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Intercellular communication is indispensable across multicellular organisms, and any aberration in this process can give rise to significant anomalies in developmental and homeostatic processes. Thus, a comprehensive understanding of its mechanisms is imperative for addressing human health-related concerns. Recent advances have expanded our understanding of intercellular communication by elucidating additional signaling modalities alongside established mechanisms. Notably, cellular protrusion-mediated long-range communication, characterized by physical contact through thin and elongated cellular protrusions between cells involved in signal transmission and reception, has emerged as a significant intercellular signaling paradigm. This chapter delves into the exploration of a signaling cellular protrusion termed 'airinemes,' discovered in the zebrafish skin. It covers their identified signaling roles and the cellular and molecular mechanisms that underpin their functionality.

One of the rarest and most unusual iguanas on the planet is the Galápagos pink land iguana (Conolophus marthae). There have been a number of hypotheses on the source of their pink coloration, including that the colour is from blood and a relative lack of dermal pigmentation. We obtained full thickness skin biopsies of three species and compared tissue from darkly pigmented areas and lightly pigmented surfaces. "Pink" areas of pink iguanas are devoid of pigment cells (e.g. melanophores) and the dermal tissue is rich with aggregates of confluent capillaries. This was in sharp contrast to the minimally vascular (only capillaries were observed) dermal areas of the marine and yellow iguanas. The dermal stratum laxum of every biopsy site contained melanophores except for the pink skin of pink iguanas. Interestingly, marine iguanas have a much thicker epidermal stratum germinativum/granulosum, between 2 and 10 cells thick depending on location, compared to the thinner epidermal stratum germinativum/granulosum of land iguanas (one to three cells thick with most areas possessing just one or two cell layers). These microscopic differences might reflect differences in habitat and ecology of the three species. [ABSTRACT FROM AUTHOR]

Introduction: Developmental processes continue in organisms in which sensory systems have reached functional maturity, however, little research has focused on the influence of sensory input on cell and tissue development. Here, we explored the influence of visual system activity on the development of skin melanophores in Xenopus laevis. Methods: Melanophore number was measured in X. laevis larvae after the manipulation of visual input through eye removal (enucleation) and/or incubation on a white or black substrate at the time when the visual system becomes functional (stage 40). To determine the developmental process impacted by visual input, migration, proliferation and differentiation of melanophores was assessed. Finally, the role of melatonin in driving melanophore differentiation was explored. Results: Enucleating, or maintaining stage 40 larvae on a black background, results in a pronounced increase in melanophore number in the perioptic region within 24 h. Time lapse analysis revealed that in enucleated larvae new melanophores appear through gradual increase in pigmentation, suggesting unpigmented cells in the perioptic region differentiate into mature melanophores upon reduced visual input. In support, we observed increased expression of melanization genes tyr, tyrp1, and pmel in the perioptic region of enucleated or black background-reared larvae. Conversely, maintaining larvae in full light suppresses melanophore differentiation. Interestingly, an extra-pineal melatonin signal was found to be sufficient and necessary to promote the transition to differentiated melanophores. Discussion: In this study, we found that at the time when the visual system becomes functional, X. laevis larvae possess a population of undifferentiated melanophores that can respond rapidly to changes in the external light environment by undergoing differentiation. Thus, we propose a novel mechanism of environmental influence where external sensory signals influence cell differentiation in a manner that would favor survival. [ABSTRACT FROM AUTHOR]

Reptilian skin coloration is spectacular and diverse, yet little is known about the ontogenetic processes that govern its establishment and the molecular signaling pathways that determine it. Here, we focus on the development of the banded pattern of leopard gecko hatchlings and the transition to black spots in the adult. With our histological analyses, we show that iridophores are present in the white and yellow bands of the hatchling and they gradually perish in the adult skin. Furthermore, we demonstrate that melanophores can autonomously form spots in the absence of the other chromatophores both on the regenerated skin of the tail and on the dorsal skin of the Mack Super Snow (MSS) leopard geckos. This color morph is characterized by uniform black coloration in hatchlings and black spots in adulthood; we establish that their skin is devoid of xanthophores and iridophores at both stages. Our genetic analyses identified a 13-nucleotide deletion in the PAX7 transcription factor of MSS geckos, affecting its protein coding sequence. With our single-cell transcriptomics analysis of embryonic skin, we confirm that PAX7 is expressed in iridophores and xanthophores, suggesting that it plays a key role in the differentiation of both chromatophores. Our in situ hybridizations on whole-mount embryos document the dynamics of the skin pattern formation and how it is impacted in the PAX7 mutants. We hypothesize that the melanophores-iridophores interactions give rise to the banded pattern of the hatchlings and black spot formation is an intrinsic capacity of melanophores in the postembryonic skin. [ABSTRACT FROM AUTHOR]

Accurate species identification is critical to monitoring programs because mis-identifications can lead to incorrect assessments of population status and trends. In the San Francisco Estuary, efforts to monitor the imperiled osmerid Delta Smelt (Hypomesus transpacificus) using morphology can be challenging because of the presence of the similar-looking non-native osmerid Wakasagi (Hypomesus nipponensis). In 2017, the US Fish and Wildlife Service’s field office in Lodi implemented a two-stage verification process for Wakasagi to help prevent Delta Smelt from being mis-identified as Wakasagi. Under this process, Wakasagi are initially identified in the field, independently identified a second time by an experienced staff member in the laboratory, then stored on-site where they can be made available for future studies. Using the recently developed Specific High-sensitivity Enzymatic Reporter un-LOCKing (SHERLOCK) assay for Wakasagi, we evaluated how well verification protocols performed by genetically identifying a subset of Wakasagi collected during routine sampling between 2017 and 2021. Through this study, we found that the protocols have served as an effective quality control measure for over 4 years and across multiple surveys. With the development of field-deployable genetics tools such as SHERLOCK, genetic identification will likely play an increasingly important role in ecological monitoring. We expect that hybrid approaches that combine morphological identifications by trained field crew with application of field-based genetic tools may offer an effective and efficient approach to ensuring data accuracy in the future.

