Arrangement Of Chromatophores Research Articles

Species Delimitation of Argonauta Paralarvae Reveals an Extensive Morphological Variability in the Northern Humboldt Current System

Argonauts or paper nautiluses are pelagic octopod cephalopods with a cosmopolitan distribution in tropical and subtropical waters around the world. Unlike other species of octopus, these are characterized by the fact that the female has a shell that serves as the breeding chamber for the eggs. Over time, this structure has been used as a taxonomic diagnostic character, causing problems in the systematics of this genus, with around 50 synonymies reported. Only two species, Argonauta argo and A. nouryi, have been reported in the Northern Humboldt Current System; however, there is taxonomic uncertainty regarding these species, which is reflected in the paralarvae (the first stage of life after hatching). In the paralarvae, the chromatophore patterns are considered to be conservative and reliable taxonomic characteristics. The objective of this study is to demonstrate the extensive variability in the chromatophore arrangement of Argonauta paralarvae in the Northern Humboldt Current using DNA barcoding and five species delimitation models. Our results include up to 11 different paralarvae morphotypes according to the pattern of chromatophores (number and arrangement) and 2 shell morphotypes. Species delimitation methods divided the 13 Argonauta morphotypes into two consensus molecular taxonomic units (MOTUs), A. argo and A. nouryi. Additionally, the results revealed an extensive morphological variability in the paralarvae and female shells of A. nouryi, demonstrating the importance of molecular data in studies involving species with different life stages, especially when this extensive morphological variability obscures conventional analyses.

Light-Writing & Projecting Multicolor Fluorescent Hydrogels for On-Demand Information Display.

Intelligent rewritable display systems have been long-expected to reduce the heavy consumption of single-use or transient devices in the age of Internet-of-Things. However, it remains challenging to construct such systems with integrated functionality of remote control, rapid activation, multicolor and multimode display. Herein, by learning from the unique multilayer arrangement of chromatophores in chameleon skins, we present a promising kind of rewritable hydrogel multicolor systems that can combine the merits of near-infrared (NIR) light-writing & projecting modes for on-demand information display. Specifically, the systems have typical multilayer layout consisting of PDMS-sealed carbon nanotubes (CNTs) film as photothermal control unit and embedded fluorescent hydrogels as multicolor display unit, in which thermo-responsive hydrogel is constrained within non-responsive hydrogel. Such rational structure design results in the establishment of one promising display mechanism via the cascading "light trigger-heat generation-fluorescence output" process. On this basis, rapid and reversible hand-written display of arbitrary information is achieved within 5 s. Also, sustainable light-projecting display of predesigned multicolor patterns is demonstrated due to the multilayer design that ensures easy patterning of photothermal control or hydrogel display layer. This study brings functional-integrated merits for novel rewritable display systems and open new possibility to construct high-end products for information display/transmission. This article is protected by copyright. All rights reserved.

The Estrogen-Responsive Transcriptome of Female Secondary Sexual Traits in the Gulf Pipefish.

Sexual dimorphism often results from hormonally regulated trait differences between the sexes. In sex-role-reversed vertebrates, females often have ornaments used in mating competition that are expected to be under hormonal control. Males of the sex-role-reversed Gulf pipefish (Syngnathus scovelli) develop female-typical traits when they are exposed to estrogens. We aimed to identify genes whose expression levels changed during the development and maintenance of female-specific ornaments. We performed RNA-sequencing on skin and muscle tissue in male Gulf pipefish with and without exposure to estrogen to investigate the transcriptome of the sexually dimorphic ornament of vertical iridescent bands found in females and estrogen-exposed males. We further compared differential gene expression patterns between males and females to generate a list of genes putatively involved in the female secondary sex traits of bands and body depth. A detailed analysis of estrogen-receptor binding sites demonstrates that estrogen-regulated genes tend to have nearby cis-regulatory elements. Our results identified a number of genes that differed between the sexes and confirmed that many of these were estrogen-responsive. These estrogen-regulated genes may be involved in the arrangement of chromatophores for color patterning, as well as in the growth of muscles to achieve the greater body depth typical of females in this species. In addition, anaerobic respiration and adipose tissue could be involved in the rigors of female courtship and mating competition. Overall, this study generates a number of interesting hypotheses regarding the genetic basis of a female ornament in a sex-role-reversed pipefish.

