Body Color Research Articles

Staging of post-settlement growth in the nudibranch Hypselodoris festiva

Sea slugs of the family Chromodorididae (Nudibranchia, Gastropoda, Mollusca) have garnered attention by researchers and hobbyists alike for their bright and variable color patterns. However, the chromodorid life cycle has yet to be fully elucidated as there exist no reports of their rearing in the laboratory. Here, we report the rearing of Hypselodoris festiva from eggs to adults, where we categorized their post-settlement growth patterns from juvenile to adult stages. Body coloration appeared around 36 days, and organogenesis of vital adult organs began within 42 days after hatching. The anus of H. festiva was observed to change from a ventral to dorsal position during juvenile growth. Individuals reached sexual maturity after six months post-hatching, with successful mating and spawning observed ex situ. This study outlines comprehensive rearing methods and life cycle staging that could be applied to other chromodorid species. We propose H. festiva as a model organism for chromodorid research, with this research contributing to the progress of developmental and evolutionary research on sea slugs.

Spectroscopic characterization of rare natural pink diamonds with yellow color zones

A set of 28 uncommon pink diamonds with yellow color zones are identified among thousands of natural pink diamonds examined. The pink color in these diamonds is caused by the 550 nm absorption band associated with plastic deformation, and is concentrated along straight lamellae (also known as deformation lines). These pink diamonds are type Ia with nitrogen concentrations ranging from 118 to 313 ppma, predominantly as A-centers, i.e., type IaA ≫ B (proportion of B-center < 10 %) to IaA > B (proportion of B-center = 11–26 %).Yellow color zones are observed on or beneath the surface of these faceted pink diamonds. Yellow fluorescence and occasionally yellow phosphorescence excited by long-wave (365 nm) or deep UV (<225 nm), corresponding to the yellow color zones, are commonly observed in yellow diamonds colored by the 480 nm absorption band. PL mapping conducted on the diamond surface and along the depth of the pink diamonds in this study reveals that the yellow color zones have features associated with the 480 nm absorption band. Some of these features are associated with nickel-related defects, and are only detected within the yellow color zones. This suggests that the yellow color zones formed in a different growth episode or from a different diamond-forming fluid than the remaining volume of the diamond with pink body color. Post-growth plastic deformation created defects giving rise to the 550 nm absorption band, producing a pink body color to diamond that was presumably colorless, and producing brown color in zones that may have had pre-existing yellow color. Three diamonds in this study contain eclogitic mineral inclusions, indicating that they formed in association with mantle eclogite, prior to plastic deformation.

Do body colour and sociability impact scototaxis response of fish?

Scototaxis test is an anxiety-like test used by behavioural neuroscientists consisting in the assessment of dark/light preference of laboratory animals. This test has been widely used in fish. Most of the species have been shown to express a preference for the dark environment. However, the majority of the investigated species has a dark body colour, thus making a clear contrast with a white/bright background. Also, while in nature fish tend to be highly social, studies in the scototaxis literature tested single fish. Yet, individual vs. group behaviour might interact with scototaxis response. In experiment 1, we assessed the individual response to test the hypothesis that the different colours of the body might modulate the dark/light preference. We found that species with a dark body colour (Hyphessobrycon megalopterus) and a largely transparent body colour (Kryptopterus bicirrhis) strongly preferred the darker environment. Instead, the preference for darkness of a species with a luminescent part of the body (Paracheirodon axelrodi) was less pronounced. Lastly, a species with a white body colour (Corydoras albini) did not prefer either a bright or a dark sector. In experiment 2, we explored the behaviour of these species when inserted in shoals of 20 individuals in the experimental apparatus. While H. megalopterus and K. bichirrhis confirmed their robust preference for darker environments, the other two species changed their preference. Taken together, these results suggest that scototaxis response is context-dependent, as it appears to be modulated by the body colour and the presence/absence of other conspecifics in the surrounding.

