Brown Morphs Research Articles

Qualitative variation of alkaloids in color morphs of Cystodytes (Ascidiacea)

Despite their great variability, particularly of color, Mediterranean specimens of the genus Cystodytes are usually attributed to the cosmopolitan species Cystodytes dellechiajei. In this study, we used MALDI-TOF and HPLC techniques to assess alkaloid distribution in the four most abundant color morphs of Cystodytes in the western Mediterranean (green, purple, brown and blue). The intraspecimen location of these compounds (either in tunic or zooids) was also analyzed. Two major chemotypes were found: (1) that of the purple morph was based on the sulfur-containing pyridoacridines, shermilamine B, kuanoniamine D and their deacetylated forms; (2) the chemotype of the blue and green morphs was based on the C 9-unsubstituted pyridoacridines, ascididemin and 11-hydroxyascididemin. In the brown morph, ascididemin was only detected by MALDI-TOF. All of these alkaloids were present in both the tunic and zooids, with the exception of the purple morph, in which shermilamine B and kuanoniamine D were found in the tunic, whilst their deacetylated forms were found in both tunic and zooids. Whereas a clear link between these pigments (pyridoacridines) and color was found in the purple morph, color in the other morphs may depend on other unknown molecules. MALDI-TOF proved to be a rapid and reliable tool with which to detect targeted compounds of low molecular mass at both colony and intraspecimen levels, making it effective for the rapid assessment of chemotypes. The chemical differences found raised questions about the taxonomic status of the color morphs attributed to the nominal species C. dellechiajei in the Mediterranean. Our results stress the importance of a detailed morphotype description when working with marine natural products, especially for taxa whose taxonomy is not well resolved, in order to understand fully the variation in secondary chemistry within and between species.

Developmental instability and immune function in colour polymorphic pygmy grasshoppers

Random left minus right deviations from symmetry in otherwise bilaterally symmetric traits may arise due to developmental instability in response to environmental stress. Here we test for variation in developmental instability, measured as asymmetry of (femur) size, among individuals belonging to four different genetically encoded colour morphs of the pygmy grasshopper Tetrix undulata (Sow.) (Orthoptera: Tetrigidae). Such a difference is expected under the hypotheses that perturbed growth and development and concomitant morphological asymmetry may result from exposure to unfavourable temperatures or costs associated with melanization, or reflect a by-product of past disease in individuals with poor immune responsiveness. Results from mixed model two-way ANOVAs uncovered no statistically significant directional asymmetry in femur size, whereas non-directional asymmetry was significant in each of the four different colour morphs. The degree of intraindividual, interlateral variance in femur size varied significantly among individuals belonging to different colour morphs, being considerably higher in the black morph, which also suffers the greatest risk of overheating, compared to the brown, striped and grey morphs. Asymmetry in femur size was not associated with one measure of immune responsiveness, the encapsulation response of individuals experimentally implanted with a novel antigen consisting of a nylon mono-filament. These results are consistent with the notion that individual pigmentation pattern may indirectly influence developmental instability and morphological asymmetry, via the effects of coloration on body temperature.

Fixed Green and Brown Color Morphs and a Novel Color‐Changing Morph of the Pacific Tree Frog Hyla regilla

Pacific tree frogs Hyla regilla are typically either green or brown in dorsal coloration. The frequency of green and brown individuals is known to fluctuate seasonally. Previous investigators have generally assumed that the green and brown body colors represent a "fixed" polymorphism and that seasonal changes in the proportion of the two body colors are a consequence of differential survival of the two color morphs. Here we report that, in addition to the "fixed" (i.e., non-color-changing) green and brown morphs of H. regilla, there are some individuals that can change hue between green and brown. The distribution of color-change ability in our study population is bimodal, suggesting that "color changers" are a distinct morph rather than one extreme of a continuous distribution of color-change ability. Our findings suggest that background brightness, not hue, triggers color change in the newly discovered morph and that this change requires days to weeks to occur. Such slow color change is not well suited for making short-term changes in color as a frog moves between differently colored substrates. Rather, seasonal changes in habitat characteristics and/or microhabitat use are likely to maintain color-change ability. Color polymorphism and color-change ability appear to represent alternative responses to divergent selection for crypsis in a heterogeneous, seasonally variable environment.

