Figure 1

Scanning electron micrographs of the embryonic and larval development of Argyrotheca cordata. Anterior faces upward and scale bars equal 50 μm. (A) Early gastrula with blastopore (arrow). (B) Ventral view of an embryo at the onset of differentiation of the three-lobed larval bodyplan comprising apical lobe (AL), mantle lobe (ML), and pedicle lobe (PL). The arrowhead points to the region of the larval apical ciliary tuft. The arrow points to the larval mouth which corresponds to the blastopore. (C) Dorsal view of a larva with distinct anlagen of the three body lobes. (D) Ventral view of a specimen of the same ontogenetic stage as the one in C with reduced larval apical ciliary tuft (arrowhead) and with the almost closed blastopore (arrow). (E) Three-lobed larva at the onset of setae formation (double arrowheads), dorso-lateral view. (F) Lateral view of a fully differentiated larva showing two of the four pairs of larval setae (double arrowheads) and a distinct primordial hump (asterisk).