Short Communication: A novel hypopigmentation for southeast Pacific humpback whales

Southeast Pacific humpback whales (Megaptera novaeangliae) migrate annually to breeding grounds in Machalilla, Ecuador, and Uramba Bahía Málaga, Colombia. This species usually displays a black/ grey body colouration with its dorsal and caudal fins exposed above water. Between 2005 and 2023, whales in these regions were studied and photographed on 1,627 days. Results indicated that 29 whales have novel body markings, including white spots, irregular circles and sinuous lines, which resemble the paintings of 20th Century artist Jackson Pollock. While this novel ‘Pollock‐style’ pigmentation does not appear to cause health problems, we recommend further studies to evaluate its origin and effects.

Integrative taxonomy reveals unanticipated hidden diversity in the monotypic goosefish genus Lophiomus (Teleostei, Lophiidae), with description of three new species and resurrection of Chirolophius laticeps Ogilby, 1910

Thought to be monotypic for decades, the only species in the goosefish genus Lophiomus Gill, Lm. setigerus (Vahl), shows a wide range of morphological variation and is distributed widely in the Indo-West Pacific (IWP). In this study, datasets for two mitochondrial and two nuclear genes sequences obtained from samples of Lophiomus collected in different localities across the IWP were constructed and analyzed to explore the phylogeny and species diversity within the genus. Our integrated approach with multiline evidence unveiled an unanticipated richness of at least six delimited species of Lophiomus. Herein, based on materials already available from museums and new specimens obtained primarily through the Tropical Deep-Sea Benthos program surveying IWP benthic fauna, we formally describe three new species: Lm. immaculioralis sp. nov., Lm. nigriventris sp. nov., and Lm. carusoi sp. nov. Also, we resurrect Lm. laticeps stat. rev. from synonyms of Lm. setigerus. These species can be diagnosed by genetics, body coloration, patterns on the floor of the mouth, peritoneum pigmentation, morphometric measurements, and meristic counts of cranial spines, dorsal-fin spines, and pectoral-fin and pelvic-fin rays from each other and from Lm. setigerus. The species Lm. setigerus, as well as the genus Lophiomus, are re-described accordingly based on the new results. Amended identification keys to the four extant lophiid genera and to species of Lophiomus are also provided.

CYMINDIS (ARROSTUS) BORKINI SP. N., A NEW SPECIES OF GROUND-BEETLES FROM THE HIMACHAL PRADESH STATE, INDIA (COLEOPTERA: CARABIDAE: LEBIINI)

A new species of ground-beetles, Cymindis (Arrostus) borkini sp. n., is described from the two localities in Western Himalayas, Himachal Pradesh, India from the environments of the Sungri Town (type locality) and from the Spiti Valley. The new species is similar to both C. (A.) glabrella Bates, 1878 and C. (A.) facchinii Kabak, 2006, but easily differs in the light color of body with dark cruciate elytral pattern, larger eyes and stouter median lobe of aedeagus.

Taxonomic resolution of the hillstream suck-loach Beaufortia pingi species group (Cypriniformes, Gastromyzontidae) and two new species from Southwest China– Beaufortia granulopinna and Beaufortia viridis

Two new species, Beaufortia granulopinna and Beaufortia viridis, are described from the upper Pearl River system in southwest China. Both species share the characteristics of the Beaufortia pingi species group, including prominent vertical stripes on the lateral body and pinnate-type lower lips, distinguishing them from other Beaufortia species. Beaufortia granulopinna is differentiated from other species in the group by possessing a unique set of characteristics: the presence of well-developed prominent tubercles on the first 6–9 pectoral fin rays in adults; and a significant proportion (54.76%) of individuals experiencing blurriness or absence of vertical stripes in the mid-section of the lateral body upon reaching adulthood. The minimum interspecific genetic distance within the genus based on mitochondrial cytb gene sequences is 10.80%. Beaufortia viridis is distinguished from other species in the group by consistently exhibiting vertical stripes of uniform length, width, and spacing across all stages of growth; the absence of tubercles on the branched rays of pectoral fins; and a body coloration of dark cyan to green. The minimum interspecific genetic distance within the genus based on mitochondrial cytb gene sequences is 4.60%. Molecular phylogenetic results confirm that the Beaufortia pingi species group forms a monophyletic clade, which is congruent with morphological classification findings. This study also addresses and resolves the taxonomic ambiguity surrounding Beaufortia pingi and Beaufortia zebroida, providing a redescription of these taxa.

