Body Color Research Articles

Transcriptome analysis of purple and green Apostichopus japonicus reared under different breeding environments

Sea cucumber (Apostichopus japonicus) is one of the cultured species with the highest production value to a single species in China’s marine agricultural industry with high nutritional and medicinal value. Body color influences numerous biological functions in sea cucumbers, and it has become a key trait in selective breeding. It is found that a cultivation environment with strong light intensity leads to a lighter body color of A. japonicus compared to dark conditions. However, little research has been conducted on the molecular mechanisms regulating body color in different breeding environments. In this study, we used Illumina sequencing to examine gene expression patterns in green and purple A. japonicus exposed to different culture conditions. Overall, the genes in the body wall of purple individuals were more affected by the environment. We also identified pathways that were potentially influenced by the breeding environment, such as “Drug metabolism - cytochrome P450”, “Porphyrin and chlorophyll metabolism”, “Phosphatidylinositol signaling system”, “TGF-beta signaling”, and “mTOR signaling”. The aim of this study was to determine the light conditions and breeding environment that are more favorable to the requirements of body color in A. japonicus and apply them to the selection of high-quality breeds. The results obtained will support the breeding of A. japonicus with specific traits and the production of seedlings to promote the development of this maricultural industry.

A new species of the Scinax cruentomma group (Anura: Hylidae) from the Ucayali River basin of Loreto, Peru.

We describe a new species of the Scinax cruentomma species group, with a red streak in the iris and a weakly bilobate vocal sac. It is known from oligotrophic soils in the sedimentary basin of the Ucayali River near Jenaro Herrera (province of Requena, Peru) and Ro Blanco (buffer zone of the Matses Indigenous territory and reserve). The new species can be distinguished from the other species of the S. cruentomma group by its small snout-vent length, body and iris color patterns, weakly bilobate vocal sac, myological characters, and the number of notes and pulses of the advertisement call. It is morphologically most similar to S. strussmannae, from which the advertisement call, nostril, canthus rostralis, and loreal region can distinguish it.

Morphological characteristic and truss morphometric analysis of amphidromous goby (‘nike') (Teleostei: Gobiiformes) in Bone River, Gorontalo, Indonesia

Abstract. Pasisingi N, Suci D, Panigoro C, Kadim MK. 2024. Morphological characteristic and truss morphometric analysis of amphidromous goby (‘nike') (Teleostei: Gobiiformes) in Bone River, Gorontalo, Indonesia. Biodiversitas 25: 223-231. One of the preferred fish resources in the Gorontalo region is amphidromous goby species, commonly known by local community as nike fish. In rivers, at the adult stage, these fish are morphologically and potentially morphometrically not necessarily distinguishable among species and between sexes. This research aimed to identify the morphological and morphometric truss characters that distinguish the sexual characteristics of goby fishes in the Bone River, Gorontalo. Fish samples were purposefully collected from eight sites along the river, spanning from upstream to downstream, using a backpack electrofishing device. Sampling occurred in March and November 2022, with morphological analysis and measurements conducted on 336 individuals. The morphometric method measured data from 13 points on the sample body, forming 28 combinations of truss distance characters (A1-A3; B1-B12; C1-C10; D1-D3) connecting these points. Morphologically, the samples were identified as three species, namely Sicyopterus longifilis, Belobranchus belobranchus, and Awaous grammepomus. This study revealed distinctions in morphological characters between male and female individuals. In S. longifilis, males exhibited a relatively slimmer body shape compared to the rounded form of females. Male B. belobranchus displayed more striking coloration than females, while male A. grammepomus featured a lighter brown body color than the paler females. All the morphometric truss characters in this study can be reliably used as a sexual distinguishing characteristic in S. longifilis. As for species B. belobranchus, B7 truss cannot be considered a differentiator. In A. grammepomus, thirteen truss characters (B3, B4, B6, B7, B8, B10, B12, C3, C6, C7, C9, C10, D1) cannot be used to differentiate males and females.

