Species: Hermissenda crassicornis
Phylum: Mollusca
Class: Gastropoda
Order: Opisthobranchia
Last week, we collected a pair of Hermissenda crassicornis on the San Carlos Beach breakwater. Even though individuals of this species are simultaneous hermaphrodites (each individual contains both male and female gametes at any given time), current evidence suggests that they reproduce exclusively via allogamy (the sperm from one individual must fertilize an ovum from another individual; self-fertilization is either not possible or not common). This meant that we had to encourage our specimens to mate before we could observe any embryonic development:
Several days after excretion, developing veligers (free-swimming nudibranch larvae) became active within their rapidly-dissolving egg capsules. The tubes around the capsules kept the fertilized eggs in a spaghetti-like mass until they were ready to hatch.
Several egg capsules broke free during collection, and provided an excellent view of developing veligers. Close inspection reveals the embryonic shell (looks like a snail shell) that will disappear later in the organism's development.
Hatched veligers are fast swimmers, but the putting them in the correct dish corrals them long enough to make basic observations about their body plan. Shortly before the following videos were taken, we fed these larvae red microalgae. As a result, their gut compartments have a distinctive pink glow:
Timeline of events:
Nudibranchs collected 4/5/13
Eggs discovered 4/12/13
Beginning veliger development noticed 4/15/13
Full encapsulated veligers discovered 4/16/13
Hatched veligers dominate 4/18/13
Our goal:
- Andrew Miller
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