summer and winter and resulted generally in dilution of ionic and osmotic concentrations of the plasma. This effect was pronounced in the lowest temperature treatments, with the greatest reduction observed in the summer 6° C treatment. This could suggest that winter‐acclimated fish are physiologically adapted to cope with lower seawater temperatures as opposed to summer‐acclimated fish.     

Seasonal changes in serum thyroid hormone levels of the feral brown bullhead, Ictalurus nebulosus Lesueur

Seasonal changes in serum L-thyroxine (T4) and triiodo-L-thyronine (T3) concentrations were measured in a feral population of brown bullheads, Ictalurus nebulosus . Serum T4 was elevated in mid April concomitant with the onset of gonadal recrudescence and the increase in ambient temperatures from the winter level. Thereafter, serum T4 levels were constant throughout the late spring and summer (except for a significant lowering in levels associated with the spawning and early postspawning period), declining to a low overwintering level by mid December. Serum T3 levels increased in April, and apart from a significant decrease in July associated with the postspawning period, rose progressively until August, after which levels declined progressively to reach overwintering levels again by mid December. Between mid April and mid May serum T4/T3 ratios fell from the high values found in fish during the winter months. Apart from variations associated with the fluctuations of T4 and T3 concentrations in the spawning and early postspawning periods, serum T4/T3 ratios remained at a low level throughout the summer and early autumn months, and rose again in October to the overwintering levels. The circannual cycles are discussed in relation to the possible role of the thyroid hormone in gonadal maturation and metabolism in this species.     

Seasonal variation in freezing tolerance of the New Zealand alpine cockroach Celatoblatta quinquemaculata

1. The cold hardiness of the alpine cockroach Celatoblatta quinquemaculata was investigated. This species is found at 1360 m a.s.l. beneath schist slabs on the Rock and Pillar Range (Central Otago, New Zealand). Cockroaches were collected monthly from January to December 1996, and their LT₅₀ and supercooling points determined.
2. Celatoblatta quinquemaculata was freezing tolerant throughout the year, with a lower lethal temperature in winter of – 8.9 °C. Celatoblatta quinquemaculata was also found frozen under rocks in the field when the under-rock temperature was below – 3 °C, and could survive being frozen at – 5 °C for 4 days in the laboratory.
3. There was a marked decrease in LT₅₀ temperature from – 5.5 °C in April to – 7.5 °C in May. This coincides with decreasing temperatures from summer through autumn to winter, during which temperatures beneath snow-covered rocks may reach – 7.3 °C.
4. Supercooling points fluctuated during the year, with an increase from – 4.2 °C in autumn to – 3.4 °C in winter. Supercooling point was highest in spring, and changes in supercooling point do not appear to be related to changes in LT₅₀.
5. Recordings of environmental temperatures from the Rock and Pillar Range suggest that cockroaches may undergo up to twenty-three freeze–thaw cycles in the coldest month of the year, and that they may remain frozen for periods of up to 21 h. Maximum cooling rates recorded in the field (0.01 °C min^–1) were 100-fold slower than laboratory cooling rates, so survival estimates from laboratory experiments may be underestimates.     

Survival at low temperature of larvae of the pine processionary moth Thaumetopoea pityocampa from an area of range expansion

1 Larvae of Thaumetopoea pityocampa (Lepidoptera: Notodontidae) develop throughout the winter, although their feeding activity and survival can be impaired by adverse climatic factors. The present study investigated the survival at low temperature of larvae originating from a population with range expansion in an alpine valley in Northern Italy.
2 The supercooling point of individually analysed larvae averaged at −7 °C. This value insufficiently described the cold hardiness of the larvae; 39% of the tested larvae were alive when returned to room temperature immediately after freezing. When larval colonies inside their nest were exposed to −17 °C for 1 h after gradual temperature decrease, survival was 70.4%.
3 Rearing of larvae in the laboratory at different day/night temperatures indicated an effect of cumulative chill injury on larvae. A logistic regression explained the relationship between negative thermal sum (h°C below 0 °C) received in the laboratory experiment and larval survival. A similar relationship was demonstrated between negative thermal sum and survival of larval colonies in the field.
4 In the laboratory experiment, some tested larvae were able to survive for up to 8 weeks without feeding depending on rearing temperature. As expected, feeding occurred only when larvae were reared at temperatures of 9 °C day/0 °C night.
5 We classify the larvae of T. pityocampa as being moderate freezing tolerant. The winter behaviour allows this species to track climate warming by a rapid expansion into those areas that become compatible with the insect's development.     

