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Multiple mechanisms of rhabdom shedding in the lateral eye of Limulus polyphemus
Author(s) -
Sacunas Robert B.,
Papuga M. Owen,
Malone Michael A.,
Pearson Anthony C.,
Marjanovic Milos,
Stroope Darrell G.,
Weiner William W.,
Chamberlain Steven C.,
Battelle BarbaraAnne
Publication year - 2002
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.10263
Subject(s) - limulus , opsin , biology , efferent , darkness , horseshoe crab , biophysics , anatomy , rhodopsin , retina , neuroscience , retinal , afferent , paleontology , biochemistry , botany
Rhabdom shedding in horseshoe crab lateral eye photoreceptors was studied with anti‐opsin and anti‐arrestin immunocytochemistry. Two, possibly three, distinct shedding mechanisms were revealed in animals maintained in natural lighting. Transient rhabdom shedding, triggered by dawn, is a brief, synchronous event that removes up to 10% of the rhabdom membrane. Whorls of rhabdomeral membrane break into vesicles and form compact multivesicular bodies. These debris particles are immunoreactive for opsin and are of a relatively uniform size, averaging approximately 2 μm 2 in area. Transient shedding requires that input from circadian efferent fibers to the retina precedes the light trigger, and cutting the optic nerve blocks efferent input and transient shedding. Light‐driven rhabdom shedding is a progressive process. Rhabdomeral membrane is removed by coated vesicles that accumulate into loosely packed multivesicular bodies. These debris particles label with antibodies directed against opsin, arrestin, and adaptin, and they have a large distribution of sizes, averaging almost 6 μm 2 in area and ranging up to 25 μm 2 or more. The amount of rhabdomeral membrane removed by light‐driven shedding has seasonal variation and depends on latitude. Light‐driven shedding does not require circadian efferent input. A possible third shedding mechanism, light‐independent shedding, is observed when transient shedding is blocked either by 48 hours of darkness or by cutting the optic nerve. Small particles, averaging 1.8 μm 2 in area, exhibiting opsin but not arrestin immunoreactivity can then be found in the cytoplasm surrounding the rhabdom. The nature of light‐independent shedding is not yet clear. J. Comp. Neurol. 449:26–42, 2002. © 2002 Wiley‐Liss, Inc.