V. Benno Meyer-Rochow

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.

Differences in ultraviolet wing patterns in the New Zealand lycaenid butterflies Lycaena salustius, L. rauparaha, and L. feredayi as a likely isolating mechanism

Abstract The dorsal and ventral surfaces of fore- and hind wings in Lycaena salustius, L. rauparaha, and L. feredayi were examined under visible and ultraviolet (UV) light. Differences between the males and females of all three species, invisible to the human eye, appear under UV-radiation. Males of L. salustius exhibit extensive UV-reflecting regions on the dorsal sides of both wing pairs. On female L. salustius, these UV-reflecting areas are reduced to tiny submarginal spots. Males and females of both L. rauparaha and L. feredayi are UV-absorbing. Scales examined under the scanning electron microscope confirmed the correlation between scale-ultrastructure and UV-reflectance or absorbance known from other butterflies. The geographical distribution of the sexually UV-dichromatic L. salustius and either the UV-absorbing L. rauparaha or L. feredayi (rarely both) overlap, and the latter two are not found together on their own. Therefore I suggest that the UV-pattern is an isolating mechanism, similar to the ...

The eyes of mesopelagic crustaceans

SummaryThe compound eyes of the mesopelagic euphausiid Thysanopoda tricuspidata were investigated by light-, scanning-, and transmission electron microscopy. The eyes are spherical and have a diameter that corresponds to 1/6 of the carapace length. The hexagonal facets have strongly curved outer surfaces. Although there are four crystalline cone cells, only two participate in the formation of the cone, which is 90–120 μm long and appears to have a radial gradient of refractive index. The clear zone, separating dioptric structures and retinula, is only 90–120 μm wide. In it lie the very large oval nuclei of the seven retinula cells. Directly in front of the 70 μm long and 15 μm thick rhabdom a lens-like structure of 12 μm diameter is developed. This structure, known in only a very few arthropods, seems to be present in all species of Euphausiacea studied to date. It is believed that the rhabdom lens improves near-field vision and absolute light sensitivity. Rod-shaped pigment grains and mitochondria of the tubular type are found in the plasma of retinula cells. The position of the proximal screening pigment as well as the microvillar organization in the rhadbdom are indicative of light-adapted material. The orthogonal alignment of rhabdovilli suggests polarization sensitivity. Behind each rhabdom there is a cup-shaped homogeneous structure of unknown, but possibly optical function. Finally, the structure and the function of the euphysiid eye are reviewed and the functional implications of individual components are discussed.

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.

Fatty acid analysis of lens and retina of two antarctic fish and of the head and body of the antarctic amphipod Orchomene plebs

Abstract 1. 1. Total phospholipid and triglyceride contents in lens and retina of Trematomus borchgrevinki and T. bernacchii (Pisces) as well as in head and body of Orchomene plebs (Amphipoda) were determined. The highest triglyceride total was found in the heads of the Antarctic amphipod. 2. 2. The fatty acid composition of phospholipid as well as triglyceride fractions was analysed for all three species by gas chromatography. 3. 3. Large amounts of polyunsaturated long chain fatty acids were found in all species, and it is believed that the sub-zero temperatures of the Antarctic marine habitat are the cause for the abundance of these acids. 4. 4. The “eye lipids” in the two fishes probably do not possess a tapetal function, but are thought to be components of the visual membranes.

Ultrastructure of the neural component of the regenerating spinal cord in the tails of three species of New Zealand lizards (Leiolopisma nigriplantare maccanni, Lampropholis delicata, and Hoplodactylus maculatum)

Abstract The regenerated spinal cords of all three species examined (Leiolopisma nigriplantare maccanni, Lampropholis delicata, Hoplodactylus maculatum) consisted of a monolayer of ependymal cells with interspersed axons and cellular processes lining the liquor-filled canalis centralis with its Reissner fibre in the centre. Cerebral spinal fluid contacting neurons (CSFCNs) were distinguishable from ependymal cells by their luminal projections, longer and thicker stereocilia (with well-developed cytoskeletal elements), overall greater electron translucency, and specific organelles like silver methenamine-positive dense granules. Silver methenamine-positive material was present also in the lumen. Vesicles, apparently rupturing, were noticed on the luminal face of the CSFCN. A secretory activity of the CSFCN is one likely function of vesicles. The similarity between CSFCNs and inner ear hair cells (as well as lateral line receptor cells) suggested another possible function, namely that of monitoring cerebros...

