Age determination in the adult screwworm (Diptera: Calliphoridae) by pteridine levels

Fluorescence spectrophotometry was used to assess the possible use of pteridines in the compound eyes to estimate the age of adult screwworms, Cochliomyia hominivorax (Coquerel). Factors affecting the quantities of pteridines include temperature and head size. No difference in pteridine levels was found among flies fed protein or carbohydrate. A regression model for estimating the age of female screwworms was constructed. The model uses head capsule size and relative pteridine quantities and assumes a constant body temperature of 30 degrees C. This regression formula has an r2 of 0.74. Our study extends the use of pteridine accumulation for age determination from obligate sanguinivorous Diptera to an autogenous species that feeds facultatively on nectar and wound exudates. The technique appears to provide a valid means to determine age of these flies.     

Spatial and temporal variation in flight morphology in the butterfly Melitaea cinxia (Lepidoptera: Nymphalidae)

Some studies on insects have found a relationship between habitat structure and investment in dispersal-related traits. In this study we compared the morphology of the butterfly Melitaea cinxia from five sites on the large Baltic island Öland that differed markedly in degree of fragmentation and size. Both wild-caught adults and individuals reared in a split-plot design were compared. We found significant site differences in size-adjusted thorax mass and total body mass. Male thorax mass was on average larger among the sites with the highest degree of habitat fragmentation. However, due to significant sex–site interactions, males and females may have adapted differently to the habitat fragmentation. Using museum specimens, we also analysed changes in morphology, finding an increase in size (measured as head and thorax width) over time. Thorax width appears to have increased among females and decreased among males. Possible explanations include increasing fragmentation of the landscape and changes in population density.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 445–453.     

Early Activity Rates do not Predict Growth and Future Body Size of Juvenile Eastern Fence Lizards,Sceloporus undulatus

Selection favors larger body size in many taxa. In some species, larger individuals are more active and bolder than smaller conspecifics, but the nature of this relationship is unclear: Is body size a predictor or a consequence of behavior? Any effect of behavior on body size may be through its effect on competitive ability, suggesting that the presence of potential competitors could exaggerate or suppress this relationship. In this study, we tested whether an individual's activity rates early in life predict its future body size by measuring same‐aged, sibling eastern fence lizards before (8 d) and after (8 wk) they significantly diverged in body size. We tested for an effect of conspecific presence (potential competition) on the relationship between early behavior and future body size by housing some lizards in sibling groups and others individually, using a split‐clutch design. Our results reveal that individuals' activity rates do not significantly differ between 8 d and 8 wk of age. At 8 wk (but not 8 d) of age, more active siblings were also larger in both housing treatments; however, early activity rates did not predict body size later in development for either of these groups. Conversely, body size at hatching did predict size at 8 wk. Although variation in activity rates exists prior to divergence in body size, and activity and body size are correlated later in development, our results suggest that higher activity rates are unlikely to be driving body size divergence in this species. Instead, very small differences in body size at hatching appear to be compounded over time and drive much more exaggerated differences in later body size.     

Effects of size on Vervet (Cercopithecus aethiops) gait parameters: A cross-sectional approach

A comparison of the values of certain temporal and spatial locomotor parameters was made among ten different-aged (sized) vervet monkeys locomoting at nine identical speeds. Cycle and stance durations decreased across speed for all the animals; at any one speed both parameters also varied directly with body size. Stride length increased with speed for all the animals and was greater in the larger animals. Swing duration and hindlimb support length tended to be relatively consistent for each animal across speed, but varied among the animals directly with body size. Hindlimb duty factor decreased with speed for any one animal but showed no direct correlation with size. Hindlimb angular excursion also showed no correlation with size, nor did it show a simple relationship with speed. In terms of gaits and gait transitions, the data indicate that vervets use a very wide variety of gait types, which are not easily correlated with speed or body size. Furthermore, the data suggest the existence of a run–gallop transition zone of speeds for these animals, rather than the existence of a specific transition speed. Finally, the data were used to test intraspecifically the elastic and dynamic similarity models, both of which predict how locomotor parameters will change with size in animals. The results are generally consistent with the dynamic model.     