Ecological mechanisms for coexistence of colour polymorphism in a coral-reef fish: an experimental evaluation.

The evolution of different colour morphs and how they are maintained in animal populations is poorly understood. We investigated the mechanisms maintaining yellow and brown morphs of a coral-reef fish, Pseudochromis fuscus, at Lizard Island, on the Great Barrier Reef. Histological examination of the gonads revealed that colour morphs were not sex-limited, therefore sexual selection does not appear to promote dichromatism in this species. The field distributions of the two colour morphs were spatially segregated, limiting the opportunity for negative frequency-dependent selection to operate. Our results support another ecological mechanism of coexistence. The yellow morph occurred in deeper areas, usually close to the reef edge, where there was a proportionally high cover of live branching corals. In contrast, the brown morph occurred in shallower areas, more distant from the reef edge, that were proportionally low in live branching corals. Within these habitats, each colour morph of P. fuscus displayed a close association with similar coloured damselfishes from the genus Pomacentrus. The yellow morph was associated with predominantly yellow damselfishes (P. moluccensis and P. amboinensis) and the brown morph with darker coloured species (P. adelus and P. chrysurus). Multiple-choice experiments in the laboratory revealed that: (1) each colour morph of P. fuscus preferentially selected habitat patches occupied by damselfishes with the same colouration; and (2) differences in microhabitat use between the two colour morphs of P. fuscus were due to the presence of different coloured damselfishes in these microhabitats. P. fuscus is a predator of newly recruited damselfishes and the striking resemblance between each morph of P. fuscus and the damselfish with which it was associated, suggests that aggressive mimicry may promote coexistence of P. fuscus colour morphs.

Variable plumage and bare part colouration in the Brown Falcon, Falco berigora: the influence of age and sex

The Brown Falcon, Falco berigora, is one of Australasia's most common raptors, yet considerable confusion remains over the influence of geography, age and sex on plumage and bare part colouration in this species. To address this issue, 160 immature and adult falcons from an individually marked, closely monitored population were examined. In contrast to previous studies, all were of known sex, age-group and part of the resident population or their offspring. Adult males had significantly lighter upperpart, cap, ventral and underwing covert plumage in comparison with other birds, closely resembling what has previously been described as a ‘rufous morph’. Immature females were significantly darker than other ages and sexes in upperpart and underwing covert plumage, resembling descriptions of ‘dark morphs’. In contrast, plumage of immature males and adult females tended to be similar and intermediate between these extremes, resembling the ‘brown morph’. The buff-tinged, not white, ventral plumage and darker underwing covert plumage of immature males separated them from adult females. Cere and orbital ring colour also differed with sex and age: immature females had the dullest facial bare parts and adult males the brightest, adult females and immature males again being intermediate between the two. The results indicate that most variation in plumage and facial bare part colouration observed in the population could be attributed to age and sex differences as opposed to racial clines or the existence of colour morphs. Moreover, the brighter colours of adult falcons may function as honest signals of quality.

Natural selection and the distribution of shell colour morphs in three species of Littoraria (Gastropoda: Littorinidae) in Moreton Bay, Queensland

The distribution of yellow, brown and red morphs of sympatric species of Littoraria were recorded on mangrove trees of the genus Avicennia within Moreton Bay, Queensland. The roles of background mimicry (leaf vs. bark, dark vs. light), niche selection and thermal tolerance (sunny vs. shaded positions and height above ground) were examined. The yellow advantage found previously in the area was tested. Total yellow morph frequency adjusted to a reduction in leaf background on pruned trees. Morph frequencies in Littoraria species reflect differences in habitat use. L. filosa (high yellow frequency) was more frequently found on leaves at the highest tree levels, while L. luteola (high brown frequency) was more frequently found on branches at lower levels. It is therefore argued that morphs mimic background elements. Previously reported niche selection by yellow and brown morphs of leaf and bark backgrounds is shown to be a result of the distribution of L. luteola on branches and L. filosa on leaves. At warmer times of the year, yellow L. filosa were more common in sunny positions; this is thought to be a result of thermal tolerance. There appears to be some advantage to particular morphs on particular tree types, but this relationship needs to be examined further. Mangrove-dwelling Littoraria are a promising model to investigate molluscan polymorphism. In the past, erroneous identification of sympatric species may have influenced the accuracy of reported patterns. We used allozyme electrophoretic markers as a precise identification technique.

