The morphology of the Limulus visual system. VI. Connectivity in the ocellus

Cell Tissue Res. 1975 May 27;159(1):39-47. doi: 10.1007/BF00231993.


An ocellus of the horseshoe crab, Limulus polyphemus, has been serially sectioned for light and electron microscopy, its sensory cells have been indexed, and the interconnections of a third of these traced. The ocellus contains 155 retinula cells and 26 arhabdomeric cells, which are secondary sensory neurons. Of these, 55 retinula cells constitute 7 quasi-ommatidial assemblages, each innervated by at least one and a total of 9 arhabdomeric cells. When known electrotonic coupling patterns are compared with gap-junctional connections, retinula cells sensitive to visible or ultraviolet light can be tentatively identified. Retinula cell axons contribute collaterals to a synaptic plexus, in which the arhabdomeric cells apparently do not participate.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Axons / ultrastructure
  • Brachyura / anatomy & histology*
  • Dendrites / ultrastructure
  • Eye / innervation*
  • Eye / ultrastructure
  • Intercellular Junctions / ultrastructure
  • Neural Pathways / ultrastructure
  • Retina / innervation
  • Synapses / ultrastructure