Sunday, August 15, 2010

Autobiography of a Shell

In August, Science + Story will be going to the beach--figuratively, anyway. Here is the first installment, on shells.

Marble Cone (Conus marmoreus), 31 to 150 mm, common throughout the Indo West Pacific, including the Philippines, where I spent part of my childhood. The Marble Cone is a carnivore of the rocky bottom.
Like a message in a bottle, every shell on the beach has a story to tell. Each turban, limpet, conch, and cowrie can tell the trained eye stories about how and where it lived, and even battles it fought against storm, surf, and predator. Authors Jerry Harasewych and Fabio Moretzsohn teach us, in this spendidly conceived and realized book, how to train our own eyes to read and recover those stories.
It is second nature to us to admire the delicate shape, color, and beauty of a perfect specimen. Taking the time to "read" each shell as an autobiography of the animal that produced it is often just as rewarding. 
Harasewych, of the Smithsonian, and Moretzsohn, of the Harte Research Institute for Gulf of Mexico Studies at Texas A&M University, have not merely provided a deluxe field guide. They've chosen the six hundred shells showcased in the book's 656 pages to provide a cross section of the shell-bearing mollusks from around the world. As the authors point out in the introductory pages, "molluscan diversity is dominated by small animals"--most the size of a fingernail or smaller. A representative selection of shells would be small snails, and a lot of them. We wouldn't see such wonders as the Lazarus Jewelbox, the Pagoda Prickly Winkle, the Modest Worm Snail, or the Telescope Snail.

Windowpane Oyster (Placuna placenta), 100 to 200 mm, Tropical Indo-West Pacific. This oyster yields the capiz shell used widely for wind chimes and other crafts in the Philippines, where there is a major Placuna fishery.

I did wish for a few more images of the living animals, and for some backstory about some of the mollusks' common names. Surely there is a tale to be told about the Poor Ittibittium, Ittibittium parcum? I also wanted to know what made the Paradoxical Blind Limpet paradoxical. But those are quibbles. That would have been a 900-page book.

Gumboot Chiton (Cryptochiton stelleri), 100 to 400 mm, Hokkaido, Japan, to Aleutian Islands, Alaska to Southern California. A nocturnal grazer on red algae, the living animal is sometimes washed ashore after storms. In life, the eight plates of its shell are covered in a mantle.
What the authors have collected here for the reader is a museum-in-a-book. You can turn the pages almost as if you'd been let into the back rooms of Smithsonian and been allowed to open the drawers containing specimens, with Harasewych at your elbow, explaining what you're seeing. While the book is beautifully written and presented, it's so seamlessly done that nothing about the presentation gets in the way of the story of the shells.

True Heart Cockle (Corculum cardissa). 40 to 80 mm, Red Sea to Indo West Pacific. The true heart cockle can form dense colonies near coral reefs. Like the corals where it makes its home, it has a symbiotic relationship with zooxanthellae algae.

 And what stories they are. Of the Miter-Shaped Nutmeg we learn that its relatives, the cancellariids, are "known to suck the blood of sleeping fishes." Carrier shells like the Atlantic Carrier Shell cement shells, rocks, and derbis to their shells, perhaps as camouflage, perhaps as stabilization in the fine mud where they live. The Giant Owl Limpet aggressively guards an algae garden. The Common Janthina is a pelagic predator, roaming the oceans of the world on a raft of air bubbles trapped in mucus--its own bubblewrap. I know I will never look at a shell quite the same way again. It's time to go up in the attic and find the box with the childhood shell collection, and look at the shells with new eyes.

Elephant Tusk (Dentalium elephantium), 50 to 100 mm, Red Sea to Australia. This tusk shell lives buried in the sandy bottom, with only its narrow end sticking out of the surface. Some hermit crabs specialize in tusk shells.

M. G. Harasewych and Fabio Moretzsohn, The Book of Shells: A Life-Size Guide to Identifying and Classifying Six Hundred Seashells (Smithsonian/Chicago University Press, 656 pages, 2400 color plates. $55.) 

Disclosure: Science + Story received a copy of The Book of Shells from The Chicago University Press for the purpose of this review.



  1. Very groovy. You're a perfect specimen, Ann. What does it mean, "hermit crabs specialize in tusk shells?" Is that like specializing in Craftsman-style houses?

  2. Sort of! They always choose a tusk shell. I tried to find a picture of a crab in a tusk shell but couldn't find a good one.