The skin color of the large yellow croaker (Larimichthys crocea) is a crucial indicator to determine its economic value. However, the location of pigment cells in the skin structure is uncertain. To determine the pigment cell type in the skin, the vertical order and ultrastructure of pigment cells were examined using light microscopy and transmission electron microscopy. Both dorsal and ventral skins comprise the epidermis, dermis, and hypodermis. Xanthophores, melanophores, and iridophores were observed in the dermis of the dorsal skin, whereas the latter two were in the dermis of the ventral skin. Interestingly, the size of xanthophores in the dorsal skin was significantly smaller than that of xanthophores in the ventral skin; however, the density of dorsal xanthophores was significantly higher than that of ventral xanthophores. The type L‐iridophores with large crystalline structures were observed in the uppermost area of the upper pigment layer, which contributed to the strikingly metallic luster shown by the ventral skin. The melanophores were exclusively found in the dorsal skin, offering the purpose of camouflage. Taken together, our results indicated that the pigment cells display different arrangement patterns between dorsal and ventral skin, and the golden color in the ventral skin results from the coexistence of light‐reflecting iridophores and light‐absorbing xanthophores. [ABSTRACT FROM AUTHOR]

The diverse and changing pigmentation of the skin allows fish to adapt to environmental conditions for survival and communication with conspecifics. However, various physical and chemical environmental factors, including pollutants, affect fish coloration. Therefore, the implementation of an analysis of skin pigmentation has been considered in fish well-being and ecotoxicological studies. A physiological color change is achieved by the motility of melanincontaining organelles: they aggregate into the perikaryon or disperse throughout the cytoplasm of melanophores in response to various stimuli. In our study, we addressed the issue of implementing the analysis of pigment dispersion in melanophores in stickleback skin to assess the response of fish to oxidative stress. We examined pigment dispersion in day and night skin samples collected from the dorsal, lateral and ventral regions. The degree of pigment dispersion we assessed by the melanophore index. The total number of melanophores counted in the defined skin area was significantly higher in the night samples than in the day samples. Only in day samples of dorsal skinwe observed the significant changes in pigment dispersion after exposure to stress: melanin was predominantly in the aggregated state. In the night samples, we did not report any response to stress in any part of the skin. Examination of pigment dispersion in melanophores in stickleback skin can be useful for assessing the welfare of fish and detecting toxic agents in the environment, but under specified conditions: in sticklebacks, it is analysis of dorsal skin during the day. [ABSTRACT FROM AUTHOR]

Bioluminescence is the ability of organisms to emit their own light which can be self-produced in light organs by photogenic cells (photocytes) or symbiotically by bearing cultures of luminous bacteria. Luminous animals are mainly comprised in the ocean, nocturnal coastal shallow-water species or, as the majority of species, inhabiting deep-sea where dim light conditions are optimal for communication by luminous signals. Due to difficult access to species, fisheries of bioluminescent fishes worldwide are rare, mostly for traditional cuisine and fishing bait. Fishes are the only bioluminescent vertebrates and thus their light organs present an astonishing level of complexity for light modulation to adequate light signals for specific ecological roles. Fishes control the output of light intensity using different mechanisms which can be categorized as being under control of hormonal or neuronal pathways. Usually, neural control allows fast and direct response to the photocytes while endocrinal systems allow to control the light produced by bacteria, via manipulation of individual melanophores. In some species, mechanical movement of melanophore-filled tissues by muscular action is under neuronal or hormonal control. Sexual dimorphism of light organs, driven by hormonal regulation during ontogeny, takes a crucial role in communication and reproductive success of these species. [ABSTRACT FROM AUTHOR]

Structural blue colors are common in animals, with the tissue nanostructures and material systems that produce them—especially bright blues—typically based on highly ordered nano‐architectures. In this study, we describe an unusually bright and angle‐independent structural blue from the skin of ribbontail stingray, arising from a more disordered array of scattering elements with a previously undescribed core–shell ultrastructure, involving nano‐vesicles enclosing guanine nano‐platelets. We show that this skin architecture functions as an intracellular photonic glass, coherently scattering blue, while broadband absorption from closely associated melanophores obviates the low color saturation typical for photonic glasses. Our characterization of skin ultrastructure and color in a stingray demonstrates how disordered systems can be harnessed to produce brilliant hues while illustrating that the capacity for guanine‐based colors likely arose extremely early in vertebrate evolution. Moreover, the material‐structure‐function associations underlying ribbontail stingray coloration, employing two distinct photonic phenomena, illustrate how the evolution of nanoscale architectures can have profound effects at much larger size scales (e.g., in visual ecology and communication), and provide fundamental guidelines for color‐saturated manmade photonic glasses. [ABSTRACT FROM AUTHOR]

Transparent immunodeficient animal models not only enhance in vivo imaging investigations of visceral organ development but also facilitate in vivo tracking of transplanted tumor cells. However, at present, transparent and immunodeficient animal models are confined to zebrafish, presenting substantial challenges for real-time, in vivo imaging studies addressing specific biological inquiries. Here, we employed a mitf−/−/prkdc−/−/il2rg−/− triple-knockout strategy to establish a colorless and immunodeficient amphibian model of Xenopus tropicalis. By disrupting the mitf gene, we observed the loss of melanophores, xanthophores, and granular glands in Xenopus tropicalis. Through the endogenous mitf promoter to drive BRAFV600E expression, we confirmed mitf expression in melanophores, xanthophores and granular glands. Moreover, the reconstruction of the disrupted site effectively reinstated melanophores, xanthophores, and granular glands, further highlighting the crucial role of mitf as a regulator in their development. By crossing mitf−/− frogs with prkdc−/−/il2rg−/− frogs, we generated a mitf−/−/prkdc−/−/il2rg−/−Xenopus tropicalis line, providing a colorless and immunodeficient amphibian model. Utilizing this model, we successfully observed intravital metastases of allotransplanted xanthophoromas and migrations of allotransplanted melanomas. Overall, colorless and immunodeficient Xenopus tropicalis holds great promise as a valuable platform for tumorous and developmental biology research. Xenopus tropicalis with triple knockout of mitf, prkdc, and il2rg is a colorless immunodeficient animal model. The mitf−/− frog further underscores the vital role of the mitf in the development of melanophores, xanthophores, and granular glands. [ABSTRACT FROM AUTHOR]

Southern Amazonia is one of the less-explored regions by anuran taxonomists. We describe a small new species of snouted treefrog, genus Scinax, from this region, from a fluvial archipelago in the Juruena River, state of Mato Grosso, Brazil. The description is based on external morphology of adults and tadpoles, advertisement call and molecular data. The species is phylogenetically related to other snouted treefrogs of the Scinax cruentomma species group and shows the most southeastern distribution in Amazonia among its close relatives. It is distinguished from congeners mainly by its larger adult body size and bilobate vocal sac that reaches the level of the pectoral fold, a reddish-brown horizontal stripe on the iris, dark melanophores or blotches on the vocal sac and the throat of females, and the uniformly brown posterior portion of the thigh. The advertisement call comprises one pulsed note emitted at regular intervals, with a duration of 189–227 ms, 30–35 pulses/note and a dominant frequency of 2,250–2,344 Hz. The type locality is suffering several environmental impacts, including illegal mining, overfishing, unsustainable agriculture, uncontrolled logging and degradation associated with the construction of new hydroelectric dams. Further study of the biology and regional distribution of the new species is required to propose mitigation measures needed for its conservation. [ABSTRACT FROM AUTHOR]

Larvae and juveniles of three species in the family Gobiidae are described based on laboratory-reared material: Bathygobius fuscus to post-settlement, Bathygobius cyclopterus to 2 days old, and Bathygobius petrophilus to just after hatching. Newly hatched larvae of these species are distinguishable from each other by the melanophore arrangements on the dorsal region of the trunk, ventrally near the tip of the tail, and along the lateral midline. The early development of Bathygobius fuscus was similar to that described previously for Bathygobius soporator but differed in the appearance of melanophores and the shape of the second dorsal fin and anal fin. [ABSTRACT FROM AUTHOR]