The relationship of egg size and incubation temperature to embryonic development time in univoltine and multivoltine aquatic insects

1. We used published data to investigate the combined influence of egg size and incubation temperature on embryonic development time for a broad assortment of aquatic insects at four different incubation temperatures (10, 15, 20 and 25 °C).
2. Embryonic development time (EDT) was positively correlated with egg size at each of the four temperatures, but with different relationships for univoltine and multivoltine aquatic insects. The relationships of embryonic development time to egg size expressed in degree-days did not significantly differ in slope ( P >0.50) or intercept ( P >0.05) for either univoltine or multivoltine aquatic insects at each of the four temperatures.
3. The relationship of embryonic development time (degree-days) to egg mass in multivoltine aquatic insects (EDT=885×0.19, P <0.0001, r 2=0.48) is similar in slope and intercept to that for other oviparous animals (i.e., zooplankton, fish, amphibians and reptiles), and to the relationship of embryonic development time to neonate mass in mammals. Univoltine species on average require 3–5 times longer to develop (EDT=14190×0.29, P <0.001, r 2=0.29) than most other animals of equivalent egg mass, but the relationship of embryonic development time to egg mass is similar in slope to that of most other animals. Together, these relationships provide a basis for evaluating differences in embryonic development time among aquatic insects.     

The effect of a seasonal time constraint on development time, body size, condition, and morph determination in the horned beetle Allomyrina dichotoma L. (Coleoptera: Scarabaeidae)

Abstract.  1. In horned beetles selection favours males that adjust their investment in horn development in relation to cues that predict adult body size. Here it is shown that in the Japanese horned beetle, Allomyrina dichotoma . There is a significant discontinuity in the horn length body size allometry. This can be described as a linear relationship that is shifted towards an increased horn length to body length ratio in males with horns longer than 16 mm.
2. Larval nutrition explains morph determination in A. dichotoma . However, unlike other species, variation in larval nutrition was the result of a seasonal time constraint that limits the time available for feeding prior to the onset of winter diapause.
3. Even when eggs were reared with an ad libitum food supply, minor morphs were still observed. Individuals that were oviposited later in the season had less time to feed, shorter development times, eclosed as smaller individuals and, in the case of males, were more likely to be hornless. Major morphs, minor morphs, and females all reduced their body size in response to seasonal time constraints in the same way. However, males that were laid later in the season had faster development times than females laid at the same time, but showed no reduction in their size relative to females, suggesting seasonal time constraints increase growth rates in males but not in females.
4. No evidence was found that seasonal time constraints resulted in a reduction of size-corrected fat reserves at eclosion, or that minor morphs gained any developmental advantage by reducing investment in horn length.     

Seasonal phenotypic plasticity of wing melanisation in the cabbage white butterfly, Pieris rapae L. (Lepidoptera: Pieridae)

Abstract.  1. Effective thermoregulation is crucial for the fitness of small flying insects. Phenotypic plasticity of the ventral hindwing of pierid butterflies is widely recognised as adaptive for effective thermoregulation. Butterflies eclosing in cooler environments have more heavily melanised wings that absorb solar radiation, thus allowing flight under these cool conditions.
2. Many pierids also exhibit phenotypic plasticity of dorsal forewing melanisation but in this case, cooler environments reduce melanisation. It has been hypothesised that this plasticity is also adaptive because it increases solar reflection from the wing surfaces onto the body in certain basking postures.
3. The degree of seasonal variation in ventral hindwing and dorsal forewing melanisation of wild-caught Pieris rapae was quantified to determine if it shows patterns of plasticity similar to that documented for other Pieris species.
4. Male wing melanisation on both wing surfaces shows the characteristic seasonal, adaptive plasticity. However, only some dorsal forewing pattern elements of females conformed to the predictions of the hypothesis of adaptive dorsal forewing melanisation. Sexual dimorphism of wing pattern plasticity may result from, and/or affect, sexual dimorphism of behaviour and physiology of these butterflies.     

Early predictors of self-biting in socially-housed rhesus macaques (Macaca mulatta)

The development of self-biting behavior in captive monkeys is little understood and poses a serious risk to their well-being. Although early rearing conditions may influence the expression of this behavior, not all animals reared under similar conditions self-bite. The purpose of this study was to examine the effects of three rearing conditions on biting behavior and to determine whether early infant behavior can predict later self-biting. The subjects were 370 rhesus macaques born at the National Institutes of Health (NIH) Animal Center between 1994 and 2004. They were reared under three conditions: mother-reared in social groups (n=183), peer-reared in groups of four (n=84), and surrogate-peer-reared (n=103). Significantly more surrogate-peer-reared animals self-bit compared to peer-only or mother-reared animals. There was no sex difference in self-biting, but this result may have been affected by a sex bias in the number of observations. The durations of behaviors exhibited by the surrogate-peer-reared subjects were recorded in 5-min sessions twice a week from 2 to 6 months of age while the animals were in their home cages and play groups. In the play-group situation, surrogate-peer-reared subjects who later self-bit were found to be less social and exhibited less social clinging than those that did not self-bite. Home-cage behavior did not predict later self-biting, but it did change with increasing age: surrogate clinging and self-mouthing decreased, while environmental exploration increased. Our findings suggest that surrogate rearing in combination with lower levels of social contact during play may be risk factors for the later development of self-biting behavior.     

