Sexual size dimorphism in the ontogeny of the solitary predatory wasp Symmorphus allobrogus (Hymenoptera: Vespidae)

Sex-specific patterns of individual growth, resulting in sexual size dimorphism (SSD), are a little studied aspect of the ontogeny related to the evolutionary history and affected by the ecology of a species. We used empirical data on the development of the predatory wasp Symmorphus allobrogus (Hymenoptera, Vespidae) to test the hypotheses that sexual differences of growth resulting in the female-biased SSD embrace the difference in (1) the egg size and the starting size of larva, (2) the larval development duration, and (3) the larval growth rate. We found that eggs developing into males and females have significant differences in size. There was no significant difference between the sexes in the duration of larval development. The relative growth rate and the food assimilation efficiency of female larvae were significantly higher than compared to those of male larvae. Thus, the SSD of S. allobrogus is mediated mainly by sexual differences in egg size and larval growth rate.     

Factors determining the average body size of geographically separated Arctodiaptomus salinus(Daday,1885) populations

Arctodiaptomus salinus inhabits water bodies across Eurasia and North Africa.Based on our own data and that from the literature,we analyzed the influences of several factors on the intra-and inter-population variability of this species.A strong negative linear correlation between temperature and average body size in the Crimean and African populations was found,in which the parameters might be influenced by salinity.Meanwhile,a significant negative correlation between female body size and the altitude of habitats was found by comparing body size in populations from different regions.Individuals from environments with highly varying abiotic parameters,e.g.temporary reservoirs,had a larger body size than individuals from permanent water bodies.The changes in average body mass in populations were at 11.4 times,whereas,those in individual metabolic activities were at 6.2 times.Moreover,two size groups of A.salinus in the Crimean and the Siberian lakes were observed.The ratio of female length to male length fluctuated between 1.02 and 1.30.The average size of A.salinus in populations and its variations were determined by both genetic and environmental factors.However,the parities of these factors were unequal in either spatial or temporal scales.     

Seasonal and geographic variation in thermal biology of the lizard Microlophus atacamensis (Squamata: Tropiduridae)

1.

We studied physiological thermal adaptation in the lizard Microlophus atacamensis along a latitudinal range.     

Thermal ecology of five Cnemidophorus species (Squamata: Teiidae) in east coast of Brazil

In this study we compared the body temperature of 16 populations belonging to five species of the genus Cnemidophorus from restinga habitats along the eastern coast of Brazil in order to evaluate the importance of how some environmental factors affect lizard body temperatures. Cloacal body temperatures (T_b) were taken immediately after capture with a quick-reading thermometer (Schultheis). Substrate temperatures (T_s) and air temperatures (T_a; approximately 1 cm above the substrate) were taken as close as possible to the point when each lizard was initially sighted. Most of the mean body temperatures in activity of the different populations and species of Cnemidophorus along the coast of Brazil ranged from 36.5 to 39.3 °C, except for Cnemidophorus lacertoides (T_b=35.2 °C) in the restinga of Joaquina, SC and for Cnemidophorus ocellifer (T_b=34.8 °C ) in the restinga of Praia do Porto, SE. Some studies show that the body temperature of lizards is more related to phylogenetic than ecological factors, suggesting that species of the same genus tend to have similar body temperatures even occurring in different types of environments. In general, regardless of the locality and latitude along the eastern coast of Brazil, the different species of lizards of the genus Cnemidophorus and their respective populations have similar body temperatures in activity and the apparent differences result from the influence of the local thermal environment of each restinga.     

Fish predation on Eudiaptomus gracilis in relation to clutch size,body size,and sex: a field experiment

An enclosure experiment was performed to test for direct predationeffects on fecundity and adult body size of the copepod Eudiaptomus gracilis in the field. By introducing a high densityof fish (15 underyearling roach, Rutilus rutilus, per 350litre enclosure) and documenting the short-term effects on traitsin a rapidly decreasing prey population, responses to changes inthe phytoplankton community were minimized. After 68 hours ofpredation, clutch size and frequency of females carrying eggs weresignificantly lower in fish enclosures. Female density was moreaffected than male density. Predation selected against large bodysize in both sexes but less so in females, leading to an increasedsexual size dimorphism. The results agree with predictions based onprey selectivity in fish. Predation risk should increase withclutch size and body size since these traits increase theconspicuousness of prey. The size of the highly visible egg-clutchmay be more important than body size. Female body size wasuncorrelated to clutch size, which may explain the weaker sizeeffect among females and the changed sexual sizedimorphism.     

