Temperature experienced during vitellogenesis influences ovarian maturation and the timing of ovulation in common wolffish

Temperature treatment of common wolffish Anarhichas lupus during vitellogenesis affected the time of final maturation; ovulation in fish held at 8 and 12° C from mid-April to October was about four and five weeks delayed, compared with a 4° C group. Fish in the 8° C group had significantly larger eggs than those in the 4° C and the 12° C groups, and a significantly higher egg production than fish in the 12° C group. Temperature treatment did not affect either fertilization rate or relative fecundity, but absolute fecundity was significantly lower in the 12° C group than the other groups due to poor growth of the fish at high temperature. This did not affect the numbers of spawning individuals. There was a trend towards lower egg survival to the eyed stage in the 12° C group compared to the 4 and 8° C groups, although the effect was not statistically significant. The results indicate that both the timing of final maturation and investment in ovarian growth in common wolffish are affected by temperature experienced during vitellogenesis.     

Temperature-dependent development rates of cod Gadus morhua eggs

Temperature development relationships were determined for batches of Irish Sea cod Gadus morhua eggs incubated in flow-through incubators. Hatching began 16·4 days after fertilization (DAF) at 6° C, 10·3 DAF at 8° C, 9·4 DAF at 10° C and 7·4 DAF at 12° C. Egg mortality increased at the higher temperatures, but survival was >80%. Results were compared with published data at four comparable stage end points: the end of blastula, the end of gastrula, the point of growth of the embryo completely surrounding the yolk and the point when 50% of the eggs were hatched. All the studies showed a curvilinear relationship between age at stage and temperature. There was a 12 day inter-study difference in time to 50% hatch at 2° C and 4 day difference at 10° C. There were no consistent trends that differentiated eastern v. western, or northern v. southern populations. A single model for cod egg incubation time from fertilization to 50% hatch was derived based on data from six cod populations, but it is recommended that individual stock relationships should be used where possible.     

Comparative developmental biology of pink salmon, Oncorhynchus gorbuscha, in southern British Columbia

Eggs and alevins from 21 families of pink salmon, Oncorhynchus gorbuscha , from five odd-year broodline stocks spawning in southern British Columbia were incubated under controlled water temperatures of 4° C, 8° C and 12° C. There were significant differences in egg survival among stocks and among families within stocks at all incubation temperatures, but the differences were greatest at 4° C. Alevin survival was at least 97% for each stock at each temperature. The most northern spawning stocks had higher egg survival at 4° C than did the others. Hatching time of the alevins and emergence time of the fry were similar for all five stocks. Alevins hatching at 8° C were longer than those hatching at 4°C or 12°C, but there were no stock differences in alevin length or tissue weight. Stocks with larger eggs produced alevins of greater total weight and more yolk. Emergent fry from Vancouver Island stocks had the greatest tissue weight at 12° C, but Fraser River fry were heaviest at 8° C. There were significant differences among families within stocks for alevin and fry size parameters, suggesting that family variation should be accounted for in studies of salmonid developmental biology.     

Thermal influences on temporal changes in plasma testosterone and oestradiol-17β concentrations during gonadal recrudescence in female common wolffish

Temperature treatment during ovarian recrudescence influenced temporal changes in plasma testosterone (T) and oestradiol-17β (E₂). In fish exposed to 8 and 12° C early in the cycle the peaks of both T and E₂ were delayed by 4 weeks in comparison with those of fish held at 4° C throughout the experiment. These differences were accompanied by corresponding shifts in the timing of ovulation.     

