Takahiko Hariyama

Polarized iridescence of the multilayered elytra of the Japanese jewel beetle, Chrysochroa fulgidissima

The elytra of the Japanese jewel beetle Chrysochroa fulgidissima are metallic green with purple stripes. Scanning electron microscopy and atomic force microscopy demonstrated that the elytral surface is approximately flat. The accordingly specular green and purple areas have, with normal illumination, 100–150 nm broad reflectance bands, peaking at about 530 and 700 nm. The bands shift progressively towards shorter wavelengths with increasing oblique illumination, and the reflection then becomes highly polarized. Transmission electron microscopy revealed that the epicuticle of the green and purple areas consists of stacks of 16 and 12 layers, respectively. Assuming gradient refractive index values of the layers between 1.6 and 1.7 and applying the classical multilayer theory allowed modelling of the measured polarization- and angle-dependent reflectance spectra. The extreme polarized iridescence exhibited by the elytra of the jewel beetle may have a function in intraspecific recognition.

A comparison of electrophysiologically determined spectral responses in 35 species of Lepidoptera

Abstract Spectral responses from the compound eyes of 35 lepidopteran species representing 14 families were investigated electrophysiologically using ERG recordings. The light-stimuli used overed the range of 383–700 nm wavelengths. All species show three or four maxima in their spectral sensitivity curves. Two of these peaks were usually associated with ultraviolet and blue light (383 and 460 nm, respectively). The other maxima occurred in the 500–620 nm region. In Nymphalidae the highest peak was found in response to 560–580 nm stimuli. Of all wavelengths tested, these are the longest wavelengths to produce principal peak sensitivities. Pieridae and Lycaenidae have maxima in the UV region which represent significantly higher sensitivities than the secondary peaks to stimuli of longer wavelengths. Satyridae, Danaidae, Hesperiidae and diurnal moths except Epicopeia (Epicopeidae) generally have similar sensitivity curves with principal peaks between 500 and 520 nm. In Papilionid species except Graphium (max = 560 nm) high maxima occur in the UV and blue (460 nm) region. Noctural Sphingid moths possess the highest peak sensitivity at 540 nm. All other noctural moths tested have three or four maxima.

Sexual dichromatism of the damselfly Calopteryx japonica caused by a melanin-chitin multilayer in the male wing veins.

Mature male Calopteryx japonica damselflies have dark-blue wings, due to darkly coloured wing membranes and blue reflecting veins. The membranes contain a high melanin concentration and the veins have a multilayer of melanin and chitin. Female and immature C. japonica damselflies have brown wings. We have determined the refractive index of melanin by comparing the differently pigmented wing membranes and applying Jamin-Lebedeff interference microscopy. Together with the previously measured refractive index of chitin the blue, structural colour of the male wing veins could be quantitatively explained by an optical multilayer model. The obtained melanin refractive index data will be useful in optical studies on melanized tissues, especially where melanin is concentrated in layers, thus causing iridescence.

The origin of extensive colour polymorphism in Plateumaris sericea (Chrysomelidae, Coleoptera).

Abstract. Evidence is presented to demonstrate that colour polymorphism in a beetle arises from structural colours produced by a five-layered reflector in the elytron. The colour of leaf beetles, Plateumaris sericea, ranges across the visible spectrum from blackish-blue to red. The elytra have two distinct layers: epicuticle and exocuticle. Morphological observations reveal that the multilayer structure within the exocuticle differs little among the different colour morphs but the layers within the epicuticle have characteristic thicknesses corresponding to the observed colour. The reflectors, consisting of five layers within the epicuticle, are responsible for all the different colours observed in P. sericea, as shown by theoretical analyses for a multilayer stack, and by showing that removal of the elytral surface, including epicuticle, results in the disappearance of the iridescent colour.

Interaction of GTP‐binding protein Gq with photoactivated rhodopsin in the photoreceptor membranes of crayfish

Interaction of G‐protein with photoactivated rhodopsin (Rh∗) in crayfish photoreceptor membranes was investigated by immunoprecipitation using an antibody against rhodopsin. Two kinds of protein were co‐precipitated with rhodopsin. One is an α subunit of class‐q G‐protein (42 kDa, CGqα) which showed light‐induced, dose‐dependent binding to rhodopsin, and the other is an actin‐like protein (44 kDa) with light‐independent binding. Most of the CGqα was available for binding to Rh∗ but was dissociated from Rh∗ in the presence of GTPγS. These findings demonstrate that, in the crayfish photoreceptor, a Gq class of G‐protein is activated by Rh∗.

Primary structure of crayfish visual pigment deduced from cDNA

The primary structure of opsin of the crayfish Procambarus clarkii has been deduced from the cDNA sequence. The opsin is composed of 376 amino acid residues including all the conservative residues characteristic of other members of the rhodopsin family. Comparison of sequences of all known opsins reveals that the major Drosophila rhodopsin is more similar to the crayfish rhodopsin than to the Drosophila UV‐sensitive pigments. The phylogenetic trees of invertebrate opsins are constructed.

