Anterior Lateral Eyes Research Articles

The Ocular Anomaly in a Ground Spider(Araneae: Gnaphosidae) from Japan.

The ocular anomaly in a Japanese ground spider is reported. The spider is identified with Gnaphosa primorica OVTSHARENKO, PLATNICK et SONG, 1992, described from the Russian Far East. It is recorded for the first time in Japan. The anomalous individual has only two eyes; these are regarded as the right anterior lateral and posterior lateral eyes.

Efferent Control in the Anterior Lateral Eyes of Orb Weaving Spiders

Abstract The anterior lateral (AL) eyes of the orb weaving spiders, Argiope amoena and A. bruennichii, have a single type of receptor cell with a maximum sensitivity at about 520–540 nm. Efferent optic nerve signals control the photoreceptor response in the AL eyes. Specifically, efferent signals decrease the threshold for light responses and change the waveform of responses. Similar changes in the threshold and waveform could be produced by exogenous application of octopamine, suggesting that it is an efferent neurotransmitter.

Changes in visual fields associated with web reduction in the spider family uloboridae.

When visual fields of the primitive orb-weaver, Waitkera waitkerensis, are reconstructed using measurements taken from intact lenses and cross and longitudinal sections of the prosoma, they show that this species has complete visual surveillance, but that none of the visual fields of its eight eyes overlap. The more advanced orb-weaver, Uloborus glomosus, also has eight eyes, but each eye has a greater visual angle, giving this species a complex pattern of overlapping visual fields. Uloborids that spin reduced webs are characterized by reduction or loss of the four anterior eyes and other carapace modifications necessary for them to effectively monitor and manipulate their reduced webs. The eyes of these uloborids have greater visual angles than those of orb-weavers, resulting primarily from perimetric expansion of their retinal hemispheres. Additionally, the axes of their visual fields are more ventrally directed due to greater dorsal than ventral retinal expansion and to ventral redirection of the entire eye. Consequently, even though the anterior lateral eyes of the triangle-weaver Hyptiotes cavatus lack retinae, the species' six functional eyes permit complete visual surveillance and exhibit visual overlap. The single-line-weaver, Miagrammopes animotus, has lost its four anterior eyes, and with them much of the anterior vision and all of the visual overlap found in the other species. However, changes similar to those of H. cavatus permit this species to retain most if its dorsal and ventral visual surveillance. Thus, ocular changes act in consort to maintain relatively complete visual surveillance in the face of eye loss and other major carapace modifications necessary for the operation of reduced webs.

The retinae of Ewyattus bleekeri, an aberrant salticid spider from Queensland

The retinal ultrastructure of an aberrant salticid spider, Euryattus bleekeri (Doleschall, 1859) is described, and discussed in the context of a model of the evolution of the Salticidae previously proposed by Jackson & Blest (1982a). The evolutionary model suggested that the Salticidae are derived from web‐building ancestors that acquired the strategy of invading the webs of other species and families of spiders; it predicts that the evolution of the principal eyes preceded that of the accessory eyes, and that traces of this sequence of events should be observable in contemporary forms. Euryattus exhibits an unusual pattern of web‐dependency (Jackson, 1985). The principal eyes conform to those of ‘advanced’ Salticidae, but the anterior lateral eyes exhibit two features associated, so far, with the primitive Spartaeinae: transverse sections of the rhabdoms present rectangular (rather than circular) profiles, and the non‐pigmented glial cytoplasm is depleted of microtubules. These findings marginally support a case for Euryattus having primitive affinities, but their import is ambiguous, and the evidence cannot be regarded as conclusive. Possible affinities between the Gnaphosidae and Salticidae based upon common tactics of web‐invasion are qualified by a comment on the retinae of the two families.

Secondary retinae of a primitive jumping spider, Yaginumanis (Arachnida, Araneida, Salticidae)

Retinae of the secondary eyes of a primitive salticid spider, Yaginumanis sexdentatus (Yaginuma 1967) are described at the ultrastructural level. The structures of the anterior lateral, posterior lateral and posterior median eyes are identical. Receptor somata lie in the retinal cups. Each receptor bearing twin rhabdomeres is ensheated by (i) much-divided processes of non-pigmented glial cells whose somata lie distally in the retinal cups; and (ii) four processes of pigmented glial cells whose somata lie basally, below the receptive segments. Pigment granules in the latter are concentrated in the basal retina, and are not present at the level of the rhabdoms. The present findings support the placement of Yaginumanis in a newly erected Subfamily Spartaeinae by Wanless (1984), because of the likelihood of homology in the fine structural organisation of the secondary retinae of this genus and of the genus Portia.

Exocytotic shedding and glial uptake of photoreceptor membrane by a salticid spider.

Receptors in the anterior lateral eyes of salticid spiders possess paired rhabdomeres. The tips of the rhabdomeral microvilli lie adjacent to non-pigmented glial processes. Photoreceptor membrane is lost during turnover by a hitherto undescribed process: individual microvilli lengthen at their tips, taper, and are received by corresponding, coated endocytotic pits in the glial membrane. Pits detach as coated vesicles with coherent fragments of microvilli within them, lose their coats, and accumulate in the glial processes as disorderly membranous detritus. Some microvillus membrane disintegrates before local endocytosis, and appears to get into the glial arms distant from the parent rhabdomere by invaginations which are either endocytotic clefts or a tubulo-cisternal system, but whose precise nature is not yet clear. No photoreceptor membrane is lost by pinocytosis into the receptor cytoplasm. Analogies between the behaviour of this system and the phagocytosis of shed vertebrate photoreceptor membrane are briefly discussed.