A new species of holothuroid from the Labrador Sea (eastern Canada): Pseudothyonelabradorensis sp. nov. (Echinodermata, Holothuroidea, Dendrochirotida, Sclerodactylidae).

A new species of holothuroid, Pseudothyonelabradorensis sp. nov. (order Dendrochirotida and family Sclerodactylidae), was discovered off the coast of Labrador (eastern Canada) at a depth of 740-969 m. Two specimens were described based on morphological and genetic parameters. Distinctive characters included pinkish body colour, presence of tube feet on a 'tail', supporting rod-shaped ossicles in the tube feet, and rod-shaped ossicles in the tentacles. To investigate its phylogenetic relationships, partial sequences of COI were obtained for the new species as well as for the type species P.raphanus and another North Atlantic species P.serrifera. According to the phylogenetic analysis, P.labradorensis sp. nov. appeared in a well-supported clade with P.raphanus and P.serrifera. Molecular data also suggest polyphyly of the genus, showing the Northeast Pacific species Pseudothyonebelli recovered outside of the clade containing the type species. Pseudothyonelabradorensis sp. nov. is the first species of the genus from the Northwest Atlantic. A key to the North Atlantic Pseudothyone is provided.

Phylogenetics, Molecular Species Delimitation and Geometric Morphometrics of All Reddish-Brown Species in the Genus Neotriplax Lewis, 1887 (Coleoptera: Erotylidae: Tritomini).

To date, five species of reddish-brown Neotriplax have been described, but their highly similar body color and other phenotypic traits make accurate taxonomy challenging. To clarify species-level taxonomy and validate potential new species, the cytochrome oxidase subunit I (COI) was used for phylogenetic analysis and the geometric morphometrics of elytron, pronotum, and hind wing were employed to distinguish all reddish-brown Neotriplax species. Phylogenetic results using maximum likelihood and Bayesian analyses of COI sequences aligned well with the current taxonomy of the Neotriplax species group. Significant K2P divergences, with no overlap between intra- and interspecific genetic distances, were obtained in Neotriplax species. The automatic barcode gap discovery (ABGD), assemble species by automatic partitioning (ASAP), and generalized mixed Yule coalescent (GMYC) approaches concurred, dividing the similar species into eight molecular operational taxonomic units (MOTUs). Geometric morphometric analysis using pronotum, elytron, hind wing shape and wing vein patterns also validated the classification of all eight species. By integrating these analytical approaches with morphological evidence, we successfully delineated the reddish-brown species of Neotriplax into eight species with three new species: N. qinghaiensis sp. nov., N. maoershanensis sp. nov., and N. guangxiensis sp. nov. Furthermore, we documented the first record of N. lewisii in China. This study underscores the utility of an integrative taxonomy approach in species delimitation within Neotriplax and serves as a reference for the taxonomic revision of other morphologically challenging beetles through integrative taxonomy.

