The temperature dependence of embryonic and larval development in Protonemura intricata (Plecoptera: Nemouridae)

SUMMARY. 1. Egg development and larval growth of Protonemura intricata (Ris, 1902) (Plecoptera: Nemouridae) were studied in the laboratory and in the Breitenbach, a small stream-in Germany (F.R.G.). 2. The mean number of eggs in batches collected from the field was 627 (S=314). 3. Mean batching success in the laboratory was 60–100% at 2–18°C. Cumulative hatch in individual batches could be described by asymmetrically sigmoid curves. The length of the hatching period was positively correlated with the length of the incubation period. 4. The incubation period of I', intricata normally consists of an initial dormancy followed by subsequent development. The length of embryonic development (Y. days) is strongly inversely temperature (T, °C) dependent and can be described by the equation: 5. The length of dormancy is dependent on oviposition dale, and is shorter the later that the eggs are laid. It also depends on temperature during incubation and is increased by rising temperatures. As a consequence, larvae hatch more or less synchronously in the field during autumn. Total incubation period, i.e. dormancy and actual development, exhibits a complex dependence on both incubation temperature and oviposition date. Under constant laboratory temperatures, a late sharp fall in temperature can terminate dormancy earlier. 6. Photoperiod probably induces dormancy and may already act on the last larval instars of the parent generation. The dormancy of P. intricata is classified as an oligopause (Müller. 1970, 1976). 7. In the laboratory. P. intricata larvae from early batches with long dormancy grew faster than larvae from late batches with direct development. Final size was the same in both cases. This acted against the population synchrony induced through egg dormancy. Benthos samples suggest the same in the field. 8. Avoidance of the suboptimal summer conditions in streams by the cold stenothermous P. intricata is suggested to partly explain the success of the species, which contributes more to total emergence biomass than do other Plecoptera in the Breitenbach.     

Interspecific variation in temperature dependence of egg development of five congeneric stonefly species (Protonemura Kempny, 1898, Nemouridae,Plecoptera)

Embryonal development of the five congeners Protonemura auberti Illies, 1954, P. hrabei Rauser, 1956, P. meyeri (Pictet, 1841), P. nitida (Stephens, 1835), and P. praecox (Morton, 1894) was studied under various laboratory temperatures and different photoperiods.Mean number of eggs in field collected batches was between 470 (P. praecox) and 1211 (P. auberti). Spring species had smaller egg batches than autumn species (Table 1). Mean hatching success in the laboratory was 50–100% at 2–18 °C. In most species hatching success decreased slightly with increasing temperature (Figs. 1a-e). None of the eggs incubated at 24 °C developed. Hatching pattern followed an asymmetric frequency distribution. In general, the hatching periods were the shorter the higher the incubation temperature.Embryonic development of all five species was inversely temperature dependent (Figs. 2a-e), and well described by a power law relationship (Figs. 3a-e). Interspecific differences in incubation periods were notable at nearly all temperatures (Fig. 4). There was a distinct interspecific sequence in length of incubation period (with steps of about 4 days), which was the same as can be seen in the flight periods: The later the species flies the longer the incubation period. Temperature fluctuations and variations in photoperiod had no influence on incubation and hatching periods or hatching success.The thermal demand of the egg stage neither explains the recent geographical distribution of the Protonemura species, nor does it directly correspond to the field temperatures common during their egg development. However, it is optimal in respect to resource partitioning between the five species, with the consequence of temporal displacement of life cycles.Derived from Brittain's (in press) proposal to compare the two constants a and b of the regressions describing the temperature dependence of embryonal development, a new index (Integral Development Time, IDT) indicating the thermal demand was created for easier comparison of numerous species (Table 2). Evaluation of the IDT for various species of Plecoptera (Fig. 5) suggests that species belonging to the family group Systellognatha generally have higher thermal requirements in the egg stage than species belonging to the Euholognatha.     

