Are you going to be glad you checked into this blog! It has been quite a year for interesting plankton offshore of Bodega Head, but this has got to be one of the "coolest" larvae that we've ever seen!
This is the veliger, or the larval stage, of a heteropod called Carinaria japonica. It was collected ~1 km off Bodega Head on 1 December 2014. I introduced heteropods in September (review that post here), but that was a different family (the atlantids). Now you get to meet Carinaria. As adults, they're sometimes called "sea elephants."
Here's a basic illustration of what you're seeing:
Modified from Heteropoda by Thiriot-Quiévreux (1973).
And now for a few close-ups highlighting some of these features.
The velum (ciliated structure used for swimming and feeding) is divided into 6 velar lobes. Note that the lobes are extremely long and slender and they have brown pigment patches at their tips (see below).
Two black eyes are visible when the veliger is floating with the opening of the shell facing up:
The shell itself is beautiful and transparent, with several whorls. In the next picture, you can also see one tentacle being extended upward. The operculum ("trap-door") is being held out behind the shell.
Believe it or not, they can withdraw those long velar lobes completely into the shell! Although it's a little hard to tell what's going on in the next picture, you're mostly seeing the shell in the background, the dark tips on the retracted velar lobes, and the operculum at the lower right.
And yes, now you can enjoy a video of these Carinaria veligers in action!
You'll see them swimming...and then there are several clips of feeding behaviors. Watch for food particles moving along the edges of the long velar lobes.
They use long cilia to drive food particles into a food groove where they are moved along by shorter cilia, like a conveyor belt, to the mouth.
One section of the video highlights a food particle. Watch it bounce out to the right — it's recaptured and then you can follow it as it moves along the perimeter of velar lobes on its journey towards the mouth.
There's also a "mystery behavior" in the video. It looks like cleaning behavior, but we're not certain. See what you think!
Many thanks to Emily for bringing these heteropod veligers to our attention. We can share them with you because of her.
Isn't it fun to think about these wonderful 6-armed larvae swimming just offshore of Bodega Head!