A new barbeled dragonfish, Eustomias shunyo sp. nov., is described based on three specimens [219.1–256.4 mm in standard length (SL)] collected at depths of 30–180 m from the Shatsky Rise in the western North Pacific. The new species is included in the subgenus Urostomias Regan and Trewavas 1930 and distinguishable from all congeners by the following combination of characters: 30 dorsal-fin rays; 48–49 anal-fin rays; 9–10 pectoral-fin rays; 7 pelvic-fin rays; 29–31 PV (photophores in ventral series between pectoral- and pelvic-fin insertions); 26–27 AC (photophores from dorsal to anal fin to end of row); 69–72 vertebrae; preanal length 63.7–65.3% SL; head length 9.7–10.1% SL; barbel length 12.2–13.7% SL; single luminous gland on upper margin of caudal fin; stem of barbel lacking external pigmentation except for its proximal portion, and melanophores sparsely scattered around small photophores on ventral side of stem; pale yellow patches arranged in 1 or 2 rows on dorsal and ventral sides of barbel stem; single or pared filaments on dorsal side of distal portion of barbel stem just before terminal bulb; single leaf-shaped dark patch on ventral side of barbel bulb. The revised diagnosis and a key to species of the subgenus Urostomias are presented. [ABSTRACT FROM AUTHOR]

The diverse and changing pigmentation of the skin allows fish to adapt to environmental conditions for survival and communication with conspecifics. However, various physical and chemical environmental factors, including pollutants, affect fish coloration. Therefore, the implementation of an analysis of skin pigmentation has been considered in fish well-being and ecotoxicological studies. A physiological color change is achieved by the motility of melanin-containing organelles: they aggregate into the perikaryon or disperse throughout the cytoplasm of melanophores in response to various stimuli. In our study, we addressed the issue of implementing the analysis of pigment dispersion in melanophores in stickleback skin to assess the response of fish to oxidative stress. We examined pigment dispersion in day and night skin samples collected from the dorsal, lateral and ventral regions. The degree of pigment dispersion we assessed by the melanophore index. The total number of melanophores counted in the defined skin area was significantly higher in the night samples than in the day samples. Only in day samples of dorsal skin we observed the significant changes in pigment dispersion after exposure to stress: melanin was predominantly in the aggregated state. In the night samples, we did not report any response to stress in any part of the skin. Examination of pigment dispersion in melanophores in stickleback skin can be useful for assessing the welfare of fish and detecting toxic agents in the environment, but under specified conditions: in sticklebacks, it is analysis of dorsal skin during the day.

The results of the study of the morphometric parameters of eggs and prelarvae of the Alaska plaice Pleuronectes quadrituberculatus in the northern part of the Sea of Okhotsk are presented. Incubation of eggs of the species from natural spawning collected in June 2021 was carried out. The diameter of eggs of the Alaska plaice ranges from 1.60 to 1.93 mm (on average, 1.75 mm). The results of our research in the northern part of the Sea of Okhotsk briefly supplement the information available in the literature on the parameters of the eggs and the morphology of the prelarvae of the Alaska plaice. The total length (TL) of newly hatched prelarvae of P. quadrituberculatus is equal to 6.48 mm with fluctuations of 5.70–7.25 mm. The general morphology of embryos and prelarvae of the Alaska place coincide with the descriptions available in the literature. At the same time, in those described by us, along with the pigmentation of the body with black melanophores, yellow pigment cells develop. The prelarvae of the Alaska plaice of the area studied differ from their peers in other areas by their large size and differentiated digestive tract. This paper presents for the first time photos of embryos and prelarvae of P. quadrituberculatus in the living state. Analysis of the levels and stages of development of Alaska plaice eggs suggests that, in the northern part of the Sea of Okhotsk, mass spawning of the species occurs in April and early May. [ABSTRACT FROM AUTHOR]

The pineal hormone melatonin is a multi-functional molecule with a recognized role in pigment aggregation in chromatophores, mediating its actions through binding to subtypes of its specific receptors. Since its discovery, melatonin has been known to be responsible for pigment aggregation towards the cell centre in fishes, including their embryos, as an adaptation to reduced light and thus results in pale body colouration. Diversity exists in the sensitivity of melanophores towards melatonin at interspecies, intraspecific levels, seasons, and amongst chromatophores at different regions of the animal body. In most of the fishes, melatonin leads to their skin paling at night. It is indicated that the melatonin receptors have characteristically maintained to show the same aggregating effects in fishes and other vertebrates in the evolutionary hierarchy. However, besides this aggregatory effect, melatonin is also responsible for pigment dispersion in certain fishes. Here is the demand in our review to explore further the nature of the dispersive behaviour of melatonin through the so-called β-melatonin receptors. It is clear that the pigment translocations in lower vertebrates under the effect of melatonin are mediated through the melatonin receptors coupled with other hormonal receptors as well. Therefore, being richly supplied with a variety of receptors, chromatophores and melanocytes can be used as in vitro test models for pharmacological applications of known and novel drugs. In this review, we present diverse effects of melatonin on chromatophores of fishes in particular with appropriate implications on most of the recent findings. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) such as superoxide radicals O2−, hydroxyl radicals OH−, and hydrogen peroxide H2O2 may have detrimental effects on marine organisms, including their integuments and visual appearances. Although some studies have described the impact of ROS on marine ecosystems and species ecology, the influence on the optical response of the integuments of marine species and on their visual appearances remains unknown. In this article, we used histology and optical characterisation to show, for the first time, that skin melanophores (melanin-containing chromophores) of the coral reef fish, Stegastes apicalis, change their shapes and fluorescent proprieties upon oxidation with H2O2 radicals. Our observations also suggest that pheomelanosomes may occur in fish integuments, where, previously, it was thought that fish melanosomes only contain eumelanin. This investigation relied on light and electron microscopy and steady-state fluorimetry, as well as time-resolved streak imaging systems. We suggest that the changes in the morphological and spectral characteristics of melanophores can be used as a marker of physiological stress induced by environmental factors such as ROS. Moreover, S. apicalis may be used as a potential model for studying the interaction between the surrounding environment and natural organisms in biologically diverse ecosystems, such as the Great Barrier Reef in Australia. [ABSTRACT FROM AUTHOR]

A Q‐switched laser system has been used in a single‐pulse mode for skin melasma treatments because of instant heat deposition in the target. Despite the efficient ablation of the melanophores in the skin, the single, high‐fluence pulse often causes undesirable damage to the surrounding tissue, leading to high recurrence rates. This study aims to investigate the feasibility of dual‐optical pulses with a temporal energy distribution on the melasma treatment in in vivo zebrafish models in comparison to that of the single optical pulse. Based on the optical detection, the dual‐optical pulses had a temporal energy distribution ratio of 4:1 and an interval of 61 μs between the two consecutive pulses. According to the histological analysis, the dual pulses removed melanophores and induced a few apoptotic nuclei with minimal recurrence. This study demonstrated that the feasibility of dual‐optical pulses (energy ratio = 4:1) could enhance the laser ablation performance in vivo. [ABSTRACT FROM AUTHOR]

