Fig. 7

Spiochaetopterus costarum, cerebral eye, a LM, semithin section, b-e, TEM; a) Part of cross section with left eye (ey) situated in a tube-like invagination filled with cuticle (cui) and extending down to the neuropil (np) of the brain (br), pigment cells form flat layer of medial side; b) Low power TEM micrograph showing the eye in longitudinal section, retina composed of numerous PSCs (psc) between which thin processes of PRCs running apically (white arrows), these terminate apically between PSCs (black arrowheads), cuticular invagination (cui) occupied by numerous cell processes (smv); c) Bottom of invagination with basal part of retina at higher magnification, monociliary sensory dendrites (sd) of PRCs terminate between PSCs (psc), invagination (cui) basally occupied by sensory cilia (sc),sensory microvilli (smv) and microvilli of PSCs, the latter forming apical layer of parallel microvilli (mv), arrowhead points to basal body in PSC; d) Intermingling processes of PRCs and PSCs; e) Higher magnification of sensory dendrite (sd) with sensory cilium (sc). Abbreviations: bb basal body, br brain, cui cuticular invagination, ecm ECM, ep epidermis, ey eye, if intermediate filaments, mv microvillus of PSC, ne neurite, np nucleus of PSC, nr nucleus of PRC, pg pigment granule, prc PRC, psc PSC, sc sensory cilium, sd: sensory dendrite, smv sensory microvilli, za zonula adherens