Thermal relations of dwarf caiman, Paleosuchus palpebrosus, in a hillside stream: Evidence for an unusual thermal niche among crocodilians

Body temperatures of 13 Paleosuchus palpebrosus, 7 males and 6 females, were monitored by radio-telemetry during cold periods (dry season) and warm periods (wet and dry seasons) in a stream draining into the Brazilian Pantanal. The mass of the caimans varied from 2.5 to 20.0 kg, and snout–vent length from 47.5 to 95.0 cm. Mean monthly body temperature was 21.6 °C, and varied from 20.1 to 25.6 °C throughout the year. Body temperature was correlated with air and water temperature but did not differ between males and females. Unlike all other crocodilians investigated in detail to date, the caimans did not show evidence of attempts to obtain higher body temperatures when ambient temperatures were low, and had low and generally constant temperatures in relation to the surrounding air and water throughout the year. The caimans remained in burrows during cold periods in the dry season, which may explain why they did not seek higher temperatures. Tolerance of relatively low and constant body temperatures may be a key adaptation of species of Paleosuchus, allowing them to occupy environments inhospitable to other crocodilians.     

中华花龟幼体热耐受性、体温昼夜变化和运动表现的热依赖性

为研究中华花龟(Ocadia sinensis)幼体的热耐受性和运动表现热依赖性，设计了具有和缺乏温度梯度两种热环境，研究幼龟体温的昼夜变化。高、低温耐受性分别用临界高温和临界低温表示，体温为泄殖腔温度，水温和气温分别是幼龟所处位置的水温和1cm高气温。临界高温和临界低温分别为41．9℃和1．8℃。在有温度梯度的热环境中，体温、水温和气温平均值有显著的昼夜差异，水温和体温的日平均值无显著差异，两者均大于气温的日平均值。在缺乏温度梯度的热环境中，体温、气温和水温平均值亦有显著的昼夜差异，但气温、水温和体温的日平均温度无显著差异。温度梯度是幼龟进行体温调节不可或缺的条件，选择体温有显著的昼夜变化，最大值和最小值分别为29．2℃和25．4℃。在02：00—06：00时间段内，幼龟选择体温明显较低，其它测定时刻的选择体温无显著差异。幼龟各测定时刻的平均体温与平均气温和水温均呈正相关。处于温度梯度中幼龟特定气温的体温比处于缺乏温度梯度中的幼龟高3．7℃，这种差异是前者利用温度梯度进行体温调节的结果；处于不同热环境中幼龟特定水温的体温无显著差异。体温显著影响幼龟的运动表现。18—39℃体温范围内，疾跑速随体温增加而增加，36℃和39℃体温的幼龟疾跑速最大；体温达到41℃时，疾跑速显著下降。体温较高的幼龟的最大持续运动距离大于体温较低的幼龟。偏相关分析显示，疾跑速与最大持续运动距离和停顿次数呈显著的正相关，停顿次数与最大持续运动距离呈负相关。     

A laboratory study on the thermal tolerance of four southeastern stream insect species (Trichoptera,Ephemeroptera)

The acute thermal tolerances of four southeastern stream insect species, Ephemerella invaria (Walker), Stenonema ithaca (Clemens and Leonard), Symphitopsyche morosa (Hagun), and Brachycentrus lateralis (Say) were determined using an artificial stream enclosure. All species were acclimated at 10°C for 72 hours prior to instantaneous immersion into heated water for 96 hours. Percent mortality was recorded and the temperature at which 50% mortality occurred determined (LT5o). Data were subjected to standard statistical analysis.Thermal tolerance values were compared between species tested and to results from previous investigations using similar methodologies. The evolution and life histories of these species were also discussed in relation to their thermal tolerance values.     