Spectral sensitivities of jumping spider eyes

Spectral sensitivities of the anterior lateral, posterior lateral and anterior median eyes of the jumping spider,Menemerus confusus Boes. et Str. have been studied by recording electroretinograms (ERGs) and receptor potentials. The anterior and posterior lateral eyes have a single type of visual cell with a maximum spectral sensitivity at about 535–540 nm. The anterior median eye has four types of visual cells with maximum sensitivities at about 360, 480–500, 520–540 and 580 nm, respectively. The ERGs recorded from the optic nerve side (posterior part of the retina) were affected greatly by long wave chromatic light and those on the corneal side (anterior part of the retina) by short wave chromatic light, suggesting that each receptor layer contains a different photopigment.

Dual sensitivities of cells in wolf spider eyes at ultraviolet and visible wavelengths of light.

Intracellular recordings have been made from visual cells in principal and secondary eyes of in vitro wolf spider preparations. The responses of all cells to all wavelengths of light were graded depolarizations; no hyperpolarizations or nerve discharges were seen. Cells in a secondary eye, the anterior lateral eye, had a maximum sensitivity in the visible at 510 nm and a secondary maximum, or shoulder, of sensitivity in the near ultraviolet at 380 nm. Cells in principal eyes, the anterior median eyes, all responded maximally both in the visible at 510 nm and in the ultraviolet at 360-370 nm or less. However, there was no typical ratio of ultraviolet to visible sensitivities; the differences in log sensitivities (log UV/VIS) varied from 3.3 to -0.5. Each principal eye had a population of cells with different ratios. These populations varied with the time of the year, possibly due to changes in light upon the animals. Chromatic adaptations of cells in anterior median (but not anterior lateral) eyes resulted in small, selective changes in spectral sensitivities, and there was some facilitation of responses from cells repeatedly stimulated. It is concluded that cells of secondary eyes contain only a visual pigment absorbing maximally in the visible, while cells of principal eyes probably contain variable amounts of both this pigment and one absorbing in the ultraviolet as well.

The fine structure o the visual system of Lycosa (Araneae: Lycosidae). II. Primary visual centers.

Wolf spiders have four pairs of eyes distributed in three rows. The first row which lie in the frontal region of the caparace, just above the chelicera, contains four eyes: a medial pair known as the anterior medial eyes (AM eyes or principal eyes) and two smaller eyes known as the anterior lateral eyes (AL eyes). The second row which is located also in the frontal region of the prosoma consists of two big eyes. These are the posterior median eyes (PM eyes). The third row contains the posterior lateral eyes (PL eyes) which lie in the flanks of the prosomal caparace. The AL, PM and PL eyes are the so-called secondary eyes.

Observations on the fluorescence and function of spiders' eyes

Preliminary observations on spiders' eyes showed that certain eyes fluoresce in ultraviolet light and others do not. The response of these eyes to ultraviolet and visible light has been investigated to discover the relationship, if any, of eye fluorescence with eye function.In the first part of this paper it is shown that of eight spiders from families with widely differing habits, vision and behaviour, five species reacted to light fluctuations and to differences in brightness of the primary colours blue, green and red. Three species did not respond to lightand only two, S. scenicus and E. falcata, indicated a preference for blue light. It was also found that the visual sensitivity of S. secenicus extended into the ultraviolet. The second part of the paper gives the results of examination in ultraviolet light of the eyes of 40 species from 11 families. Spiders with poor sight and a preference for shade generally showed a strong fluorescence of all eyes. The anterior median and lateral eyes of those species with good sight fluoresced only weakly or not at all, whereas the posterior median and lateral eyes ofthese spiders fluoresced brightly.Freshly cut frozen sections of the eyes of two selected species, S. scenicus with good sight and C. similis with poor sight, were examined with the fluorescence, phase and polarizing microscopes. The localization of the fluorescence in these eyes is described and a fluorescent substance, common to all the spiders, was found in the lens of the eyes of most species examined.Additional information on the structure of the cornea and lens was also revealed by phase and polarized light microscopy.The results suggest that spiders' eyes respond to light in different ways and the fluorescent substance present in the lens of the eyes is related to eye function.

New Nebraska Spiders.*

Recent collections of spiders in the state of Nebraska have revealed the following new species. Brachybothrium lincolnianum n. sp. Male. In life, black or fuscous in color, the venter lighter than the dorsum and the carapace somewhat lighter than the abdomen. In alcohol, this color changes to a yellow or brown, the cephalothorax then being yellowish and the abdomen darker, a soft brown or tan. Eye area twice as wide as long; anterior median eyes separated from each other by an interval equal to more than twice the diameter of one of them and from the anterior lateral eyes by a space only slightly greater; the latter have a diameter two and one-half times that of the former. The posterior median eyes are as far apart as are the anterior lateral eyes, while the posterior lateral eye, the posterior median eye, and the anterior median eye of each side are in a row and form almost a straight line. The posterior lateral eyes have a diameter two-thirds as great as that of the posterior median eyes, while the posterior median eyes have a diameter about three-fourths that of the anterior lateral eyes, which are by far the largest eyes; posterior row slightly longer than the anterior.