Eisuke Eguchi

Pentachromatic visual system in a butterfly

and mammals. The two segregated frequency ranges of best localization performance in the pigeon (250-500Hz and 2-4kHz) could reflect the operational ranges of two distinct binaural mechanisms as proposed by the classic duplex theory of directional hearing [15]: the perception of interaural time (phase) differences at low frequencies and of interaural intensity disparities at high frequencies. The transitional zone between these mechanisms could correspond to the range of poor localization capabilities at 1-2 kHz determined by both, the physiological high-frequency limit for phase locking in the auditory nervous system [16] and the physical low-frequency limit for interaural level differences due to the acoustic shadow of the head. Although this interpretation offers an explanation for the frequency dependence of auditory localization, it cannot, however, be completely excluded that the pigeon may use a pressure gradient system as suggested for the Japanese quail [17]. To solve this problem, measurements of the interaural intensity and phase difference thresholds are required. These behavioral experiments using heart-rate conditioning are in progress. First results are consistent with the hypothesis of combined binaural phase and intensity difference perception in sound localization.

Freeze-etch and histochemical evidence for cycling in crayfish photoreceptor membranes

SummaryFreeze-etched rhabdoms and adjacent cytoplasmic organelles from crayfish compound eyes have been studied for evidence of photoreceptor membrane cycling. The protoplasmic leaflet face (PF) of split photoreceptor membrane of the microvilli is richly particulate. The particles (92±16 A in diameter in surface fractures; 70±9 A in cross fractures; density about 8000/μm2) probably indicate rhodopsin molecule localization. Closely similar particles appear in membranes of pinocytotic vesicles, multivesicular bodies (MVB) and secondary lysosomes. In contrast other retinular cell membranes like plasma membrane remote from the rhabdom are quite distinct (60±23 A particle diameter, density ca 1000/μm2). Histochemical tests for acid phosphatase demonstrate its presence in well-developed (but not early stage) MVBs, mixed lamellar vesicular bodies (LVB) and lamellar bodies. Density of PF particles decreases from 8000 in MVB to roughly 4500/μm2 in LVB indicating a degradative sequence from rhabdom to lamellar bodies. Membrane leaflet orientations show that primary endocytosis from microvilli must be followed by secondary endocytosis of fused coated vesicles to form MVB. Morphological evidence for photoreceptor membrane resynthesis has not been found yet in crayfish but some has been obtained in other crustaceans.

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.

3-Dehydroretinal (vitamin A2 aldehyde) in crayfish eye

11-Cis-3-dehydroretinal was found in the eye of crayfish, Procambarus clarkii. The 11-cis-3-dehydroretinal was isomerized to all-trans isomer by light-illumination, as was also 11-cis-retinal. Irradiation with deep-red light (lambda greater than 680 nm) selectively isomerized the 11-cis-3-dehydroretinal. The 3-dehydroretinal was not extracted with petroleum ether from the tissue after freeze-drying. These facts suggest that the 11-cis-3-dehydroretinal is the chromophore of crayfish visual pigment. The 3-dehydroretinal content varied with season, high level in winter and low in summer. The crayfish may have a vitamin A1-A2 visual pigment system similar to those of freshwater fishes and amphibians.

Localization of spectral receptors in the ommatidium of butterfly compound eye determined by polarization sensitivity

Summary1.A butterfly Papilio has 5 types of spectral receptors in the compound eye. The spectral sensitivity of each type peaks in the UV, violet, blue, green, and red wavelengths, respectively. The green type contains two subtypes with and without a UV secondary peak. Here we studied the localization of these spectral receptors within the ommatidium.2.An ommatidium contains 9 photoreceptors (R1–9), each of which is one of the 5 spectral receptor types. The photoreceptors bear parallel microvilli to form a nontwisted rhabdom, and thereby the photoreceptors are polarization sensitive.3.We first examined the microvillar orientation by electron microscopy. The microvilli of R1, 2, and 9 are oriented dorso-ventrally (0°), whereas those of R3 and 4 are parallel to the antero-posterior axis (90°). The R5–8 bear microvilli diagonally: 45° for R6 and R8, 135° for R5 and R7.4.We then recorded spectral and polarization sensitivities from single photoreceptors. The peak angle of the polarization sensitivity (θmax) of the UV, violet, and blue receptors were around 0°, whereas that of the green receptors was around 90°. In the double-peaked green receptors, the θmax at UV was also around 90°. The red receptors showed a θmax at around 35°. The polarization sensitivity ratio (PSmax/PSmin) of the double-peaked green receptors measured at UV was around 4, whereas the ratio of other receptors was around 2.5.We conclude that R1 and R2 are either UV, violet, or blue receptors whereas R3 and R4 are green receptors. Some R6 and R8 are red receptors. We also conclude that the UV secondary peak in the double-peaked green receptor is not simply attributable to the coupling with UV receptors.