Aspects of the thermal biology of the six-lined racerunner, Cnemidophorus sexlineatus (Squamata:Teiidae) in West-Central Florida

(1) I measured the critical thermal maximum (CTM_ax), mean selected temperature (MST), and mean activity temperature (MAT) of six-lined racerunners, (Cnemidophorus sexlineatus) from Florida. (2) Mean CTM_ax and MST of Florida lizards (n=10) were 48.2±0.6 and 33.5±1.9^oC, respectively. MAT (n=22) at 36.6^oC was statistically higher than MST. (3) CTM_ax, MST, and MAT of Florida lizards were statistically lower than those published for a conspecific Oklahoma population.     

Body size and its consequences: Allometry and the lower limb length of Liang Bua 1 (Homo floresiensis)

Bivariate femoral length allometry in recent humans, Pan, and Gorilla is investigated with special reference to the diminutive Liang Bua (LB) 1 specimen (the holotype of Homo floresiensis) and six early Pleistocene femora referred to the genus Homo. Relative to predicted body mass, Pan and Gorilla femora show strong negative length allometry while recent human femora evince isometry to positive allometry, depending on sample composition and line-fitting technique employed. The allometric trajectories of Pan and Homo show convergence near the small body size range of LB 1, such that LB 1 manifests a low percentage deviation (d_yx of Smith [1980]) from the Pan allometric trajectory and falls well within the 95% confidence limits around the Pan individuals (but also outside the 95% confidence limits for recent Homo). In contrast, the six early Pleistocene Homo femora, belonging to larger individuals, show much greater d_yx values from both Pan and Gorilla and fall well above the 95% confidence limits for these taxa. All but one of these Pleistocene Homo specimens falls within the 95% confidence limits of the recent human sample. Similar results are obtained when femoral length is regressed on femoral head diameter in unlogged bivariate space. Regardless of the ultimate taxonomic status of LB 1, these findings are consistent with a prediction made by us (Franciscus and Holliday, 1992) that hominins in the small body size range of A.L. 288-1 (“Lucy”), including members of the genus Homo, will tend to possess short, ape-like lower limbs as a function of body size scaling.     

Food habits and the evolution of energetics in birds of paradise (Paradisaeidae)

Basal rates of metabolism, minimal thermal conductances, and body temperatures are reported for 13 species of birds of paradise that belong to nine genera. Body mass alone accounts for 91.7% of the variation in their basal rates. Basal rate in this family also correlates with food habits and the altitudinal limits to distribution. Species that feed almost exclusively on fruit have basal rates that average 79.4% of species in which >10% of the diet is insects, and species restricted to altitudes <1,000 m have basal rates that are 90.6% of those found at higher altitudes. The combination of body mass, food habits, and altitudinal distribution accounts for 99.0% of the variation in basal rate in the species studied. The application of food habits to a cladogram of the studied Paradisaeidae implies that frugivory and low basal rate were plesiomorphic in this family. The evolution of omnivory, defined as including >10% of the diet as insects, appears to have occurred at least twice, and in each case was associated with an increase in basal rate of metabolism. Basal rate increased at least thrice with a movement into the highlands. Basal rate, however, does not correlate with plumage dimorphism or with reproductive behavior. The basal rates of metabolism in manakins and birds of paradise, i.e., passerine frugivores, are greater than those found in nonpasserine frugivores. Thermal conductance correlates with body mass, which accounts for 85.8% of its variation in this family. Body temperature in paradisaeids, the mean of which was 40.2°C, may correlate with basal rate of metabolism.     

Effect of age and body size on selected temperature by juvenile wood turtles (Glyptemys insculpta)

In an aquatic thermal gradient of 15–30 °C, 3-, 6-, and 12-month-old juvenile wood turtles (Glyptemys insculpta) acclimated to 20 °C selected the warmest temperature available (30 °C) and avoided the coldest temperatures available (15 and 18 °C). Mean selection of chambers differed between control and gradient tests across all temperatures except 27 °C. Turtles of all age classes relocated between chambers less often when the gradient was present than during control tests. Six- and 12-month-old turtles selected 30 °C more frequently, and selected colder temperatures less frequently, than 3-month-old turtles, suggesting that the ability to select preferred temperatures is better developed in older hatchlings.     