Seasonal changes in fast-starts in the short-horn sculpin: integration of swimming behaviour and muscle performance

In short-horn sculpin Myoxocephalus scorpius , the power requirements for fast-start swimming and the length-specific velocity of the curvature wave travelling down the spine ( Û ) were not influenced significantly by acclimation to summer and winter conditions at test temperatures of 5 and 15° C. However, in-vivo and in-vitro muscle performance exhibited acclimation responses at 15° C. Seasonal acclimation altered the escape performance curves for power and Û significantly over a wider temperature range of 0·8–20° C. Û was significantly higher at 20° C in the summer- than winter-acclimation group. The acclimation of lower levels of physiological organization at 15° C may thus serve to extend the thermal limits for escape performance in summer acclimated fish.     

Overwintering survivorship of pupae of the mimosa web worm, Homadaula anisocentra (Lepidoptera: Plutellidae), in an urban landscape

ABSTRACT. 1. Overwintering survivorship of pupae of the mimosa webworm, Homadaula anisocentra Meyrick (Lepidoptera: Plutellidae), was examined in several urban habitats in central Iowa during the winters of 1981–82, 1982–83 and 1983–84.
2. Survivorship and supercooling point temperatures were determined throughout the winters. Corroborative laboratory studies were conducted during the winter of 1982–83.
3. Minimum ambient temperatures that equalled or were below the supercooling point of the insect, at any time, were lethal.
4. Prolonged cold exposure below 0°C and above the supercooling point resulted in high mortality levels. To quantify this relationship, a concept of minimum-temperature exposure was developed by tabulating the number of degrees that the daily minimum temperature was below 0°C for a given sampling period.
5. Some mimosa webworm pupae were found to overwinter in highly protected sites (2.5–5.0°C warmer than the ambient air temperatures) in the urban environment, resulting in less minimum-temperature exposure and reducing the probability of reaching the lethal supercooling point temperature.     

Fattening strategies of wintering great tits support the optimal body mass hypothesis under conditions of extremely low ambient temperature

1.  In a seasonal environment, subcutaneous energy reserves of resident animals often increase in winter and decline again in summer reflecting gradual seasonal changes in their fattening strategies. We studied changes in body reserves of wintering great tits in relation to their dominance status under two contrasting temperature regimes to see whether individuals are capable of optimizing their body mass even under extreme environmental conditions.
2.  We predicted that dominant individuals will carry a lesser amount of body reserves than subordinate great tits under mild conditions and that the body reserves of the same dominant individuals will increase and exceed the amount of reserves of subordinates under conditions of extremely low ambient temperatures, when ambient temperature dropped down to −37 °C.
3.  The results confirmed the predictions showing that dominant great tits responded to the rising risk of starvation under low temperatures by increasing their body reserves and this was done at the expense of their safety.
4.  Removal experiments revealed that lower body reserves of subordinate flock members are due to the increased intraspecific competition for food under low ambient temperatures.
5.  Our results also showed that fattening strategies of great tits may change much quicker than previously considered, reflecting an adaptive role of winter fattening which is sensitive to changes in ambient temperatures.     