New data on the morphology, distribution and host plants of three species of the Terellia virens group (Diptera: Tephritidae)

New data on the morphology, distribution and host plants of three species from the Terellia virens group are provided. Terellia freidbergi Korneyev, 2013 and T. ivannikovi Korneyev et Evstigneev, 2013 are redescribed based on fresh specimens having the body shape and colour characteristic of living flies. Terellia zerovae Korneyev, 1985 is recorded for the first time from Russia; T. ivannikovi, previously known from the Samara Province of Russia, is recorded for the first time from Armenia and from the Saratov and Ul’yanovsk provinces of Russia. Centaurea takhtajanii Gabrieljan et Tonjan is recorded for the first time as a host plant of T. ivannikovi. In Armenia, the larvae of T. freidbergi develop in capitula of C. kotschyi persica (Boiss.) Greuter, C. (Chartolepis) sp., C. polypodiifolia Boiss, C. daralagoezica (Fomin) Greuter and C. spectabilis (Fisch. et C.A. Mey) Sch. Bip.; all these taxa are recorded for the first time as host plants of T. freidbergi. A key to identification of seven species of the T. virens group occurring in Armenia and Russia, is provided.

Current evidence of climate-driven colour change in insects and its impact on sexual signals.

The colours of insects function in intraspecific communication such as sexual signalling, interspecific communication such as protection from predators, and in physiological processes, such as thermoregulation. The expression of melanin-based colours is temperature-dependent and thus likely to be impacted by a changing climate. However, it is unclear how climate change drives changes in body and wing colour may impact insect physiology and their interactions with conspecifics (e.g. mates) or heterospecific (e.g. predators or prey). The aim of this review is to synthesise the current knowledge of the consequences of climate-driven colour change on insects. Here, we discuss the environmental factors that affect insect colours, and then we outline the adaptive mechanisms in terms of phenotypic plasticity and microevolutionary response. Throughout we discuss the impact of climate-related colour change on insect physiology, and interactions with con-and-heterospecifics.

Hainan four-eyed turtles actively select suitable stones to masquerade according to their own morphology.

Masquerade is a form of camouflage in which animals use their body size, shape, and coloration to resemble inanimate objects in their environment to deceive predators. However, there is a lack of experimental evidence to show that animals actively choose objects that match these body parameters. To explore how the Hainan four-eyed turtle, Sacalia insulensis, masquerades using suitable stones, we used indoor video surveillance technology to study the preferences of juvenile S. insulensis for stones of different sizes, shapes, and colors. The results indicated that under normal conditions, during the day, juvenile S. insulensis preferred larger oval or round stones, while at night, they preferred oval stones that were closer to their own size, with no significant preference for stone color during either time. When disturbed (by a researcher swinging their arm back and forth above the experimental setup every hour to mimic a predator), the turtles showed a preference for brown stones that were closer to their size and oval in shape. These findings suggest that juvenile S. insulensis prefer stones that resemble their carapace size and shape to masquerade when undisturbed, and that this preference is reinforced when they masquerade to reduce the risk of predation. The preference for stones that resemble their carapace color is significant only when there is a disturbance. To the best of our knowledge, this is the first study to provide evidence that vertebrates can selectively choose objects that resemble their own morphology for masquerading to reduce predation risk.

Mutation of mpv17 results in loss of iridophores due to mitochondrial dysfunction in tilapia

Abstract Mpv17 (mitochondrial inner membrane protein MPV17) deficiency causes severe mitochondrial DNA depletion syndrome in mammals and loss of pigmentation of iridophores and a significant decrease of melanophores in zebrafish. The reasons for this are still unclear. In this study, we established an mpv17 homozygous mutant line in Nile tilapia. The developing mutants are transparent due to the loss of iridophores and aggregation of pigment granules in the melanophores and disappearance of the vertical pigment bars on the side of the fish. Transcriptome analysis using the skin of fish at 30 dpf (days post fertilization) revealed that the genes related to purine (especially pnp4a) and melanin synthesis were significantly downregulated. However, administration of guanine diets failed to rescue the phenotype of the mutants. In addition, no obvious apoptosis signals were observed in the iris of the mutants by TUNEL staining. Significant downregulation of genes related to iridophore differentiation was detected by qPCR. Insufficient ATP, as revealed by ATP assay, α-MSH treatment, and adcy5 mutational analysis, might account for the defects of melanophores in mpv17 mutants. Several tissues displayed less mtDNA and decreased ATP levels. Taken together, these results indicated that mutation of mpv17 led to mitochondrial dTMP deficiency, followed by impaired mtDNA content and mitochondrial function, which in turn, led to loss of iridophores and a transparent body color in tilapia.

