Tide Lines: Mysterious variation on snail theme
by Judith Lea Garfield
Aug 02, 2013 | 2060 views | 0 0 comments | 7 7 recommendations | email to a friend | print
A typical <i>N. spadicea adult</i>, about 2 inches long. Note the pale orange-brown mantle and smattering of dark-brown dots. The otherwise white shell has chestnut-brown markings. ©2013 Judith Lea Garfield
A typical N. spadicea adult, about 2 inches long. Note the pale orange-brown mantle and smattering of dark-brown dots. The otherwise white shell has chestnut-brown markings. ©2013 Judith Lea Garfield
slideshow
Juvenile: The colors and pattern of this inch-long cowry are typical of a young Neobernaya spadicea. The mantle is tinted orange-brown with dark dots, and the shell covered by bands of light and dark brown. Kevin Lee
Juvenile: The colors and pattern of this inch-long cowry are typical of a young Neobernaya spadicea. The mantle is tinted orange-brown with dark dots, and the shell covered by bands of light and dark brown. Kevin Lee
slideshow
I may have taken a year off from writing Tide Lines but not so from diving, underwater photography, and learning more marine science. Now reinvigorated, and with sea pen (and the occasional pun) in hand, I’m enthused to share with you more ocean mysteries, dilemmas, and dramas taking place off our coast.

Explorers take note: We know less than five percent of what lives in the ocean, so if you want to discover something new, that’s the place to go for the highest rate of return on your adventure investment. Recently, I scored some payback by discerning if not a new species, then maybe a novel variant of a marine snail called a cowry. Here is some background to catch you up.

For many snail-type animals, it’s all about the shell, because that’s where the beauty lies. Not so for the cowry, a mollusk whose extravagant fleshy bits (mantle) of orange-brown scattered with dark-brown dots must be admired along with the shell’s slick artistry. The “chestnut” in the chestnut cowry (Neobernaya spadicea), the only true cowry species living off our coast (all others lead a tropical existence) isn’t meant to fit the cozy image of the nut stereotypically found roasting on an open fire. The top part of the smooth and glossy egg-shaped shell has a patch of rich chestnut brown. The rest of the shell is snowy white.

The cowry’s underside reveals a long slit edged with blunt teeth, which the two halves of the showy mantle slide over at will, either to completely encase the shell or to retract the exposed flesh into the shell. Stretching is accomplished by inflating the soft, bumpy tissue with water and body fluids so that, like an incoming tide, the flesh expands out and over the shell’s surface. If touched or otherwise threatened, the mollusk instantly pulls in its fleshy skin via a quick muscular movement, a cringe if you will, leaving its hard, shiny armor aimed at the disturbance. This sliding-door skin mechanism also acts to police hitchhikers and other potential squatters (typically the bane of slow-moving critters) from loitering or taking up residence on the shell’s surface. Thus, a cowry’s distinctive mantle and shell are equally substance and style.

Young cowries are styled a bit differently from adults. At early-stage development, the shell is wrapped in color bands of alternating dark brown and light brown. The mantle, however, is more similarly matched to the adult: light to dark orange-brown with a scattering of dark-brown dots. Herein lies the mystery of my observed cowry. I was finning along the canyon wall in the reserve off La Jolla Shores at about 55 feet deep when an inch-long mollusk caught my eye. The shell’s color, pattern and size designated it as a juvenile but the colorless fleshy mantle cuddling its shell didn’t look familiar. Forget the orange-brown tint, where were the scattered dots?

Although research confirmed my suspicions that it was indeed a chestnut cowry, without the animal in hand for genetic evaluation, I can’t say decisively whether or not it was a different species. I suggest it is a color (or lack thereof) variant, but if you extrapolate from this article’s first sentence, you’ll appreciate that a dearth of publications on and images of this critter prevents me from knowing for certain. Though the mystery remains for now, I at least can add to the pool, er, puddle of knowledge on cowries. And at some point, I hope to come across others who can definitively shed light on this outlier phenotype or who will find my sighting a useful data point to aid in their own cowry investigations.

— Judith Lea Garfield, naturalist and underwater photographer, has authored two natural history books about the underwater park off La Jolla Cove and La Jolla Shores. Visit www.TideLines.org, or email Judith@TideLines.org.
Comments
(0)
Comments-icon Post a Comment
No Comments Yet