In Colombia, glyphosate (GP) is used to control weeds, with Roundup Active® being the most widely used. This use has affected aquatic ecosystems, causing malformations in amphibians. The Savannah frog (D. molitor) is a tropical frog inhabiting the mountain of Colombia. In the present study, we determined the effect of sublethal concentrations of GP (Roundup Active®) on the skin of D. molitor. Twenty-four tadpoles were exposed to concentrations of GP (T1: 0, T2: 1.4, T3: 3.6, and T4: 5.6 a.e mg/L) during 31 days. In 10 individuals per treatment, two skin regions were evaluated: dorsal cranial and caudal ventral to determine histopathological alterations. Morphometric analysis of the layers of the skin was performed: epidermis, dermis, and hypodermis-muscular. T1 did not present histopathological alterations. Since T2 was identified, glandular cell hyperplasia and hypertrophy increased melanophores and melanin accumulations in the highest concentrations of GP. The ultrastructure revealed an increase in excretory glands in the dermis. In the other layers, an increase of melanophores and melanocyte clusters was observed accompanied by vacuolization of basal cells. The morphometry showed an increase in the thickness of the dermis in the dorso-cranial region in T2 compared to the other treatments, while the ventral caudal region exhibited a variation in the thickness of the dermis from T2 and a decrease in T4. Despite evaluating sublethal concentrations, the skin of D. molitor tadpoles presents histopathological, ultrastructural, and morphometric alterations that could affect the survival of the species in the natural environment. [ABSTRACT FROM AUTHOR]

Adhesive interactions are essential for tissue patterning and morphogenesis yet difficult to study owing to functional redundancies across genes and gene families. A useful system in which to dissect roles for cell adhesion and adhesion-dependent signaling is the pattern formed by pigment cells in skin of adult zebrafish, in which stripes represent the arrangement of neural crest derived melanophores, cells homologous to melanocytes. In a forward genetic screen for adult pattern defects, we isolated the pissarro (psr) mutant, having a variegated phenotype of spots, as well as defects in adult fin and lens. We show that psr corresponds to junctional adhesion protein 3b (jam3b) encoding a zebrafish orthologue of the two immunoglobulin-like domain receptor JAM3 (JAM-C), known for roles in adhesion and signaling in other developing tissues, and for promoting metastatic behavior of human and murine melanoma cells. We found that zebrafish jam3b is expressed post-embryonically in a variety of cells including melanophores, and that jam3b mutants have defects in melanophore survival. Jam3b supported aggregation of cells in vitro and was required autonomously by melanophores for an adherent phenotype in vivo. Genetic analyses further indicated both overlapping and non-overlapping functions with the related receptor, Immunoglobulin superfamily 11 (Igsf11) and Kit receptor tyrosine kinase. These findings suggest a model for Jam3b function in zebrafish melanophores and hint at the complexity of adhesive interactions underlying pattern formation.

The new anchovy Stolephorus horizon n. sp., described on the basis of 34 specimens collected from Fiji and Tonga, has been previously confused with Stolephorus indicus (van Hasselt, 1823) or Stolephorus scitulus (Fowler, 1911). However, the new species differs from both of the latter in having the pectoral fin without melanophores, and a unique range of gill rakers. A redescription of S. scitulus and an identification key of species previously identified as S. indicus are also provided. [ABSTRACT FROM AUTHOR]

The deep-sea environment is associated with a wide range of anatomically specialized morphologies allowing camouflage in this low or no light environment. Specialized ultra-black coloration has been documented in the pelican eel, Eurypharynx pelecanoides, but has not been explored in the other largely deep-sea inhabiting pelagic anguilloid eels. Histological examination of the integument revealed a layer of free melanosomes in the superficial dermis consistent with specialized ultra-black camouflage in the swallower eels Saccopharynx, the bobtail snipe eel Cyema, the sawtooth eels Serrivomer, and the snipe eels Avocettina and Nemichthys. The anatomy in these taxa is consistent with the previously described ultra-black morphology, except that Nemichthys, Avocettina, and Serrivomer have both large amounts of free melanosomes and melanophores. Consideration of this morphology in the context of anguilloid eel evolution in the deep-sea environment suggests repeated independent evolution of ultra-black coloration within the anguilloids, and greater development in the taxa more specifically associated with the bathypelagic habitats and the production of bioluminescence. [ABSTRACT FROM AUTHOR]

A new species of the genus Macrocephenchelys is described herein based on a single specimen collected from the deep‐sea trawl landing at Kalamukku fish landing centre, Kerala coast, Arabian Sea. The new species is distinguished by having a dorsal‐fin origin behind the middle of pectoral fin, a larger head, shorter trunk, larger gill opening, dorsal surface of body with dark‐brown colour and ventral surface of head and belly with numerous patches of melanophores before anus, vertebrae 14‐30‐151. The new species shares most of the characteristics with Macrocephenchelys brevirostris but differs from it by having a more anterior dorsal‐fin origin (vs. over the tip or slightly behind the pectoral‐fin tip), larger head [15.3% total length (TL) vs. 10.5%–13.9% TL, 53.2% pre‐anal length (PAL) vs. 35.8%–47.6% PAL], shorter trunk length (13.6% TL vs. 14.4%–20.6% TL, 47.3% PAL vs. 52.4%–66.2% PAL); further it shows 7.9%–8.1% genetic divergence from the sequences of M. brevirostris. [ABSTRACT FROM AUTHOR]

In this study, a new species of Rhyacoglanis is described from the Jamanxim River basin, Tapajós River basin. The new species differs from congeners based on the combination of the following diagnostic characters: two oblique dark bands formed by an agglomerate of melanophores on the predorsal region; dorsal confluence between the dark subdorsal and subadipose bands in large juveniles and adults; ventral confluence between the dark subadipose and caudal peduncle bands; body without conspicuous dark brown spots; complete dark band on caudal peduncle; body with three dark bands; a thin dark caudal-fin band; pectoral-fin spine with anterior serrae distributed along the entire margin; the posterior tip of the post-cleithral process reaching vertical through the base of the dorsal-fin spine; and hypural 5 free of hypural 3 and 4 and pointed caudalfin lobes. Additionally, our molecular phylogenetic results using ultraconserved elements (UCEs) corroborate the new species as Rhyacoglanis and sister to an undescribed species of Rhyacoglanis from the Xingu River basin. Moreover, as pointed out in previous studies, we confirm Cruciglanis as a sister group to Pseudopimelodus plus Rhyacoglanis. [ABSTRACT FROM AUTHOR]