Effect of temperature on the biology of Creontiades dilutus (Stål) (Heteroptera: Miridae)

The egg and nymphal development, fecundity and survival of the green mirid, Creontiades dilutus were examined at a range of temperatures and a modified day-degree model fitted to the data. Day degree (DD) requirements for egg and nymphal development, and threshold temperatures were calculated from the fitted lines. Female fecundity and longevity, egg and nymphal development, and survival of C. dilutus were significantly influenced by temperature. Eggs and nymphs failed to complete development at temperatures below 17 and at 38°C. Females also failed to produce any eggs at 11 and 38°C. The optimum temperature range for female fecundity was found to be 26–32°C. The optimum temperature for the development of eggs was calculated from the model as 30.5°C and for nymphs as 31.5°C. The threshold temperature for development was 15.8°C for egg and 15.1°C for nymph; 69.4 and 156.7 DD were required for completing the egg and the nymphal development, respectively. At the optimum temperature, it was estimated that development from egg to adult took 15 days. Survival was highest at 26°C for eggs and at 30–32°C for nymphs.     

Diapause induction and coloration in the Senegalese grasshopper, Oedaleus senegalensis

Abstract. Embryonic diapause induction in the Senegalese grasshopper, Oedaleus senegalensis Krauss (Orthoptera: Acrididae), is influenced both by the photoperiod and the temperature experienced by females. High temperatures (40°C) and long photoperiods (LD 14:10h), which characterize the beginning of the rainy season in the Sahel, cause non-diapausing eggs to be laid. Lower temperatures (25°C) and shorter photoperiods (LD 12:12h), which occur at the end of the rains, result in the production of diapausing eggs. At 30°C and constant photoperiods, O. senegalensis exhibited a long-day-short-day response with critical photoperiods of c. 13 h and c. 20 h, only the former value being of ecological significance. The photoperiodically sensitive stages to diapause induction in females occurred from the fifth stadium onwards. Temperature also affected the coloration of both nymphs and adults. Dark-black and pale-white individuals were produced by low (25°C) and high (40°C) temperatures respectively, whereas an intermediate temperature (30°C) produced individuals which were greyish brown. These results are discussed in relation to the ecology of O. senegalensis.     

The effect of temperature and fish size on growth and feed efficiency ratio of juvenile spotted wolffish Anarhichas minor

The growth properties of juvenile spotted wolffish Anarhichas minor reared at 4, 6, 8 and 12° C, and a group reared under 'temperature steps', (T‐step) i.e . with temperature reduced successively from 12 to 9 and 6° C were investigated. Growth rate and feed efficiency ration was significantly influenced by temperature and fish size. Overall growth rate was highest at 6° C (0·68% day⁻¹) and lowest at 12° C (0·48% day⁻¹), while the 4 and 8° C, and the T‐step groups had similar overall growth rates, i.e . 0·59, 0·62 and 0·51% day⁻¹ respectively. Optimal temperature for growth ( T _{opt G} ) and feed efficiency ratio (T_{opt FCE}) decreased as fish size increased, indicating an ontogenetic reduction in T _{opt G} and T _{opt FCE}. The results suggest a T _{opt G} of juvenile spotted wolffish in the size range 135–380 g, dropping from 7·9° C for 130–135 g to 6·6° C for 360–380 g juveniles. The T _{opt FCE} dropped from 7·4° C for 120–150 g to 6·5° C for 300–380 g juveniles. A wider parabolic regression curve between growth, feed efficiency ratio and temperature as fish size increased, may indicate increased temperature tolerance with size. Individual growth rates varied greatly at all time periods within the experimental temperatures, but at the same time significant size rank correlations were maintained and this may indicate stable size hierarchies in juvenile spotted wolffish.     

Effects of temperature on the development and survival of an endangered butterfly, Shijimiaeoides divinus barine (Leech) (Lepidoptera: Lycaenidae)

