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Recent collecting efforts in the upper Malagarazi basin (2013–2022) allowed for an integrative study based on qualitative (colour), quantitative (meristic and metric), and barcoding gene [mtDNA, cytochrome c oxidase (COI)] data of specimens similar to Enteromius sp. ‘ascutelatus’, being a previously identified, potentially, new species. Based on these data, the present study confirms its identification as a new species for science, which is here formally described as Enteromius nzigidaherai sp. nov. This new species belongs to the group of Enteromius species for which the last unbranched ray of the dorsal fin is flexible and devoid of serrations along its posterior edge. This species has a horizontal series of black spots at the midlateral level of the sides. Three congeneric species, known from the Congo basin sensu lato, with two of them also found in the upper Malagarazi basin, are most similar to it. However, E. nzigidaherai sp. nov. is distinguished from the two sympatric upper Malagarazi species, that is, E. quadrilineatus and E. lineomaculatus, at least by two meristics and two morphometrics. It is also distinguished from E. urostigma, known from the upper Congo basin, by two meristics and one, apparently related, morphometric. In addition, a barcoding (mtDNA, COI) study revealed that the specimens of E. nzigidaherai sp. nov. form a well‐supported, separate lineage, with a K2P genetic distance of more than 10% with specimens identified as E. quadrilineatus and E. lineomaculatus, both originating from the upper Malagarazi basin and for which tissue samples were available. Finally, the new species was found to be endemic to the upper reaches of two left bank affluents of the upper Malagarazi basin: the Muyovozi and the Kinwa. However, both affluents are threatened by human activities, which seem to have resulted in its local disappearance as recent intensive collecting efforts in the latter affluent have remained unsuccessful. The species should thus be considered Critically Endangered (CR) according to IUCN criteria B1ab(ii,iv)c(i,iii). Therefore, it is hoped that the present description draws renewed attention to the importance of aquatic protection in the region by highlighting the need for the effective establishment of the Malagarazi Nature Reserve and concern for its optimal delimitation to efficiently protect the entire ichthyofauna of the upper Malagarazi, without excluding the fish species confined to its affluent rivers. [ABSTRACT FROM AUTHOR]

A new species of Melanorivulus is described from the upper Taquari River drainage, upper Paraguay River basin, in the Western Brazilian Cerrado. This species is a member of the Melanorivulus pictus group, endemic to the central Brazilian plateau and adjacent areas. Melanorivulus terena, new species, is endemic to the Paraguay River basin and is possibly closely related to other species endemic to the upper Paraná River basin, such as M. linearis, M. interruptus and M. egens, by the absence of distinctive dark marks on the humeral region in males. The new species is distinguished from all other species of the M. pictus group by a distal margin of unpaired fins and pelvic fin that is orangish red, and by the number of scales in the transversal series. The possible close relationship between the new species and other species recorded in the Paraná River basin may indicate an ancestral interconnection of the headwaters of the Rio Taquari (Paraguay River basin) with the headwaters of the upper Rio Verde and Rio Pardo (Paraná River basin). [ABSTRACT FROM AUTHOR]

Mating cues are often comprised of several elements, which can act independently, or in concert to attract a suitable partner. Individual elements may also function in other contexts, such as anti-predator defense or camouflage. In Heliconius butterflies, wing patterns comprise several individual color pattern elements, which advertise the butterflies' toxicity to predators. These wing patterns are also mating cues and males predominantly court females that possess the same wing pattern as their own. However, it is not known whether male preference is based on the full wing pattern or only individual pattern elements. We compared preferences of male H. erato lativitta between female models with the full wing pattern and those with some pattern elements removed. We found no differences in preference between the full wing pattern model and a model with pattern elements removed, indicating that the complete composition of all elements is not essential to the mating signal. Wing pattern preferences also contribute to pre-mating isolation between two other Heliconius taxa, H. erato cyrbia , and H. himera ; therefore, we next compared preferences for the same models in these species. H. erato cyrbia and H. himera strongly differed in preferences for the models, potentially providing a mechanism for how pre-mating isolation acts between these species. These findings suggest that contrasting levels of selective constraint act on elements across the wing pattern. [ABSTRACT FROM AUTHOR]

The study of colour, including physical properties and patterns, is an essential step in comprehensively understanding the role, evolution and diversification of this trait involved in functions like survival, performance, reproductive success and communication. While quantitative studies on colour have primarily focused on colour attributes, such as hue or brightness, the quantitative assessment of how colours are distributed across an organism's body (i.e. pattern) has received less attention despite its high functionality irrespective and together with colour. This gap is particularly noticeable in amphibians, especially in highly polymorphic, continuously variable species. In this study, we use the urodele Salamandra salamandra as a study model to apply an analytical approach for extracting and quantifying colour proportions and patterns variation using the recently developed R packages patternize and recolorize to precisely describe and compare colour distribution at both taxonomic and habitat levels. We first assessed the potential application of this workflow in taxonomic studies by examining its accuracy and sensitivity in differentiating morphs, using S. s. bernardezi and S. s. gallaica subspecies. Subsequently, we applied the same analytical approach to compare colour and colour pattern shifts among population of S. s. bernardezi within an urban–forest system. Our results demonstrated that this methodological workflow effectively detects differences in colour patterns at the taxonomic and habitat levels, confirming its utility in different fields, from systematics to eco‐evolutionary studies. Furthermore, our results revealed an increased prevalence of melanistic colouration and a less homogeneous colour pattern within urban settings, contributing to the limited number of studies about amphibian colouration in anthropic habitats. We outline and discuss alternative hypotheses to explain these patterns, although further investigation is necessary to address several new questions that arise from our results. [ABSTRACT FROM AUTHOR]

A common goal in evolutionary biology is to discern the mechanisms that produce the astounding diversity of morphologies seen across the tree of life. Aposematic species, those with a conspicuous phenotype coupled with some form of defence, are excellent models to understand the link between vivid colour pattern variations, the natural selection shaping it, and the underlying genetic mechanisms underpinning this variation. Mimicry systems in which species share a conspicuous phenotype can provide an even better model for understanding the mechanisms of colour production in aposematic species, especially if comimics have divergent evolutionary histories. Here we investigate the genetic mechanisms by which mimicry is produced in poison frogs. We assembled a 6.02‐Gbp genome with a contig N50 of 310 Kbp, a scaffold N50 of 390 Kbp and 85% of expected tetrapod genes. We leveraged this genome to conduct gene expression analyses throughout development of four colour morphs of Ranitomeya imitator and two colour morphs from both R. fantastica and R. variabilis which R. imitator mimics. We identified a large number of pigmentation and patterning genes differentially expressed throughout development, many of them related to melanophores/melanin, iridophore development and guanine synthesis. We also identify the pteridine synthesis pathway (including genes such as qdpr and xdh) as a key driver of the variation in colour between morphs of these species, and identify several plausible candidates for colouration in vertebrates (e.g. cd36, ep‐cadherin and perlwapin). Finally, we hypothesise that keratin genes (e.g. krt8) are important for producing different structural colours within these frogs. [ABSTRACT FROM AUTHOR]