Arion vulgaris (Gastropoda: Pulmonata: Arionidae) – a new alien species in the fauna of Donbass

The first anatomically confirmed record of the Western European mollusk Arion vulgaris Moquin-Tandon, 1855 (Gastropoda: Pulmonata: Arionidae) in the territory of Donbass is described. The species was found in the central city park of Donetsk. Adults were rufous (from grayish rufous to bright orange) or brown in color without dark lateral bands or traces of them. The color of the soles of subadult and adults was from cream to dark gray, regardless of body color, individuals with light gray uniformly colored (39.4%) and cream (35.2%) soles dominated. Egg laying was recorded in September-October. Eggs, juveniles hatched from eggs, subadult and adult hibernate. Some individuals have a lifespan of more than one year. Over the five-year observation period, the area of the colony did not increase and is 0.325 ha, that indicates a low invasive potential of the species in the steppe zone. The distribution of A. vulgaris in the Donbass is likely to be limited to local colonies in populated areas, however, anthropochore invasion of the species into the ravine and fl oodplain forests of the region is possible.

Amazons Are Back: Absence of Males in a Praying Mantis from Uruguayan Savannas.

With a broad distribution throughout South America, Brunneria subaptera (Saussure)(Coptopterygidae) is the most abundant praying mantis species in Uruguay, mostly associated with grassland vegetation. Their body coloration can vary between green or brown sepia. The recent catalog of Uruguayan mantids showed that all specimens of B. subaptera from the collections in Uruguay were females, suggesting an absence of males in natural populations. The aim of this study was to determine the occurrence of female-only populations of B. subaptera in Uruguay. Moreover, we analyzed the genetic variation and estimated the time of the most recent common ancestor of the species. We performed bimonthly samplings in two localities in Uruguay for 1year and we sexed the individuals. We extracted DNA from the abdominal tissue of adult females and sequenced a fragment of the mitochondrial cox1 gene to assess the genetic diversity and to estimate diversification times. We did not find any males in either of the studied localities. The age estimates revealed a recent origin of the species (2.33Ma), and there was no genetic differentiation between the individuals from Uruguayan localities. This absence of males of B. subaptera documented in the sampled locations suggests that the species reproduces by thelytokous parthenogenesis. This study opens promising venues for future research into reproductive strategies and polymorphism in South-American praying mantises that inhabit one of the largest areas of grasslands in the world, currently under dramatic deterioration and reduction.

Sexual dichromatism in the fur of a bat: An exploration of color differences and potential signaling functions.

Sex differences in body color (i.e., sexual dichromatism) are rare in bats and, more broadly, in mammals. The eastern red bat (Lasiurus borealis) is a common tree-roosting bat that occupies much of North America and has long been described as sexually dichromatic. However, previous research on this species found that absolute body size and collection year were better predictors of fur color in preserved specimens than sex. We revisited this issue and photographed 82 live eastern red bats under standardized conditions, then used image analysis to quantify pelage hue, saturation, and value. We used an information theoretic approach to evaluate four competing hypotheses about the principal drivers of color differences in the fur of eastern red bats. Our analyses demonstrated that sex was a better predictor of pelage color than body size; males had redder, more saturated, and lighter pelages than females. Additionally, the fur color of juvenile versus adult bats differed somewhat, as juveniles were darker than adults. In general, absolute body size (i.e., forearm length in bats) was a poor predictor of color in live eastern red bats. In an exploratory post-hoc analysis, we confirm that fur color is related to body mass (i.e., a proxy for body condition in bats), suggesting color might serve as a sexually selected signal of mate quality in this partially diurnal species. Future work should investigate the functional role of sexual dichromatism in this species, which could be related to signaling or possibly thermoregulation.

Neurotransmitter norepinephrine regulates chromatosomes aggregation and the formation of blotches in coral trout Plectropomus leopardus.