We report the results of a taxonomic revision of the species of Bryconamericus from the Amazon River Basin of Peru, Ecuador, Bolivia and the Pacific coastal rivers of Peru. Based on morphological analyses, four valid species are recognized: B. bolivianus Pearson 1924, B. osgoodi Eigenmann & Allen 1942, B. pachacuti Eigenmann 1927 and B. phoenicopterus (Cope 1872). Three new species are described: B. lambayequensis sp. n. from the Cañariaco River, Pacific coast, Peru and two from the Amazon River Basin: B. abalio sp. n. from the Ucayali River drainage, Peru, and B. parapetiensis sp. n. from Itenez/Parapeti, Amazonia, Bolivia. Two species are synonymized and one was recently assigned to another genus: Bryconamericus alfredae is considered a junior synonym of Acrobrycon ipanquianus; Bryconamericus grosvenori is a junior synonym of B. bolivianus. A taxonomic key to these species of Bryconamericus and comments on the conservation status of the Amazonian and Pacific coast freshwater ichthyofauna are also included. [ABSTRACT FROM AUTHOR]

Saurida fortis sp. nov., a lizardfish (Aulopiformes: Synodontidae) from the northwestern Pacific Ocean, previously misidentified as Saurida umeyoshii Inoue and Nakabo 2006 and/or Saurida wanieso Shindo and Yamada 1972, is morphologically and genetically distinct from both species and described as new. It is characterized by the following combination of characters: dorsal-fin rays 11 or 12; lateral-line scales 53–56; vertebrae 51–54; pre-dorsal-fin scale rows 19–22; scale rows below lateral line 5.5; scale rows below lateral line with melanophores 3–5.5; pectoral fin moderately long, its length 12.5–16.9% of standard length (SL), tip of fin just short of or extending slightly beyond P–D line; pelvic girdle width 8.0–11.1% SL; anterior end of base of anteriormost gill raker on lower gill arch located behind posterior end of basibranchial/hypobranchial junction, with gap between gill raker and junction subequal in length to 1–3 gill-raker bases; body dark brown dorsally, silvery-white ventrally, with a row of poorly defined brownish-black blotches along lateral line and a pair of similar blotches posterior to both dorsal- and adipose-fin bases; scale pockets below lateral line with melanophores (usually absent anterior to pelvic-fin bases, rarely present in adults), melanophore number decreasing ventrally and increasing with growth; single row of indistinct black spots along caudal-fin upper margin. [ABSTRACT FROM AUTHOR]

Some freshwater teleost fish have pigment cells whose arrangement and shape are affected by the environment. Natural light has a wide range of light intensity. Fish are sensitive to the background and exposed light colour. Fish body colour is a significant criterion in fixing its market value, whether it is ornamental or edible. By favourable light exposure, a culturist may get a good market value of fish on most ethical grounds. In this study, we recorded the changes in melanophore response with the changes in light colour on Channa punctata. Adult fish were treated with monochromatic lights (darkness, white, blue and red light) for 5 and 28 days. After treatment, their body colour and melanophore size, number, length and the number of dendrites were studied. The results showed a significant influence of monochromatic light on melanophore arrangement in fish skin. The data showed that blue light is appropriate for the overall species colour of photic C. punctata. Continuous black or white light caused severe damage to the fish's appearance. [ABSTRACT FROM AUTHOR]

This research study obtained the first morphological description of the Colorado snapper (Lutjanus colorado) larvae assisted by DNA barcoding as a molecular identification tool. Sixteen Lutjanidae larvae were separated from zooplankton samples and selected for this study. A fragment of the mitochondrial gene cytochrome oxidase subunit I (COI) of 658 bp was used in the analyses of intra‐ and interspecific genetic divergences; a neighbour‐joining tree (NJ) of K2P distances was performed with reference sequences of 15 Lutjanidae species from the Northeastern Tropical Pacific. Genetic divergences and the NJ tree identified 16 larvae as L. colorado. Morphological investigations of larvae at different developmental stages were performed; similarities and differences are discussed in comparison to four species described previously for the Northeastern Pacific. Pigmentation patterns were the best diagnostic features, particularly the caudal melanophores, at least up to 12.4 mm body length. [ABSTRACT FROM AUTHOR]

Oscar Astronotus ocellatus (Agassiz, 1831), an Amazonian cichlid, has normal and amelanism varieties, but studies on its amelanism mechanism are scarce. Here, we investigated the ultrastructure, metabolome, and transcriptome profiles of skin from normal and amelanistic individuals. We found more stellate-shaped melanophores, mature melanosomes and melanin in normal, but less melanin, oval-shaped melanophores and immature melanosomes in amelanistic individuals. A significant separation in metabolome between normal and amelanism was observed. Pathways, e.g., biosynthesis of amino acids and unsaturated fatty acids, of differentially expressed metabolites (DEMs) involved in were significantly enriched. Transcriptome showed 323 differentially expressed genes (DEGs), of which stmn4, tyr, tyrp1, prkca, dusp8, hsp70, and wls were involved in melanin-related pathways especially tyrosine metabolism. Several classical melanin-related genes including slc24a5, acdy2, and acdy6 harbored non-synonymous SNPs in the functional domains. Integration of transcriptome and metabolome showed 18 strong correlations between DEMs and DEGs, e.g., between l-Proline and cds1, styk1, fam83b, and gimap7, between phosphorylcholine/N-alpha-Acetyl-l-lysine and myh, mical2b and mical3a, and between biopterin and dusp8. This study characterized the difference of skin melanophore, melanosome and melanin content between normal and amelanistic Oscar, and identified some candidate amelanism-related genes, metabolites and pathways, helping to understand its amelanism mechanisms. [ABSTRACT FROM AUTHOR]

Aposematism continues to be a phenomenon of central interest in evolutionary biology. The life history of the mimic poison frog, Ranitomeya imitator, relies heavily on aposematism. In order for aposematic signals to be effective, predators must be able to learn to avoid the associated phenotype. However, in R. imitator, aposematism is associated with four different color phenotypes that mimic a complex of congeneric species occurring across the mimic frog's geographic range. Investigations of the underlying mechanics of color production in these frogs can provide insights into how and why these different morphs evolved. We used histological samples to examine divergence in the color production mechanisms used by R. imitator to produce effective aposematic signals across its geographic range. We measured the coverage of melanophores and xanthophores (the area covered by chromatophores divided by total area of the skin section) in each color morph. We find that morphs that produce orange skin exhibit a higher coverage of xanthophores and lower coverage of melanophores than those that produce yellow skin. In turn, morphs that produce yellow skin exhibit a higher coverage of xanthophores and lower coverage of melanophores than those that produce green skin. Generally, across the morphs, a high ratio of xanthophores to melanophores is associated with colors of brighter spectral reflectance. Together, our results contribute to the understanding of color production in amphibians and document divergence in the histology of a species that is subject to divergent selection associated with aposematism. [ABSTRACT FROM AUTHOR]

Two specimens representing the first known adults of Lestidiops indopacificus (Ege, 1953) are reported and described from Taiwan, and the validity and generic assignment of this species are confirmed. The origin of the pelvic fin directly below the dorsal-fin base shows that L. indopacificus belongs to the L. mirabilis species complex. It can be separated from its congeners by the position of the nostrils above the posterior end of the maxilla, the light body color with unevenly distributed melanophores in adults, and a distinct combination of meristic values and other morphological characteristics. New geographic records are reported for the two other current members of this species complex, L. mirabilis (Ege, 1933) and L. extremus (Ege, 1953). The diagnostic features that separate these three very similar species are discussed. [ABSTRACT FROM AUTHOR]