Bar, stripe and spot development in sand-dwelling cichlids from Lake Malawi

BackgroundMelanic patterns such as horizontal stripes, vertical bars and spots are common among teleost fishes and often serve roles in camouflage or mimicry. Extensive research in the zebrafish model has shown that the development of horizontal stripes depends on complex cellular interactions between melanophores, xanthophores and iridophores. Little is known about the development of horizontal stripes in other teleosts, and even less is known about bar or spot development. Here, we compare chromatophore composition and development of stripes, bars and spots in two cichlid species of sand-dwellers from Lake Malawi—Copadichromis azureus and Dimidiochromis compressiceps.Results(1) In D. compressiceps, stripes are made of dense melanophores underlaid by xanthophores and overlaid by iridophores. Melanophores and xanthophores are either loose or absent in interstripes, and iridophores are dense. In C. azureus, spots and bars are composed of a chromatophore arrangement similar to that of stripes but are separated by interbars where density of melanophores and xanthophores is only slightly lower than in stripes and iridophore density appears slightly greater. (2) Stripe, bar and spot chromatophores appear in the skin at metamorphosis. Stripe melanophores directly differentiate along horizontal myosepta into the adult pattern. In contrast, bar number and position are dynamic throughout development. As body length increases, new bars appear between old ones or by splitting of old ones through new melanophore appearance, not migration. Xanthophore and iridophore distributions follow melanophore patterns. (3) Metamorphic pigmentation arises in cichlids in a fashion similar to that described in zebrafish: melanophore progenitors derived from the medial route of neural crest migration migrate from the vicinity of the neural tube to the skin during metamorphosis.ConclusionThe three pigment cell types forming stripes, bars and spots arise in the skin at metamorphosis. Stripes develop by differentiation of melanophores along horizontal myosepta, while bars do not develop along patent anatomical boundaries and increase in number in relation with body size. We propose that metamorphic melanophore differentiation and migratory arrest upon arrival to the skin lead to stripe formation, while bar formation must be supported by extensive migration of undifferentiated melanophores in the skin.

Chromatophore arrangement and photophore formation in the early development of swordtip squid Uroteuthis (Photololigo) edulis

The commercially valuable swordtip squid Uroteuthis (Photololigo) edulis has recently experienced a decline, indicating a need for its management. However, very little is known about its morphology during early developmental stages. Therefore, in this report, we describe the chromatophore arrangement and photophore formation in laboratory-reared specimens ranging from 2.2 to 13.6 mm in dorsal mantle length (DML). We observed seven characteristic chromatophore arrangements and a pair of photophores on the ventral surface of the ink sac in the five developmental stages after hatching, which allow U. edulis hatchlings and paralarvae to be distinguished from other sympatric loliginid squids around the coastal area of central Japan. We also found an increase in the number of other chromatophores and rapid growth of the photophores between 7 and 9 mm in DML, which marks the transition between the paralarva and juvenile stages. These findings will be useful for identifying U. edulis hatchlings and paralarvae from natural plankton samples, thus contributing toward research on the spatial distribution, seasonal migration, and predicted spawning grounds of this species.

A Polarized Viewpoint?