A thin polymer membrane, nano-suit, enhancing survival across the continuum between air and high vacuum

Most multicellular organisms can only survive under atmospheric pressure. The reduced pressure of a high vacuum usually leads to rapid dehydration and death. Here we show that a simple surface modification can render multicellular organisms strongly tolerant to high vacuum. Animals that collapsed under high vacuum continued to move following exposure of their natural extracellular surface layer (or that of an artificial coat-like polysorbitan monolaurate) to an electron beam or plasma ionization (i.e., conditions known to enhance polymer formation). Transmission electron microscopic observations revealed the existence of a thin polymerized extra layer on the surface of the animal. The layer acts as a flexible “nano-suit” barrier to the passage of gases and liquids and thus protects the organism. Furthermore, the biocompatible molecule, the component of the nano-suit, was fabricated into a “biomimetic” free-standing membrane. This concept will allow biology-related fields especially to use these membranes for several applications.

Presence of Rhodopsin and Porphyropsin in the Eyes of 164 Fishes, Representing Marine, Diadromous, Coastal and Freshwater Species—A Qualitative and Comparative Study

There are two types of visual pigments in fish eyes; most marine fishes have rhodopsin, while most freshwater fishes have porphyropsin. The biochemical basis for this dichotomy is the nature of the chromophores, retinal (A1) and 3‐dehydroretinal (A2), each of which is bound by an opsin. In order to study the regional distribution of these visual pigments, we performed a new survey of the visual pigment chromophores in the eyes of many species of fish. Fish eyes from 164 species were used to examine their chromophores by high‐performance liquid chromatography—44 species of freshwater fish, 20 of peripheral freshwater fish (coastal species), 10 of diadromous fish and 90 of seawater fish (marine species) were studied. The eyes of freshwater fish, limb freshwater fish and diadromous fish had both A1 and A2 chromophores, whereas those of marine fish possessed only A1 chromophores. Our results are similar to those of previous studies; however, we made a new finding that fish which live in freshwater possessed A1 if living near the sea and A2 if living far from the sea if they possessed only one type of chromophore.

Light-modulated subcellular localization of the alpha-subunit of GTP-binding protein Gq in crayfish photoreceptors.

Gq-type GTP-binding protein (Gq) plays an important role in invertebrate visual phototransduction. The subcellular localization of the alpha subunit of visual Gq in crayfish photoreceptor was investigated immunocytochemically and biochemically to demonstrate the details of the rhodopsin-Gq interaction. The localization of Gq(alpha) changed depending on the light condition. In the dark, Gq(alpha) was localized in the whole rhabdoms as the membrane-bound form. In the light, half of the Gq(alpha) was localized in the cytoplasm as the soluble form. The translocation of Gq(alpha) was reversible. The light-modulated translocation possibly controls the amount of Gq that can be activated by rhodopsin. In vitro hydroxylamine treatment of rhabdomeric membranes suggested that the translocation was regulated by the fatty-acid modification of Gq(alpha).

The visual pigment chromophores in the retina of insect compound eyes, with special reference to the Coleoptera

Abstract A new survey, by HPLC, of the visual pigment chromophores in the compound eye of Japanese insects was made during the Summer and Autumn of 1988. The results largely conformed to those of previous studies (in Europe, Japan and the U.S.A.), except for the discovery of several coleopterans unusual in containing both retinal (A 1 ) and 3-hydroxyretinal (A 3 ). The chromophores of five coleopteran families are described for the first time: the Gyrinidae, Hydrophilidae and Lampyridae contain both A 1 and A 3 : while in the Lucanidae and Melandryidae only A 1 was detected. Of the Family Cerambycidae (the only insect family so far discovered to contain members with different chromophore types), one of the two major subfamilies not previously investigated, the Lepturinae, yielded only A 1 . Newly-tested species from the Prioninae conformed to earlier findings (A 1 only). Additional data (Vogt, previously unpublished) suggest that the Cantharidae, Cicindelidae, Dermestidae and Tenebrionidae also utilize only A 1 . The distribution of A 1 and A 3 among the insects is discussed in terms of phylogeny, diet, and the photic environment. The coleopterans utilizing both A 1 and A 3 are widely separated, phylogenetically, but most are carnivorous and associated with an aquatic environment. The co-incidence of these features also in the Odonata, which generally utilize both A 1 and A 3 , suggests that chromophore content in both groups may well be environmentally related. These findings are compared with the seasonal and environment-related occurrence of A 1 and A 2 (3-dehydroretinal) reported for fishes, amphibians and crustaceans. The data now accumulated for compound eye chromophore content of the Insecta are listed. Included are first mentions of the Dermaptera (the earwig Anisolabis maritima ) and Megaloptera ( Sialis lutaria ), which contain only A 1 . Exceptions to the previously apparent, general phylogenetic trends are now known in the Orders Coleoptera, Diptera, Neuroptera and Odonata.