Groups of zebrafish (Danio rerio) embryos receive radiations of different frequencies and intensities by means of new prototype devices. They are exposed to static (B0, 0 Hz), extremely low-frequency (ELF, 0.2 Hz), low-frequency (LF, 270 kHz), very-high-frequency (VHF, 100 MHz), and ultra-high-frequency (UHF, 900 MHz) field irradiations. The applied magnetic field intensities are 40 mT at 0 Hz, 40 mT at 0.2 Hz, 470 μT at 270 kHz, 240 nT at 100 MHz, and 240 nT at 900 MHz. Such combinations are meant to cover environmental radiations from geomagnetic fields and cosmic magnetism to electromagnetic radiation of electronic instruments such as GSM and UMTS transmission-mode mobile systems. For each frequency, fish are monitored for up to 5 days. Unexposed embryos are used as controls. Notably, exposure to the different radiations brings alterations of body pigmentation in zebrafish embryos and larvae in terms of total number, area, and morphology of (black) melanophores. This research may contribute to evaluating the roles and effects of magnetic radiation on living matter. [ABSTRACT FROM AUTHOR]

Melatonin influences mammalian coat colour and hair follicle pigmentation and also weakly alters the electrical stimulation of retinal cells in the eyes. A direct melanocytic response to melatonin is still uncertain in mammals and human skin pigmentation. Melatonin acts as a free radical scavenger and thus inhibits the initiation of cancer cell growth. Treatment of melanoma sees perspective features in the administration of melatonin along with known chemotherapeutic molecules to improve the efficacy of conventional cytotoxic agents. Being richly supplied with a variety of receptors, melanocytes and melanoma cells can be used as in vitro test models for pharmacological applications of known and novel drugs. [ABSTRACT FROM AUTHOR]

We report the results of a taxonomic revision of the species of Bryconamericus from the Amazon River Basin of Peru, Ecuador, Bolivia and the Pacific coastal rivers of Peru. Based on morphological analyses, four valid species are recognized: B. bolivianus Pearson 1924, B. osgoodi Eigenmann & Allen 1942, B. pachacuti Eigenmann 1927 and B. phoenicopterus (Cope 1872). Three new species are described: B. lambayequensis sp. n. from the Cañariaco River, Pacific coast, Peru and two from the Amazon River Basin: B. abalio sp. n. from the Ucayali River drainage, Peru, and B. parapetiensis sp. n. from Itenez/Parapeti, Amazonia, Bolivia. Two species are synonymized and one was recently assigned to another genus: Bryconamericus alfredae is considered a junior synonym of Acrobrycon ipanquianus; Bryconamericus grosvenori is a junior synonym of B. bolivianus. A taxonomic key to these species of Bryconamericus and comments on the conservation status of the Amazonian and Pacific coast freshwater ichthyofauna are also included.

Bioluminescence is a common ecological trait among many marine organisms, including three shark families: Etmopteridae, Dalatiidae, and Somniosidae. The kitefin shark, Dalatias licha (Bonnaterre, 1788), from the Dalatiidae family is the largest known luminous vertebrate. This study compares the light organ ultrastructure of D. licha with that of Etmopterus spinax, the type species of Etmopteridae, to gain a deeper understanding of the light emission process and its evolutionary conservation within shark families. The ultrastructure of D. licha's photophores and the morphological changes that occur after hormonal stimulation (via melatonin and α-MSH, which stimulate or inhibit the bioluminescence, respectively) were examined. The photophores consist of a spherical pigmented sheath surrounding a unique, regionalized light-emitting cell (photocyte). The photocyte's basal area contains a specific area filled with granular inclusions that resemble the glowon-type microsources of E. spinax, suggesting that this area is the intracellular site of light emission. An acidophilic secretion, not present in Etmopteridae, is also observed within the granular area and may be involved in photogenesis. The ultrastructure analysis reveals no lens cells or reticular layer, unlike in Etmopteridae photophores, indicating a simpler organization in Dalatiidae photophores. Melatonin stimulation causes the removal of pigments from the photophore-associated melanophores and an increase in the granular inclusion diameter and coverage in the granular area, further showing that this last area is the potential site of light emission, while α-MSH stimulation causes the extension of the melanophore pigments and a decrease in the granular inclusion diameter and coverage. These results support the evolutive conservation of photophore functional organization across luminous etmopterid and dalatiid sharks. [ABSTRACT FROM AUTHOR]

Phenacostethus sikat, new species, is described from coastal drainages of Kalimantan Selatan, the southeastern province of Indonesian Borneo, that flow into the Java Sea and the Straits of Makassar. This discovery and description brings the number of valid species of priapiumfishes, the atheriniform subfamily Phallostethinae, to 24 and extends the known distribution of the phallostethines to drainages on the eastern margin of the modern Sunda Shelf. Phenacostethus sikat differs from congeners in features of the priapium, the complex bilaterally asymmetric, subcephalic copulatory organ of males, and is readily distinguished by a unique, brush-shaped seminal papilla in males, as opposed to a simpler, ruffled seminal papilla in Phe. smithi, its inferred sister species based on morphology, and a smooth seminal papilla in males of Phe. posthon and Phe. trewavasae. Males of Phe. sikat and Phe. smithi are either sinistral or dextral, the hooked toxactinium arises on the right or left side of the head and curves strongly under the head towards the aproctal side of the body. Males of Phe. posthon and Phe. trewavasae are exclusively dextral or sinistral, respectively. Males of Phe. sikat have an ossified inner pulvinular bone which is cartilaginous or absent in Phe. smithi. Males of Phe. sikat and Phe. smithi have a curved and pointed or blunt second ctenactinium as opposed to a highly reduced second ctenactinium in males of Phe. posthon and Phe. trewavasae. Females of the new species lack rudimentary pelvic fins which are present in adult females of Phe. smithi, Phe. posthon, and Phallostethus. The new species is also diagnosed by a colour pattern with few or no melanophores along the horizontal septum anterior to the anal-fin origin. The mtCOI sequences of Phe. sikat differ from those of congeners by 13.85-24.23%, with an average of 21.54%, an extraordinarily high level of divergence comparable to that of other diminutive fishes. Like congeners, Phe. sikat is a miniature species. The largest specimen known is an adult female just 15.3 mm SL. [ABSTRACT FROM AUTHOR]

