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Monarch butterflies in North America have an exceptionally large breeding distribution, occupying regions west of the Rocky Mountains and throughout the eastern seaboard. An experimental study conducted 17 years ago and published in this journal appeared to show that western monarch larvae tend to have smaller black stripes than those from eastern parents, which at the time was thought to be an adaptation to higher solar exposure in California. Here, we revisit this question by measuring melanism of eastern and western larvae from online photographs submitted to iNaturalist by members of the public. We downloaded over 500 photos of larvae from 10 different states (4 in the west, 6 in the east) and used image analysis to quantify the size of each larva's black stripes (% of surface covered by black). We compared average melanism level between east and west, while also accounting for temperature (at the photo location), seasonal effects, and latitude. Results showed larvae tended to be darker with lower development temperatures, and later in the season, though there was no significant difference between eastern and western larvae in their degree of melanism. It is not yet clear why findings here were different from the prior experimental study. Also, the wild larvae appeared to be notably lighter in color than the captive-reared larvae of the original study, suggesting that the captive environment does not truly replicate the developmental experience of wild larvae, at least in terms of cuticular development. Thus, if there truly are innate tendencies for western larvae to differ (morphologically) from eastern, they are not observable in nature. • Monarch butterflies in North America were once thought to have two distinct eastern and western populations. • Early laboratory work published in this journal showed western larvae were lighter in color than eastern. • Melanism levels of 500+ online photos of wild larvae showed no difference between western and eastern subpopulation larvae. • Monarch larvae tend to be darker with lower temperatures, and, later in the season. • Findings are consistent with more recent evidence for a single population in North America. [ABSTRACT FROM AUTHOR]

In animals with complex life cycles, all resources needed to form adult tissues are procured at the larval stage. For butterflies, the proper development of wings involves synthesizing tissue during metamorphosis based on the raw materials obtained by larvae. Similarly, manufacture of pigment for wing scales also requires resources acquired by larvae. We conducted an experiment to test the effects of food deprivation in the larval stage on multiple measures of adult wing morphology and coloration of monarch butterflies (Danaus plexippus), a species in which long-distance migration makes flight efficiency critical. In a captive setting, we restricted food (milkweed) from late-stage larvae for either 24 hrs or 48 hrs, then after metamorphosis we used image analysis methods to measure forewing surface area and elongation (length/width), which are both important for migration. We also measured the brightness of orange pigment and the intensity of black on the wing. There were correlations between several wing features, including an unexpected association between wing elongation and melanism, which will require further study to fully understand. The clearest effect of food restriction was a reduction in adult wing size in the high stress group (by approximately 2%). Patterns observed for other wing traits were ambiguous: monarchs in the low stress group (but not the high) had less elongated and paler orange pigmentation. There was no effect on wing melanism. Although some patterns obtained in this study were unclear, our results concerning wing size have direct bearing on the monarch migration. We show that if milkweed is limited for monarch larvae, their wings become stunted, which could ultimately result in lower migration success. [ABSTRACT FROM AUTHOR]

Mammalian pelage color can vary among individuals of many species, although this intraspecific variation is often overlooked by researchers, perhaps because of its sometimes subtle nature and difficulty in assessing it quantitatively. Thus, such variation is rarely studied in mammals, and this is especially true within the order Chiroptera, where there has been very little empirical research. We examined museum specimens of red bats (Lasiurus borealis, family Vespertilionidae) from Georgia, USA, to determine the extent of sexual dimorphism in pelage color and to explore possible associations between body size and pelage color. We photographed 54 specimens under uniform lighting, and used an image analysis program to measure pelage hue on the uropatagium region, which is fully furred in members of the genus Lasiurus. Statistical analyses of pelage hue scores showed males had significantly redder pelage than females when considered alone, but when examined together with effects of body size and collection year, sex was not significant, and collection year and body size were. More recent specimens tended to be less red than older specimens, which might indicate a wearing of the buffy tips of hairs from older specimens, and smaller bats of both sexes tended to be more red. These interesting findings are encouraging and we suggest that future explorations into intraspecific variation in pelage color of bats using this or similar approaches are warranted to clarify the significance of the patterns. This study also demonstrated that care must be taken in analyses of mammalian pelage color from older museum skins, or at least that researchers must take into account the age of the specimens [Current Zoology 56 (4): 401-405, 2010]. [ABSTRACT FROM AUTHOR]

The article discusses a study on the use of a method for quantifying mammal hair morphology and assessing morphological characteristics of mammalian hair for zoological research. In this study, morphological measurements were obtained on 120 hair samples from white-tailed deer Odocoileus virginianus using a standard flatbed scanner and an image analysis software program. Results show that the width of hair shafts ranged from 0.08 millimeter (mm) to 0.21 mm with normal distribution and a 2.2 mm average length of color bands measured by hue and brightness scores. Data also include the two-dimensional surface area measurement. The study suggests the importance of these parameters to examining factors influencing the morphology of mammalian hair, or assessing nutritional status.

