Larval development and metamorphosis - Aplysia oculifera
A. Colour change in egg ribbon from freshly laid (bright yellow) to a brown just before hatching. B. Veliger larvae - shell length 0.35mm. C. Young slug, 1 day after settlement (metamorphosis). D. 12 days after settlement - 0.9mm long. E. 23 days after settlement - 1.8mm long. F. 36 days after settlement - 4.0mm long. PHOTOS: Itai Plaut.
To accompany Itai's photos here is a summary of the information about larval growth and development in A. oculifera from Plaut, Borut & Spira (1995).
Larvae hatch 8-9 days after eggs are laid, the eggs changing colour from yellow to brown. The veliger larvae were fed on the unicellar algae Isochrysis and reached full size in about 50 days. The veligers could survive however, for up to 330 days.
A range of algae from their natural habitat were tested in settlement experiments to see if any of them had a natural chemical which would trigger metamorphosis and settlement of the larvae. The red algae of the genera Dasia, Jania, Hypnea and Liagora, and the green algae Enteromorpha intestinalis and Ulva sp did, but Cladophora sp, Codium spand a number of brown algae did not.
Settled larvae only grew and survived when fed Enteromorpha intestinalis. Veliger larvae were still able to settle out of the plankton and metamorphose after 6 to 8 months. Larvae that settled and metamorphosed on non-food algae survived for 22 days without feeding suggesting that in nature they would have a chance of finding their food algae, (Enteromorpha), before starving. Postmetamorphic juveniles and adults feed on the green alga Ulva.
See Itai Plaut's message [#2444].
• Plaut, I., A. Borut and M.E. Spira (1995). Growth and metamorphosis of Aplysia oculifera larvae in laboratory culture. Marine Biology,122: 425-430.
Rudman, W.B., 2000 (May 25) Larval development and metamorphosis - Aplysia oculifera. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/aplyocdev