In this study, the early development of Cobitis striata fuchigamii was described using aquarium-spawned eggs and juveniles. Egg yolk diameter after water absorption was 1.0‒1.1 mm, and the spherical, demersal eggs had a light-yellow yolk, no oil droplets, and low viscosity. Newly hatched larvae [4.0–4.5 mm in total length (TL)] had 44‒45 (27‒28 + 17‒18) myomeres (26‒27 between the pectoral fins and the middle of the anus), two pairs of short tubular outer gill filaments on the cheek, and only a few melanophores on parts of the eye. Notochord flexion began at 5.1–6.8 mm TL and ended at 10.0 mm TL. The number of fin rays on each fin was finalized at approximately 25.0 mm TL. Lateral line spots of the larvae were indistinct, and juveniles formed blotches at approximately 25.0 mm TL. The barbels were formed in the following order: third, second, and then first. The formation of membranous fins occurred in the following order: pectoral, caudal, dorsal, anal, and then pelvic; full fin ray complements occurred in the caudal, dorsal, anal, pectoral, and pelvic regions. Some individuals (5.1–7.5 mm TL at the flexion stage) had free lateral neuromasts on the caudal region, each with a short cupula. [ABSTRACT FROM AUTHOR]

Larvae and juveniles of three species in the family Gobiidae were described based on reared material; Priolepis borea survived to post-settlement, and Priolepis cincta and Priolepis latifascima to seven days after hatching. Newly hatched larvae of Priolepis are distinguishable from each other by the presence or absence of melanophores on the yolk, ventral part of the abdomen, posterior angle of the lower jaw, and dorsal region of the body. The presence of a row of melanophores on the ventral part of the body and xanthophores may be useful to identify the genus. [ABSTRACT FROM AUTHOR]

Chinese soft-shelled turtle (Pelodiscus sinensis) is an important freshwater breeding species in East and Southeast Asia. The most external differences among different strains are skin pigmentation and blotches, but the mechanism of their formation is unknown. To investigate the mechanism of skin pigmentation diversity in Chinese soft-shelled turtle, three unique phenotypes (Golden strain, Japanese strain and Qingxi black strain) were selected to observe the chromatophores, and the transcriptome and metabolome were compared. The results showed the presence of melanophores, xanthophores and iridophores in the skin of all three strains. However, there were differences in the composition and organelles of chromatophores. The upregulation of gene asip and elevated accumulation of glutathione and cysteine in Golden strain resulted in the production of pheomelanin, leading to yellow pigmentation in the skin. The upregulation of gene dct and elevated accumulation of indole-5, 6-quinone in Qingxi black strain resulted in the production of eumelanin, which made the skin appear black-brown. Japanese strain produced eumelanin and pheomelanin, however, the presence of melanosomes resulted in skin darkening and appeared dark green pigmentation. The white blotches of Gloden strain and Japanese strains were formed through increased production of iridophores, while the black blotches of Qingxi black strain were formed by inducing migration and apoptosis of melanophores within iridophores. In conclusion, the distinctive characteristics of the skin in three strains resulted from combination of melanin type, abundance of melanosomes and interaction between melanophores and iridophores. These results provided valuable reference for investigating the mechanisms underlying skin pigmentation diversity in Chinese soft-shelled turtle and other vertebrates. • Pheomelanin is the primary factor contributing to the yellow skin pigmentation of Golden strain. • Eumelanin is the main reason for the dark-brown skin pigmentation of Qingxi black strain. • Japanese strain produce both eumelanin and pheomelanin, while melanosomes darken skin pigmentation. • White blotches are formed by reflection from iridophores, while black blotches are attributed to the migration and apoptosis of melanophores induced by iridophores. [ABSTRACT FROM AUTHOR]

Morphological development in laboratory-hatched larval and juvenile Rhinogobius flumineus is described. Body lengths (BL) were 5.7 ± 0.1 (mean ± SD) mm just after hatching, reaching 8.9 ± 0.1 mm by day 11, 11.9 ± 0.1 mm by day 24 and 14.7 ± 0.4 mm by day 42. Notochord flexion began before hatching and its flexion was completed on day 1 after hatching (ca. 6.4 mm BL), and yolk completely absorbed by day 9. Body proportions tended to become mostly constant in juvenile stage. Fin-rays of the 2nd dorsal and caudal fins were present at hatching, and those of other fins appeared almost simultaneously, rapidly increased and attained full complements by 6.8–6.9 mm BL on day 9. Melanophores were few on the body during days 0–3 but increased with growth and covered the entire body surface in juveniles larger than ca. 9.0 mm BL at 11 days after hatching. These features are considered to reflect the ecological differences between R. flumineus as a fluvial species and amphidromous/lentic congeners across the genus. [ABSTRACT FROM AUTHOR]

The parental care of the nests and the embryonic and larval development of the labrisomid blenny Labrisomus philippii (Teleostei: Labrisomidae) were described for the first time. In situ underwater recordings were done on nests deposited at 2‐m depth at Pisagua and Sarmenia, northern Chile. The nests were composed by a mass of adhered eggs, exclusively on red algae covers (Rhodophyta) outside the crevices used by the adult and guarded by the male. Males utilized ~90% of the time taking care of the nest, defending it from predators (other fish and crustaceans), and keeping it clean. For the observation of larvae, egg masses were extracted from the nests and incubated in the laboratory. Eggs are spheroid, 1.09–1.23 mm in size, with filaments originating from a central thallus in the basal pole, small perivitelline space and granular yolk, with numerous small oil droplets. Larvae hatched at an average size of 5.06 ± 0.10 mm body length (BL), with a functional mouth, and a round yolk‐sac of 0.09 mm3. Larvae are elongated, slightly laterally compressed, with a round and moderate head and a short snout. They have preopercular spines and 35 myomeres; melanophores are located on the cleithrum symphysis, over the head, along the base of the anal fin, between pterygiophores of the dorsal ray fin, and in the ventral margin of the gut. During development, larvae grew at 0.28 mm d−1. Finally, this research helped to increase knowledge on early‐life history traits of this coastal fish inhabiting rocky shores along the south Pacific Ocean. [ABSTRACT FROM AUTHOR]

The capture of a female specimen of the velvet belly lantern shark Etmopterus spinax with abnormal skin coloration is reported. The specimen was captured off northern Spain (Bay of Biscay, North‐eastern Atlantic) in 2021 by bottom trawling. The lack of dermal melanophores combined with a normal retinal pigmentation, lead us to considerate the specimen as leucistic. This is the first case of leucism in E. spinax and the second record of colour aberration in the family Etmopteridae. A comprehensive updated review of published literature on albinism and leucism in chondrichthyans is also provided. [ABSTRACT FROM AUTHOR]

Several morphometric characters with observing general morphology of laboratory-reared larval and juvenile Puntioplites proctozysron (9–40-day-old, 6.8 to 23.4 mm body length, BL) were observed. All myomeres were observable in day 9 flexion larvae. The body proportions tended to become constant in juveniles except for the body depth and upper jaw length that increased continuously. Dorsal and caudal fin-rays already appeared in day 9 larvae, followed by anal, pelvic and pectoral fins, and overall aggregate fin-ray numbers attained full complements by 13.7 mm BL on day 35. Melanophores were scarce in day 9 larvae except those on head, those appeared on trunk and increased in postflexion larvae > 11.0 mm BL, covering whole trunk above lateral line in juveniles. [ABSTRACT FROM AUTHOR]