Thoughts on the possible function and origin of bioluminescence in the New Zealand glowworm Arachnocampa luminosa (Diptera: Keroplatidae), based on electrophysiological recordings of spectral responses from the eyes of male adults

It was established by means of the electroretinogramme method that eyes of male Arachnocampa luminosa respond to the presentation of monochromatic isophotonic light flashes with three response peaks. The eyes are maximally sensitive to light of 540 nm wavelength (green); a distinct second response peak exists to light of 460 nm wavelength (bluegreen); a third response peak exists in the near-ultraviolet. Light of a wavelength longer than 660 nm does not elicit measurable responses. The results are discussed in relation to eye anatomy and physiology as well as glowworm ecology and behaviour. It is concluded that the bluegreen light emitted by glowworm larvae is aimed at small aquatic prey, but that in the adult the light, “inherited” from the larval stage, obtained a new purpose — that of in-traspecific communication.

Structure and possible function of the unusual compound eye of Sericesthis geminata (Coleoptera: Scarabaeidae)

Sericesthis geminata (Boisduval) is a nocturnal, eucalypt‐defoliating scarabaeid beetle. Its eye, like that of many other nocturnal arthropods, is of the ‘clear‐zone’ type, in which dioptric apparatus and receptor layer are separated by a region devoid of pigment. The eye is unusual, however, in possessing a tiered retinula, consisting of a distal rhabdomere, a proximal rhabdom, and a small basal rhabdomere. The distal rhabdomere, located directly above the proximal rhabdom, belongs to a single retinula cell whose microvilli are arranged in a complicated pattern and in 3 main directions. The diameter of the distal rhabdomere is extremely large, and its microvilli are approximately twice as thick as those of the proximal rhabdom, which measure 70–75 nm. The proximal rhabdom comprises 6 fused, V‐shaped rhabdomeres, and resembles that of the firefly. Cell migrations in response to dark/light adaptation were not observed. The presence of a large, distal rhabdomere, the unique tri‐ or polydirectional arrangeme...

The eyes of mesopelagic crustaceans: I. Gennadas sp. (Penaeidae)

SummaryThe eye of the deep-sea penaeid shrimp Gennadas consists of approximately 700 square ommatidia with a side length of 15 μn. It is hemispherical in shape and is located at the end of a 1.5 mm long eye stalk. The cornea is extremely thin, but the crystalline cone is well-developed. A clear zone between dioptric structures and the rhabdom layer is absent. A few pigment granules are found within the basement membrane; otherwise they, too, are absent from the eye of Gennadas. The rhabdom is massive and occupies 50 % of the eye. It consists of orthogonally oriented microvilli (the latter measuring 0.07 μm in diameter) and is 75 μm long. In cross sections adjacent rhabdoms, all approximately 8 μm in diameter, form an almost continuous sheet and leave little space for retinula cell cytoplasm. In spite of a one h exposure to light, rhabdom microvilli show no disintegration or disruption of membranes. Vesicles of various kinds, however, are present in all seven retinula cells near the basement membrane. Bundles of seven axons penetrate the basement membrane. On their way to the lamina they often combine and form larger aggregations.ZusammenfassungDas aus ca. 700 Ommatidien zusammengesetzte, halbkugelförmige Auge der Tiefseegarnele Gennadas sp. sitzt am Ende eines etwa 1,2 mm langen Stiels. Die Cornea ist zwar außerordentlich dünn, doch der Kristallkegel ist gut entwickelt. Es fehlt eine klare pigmentfreie Zone zwischen dioptrischem Apparat und Rhabdom. Vereinzelte Pigmentkörner werden lediglich innerhalb der Basallamina angetroffen. Das Rhabdom ist massiv und nimmt rund 50 % des Augenvolumens ein. Es besteht aus rechtwinklig angeordneten Mikrovilli, die einen Durchmesser von 72 nm aufweisen. Querschnitte zeigen die dichte Packung der Rhabdome. Interrhabdomale Lüken für Retinula-Zellplasma sind kaum vorhanden. Nach einer einstündigen Helladaptation wurden keine Feinstrukturveränderungen an den Mikrovilli beobachtet. In allen Retinulazellen traten jedoch in der Nähe der Basallamina Vesikel verschiedenster Art auf. Die sieben Axone eines Ommatidiums verlassen das Auge als gemeinsames Bündel, doch unterhalb der Basallamina vereinigen sich oft mehrere Bündel zu größeren Einheiten.

Electrophysiological studies on the insect compound eye

Using electrophysiological studies of the insect compound eye as an example, this paper describes how to set-up the experimental equipment, how to prepare and use recording electrodes, how to make a preparation, and how to locate the electrode in the tissue after the recording. The basic anatomy of the compound eye is explained and functional parameters such as absolute sensitivity versus activity, colour and polarisation sensitivity, flicker fusion frequency, and information transfer are mentioned.