The Functional Organization within the Ommatidium of the Lateral Eye of Limulus

Smith, Thomas G.; Baumann, Fritz

doi:10.1016/s0079-6123(08)63248-3

Cited by 55 publications

(35 citation statements)

References 42 publications

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“…Impulses were never recorded in any photoreceptor soma, not even through the electrical connexions to the other two cells (cf. Smith & Baumann, 1969;Shaw, 1969). The slow potential could so readily be seen with various methods of extracellular recording from the ocellar axons that any impulses present would have been clearly revealed, but again none attributable to the receptor axons were found.…”

Section: Barnacle Photoreceptor Signalsmentioning

confidence: 95%

Decremental conduction of the visual signal in barnacle lateral eye

Shaw¹

1972

The Journal of Physiology

102

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SUMMARY1. There are problems associated with the notion that slow potentials alone are used to transmit information in the early stages of some visual systems. This idea and alternatives have been tested on the barnacle lateral ocellus, a simple eye with only three photoreceptors, each with its own axon about 1 cm long.2. All of the receptors have very similar properties including spectral sensitivity, and are also electrically coupled together. Impulses cannot be recorded from any of the cell bodies, all ofwhici have been impaled as shown by dye marking.3. No impulses can be recorded externally from most of the ocellar nerve or intracellularly from the receptor axon terminals. Impulses driven by light, sometimes recorded in the final part of the nerve, are believed to originate in other axons.4. During illumination of the eye, current enters the receptor soma and leaves via the rest of the axon. This is consistent with the idea that the axon acts as a purely passive cable. The passive behaviour was also demonstrated in a comparison of the relative attenuation down the axon, of hyperpolarizations and depolarizations.5. Calculations based on the supposed electrical constants of the somas showed that the slow potential itself was unlikely to be the visual signal, since it would be enormously attenuated by passive spread down the long thin axons. To check this, the axon terminals in the supraoesophageal ganglion were penetrated and identified by electrical and dye-marking criteria. In fact, the slow potential was attenuated in the most favourable

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Section: Barnacle Photoreceptor Signalsmentioning

confidence: 95%

Decremental conduction of the visual signal in barnacle lateral eye

Shaw¹

1972

The Journal of Physiology

102

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“…Ultramicroscopic studies (Jinks et al, 1993) have shown that the isolated cells closely resemble cells in situ, suggesting that the increase in input resistance (decrease in the passive conductance) is probably not the result of loss of membrane during dissociation of the lateral-eye retina. Borsellino et al (1965) and Smith and Baumann (1969) calculated that the membrane of a photoreceptor cell within an ommatidium of the lateral eye of Limulus, excluding the electrical junctions between the cell and other cells in the same ommatidium, has a resistance of about 50 MQ. In view of this, the input resistances of cells dissociated from the lateral eye, which we observed to be large in comparison with cells in situ (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Just after light onset at intermediate to high intensities, the cell responded with a transient depolarization which subsequently decayed away to a steady-state depolarization. The transient was usually preceded by what appeared to be a large bump; this regenerative event [see Smith & Baumann (1969) for a review; Millecchia & Mauro, 1969a] was present in the receptor potentials of both isolated cells and cells in situ (Fig. 2C).…”

Section: Light Sourcementioning

confidence: 99%

Photoreceptor cells dissociated from the compound lateral eye of the horseshoe crab, Limulus polyphemus, II: Function

1993

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A combination of enzymatic digestions and mechanical disruption was used to isolate photoreceptor cells from the compound lateral eye of the horseshoe crab, Limulus polyphemus. The cells were maintained in a culture medium and tested for function using whole-cell and cell-attached patch configurations of the gigaseal technique. The cells dissociated from the eye generated spontaneous voltage and current bumps in the dark, and depolarized in a graded fashion to increasing intensities of light over several decades, producing responses similar to those of cells in vivo. Currents evoked during voltage clamp were similar to those in ventral photoreceptor cells of Limulus, although transient currents in the dark-and light-activated currents were smaller in isolated lateral eye cells, perhaps because of the slow speed and spatial nonuniformity of the clamp in these large cells. In addition to isolated cells, dissociation of the compound eye produced small clusters of cells and isolated ommatidia which were also tested for function. Comparison of the electrical characteristics of isolated cells with those of cells in small clusters and in their ommatidial matrix suggests that the electrical junctions normally connecting photoreceptor cells within an ommatidium are functional in the latter groups, but not in isolated cells. Cell-attached patches of rhabdomeral membrane of isolated cells contained light-activated channels, resembling those observed in ventral photoreceptor cells, but no voltage-activated channels. Similar patches of arhabdomeral membrane contained voltageactivated channels, but no light-activated channels. We conclude that this preparation is suitable for studies of processes involved in generating the light response in invertebrate photoreceptor cells.

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“…But interestingly, the electrical junctions between retinular and eccentric cells are rectifying, such that depolarizing current flows from retinular to eccentric cells but not in the other direction (Smith and Baumann, 1969). Therefore, if eccentric cells depolarize in response to UV light, the current would not dissipate into retinular cells; rather, it could depolarize the eccentric cell sufficiently to produce action potentials or increase the likelihood that action potentials are produced in response to retinular cell depolarization.…”

Section: Lpuvops1 Is Expressed In Le Eccentric Cellsmentioning

confidence: 99%

Opsin expression in Limulus eyes: A UV opsin is expressed in each eye type and co-expressed with a visible light-sensitive opsin in ventral larval eyes

Battelle

Kempler

Harrison

et al. 2014

Journal of Experimental Biology

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The eyes of the horseshoe crab, Limulus polyphemus, are a model for studies of visual function and the visual systems of euarthropods. Much is known about the structure and function of L. polyphemus photoreceptors, much less about their photopigments. Three visiblelight-sensitive L. polyphemus opsins were characterized previously (LpOps1, 2 and 5). Here we characterize a UV opsin (LpUVOps1) that is expressed in all three types of L. polyphemus eyes. It is expressed in most photoreceptors in median ocelli, the only L. polyphemus eyes in which UV sensitivity was previously detected, and in the dendrite of eccentric cells in lateral compound eyes. Therefore, eccentric cells, previously thought to be nonphotosensitive second-order neurons, may actually be UV-sensitive photoreceptors. LpUVOps1 is also expressed in small photoreceptors in L. polyphemus ventral larval eyes, and intracellular recordings from these photoreceptors confirm that LpUVOps1 is an active, UVsensitive photopigment. These photoreceptors also express LpOps5, which we demonstrate is an active, long-wavelength-sensitive photopigment. Thus small photoreceptors in ventral larval eyes, and probably those of the other larval eyes, have dual sensitivity to UV and visible light. Interestingly, the spectral tuning of small ventral photoreceptors may change day to night, because the level of LpOps5 in their rhabdoms is lower during the day than during the night, whereas LpUVOps1 levels show no diurnal change. These and previous findings show that opsin co-expression and the differential regulation of co-expressed opsins in rhabdoms is a common feature of L. polyphemus photoreceptors.

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The Functional Organization within the Ommatidium of the Lateral Eye of Limulus

Cited by 55 publications

References 42 publications

Decremental conduction of the visual signal in barnacle lateral eye

Decremental conduction of the visual signal in barnacle lateral eye

Photoreceptor cells dissociated from the compound lateral eye of the horseshoe crab, Limulus polyphemus, II: Function

Opsin expression in Limulus eyes: A UV opsin is expressed in each eye type and co-expressed with a visible light-sensitive opsin in ventral larval eyes

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