Invertebrates, like vertebrates, use the light-activated heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor (GPCR) rhodopsin as a photoreceptor in visual signal transduction. Unlike vertebrate rhodopsin, which signals through transducin, invertebrate rhodopsin signals through G q -type G proteins to stimulate an inositol 1,4,5-trisphosphate-based signaling pathway (see Schertler). Murakami and Kouyama determined the 2.5 Å resolution crystal structure of squid rhodopsin, shedding new light on mechanisms of signaling involving this GPCR family. Crystallization of truncated squid rhodopsin (lacking a C-terminal extension that is not involved in signal transduction) revealed two cytoplasmic helices as well as the seven transmembrane helices characteristic of GPCRs. Transmembrane helices V and VI projected 25 Å into the cytoplasm to form, together with cytoplasmic helices VIII and IX, a structure that is not present in bovine rhodopsin, which the authors propose is involved in interactions with G q . Rhodopsin consists of the protein opsin and the covalently bound chromatophore retinal; the amino acid residues in contact with retinal in squid rhodopsin differ from those in bovine rhodopsin, and retinal assumes a less distorted configuration in the former. Intriguingly, the arrangement of chromatophores in crystallized squid rhodopsin may provide insight into the ability of invertebrates to detect the polarization plane of light. M. Murakami, T. Kouyama, Crystal structure of squid rhodopsin. Nature 453 , 363-367 (2008). [PubMed] G. F. X. Schertler, The rhodopsin story continued. Nature 453 , 292-293 (2008). [PubMed]

Molecular evidence for synonymy of the genera Moroteuthis and Onykia and identification of their paralarvae from northern Hawaiian waters

It has been claimed that most squid species in the genus Onykia may be immature stages of species in the genus Moroteuthis. To evaluate the generic status of Moroteuthis and Onykia and to identify paralarvae collected in northern Hawaiian waters, we performed morphological investigation and nucleotide sequence analysis of the mitochondrial cytochrome oxidase I (COI) gene. Of 42 Onykia paralarvae (1.8–8.5 mm dorsal mantle length, DML) examined, 41 had a nucleotide sequence identical to that of M. robusta and one (designated Onykia sp. A) could not be assigned to any known Moroteuthis species. Nucleotide sequence diversity estimates based on Kimura's two-parameter distances between Onykia sp. A and Moroteuthis spp. (0.109–0.150) fell well within the range of congeneric species, suggesting that Onykia sp. A is a member of the genus Moroteuthis. Molecular data supported the conclusion that the genus Moroteuthis is a junior synonym of the genus Onykia. Morphological investigation revealed that paralarvae of O. robusta (= M. robusta) <4.0 mm DML were distinct from other Onykia paralarvae in the chromatophore pattern on the mantle. The key characters for distinguishing O. robusta paralarvae from Onykia sp. A were the number and arrangement of chromatophores on the funnel.

The Role of Chromatophore Arrangement in Protecting the Chromatophores of the Brown Alga Dictyota dichotoma against Photodamage

Summary In the brown alga Dictyota dichotoma , the chromatophores, because of their brown colour also called phaeoplasts, occupy different positions in the cells depending on the fluence rate, the so called low and high intensity arrangement. Chromatophore displacement from the low to the high intensity arrangement decreases light absorption of the thallus. These changes are essentially restricted to the visible range of radiation due to absorption by the photosynthetic pigments. In the UV-B around 300 nm almost no absorption changes were observed. To find out whether chromatophore displacement can serve as a protection against photodamage, thalli with phaeoplasts being either in the low or the high intensity arrangement were irradiated with high fluences of visible light and UV-B, respectively. The experiments show that destruction of the pigments by visible light is considerably higher when the phaeoplasts are in the low intensity arrangement. On the contrary, the extent of photodamage caused by UV-B irradiation does not show significant correlation to chromatophore arrangement. This is plausible as the absorption of UV-B is not significantly influenced by changes in chromatophore arrangement. The question whether chromatophore displacement in Dictyota has a function in regulation of photosynthesis, in facilitating CO 2 -supply to phaeoplasts or decreasing the extent of photoinhibition is discussed.

Bregmaceros neonectabanus, a new species of the family Bregmacerotidae, Gadiformes

Close examinations of 3 forms ofBregmaceros nectabanus Whitley showed that the Southeast Atlantic and Indo-Malayan form and the Fiji Islands form are clearly distinct from the trueB. nectabanus (Toyama Bay form) in principal caudal fin ray (14 vs. 13) and in appearance of the abdomen (pigmented vs. not pigmented). The SE Atlantic and Indo-Malayan form is described as a new species,B. neonectabanus. The Fiji Is. form, differing from the new species only in the arrangement of chromatophores, is left for further study. The new species was collected from Japanese waters.