Daily changes of structure, function and rhodopsin content in the compound eye of the crabHemigrapsus sanguineus

SummaryThe compound eye of the crabHemigrapsus sanguineus undergoes daily changes in morphology as determined by light and electron microscopy, both in the quantity of chromophore substances studied by HPLC and in visual sensitivity as shown by electrophysiological techniques.1.At a temperature of 20 °C, the rhabdom occupation ratio (ROR) of an ommatidial retinula was 11.6% (maximum) at midnight, 8.0 times larger than the minimum value at midday (1.4%) (Figs. 2, 6).2.Observations by freeze-fracture revealed that the densities of intra-membranous particles (9–11 nm in diameter) of rhabdomeric membrane were ca. 2000/μm2 and ca. 3000/μm2 for night and daytime compound eyes, respectively (Fig. 3).3.Screening pigment granules migrated longitudinally and aggregated at night, but dispersed during the day. Reflecting pigment granules migrate transversally in the proximal half of the retinula layer i.e. cytoplasmic extensions containing reflecting pigment granules squeeze between neighbouring retinula cells causing optical isolation (Fig. 4). Thus the screening pigment granules within the retinula cells show longitudinal migration and radial movement so that the daytime rhabdoms are closely surrounded by the pigment granules (Fig. 2).4.At 20 °C, the total amount of chromophore of the visual pigment (11-cis and all-trans-retinal) was 1.4 times larger at night than during the day i.e. 46.6 pmol/eye at midnight and 33.2 pmol/eye at midday (Fig. 9). Calculations of the total surface area of rhabdomeric membrane, total number of intra-membranous particles in rhabdomeric membrane and the total number of chromophore molecules in a compound eye, indicate that a considerable amount of chromophore-protein complex exists outside the rhabdom during the day.5.The change in rhabdom size and quantity of chromophore were highly dependent on temperature. At 10 °C both rhabdom size and amount of chromophore stayed close to daytime levels throughout the 24 hours (Figs. 6, 9).6.The intracellularly determined relative sensitivity of the dark adapted night eye to a point source of light was about twice as high as the darkadapted day eye (Fig. 10). Most of the increase in the sensitivity is attributed primarily to the effect of reflecting pigment migration around the basement membrane (Fig. 4) and, secondarily, to the changes in the amount and properties of the photoreceptive membrane. The results form the basis of a detailed discussion as to how an apposition eye can function possibly as a night-eye.

Orthogonal microvillus pattern in the eighth rhabdomere of the rock crab Grapsus.

SummaryThe eighth retinular cell (R 8) of Grapsus lacks cytoplasmic pigment granules and basically resembles those previously known in the ghost crab Ocypode and the mysid Praunus. Distally located, R 8 comprises four lobes inserted between the outer ends of the seven regular retinular cells (R 1–R 7). A thin cytoplasmic bridge connects these lobes. One lobe adjacent to R 1 contains the nucleus of R 8 and gives rise proximally to the cells axon. The short distal eighth rhabdomere consists of microvilli (mvl) protruding axially from all four lobes. Similar R 8s were found also in two other crab families and in two other genera of mysids.In Grapsus the eighth rhabdomere is extraordinary in possessing mvl oriented in two orthogonal directions parallel to the mvl of R 1–R 7. The distal 20% of the rhabdom consists of mvl originating exclusively from R 8. These appear in somewhat irregular bands and are alternately oriented parallel to the animals vertical or horizontal axis. More proximally the retinula contains eleven sectors but the rhabdom still comprises bands of alternating mvl with those from R 8 joined respectively by the rhabdomeres of R 1, 4, and 5 (horizontal) and R 2, 3, 6 and 7 (vertical). The rest of the rhabdom shows typical decapod organization with seven interdigitating rhabdomeres.