The effects of temperature on the development and survival of Shijimiaeoides divinus barine were examined in the laboratory in 2008. The eggs and larvae were reared at temperatures of 15, 17.5, 20, 25, 30 and 35°C with a long-day photoperiod of 16 h light : 8 h dark (16L : 8D). The highest hatchability of eggs was 88.0% at 20°C, but hatchability at high temperatures of 30 and 35°C was 30 and 0%, respectively. The lowest and highest survival rates from the first to third instar were 18.8% at 15°C and 76.9% at 20°C. Few deaths were observed after the fourth instar. The shortest developmental periods of the eggs and larvae were 4.0 and 15.8 days at 30°C, and the durations of the egg and larval stages increased significantly as the temperature decreased. The developmental zero and thermal constants were 9.6°C and 82.6 degree–days for the egg stage, and 10.7°C and 306.8 degree–days for the larval stage. The developmental period of the natural population of S. divinus barine in Azumino City, Nagano Prefecture was calculated using the developmental zero, thermal constants and Azumino City temperature data.     

Effects of temperature of adults and eggs on the induction of embryonic diapause in the band-legged ground cricket, Dianemobius nigrofasciatus

Abstract.  Eggs laid by adult female Dianemobius nigrofasciatus , reared under long-day (LD 16 : 8 h, 25 °C) or short-day (LD 12 : 12 h, 25 °C) conditions from the nymphal stage, are kept at several constant temperatures. At 22.5–30.0 °C, eggs laid by long-day adults show lower incidences of diapause than those laid by short-day adults. In both eggs laid by adults under long-day conditions and those under short-day conditions, the higher the temperature at which the eggs are kept, the lower the incidence of diapause. When eggs of long-day adults are exposed to a low-temperature pulse (10 °C, 24 h) on the day of deposition (day 0), the incidence of diapause increases. The low-temperature pulse on day 1 does not increase the incidence of diapause. By contrast, when the eggs of short-day adults are exposed to a high-temperature pulse (35 °C, 24 h) on day 0 or day 1, the incidence of diapause decreases. The temperature pulses on day 0 are more effective at diapause prevention. Staining of diapause eggs by the Feulgen–Rossenbeck method shows that the eggs enter diapause at the blastoderm stage, which is on day 1 or day 2 at 25 °C. The exposure of adults to long days and higher temperatures prevents the eggs from entering diapause. In D. nigrofasciatus , embryonic diapause is controlled by maternal effects, adult photoperiod and temperature, and egg temperature before or at diapause.     

Diapause duration, survival in relation to desiccation and egg-pod morphology of the Senegalese grasshopper, Oedaleus senegalensis

Abstract. The Senegalese grasshopper, Oedaleus senegalensis (Krauss) (Orthoptera: Acrididae), is periodically a devastating pest of subsistence crops in the sahelian zone of West Africa.Egg diapause has been suggested as an important component of the mechanism acting to generate outbreaks and therefore diapause duration, egg survival in relation to desiccation and egg-pod morphology were investigated in this study.
Three months after oviposition, 50% of initially diapausing egg pods maintained in the laboratory exhibited 'partial emergence' and produced hoppers.No difference in diapause duration was evident between egg pods maintained at a constant 30 ± 1°C and those maintained under alternating temperature conditions of 23 ± 1°C and 35 ± 1°C.Laboratory maintained eggs showed significant variation in diapause duration with diapause lasting between 2 months and 4 years.Diapause duration was shorter in the field with only c. 1.4% of eggs remaining in diapause after a single dry season (6–7 months).Survival of eggs in relation to desiccation was high in the field and low in the laboratory, and field eggs lost only c. 20% of their body weight over the dry season.Survival of diapausing and non-diapausing egg pods in the laboratory was similar, indicating that diapause in this species is primarily a mechanism for preventing emergence at an inappropriate time of year, rather than conferring any additional resistance to desiccation.Egg pods oviposited under diapause-inducing conditions (LD 14:10 h, 25°C) were significantly shorter than those laid under non-diapausing conditions (LD 10:14 h, 40°C).These results are discussed both in relation to possible O.senegalensis 'bet-hedging' strategies and to the probable mechanism operating behind major outbreaks of this species.     