Aspects of the biology of Pilot whales (Globicephala melaena) in recent mass strandings on the British coast

Five mass strandings of Pilot whales, involving from 23 to 40 animals, occurred on the British coast between 1982 and 1985. The sex ratio in all strandings was biased towards females (62% overall), but more than one mature male was present in each group. A multi-male, polygynous social system is suggested. Growth is rapid from a mean body length at birth of 1.78 m to about 3 m at 2–3 years. Thereafter, males grow faster than females and attain a greater body length by some 18–25%. Maximum body lengths in this study were of a 6.3 m male and a 5.5 m female. The greatest ages determined were of a 20-year-old male and a 25-year-old female, but there is a possibility that readable dentine is not deposited in the teeth of older animals and that some whales are thus of a greater age than can be detected. Females become sexually mature at about seven years of age and a body length of 3–4 m. Some reach sexual senility before death. Males mature at a greater age and at about 5 m in length. Annual calf production is about 11% and no seasonality in parturition could be detected. Pollutant levels are generally within the range of those published for odontocetes, but PCB levels are higher than any yet found in other Pilot whale populations. Evidence of squid was found in three digestive tracts. Blubber thickness increases with the size of the animal, reaching 35–65 mm in adults. The existence of an annual, rigid north-south migrational pattern is unlikely.     

Body size and area‐incidence relationships: is there a general pattern?

Aim This paper tests firstly for the existence of a general relationship between body size of terrestrial animals and their incidence across habitat patches of increasing size, and secondly for differences in this relationship between insects and vertebrates. Location The analysis was based on the occupancy pattern of 50 species from 15 different landscapes in a variety of ecosystems ranging from Central European grassland to Asian tropical forest. Methods The area‐occupancy relationship was described by incidence functions that were calculated using logistic regression. A correlation analysis between body size of the species and the patch area referring to the two given points of the incidence function was performed. In order to test for an effect of taxon (insects vs. vertebrates), an analysis of covariance was conducted. Results In all species, the incidence was found to increase with increasing patch area. The macroecological analysis showed a significant relationship between the incidence in habitat patches and the body size of terrestrial animals. The area requirement was found to increase linearly with increasing body size on a log‐log scale. This relationship did not differ significantly between insects and vertebrates. Conclusions The approach highlighted in this paper is to associate incidence functions with body size. The results suggest that body size is a general but rather rough predictor for the area requirements of animals. The relationship seems valid for a wide range of body sizes of terrestrial animals. However, further studies including isolation of habitats as well as additional species traits into the macroecological analysis of incidence functions are needed.     

Captive breeding reveals larval performance and adult body size differences between two geographical populations of the stag beetle Aegus chelifer chelifer (Coleoptera: Lucanidae)

Stag beetles usually have great intraspecific variation in their body sizes, which can be affected by both environmental and genetic factors. However, direct studies on wild-caught specimens may be insufficient to clarify such variation due to the confounding effects of ecological variance in natural habitats. To evaluate this, the stag beetle Aegus chelifer chelifer MacLeay, 1819 was collected from within two localities (Bangkok metropolitan area and Chanthaburi province) in Thailand and then reared under the same condition to investigate the differences in morphological characteristics between the wild-caught and captive-bred beetles and between the two geographical populations. Narrow-sense heritabilities (h²) of the observed traits in adults were not significant. Variation in the body size of captive-bred specimens was less than in the wild-caught specimens and the overlap of the body size variation between the two populations was lower in the captive-bred beetles. The Chanthaburi population had a significantly larger body size than the Bangkok population. Allometric slopes and intercepts were also significantly different between the two geographic populations. Captive-bred larvae showed similar relative growth rates, but male larvae from the Chanthaburi population had a longer feeding period, and so a larger adult body size, than those from the Bangkok population. The differences between the two populations could be explained by adaptation through larval performances and body size in order to respond to their habitats.     