Color changes and pattern formations can represent strategies of the utmost importance for the survival of individuals or of species. Previous studies have associated capture with the formation of blotches (areas with light color) of coral trout, but the regulatory mechanisms link the two are lacking. Here, we report that capture induced blotches formation within 4-5seconds. The blotches disappeared after anesthesia dispersed the pigment cells and reappeared after electrical stimulation. Subsequently, combining immunofluorescence, transmission electron microscopy and chemical sympathectomy, we found blotches formation results from activation of catecholaminergic neurons below the pigment layer. Finally, the in vitro incubation and intraperitoneal injection of norepinephrine (NE) induced aggregation of chromatosomes and lightening of body color, respectively, suggesting that NE, a neurotransmitter released by catecholaminergic nerves, mediates blotches formation. Our results demonstrate that acute stress response-induced neuronal activity can drive rapid changes in body color, which enriches our knowledge of physiological adaptations in coral reef fish.

A fish can change its stripes: investigating the role of body colour and pattern in the bluelined goatfish.

Bluelined goatfish (Upeneichthys lineatus) rapidly change their body colour from a white horizontally banded pattern to a seemingly more conspicuous vertically banded red pattern, often when foraging. Given the apparent conspicuousness of the pattern to a range of observers, it seems unlikely that this colour change is used for camouflage and instead may be used for communication/signalling. Goatfish often drive multispecies associations, and it is possible that goatfish use this colour change as a foraging success signal to facilitate cooperation, increase food acquisition, and reduce predation risk through a 'safety in numbers' strategy. Using a novel approach, we deployed 3D model goatfish in different colour morphs-white without bands, white with black vertical bands, and white with red vertical bands-to determine whether the red colouration is an important component of the signal or if it is only the vertical banding pattern, regardless of colour, that fish respond to as an indicator of foraging success. Use of remote underwater video allowed us to obtain information without the influence of human observers on the communities and behaviours of other fish in response to these different colours exhibited by goatfish. We found that conspecifics were more abundant around the black- and red-banded model fish when compared with the white models. Conspecifics were also more likely to forage around the models than to pass or show attraction, but this was unaffected by model colour. No difference in the abundance and behaviour of associated heterospecifics around the different models was observed, perhaps due to the static nature of the models. Some species did, however, spend more time around the red- and black-banded fish, which suggests the change in colour may indicate benefits in addition to food resources. Overall, the results suggest that the body colour/pattern of U. lineatus is likely a signalling tool but further work is required to explore the benefits to both conspecifics and heterospecifics and to further determine the behavioural functions of rapid colour change in U. lineatus.

Effects of Photoperiod on Survival, Growth, Physiological, and Biochemical Indices of Redclaw Crayfish (Cherax quadricarinatus) Juveniles

Through a 30-day experiment, this study investigated the effects of five photoperiods (0L:24D, 6L:18D, 12L:12D, 18L:6D, and 24L:0D) on the survival, enzyme activity, body color, and growth-related gene expression of redclaw crayfish (Cherax quadricarinatus) juveniles. The results showed that C. quadricarinatus juveniles under 18L:6D and 24L:0D photoperiods exhibited the highest survival rate, which was significantly higher than the survival rates of juveniles under the other three photoperiods (p < 0.05). However, the 0L:24D group had the highest final body weight and weight gain rate, significantly surpassing those of the 12L:12D, 18L:6D, and 24L:0D groups (p < 0.05). Regarding enzyme activity and hormone levels, juveniles under the 18L:6D photoperiod exhibited relatively higher activity of superoxide dismutase (SOD), acid phosphatase (ACP), and lysozyme (LZM) enzymes than those under other photoperiods, but their levels of melatonin and cortisol were relatively low. In addition, the 24L:0D group showed the highest malondialdehyde (MDA) content. Analysis of gene expression levels revealed that retinoid X receptor (RXR) and α-amylase (α-AMY) genes in C. quadricarinatus juveniles exhibited significantly higher expression levels under the 18L:6D photoperiod than those under the other four photoperiods (p < 0.05). With increasing daylight exposure, the body color of C. quadricarinatus changed from pale blue to yellow–brown. In summary, C. quadricarinatus juveniles achieved high survival rates, good growth performance, strong antioxidant stress response, and immune defense capabilities under an 18 h photoperiod. Therefore, in the industrial seedling cultivation of redclaw crayfish, it is recommended to provide 18 h of daily light. Further, the study demonstrated the ability to manipulate the body color of C. quadricarinatus through controlled artificial photoperiods. These findings provide essential technical parameters needed for the industrial cultivation of C. quadricarinatus juveniles.