Relationships between maternal size, egg diameter, time of spawning season, temperature, and length at hatch of Atlantic silverside, Menidia menidia

Eggs were stripped from gravid Atlantic silversides collected on two occasions, once during the early part and once during the late part of the natural spawning season. Unfertilized egg diameter was not correlated with length of the female, nor was it significantly larger during the early part of the season. Eggs were fertilized and incubated in the laboratory. Larval length at hatch was measured every 24 h during the hatching period after embryos were incubated at 18 or 25° C. Lower incubation temperature caused a significantly greater length at hatch for the offspring of each of the 20 females studies. In most cases (17 out of 20 at 25° C, 10 out of 20 at 18° C), there was a significant decrease in length at hatch during the hatching period for a given female's eggs incubated at a given temperature. In the natural environment, larvae hatched early in the season under cooler temperatures could average 12% longer than those hatched later under warmer temperatures, and therefore may have a greater chance of survival. The results help to explain the observation that field-caught M. menidia that hatched early in the season are larger at any given age than those that hatched late in the season.     

Geographical variation in Japan in egg development of the mayfly, Ephoron shigae (Ephemeroptera: Polymitarcyidae)

1. The effect of temperature on embryonic development was compared in four populations, two bisexual and two unisexual, of Ephoron shigae , including one each near the northern and southern periphery of the species range in Japan.
2. Eggs from every population were chilled at 4, 8 or 12 °C for diapause development after 50 days at 20 °C for pre-diapause development (experiment I). Some eggs hatched during chilling at 8 °C or 12 °C, whereas no eggs hatched at 4 °C. The rate of hatching in a given condition of chilling was higher for the eggs from warmer winter environments.
3. Chilling at 4 or 8 °C effectively facilitated diapause development. Chilling at 12 °C was, in general, not so effective, but relatively effective for the eggs from warmer winter environments.
4. Eggs were incubated at 8, 12, 15 or 20 °C after chilling at 4 °C to examine the effect of temperature on post-diapause development (experiment II). The eggs incubated at higher temperature after chilling hatched quicker and more synchronously and had higher hatching success.
5. The relationship between temperature and the days required for hatching after chilling was well described by the power function. There was no significant difference in the slope of the regression lines (i.e. temperature dependency) among local populations. However, a longer time was required for hatching at a given temperature for the population from the colder winter environment.
6. There was no detectable difference in the observed intraspecific variations between unisexual and bisexual populations.     

Genetic engineering in rainbow trout, Salmo gairdnerii Richardson, by the suppression of meiotic and mitotic metaphase

Diploid gynogenesis in rainbow trout eggs was induced by a heat shock applied after fertilization with UV irradiated sperm. Survivals were high when the heat treatment was given soon after fertilization at times corresponding to the completion of egg meiosis but were low at all other times. Increases in survival occurred, however, when the heat treatment was given at 4 h 30 min and 5 h after fertilization, with an incubation temperature of 10°C, and at 9 h after fertilization, with an incubation temperature of 5°C. Electrophoretic analysis at three enzyme loci demonstrated a significant increase in homozygous offspring from eggs given these later heat treatments when compared to offspring from eggs treated between 40 and 70 min after fertilization, again with an incubation temperature of 10°C. There was still a significant frequency of heterozygotes in these groups, however, probably of spontaneous origin via diploidization during meiosis. No tetraploid alevins were observed after normal fertilization and attempted suppression of first mitosis.     

Effects of temperature and soil moisture on survival of eggs of the mosquito Psorophora columbiae (Diptera: Culicidae)

The results of laboratory tests indicated the average survival rates for Psorophora columbiae eggs remained quite high for all of the egg populations exposed to a temperature of 27°C (range 83.0–100.0% survival) after 96 days of exposure, except for the non‐diapausing eggs on dry soil (66.3%). In regard to the exposure of egg populations to moderately cold temperatures (i.e. 8°C, 4°C and ?2°C) for periods of up to 16 days, survival rates for egg populations exposed to 8°C continued to remain relatively high (average >85%) for the remainder of the experimental exposure period (i.e. 96 days). Diapausing Ps. columbiae eggs were more tolerant (82.0% survival) to low temperatures (?2°C) than non‐diapausing eggs (2.4% survival) for 64 days, particularly at temperatures of and below 4°C. Diapausing and non‐diapausing eggs were similar in their ability to survive under high temperatures (34°C and 38°C). High soil moisture (30–40%) or substrate moisture (95% relative humidity) content appeared to enhance the ability of the mosquito eggs to survive both low and high temperature extremes.     

