Embryonic development of the solar-powered nudibranch <i>Phyllodesmium lizardensis</i> (Gastropoda: Nudibranchia)

In this pilot study we investigated the early embryonic development of the recently described solar-powered nudibranch species <i>Phyllodesmium lizardensis.</i> In previous studies <i>P. lizardensis</i> has been used as a model system to study the symbiosis between nudibranchs and their symbiotic dinoflagellates <i>Symbiodinium</i>, but the transmission mode of symbionts in the life cycle of this species remained unknown. Embryonic development in <i>P. lizardensis</i> was similar to related nudibranch taxa. Specimens laid clear gelatinous egg masses filled with relatively small egg capsules (81.25 ± 3.78 µm, <i>n</i> = 11). Zygotes developed into planktotrophic veliger larvae that hatched after about 85 hours. No <i>Symbiodinium</i> cells could be detected by means of light microscopy at any developmental stage in zygotes or unhatched veliger larvae. Vertical transmission of symbionts is therefore unlikely; the timing of <i>Symbiodinium</i> acquisition by this species remains unknown.