Reproductive maturation in the large pine weevil Hylobius abietis: the relative importance of larval and adult diet

1 Larval and adult Hylobius abietis (L.) can feed and, in the case of the adults, cause commercially significant damage to many species of conifer. The present study aimed to evaluate the impact of larval and adult feeding on different host plants on subsequent reproductive fitness. 2 Hylobius abietis larvae were reared on logs of four host species known to vary in suitability for development; Pinus nigra ssp. laricio, Picea sitchensis, Larix kaempferi and Pseudotsuga menziesii. Adult females were collected on emergence and allocated to complete maturation feeding on one of four seedling conifer species, P. nigra spp. laricio, P. sitchensis, P. menziesii and Larix ×marschlinsii. It was assumed that variation in both larval and adult host plant quality had the potential to influence subsequent reproductive behaviour. 3 The time taken for females to attain reproductive maturity was assessed, and reproductive output was measured over an average period of 17 days. 4 The best predictor of the time to attain reproductive maturity was found to be the initial adult body weight. This was strongly related to the larval host species, with the largest adults emerging from P. nigra ssp. laricio. The time taken to begin oviposition was in the range 10–49 days (mean 23 days). The subsequent mean rate of oviposition for individual females was in the range 0.1–3.7 eggs per day. Egg volumes varied between and within individual females, in the range 0.241–1.079 mm³. 5 The species of seedling provided for maturation feeding had no significant impact on reproductive behaviour over the course of the experiment. It is possible, however, that the quality of the adult diet might exert a greater influence on behaviour over a longer period because H. abietis is a relatively long‐lived species.     

Two new species of the stonefly genus Amphinemura (Insecta,Plecoptera, Nemouridae) from China

Two new species of the genus Amphinemura Ris from China are described and illustrated, i.e. A. annulata Du & Ji, sp. n. from Zhejiang, Shanxi, Shaanxi and Guizhou Province, and A. lingulata Du & Wang, sp. n. from Shaanxi and Sichuan Province. A. annulata is similar to A. tricintusidens Wang & Zhu in having an apical cavity of the epiproct, but the epiproct ventral sclerite and the median paraproct lobe of the two species are different. A. lingulata is related to A. didyma Zhu & Yang in having the similar epiproct, but they differ mostly in paraproct median and outer lobes.     

Transgenerational effects of parental larval diet on offspring development time, adult body size and pathogen resistance in Drosophila melanogaster

Environmental conditions experienced by parents are increasingly recognized to affect offspring performance. We set out to investigate the effect of parental larval diet on offspring development time, adult body size and adult resistance to the bacterium Serratia marcescens in Drosophila melanogaster. Flies for the parental generation were raised on either poor or standard diet and then mated in the four possible sex-by-parental diet crosses. Females that were raised on poor food produced larger offspring than females that were raised on standard food. Furthermore, male progeny sired by fathers that were raised on poor food were larger than male progeny sired by males raised on standard food. Development times were shortest for offspring whose one parent (mother or the father) was raised on standard and the other parent on poor food and longest for offspring whose parents both were raised on poor food. No evidence for transgenerational effects of parental diet on offspring disease resistance was found. Although paternal effects have been previously demonstrated in D. melanogaster, no earlier studies have investigated male-mediated transgenerational effects of diet in this species. The results highlight the importance of not only considering the relative contribution each parental sex has on progeny performance but also the combined effects that the two sexes may have on offspring performance.     

The effect of larval competition on development time and adult size in the seaweed fly,Coelopa frigida

Summary The effect of larval competition on adult size and egg to adult development time has been investigated in laboratory populations of the seaweed fly, Coelopa frigida. Increased larval density results in longer development times and smaller adults, suggesting a strong interference element to the competition. This may be due to a limiting rate of food supply rather than interactions between larvae. The relationship between development time and size suggests that both these characters are involved in control of the onset of pupation. C. frigida is polymorphic for an inversion on chromosome I. Differences in relative viability between the karyotypes are not related to the development time or size differences.     