Coral reefs rank among the most diverse species assemblages on Earth. A particularly striking aspect of coral reef communities is the variety of colour patterns displayed by reef fishes. Colour pattern is known to play a central role in the ecology and evolution of reef fishes through, for example, signalling or camouflage. Nevertheless, colour pattern is a complex trait in reef fishes—actually a collection of traits—that is difficult to analyse in a quantitative and standardized way. This is the challenge that we address in this study using the hamlets (Hypoplectrus spp., Serranidae) as a model system. Our approach involves a custom underwater camera system to take orientation‐ and size‐standardized photographs in situ, colour correction, alignment of the fish images with a combination of landmarks and Bézier curves, and principal component analysis on the colour value of each pixel of each aligned fish. This approach identifies the major colour pattern elements that contribute to phenotypic variation in the group. Furthermore, we complement the image analysis with whole‐genome sequencing to run a multivariate genome‐wide association study for colour pattern variation. This second layer of analysis reveals sharp association peaks along the hamlet genome for each colour pattern element and allows to characterize the phenotypic effect of the single nucleotide polymorphisms that are most strongly associated with colour pattern variation at each association peak. Our results suggest that the diversity of colour patterns displayed by the hamlets is generated by a modular genomic and phenotypic architecture. see also the Perspective by Bruno Frédérich [ABSTRACT FROM AUTHOR]

Colour pattern variation provides biological information in fields ranging from disease ecology to speciation dynamics. Comparing colour pattern geometries across images requires colour segmentation, where pixels in an image are assigned to one of a set of colour classes shared by all images. Manual methods for colour segmentation are slow and subjective, while automated methods can struggle with high technical variation in aggregate image sets. We present recolorize, an R package toolbox for human‐subjective colour segmentation with functions for batch‐processing low‐variation image sets and additional tools for handling images from diverse (high‐variation) sources. The package also includes export options for a variety of formats and colour analysis packages. This paper illustrates recolorize for three example datasets, including high variation, batch processing and combining with reflectance spectra, and demonstrates the downstream use of methods that rely on this output. [ABSTRACT FROM AUTHOR]

Polyene pigments represent a major class of pigments in present‐day organisms. Their occurrence in fossils has been frequently discussed, but to date no spectroscopic evidence has been found. Here, we use in situ Raman spectroscopy to examine the chemistry of exceptionally well‐preserved gastropod shells with colour preservation from the Middle Miocene of the Vienna Basin (Austria, Hungary). Raman signals indicative of the presence of intact (i.e. non‐hydrogenated) polyene pigments were obtained from fossil shells with reddish colour patterns, thus revealing the first record of intact polyenes in fossils. The observed Raman values are in good agreement with those of unmethylated (non‐carotenoid) polyenes. Fossil polyene pigments were detected in representatives of the superfamily Cerithioidea, but not in representatives of other gastropod families with colour preservation found at the same localities, demonstrating that the occurrence of polyene pigments is taxon‐specific. Our results show that Raman spectroscopy represents a valuable tool for the non‐destructive screening of rare fossils with colour preservation for the occurrence of polyene pigments. [ABSTRACT FROM AUTHOR]

A morphometric examination of Anthrenus flavipes flavipes LeConte 1854 from Central Macedonia, Greece is carried out and compared with data from previous publications. Size ranges for both sexes are generated. Males are significantly smaller than females. The body width/body length ratio is calculated. Images of body size range, antennal club and aedeagus are provided. Elements of the elytral colour pattern are considered in the light of LeConte's original description. [ABSTRACT FROM AUTHOR]

Two species new to science Willowsia sikkimensis sp. nov. and W. arunachalensis sp. nov., and one new record of the genus Willowsia Shoebotham, 1917 are described and illustrated here. The new species are mainly distinguished from the others on the basis of pigment pattern, scale type and chaetotaxy. The species were collected from the states of Arunachal Pradesh and Sikkim (India). Willowsia shiae Pan, Zhang & Chen, 2006 is recorded for the first time from India (Arunachal Pradesh) and redescribed with detailed chaetotaxic nomenclature. A key to the Indian species of Willowsia and a comparison table of related species are also provided.

Many fossil insects show monochromatic colour patterns that may provide valuable insights into ancient insect behaviour and ecology. Whether these patterns reflect original pigmentary coloration is, however, unknown, and their formation mechanism has not been investigated. Here, we performed thermal maturation experiments on extant beetles with melanin-based colour patterns. Scanning electron microscopy reveals that melanin-rich cuticle is more resistant to degradation than melanin-poor cuticle: with progressive maturation, melanin-poor cuticle regions experience preferential thinning and loss, yet melanin-rich cuticle remains. Comparative analysis of fossil insects with monotonal colour patterns confirms that the variations in tone correspond to variations in preserved cuticle thickness. These preserved colour patterns can thus be plausibly explained as melanin-based patterning. Recognition of melanin-based colour patterns in fossil insects opens new avenues for interpreting the evolution of insect coloration and behaviour through deep time. [ABSTRACT FROM AUTHOR]

A common goal in evolutionary biology is to discern the mechanisms that produce the astounding diversity of morphologies seen across the tree of life. Aposematic species, those with a conspicuous phenotype coupled with some form of defence, are excellent models to understand the link between vivid colour pattern variations, the natural selection shaping it, and the underlying genetic mechanisms underpinning this variation. Mimicry systems in which multiple species share the same conspicuous phenotype can provide an even better model for understanding the mechanisms of colour production in aposematic species, especially if comimics have divergent evolutionary histories. Here we investigate the genetic mechanisms by which vivid colour and pattern are produced in a Müllerian mimicry complex of poison frogs. We did this by first assembling a high-quality de novo genome assembly for the mimic poison frog Ranitomeya imitator. This assembled genome is 6.8 Gbp in size, with a contig N50 of 300 Kbp R. imitator and two colour morphs from both Ranitomeya fantastica and R. variabilis which R. imitator mimics. We identified a large number of pigmentation and patterning genes that are differentially expressed throughout development, many of them related to melanocyte development, melanin synthesis, iridophore development and guanine synthesis. Polytypic differences within species may be the result of differences in expression and/or timing of expression, whereas convergence for colour pattern between species does not appear to be due to the same changes in gene expression. In addition, we identify the pteridine synthesis pathway (including genes such as qdpr and xdh) as a key driver of the variation in colour between morphs of these species. Finally, we hypothesize that genes in the keratin family are important for producing different structural colours within these frogs.