Do correlations exist between chromatophore arrangement and photosynthetic activity in seaweeds? : Nultsch, W., J. Pfau and U. Rüffer, 1981. Mar. Biol., 62(2/3): 111–117

Do correlations exist between chromatophore arrangement and photosynthetic activity in seaweeds? : Nultsch, W., J. Pfau and U. Rüffer, 1981. Mar. Biol., 62(2/3): 111–117

Do correlations exist between chromatophore arrangement and photosynthetic activity in seaweeds?

In Dictyota dichotoma, as in many other plants, the chromatophores which at low intensities occupy the cell walls perpendicular to the light beam move to the side walls parallel to the light beam if exposed to high light intensities. The aim of this investigation was to find out whether or not the changes from low- to high-intensity arrangement and vice versa function as an active control mechanism to regulate photosynthetic activity in D. dichotoma under the respective light condition. Four different experimental approaches were made: (a) In white and blue light experiments the changes of the transmittance and of the rate of photosynthetic oxygen production in high- and low-intensity arrangement were compared. (b) The kinetics of the depression and recovery of the PS-rates, as well as of the transmittance changes, were determined during high- and low-intensity movement, respectively. (c) Transmittance and PS-rates of thalli under illumination with polarized and unpolarized light of the same intensity (1,000 1x) were compared. (d) PS-rates of thalli after darkening as well as after preirradiation with weak and strong red light, conditions under which the chromatophores occupy the same position in the cells, were measured. In all these experiments the photosynthetic activity was strongly influenced by pre-illumination, but was independent of the respective chromatophore arrangement. This finding was confirmed by experiments with two other algae: (1) In the brown alga Alaria esculenta which does not display light-induced chromatophore displacements and concomitant transmittance changes, pre-irradiation with high light intensities decreases the PS-rates. (2) In the green alga Ulva lactuca, which shows circadian chloroplast movements, the PS-rates depend on the pre-irradiation only, irrespective of the chloroplast position. Thus we may conclude that in these organisms the function of chromatophore displacements is not the regulation of photosynthetic activity. Other ecological functions are discussed.

THE LARVAL DEVELOPMENT OFPINNIXA LONGIPES(LOCKINGTON, 1877) (BRACHYURA : PINNOTHERIDAE), REARED IN THE LABORATORY

Larvae of Pinnixa longipes, a commensal with the polychaete Axiothella rubrocincta. were reared to the megalopa stage in the laboratory. The zoeae were cultured at 34‰, 20°C, fed a combination of Dunaliella tertiolecta and Phaeodactylum tricornutum daily, and provided with a photoperiod of 12 h each of light and dark. The five zoeal and one megalopal stages are described and figured in detail, including the arrangement of chromatophores and various types of setae. Zoeae of P. longipes can be distinguished from other Pinnotherid zoeae, for which descriptions are available, on the basis of morphological characteristics.

The dermal chromatophores of Anolis carolinensis (Reptilia, Iguanidae).

AbstractSkin of the back, belly, dewlap and parietal eye were studied as illustrations of the principal variations of chromatophore arrangement and color range present in Anolis carolinensis. The fine structure of the chromatophores, disposed in sharply stratified layers, was investigated. The most superficial chromatophore layer consists of xanthophores, which impart a greenish‐yellow color to the skin. These cells are filled with two types of membrane‐bounded inclusions containing pteridines and carotenoids, respectively. Basal to the xanthophores is a 2–4 cell‐deep layer of iridophores. These cells are filled with undulating layers of birefringent rodlets, presumably guanine, arranged parallel to the skin surface. The most basal chromatophores are large melanophores, positioned above a thick collagenous basement lamella. Migration of melanin granules into the dendritic processes, which terminate at the dermoepidermal junction, cause the lizard to change from green to brown. The back skin, which ranges in color from bright green to brown, contains the full complement of dermal chromatophores. The xanthophore region is much reduced in the cream‐colored belly. The dewlap, which is bright red when extended, bears a thick layer of iridophores through which are scattered melanophores, and erythrophores containing red pigment. The dermis over the parietal eye contains only xanthophores and a basement lamella.