Muscle growth in yolk-sac larvae of the Atlantic halibut as influenced by temperature in the egg and yolk-sac stage

Atlantic halibut eggs and yolk-sac larvae were incubated at 1, 5 and 8° C. Eggs incubated at 8° C gave slightly shorter larvae at hatching with a significantly smaller total cross-sectional area of white muscle fibres than eggs incubated at 5° C. Transport of eggs 2 days prior to hatching gave significantly longer larvae at hatching with a significantly larger red fibre cross-sectional area than when eggs were transported shortly after the blastopore closure. A higher survival until 230 degree days after hatching was also observed in the former group. All eggs incubated at 1° C died before hatching and all larvae incubated at 1° C died before 45 degree days after hatching. From hatching until 230 degree days the total white cross-sectional area increased threefold in all temperature groups. The increase in white cross-sectional area was entirely due to hypertrophy between hatching and 150 degree days (10 mm L _S). Recruitment of new white fibres increased in germinal zones at the dorsal, ventral and lateral borders of the myotome from 150 degree days onwards, but at 230 degree days (12–13 mm L _S) the recruitment fibre zone constituted <10% of the total white cross-sectional area. Larval incubation at 8° C gave slightly longer larvae with a significantly larger cross-sectional area of recruitment fibres at 230 degree days than incubation at 5° C. The larval group incubated at 8° C also had a significantly lower survival until 230 degree days than did the 5° C group. Incubation temperature regimes did not affect the volume density of myofibrils in the axial muscle fibres at 230 degree days. Thus hypertrophy is the predominant mechanism of axial white muscle growth in Atlantic halibut yolk-sac larvae and an increased rearing temperature during the yolk-sac stage increases white muscle fibre hyperplasia.     

Effects of temperature on the development and survival of Nanomia bijuga (Hydrozoa, Siphonophora)

Abstract. The effects of temperature on the development of marine invertebrates have been studied primarily in benthic species. For this study, gametes were collected from Nanomia bijuga , a mesopelagic siphonophore, and were self-crossed. Fertilized eggs kept at 8 and 12°C developed more slowly at the lower temperature. Developing stages were preserved after 2, 4, 6, and 9 days of development for comparative analysis with SEM. Concurrent experiments compared survival. Eggs collected from two additional colonies were placed in four temperature treatments: 4, 8, 12, and 18°C. The young developed normally in all treatments, but survived longer at lower temperatures. Young of N. bijuga will develop to siphonulae possessing tentacles, nematocysts, and a functional gastrozooid without being fed. Nonetheless, it is likely that food constraints, rather than temperature, limited survival in this study.     

Production and survival of eggs of the cattle tick Boophilus microplus (Canestrini) (Acarina: Ixodidae) in the wet and dry tropics of north Queensland

Monthly observations were made on egg production and egg survival of the cattle tick Boophilus microplus , at five sites in northern Queensland from August 1978 to July 1980. Egg production was close to the potential except in the hot, dry season in the drier sites and a model was fitted to explain the data. The main factors that reduced egg production were maximum soil temperature greater than 33.6°C, minimum soil temperature less than 17.6°C, and soil moisture less than 0.26 water-holding capacity when the soil maximum temperature was greater than 37.2°C. The model explains 61% of the variation in egg production from an independent set of data from southern Queensland. Analysis of egg viability at the time of retrieval from pasture indicated that the most important variables reducing viability were maximum soil temperature greater than 25.4°C, minimum soil temperature less than 16.9°C, soil moisture below 0.21 water-holding capacity, the sum of degree-days less than 3.95 per day and stress carried over from the egg production phase.     