Parauchenoglanis zebratus sp. nov. is a new species endemic to the Upper Lualaba in the Upper Congo Basin. It is distinguished from all its congeners known from the Congo Basin and adjacent basins by the presence of (1) distinctive dark‐brown or black vertical bars on the lateral side of the body, at least for specimens about ≥120 mm LS, (2) a broad and triangular humeral process embedded under the skin and (3) a well‐serrated pectoral‐fin spine. Genetic analysis based on mtDNA COI sequences confirmed the genetic distinctiveness (2.8%–13.6% K2P genetic divergence) of P. zebratus sp. nov. from congeners within the Congo and adjacent river basins. The study also revealed additional undocumented diversity within P. ngamensis, P. pantherinus, P. punctatus and P. balayi, indicating the need for further in‐depth alpha‐taxonomic attention to provide more accurate species delimitations for this genus. The discovery of yet another new species endemic to the Upper Lualaba, and this well outside the currently established protected areas, highlights the critical need for further assessments to accurately document the species diversity to guide freshwater conservation prioritisation and biodiversity management in this region. [ABSTRACT FROM AUTHOR]

The article presents preliminary results of study of the colour pattern variability of mottled scorpion Mesobuthus eupeus (C.L. Koch, 1839) in habitats of the eastern part of Azerbaijan. The studies were carried out on the basis of material from five samples taken in the southeastern part of the Shirvan Plain, northwestern, northeastern, central and southeastern Gobustan. The colouration of the mottled scorpion is a complex of multi-element characters, which includes the colour and pattern of the dorsal and ventral surfaces of the body. When studying the material, the general colour of background of the body and individual elements of the pattern of the dorsal surface of the mesosome, medial, paramedial and marginal longitudinal stripes, transverse stripes and pigmented areas (spots), were mainly taken into account. Most specimens in samples had all or only part of the pattern elements, the variability of a combination of which led to the formation of a wide variety of colour options. In about 1.2% of specimens, the absence of pattern elements was noted. According to the totality of features (pattern elements) of the dorsal surface of the mesosome, all variable specimens of M. eupeus in the studied material were grouped into 11 morphs, each of which had from 2 to 8 (54 in total) colour aberrations. The frequencies of the variability of the main elements of the pattern were in the range of 0.33–0.84. The relative pigmentation index used to quantify the level of pigment on the mesosomal segments also varied widely (0–0.89; M = 0.36). The polymorphism of colouration and colour pattern of the mottled scorpion, presumably, is the result of adaptation of the species to microbiotopic conditions in habitats in each conglomeration by changing the ratio between the phenotypes presented in them. The manifestation of polymorphism in the colour pattern of the mottled scorpion in a relatively small area can be explained by the spatial differentiation of different types of habitats due to the heterogeneity of a landscape.

Sensory drive proposes that natural selection on nonmating behaviours (e.g. foraging preferences) alters sensory system properties and results in a correlated effect on mating preferences and subsequently sexual traits. In colour-based systems, we can test this by selecting on nonmating colour preferences and testing for responses in colour-based female preferences and male sexual coloration. In guppies (Poecilia reticulata), individual functional links of sensory drive have been demonstrated providing an opportunity to test the process over more than one link. We measured male coloration and female preferences in populations previously artificially selected for colour-based foraging behaviour towards two colours, red and blue. We found associated changes in male coloration in the expected direction as well as weak changes in female preferences. Our results can be explained by a correlated response in female preferences due to artificial selection on foraging preferences that are mediated by a shared sensory system or by other mechanisms such as colour avoidance, pleiotropy or social experiences. This is the first experimental evidence that selection on a nonmating behaviour can affect male coloration and, more weakly, female preferences.

A young female puff adder (Bitis arietans) with an unusual 'speckled' colour pattern was recently found in Bloemfontein, central South Africa. The snake was grey‐brown dorsally with numerous scattered dark markings and very occasional pale flecks, but it lacked the backwards‐pointing, dark‐edged, pale chevrons that characterise this common, widespread and highly venomous species. It also lacked any stripes or bands, but the head was lightly patterned. Although various rare colour morphs have been reported for this species, this is the first record of a puff adder with a 'speckled' dorsal pattern. [ABSTRACT FROM AUTHOR]

In animals, changes in colour pigmentation in an intraspecific context are usually described as a polymorphism adaptive to environmental factors. According to the thermal melanism hypothesis (TMH), melanic individuals are more active because they may attain higher temperature and then benefit from higher size, foraging time and reproduction. The polymorphic seed‐beetle Acanthoscelides quadridentatus (Coleoptera: Chrysomelidae) naturally attacks the seeds of two plant varieties, Mimosa setosa var. paludosa and M. setosa var. setosa, in the Brazilian savanna.The authors tested TMH in this system, predicting that melanic beetles would be larger, and infringe worst germination rate and higher seed mortality. Additionally, they tested whether seed weight plays a role in germination.The authors found two beetle morphs: a melanic/1.1‐fold larger and another lighter/smaller. Seeds of M. setosa var. setosa are 1.9‐fold heavier and its intact seeds germinate faster and with a higher amount than the seeds of M. setosa var. paludosa. There is no difference in the attack rate by beetle morphs. The attacked seeds of both plant varieties did not germinate.The authors evidence phenotypic plasticity in A. quadridentatus, highlighting that TMH is confirmed for the relationship between melanism and larger sizes, although there was no difference in foraging of melanic individuals. This study shed light on the importance of plant varieties in driving the morphology of seed‐beetles. [ABSTRACT FROM AUTHOR]

