Fig. 6

A Expression patterns of Slit/Robo orthologs in Alboglossiphonia lata embryos using fluorescent in situ hybridization. FWMISH was carried out after the appearance of pigmentation in the eyespots. Anterior is up in all views unless indicated otherwise. Asterisks indicate photoreceptor cells (PRCs). a: Head region of A. lata juvenile showing the 3 pairs of eyespots (white arrowhead). b: Ala-slit expression pattern in a pair of longitudinal narrow patches (white arrow) between eyespots. c: Ala-robo1 is expressed in presumptive photoreceptor cells of 3 pairs of eyespots (open arrowhead). d: Ala-robo2 is expressed in presumptive pigmented supporting cells of 3 pairs of eyespots (open yellow arrowhead). e: Head region of Helobdella austinensis juvenile showing the 1 pair of eyespots (white arrowhead). e’-e’’: Hau-robo2 was used as a marker to compare the expression pattern of transcripts of the Alboglossiphonia lata robo2 ortholog. Hau-robo2 is expressed in the region of photoreceptor cells (PRCs, yellow arrowhead) including extra ocular PRCs (open yellow arrowhead). Scale bar: 100 μm in a-d; 100 μm in e-e'' B Pseudocolorized laser scanning microscopic (LSM) view of histological sections of adult A. lata and H. austinensis. a: A. lata has 3 pairs of eyespots with the first pair located closely each other. a’-a’’’: Internal structure of A. lata eyespots is composed of pigmented supportive cells (PSCs) and phaosomal photoreceptor cells (PRCs, asterisk). b: 1 pair of eyespots is clearly visible in anterior head of H. austinensis. b’: pigmented eyespot of H. austinensis is composed of PSCs and phaosomal photoreceptor cells (PRCs, asterisk). Scale bar: 100 μm in a-b; 10 μm in a-a''', b'. C Schematic summary of the combinatorial expression patterns by which robo genes are proposed to specify pigmented and cryptic eyespots in two glossiphoniid leech species