Beyond color and pattern: elucidating the factors associated with intraspecific aggression in the mimic poison frog (Ranitomeya imitator)

Assortative or disassortative aggression – when individuals display more aggression towards conspecifics with similar or different phenotypic characteristics – can either maintain polymorphisms or facilitate gene flow between populations depending on which direction the aggression is aimed. Deciphering which factors elicit or prevent aggression is crucial to improving our knowledge of the origin and maintenance of reproductive barriers and subsequent speciation. The Peruvian mimic poison frog, Ranitomeya imitator, is a monogamous and territorial species that has evolved into four distinct color-pattern morphs in a mimetic radiation. Here we use historical landscape genetic data and competition trials between male individuals sourced from different populations and color-pattern morphs to show that the level of aggression between individuals is not associated with color morph or body size but rather with source population. Individuals spent more time in combat with individuals from their own deme (genetically homogeneous population), irrespective of color morph or size. These findings indicate that genotypic similarity is correlated with increased aggression in R. imitator, though the mechanism by which R. imitator males identify conspecifics as territorial threats remains unclear. As body size and color morph were not significantly associated with aggression levels, this study emphasizes the necessity of further research to identify whether other phenotypic traits are influencing territorial behavior between male frogs, and if these factors play a role in increasing gene flow, or conversely, the formation of reproductive barriers between populations.

Effects of Water Temperature on the Body Color and Expression of the Genes Related to Body Color Regulation in the Goldfish.

Melanin-concentrating hormone (MCH), melanocyte-stimulating hormone (MSH), and somatolactin (SL) in the hypothalamus-pituitary axis are associated with body color regulation in teleost fish. Although these hormones' production and secretion respond well to light environments, such as background color, little is known about the effects of different water temperatures. We investigated the effects of water temperature, 10°C, 20°C, and 30°C, on body color and the expression of these genes and corresponding receptor genes in goldfish. The body color in white background (WBG) becomes paler at the higher water temperature, although no difference was observed in black background (BBG). Brain mRNA contents of proMCH genes (pmch1 and pmch2) increased at 30°C and 20°C compared to 10°C in WBG, respectively. Apparent effects of background color and temperature on the pituitary mRNA contents of a POMC gene (pomc) were not observed. The pituitary mRNA contents of the SLα gene were almost double those on a WBG at any temperature, while those of the SLβ gene (slb) at 30°C tended to be higher than those at 10°C and 20°C on WBG and BBG. The scale mRNA contents of the MCH receptor gene (mchr2) in WBG were higher than those in BBG at 30°C. The highest scale mRNA contents of MSH receptor (mc1r and mc5r) on BBG were observed at 20°C, while the lowest respective mRNA levels were observed at 30°C on WBG. These results highlight the importance of temperature for the endocrinological regulation of body color, and darker background color may stabilize those endocrine functions.

Spawning, larval morphological ontogeny and first feeding of yellow-striped cardinalfish Ostorhinchus cyanosoma (Bleeker, 1853)

The yellow-striped cardinalfish (Ostorhinchus cyanosoma) can be found in the Indo-West Pacific region. It possesses great potential for the ornamental aquarium market due to its vibrant body coloration and tendency of group swimming. This study aims to investigate the spawning frequency and larval morphological ontogeny, and develop first feeding techniques of O. cyanosoma reared in capacity. From April 2021 to August 2022, a total of 70 spawning events were documented for the broodstock. These spawning events did not exhibit specific patterns related to seasonal or lunar cycles. The effects of four live prey treatments (mono-feeding and co-feeding of SS-type rotifer Brachionus sp. and nauplii of copepod Bestiolina coreana) on the mouth opening rate, prey ingestion rate, and prey selectivity of the 0 day-post-hatch (dph) larvae were investigated. The O. cyanosoma larvae displayed significantly higher mouth opening rate, ingestion rate and prey selectivity on the copepod nauplii over the rotifer. In the 7-d larviculture experiment, the larvae showed significant higher survival rate in the copepod feeding treatment (68%) than the rotifer feeding treatment (0%). For ontogeny, O. cyanosoma larvae appeared to be altricial (at pre-flexion stage with no gas bladder and poor-developed fins) and small-mouthed (235.94 μm) when leaving the mouthbrood. The standard length increased from 2.64 to 6.51 mm during 0 to 21dph. Ntochord flexion initiated at 12 dph, and the metamorphosis was completed by 21 dph. This study is the first attempt to document the broodstock management, first feeding protocol and larval ontogeny of O. cyanosoma. The findings could have implications for larviculture of cardinalfishes.