Sexual isolation and cuticular hydrocarbons in Drosophila elegans.

In Drosophila elegans, partial sexual isolation has developed between the brown and black morphs, which are distributed allopatrically. The present study aims to understand how they discriminate between potential mates. Mating experiments show that the females of the two morphs differ in sexual signal(s) and the males discriminate using these differences. Body colouration is not used as a sexual cue in this species. Between the females of the two morphs, a large difference was observed in the percentages of 7-pentacosene and 9-pentacosene on the cuticle. Genetical analysis using recombinant inbred lines supported the possibility that the concentration of these pentacosenes plays a role in mate discrimination of these two morphs. However, males did not respond to killed females at all, suggesting that cuticular hydrocarbons of females are not the only cue for the induction of male courtship behaviour. It may be that unknown signals or substances are essential to induce male courtship and pentacosenes modulate the attractiveness of females, positively in the black morph and negatively in the brown morph. Drosophila elegans F1 offspring had intermediate characteristics in mate discrimination and hydrocarbon composition between the parental brown and black morph strains. The number of loci responsible for the differences in the concentration of pentacosenes and the male and female components in the mate recognition between these two morphs is suggested to be more than one.

Headbob Display Analysis of the Grand Cayman Anole, Anolis conspersus

Headbob displays from 22 adult male Anolis conspersus of three (green, brown, and blue) were videotaped in the laboratory. Frame-by-frame coordinates of the vertical head mo- tions were used to generate display-action-pattern (DAP) graphs. Field observations had revealed that only one type of headbob was performed when males displayed to nonspecific audiences while moving around their territories (male-alone context). During staged male encounters in the lab (male-male context), Type A displays and a second type of B) were produced. The two types of displays were partitioned into units that were compared among the color morphs. We then trans- formed the units with principle components analysis and used one-way ANOVAs to test statistically for differences among the color morphs at the unit level. Finally, we used discriminant function analysis to test for color morph differences at the display level. Graphical visualization and statistical analyses showed that, like body coloration, the green and the brown morph are more distinctive from each other than either is from the blue morph, although the differences in units among the color forms are subtle. Given that A. conspersus is a member of the seven-species Anolis radiation on Jamaica, we compare the structure of one of its displays (Type A) with that of its closest relative, Anolis grahami. Last, we speculate on the possible origin of the unusual structure observed in the A. conspersus Type B display.

Plumage polymorphism of red‐footed boobies (Sula sula) in the western Indian Ocean: an indicator of biogeographic isolation

AbstractThe pantropical red‐footed booby Sula sula is one of the most polymorphic seabirds. In the Indian Ocean most extant colonies hold white morph adults except on Europa Island (southern Mozambique Channel), where adults are of the white‐tailed brown morph and on Tromelin Island (western Indian Ocean), where one‐third of the birds are of the white‐tailed brown morph and two‐thirds are of the white morph. On Tromelin, the morph ratio has remained constant over the last 40 years. An extinct colony (Glorieuses Islands, northern Mozambique Channel) once supported a white‐tailed brown morph population. These results suggest that the colonies of the western Indian ocean do not constitute one great gene pool where exchanges occur, but are isolated at various degree from each other. Particularly, the population of Europa is the only current population of the Indian Ocean constituted almost entirely of white‐tailed brown morph, suggesting that it is isolated from other nearby colonies. Possible causes of isolation are discussed in the light of oceanic features of the Mozambique Channel. Although further studies are needed to understand the adaptive significance of plumage coloration in red‐footed boobies, I suggest that white‐tailed brown morph at Europa may act as a defensive camouflage against kleptoparasitism by great frigatebirds Fregata minor and brown skuas Catharacta antarctica.