Bimodal life cycle of the burying beetle Nicrophorus quadripunctatus in relation to its summer reproductive diapause

Abstract 1. Under natural conditions in Kyoto, Japan, the reproductive activities of Nicrophorus quadripunctatus Kraatz (Coleoptera: Silphidae) decreased in summer and the species showed a bimodal life cycle.
2. In the laboratory, most adult pairs raised at 20 °C under a LD 12:12 h regime reproduced when provided with a piece of chicken. In adults raised at 20 °C under a LD 16:8 h regime, however, both reproductive behaviour and ovarian development were reduced. It is concluded that these adults entered a reproductive summer diapause.
3. High temperature (25 °C) also suppressed the reproductive behaviour even under a favourable LD 12:12 h regime. In the field, therefore, adults reduce their reproductive activity in summer because of diapause induced by long-day photoperiods and direct inhibition of reproduction by high temperatures.
4. When the temperature was changed from 20 °C to 25 °C immediately after hatching of larvae, they reached the wandering stage in 95% of adult pairs. When the temperature was changed from 20 °C to 25 °C immediately after oviposition, however, no larvae hatched in 85% of pairs. Egg mortality was significantly higher at 25 °C than at 20 and 22.5 °C; no eggs hatched at 27.5 °C. The physiological mechanisms for reducing reproduction probably prevent the beetles from inefficient oviposition in summer.     

The roles of temperature and diapause in the life history of a temperate-zone dragonfly: Argia vivida (Odonata: Coenagrionidae)

Abstract. 1. The life cycle of Argia vivida Hagen generally took longer to complete in the field than was predicted on the basis of the thermal sum accumulated in laboratory rearing.
2. The prediction of a bivoltine life-cycle from geothermal sites with either a constant annual temperature of 26°C or thermal range of 11–31°C was not borne out because the intervention of short-day induced developmental delays in later larval instars extended the life cycle to 1 year.
3. This diapause, which synchronizes adult emergence with favourable summer temperatures, was also present in larvae from sites with annual temperature ranges of 0–33°C and 5–20°C.
4. At these colder sites completion of the life cycle takes 2 and 3 years respectively and dragonflies must be in cold-resistant stages during the winter. A long-day diapause, principally affecting late-instar larvae below a certain size during the summer, achieves this.
5. Large diurnal temperature fluctuations at the 0–33°C site markedly increase the useful thermal energy available to larvae for growth over that predicted by the thermal sum equation.
6. The interaction between the effects of temperatures favourable for growth and day-length-governed diapause, synchronize the emergence of the low-temperature sensitive adult stage of this tropical dragonfly with northern-latitude summers at a variety of habitats.     

The link between migration, the reproductive cycle and condition of Sardinella aurita off Mauritania, north-west Africa

The annual migration pattern of round sardinella Sardinella aurita up and down the north-western African coast between 12° N (Senegal) and 22° N (western Sahara) was shown to be associated with spawning activity and a distinct seasonality in fish condition, based on monthly sampling from commercial catches (2000–2003). Some S. aurita were found to spawn throughout the entire year, but a peak in spawning existed during the summer (June to September). The spawning cycle is apparent from seasonality in maturity stages, but is also demonstrated by the increase in gonad mass and fat content of the fish in springtime, the period preceding spawning. During the months after spawning, although feeding is maintained, the physical condition of the fish collapses, and fat content rapidly declines.     

Water temperature in a stream gravel bed and implications for salmonid incubation

SUMMARY. 1. Water temperatures were recorded at hourly intervals in the gravel of a trout spawning area in a small stony stream at depths of 0–20 cm in 1985–86 and 0– 40 cm in 1987.
2. As depth within gravel increased, the size of the daily fluctuations reduced and their time of occurrence was delayed by about 12 min cm⁻¹' in 1985–86 and about 6 min cm⁻¹ in 1987.
3. From October to February mean temperatures at 20 cm depth were, on average, 0.5°C higher than those at the gravel surface. This reflected elevated daily minima more than it reflected elevated daily maxima.
4. From March to July daily minima were lower and daily maxima were higher in the stream than in the gravel. Consequences were: (a) an appreciable increase in mean daily range at all depths in the gravel during the summer, (b) higher daily means (by an average of about 0.4°C) in the water than in the gravel in May to August.
5. Some implications for the early development of salmonid fish are considered.     