Genetic variability of New Caledonian Boeckella De Guerne & Richard, 1889 (Copepoda: Calanoida), with the description of a new species

Abstract Thirteen new freshwater populations of the copepod genus BoeckellaDe Guerne & Richard, 1889 were found during three expeditions to New Caledonia (‘La Planète Revisitée,’ 2016-2018). The 12 populations from the Plaine des Lacs, which show remarkable genetic diversity among themselves, were identified as B. spinogibbaDefaye, 1998, the only species of its genus known from New Caledonia until now. The sole exception, the population from Mont-Dore 22 km further east, appeared genetically and morphologically distinct from the others and is described herein as a new species. The two species are distinguished from each other by the shapes of the male and female P5, female Th5, and body colour. A previously published key is amended to separate the species. Our concatenated COI+28S phylogeny places the two New Caledonia species as a new branch within Boeckella, distinct from the branches consisting of South American, Antarctic and Australasian species. All 13 Boeckella populations inhabit the extreme south of New Caledonia, an area known for endemism and high heavy metal concentrations in the soil. Extensive mining activity in this metal-rich area, begun in 1873, is now leading to conflict with conservation goals. By using aerial photographs to trace the fate of the pond that is the type locality of B. spinogibba, we confirmed that it disappeared between 2007 and 2014 as a result of the expansion of the Goro nickel mine.

Deciphering scavenger receptors reveals key regulators in the intestine that function in carotenoid coloration of leopard coral groupers (Plectropomus leopardus)

Carotenoid based body coloration are common features in fish, which depends on the diet derived carotenoids pigments deposition, employing a bunch of carotenoid uptake, absorption and processing related genes. Scavenger receptors are a large family of cell surface receptors with complex structure and diverse functions. However, the SRs genes have been insufficiently explored concerning their role in fish carotenoid coloration. Here, we systemically identified 19 SRs family genes and investigated their expression patterns of in various tissues of P. leopardus. Expression analysis unveiled the diverse involvements of SRs in the intestine of P. leopardus with different body colors and the responses to exogenous carotenoids. Notably, cd36, emerged as a pivotal factor in intestinal functions predominantly localized in the intestinal epithelial and goblet cells. Knockdown of cd36 led to the reduction in skin brightness and carotenoid levels in both intestine and skin, while overexpressing cd36 increased the carotenoids uptake of cells in vitro. Additionally, our investigations revealed that cd36 exerts regulation on genes associated with carotenoid uptake, transport, and processing. To sum up, our results provide a comprehensive view on SRs functions in carotenoid coloration of P. leopardus and will facilitate the understanding on the mechanism of carotenoids coloration of vertebrates.

Genetically Encoded Lizard Color Divergence for Camouflage and Thermoregulation.

