Genetic basis of orange spot formation in the guppy (Poecilia reticulata)

Background To understand the evolutionary significance of female mate choice for colorful male ornamentation, the underlying regulatory mechanisms of such ornamentation must be understood for examining how the ornaments are associated with “male qualities” that increase the fitness or sexual attractiveness of offspring. In the guppy (Poecilia reticulata), an established model system for research on sexual selection, females prefer males possessing larger and more highly saturated orange spots as potential mates. Although previous studies have identified some chromosome regions and genes associated with orange spot formation, the regulation and involvement of these genetic elements in orange spot formation have not been elucidated. In this study, the expression patterns of genes specific to orange spots and certain color developmental stages were investigated using RNA-seq to reveal the genetic basis of orange spot formation. Results Comparing the gene expression levels of male guppy skin with orange spots (orange skin) with those without any color spots (dull skin) from the same individuals identified 1102 differentially expressed genes (DEGs), including 630 upregulated genes and 472 downregulated genes in the orange skin. Additionally, the gene expression levels of the whole trunk skin were compared among the three developmental stages and 2247 genes were identified as DEGs according to color development. These analyses indicated that secondary differentiation of xanthophores may affect orange spot formation. Conclusions The results suggested that orange spots might be formed by secondary differentiation, rather than de novo generation, of xanthophores, which is induced by Csf1 and thyroid hormone signaling pathways. Furthermore, we suggested candidate genes associated with the areas and saturation levels of orange spots, which are both believed to be important for female mate choice and independently regulated. This study provides insights into the genetic and cellular regulatory mechanisms underlying orange spot formation, which would help to elucidate how these processes are evolutionarily maintained as ornamental traits relevant to sexual selection.

Psilotris vantasselli, a new species of goby from the tropical western Atlantic (Teleostei: Gobiidae: Gobiosomatini: Nes subgroup)

A new species of goby is described from submersible and scuba collections off Bonaire and New Providence Island, Bahamas. A molecular phylogenetic analysis of mitochondrial and nuclear genes confirms the placement of the new species within the genus Psilotris of the Nes subgroup of the Gobiosomatini. The new species is easily distinguished from congeners and morphologically similar species of Varicus by its unique coloration, which includes eight narrow, bright yellow bars on the trunk, each with a small orange spot centered on the lateral midline. In addition, the combination of the absence of scales on the head and body and the presence of modified ctenoid scales on the base of the caudal fin, branched pelvic-fin rays, and 15–16 pectoral-fin rays further differentiates the new species from other species of Psilotris and Varicus.

A new subspecies of Corydalis mira (Batalin) c. Y. Wu et h. Chuang (Fumariaceae) from Jammu and Kashmir state (India)

The new subspecies Corydalis mira (Batalin) C. Y. Wu et H. Chuang subsp. fokarica Mikhailova collected in the Western Himalayas of India, near the Fokar monastery in Sergol settlement (state of Jammu and Kashmir) is described. The new subspecies differs from C. mira subsp. mira by dark orange spot on the upper outer petal (not solid colored yellow corolla), by seeds with an edge and glossy tuberculate surface (not seeds without edge and with an opaque reticulate surface).

Female mate preference explains countergradient variation in the sexual coloration of guppies ( Poecilia reticulata )

We tested the hypothesis that mate choice is responsible for countergradient variation in the sexual coloration of Trinidadian guppies ( Poecilia reticulata ). The nature of the countergradient pattern is that geographical variation in the carotenoid content of the orange spots of males is counterbalanced by genetic variation in drosopterin production, resulting in a relatively uniform pigment ratio. A female hue preference could produce this pattern, because hue is the axis of colour variation most directly affected by the pigment ratio. To test this hypothesis, we crossed two populations differing in drosopterin production and produced an F 2 generation with variable drosopterin levels. When the carotenoid content of the orange spots was held constant, female guppies preferred males with intermediate drosopterin levels. This shows that females do not simply prefer males with greater orange spot pigment content; instead, the ratio of the pigments also affects male attractiveness. To our knowledge, this is the first direct evidence for a hypothesized agent of countergradient sexual selection.