Egg production, larval development, and adult longevity of cat fleas (Siphonaptera: Pulicidae) exposed to ultrasound

Adult cat fleas, Ctenocephalides felis felis (Bouché), on cats (Felis catus) were exposed to emissions from an ultrasonic flea collar worn by the cat. No significant differences were found in total numbers of eggs produced per day (mean = 524 control, 614 treatment), in length of larval development time (mean = 7.7 d control, 7.7 d treatment), or in total daily pupal production (mean = 485 control, 445 treatment) between the treatment and the control groups. Tests off the host were conducted to determine whether ultrasonic exposure caused mortality in adult fleas; no significant differences were found in daily mortality between the treated and control fleas during 1 wk of exposure.     

Effects of attachment substrate,larval diet,and temperature on development and survival of immature Coquillettidia linealis (Skuse) and Coquillettidia xanthogaster (Edwards)

A sustainable colony allowed investigations into attachment substrates, diet and temperature in the development of the immature stages of Cq. linealis and its local congener Cq. xanthogaster. As immatures, these mosquitoes attach to submerged plants for respiration, and various field‐collected and laboratory‐raised plants were compared with non‐living substrates. Hydroponically‐grown wheat plant seedlings provided the most suitable attachment substrate. Development and survival of immatures to eclosion were investigated with three types and three quantities of a standardized diet. Development and survival at rearing temperatures between 10° and 30° C were also investigated. Diet type appeared to have little influence on development. However, at the lowest diet quantity, development to pupation was significantly reduced while the highest diet quantity impacted on the eclosion of pupae. Mean duration of immature development for Cq. linealis increased as temperature decreased. Time from 1^st instar to median eclosion did not differ significantly between 23° C (6.0 weeks) and 25° C (5.3 weeks), although it was 10 weeks at 20° C, and 30° C was lethal. For Cq. xanthogaster, similarly, mean duration of immature development increased as temperature decreased, with development time from 1^st instar to median eclosion significantly longer at 20° C (7.5 weeks) compared to 23° C (5.0 weeks) and 30° C (4.0 weeks).     

Effect of rearing temperature and larval density on larval survival, age at pupation and adult size of Anopheles gambiae

The effects of temperature and larval density on survival of larvae, growth rate, age at pupation, and adult size (measured as wing length and dry weight) of laboratory-reared Anopheles gambiae (Diptera: Culicidae) were studied. Larvae were reared at three temperatures (24, 27 and 30°C) and three densities (0.5, 1 and 2 larvae/cm²). The effects of density and temperature strongly interacted to determine the mosquitoes' life-history parameters. Survival was highest at the intermediate temperature of 27°C. The differences between the temperatures increased with increasing density. At 30°C survival decreased as density increased, but at 27°C increasing density led to higher survival. Age at pupation increased as temperature decreased from 30°C to 24°C and as density decreased from 2 to 0.5 larvae/cm². Adult size also increased as temperature decreased, but showed a negative correlation with density only at 27°C. In contrast, at 24°C and 30°C a decrease in density led to a decrease in adult size. Growth rate showed a similar pattern. At 27°C growth rate decreased as density increased, but at other temperatures the opposite trend was observed.     

The Group of Amphinemura flavostigma (Plecoptera,Nemouridae)

Three closely related species from Japan are treated and defined as composing the Amphinemura flavostigma group (Okamoto, 1922). One species, A. nikkoensis, is described as new to science. Two already known species, A. flavostigma and A. monotuberculata (Kawai, 1956), are redescribed, while the female of the latter is described for the first time. Another species, A. tetraspinosa Kawai, 1960, is regarded as a subjective synonym of Nemoura flavostigma Okamoto, 1922.     