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UV light‐induced fluorescence is widely used as a key to reveal residual shell colour patterns of Neogene and Palaeogene molluscs. However, only few examples of fluorescent colour patterns are known from Mesozoic marine shells and little is known about the nature of fluorescence in fossils. Here, UV light‐induced fluorescence reveals previously unseen abundance and diversity in the colour patterns of the basal pectinid Pleuronectites laevigatus from the Middle Triassic Muschelkalk of Central Europe. In addition to known variations of radial bands, a multitude of zigzag and zigzag‐related patterns was found. The diversity of colour patterns is comparable to modern pectinids and is interpreted as colour pattern polymorphism. Raman spectra of the colour patterns indicated the preservation of residual organic pigments with aromatic moieties. The fluorescence properties of P. laevigatus and other basal pectinids from the Muschelkalk of Germany and France are described in detail, suggesting that colour pattern fluorescence is due to colourless diagenetic products of the pigments, not to the fossil pigments themselves. A remarkable feature of the colour patterns of P. laevigatus is the presence of different fluorescence colours. Because a gradual shift of the fluorescence colour from yellow to red with decreasing intensity to finally non‐fluorescent is observed, which correlates with the provenance of the specimens, the fluorescence properties are interpreted to reflect differences in diagenetic history. The results show that the fluorescence colour of fossil molluscs, especially of Mesozoic molluscs, may be affected by diagenesis and should only be used with caution for taxonomic purposes. [ABSTRACT FROM AUTHOR]

From feather and hair dotted arrays to pigmented stripes and spots, the spatial distribution of skin appendages and colouration often forms visible ornaments crucial for fitness in the coat of birds and mammals. These geometrical motifs are extremely diverse in nature. Yet, phenotypic surveys evidenced common themes in variation: the orientation, appendage-specificity or pigmentation of a given region may be conserved across groups or species. Here, we review naturalist observations of natural variation in the anatomy and ecological function of the skin pattern in amniotes. We then describe several decades of genetics, mathematical modelling and experimental embryology work aiming at understanding the molecular and morphogenetic mechanisms responsible for pattern formation. We discuss how these studies provided evidence that the morphological trends and differences representative of the phenotypic landscape of skin patterns in wild amniote species is rooted in the mechanisms controlling the production of distinct compartments in the embryonic skin., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The geographic variability of the dorsal pattern (DP) of the Italian wall lizard, Podarcis siculus, across its native range was studied with the aim of understanding whether the distributions of this phenotypic trait were more shaped by allopatric differentiation rather than adaptive processes. A total of 1298 georeferenced observations scattered across the Italian peninsula and the main islands (Sicily, Corsica and Sardinia) were obtained from citizen science databases and five DPs were characterized by different shapes of the dark pattern ("reticulated", "campestris", "reticulated/campestris" and "striped") or by absence of it ("concolor"). Frequencies of different DP phenotypes differ between the two main mtDNA lineages settled in central-northern and in southern Italy, respectively. This pattern may be indicative of a role of long-term allopatric historical processes in determining the observed pattern. The analysis also identified a putative wide area of secondary contact, in central southern Italy, characterized by high diversity of the DP. Generalized Linear Models (GLMs), used to estimate a possible association between bioclimatic variables and the observed phenotypic variation, showed that each of the five DPs is correlated to different environmental factors and show a different distribution of areas with high probability of occurrence. However, for all but one of the DPs, the area with the greatest probability does not correspond exactly to the real distribution of the DP. Conversely, the "concolor" phenotype does not seem related to any particular mtDNA lineage and it shows a preference for areas with high temperature and low rainfall. This is in agreement with the expectation of low amount of melanin of the dorsal pattern that, in the study areas, is characterized by a light uniform coloration which could confer a better thermoregulation ability in high temperatures environments to avoid overheating. [ABSTRACT FROM AUTHOR]

The Orchidaceae is characterised by the repeated evolution of sexual deception, one of the most specialised pollination strategies. In orchids, sexual deception involves long-range pollinator attraction via mimicry of female insect sex pheromones. At close range, visual signals involving colour mimicry, contrast to the background, and exploitation of pollinator sensory biases could attract pollinators, but remain largely untested. Here we focus on a remarkable system in which species from two only distantly related sexually deceptive orchid genera with strikingly different flowers (Drakaea livida and three species of Caladenia) share the same pollinator, males of the thynnine wasp Zaspilothynnus nigripes. We used spectral reflectance measurements and modelling to investigate pollinator perception of colour, including the first examination of overall colour patterns in flowers via colour pattern geometry analyses. Rather than closely matching the colours of female Z. nigripes, these orchids had strong chromatic and achromatic contrast against their backgrounds. For Caladenia, the sepals and petals show high contrast, while in D. livida, which has diminutive petals and sepals, it is the labellum that contrasts strongly against the background. Despite varying in colour, the Caladenia species all had strong within-flower contrast between a UV-bright central target (column and labellum) and a corolla of radiating stripes (petals and sepals). The colour pattern geometry analyses also indicated that the orchids’ overall colour patterns are highly conspicuous against their backgrounds. Contrast, UV, and target patterns could all enhance detection, and exploit pollinators’ innate preferences. Since colour contrast may function with a range of colours and floral forms, attracting pollinators via contrast rather than visual mimicry may be a critical but previously overlooked process facilitating the evolution of sexual deception.

1. A mimetic complex of red‐and‐black insects is proposed to occur in Central Europe. 2. In our study, we tested in isolation the importance of a colour pattern as the main factor responsible for the predator avoidance of the members of this putative mimetic complex by transferring the patterns of seven European red‐and‐black insects onto a palatable prey using paper stickers. Wild‐caught adult great tits (Parus major) were used as the predators. 3. In general, the response of the tested birds to palatable prey carrying a conspicuous pattern differed from their responses to the real insect species demonstrated in previous studies. 4. The birds avoided the pattern of Pyrrhocoris apterus most often, putatively because of their rich individual experience with the real insect from the wild, since it is the most common amongst our chosen species. Other patterns were attacked similarly to the control, inconspicuous roach pattern. Obviously, these patterns did not discourage the birds from making a closer inspection of the offered prey and revealing the edible cockroach hidden underneath the coloured paper sticker. 5. We show that the method of transferring aposematic colour patterns to edible prey has substantial limitations when testing how predators generalise colour patterns within the mimetic complex. [ABSTRACT FROM AUTHOR]

Research on animal colouration has grown exponentially in the last decade thanks to multidisciplinary approaches. Most studies are focused on trade-offs between communication and mimicry, which represent the two main constraints and drivers of the evolution of body colourations. Reptiles are excellent model species for investigating this field of study and lizards in particular show great variability of body colourations and their functions. We studied the lizard Podarcis siculus, analysing the variations of dorsal colour of three populations and obtained clear patterns of seasonal and ontogenetical variation of dorsal colour. According to baseline colour, males were greener and brighter than females, although no difference in saturation was recorded. According to seasonal variations, analyses showed that both sexes significantly vary in colour over the year: males reached higher peaks of hue and saturation later than females during spring, while females showed higher peaks of brightness and reached earlier similarly to hue and saturation. Ontogenetic variations were recorded only in males, which become greener, less bright and saturated with growing size. Therefore, our results suggest the occurrence of two opposing strategies in colour expression between sexes: males’ dorsal colouration plays a major role in communication, while females are more crypsis-oriented.