Thermal responses to feeding in a secretive and specialized predator (Gila monster, Heloderma suspectum)

We investigate how a unique dietary specialist, the Gila monster (Heloderma suspectum), uses behavioral thermoregulation to elevate body temperature (T_b) after feeding. Lizards in a laboratory thermal gradient were fed rodent meals of three different sizes (5, 10, or 20% of body mass), or sham fed (meal of 0% body mass), and T_bs were recorded for three days before feeding and seven days after feeding. Gila monsters selected a mean T_b of 25.2 °C while fasting (set-point range 23.6–27.1), and increased T_bs after feeding. The magnitude and duration of post-prandial T_b increases are positively related to meal size, and Gila monsters selected mean T_bs up to 3.0 °C higher and maintain elevated T_bs for 3–6 days after feeding. Selection of T_b does not appear to differ between day and night time periods, and because the lizards are both diurnal and nocturnal (at different times of year), photoperiod may not be an important influence on T_b selection.     

Development of successive cambia and pattern of secondary growth in the stem of the Neotropical liana Rhynchosia phaseoloides (SW.) DC. (Fabaceae)

The occurrence of flattened stems in Rhynchosia phaseoloides (SW.) DC. (Fabaceae) has been known for years, but little interest has been shown toward elucidating its secondary growth. This study aims to (1) understand the pattern of secondary growth and development of vascular elements from the cambium at different stages of stem growth and (2) elucidate the type, size and distribution of cells related to these processes at different regions of the stem. Dilatation growth in main stems and branches of R. phaseoloides is achieved by successive cambia formed in two areas of the actual cortex that are opposed to each other by approximately 180°. Only the first cambial ring is functionally normal and closed-elliptical in outline, supporting the growth of the middle part of the rather flat stem. Later on, this stem becomes oval to oblong in cross-section outline by the activity of successive cambia from which cells produce further xylem, phloem and parenchyma tissues in a somewhat fan-shaped way. As shown in cross section, a flat cable-like structure of several modules results, forming wings relative to the primary central axis tissues. The secondary cambia are formed by dedifferentiation of cortical parenchyma cells, resulting in small clusters of radially arranged meristematic bands of cells. From these meristematic bands, an outward-facing crescent-shaped new band of cambium is originated. The innermost cells of this meristematic band form the parenchymatic tissue that connects the new lateral module to the proximal one. This occurs several times during the whole stem ontogeny.     

Change in the thermal biology of tadpoles of Odontophrynus occidentalis from the Monte desert, Argentina: Responses to photoperiod

We determined if the photoperiod regime affects the thermal biology of the tadpoles of Odontophrynus occidentalis from the Monte desert (Argentina). Variables measured were: selected body temperature (T_sel), critical thermal maximum (CT_max) and thermal critical minimum (CT_min). The tadpoles were acclimated to 15±2 °C for 15 days, and they were divided in three experimental groups: 24 h light, 24 h dark and 12 h/12 h light/dark. Data indicate that the photoperiod had an important effect upon the thermal biology of the Odontophrynus occidentalis tadpoles. The treatment group exposed to 24 h of light showed the highest selected temperature and thermal extremes. We suggest that changes in photoperiod may allow these organisms to anticipate the future changes in their thermal environment, as longer days usually involve higher temperatures.     

Effects of wing polyphenism, aphid genotype and host plant chemistry on energy metabolism of the grain aphid, Sitobion avenae

Wing dimorphism has been proposed as a strategy to face trade-offs between flight capability and fecundity. In aphids, individuals with functional wings have slower development and lower fecundity compared with wingless individuals. However, differential maintenance costs between winged and wingless aphids have not been deeply investigated. In the current study, we studied the combined effect of wing dimorphism with the effects of aphid genotypes and of wheat hosts having different levels of chemical defences (hydroxamic acids, Hx) on adult body mass and standard metabolic rates (SMR) of winged and wingless morphs of the grain aphid, Sitobion avenae. We found that wingless aphids had higher body mass than winged aphids and that body mass also increased towards host with high Hx levels. Furthermore, winged aphids showed a plastic SMR in terms of Hx levels, whereas wingless aphids displayed a rigid reaction norm (significant interaction between morph condition and wheat host). These findings suggest that winged aphids have reduced adult size compared to wingless aphids, likely due to costs associated to the development of flight structure in early-life stages. These costs contrast with the absence of detectable metabolic costs related to fuelling and maintenance of the flight apparatus in adults.     