Spatial and temporal variation in the diet of a predaceous stonefly (Plecoptera: Perlodidae)

SUMMARY. 1. Spatial and temporal variation in the diet of the univoltine predatory stonefly, Kogotus nonus , was studied over 3 years in a small Alberta stream to determine whether the relative abundance of prey types in the diet of Kogotus reflected relative prey densities in the stream and whether the variation in absolute feeding rate was related to either prey or predator density.
2. The seasonal shift from sole utilization of Orthocladiinae to inclusion of Baetis in the diet could not be attributed to seasonal changes in prey density, but was probably related to predator size and ability to handle very active prey. Most of the spatial variation in diet could be related to differences in background prey densities, but very high densities of Baetis caused the predator to specialize on this prey.
3. Feeding rate on Baetis . as assessed by per capita gut contents, showed a seasonal shift from a positive correlation with Baetis density in winter to a negative relationship with predator density in spring. This suggested that feeding by small Kogotus is a function of prey density. while feeding by later instars is influenced by between predator interactions such as interference.     

The effect of salinity and temperature on the larval development of clibanarius vittatus (Bosc) (crustacea: decapoda: diogenidae)

Clibanarius vitatus (Bosc) larvae were reared in twenty combinations of four salinities (15, 20, 25, and 30%) and five temperatures (15, 20, 25, 30 and 35%°C). No development was observed in any salinity at 15°C, but partial development occurred in all other test conditions. Metamorphosis to juvenile crabs was noted only at salinities of 25 and 30A% in combination with temperatures of 25 and 30°C. In general, development times were decreased at higher temperatures; no trend was evidence for salinity. Mortality of zoeae was usually highest at the time of the first molt and greatest overall mortality occurred during the megalopa stage prior to metamorphosis. Previous experiments (unpubl.) have shown that C. vittatus adults can tolerate temperature down to 5°C. It is suggested that geographic distribution of C. vittatus (Virginia, southward) is limited not by adult tolerances but by the inability iof the species to establish a breeding population. Larvae require two months at 25°C or above to metamorphose, and this condition is not met in areas north of Virginia.     

The relative importance of size and asymmetry in sexual selection

Developmental stability reflects the ability of individualsto cope with their environment during ontogeny given their geneticbackground. An inability to cope with environmental and geneticperturbations is reflected in elevated levels of fluctuatingasymmetry and other measures of developmental instability. Bothtrait size and symmetry have been implicated as playing an importantrole in sexual selection, although their relative importancehas never been assessed. We collected information on the relationshipbetween success in sexual competition and size and asymmetry,respectively, to assess the relative importance of these twofactors in sexual selection. Studies that allowed comparisonof the relationships for the same traits' size and symmetryand success in sexual competition constituted the data, whichtotaled 73 samples from 33 studies of 29 species. The averagesample-size weighted correlation coefficients between matingsuccess or attractiveness and size and asymmetry, respectively,were used as measures of effect size in a meta-anatysis. Analysiswas conducted on samples, studies, and species separately. Wefound evidence of an overall larger effect of symmetry at thespecies level of analysis, but similar effects at the sampleor study levels. The difference in effect size for charactersize and character symmetry was larger for secondary sexualcharacters than for ordinary morphological characters at thelevel of analysis of samples. The results lend support to theconclusion that symmetry plays an important general role insexual selection, especially symmetry of secondary sexual characters.     

Growth of larval and juvenile perch: the importance of diet and fish density

In August, growth rate of young–of–the–year (YOY) Perch In lake enclosures could be explained by both YOY density and mean cladoceran biomass, suggesting that in a lake where YOY perch are dominant, growth may be density dependent in late summer and mediated through top–down control on daphnid biomass. In June, growth rate of YOY perch could not be fully explained by YOY density or by mean cladoceran biomass, suggesting that growth and survival during the first part of the summer is negatively affected by a diet of Bosmina and cyclopoid copepods only. The experiments also suggest why YOY perch have a slow growth and a low abundance in eutrophic lakes where small zooplankton dominate. The June experiment also indicated that growth of late larval or early juvenile perch improved when a larger cladoceran became available and was included in the diet.     