Relationship between body size and flying-related structures in Neotropical social wasps (Polistinae,Vespidae, Hymenoptera)

Body size influences wing shape and associated muscles in flying animals which is a conspicuous phenomenon in insects, given their wide range in body size. Despite the significance of this, to date, no detailed study has been conducted across a group of species with similar biology allowing a look at specific relationship between body size and flying structures. Neotropical social vespids are a model group to study this problem as they are strong predators that rely heavily on flight while exhibiting a wide range in body size. In this paper we describe the variation in both wing shape, as wing planform, and mesosoma muscle size along the body size gradient of the Neotropical social wasps and discuss the potential factors affecting these changes. Analyses of 56 species were conducted using geometric morphometrics for the wings and lineal morphometrics for the body; independent contrast method regressions were used to correct for the phylogenetic effect. Smaller vespid species exhibit rounded wings, veins that are more concentrated in the proximal region, larger stigmata and the mesosoma is proportionally larger than in larger species. Meanwhile, larger species have more elongated wings, more distally extended venation, smaller stigmata and a proportionally smaller mesosoma. The differences in wing shape and other traits could be related to differences in flight demands caused by smaller and larger body sizes. Species around the extremes of body size distribution may invest more in flight muscle mass than species of intermediate sizes.     

Estimating consumable biomass from body length and order in insects and spiders

1. Current models used to estimate insect prey biomass for diet studies use whole weight. However, a large proportion of an arthropod's body is taken up by an indigestible exoskeleton, leading to erroneous estimation of the food intake of insectivorous animals. 2. Linear mixed effect models were used to obtain equations to predict consumable biomass from body length for a variety of Neotropical insects and spiders. These data were obtained by feeding taxa of various orders to groups of 100 social spiders and comparing pre‐ and post‐consumption weights using size‐matched controls. 3. Significant linear relationships were found relating body size to consumed biomass for all orders, with slopes ranging from 1.276 to 4.011 and R² values from 0.476 to 0.929. For orders other than spiders and Orthoptera, the increase in weight with size exhibited negative allometric scaling, suggesting a decrease in tissue density, or an increase in internal air space, with size. 4. Although there were significant differences across taxonomic orders in the proportion of biomass consumed, within most orders the proportion consumed did not differ significantly with body size. The estimated regression coefficients may be used by other workers to estimate consumable biomass of arthropod prey for studies requiring large sample sizes or non‐lethal sampling of rare or endangered species.     

On the stability of populations of mammals, birds, fish and insects

A key concern for conservation biologists is whether populations of plants and animals are likely to fluctuate widely in number or remain relatively stable around some steady-state value. In our study of 634 populations of mammals, birds, fish and insects, we find that most can be expected to remain stable despite year to year fluctuations caused by environmental factors. Mean return rates were generally around one but were higher in insects (1.09 ± 0.02 SE) and declined with body size in mammals. In general, this is good news for conservation, as stable populations are less likely to go extinct. However, the lower return rates of the large mammals may make them more vulnerable to extinction. Our estimates of return rates were generally well below the threshold for chaos, which makes it unlikely that chaotic dynamics occur in natural populations – one of ecology's key unanswered questions.     

What does determine gonad weight in the wild kissing bug Mepraia spinolai

Female fecundity increases with body size in a variety of insects, but it is unknown if this generalization applies for kissing bugs. In this study, we evaluate whether gonad weight in the bloodsucking insect Mepraia spinolai correlates with body size, or determined by nutrition or developmental time. We found that the investment on reproductive tissue correlates positively and significantly with body size and with the amount of ingested blood by female insects along their lifespan. Total molting time did not significantly affect gonad weight. We suggest that under optimal feeding conditions M. spinolai females could express their maximum reproductive potential.     

Reproductive patterns and birth seasonality in a South-American breeding colony of common marmosets,Callithrix jacchus

We analyzed data on captive-born and wild-caught females housed under natural conditions in a colony located in northeastern Brazil. No differences in reproductive performance were found between captive-born and wild-caught females. Twins were the most frequent litter size, followed by triplets and singletons. No parity effect was observed, with similar infant survival for nulliparous and multiparous females. No significant departures in sex ratio were detected for births and mortality of the male and female infants. The age of the females at the time of pairing showed a negative correlation with pairing-parturition length, but did not affect infant survival. The prolongation in pairing-parturition interval (PPI) and interbirth interval (IBI) was related to birth seasonality. The births were clustered in the second half of the dry season and the beginning of the wet season (November–March), and the time of pairing and the time of infant birth influenced the PPI and IBI, respectively. The use of outdoor cages, which allowed the animals to be aware of the seasonal variations in photo-period and rainfall seems to be sufficient to time the reproductive activity, even when the animals are maintained on a constant food supply.     