Carotenoid-based colour of acanthocephalan cystacanths plays no role in host manipulation

Manipulation by parasites is a catchy concept that has been applied to a large range of phenotypic alterations brought about by parasites in their hosts. It has, for instance, been suggested that the carotenoid-based colour of acanthocephalan cystacanths is adaptive through increasing the conspicuousness of infected intermediate hosts and, hence, their vulnerability to appropriate final hosts such as fish predators. We revisited the evidence in favour of adaptive coloration of acanthocephalan parasites in relation to increased trophic transmission using the crustacean amphipod Gammarus pulex and two species of acanthocephalans, Pomphorhynchus laevis and Polymorphus minutus . Both species show carotenoid-based colorations, but rely, respectively, on freshwater fish and aquatic bird species as final hosts. In addition, the two parasites differ in the type of behavioural alteration brought to their common intermediate host. Pomphorhynchus laevis reverses negative phototaxis in G. pulex , whereas P. minutus reverses positive geotaxis. In aquaria, trout showed selective predation for P. laevis -infected gammarids, whereas P. minutus -infected ones did not differ from uninfected controls in their vulnerability to predation. We tested for an effect of parasite coloration on increased trophic transmission by painting a yellow–orange spot on the cuticle of uninfected gammarids and by masking the yellow–orange spot of infected individuals with inconspicuous brown paint. To enhance realism, match of colour between painted mimics and true parasite was carefully checked using a spectrometer. We found no evidence for a role of parasite coloration in the increased vulnerability of gammarids to predation by trout. Painted mimics did not differ from control uninfected gammarids in their vulnerability to predation by trout. In addition, covering the place through which the parasite was visible did not reduce the vulnerability of infected gammarids to predation by trout. We discuss alternative evolutionary explanations for the origin and maintenance of carotenoid-based colorations in acanthocephalan parasites.

Study of the Influence Hormone LHRH-a and 17a-MT of Hemocytology on Orange Spot Grouper Broodstock, Epinephelus coioides

<p>An experiment to study the influence of the chronic hormone LHRH-a and 17a-MT on haematology orange spot grouper, Epinephelus coioides broodstock was conducted at Gondol Research Institute for Mariculture, Bali. Fish weights were ranged 4.7-10.4 kg (female) and 10.4-17.8 kg (male). The females broodstock was treated by hormone 17a-MT with dosage 50 mg/kg body weight, and males was by hormone LHRH-a with dosage 50 and 100 mg/kg body weight. Fish were kept on two concrete tank contained 100 m³ sea water and 2 meters depth and density 15 fishes/tank, male ratio and female was 1 : 2. Hormone treatment was peformed every two months until six months culture. Blood were collected before treatment by hormone and every two months. Hemocytology parameters measured were hematocrit, hemoglobin, total erythrocyte, and total leucocyte. Result of the average indicator of hemacytology to influence on haemological parameters.</p> <p>Keywords: Epinephelus coioides, chronic hormone, hemocytology, orange spot grouper broodstock.</p> <p> </p> <h2>ABSTRAK</h2> <p>Suatu percobaan dengan tujuan untuk mengetahui pengaruh hormon LHRH-a dan 17a-MT terhadap keragaan hemositologi induk ikan kerapu lumpur, <em>Epinephelus coioides</em> telah dilakukan di Balai Besar Riset Perikanan Budidaya Laut Gondol, Bali. Ikan uji yang digunakan adalah induk ikan kerapu lumpur kelamin betina dengan bobot antara 4,7-10,4 kg dan induk kelamin jantan dengan bobot antara 10,4-17,8 kg. Ikan uji dipelihara dalam bak beton volume 100 m³ dengan kepadatan 15 ekor/bak, dilengkapi aerasi dan pergantian air sistim mengalir. Induk kelamin betina diberikan perlakuan implantasi pelet hormon LHRH-a dosis 50 mg/kg bobot, dan induk kelamin jantan dengan hormon 17a-MT dosis 50 dan 100 mg/kg bobot ikan. Implantasi dilakukan setiap 2 bulan, pada awal percobaan (sebelum perlakuan hormon/bulan ke-0), bulan ke-2, bulan ke-4, dan bulan ke-6 dilakukan sampling darah untuk pengujian keragaan hemositologi, meliputi; persentase hematokrit, kadar nilai hemoglobin, jumlah total eritrosit, dan jumlah total leukosit. Hasil percobaan menunjukkan bahwa penggunaan hormon LHRH-a pada induk ikan kerapu lumpur kelamin betina dan hormon 17a-MT pada induk ikan kerapu lumpur kelamin jantan berpengaruh terhadap keragaan hemositologi.</p> <p>Kata kunci: <em>Epinephelus coioides, </em> hemositologi, hormon kronik, induk ikan kerapu lumpur</p>