The larval diet of three anisopteran (Odonata) species

SUMMARY.

• 1 Comparisons between larval diets of three anisopteran species (Anax imperator, Aeshna cyanea and Libellula depressa) showed that their food intake changed depending on: (1) predator species, (2) time of year, and (3) developmental stage.
• 2 Although this last factor is not so important, the mean size of prey items and the range of prey species eaten by Auax imperator and Aeshna cyanea larvae increased with predator size.
• 3 Comparisons between prey availability and diets indicated differential selectivity by these predators.

     

Effect of four chlorophytes on larval survival, development and adult body size of the mosquito Aedes aegypti

The effect of four microalgal chlorophytes, Chlorella vulgaris,Scenedesmus quadricauda, Chlorococcum sp. and Ankistrodesmus convolutus, on the survival, larval development and adultbody size of the mosquito Aedes aegypti was investigated. The percentage mortality of larvae fed with C. vulgaris, Chlorococcum sp.or S. quadricauda after six days was 100%, 84% and 88%,respectively. Delayed pupation and body size reduction of the mosquitoesfed with C. vulgaris, Chlorococcum sp. and S. quadricaudawere observed. In contrast, larvae fed with A. convolutus werebigger than those fed with normal insectory feed. The study showed thatC. vulgaris, S. quadricauda and Chlorococcum sp. have potentialto be used as larvicidal agents.     

Effect of larval diet on cat flea (Siphonaptera: Pulicidae) developmental times and adult emergence.

The natural diet of cat flea, Ctenocephalides felis (Bouche), larvae is primarily adult flea feces, but dried bovine blood may be substituted in the laboratory. Percentage adult emergence (79.4% on feces; 78.9% on blood) and developmental times (20.6 d on feces; 17.1 d on blood) did not significantly differ for the two diets. The drying temperature of blood determined its quality; blood dried at 120 degrees C was unsatisfactory for larval development. The dietary value of dried bovine blood was not enhanced when supplemented with brewer's yeast, rodent chow, or a combination of those constituents. Blood particle size ranging from less than 180 to greater than 500u did not affect the value of blood as a diet. Rodent chow, yeast, albumen, hemoglobin, and mixtures of these constituents were unsuitable as larval diets.     

The effects of diet on plasma and yolk steroids in lizards (Anolis carolinensis)

Steroids present in egg yolk have been shown to vary as a resultof numerous social and environmental influences and to produceboth positive and negative phenotypic outcomes in offspring.In the present study, we examined how quality of the diet affectsplasma and yolk steroids in the green anole (Anolis carolinensis),a lizard species with genotypic sex determination. We documentedthe effects of body condition on plasma testosterone (T) andcorticosterone (CORT)—steroids with frequently opposingeffects—in breeding females and on the T and CORT contentof their eggs. We chose to manipulate body condition via dietbecause resource availability is a relevant, fluctuating variablein the environment to which females can be expected to respond.Field-collected females were housed in the laboratory and kepton either a reduced, standard, or enhanced diet (differing innutritional quality and/or quantity) for ten weeks. Althoughfemales did not differ in body condition at the beginning ofthe study, we found these diet regimes effective in producingfemales that differed in condition by the end of the study.Females on diets of enhanced quality were in better condition,produced more, but not heavier, eggs, and had higher plasmaT concentrations than did females on a standard diet or oneof reduced quality. There was also a significant positive relationshipbetween laying sequence of eggs and yolk T for females on dietsof enhanced quality, but not for the females on diets of standardor reduced quality. There were no effects of quality of dieton CORT in plasma or yolk, but yolk T and yolk CORT exhibiteda strong positive correlation irrespective of treatment. Femaleson diets of reduced quality did not differ from females on standarddiets either with respect to reproductive output or to endocrineprofiles, in spite of being in worse body condition. These resultsdemonstrate that females’ body condition, physiology,and reproductive output can be manipulated by quality of diet,and that changes in deposition of yolk steroids in responseto diet may be minimal.