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Dive Dry with Dr. Bill

#688: Mistaken Identity

Jacques-Yves Cousteau is well known for his quote "People protect what they love." A similar concept was put forth by the Senegalese environmentalist Baba Dioum back in 1968 in a speech before the general assembly of the International Union for the Conservation of Nature (IUCN). He said ""In the end, we will conserve only what we love, we will love only what we understand, and we will understand only what we are taught." This has essentially been my philosophy since I began teaching marine biology 47 years ago. It is the reason IU write these columns and produce my videos.

Some people love whales and dolphins and strive to protect them. Others are driven to ecstasy by the beautiful shell-less snails known as nudibranchs. There are even those who cherish the strangest of undersea critters like the hagfish. It is important to love and protect specific species and related groups, but unless one preserves the habitats in which they live, such efforts will ultimately be useless. My focus is on understanding, loving and preserving kelp forest ecosystems (although I'm known to stray to coral reefs in winter!).

There are those who love the hard shell finish of Turtle Wax... er, I mean the molluscs known as snails and their often beautiful shells. Sadly some of these snail "lovers" are shell collectors rather than snail protectors. Of course if they collect only the discarded shells of deceased gastropods, that is reasonably cool. However the shell trade often takes living animals from natural habitats.

For those snail enthusiasts who love to see them alive in their natural habitat, this Bud (er, column) is for you! Today I'm focusing on one of the more intriguing shelled snails in our kelp forests. In researching this column I discovered that I may have misidentified this snail for nearly 50 years! I always thought it was the leafy hornmouth (Ceratostoma foliatum) but am now wondering if it might be the three winged murex (Pteropurpura trialata).

Both are members of the murex family. Both appear very similar to my non-malacological eye, even with my glasses on. I'm not a snail expert by any means (although I do like escargot). I hope someone who knows will wander upon this column and clue me in. Fortunately their ecology is similar so whichever species it is, this should cover it!

These snails are both found in our waters. However, the leafy hornmouth, found from Alaska to San Diego, is considered uncommon south of Pt. Conception. The three winged murex is a more southern species found from Bodega Bay to Baja and common in southern California but more rare north of Palos Verdes. Based on distribution alone, it seems more likely to be the latter species.

Both species have shells that kind of resemble the helmet of a Spanish conquistador, at least if you have a vivid imagination like myself. Both have three flanges projecting from the shell, one to either side of the opening or aperture where the critter hides and one on top. These flanges have been the subject to debate regarding their function. Some scientists feel they serve to make it more difficult for a hungry predator like a sheephead to dislodge them from the rock. Others believe they allow the snail to land on its "foot" if they fall through the water column... kind of like a cat! Maybe they just like ornate decorations. The three-winged murex may exhibit completely white shells, but more often they are brown and white or beige like the leafy hornmouth.

As far as diet is concerned, both are predators. Yep, you probably think of snails as herbivores since on land they often devastate your garden. These murexes munch by boring holes into the shells of their prey using their rasp-like radula. Up north the leafy hornmouth feeds on barnacles and bivalves but in our region it chows down on tube snails. The three-winged murex feeds on slow moving snails including limpets, but also on the attached tube snail. Easy pickings!

No "Dive Dry" column would be complete without mention of mating behavior. Males and females are separate in both species. When it's time to do "it," leafy hornmouth snails gather together in clusters up close and personal. In both species females lay their yellow egg capsules on the rocks. Leafy hornmouth egg capsules contain up to 80 individual eggs and during her lifetime the female may lay over 15,000 eggs. Wow... imagine the cost if they all needed day care!

In the leafy hornmouth the eggs develop into early larval stages within the egg itself. When they hatch out, they do so as miniature snails. Way up north in the colder waters of Washington state, this entire process may take about four months. Given the fact they hatch as developed snails rather than planktonic larvae, I have to assume dispersal via the currents is minimal to non-existent. However, they may disperse as young or adults on drifting seaweed such as kelp.

Whichever species this is, I will love it and protect the ecosystem that sustains it. I hope you do, too. However, I do hope some knowledgeable mollusc specialist will edumacate me and finally clear up this latest mystery from the deep.

© 2016 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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The yet-to-be identified murex (which is its best side?); an "albino" shell suggesting it may be the
three-winged murex and the underside of a shell showing operculum with an inset of a cluster of egg capsules.

This document maintained by Dr. Bill Bushing.
Material and images © 2016 Star Thrower Educational Multimedia