Animal colour patterns remain a lively focus of evolutionary and behavioural ecology, despite the considerable conceptual and technical developments over the last four decades. Nevertheless, our current understanding of the function and efficacy of animal colour patterns remains largely shaped by a focus on stationary animals, typically in a static background. Yet, this rarely reflects the natural world: most animals are mobile in their search for food and mates, and their surrounding environment is usually dynamic. Thus, visual signalling involves not only animal colour patterns, but also the patterns of animal motion and behaviour, often in the context of a potentially dynamic background. While motion can reveal information about the signaller by attracting attention or revealing signaller attributes, motion can also be a means of concealing cues, by reducing the likelihood of detection (motion camouflage, motion masquerade and flicker-fusion effect) or the likelihood of capture following detection (motion dazzle and confusion effect). The interaction between the colour patterns of the animal and its local environment is further affected by the behaviour of the individual. Our review details how motion is intricately linked to signalling and suggests some avenues for future research. This Review has an associated Future Leader to Watch interview with the first author.

Callaspidia is a Holarctic genus; some species of Callaspidia attack the larvae of order Diptera and Coleoptera. Callaspidia notata (Boyer de Fonscolombe, 1832) (Hymenoptera: Figitidae: Aspicerinae) is reported with colour variations like scape, pedicel and basal part of antennal segment 3 slightly darker than remaining segments, scutellum and mesopleura mostly dark reddish with some darker areas, legs also reddish brown except tarsal segments lighter in colouration. Suspected trophic associations with Ischiodon scutellaris (F.) via Aphis nerii on Calotropis procera (Ait.) Ait and Tinocallis kahawaluokalani (Kirkaldy) on Lagerstroemia indica have been given. Studies suspected that C. notata parasitizes the immature of Ischiodon scutellaris (F.) like other reported species of this genus. Main diagnostic characters, brief description, morphometrics and illustrations are provided. Comparison of recorded species with type species has been provided. World distribution and distribution in Pakistan has been given using Arc GIS tools. [ABSTRACT FROM AUTHOR]

Abstract Background Elevated water temperature, as is expected through climate change, leads to masculinization in fish species with sexual plasticity, resulting in changes in population dynamics. These changes are one important ecological consequence, contributing to the risk of extinction in small and inbred fish populations under natural conditions, due to male-biased sex ratio. Here we investigated the effect of elevated water temperature during embryogenesis on sex ratio and sex-biased gene expression profiles between two different tissues, namely gonad and caudal fin of adult zebrafish males and females, to gain new insights into the molecular mechanisms underlying sex determination (SD) and colour patterning related to sexual attractiveness. Results Our study demonstrated sex ratio imbalances with 25.5% more males under high-temperature condition, resulting from gonadal masculinization. The result of transcriptome analysis showed a significantly upregulated expression of male SD genes (e.g. dmrt1, amh, cyp11c1 and sept8b) and downregulation of female SD genes (e.g. zp2.1, vtg1, cyp19a1a and bmp15) in male gonads compared to female gonads. Contrary to expectations, we found highly differential expression of colour pattern (CP) genes in the gonads, suggesting the ‘neofunctionalisation’ of those genes in the zebrafish reproduction system. However, in the caudal fin, no differential expression of CP genes was identified, suggesting the observed differences in colouration between males and females in adult fish may be due to post-transcriptional regulation of key enzymes involved in pigment synthesis and distribution. Conclusions Our study demonstrates male-biased sex ratio under high temperature condition and support a polygenic SD (PSD) system in laboratory zebrafish. We identify a subset of pathways (tight junction, gap junction and apoptosis), enriched for SD and CP genes, which appear to be co-regulated in the same pathway, providing evidence for involvement of those genes in the regulation of phenotypic sexual dimorphism in zebrafish.

The geographic variability of the dorsal pattern (DP) of the Italian wall lizard, Podarcis siculus, across its native range was studied with the aim of understanding whether the distributions of this phenotypic trait were more shaped by allopatric differentiation rather than adaptive processes. A total of 1298 georeferenced observations scattered across the Italian peninsula and the main islands (Sicily, Corsica and Sardinia) were obtained from citizen science databases and five DPs were characterized by different shapes of the dark pattern (“reticulated”, “campestris”, “reticulated/campestris” and “striped”) or by absence of it (“concolor”). Frequencies of different DP phenotypes differ between the two main mtDNA lineages settled in central-northern and in southern Italy, respectively. This pattern may be indicative of a role of long-term allopatric historical processes in determining the observed pattern. The analysis also identified a putative wide area of secondary contact, in central southern Italy, characterized by high diversity of the DP. Generalized Linear Models (GLMs), used to estimate a possible association between bioclimatic variables and the observed phenotypic variation, showed that each of the five DPs is correlated to different environmental factors and show a different distribution of areas with high probability of occurrence. However, for all but one of the DPs, the area with the greatest probability does not correspond exactly to the real distribution of the DP. Conversely, the “concolor” phenotype does not seem related to any particular mtDNA lineage and it shows a preference for areas with high temperature and low rainfall. This is in agreement with the expectation of low amount of melanin of the dorsal pattern that, in the study areas, is characterized by a light uniform coloration which could confer a better thermoregulation ability in high temperatures environments to avoid overheating.