Local adaptation is critical in speciation and evolution, yet comprehensive studies on proximate and ultimate causes of local adaptation are generally scarce. Here, we integrated field ecological experiments, genome sequencing, and genetic verification to demonstrate both driving forces and molecular mechanisms governing local adaptation of body coloration in a lizard from the Qinghai-Tibet Plateau. We found dark lizards from the cold meadow population had lower spectrum reflectance but higher melanin contents than light counterparts from the warm dune population. Additionally, the colorations of both dark and light lizards facilitated the camouflage and thermoregulation in their respective microhabitat simultaneously. More importantly, by genome resequencing analysis, we detected a novel mutation in Tyrp1 that underpinned this color adaptation. The allele frequencies at the site of SNP 459# in the gene of Tyrp1 are 22.22% G/C and 77.78% C/C in dark lizards and 100% G/G in light lizards. Model-predicted structure and catalytic activity showed that this mutation increased structure flexibility and catalytic activity in enzyme TYRP1, and thereby facilitated the generation of eumelanin in dark lizards. The function of the mutation in Tyrp1 was further verified by more melanin contents and darker coloration detected in the zebrafish injected with the genotype of Tyrp1 from dark lizards. Therefore, our study demonstrates that a novel mutation of a major melanin-generating gene underpins skin color variation co-selected by camouflage and thermoregulation in a lizard. The resulting strong selection may reinforce adaptive genetic divergence and enable the persistence of adjacent populations with distinct body coloration.

Genetic structure, UV-vision, wing coloration and size coincide with colour polymorphism in Fabriciana adippe butterflies.

Colour polymorphisms have long served as model systems in evolutionary studies and continue to inform about processes involved in the origin and dynamics of biodiversity. Modern sequencing tools allow for evaluating whether phenotypic differences between morphs reflect genetic differentiation rather than developmental plasticity, and for investigating whether polymorphisms represent intermediate stages of diversification towards speciation. We investigated phenotypic and genetic differentiation between two colour morphs of the butterfly Fabriciana adippe using a combination of ddRAD-sequencing and comparisons of body size, colour patterns and optical properties of bright wing spots. The silvery-spotted adippe form had larger and darker wings and reflected UV light, while the yellow cleodoxa form displayed more green scales and reflected very little UV, showcasing that they constitute distinct and alternative integrated phenotypes. Genomic analyses revealed genetic structuring according to source population, and to colour morph, suggesting that the phenotypic differentiation reflects evolutionary modifications. We report 17 outlier loci associated with colour morph, including ultraviolet-sensitive visual pigment (UVRh1), which is associated with intraspecific communication and mate choice in butterflies. Together with the demonstration that the wings of the adippe (but essentially not the cleodoxa) morph reflect UV light, that UV reflectance is higher in females than males and that morphs differ in wing size, this suggests that these colour morphs might represent genetically integrated phenotypes, possibly adapted to different microhabitats. We propose that non-random mating might contribute to the differentiation and maintenance of the polymorphism.

Sexual dimorphism and ecomorphology of the Berthold’s bush anole (Polychrus gutturosus) in Costa Rica

Abstract Morphological variation present within a species is the result of sexual or natural selection and determines the ecological relationships (i.e., ecomorphology) and the degree of sexual dimorphism. For most lizard species, either males or females are the larger sex, suggesting that selection operates differently on each sex. Thus, differences in morphology can determine the habitat use made by males and females. Here we use the Berthold’s bush anole (Polychrus gutturosus), a rare arboreal, diurnal lizard, to examine whether morphological and ecological measures differ among sexes and whether such potential differences emerge as a result of resource partitioning. We measured the morphology of wild individuals from one population and from preserved specimens collected in Costa Rica. We collected data on nine morphological measurements, nocturnal body and air temperatures, and sleeping perch height. We measured 45 wild individuals (22 males and 23 females) and 17 preserved specimens (6 males and 11 females). We found a female-biased body size, and male-biased tail length, head dimensions, and limb lengths. We also observed differences between males and females in body color and the size and shape of femoral pores, although these differences require quantification. We did not find sex differences in sleeping perch height or nocturnal body temperature. Our results demonstrate that resource partitioning does not explain differences among sexes, and that female-biased body size in P. gutturosus might reflect selection operating on increased fecundity.

New Lineaburmops fossils (Araneae: Lagonomegopidae) with contrasting color patterns from mid-Cretaceous Kachin amber, northern Myanmar

The fossil spider family Lagonomegopidae is widespread in the Cretaceous period, and mainly reported from mid-Cretaceous Kachin amber, northern Myanmar. Here, two new lagonomegopid species, belonging to the genus Lineaburmops, are described from Kachin amber: Lineaburmops longiantepes sp. nov. and Lineaburmops rhombus sp. nov., which showing similar contrasting body coloration as other Lineaburmops species. The compositional element of these special color patterns and their potential functions are discussed.

