Fig. 7 in Ultrastructural differences in presumed photoreceptive organs and molecular data as a means for species discrimination in Polygordius (Annelida, Protodriliformia, Polygordiidae)

Fig. 7 Differences in the distribution of receptor cells within most frequent sensory organs between P. lacteus and P. appendiculatus (TEM, crosssections). a–c Three different sensory organs in P. lacteus; cavities with numerous sensory microvilli emerging from rhabdomeric receptor cells. Sensory processes of type 3 cells (sc 3) are most frequent due to more than seven rhabdomeric receptor cells per organ (up to three apices visible in each organ). The ecm surrounds the photoreceptive region toward the body cavity. d–f Three different sensory organs in P. appendiculatus with processes of ciliary sensory cells, especially ciliary branches of type 1 sensory cells. Arrows in e indicate several sectioned unbranched cilia of type 2 sensory cells. Note that besides differences in dominance of sensory processes the sensory organs are all in all smaller compared to the organs in P. lacteus (indicated by scale bars). ecm extracellular matrix, sc 1, sc 3 sensory cell type 1, 3