Some Unique Features in Compound Eyes of Two Isopods
I have observed certain unique features in the ultrastructure of the compound eyes of the terrestrial isopod crustaceans Porcellio scaber and Armadillidium vulgare, using both scanning and transmission electron microscopy.Only about twenty ommatidia, arranged into four rows, constitute an eye, giving the organ the appearance of a cluster of grapes (Fig. 1). A few trichoid sensilla are interspersed between the ommatidia.The dioptric apparatus of each ommatidium is composed of a biconvex, cuticular lens and an underlying spherical crystalline cone. In these isopods each crystalline cone is the secretion of only two cells (Fig. 2), rather than four as in most malacostracans. The suture line between the two cone hemispheres is always parallel to the long axis of the ommatidium.