Plumage polymorphism of red-footed boobies (Sula sula) in the western Indian Ocean: an indicator of biogeographic isolation

The pantropical red-footed booby Sula sula is one of the most polymorphic seabirds. In the Indian Ocean most extant colonies hold white morph adults except on Europa Island (southern Mozambique Channel), where adults are of the white-tailed brown morph and on Tromelin Island (western Indian Ocean), where one-third of the birds are of the white-tailed brown morph and two-thirds are of the white morph. On Tromelin, the morph ratio has remained constant over the last 40 years. An extinct colony (Glorieuses Islands, northern Mozambique Channel) once supported a white-tailed brown morph population. These results suggest that the colonies of the western Indian ocean do not constitute one great gene pool where exchanges occur, but are isolated at various degree from each other. Particularly, the population of Europa is the only current population of the Indian Ocean constituted almost entirely of white-tailed brown morph, suggesting that it is isolated from other nearby colonies. Possible causes of isolation are discussed in the light of oceanic features of the Mozambique Channel. Although further studies are needed to understand the adaptive significance of plumage coloration in red-footed boobies, I suggest that white-tailed brown morph at Europa may act as a defensive camouflage against kleptoparasitism by great frigatebirds Fregata minor and brown skuas Catharacta antarctica.

Effects of Copulation Duration on Fertility and Sexual Receptivity of Females in Drosophila elegans

Abstract In Drosophila elegans, copulation duration is shorter in the brown morph (about 11 min) than in the black morph (25–35 min). In this study, it appeared that sperm transfer also occurred at an earlier stage of copulation in the brown morph than in the black morph and both sexes were responsible for the control of sperm transfer. In the HK (brown morph) strain, number of eggs produced per female decreased to some extent when copulation was interrupted 3 min after the start of copulation. In the OH (black morph) strain, the rate of sperm transfer was low when copulation was interrupted 3 or 5 min after the start of copulation. Thus, shortened (3–5 min) copulation was disadvantageous in this species. However, adaptive significance of prolonged (>10 min) copulation of the black morph was not apparent in the present experiments. Females of the HK strain recovered receptivity earlier than those of the OH strain irrespective of male-type in the previous mating: i.e., the former will mate more times in th...

The major carotenoid pigments of the grain aphid, Sitobion avenae (F.) (Hemiptera: Aphididae)

SummaryThe economically important grain aphid, Sitobion avenae (F.) shows colour polymorphism, with brown and green forms predominating. Colour is determined both genetically and in response to environmental factors, including nutrition. The biological significance of the colour polymorphism is unknown, although seasonal changes occur in the frequency of colour morphs in the field, whilst the brown morph may have adaptive significance in terms of hymenopterous endoparasitism. The ground colour of aphids is produced by haemolymph pigments, aphins (glucosides) and carotenoids. The latter may be under the synthetic control of intracellular endosymbiotic bacteria. In this study, the major carotenoid pigments of a brown and a green clone of S. avenae were examined using thin layer chromatography (TLC) and high‐performance liquid chromatography (HPLC), and their absorbance spectra recorded. Using TLC, the brown clone produced five bands of different Rf, ranging from yellow, to orange‐pink to pink in colour. In contrast, the green clone gave only a single yellow band of higher Rf than any of the bands of brown aphids. Following separation of carotenoids by HPLC, brown aphids gave seven peaks and green aphids five. Comparison of absorbance maxima with known published values for carotenoids provides strong evidence for the identification of four of the carotenoid pigments from brown aphids (RB‐4, 3,4‐didehydrolycopene; RB‐5, torulene; RB‐6; lycopene; RB‐7, γ‐carotene) and one from green aphids (RG‐2, α‐carotene). The other carotenoids remain unidentified. The biosynthesis and possible biological relevance of the various pigments of S. avenae are briefly discussed.

Copulation Duration and Its Genetic Control in Drosophila elegans

Copulation duration differed between black and brown morphs of Drosophila elegans: longer in the former than in the latter. Experiments on copulation between these two morphs revealed that copulation duration was determined by both sexes. The genetic analyses using F1 hybrids and recombinant inbred lines suggest that two or more loci were responsible for the differences in both of male and female properties for the determination of copulation duration between the black and brown morphs and at least one of the loci governing the male property was probably located on the X chromosome. It also appeared that loci responsible for the difference in copulation duration of males between the brown morph and black morph strains differed from those responsible for the difference in copulation duration of females between them. Genes controlling male copulation duration are at least partly linked with a gene controlling body coloration.

