41 — Globose voilet snail, Janthina globosa

J. globosa from Papamoa Beach, 2016.

J. globosa from Papamoa Beach, 2016.
Looking down on the top of the spire.

A group of J. globosa from Papamoa Beach,
2016.

The globose voilet snail Janthina globosa Swainson, 1822 is found all around the world in warm seas. Unlike the previous species (J. exigua), J. globosa is found more commonly in the north and east of New Zealand. I suspect this is to do with the prevailing currents, as the west coast has for the most part, a cold water current coming up from the south and the north east coast a warmer water current coming down from the north.

Of the three violet snail species usually found in New Zealand waters J. globosa is the least common. It has a fragile shell and is shiny in appearance. The ones pictured below are about 15mm across. I've never actually found any; these were collected by my dad, while walking the dog.

Notice how they are darker on the bottom of the shell and how the spire is lighter. I'm speculating that this is to aid camouflage, as they orient upside-down on the surface of the water. It would be an advantage to look darker from above and lighter from below.







More info:

More pictures: http://www.mollusca.co.nz/speciesdetail.php?speciesid=946&species=%20globosa