Fig. 1.

Stereomicroscope images of early embryos of small-spotted catshark used in the present study, according to the developmental stages (St) of Ballard et al. (1993). During the stages represented here (St18–24, 26) the metamerization of the pharynx and completion of the somite set occurs. The pharyngeal pouches become progressively visible from St18 to St20 (A-C). Pharyngeal clefts progressively open from St21 onwards (D-H). The optic anlage is clearly visible from St18 onwards (arrowheads), as well as the lens rudiment from St22 onwards (asterisks; E-H). The dotted line in (H) indicates the frontal plane of the section, parallel to the ventral optic fissure (arrow). OtV, otic vesicle. Scale bars: 1 mm.