How does rapid body color change affect the conspicuity of lizards to their predators and conspecifics?

How does rapid body color change affect the conspicuity of lizards to their predators and conspecifics?

Family resemblance in color-patch size is not affected by stress experience in a cichlid fish.

Animal body coloration is often linked to social dominance and mating success. This is because it can carry information on an animal's body condition and competitive ability by reflecting the genetic quality of individuals or by responding to their current or past living conditions. The present study investigates genetic and environmental effects on a conspicuous color pattern of the cichlid fish Tropheus sp. black "Ikola," in which the size of a carotenoid-based yellow area on the body co-varies with social dominance. To examine environmental plasticity of the color pattern, we tested for effects of early-life stress, induced by reduced feeding of juveniles prior to color pattern formation, as well as effects of a stress treatment administered to fully colored adult fish. None of the stress treatments affected the color pattern as quantified by the width of the yellow bar. However, offspring bar width was correlated to parental values in mid-parent-mid-offspring regression analyses, and animal models estimated significant additive genetic effects on bar width, indicating heritability of the trait. Depending on the random effects structure of the animal models (i.e., whether including or excluding maternal and brood effects), narrow-sense heritability estimates for bar width ranged between 0.2 and 0.8, with the strongest statistical support for the highest estimate. In each of the alternative models, a large proportion of the total variance in bar width was explained by the included random effects, suggesting that bar width is strongly determined by genetic factors or shared maternal and brood environments, with limited scope for environmental influences later in life.

Rapid body colouration changes in Oryzias celebensis as a social signal influenced by environmental background.

Rapid body colouration changes in some animals, such as chameleons and octopuses, serve dual functions: camouflage and intraspecific communication. It has been hypothesized that these colouration changes originally evolved to provide camouflage and subsequently were co-opted as social signals; however, experimental model systems that are suitable for studying such evolutionary processes are limited. Here, we investigated the relationship between rapid colouration changes of the blackened markings and aggressive behaviours in male Oryzias celebensis, an Indonesian medaka fish, under triadic relationships (two males and one female) or three males conditions with two different environmental backgrounds. In an algae-covered tank, mimicking the common laboratory rearing conditions, males with blackened markings exhibited more frequent attacks towards different conspecific individuals compared with non-blackened males and females. The blackened males were seldom attacked by non-blackened males and females. By contrast, neither aggressive behaviours nor black colouration changes were observed in the transparent background condition with a brighter environment. These indicated that the blackened markings in O. celebensis serve as a social signal depending on the environmental backgrounds. Considering that such colouration changes for camouflage are widely conserved among teleost fishes, the traits are likely to be co-opted for displaying social signals in O. celebensis.

Visual cues do not function in a multimodal signalling context for mate attraction in eastern gray treefrogs

Abstract Anurans use different sensory modalities to communicate and interact socially, including acoustic, chemical, tactile, and visual signals. In a multimodal context, these sensory modes can transmit different information to the receiver or even reinforce the same message. In this study, we hypothesized that body colour traits and vocal sac movements of male eastern gray treefrogs [Dryophytes versicolor (= Hyla versicolor)] serve as secondary visual cues that increase their attractiveness while calling to attract mates. We tested this hypothesis using playback trials combining synthetic advertisement calls with a variety of visual cues, including differently coloured resin frog models, simulated vocal sacs, and live frogs. None of the visual stimuli tested impacted female choice, and there was no difference in response rate, response time, choice angle, or distance covered in the arena between multimodal and unimodal stimuli. However, females showed a strong preference for longer calls even if the less attractive calls were paired with a visual stimulus. The study provides comprehensive insights into the role of visual stimuli in the mate attraction of eastern gray treefrogs and suggests that call traits play a dominant role in the male-selection process of this species, contrary to what was observed for visual stimuli.