Sexual dimorphism is a major component of morphological variation across the tree of life, but the mechanisms underlying phenotypic differences between sexes of a single species are poorly understood. We examined the population genomics and biogeography of the common palmfly Elymnias hypermnestra, a dual mimic in which female wing colour patterns are either dark brown (melanic) or bright orange, mimicking toxic Euploea and Danaus species, respectively. As males always have a melanic wing colour pattern, this makes E. hypermnestra a fascinating model organism in which populations vary in sexual dimorphism. Population structure analysis revealed that there were three genetically distinct E. hypermnestra populations, which we further validated by creating a phylogenomic species tree and inferring historical barriers to gene flow. This species tree demonstrated that multiple lineages with orange females do not form a monophyletic group, and the same is true of clades with melanic females. We identified two single nucleotide polymorphisms (SNPs) near the colour patterning gene WntA that were significantly associated with the female colour pattern polymorphism, suggesting that this gene affects sexual dimorphism. Given WntA’s role in colour patterning across Nymphalidae, E. hypermnestra females demonstrate the repeatability of the evolution of sexual dimorphism. [ABSTRACT FROM AUTHOR]

Characidium pumarinri n. sp. is described from the affluents of Río Huallaga, a tributary of Río Marañón that drains the eastern slopes of the Andes, in the Peruvian Amazon. The new species has a deep body (24–31% in LS), 11–17 well‐marked dark bars and remarkable sexual dimorphism related to colour pattern, in which males have darker anal, dorsal, pectoral and pelvic fins than females. C. pumarinri resembles some species allocated in Clade C4, mainly by having a high number of transversal bars and a deep body. In addition, a thorough review and further descriptions of the secondary sexual characteristics in Characidium are provided. [ABSTRACT FROM AUTHOR]

Colour pattern influences behaviour and affects survival of organisms through perception of light reflectance. Spectrophotometric methods used to study colour optimise precision and accuracy of reflectance across wavelengths, while multiband photographs are generally used to assess the complexity of colour patterns. Using standardised photographs of sand lizards (Lacerta agilis), we compare how colours characterised using point measurements (using the photographs, but simulating spectrophotometry) on the skin differ from colours estimated by clustering pixels in the photograph of the lizard's body. By taking photographs in the laboratory and in the field, the experimental design included two 2-way comparisons. We compare point vs. colour clustering characterisation and influence of illumination in the laboratory and in the field. We found that point measurements adequately represented the dominant colour of the lizard. Where colour patterning influenced measurement geometry, image analysis outperformed point measurement with respect to stability between technical replicates on the same animal. The greater colour variation derived from point measurements increased further under controlled laboratory illumination. Both methods revealed lateral colour asymmetry in sand lizards, i.e. that colours subtly differed between left and right flank. We conclude that studies assessing the impact of colour on animal ecology and behaviour should utilise hyperspectral imaging, followed by image analysis that encompasses the whole colour pattern. [ABSTRACT FROM AUTHOR]

Hybridization can generate novel phenotypes distinct from those of parental lineages, a phenomenon known as transgressive trait variation. Transgressive phenotypes might negatively or positively affect hybrid fitness, and increase available variation. Closely related species of Heliconius butterflies regularly produce hybrids in nature, and hybridization is thought to play a role in the diversification of novel wing colour patterns despite strong stabilizing selection due to interspecific mimicry. Here, we studied wing phenotypes in first‐ and second‐generation hybrids produced by controlled crosses between either two co‐mimetic species of Heliconius or between two nonmimetic species. We quantified wing size, shape and colour pattern variation and asked whether hybrids displayed transgressive wing phenotypes. Discrete traits underlain by major‐effect loci, such as the presence or absence of colour patches, generate novel phenotypes. For quantitative traits, such as wing shape or subtle colour pattern characters, hybrids only exceed the parental range in specific dimensions of the morphological space. Overall, our study addresses some of the challenges in defining and measuring phenotypic transgression for multivariate traits and our data suggest that the extent to which transgressive trait variation in hybrids contributes to phenotypic diversity depends on the complexity and the genetic architecture of the traits. [ABSTRACT FROM AUTHOR]

A new species of Trichomycterus endemic to the Ribeira de Iguape River basin, southeastern Brazil, was studied based on morphological and molecular evidence. This species had an outer layer of coloration composed of scattered, round, black or dark‐brown spots smaller or equivalent in size to the circumference of the eye; eight pectoral‐fin rays; 28–29 opercular odontodes; 54–56 interopercular odontodes; and supraorbital line of the laterosensory system not interrupted, with pores s2 absent. Two other species of Trichomycterus from the Ribeira de Iguape River basin are recorded, and their taxonomic status is discussed: Trichomycterus alternatus and Trichomycterus jacupiranga were not differentiated using molecular analysis but may be consistently distinguished based on morphology. The phylogenetic relationships of the co‐occurring species, T. alternatus and Cambeva zonata, were inferred using mitochondrial data, reinforcing the taxonomic status of these recently revised species that have a complex taxonomy. In addition, a new combination for Trichomycterus taroba with its inclusion in the genus Cambeva is recommended. [ABSTRACT FROM AUTHOR]

Ontogenetic colour change (OCC) is defined as the progressive and non-reversible process of changes in colouration of organisms associated with their development. Among the many vertebrate groups, amphibians are particularly impressive for their strikingly wide variety of colours, colour patterns, and signals, whose evolutionary and ecological significance have been poorly studied. Elachistocleis comprises 18 species currently separated into two main groups based on their ventral colour pattern: one immaculate and the other with specks and/or colour patches. Elachistocleis haroi is a small-sized species within the immaculate venter group, distributed in the Yungas and Dry Chaco ecoregions from which little information is known. In a comprehensive sampling of post-metamorphic individuals of E. haroi at different stages of development we identified a significant variation in ventral colour pattern, which could denote a progressive filling of yellow colour according to an ontogenetic pattern. To test this hypothesis, we analysed 39 post-metamorphic individuals of E. haroi at different stages of development with imaging procedures. We found that yellow spots and their intensity are significantly related to snout-vent length, as major expansion of colour on the sides, gular region and male chest, as almost no development on the belly. We briefly discuss our findings in relation to sexual display and predation avoidance. To our knowledge, this is the first analysis of post-metamorphic OCC in ventral colouration in the genus Elachistocleis. [ABSTRACT FROM AUTHOR]

Background: The geometric patterns that adorn the shells of many phylogenetically disparate molluscan species are comprised of pigments that span the visible spectrum. Although early chemical studies implicated melanin as a commonly employed pigment, surprisingly little evidence generated with more recent and sensitive techniques exists to support these observations. Results: Here we present the first mass spectrometric investigations for the presence of eumelanin and pheomelanin in 13 different molluscan species from three conchiferan classes: Bivalvia, Cephalopoda and Gastropoda. In the bivalve Mytilus edulis we demonstrate that eumelanin mainly occurs in the outermost, non-mineralised and highly pigmented layer of the shell (often referred to as the periostracum). We also identified eumelanin in the shells of the cephalopod Nautilus pompilius and the marine gastropods Clanculus pharaonius and Steromphala adriatica. In the terrestrial gastropod Cepaea nemoralis we verify the presence of pheomelanin in a mollusc shell for the first time. Surprisingly, in a large number of brown/black coloured shells we did not find any evidence for either type of melanin. Conclusions: We recommend methods such as high-performance liquid chromatography with mass spectrometric detection for the analysis of complex biological samples to avoid potential false-positive identification of melanin. Our results imply that many molluscan species employ as yet unidentified pigments to pattern their shells. This has implications for our understanding of how molluscs evolved the ability to pigment and pattern their shells, and for the identification of the molecular mechanisms that regulate these processes. [ABSTRACT FROM AUTHOR]