The demands of long-distance flight represent an important evolutionary force operating on the traits of migratory species. Monarchs are widespread butterflies known for their annual migrations in North America. We examined divergence in wing morphology among migratory monarchs from eastern and western N. America, and nonmigratory monarchs in S. Florida, Puerto Rico, Costa Rica, and Hawaii. For the three N. American populations, we also examined monarchs reared in four common environment experiments. We used image analysis to measure multiple traits including forewing area and aspect ratio; for laboratory-reared monarchs we also quantified body area and wing loading. Results showed wild monarchs from all nonmigratory populations were smaller than those from migratory populations. Wild and captive-reared eastern monarchs had the largest and most elongated forewings, whereas monarchs from Puerto Rico and Costa Rica had the smallest and roundest forewings. Eastern monarchs also had the largest bodies and high measures of wing loading, whereas western and S. Florida monarchs had less elongated forewings and smaller bodies. Among captive-reared butterflies, family-level effects provided evidence that genetic factors contributed to variation in wing traits. Collectively, these results support evolutionary responses to long-distance flight in monarchs, with implications for the conservation of phenotypically distinct wild populations. [ABSTRACT FROM AUTHOR]

Amphibians have long been known to display wide variation in erythrocyte morphology across species, but within species there has been little attention given to individual variation in red blood cell morphology. We captured 49 red-backed salamanders (Plethodon cinereus) from central Pennsylvania, USA and used image analysis procedures to measure erythrocyte morphology (size and shape) on blood smears made from all individuals. We then statistically examined whether variation in snout-vent-length, sex, tail loss, or capture location influenced these cell variables. Only snout-vent-length affected erythrocyte size and shape, with increasing body sizes associated with increasing cell areas and increasingly rounder cells. Further, erythrocyte shape was also associated with a measure of body condition that was corrected for body size, such that individuals with high body condition scores had rounder cells. Given the oxygen-carrying role of erythrocytes in all vertebrates, we suspect this discovery is related to size-related changes in oxygen demand, since total oxygen consumption increases with body size in an allometric manner. While our results warrant further investigation to understand the mechanism, the association we found between cell roundness and both body size and condition nevertheless indicates this parameter could be used to assess the health state of plethodontid salamanders in future research, provided non-destructive sampling is employed. Our results also underscore the value of hematological investigations in the study of animal biology. [ABSTRACT FROM AUTHOR]

Monarch butterflies are famous among insects for their unique migration in eastern North America to overwinter sites in Mexico and their bright orange wing color, which has an aposematic function. While capturing migrating monarchs in northeast Georgia, USA, I noticed that many appeared to have unusually deep orange wings. I initiated the current study to compare wing hues (obtained using image analysis of scanned wings) of migrants (captured in 2005 and 2008) to samples of breeding and overwintering monarchs. Consistent with initial observations, migrants had significantly lower orange hues (reflecting deeper, redder orange colors) than breeding and overwintering monarchs. There was also a difference in hue between sexes and a relationship with wing size, such that largermonarchs had deeper, redder hues. The reasons for the color difference of migrants are not apparent, but one possibility is that the longer-lived migrant generation has denser scalation to allow for scale loss over their lifespan. Alternatively, this effect could be confined to the subpopulation of monarchs in the Southeastern United States, which may not be well represented at the Mexican overwintering sites. In any case, this discovery highlights the many questions emerging on the significance of wing color variation in this species. [ABSTRACT FROM AUTHOR]

Reports of sexual dichromatism in salamanders are rare and have been generally restricted to a few species in the families Hynobiidae and Salamandridae. We used image analysis techniques to examine sexual dichromatism in the marbled salamander, Ambystoma opacum (Gravenhorst, 1807). We measured the average hue of white saddles on male and female marbled salamanders (n = 118), as well as the proportion of white dorsal surface area relative to the black dorsal surface area, to determine the extent of sexual dichromatism in this species. We also tested whether patterning and coloration were correlated with body size or relative body mass. Males had significantly whiter saddles and higher relative proportions of white coloration on their dorsal surfaces than did females. Furthermore, the relative proportion of white areas on the dorsum was positively correlated to body condition in both males and females. Body size was not correlated with hue or proportion of white area on the dorsum. To our knowledge, we report the first confirmation of sexually dimorphic coloration in the ambystomatid salamander family, extending the known distribution of sexual dichromatism in the order Caudata. [ABSTRACT FROM AUTHOR]

The article discusses the method for obtaining and counting hemocytes in milkweed bugs. One method relies on estimates of overall hemocyte volume after centrifugation of hemolymph in hematocrit tubes. Electronic particle counters have been used to count marine arthropod hemocytes. Liquid nitrogen fixation has been used to compare the numbers of hemocytes in tissue sections to counts made of hemolymph from severed appendages.

Focuses on the quantification of monarch butterfly larval pigmentation using digital image analysis. Effects of rearing temperature on larval blackness; Measurement of pigmentation in Lepidopteran larvae.