Phenotypic variation in male and worker encapsulation response in the bumblebee Bombus terrestris

Abstract.  1. Life-history traits such as immunity are often characterised by the presence of large phenotypic variation, but it often remains unclear how and why this variation is maintained by selection.
2. Here an annual social insect, the bumblebee Bombus terrestris , was used to study variation in encapsulation response of males and workers. Bumblebees are a suitable system to study offspring immunity because they are host to a broad variety of different parasites. Bumblebee males, in particular, have a long lifespan compared with other social insect males and their immunity should therefore be an important element for colony reproductive success.
3. Encapsulation response, which was used here as a measurement for the generalised immune defence capacity of an individual, was found to be a highly variable trait. High levels of worker response correlated with low levels of colony parasitism rates.
4. Encapsulation response was found to be (a) lower in males compared with sister workers, and (b) lower in late-produced cohorts compared with early ones.
5. In colonies with delayed sexual reproduction, males had a lower encapsulation response. Thus, investments into immunity seemed reduced in later male cohorts and those eclosing later in the season, perhaps because males had a shorter expected remaining time to acquire matings. The results presented add further evidence that immune defence is a key variable defining colony fitness in social insects.     

Brain biogenic amines and reproductive dominance in bumble bees (Bombus terrestris)

To begin to explore the role of biogenic amines in reproductive division of labor in social insects, brain levels of dopamine, serotonin, and octopamine were measured in bumble bee (Bombus terrestris) workers and queens that differ in behavioral and reproductive state. Levels of all three amines were similar for mated and virgin queens. Young workers that developed with or without a queen had similar amine levels, but in queenright colonies differences in biogenic amine levels were associated with differences in behavior and reproductive physiology. Dominant workers had significantly higher octopamine levels compared with workers of lower dominance status but of similar size, age, and ovary state. High dopamine levels were associated with the last stages of oocyte development irrespective of worker social status and behavior. These results suggest that biogenic amines are involved in behavioral and physiological aspects of regulation of reproduction in bumble bees. Accepted: 10 December 1999     

Life history reaction norms to time constraints in a damselfly: differential effects on size and mass

Optimality models predict that, under a time constraint, organisms should accelerate development, and preferably so by increasing growth rate, to keep size at emergence constant. Unfortunately, most tests did neglect genetic constraints and interchanged mass with body size which may explain mixed support for some of the models' predictions. We imposed time constraints on full sibling larvae of the damselfly Enallagma cyathigerum by manipulating day length regimes. Under a time constraint, larval development and growth rate based on size indeed were faster. This made it possible to keep size at emergence constant, despite the shorter development time. Interestingly, under a time constraint, growth rate based on mass was not increased and larvae had a lower mass at emergence. We see two reasons for this difference between body mass and size. First, size is fixed at emergence, while mass can still increase in many insects. Secondly, genetic constraints may have contributed to different responses for size and mass. In general, our results strongly suggest discriminating between size and mass when testing life history responses.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 187–196.     

Analysis of pteridines in Pyrrhocoris apterus (L.) (heteroptera,pyrrhocoridae) during development and in body-color mutants

By using thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), five different pteridines have been quantified in extracts from Pyrrhocoris apterus: neopterin, isoxanthopterin, isoxantholumazine (violapterin), 7-methylxanthopterin, and erythropterin. Biopterin was also detected using HPLC. Pteridines have been analyzed separately in bodies and eyes of the wild type regarding developmental stage and sex. The pteridine content in both bodies and eyes increased from nymphs to 2-day-old adults. After this period, the concentration of pteridines in the eyes of adults remained approximately constant, while in the bodies isoxantholumazine, 7-methylxanthopterin, and isoxanthopterin kept increasing until 20 days. Considering the total amount of pteridines per insect, no qualitative or quantitative differences between males and females have been observed except a lower concentration of erythropterin in female bodies. But when pteridines are analyzed per unit body weight, a lower amount of pteridines is always detected in females due to its bigger size. A new body-color mutant, the yolk body mutant, that goes through developmental colour changes, was also analyzed during development, showing a general deficient accumulation of all pteridines, especially of 7-methylxanthopterin and isoxantholumazine in adult bodies. The effect on pteridine content of three other recessive (white, yellow, mosaic) and two dominant (Pale and Apricot) body-color mutations, has also been studied. A specific pteridine pattern different from the wild type was obtained for each mutant. © 1997 Wiley-Liss, Inc.