The arrangements of flowers and wine counterparts are inextricably linked. Whether a fundamental aspect of tablescaping or acolytes to broader entertainment rituals, they have an interlaced history since ancient times. The aim of this contribution is twofold: first, we seek to understand how the colour composition pattern of flower arrangements (e.g., value, saturation, and temperature) influence the subjects' perception of flower arrangements' delicacy or robustness. Second, we aim to verify the influence of visually delicate and robust flower arrangements on individual judgment of wines. Forty-one subjects evaluated the delicacy and robustness of eight flower arrangements with different colour composition patterns in an online environment. Results showed that analogous flower arrangements that combined flowers with high value, low saturation, and cool temperature were perceived as more delicate than the analogous flower arrangements that combined flowers with low value, high saturation, and warm temperature. The latter were perceived as more robust. Subsequently, sensory descriptions and hedonic judgments of wines were investigated during subjects' exposure to three different conditions: the presence of delicate , robust, or totally absent flower arrangements. In each condition, two wines were tasted blind: a wine previously defined as delicate – a Pinot Noir from Australia, and a wine known for its robust character – a Tannat from Uruguay. Results showed that both wines were perceived as being more delicate when tasted in presence of the ' delicate ' flower arrangement (compared to ' robust ' or 'no' arrangements). There was, however, no interaction effect between type of wine and flower arrangement. Despite this lack of interaction, Tannat wines were clustered together with Pinot Noir wines, when tasted in the presence of the delicate flower arrangement and were described as more delicate than when the same wine was tasted in the control room (no flowers present), suggesting a visual-mouthfeel cross modality effect. The results of this investigation could help event organisers (i.e., weddings and the entertainment-related sector), as well as wine lovers in general, consider the style of wines and how they combined with the colour characteristics of flower arrangements during tablescaping. • The crossmodal effect of flower arrangements on the perception of wines was studied. • Analogous colour scheme influence the perception of delicacy and robustness of flower arrangements. • Wines were perceived as more delicate when tasted in front of delicate flowers. • Wines were also described using 'delicate' descriptors in the presence of flowers. • Pairing of wine styles and flower arrangements should be considered in events and marketing. [ABSTRACT FROM AUTHOR]

In many butterfly species, the posterior end of the hindwings of individuals perching with their wings closed resembles a butterfly head. This “false head” pattern is considered an adaptation to deflect predator attacks to less vulnerable parts of the body. The presence of symmetrical damage in left and right wings is considered evidence of failed predator attacks to perching butterflies. In this research, we tested the prediction derived from the deflection hypothesis that the degree of resemblance of the false head area (FH) to a real head, as measured by the number of FH “components” (eyespots, “false antennae”, modified outline of the FH area and lines converging on the FH area) present in the hindwings, is positively correlated to the frequency of symmetrical damage in the FH area. We studied specimens from two scientific collections of butterflies of the subfamily Theclinae (Lycaenidae) belonging to the Universidad Nacional Autónoma de México (Colección Nacional de Insectos [CNIN] and Museo de Zoología, Facultad de Ciencias [MZFC]). We scored the presence of symmetrical damage in a sample of 20,709 specimens (CNIN: 3,722; MZFC: 16,987) from 126 species (CNIN: 78 species; MZFC: 117 species; 71 species shared by both collections) whose hindwings vary in the number of FH components, and found that, as predicted, the proportion of specimens with symmetrical damage increases as the number of FH components increases. We also tested the hypothesis that behavioural differences between the sexes makes males more prone to receive predator attacks and, thus, we predicted a higher frequency of symmetrical damage in the FH of males than in that of females. We found that the frequency of symmetrical damage was not significantly different between males and females, suggesting that behavioural differences between the sexes produce no differences in the risk of being attacked. Overall, our results provide support to the idea that the FH of butterflies is an adaptation that deflects predator attacks to less vulnerable parts of the body in both sexes.

Heliconius butterflies are well-known for their colourful wing patterns, which advertise distastefulness to potential predators and are used during mate choice. However, the relative importance of different aspects of these signals will depend on the visual abilities of Heliconius and their predators. Previous studies have investigated colour sensitivity and neural anatomy, but visual acuity (the ability to perceive detail) has not been studied in these butterflies. Here, we provide the first estimate of visual acuity in Heliconius : from a behavioural optomotor assay, we found that mean visual acuity = 0.49 cycles-per-degree (cpd), with higher acuity in males than females. We also examined eye morphology and report more ommatidia in male eyes. Finally, we estimated how visual acuity affects Heliconius visual perception compared to a potential avian predator. Whereas the bird predator maintained high resolving power, Heliconius lost the ability to resolve detail at greater distances, though colours may remain salient. These results will inform future studies of Heliconius wing pattern evolution, as well as other aspects in these highly visual butterflies, which have emerged as an important system in studies of adaptation and speciation.

The study analyzed the live colour pattern present on the carapace of Portunus pelagicus. Our results indicated that the occurrence of three major colour morphs in the population of P. pelagicus with an intraspecific variation among the female population in Mandapam (Palk Bay and Gulf of Mannar) region. The crab population was dominated by carapace colour morph Type 2 (51.27%) in Palk Bay and Type 3 (54.80%) in Gulf of Mannar. There was no evidence of a colour morph difference between ages in observed specimens. The colour morphotypes showed significant difference in the analysed population, among and between the sexes. [ABSTRACT FROM AUTHOR]

Bombus bicoloratus is an important pollinator of wild flowers in the oriental region. We confirmed a total of 451 specimens of B. bicoloratus from China based on DNA sequences from mitochondrial cytochrome oxidase subunit I (COI) barcodes. Bombus bicoloratus is distributed mainly in tropical and subtropical areas of southern China. This species exhibits a striking intraspecific colour-pattern polymorphism both in females and males. The distribution frequency of the different colour patterns is heavily skewed, with 50.9% of the workers sharing the same colour pattern that predominates in most locations. Workers from the islands of Hainan and Taiwan possess a very distinct colour pattern, and its spatial distribution is correlated with the climate factor irradiance. Bombus bicoloratus has been recorded to collect nectar and pollen from 14 plant families, indicating that this species is polylectic. This study will be helpful for recognising bumblebee species with variable colour patterns, especially B. bicoloratus, in Asia. [ABSTRACT FROM AUTHOR]