Synchronization of larval emergence in winter moth (Operophtera brumata L.) and budburst in pedunculate oak (Quercus robur L.) under simulated climate change

1. The hypothesis that a 3 °C elevation in temperature and doubled CO₂ concentration would have no effect on the synchronization of winter moth egg hatch with budburst in oak was tested by comparing the separate and interactive effects of ambient and elevated (+ 3 °C) temperature and ambient and elevated (doubled to 340 p.p.m.) CO₂ in eight experimental Solardomes. In addition, an outdoor control was compared with the ambient temperature/CO₂ treatment combination.
2. Elevated temperature accelerated darkening (preceding egg hatch by about 5–10 days) and hatching of eggs developing off the trees; elevated CO₂ had no effect. The same effects were observed in eggs developing on the trees.
3. Within treatments, date of egg hatch was the same on trees with early or late budburst.
4. Egg darkening and budburst were closely synchronized at both ambient and elevated temperatures.
5. Both eggs and trees required fewer cumulative heat units (day degrees > 4 °C), for hatching and budburst, respectively, at ambient than elevated temperatures. The requirements in the outdoor control treatment were similar to those in the ambient Solardome treatment.
6. Egg hatch between 10 and 25 °C, on a temperature gradient in the laboratory, required a constant number of heat units; fewer were required below 10 °C.
7. Elevated temperatures, in the Solardomes and the field, delayed adult emergence from the pupae.
8. The results suggest that a general increase in temperature with climatic change would not affect the closeness of the synchronization between egg hatch of winter moth and budburst of oak.     

Spawning of the Australian freshwater fish Murray cod, Maccullochella peeli (Mitchell), in earthen ponds

Murray cod, Maccullochella peeli , spawned naturally in earthen ponds in four consecutive breeding seasons. Spawning was induced by a rise in water temperature up to or above 20°C during spring, however, an associated rise in water level was not required. Response to the temperature rise was more rapid later in the season and increasing daylength may have also been involved. Eggs were deposited on firm substrates at depths between 0·5 and 2·3 m, and hollow pipes, logs or similar structures were not necessary to provide suitable sites for egg deposition. At two spawning sites, mud had been removed from the pond banks by the broodfish and the eggs attached to the exposed clay. At one spawning site, a male cod was observed protecting the eggs during incubation.
It is suggested that high survival of cod larvae will only occur when a significant rise in water level coincides with the breeding season and as a consequence the control of water levels for irrigation and flood mitigation purposes during spring and summer has affected Murray cod to a greater extent than golden perch, Macauaria ambigua , which spawns only after a substantial rise in water level, when conditions are more favourable for larval survival.     

Influence of soil moisture on egg cold hardiness in the migratory locust Locusta migratoria (Orthoptera: Acridiidae)

Abstract.  The present study investigates the influence of environmental moisture on cold hardiness of the migratory locust, Locusta migratoria . The water content of locust eggs kept in soil at 30 °C varies according to the moisture content of the substrate. In turn, it can significantly affect the supercooling point of locust eggs (range from −26 to −14.8 °C) and the mortality when exposed to subzero temperatures. Environmental moisture influences the supercooling capacity of eggs and their survival at low temperature. When locust eggs of the same water content are exposed to subzero temperatures under different soil moistures, their mortality varies between short-time exposure and long-time exposure at subzero temperatures. Given a short-time exposure, mortality in wet soil is lower than in dry soil due to the buffering effect of soil water against temperature change. The pattern of egg mortality is reversed after long-time exposure at low temperature, suggesting that inoculative freezing may be an important mortality factor. It is suggested that interactions between soil moisture and low temperature can influence the cold hardiness of locust eggs, and partial dehydration is beneficial to over-wintering eggs of the migratory locust.