The present study was carried out to investigate the optimum stocking density for gonadal development, pigmentation, and survival of Carassius carassius stocked at varying stocking densities under a biofloc-based system. C. carassius (25 ± 0.15 g) were randomly distributed in sixteen tanks, each with 250 L water at the stocking densities viz. 1 kg/m3, 2 kg/m3, 3 kg/m3, 4 kg/m3 (10, 20, 30 and 40 fish/250 L). The carbon‑nitrogen ratio of 15:1 was maintained using wheat flour as a carbon source. The best gonad performance in terms of absolute fecundity (4449.98 ± 115.636), relative fecundity (114.67 ± 2.770), GSI (5.62 ± 0.018 and 2.93 ± 0.014 for females & males respectively), and advanced maturation stages (vitellogenic oocytes and seminiferous tubules with spermatozoa) was observed in the density treatment having 20 fish/250 L. The skin carotenoid content showed an increasing trend with maximum content (8.11 ± 0.018 μg/g)) recorded for the fish stocked at 20/250 L. The scales of the fish from the same treatment presented a higher concentration of yellow orange pigments giving an overall golden hue to the scales while as the density and dispersion of melanophores increased with an increase in stocking density giving an overall darker coloration to the fish, indicating a stressful condition at higher stocking density. The survival rate of fish showed no significant difference (p ≥0.05) between the various density groups. The results of this experiment elucidate that Carassius carassius could be cultured with better gonad performance, increased carotenoid content, and high survival at a stocking density of 2 kg/m3 in a biofloc system. [Display omitted] • Floc volume significantly affects the reproductive performance and pigmentation. • At higher fish density in Biofloc system, advanced stages of gonadal maturity are seen. • Carotenoid content in fish skin improves at higher stocking density, employing BFT. • In biofloc system, stocking density is an impact factor beyond a certain limit. • Higher dispersion of scale melanophores is seen as stocking density exceeds a limit. [ABSTRACT FROM AUTHOR]

Macrophages have diverse functions in immunity as well as in development and homeostasis. We identified a function for these cells in long-distance communication during postembryonic tissue remodeling. Ablation of macrophages in zebrafish prevented melanophores from coalescing into adult pigment stripes. Melanophore organization depends on signals provided by cells of the yellow xanthophore lineage via airinemes, long filamentous projections with vesicles at their tips. We show that airineme extension from originating cells, as well as vesicle deposition on target cells, depend on interactions with macrophages. These findings identify a role for macrophages in relaying long-range signals between nonimmune cells. This signaling modality may function in the remodeling and homeostasis of other tissues during normal development and disease.

Groups of zebrafish (Danio rerio) embryos receive radiations of different frequencies and intensities by means of new prototype devices. They are exposed to static (B0, 0 Hz), extremely low-frequency (ELF, 0.2 Hz), low-frequency (LF, 270 kHz), very-high-frequency (VHF, 100 MHz), and ultra-high-frequency (UHF, 900 MHz) field irradiations. The applied magnetic field intensities are 40 mT at 0 Hz, 40 mT at 0.2 Hz, 470 μT at 270 kHz, 240 nT at 100 MHz, and 240 nT at 900 MHz. Such combinations are meant to cover environmental radiations from geomagnetic fields and cosmic magnetism to electromagnetic radiation of electronic instruments such as GSM and UMTS transmission-mode mobile systems. For each frequency, fish are monitored for up to 5 days. Unexposed embryos are used as controls. Notably, exposure to the different radiations brings alterations of body pigmentation in zebrafish embryos and larvae in terms of total number, area, and morphology of (black) melanophores. This research may contribute to evaluating the roles and effects of magnetic radiation on living matter.

In nature, most Paramisgurnus dabryanus are grey‐black (grey‐black loach), although there is a mutant (albino) in the breeding population with a 'golden colour' (golden loach). There are no reports of early body colour formation in albino fishes. In this study, the differences in body colour characteristics between normal body colour P. dabryanus and albino P. dabryanus were compared by comparing body colour formation, skin and fin pigment cells of two body colours of P. dabryanus. It was found that the order of appearance of pigment cells in grey‐black loach and golden loach was melanophores, xanthophores, erythrophores, and finally, iridophores; the composition of the pigment cells in the fins and the skin tissue were essentially the same. However, there were no melanophores in the skin of the golden loach. The melanophores of grey‐black loach skin were distributed with a large number of melanosomes of high electron density; the xanthophore and erythrophores were spherical and contained pteridine vesicles. Melanophores and xanthophores are distributed in both the epidermis and dermis of the grey‐black loach, and the xanthophores of the golden loach are distributed between the scales and the epidermis, and between the dermis and the muscle layer. In this study, we elucidated the body colour composition and pigment cell characteristics of the two body colours of P. dabryanus. Our study provided a scientific basis for the research for fish body colour variation. [ABSTRACT FROM AUTHOR]

We performed systematic surveys for members of the Eurycea quadridigitata (Dwarf Salamander) complex in Georgia to determine the distribution of member species. Over 409 person-hours of search effort, we sampled 211 locations in 38 counties, detecting 108 individuals, including many that bridge substantial distribution gaps. Molecular data document Georgia specimens belong to 2 species, E. hillisi and E. quadridigitata. No specimens attributable to E. chamberlaini were found in Georgia, indicating this species has a distribution restricted to South and North Carolina. We used color patterns and measures of body size and shape of specimens identified by molecular methods to separate 4 species of 4-toed Eurycea from the Coastal Plain of Alabama, Florida, Georgia, South Carolina, and North Carolina. Large body size and the presence of melanophores across the chin and surrounding the cloaca separated E. quadridigitata from all others. Additionally, E. sphagnicola and E. quadridigitata possessed dark sides to the body and tail, with these features being disrupted by irregular white stripes or spots. In contrast, E. chamberlaini and E. hillisi possessed light sides to the body and tail that lacked irregular white stripes. Small body size distinguished E. sphagnicola from E. quadridigitata, but no feature distinguished E. chamberlaini from E. hillisi. [ABSTRACT FROM AUTHOR]

The function and regulation of female nuptial colour signals are poorly understood. In fish, colour is often mediated by chromatophores, allowing for rapid and versatile signalling. Here, we examine a distinct but temporary black line around the eyes and snout ('dark eyes') displayed by female sand gobies before spawning and never observed in males. We investigate the regulatory mechanism of the display by analysing the number of melanophores in both sexes in vitro and their response to hormonal exposure. We also test the hypothesis that dark eyes serve an anti-glare function and focus the line of sight, by analysing the frequency, intensity and duration of the display in bright and dim light, with and without males present. We show that the sexes do not differ in terms of the number of melanophores, but that males and females respond in different ways to exposure to melanocyte-stimulating hormone, which has a stronger dilatory effect in females and results in a darker line. However, the darkness of the iris is not affected. Neither light levels nor the presence of potential mates affect the frequency of the dark eye display, but the display is longer lasting and more intense in the presence of smaller nest-holding males. [ABSTRACT FROM AUTHOR]