Growth and survival of Azolla filiculoides in Britain I. Vegetative production

Azolla filiculoides Lam. causes serious weed problems in Britain, but its long-term survival might be limited by winter death. The aim of this study was to establish the low temperature responses and limitations of A. filiculoides sporophytes.
In the laboratory, normal vegetative growth was shown to continue at 5°C. Reddening of plants was a response to low temperature and high light conditions which could be prevented by shading. Adult plants died after short (18 h) exposure to −4°C but survived sub-zero temperatures >−4°C. Evidence was found of seasonal changes in chill tolerance, but not in freeze tolerance.
In outdoor culture, plants survived encasement in ice and air temperatures to −5°C. Additional evidence suggested that natural populations can readily survive air temperatures much lower than this. Microclimatic effects are likely to be responsible for this discrepancy between laboratory and outdoor culture results.
Three phenotyes were identified; survival, colonizing and mat forms.     

Possible impact of mild winters on zooplankton succession in eutrophic lakes of the Atlantic European area

1. We report on a long-term study (1975–94) of water temperatures and plankton in a eutrophic lake (Heiligensee, Berlin, Germany). Using a phenomenological approach, we use historical data to infer how an increase in air temperature has influenced a natural zooplankton community.
2. Air temperatures in Berlin showed a significantly rising trend between 1975 and 1994. Mean winter air temperatures in the last 8 years always exceeded the long-term mean.
3. A rising trend was also found for April water temperature, which increased significantly beginning in 1988–89. An increase of 2.58°C in the last 21 years was recorded using a linear model. A significantly decreasing trend was found in June but no trend was noted for the other summer months.
4. Phytoplankton composition shifted from a dominance of diatoms and cryptophytes during winter and spring in the 1980s towards a dominance of cyanobacteria in 1990–94.
5. The dominant zooplankton species in spring shifted in recent years from the large-bodied Daphnia galeata to the smaller D. cucullata . Cyclops kolensis , previously the only invertebrate predator during winter, decreased in abundance while C. vicinus , usually present during spring and autumn, increased in abundance and was numerous during winter, a season passed in diapause in the earlier years.
6. Because direct and indirect temperature effects are species specific, we put forward the hypothesis that zooplankton species, rather than functional groups, are the nexus between environmental stress, such as rising air temperatures, and ecosystem changes.     

Reproductive biology of the threatened golden galaxias Galaxias auratus Johnston and the influence of lake hydrology

Golden galaxias Galaxias auratus (31–235 mm fork length, L _F) were collected monthly from littoral habitats in Lakes Crescent and Sorell, Tasmania, Australia, between July 2000 and December 2002. Spawning habitats were identified and monitored in both lakes, and surveyed in Lake Crescent. Trends in gonado-somatic indices and reproductive stages of development indicated that gonad development in both sexes begins in midsummer and peaks in late autumn to early winter. Males mature at smaller sizes (50% at 52 mm L _F) than females (50% at 76 mm L _F), larger individuals are predominately females (95% of fish ≥138 mm L _F), and overall male to female ratios are female biased ( c . 1:2). Spawning occurs late autumn to early spring (water temperatures = 1·4–9·7° C) with peaks in spawning activity in winter (mean water temperatures <5° C). Demersal adhesive eggs ( c. 1·5 mm diameter) were found on cobble substrata ( c. 20–250 mm diameter) in littoral areas ( c. 0·2–0·6 m deep) and fecundity of fish 71–181 mm L _F ranged from 619 to 14 478 eggs. The rate of change in water level over the 20 days prior to monthly sampling was important in explaining the occurrence of spent fish and this accounted for temporal differences in spawning between the populations. Lake hydrology influences the reproductive cycle of G. auratus by possibly providing a stimulus for spawning and it controls the availability of spawning habitat in Lake Crescent. Seasonal hydrological cycles ( i.e. rises during late autumn to winter) and a minimum water level of 802·20 m Australian Height Datum in Lake Crescent during autumn (above which littoral areas of cobble substratum are inundated) are critical to G. auratus populations.     