A comparative study of spectral sensitivity curves in three diurnal and eight nocturnal species of Japanese fireflies

Abstract The spectral properties of the eyes of 3 species of diurnal and 8 species of nocturnal Japanese fireflies, in many cases males and females, were determined by an electroretinographic method. With the exception of Hotaria parvula males, which had a λmax of 580 nm, almost all species studied possessed a maximum around 500–540 nm. The eyes of diurnal and nocturnal species did not differ significantly in their sensitivity maxima. As in North American species of fireflies (Lall, 1981a,b) congruency existed between visual sensitivity peaks and light emission maxima in Luciola cruciata, L. lateralis and Hotaria parvula. In agreement with Seliger et al. (1982a,b) we conclude that an adaptation of the visual sensitivity to the light produced need not have occurred and that evolutionary adaptation of light emission to an existing ancestral green-sensitivity of the eye is the more likely course of events.

Spectral Sensitivity of Single Photoreceptor Cells in the Eyes of the Ctenid Spider Cupiennius salei Keys

Abstract Intracellular recordings from photoreceptor cells of all eyes of the spider Cupiennius salei Keys reveal 3 groups of cells with spectral sensitivity maxima in the blue (480 nm). green (520 nm), and UV (340 nm), respectively. The blue and green cells show secondary peaks in the UV at 340-380 nm. In the posterior median, posterior lateral and anterior median eyes, the majority of photoreceptor cells are the blue and green cells in roughly equal numbers. In the anterior lateral eye, however, the green cells dominate. UV cells were only found in the secondary eyes and only once in each of them.

The effects of temperature and light on particles associated with crayfish visual membrane: a freeze-fracture analysis and electrophysiological study

SummaryDepending on the pre-experimental treatment, densities as well as sizes of particles associated with the visual membranes in the eyes ofProcambarus clarkii varied. The highest mean particle density (5268 ± 969 μm2) and the smallest mean particle diameter (5.57 ± 1.35 nm) were found in crayfish which had been kept in the dark for 10 weeks in aerated fresh water of 10 ° C. Crayfish kept under a 12 h dark/light regime in water of 10 ° C or 30 ° C for three weeks displayed particle densities of 1076 ± 180 and 2899 ± 249 μm−2, respectively; particle diameters were of the order of 8 nm.Temperature did not alter the shape or the slope of theV/logI curves, but ERG recordings show that maximum spectral sensitivity was shifted from λmax=560 nm in cold water crayfish (10 ° C) to λmax=580 nm in crayfish from the 30 ° C tank, and that the 10 ° C curve was somewhat narrower than the 30 ° C curve. It is suggested that the observed shift was caused by a combination of factors, of which the following may have played key roles: (1) The filter effect of screening pigment granules and other intracellular components such as vesicles, vacuoles, endoplasmic reticulum, and mitochondria, some of which were developed to a considerably greater extent in 30 ° C material; (2) increased membrane fluidity due to higher temperature as well as the presence of photoproducts in the light, and the ‘countermeasures’ taken by the visual pigment molecules to stabilize the lipid bilayer, e.g. higher density, possible 12-s-cis linkages etc.; and (3) increased regeneration or synthesis of rhodopsin due to higher metabolic activity of retinula cells at higher temperatures.Temperature-induced changes of visual pigments in a variety of organisms are discussed and evidence for the rhodopsin-aggregate model of crayfish visual pigment is presented. It is concluded that the retinula cytoplasm is involved in restoring depleted stocks of photopigment, and that the biological sense of possessing an increase in red sensitivity during the warm summer months lies in the correlation of light penetration in the natural habitat ofP. clarkii and optimal exploitation of the habitat.