Isolation and complete genome sequence analysis of Vibrio rotiferianus strain TO-01 from Trachinotus ovatus to reveal its pathogenicity and drug resistance

Vibrio rotiferianus is a pathogenic bacterium that is widely distributed in the ocean and can cause diseases in a variety of marine animals, including fish, shrimp and shellfish. In this study, we isolated and identified V. rotiferianus strain TO-01 from diseased Trachinotus ovatus. Infected fish exhibited a range of pathological symptoms, including lethargy in swimming, blackened body coloration, skin ulceration and erratic side swimming. Tissue section examination revealed pronounced damage to the liver, spleen and gills of the infected fish. An analysis of immune factor expression revealed a significant increase in the expression of inflammatory factors, including interleukin (IL)-1, IL-2, IL-6 receptor and IL-21, in the spleen and kidney of fish infected with TO-01 at 6 h post-infection. To gain a more in-depth comprehension of the pathogenicity and drug resistance of V. rotiferianus, we conducted whole genome sequencing. The total genome length of V. rotiferianus was 4734,075 bp, and 74 virulence factors were predicted within the genome. Most of these virulence genes were associated with bacterial adhesion and flagellar motility. A gene associated with group sensing, cqsA, and a gene associated with hemolysin, tlh, were also identified. The prediction of drug resistance genes was in agreement with the results of drug sensitivity assays, both of which indicated that TO-01 has significant resistance to β-lactams. The findings of this study significantly enhance our understanding of the pathogenic mechanism of V. rotiferianus and give crucial insights into disease prevention and control in the management of T. ovatus.

The cuticular protein gene ApCP7 and ApCP62 are essential for reproduction in Acyrthosiphon pisum, affecting ecdysis and survival

Cuticular proteins, in conjunction with chitin, compose the insect exoskeleton, and play a key role in the growth, development, and molting of insects. However, the specific functions of most cuticular protein genes in the growth, development, and reproductive processes of the pea aphid (Acyrthosiphon pisum) remain unclear. In this study, we have identified six cuticular protein genes in the pea aphid, namely ApCP7, ApCP10, ApCP19, ApCP19.8-like, ApCP35 and ApCP62. We found that the expression levels of six genes were highly expressed during the adult stage, and except for ApCP10, which is highly expressed in the pea aphid cuticle, other genes were highly expressed in the ovaries. Subsequently, we observed that the survival rate and fecundity of pea aphid were significantly lower than those of the control group after silencing ApCP7 and ApCP62 through RNA interference. Furthermore, when ApCP7 transcript levels were reduced, aphid encountered difficulties in molting, were smaller in body size, and exhibited a darker body color. These results indicate that ApCP7 and ApCP62 are involved in the development and reproduction of pea aphid, and could be used as RNAi targets for controlling pea aphid.

A chromosome-level genome of the striated frogfish (Antennarius striatus)

The striated frogfish (Antennarius striatus), a member of the sub-order Antennarioidei within the order Lophiiformes, possesses remarkable adaptations. These include the ability to modulate body coloration for camouflage, utilize bioluminescent esca for predation, and employ elbow-like pectoral fins for terrestrial locomotion, making it a valuable model for studying bioluminescence, adaptive camouflage, fin-to-limb transition, and walking-like behaviors. To better study and contribute to the conservation of the striated frogfish, we obtained the micro-CT image of the pectoral fin bones and generated a high-quality, chromosome-level genome assembly using multiple sequencing technologies. The assembly spans 548.56 Mb with a contig N50 of 21.05 Mb, and 99.35% of the genome is anchored on 24 chromosomes, making it the most complete genome available within Lophiiformes. The genome annotation revealed 28.43% repetitive sequences and 23,945 protein-coding genes. This chromosome-level genome provides valuable genetic resources for frogfish conservation and offers insights into the genetic mechanisms underlying its unique phenotypic evolution. Furthermore, it establishes a foundation for future research on limb development and adaptive camouflage in this species.