Behavioural studies on the lesser sandeel Ammodytes marinus (Raitt) III. The effect of temperature on activity and the environmental control of the annual cycle of activity

The behaviour of the lesser sandeel, Ammodytes marinus (Raitt), has been investigated at 5, 10 and 15° C, using a photographic method of recording activity. The activity patterns at 10 and 15° C were very similar, there being a high level of swimming activity during the light period, which fell to a low level at 5° C. It was also lower at 10° C at the end of the experiment than at the beginning and it is suggested that this might have been due to an increase in the fat contents of the fish. The feeding rate of the fish was measured and showed a Q ₁₀ of 2.08 for the temperature range 5–15° C. The annual cycle of activity of A. marinus is discussed in relation to seasonal changes in food availability, light and temperature, and in the fat content of the fish. It is concluded that after spawning in the December–January period the fish remain buried in the sand until April, because of the limiting effect on swimming and feeding activity of the environmental factors in the intervening period. The proportion of fish available for capture at the start of the fishery in April is related mainly to temperature, but food (as measured by numbers of copepods) light intensity and photoperiod are by then increasing rapidly. After July the fishery ceases and it is thought that this is because the fish have entered an overwintering stage, during which they remain buried in the sand. This phase is also thought to be associated with the maturation of the gonads in readiness for the winter spawning. The factors causing the fish to enter this stage are as yet undetermined but may be related to the attainment of a certain level of fat content.     

Possible impact of mild winters on zooplankton succession in eutrophic lakes of the Atlantic European area

1. We report on a long-term study (1975–94) of water temperatures and plankton in a eutrophic lake (Heiligensee, Berlin, Germany). Using a phenomenological approach, we use historical data to infer how an increase in air temperature has influenced a natural zooplankton community.
2. Air temperatures in Berlin showed a significantly rising trend between 1975 and 1994. Mean winter air temperatures in the last 8 years always exceeded the long-term mean.
3. A rising trend was also found for April water temperature, which increased significantly beginning in 1988–89. An increase of 2.58°C in the last 21 years was recorded using a linear model. A significantly decreasing trend was found in June but no trend was noted for the other summer months.
4. Phytoplankton composition shifted from a dominance of diatoms and cryptophytes during winter and spring in the 1980s towards a dominance of cyanobacteria in 1990–94.
5. The dominant zooplankton species in spring shifted in recent years from the large-bodied Daphnia galeata to the smaller D. cucullata . Cyclops kolensis , previously the only invertebrate predator during winter, decreased in abundance while C. vicinus , usually present during spring and autumn, increased in abundance and was numerous during winter, a season passed in diapause in the earlier years.
6. Because direct and indirect temperature effects are species specific, we put forward the hypothesis that zooplankton species, rather than functional groups, are the nexus between environmental stress, such as rising air temperatures, and ecosystem changes.     

Novel sulfur-oxidizing streamers thriving in perennial cold saline springs of the Canadian high Arctic

The perennial springs at Gypsum Hill (GH) and Colour Peak (CP), situated at nearly 80°N on Axel Heiberg Island in the Canadian high Arctic, are one of the few known examples of cold springs in thick permafrost on Earth. The springs emanate from deep saline aquifers and discharge cold anoxic brines rich in both sulfide and sulfate. Grey-coloured microbial streamers form during the winter months in snow-covered regions of the GH spring run-off channels (−1.3°C to 6.9°C, ∼7.5% NaCl, 0–20 p.p.m. dissolved sulfide, 1 p.p.m. dissolved oxygen) but disappear during the Arctic summer. Culture- and molecular-based analyses of the 16S rRNA gene (FISH, DGGE and clone libraries) indicated that the streamers were uniquely dominated by chemolithoautotrophic sulfur-oxidizing Thiomicrospira species . The streamers oxidized both sulfide and thiosulfate and fixed CO₂ under in situ conditions and a Thiomicrospira strain isolated from the streamers also actively oxidized sulfide and thiosulfate and fixed CO₂ under cold, saline conditions. Overall, the snow-covered spring channels appear to represent a unique polar saline microhabitat that protects and allows Thiomicrospira streamers to form and flourish via chemolithoautrophic, phototrophic-independent metabolism in a high Arctic winter environment characterized by air temperatures commonly below −40°C and with an annual average air temperature of −15°C. These results broaden our knowledge of the physical and chemical boundaries that define life on Earth and have astrobiological implications for the possibility of life existing under similar Martian conditions.