Depth-related variation in regeneration of artificial lesions in the Caribbean corals Porites astreoides and Stephanocoenia michelinii

Regeneration of artificial lesions was studied along a depth gradient from 5–35 m in the Caribbean corals Porites astreoides (brown morph) and Stephanocoenia michelinii (massive morph). During the first 3–4 weeks of the regeneration process tissue recovery in both coral species was higher in shallow water than in deep water colonies. After 7 weeks when the lesions were almost closed, however, shallow as well as deep water colonies had restored the damage to the same degree, showing that regeneration is a high priority process in coral ecology. The deep water colonies did not show signs of photoacclimatization. The zooxanthellae densities and the total chlorophyll concentration per algal cell in the coral tissue did not vary significantly with depth. Furthermore, there was no decrease with depth of the chlorophyll a/ c 2 ratio, which would have indicated photoacclimatization by means of a relative increase of chlorophyll c 2 which is more efficient in using the blue light available at depth. One possibility which may explain the slower tissue recovery in deep water colonies during the first stage of the regeneration process, is a combination of the reduced light levels at depth and a lack of chlorophyll acclimatization in the deep water colonies.

Gene frequency changes inCepaeasnails on the Marlborough Downs over 25 years

In 1985 we resurveyed the sites on the Marlborough Downs in southern England at which Cain and Currey in 1960/61 sampledCepaeasnails and thence introduced the term «area effects» to describe large areas of uniform morph frequency. Some sites no longer harbouredCepaeaand at others the species composition had changed, with a general spread ofCepaea hortensisat the expense ofCepaea nemoralis. The majority, however, permitted comparison of morph frequencies between the two surveys. InC. nemoralis, we detected a significant overall decrease in the frequency of the brown morph and estimate selection as 5–9% per generation. There was no apparent change in frequencies of banded morphs. InC. hortensiswe detected a significant overall increase in the frequency of unbanded shells (1–3% selection per generation) and an almost significant decrease in the frequency of fusions within the banded class. There was insufficient colour polymorphism inC. hortensisto allow analysis of colour morph frequencies. These changes — all in the direction of reduced absorption of solar energy — resemble others detected in both species at other localities in southern England. Possible explanations include large-scale climatic effects and changes in vegetation.

Gene frequency changes in Cepaea snails on the Marlborough Downs over 25 years

In 1985 we resurveyed the sites on the Marlborough Downs in southern England at which Cain and Currey in 1960/61 sampled Cepaea snails and thence introduced the term ‘area effects' to describe large areas of uniform morph frequency. Some sites no longer harboured Cepaea and at others the species composition had changed, with a general spread of Cepaea hortensis at the expense of Cepaea nemoralis. The majority, however, permitted comparison of morph frequencies between the two surveys. In C. nemoralis, we detected a significant overall decrease in the frequency of the brown morph and estimate selection as 5–9% per generation. There was no apparent change in frequencies of banded morphs. In C. hortensis we detected a significant overall increase in the frequency of unbanded shells (1–3% selection per generation) and an almost significant decrease in the frequency of fusions within the banded class. There was insufficient colour polymorphism in C. hortensis to allow analysis of colour morph frequencies. These changes—all in the direction of reduced absorption of solar energy—resemble others detected in both species at other localities in southern England. Possible explanations include large-scale climatic effects and changes in vegetation.