Differential expression and alternative splicing analyses of multiple tissues reveal albinism-associated genes in the Wels catfish (Silurus glanis)

Albinism is a widespread departure from a typical body colouration due to altered melanin production. The Wels catfish (Silurus glanis) is among the largest freshwater fish species in the world, and albino individuals occur both in the wild and in aquaculture. Here, we performed transcriptome-wide analysis of albino and normally pigmented S. glanis using four tissues (skin, dorsal fin, whole eye and liver) to identify genes associated with albinism by exploring patterns of differential expression (DE) and differential alternative splicing (DAS). Multi-tissue analyses revealed a large number of genes in skin (n = 1355) and fin (n = 614) tissue associated with the albino phenotype in S. glanis, while the number of DE genes in eye and liver tissues was lower (n = 188, n = 189, respectively). Several DE genes across multiple tissues were detected as the most promising candidates (e.g., hsp4, hsp90b1, raph1, uqcrfs1, adcy-family and wnt-family) potentially causally linked to the albino phenotype in Wels catfish. Moreover, our findings supported earlier observations of physiological differences between albino and normally pigmented individuals, particularly in energy metabolism and immune response. In contrast, there were only a few pigmentation-related genes observed among DAS genes (4 in skin, 2 in fin), the overlap between DAS and DE genes was low (n = 25) and did not include known pigmentation-related genes. This suggests that DAS and DE in Wels catfish are, to a large extent, independent processes, and the observed alternative splicing cases are probably not causally linked with albinism in S. glanis. This work provides the first transcriptome-wide multi-tissue insights into the albinism of Wels catfish and serves as a valuable resource for further understanding the genetic mechanisms of pigmentation in fish.

Quantitative analysis of infectious precocity virus load and stunted growth syndrome via an immunohistochemical assay and reverse transcriptase quantitative real-time PCR in Macrobrachium rosenbergii

The giant freshwater prawn Macrobrachium rosenbergii (M. rosenbergii) is susceptible to a flavivirus known as the infectious precocity virus (IPV). The symptoms of infection, such as sexual precocity and stunted growth, collectively constitute what is referred to as iron prawn syndrome (IPS). IPV manifests as a persistent, long-term infection marked by subtle morphological changes that pose challenges for detection. Prawns suspected of early-stage infection do not necessarily present clear clinical signs. This study investigated IPV diagnostics based on clinical signs, immunohistochemistry (IHC), and reverse transcriptase quantitative real-time PCR (RT-qPCR) in prawns suspected of IPV-infection. We also explored the correlations among the three diagnostic approaches. Some clinical signs are easily observable, such as shorter body length, mature gonads, elongated blue claws, blue tailfins, and darker body coloration; however, they are not absolute signs of infection. Additionally, many infected prawns do not exhibit clear clinical signs during the early stages. We produced anti-IPV serum and then applied it via IHC staining to highlight the location of the virus. Positive signals were observed in the perinuclear cytoplasm of haemocytes in the hepatopancreas, gills, and pereiopods. IPV-positive signals were also detected in support cells within the lamina ganglionaris as well as in neurosecretory cells within the bellonci organ, sinus glands, and the X organ. The detection of IPV-positive signals in prawns without clinical signs demonstrates the value of this diagnostic method. IHC analysis was used to distinguish between IPV-positive and IPV-negative prawns, and also used in conjunction with RT-qPCR to quantify viral loads in these two groups. The IPV viral loads were as follows: IHC-positive prawns (> 103.5 copies/ μg) and IHC-negative prawns (< 103.5 copies/ μg). Note that the highest numbers of viral copies were observed in pleopods, which are easily obtained and do not necessitate sacrificing the animal. In conclusion, the correlation between viral load and IHC pathological diagnosis could be used to identify cases of IPV infection, while providing valuable insights into disease prevention and prognosis.