Blade runner

I first wrote about Surfgrass Limpets (Lottia paleacea) several years ago (yikes, almost 5½ years ago now!) — see the post called "Chemical camouflage" on 7 June 2012.

Tonight I took a couple of pictures of this limpet that made me curious:

 

Remember that Surfgrass Limpets only live on surfgrass (Phyllospadix spp.) blades, which are very narrow (depending on the species of surfgrass, only ~0.5-4 mm across).

Generally when I see a Surfgrass Limpet, it's a single individual on a blade.  This is the first time I recall finding two limpets next to each other.  So then I wondered — can Surfgrass Limpets turn around on the blade?  Or, do they only move back and forth?  If there are two limpets on one blade, do they compete for food?

Here's the next photo:

 

I noticed at least one individual that looked different from the others — it was smaller and much paler, appearing pale green, at least when looking down on a cluster of surfgrass blades.

Many of the Surfgrass Limpets we see are brown, and they're often ~10 mm long.  This individual was only ~4 mm long (note millimeter marks on the ruler above).  Is this a juvenile Surfgrass Limpet?  If so, how old is it?  What time of year do the adults spawn?  When do the larvae settle out of the plankton?  Is the pale coloration a variation, or is it more typical of juveniles, or is it a signal of new shell growth?

Lots of questions for which I don't have answers, but it's always fun to wonder, especially when you look at a familiar species from a different perspective!