Figure 1

Developmental stages of S. roscoffensis . A. Green adult in ventral view with anterior facing upwards. The location of the statocyst is marked with an asterisk. Arrows point to the lateral edges, which are looped ventrally to form a ventral groove. The male genital pore (mg) and the bursal nozzle (bn) are located in the posterior half of the animal. B. Up to 20 embryos may be found in a single cocoon. C and D. Newly hatched juveniles yet devoid of symbiotic algae. Ventral view (C), and dorsal view (D), respectively. On the ventral side a groove is formed (g). The animals are completely covered with cilia (c). E. Close-up of the parenchyma of an adult specimen containing algae (arrowheads). Scale bars: 200 μm (A), 100 μm (B), 50 μm (C, D), 20 μm (E).