The Dove Snail Attacks!

I had a bit of an eyebrow-raising experience today.  I was trying to photograph a common snail, the Carinate Dove Snail (Alia carinata).  This marine snail can be found in a variety of habitats, e.g., rocky shores in tidepools and among surfgrass and seaweeds and in harbors among eelgrass.  It's fairly small (most individuals are probably ~10 mm long), elongate, and usually brownish/black in color.  Here's an example:

 

 

This species is common enough that you can overlook it.  But I needed a photograph, so I was looking at several of them under a microscope today when I came across one in a puzzling position.  I wasn't sure what was going on at first:

 

 

 

So that's the snail, with its siphon extended up and to the right and its foot flat against the surfgrass blade (in this photo the foot has blue highlights).  You can see the snail's short tentacles, and you can also see a small dark eye on the right hand tentacle.  But what's below the tentacles?  Here's a side view:

 

 

 

Ahhh!  The snail had extended its proboscis (a tubular feeding structure) into an egg capsule filled with developing larvae.  It was vacuuming up the veliger larvae!  I hadn't seen this behavior before, so I wasn't sure I was interpreting it correctly at first, but there was no doubt.  The snail reached around inside the egg capsule and cleaned out almost every developing larva.  (The egg capsule/larvae belong to a different snail species, Lacuna marmorata.)

 

Even better, Eric wasn't far away and he came over just in time to capture a video of this fascinating feeding behavior (see below).  

 

I loved learning something new and unusual about a common local snail.  In some ways the name "dove snail" suggests a rather sedate snail, but I'll never look at Alia the same way again!

 

And here's the best part — the video!  Watch for the snail approaching the egg capsule, inserting its proboscis inside, then using suction and its tongue-like radula to ingest the tiny larval snails.  You'll see the radula flicking in/out at the tip of the proboscis.  (At this stage, the larval snails have shiny little shells.)

 

 

 

Many thanks to Eric for a memorable video!