Andreia Salvador - Fascinating Shells: An Introduction to 121 of the World’s Most Wonderful Mollusks

fascinating
SHELLS

An Introduction to 121 of the Worlds Most Wonderful Mollusks

Andreia Salvador

The University of Chicago Press

To Roberto

The University of Chicago Press, Chicago 60637

2022 by The Trustees of the Natural History Museum, London The author has asserted her right to be identified as the author of this work.

All rights reserved. No part of this book may be used or reproduced in any manner whatsoever without written permission, except in the case of brief quotations in critical articles and reviews. For more information, contact the University of Chicago Press, 1427 E. 60th St., Chicago, IL 60637.

Published 2022

Printed in China

31 30 29 28 27 26 25 24 23 22 1 2 3 4 5

ISBN-13: 978-0-226-81913-6 (cloth)

ISBN-13: 978-0-226-81981-5 (e-book)

DOI: https://doi.org/10.7208/chicago/9780226819815.001.0001

First published as Interesting Shells in 2022 by the Natural History Museum, Cromwell Road, London SW7 5BD.

Library of Congress Cataloging-in-Publication Data

Names: Salvador, Andreia, author.

Title: Fascinating shells : an introduction to 121 of the worlds most wonderful mollusks / Andreia Salvador.

Description: Chicago : The University of Chicago Press, 2022. | First published as Interesting Shells in 2022 by the Natural History Museum, London.

Identifiers: LCCN 2021025584 | ISBN 9780226819136 (cloth) | ISBN 9780226819815 (ebook)

Subjects: LCSH: Natural History Museum (London, England)Catalogs. | ShellsIdentification. | ShellsPictorial works.

Classification: LCC QL404 .S34 2022 | DDC 591.47/7dc23

LC record available at https://lccn.loc.gov/2021025584

Reproduction by Saxon Digital Services, Norfolk, UK
Printed by Toppan Leefung Printing Limited, China

The Museum

Londons Natural History Museum is not only a tourist attraction, but also a world-class research institution that employs over 300 scientists and houses many of the worlds most important taxonomic collections. The Museums mollusca collection is one of the most comprehensive and significant in the world and has over 8 million specimens. These specimens are key to telling the history of collecting, the science of taxonomy and the human desire to understand the natural world.

The author

The author is the Senior Curator of Mollusca at the Natural History Museum, London. Her interests include history of collections, voyages and expeditions in malacology. She has been collecting seashells since she was a child, and her favourite one is the mini museum of curiosities, the carrier shell.

Acknowledgements

The author would like to thank: Kevin Webb, Roberto Portela Miguez, Jonathan Ablett, Tom White, Suzanne Williams, John Taylor, Chong Chen, Graham Oliver, Manuel Malaquias, Barna Pll-Gergely, Marta Ferreira, Susana Celestino, CIEMAR and NHM Publishing.

Introduction

The beautiful shells illustrated in this book belong to one of the most diverse groups of animals, the molluscs. These are invertebrates soft-bodied animals without an internal skeleton and include snails, oysters, cuttlefishes and chitons, each with their characteristic type of shell. Most snails have a spirally coiled shell, oysters have a pair of shells called valves, cuttlefishes have an internal shell and chitons have an armour-like shell made up of eight separate pieces. But not all molluscs have shells, some, like slugs and some octopuses, do not have a shell at all.

The external shell provides protection for the soft body. It is made of calcium carbonate and a tough protein called conchiolin, which forms the shell matrix into which the calcium carbonate is deposited. These two components are secreted by the mantle, a thin layer of tissue that covers the soft parts of the body. As the animal grows, more shell is secreted by the mantle, enlarging the shell and making more space for the animal to grow.

Molluscs range in size from tiny snails less than 2 mm (0.08 in) long to giant squid, which can reach up to 13 m (43 ft) in length. They are found all over the world on land, in freshwater and in the sea, from the snowy mountains to the deserts, from the deep-sea hydrothermal vents to the jungles of the tropics and from the coral reefs to the rocky shores.

There are seven groups or classes of living molluscs. Of the groups described below, the first five are illustrated in this book.

Gastropods (snails and slugs)

This is the most diverse group of molluscs, with the largest number of species, and includes marine, terrestrial and freshwater snails and slugs. Gastropods range in size from a few millimetres to over 900 mm (35 in) in length and can be found in almost every environment on Earth.

Generally snails have spirally coiled shells, and they come in a variety of shapes, sizes, colours and patterns. Many snails can withdraw into their shells to protect themselves from predatorsor hostile environmental conditions. Some have an additional structure called an operculum that is attached to the foot and closes over the entrance to the inside of the shell like a trap door. Slugs and semislugs have a much-reduced shell, so the animal cannot withdraw inside, and in many species of slugs the only remnant of the shell is a small internal plate.

Gastropods feed using an organ called the radula, these vary in form depending on whether the gastropods are carnivores, herbivores or opportunistic scavengers. In most snails, it is a rasping tongue-like organ full of microscopic teeth that rubs food against the jaw like a cheese-grater. Some gastropods, like the cone snails, are able to actively hunt using a harpoon-shaped radula, which acts as a dart and injectsa venom that quickly paralyzes their prey.

Bivalves (clams, mussels, scallops and oysters)

The bivalves represent the second largest group of molluscs in terms of species diversity. They have two separate shells (called valves) that usually close tightly together, to encase and protect the soft body. The valves are joined together along their upper edges by a hinge, and strong muscles attached to the inner surfaces of the shell allow the animal to pull the valves together. Like the gastropods, the bivalve shell is extremely variable in size, shape and colour. Most bivalves are filter feeders that extract tiny particles of organic matter from the water in which they live.

Bivalves are aquatic animals, living in freshwater environments and throughout the oceans, from the shoreline to the deep sea. Some species attach themselves to rocks or other hard surfaces using a fine filament-like thread known as a byssus; others are free-swimming and highly mobile. They can also be found living burrowed into mud or sand, and some even bore into wood or soft rocks.

Cephalopods (octopus, squids, nautilus)

This charismatic group of molluscs includes the nautilus (the only member of this group with an exterior shell), the cuttlefish and the squid (with an internal and reduced shell, called a cuttlebone and pen, respectively), and the octopuses (the majority of species do not have a shell). They are generally fast swimmers, capable of expelling water out of the siphon at high speed in a kind of jet propulsion mechanism. The siphon is a part of the mantle tissue that is extended to form a tube. Cephalopods are carnivorous and have long tentacles, or arms, that are used to seize their prey, and powerful beak-like mouths that they use to tear their prey apart. There are about 800 living species, all of which are marine.