(n.) A little eye; a minute simple eye found in many invertebrates.
(n.) An eyelike spot of color, as those on the tail of the peacock.
Example Sentences:
(1) Each ocellus has a cuticular lens located on the distal end of a cuticular cone which encapsulates the receptor cells.
(2) It appears, therefore, that the graded receptor potential, which survives the application of tetrodotoxin, is responsible for mediating synaptic transmission in the ocellus.
(3) The receptory area of the ocellus terminates in a tapetum which contains granules, soluble in alcohol.
(4) A third type comes from the median ocellus and can be traced into the cervical connectives.
(5) 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.
(6) Membrane potential changes following illumination of a photoreceptor cell in the lateral ocellus of a barnacle (Balanus eburneus) were studied by means of intracellular recording and polarization techniques.
(7) The decay of the depolarizing and hyperpolarizing components of the visual signal was studied by recording intracellularly from single receptor axons of the median ocellus of the giant barnacle.2.
(8) Each ocellus has about 80 retinula cells whose axons project to corresponding ganglia from which 4 giant afferent interneurons (per ganglion) project to the brain.
(9) The visual pigment of each ocellus of mosquitoes reared in darkness was characterized by microspectrophotometry, and found to be the same.
(10) However, the two bilaterally positioned cells destined to become the pigment cells in the first step are still equipotent at this stage in that they can give rise to either the ocellus or otolith.
(11) Anatomically, the sensory cells of the dorsal ocellus of Tenodera were determined histologically to be grouped into two distinct regions, each group making its own separate contribution to the ocellar nerve.
(12) In the absence of this interaction, melanocyte specification proceeds along the dominant pathway that results in the differentiation of an ocellus.
(13) Five cells are accessory cells of the sensory structures: three lens cells and a pigment-cup cell in the ocellus, and a single pigment cell in the otolith.
(14) Of the remaining 79 cells, 36 are sensory, 17 receptors in the ocellus and 19 presumed hydrostatic pressure receptors; these lie on the right and left sides of the sensory vesicle, respectively.
(15) The light-evoked slow potential responses of the postsynaptic units are not altered by the application of tetrodotoxin to the ocellus.
(16) A small number of cells in the supraesophageal ganglion hyperpolarize when the median ocellus is illuminated and depolarize when it is shadowed.
(17) The spectral sensitivities of single Limulus median ocellus photoreceptors have been determined from records of receptor potentials obtained using intracellular microelectrodes.
(18) The spectral sensitivity curve for the repolarizing responses peaks at 480 nm; it is the only spectral sensitivity curve for a median ocellus electrical response known to peak at 480 nm.
(19) Our main conclusions are that: 1) the photoreceptors (retinular cells) of the lateral eye project only to the lamina; 2) the photoreceptors of the lateral rudimentary eye project to both the lamina and medulla; 3) the photoreceptors of the median ocellus project only to the ocellar ganglion; and 4) the photoreceptors of the rudimentary median (endoparietal) eye project to the ocellar ganglion and also into the optic tract.
(20) The view that the ocellus of the cockroach represents a degenerated structure can no longer be supported.
Stemma
Definition:
(n.) One of the ocelli of an insect. See Ocellus.
(n.) One of the facets of a compound eye of any arthropod.
Example Sentences:
(1) Response properties and spectral sensitivities of a functional class of medulla neurons that received dominant input from a single stemma in the swallowtail butterfly larva were examined with regard to neutral and chromatic backgrounds.
(2) The remaining two types of neurons dominated by the dichromatic stemma showed non-color-opponent and broad action spectra ascribable to a synergistic effect of the two classes of photoreceptors.
(3) Many neurons exhibiting an antagonistic interaction between signals from one particular stemma (center) and neighboring stemmata (surround) were found in the second optic neuropil (medulla) of the larval swallowtail butterfly.
(4) The larval medulla neurons described may form parallel, elementary color-coded channels in the medulla neuropile to combine the outputs of the different color receptors in a single visual unit (stemma) into specific color-opponent signals.
(5) Eight types of neurons were dominated by a dichromatic stemma with blue and green receptors.
(6) All eight types of neurons dominated by a trichromatic stemma (with UV, blue, and green receptors) were color opponent.