Many studies have shown that speciation can be facilitated when a trait under divergent selection also causes assortative mating. In Müllerian mimetic butterflies, a change in wing colour pattern can cause reproductive isolation. However, colour pattern divergence does not always lead to reproductive isolation. Understanding how divergent selection affects speciation requires identifying the mechanisms that promote mate preference and/or choosiness.This study addresses whether shifts in wing colour pattern drives mate preference and reproductive isolation in the tropical butterfly genus Melinaea (Nymphalidae: Ithomiini), and focuses on five taxa that form a speciation continuum, from subspecies to fully recognized species.Using genetic markers, wing colour pattern quantification, male pheromone characterization and behavioural assays of mating preference, we characterize the extent of genetic and phenotypic differentiation between taxa and compare it to the level of reproductive isolation.We show strong premating isolation between the closely related species M. satevis and M. marsaeus, in addition to genetic and phenotypic (colour pattern and pheromones) differentiation. By contrast, M. menophilus and M. marsaeus consist of pairs of subspecies that differ for colour pattern but that cannot be differentiated genetically. Pheromonal differentiation of subspecies was significant only for M. marsaeus, although most individuals were indistinguishable. Melinaea menophilus and M. marsaeus also differ in the strength of assortative mating, suggesting that mate preference has evolved only in M. marsaeus, consistent with selection against maladaptive offspring, as subspecific 'hybrids' of M. marsaeus have intermediate, non‐mimetic colour patterns, unlike those of M. menophilus which display either parental phenotypes.We conclude that a shift in colour pattern per se is not sufficient for reproductive isolation, but rather, the evolution of assortative mating may be caused by selection against maladaptive intermediate phenotypes. This study suggests that mate preference and assortative mating evolve when adaptive, and that even in the early stages of divergence, reproductive isolation can be nearly complete due to mating preferences. [ABSTRACT FROM AUTHOR]

Three new species of snapping shrimps of the genus Alpheus are described from the Persian Gulf. These belong to the Alpheus edwardsii species-group, which is mainly characterized by unarmed orbital hoods and the presence of dorsal and ventral notches on the palm of the major chela. Alphus ankeri sp. nov. shows a close affinity to A. pacificus Dana, 1852 and A. heronicus Banner & Banner, 1982 bearing no balaeniceps crests in both sexes on the dactylus of the minor chela, and the merus of the major chela of both sexes are unarmed. This species differs from the closely related species by the absence of an overhanging proximal shoulder in the major chela. The other rock crevice inhabiting species, A. mohammadpouri sp. nov. is diagnosed by exhibiting sexual dimorphism in its balaeniceps crests and the armed merus of the major chela. These two characters are similar to those recorded for three sandy/rubble dwelling species: A. inopinatus Holthuis & Gottlieb, 1958, A. lobidens De Haan, 1849 and A. australiensis Banner & Banner, 1982. This new species is distinguishable from these latter species by the shape of the minor chela and colour pattern. A coral inhabiting species A. abumusa sp. nov. appears to be closely related to A. maindroni Coutière, 1898, showing an armed merus of the major chela and the absence of spine-like seta on the ischia of the third legs. This last new species is easily discriminated from A. maindroni by longer antennular segments, a markedly concave frontal margin between the rostrum and orbital hood, and a different colour pattern. [ABSTRACT FROM AUTHOR]

In many butterfly species, the posterior end of the hindwings of individuals perching with their wings closed resembles a butterfly head. This ``false head' pattern is considered an adaptation to deflect predator attacks to less vulnerable parts of the body. The presence of symmetrical damage in left and right wings is considered evidence of failed predator attacks to perching butterflies. In this research, we tested the prediction derived from the deflection hypothesis that the degree of resemblance of the false head area (FH) to a real head, as measured by the number of FH ``components' (eyespots, ``false antennae', modified outline of the FH area and lines converging on the FH area) present in the hindwings, is positively correlated to the frequency of symmetrical damage in the FH area. We studied specimens from two scientific collections of butterflies of the subfamily Theclinae (Lycaenidae) belonging to the Universidad Nacional Autónoma de México (Colección Nacional de Insectos [CNIN] and Museo de Zoología, Facultad de Ciencias [MZFC]). We scored the presence of symmetrical damage in a sample of 20,709 specimens (CNIN: 3,722; MZFC: 16,987) from 126 species (CNIN: 78 species; MZFC: 117 species; 71 species shared by both collections) whose hindwings vary in the number of FH components, and found that, as predicted, the proportion of specimens with symmetrical damage increases as the number of FH components increases. We also tested the hypothesis that behavioural differences between the sexes makes males more prone to receive predator attacks and, thus, we predicted a higher frequency of symmetrical damage in the FH of males than in that of females. We found that the frequency of symmetrical damage was not significantly different between males and females, suggesting that behavioural differences between the sexes produce no differences in the risk of being attacked. Overall, our results provide support to the idea that the FH of butterflies is an adaptation that deflects predator attacks to less vulnerable parts of the body in both sexes. [ABSTRACT FROM AUTHOR]

The longitudinal colour pattern – an adaptively controlled feature functioning in cephalopods as camouflage – is described in two straight-shelled cephalopods from the Silurian of Gotland. A shell of the orthocerid Dawsonoceras annulatum (Sowerby) exhibits relatively broad longitudinal colour bands around the entire shell circumference, which in combination with transverse annuli and undulated growth ridges form a visually reticulate ornament. Such a combination is not known in other Silurian straight-shelled cephalopods. Dawsonoceras annulatum is the only known Palaeozoic cephalopod retaining an almost identical colour pattern in populations inhabiting different palaeo-continents. The shell of the pseudorthocerid Lyecoceras? columnare (Marklin) has densely packed narrow longitudinal colour bands on the entire smooth shell. In this feature the species is very similar to other Silurian and Ordovician pseudorthocerids. However, in Ordovician pseudorthocerids colour bands are restricted dorsally. The type of colouration described herein differs from that of Devonian and younger pseudorthocerids where the shell bears zig-zag bands. Longitudinal colouration around the entire shell circumference supports vertical or subvertical life orientation in both described species.