The effect of body coloration and group size on social partner preferences in female fighting fish (Betta splendens)

Females of the fighting fish Betta splendens have been shown to associate with other B. splendens females in a manner reminiscent of shoaling behavior. Since body coloration varies dramatically in this species, and since body coloration has been shown to affect shoalmate choice in other species of fish, we examined the influence of body coloration on association preferences in female B. splendens. In dichotomous choice tests, B. splendens females spent more time swimming near groups of females (regardless of coloration) than swimming near an empty chamber, and chose to swim near fish of similar coloration to their own when choosing between two distinctly colored groups of females. When examining the interplay between body coloration and group size, focal fish spent more time swimming near larger groups (N = 5) of similarly colored fish than swimming near an individual female of similar coloration. However, focal fish showed no preference when presented with an individual female of similar coloration and a larger group of females of dissimilar coloration. These results suggest that association choices in B. splendens females are strongly affected by both body coloration and by group size.     

Spinning behaviour and morphology of the spinning glands in male and female Aposthonia ceylonica (Enderlein, 1912) (Embioptera: Oligotomidae)

Embioptera (webspinners) are unique among insects in that juvenile and adults of both sexes spin silk. They possess spinning apparatuses in the basitarsomeres of their prothoracic legs, which they use to build galleries as habitat and protection. Embioptera are primitively social and cooperate in building the galleries. They also show sexual dimorphism that comprises modifications of the mandibles in males, the winglessness of the females and differences in the morphology of the forelegs. In the present investigation we address the correlation of spinning behaviour and sexual dimorphism in the spinning apparatus of Aposthonia ceylonica (Enderlein, 1912). To analyse spinning behaviour we conducted video observations of Ap. ceylonica in artificial habitats. We observed females and males alone as well as female-male pairs to cover possible effects of interactions between sexes. The morphology of the spinning apparatus was analysed and reconstructed using high resolution X-ray computed tomography (SRμCT). The observations show that during trials of 24 h adult males and females produce similar amounts of silk per body weight, despite the fact that adult males do not feed, perhaps due to modifications of their mandibles related to courtship that interfere with feeding. Spinning glands in males are distinctly smaller than in females in absolute values, which reflect the general size difference in females and males. Despite their smaller body size, the volumes of reservoirs of spinning glands are larger in males in relative as well as in absolute values. Together with spinning behaviour and the amount of silk production, this indicates that males produce and store gland secretions in the large reservoirs prior to their final moult for later use.     

Aspects of comparative thermal ecology of sympatric hinge-back tortoises (Kinixys homeana and Kinixys erosa) in the Niger Delta, southern Nigeria

Aspects of the thermal ecology of two sympatric hinge‐back tortoises, Kinixys erosa and Kinixys homeana, were studied in the rainforest zone of south‐eastern Nigeria (West Africa). There were no significant differences in mean body temperatures (T_b) among K. homeana males, K. homeana females, K. erosa males and K. erosa females. In both species, there was a significant correlation between T_b and air temperature (T_a), and the regression line of T_a plotted against T_b differed significantly from the line of ideal poikilothermy. These regressions did not differ significantly between sexes in either species. There were no significant differences in terms of mean T_b in K. homeana during the various day‐hour intervals, whereas the mean T_b of K. erosa varied significantly among the various daytime intervals, attaining the higher values at 11.01–15.00 and 15.01–19.00 hours. In both species, T_bs were nearly always below T_as, and the negative difference ‘T_b ‐ T_a’ increased with increasing T_a. The hourly‐time course of the difference between T_b and T_a showed significant differences in K. homeana (with the higher negative differences at 11.01–15.00 and 15.01–19.00 hours), whereas no such difference was observed in K. erosa. In general, tortoises of both species showed behavioural thermoregulation in their avoidance of overheating in tropical environments, taking advantage of shady forest environments.