Sedimentation and distributions of green and brown morphs of the Caribbean coral Porites astreoides Lamarck

Sediments suspended in the water column and settling on to reef surfaces are thought to exert control on coral distributions through both lethal and sublethal effects. I investigated whether variation in sedimentation rates can adequately explain patterns of distribution observed along depth gradients for green and brown colonies of the common Caribbean coral Porites astreoides Lamarck. Colony abundances and rates of downward flux of suspended particulates (i.e., sedimentation rates) were assessed along depth gradients at four sites (Tague Bay, Buck Island, Cane Bay and Salt River Canyon) on St. Croix, US Virgin Islands. In all but one instance, 12 m depth at Tague Bay, distributions of green and brown P. astreoides varied predictably with differences in sedimentation rates: higher levels of sedimentation corresponded with a lower proportion of green colonies. Laboratory experiments conducted with colonies from the low sediment Cane Bay site showed that brown colonies not only shed sediment from the colony surface significantly better than green colonies, but also suffer less sediment-induced tissue death. While previous models of sediment resistance in corals have been based on variation in colony shape and polyp architecture, results obtained here indicate that major differences in these parameters may not be necessary for differential tolerances to occur.

Ecological and Life History Characteristics of Botryllus schlosseri Tunicata Populations Inhabiting Undersurface Shallow‐Water Stones

Abstract. Populations of Botryllus schlosseri PALLAS 1772. a cosmopolitan colonial ascidian. were examined on the undersurface of stones for the first time in three adjoining localities along the Israeli Mediterranean coast. A two‐year study of 1589 stones which were inhabited by 1345 colonies, revealed that colony coverage was < 1.5 % of the total available substrate area; values were highest in spring, lowest in winter. The two years differed significantly in the number of colonies · m 2, and these numbers were correlated with mean seawater temperatures. Most of the stones contained 1–5 Botryllus colonies year‐round; no significant correlation was found between number and stone size. The brown morph was dominant 80 % at all three localities. The distribution of other colour morphs differed between localities. Reproductive colonies were either hermaphroditic or contained male gonads only. Peak reproduction was in the spring, but did not correlate with seawater temperatures. While colony size ranged between I and 1I55zooids, sexually mature colonies consisted of 171–273 zooids on the average, compared with 37–90 zooids for sterile colonies. The three populations differed significantly in several ecological and life history characteristics. This further confirmed past studies indicating that Botryllus populations are characteristically divided into local subpopulations exhibiting microgeographic differences in life history patterns. The results are compared with the accumulated data on other world‐wide Botryllus populations residing in other habitats.

Dimorphism in the Ascidian Pyura stolonifera Near Melbourne, Australia, and its Evaluation Through Field Transplant Experiments

Abstract. On the central coast of Victoria, Australia, the ascidian Pyura stolonifera (Heller. 1878) assumes 2 morphs. a yellow form living exclusively on inner shores, and a brown morph mainly on outer coasts. Distributional surveys, morphological analyses and field transplant experiments were conducted as part of a multidisciplinary investigation designed to elucidate the environmental and genetic components of dimorphism in this species. Distributional surveys revealed that the 2 morphs have a parapatric distribution. Morphological analyses showed striking differences between morphs in colours of tissue types, external anatomy, morphometry and gravimetry. Possible ecological significances of this morphological differentiation are discussed. Transplant experiments, in which morphs were moved within and between habitats, yielded no evidence for morphological plasticity in adults of this species for the great majority of characters examined.

Incipient reproductive isolation between two morphs of Drosophila elegans (Diptera: Drosophilidae)

Drosophila elegansis a flower-breeding species occurring in tropical and subtropical regions of Asia. Two morphs, brown and black, are known in this species. The brown morph is recorded from southern China, Philippines, Indonesia and New Guinea, while the black morph is from the Okinawa islands and Taiwan. The present crossing experiment suggests that the difference of body colour between them was due to alleles on a single locus or closely linked loci on an autosome; F1hybrids exhibited intermediate body colour. Female choice tests revealed asymmetrical premating isolation between the brown and black morphs; isolation indices ranged from 0.55 to 0.83 in the tests using females of the black morph (deviation from random mating was significant), but from −0.03 to 0.50 in the tests using females of the brown morph (deviation from random mating was insignificant). However, body colour was not used as a criterion of mate choice by females. A weak and asymmetrical postmating isolation was also observed between the brown and black morphs; viability was lowered in F2progenies of crosses between females of the brown morph and males of the black morph. No premating or postmating isolation was observed between geographic strains of each morph. Under irradiation, body temperature was higher in the black morph than in the brown morph. On the other hand, no significant difference was observed in tolerance to cold, heat and desiccation between the brown and black morphs.