The Book of Shells: A Life-Size Guide to Identifying and Classifying Six Hundred Seashells (Life-Size Guides to the Best of Nature) - Hardcover

Harasewych, M. G.; Moretzsohn, Fabio

Hardcover

ISBN 10: 0226315770 ISBN 13: 9780226315775

Verlag: University of Chicago Press, 2010

Inhaltsangabe

Who among us hasn’t marveled at the diversity and beauty of shells? Or picked one up, held it to our ear, and then gazed in wonder at its shape and hue? Many a lifelong shell collector has cut teeth (and toes) on the beaches of the Jersey Shore, the Outer Banks, or the coasts of Sanibel Island. Some have even dived to the depths of the ocean. But most of us are not familiar with the biological origin of shells, their role in explaining evolutionary history, and the incredible variety of forms in which they come.

Shells are the external skeletons of mollusks, an ancient and diverse phylum of invertebrates that are in the earliest fossil record of multicellular life over 500 million years ago. There are over 100,000 kinds of recorded mollusks, and some estimate that there are over amillion more that have yet to be discovered. Some breathe air, others live in fresh water, but most live in the ocean. They range in size from a grain of sand to a beach ball and in weight from a few grams to several hundred pounds. And in this lavishly illustrated volume, they finally get their full due.

The Book of Shells offers a visually stunning and scientifically engaging guide to six hundred of the most intriguing mollusk shells, each chosen to convey the range of shapes and sizes that occur across a range of species. Each shell is reproduced here at its actual size, in full color, and is accompanied by an explanation of the shell’s range, distribution, abundance, habitat, and operculum—the piece that protects the mollusk when it’s in the shell. Brief scientific and historical accounts of each shell and related species include fun-filled facts and anecdotes that broaden its portrait.

The Matchless Cone, for instance, or Conus cedonulli, was one of the rarest shells collected during the eighteenth century. So much so, in fact, that a specimen in 1796 was sold for more than six times as much as a painting by Vermeer at the same auction. But since the advent of scuba diving, this shell has become far more accessible to collectors—though not without certain risks. Some species of Conus produce venom that has caused more than thirty known human deaths.

The Zebra Nerite, the Heart Cockle, the Indian Babylon, the Junonia, the Atlantic Thorny Oyster—shells from habitats spanning the poles and the tropics, from the highest mountains to the ocean’s deepest recesses, are all on display in this definitive work.

Über diesen Titel

Über die Autorin bzw. den Autor

M. G. Harasewych

is research zoologist and curator of marine mollusks at the Department of Invertebrate Zoology at the Smithsonian Institution in Washington, D.C., which houses one of the world’s largest mollusk collections. He has discovered and described dozens of new genera and species, written widely for scientific journals and periodicals, and is the author of Shells: Jewels from theSea. Fabio Moretzsohn has a doctorate in zoology and is a researcher for the Harte Research Institute in Texas. He has discovered a few new species of mollusks and is a coauthor of the Encyclopedia of Texas Seashells

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The Book of Shells

A Life-Size Guide to Identifying and Classifying Six Hundred Seashells

By M. G. Harasewych, Fabio Moretzsohn, Coral Mula

The University of Chicago Press

Copyright © 2010 The Ivy Press Limited
All rights reserved.

ISBN: 978-0-226-31577-5

CHAPTER 1

WHAT IS A MOLLUSK?

Mollusks are among the oldest and most diverse groups of animals on the planet. Like all taxa, they are defined by their genealogy. That is to say, they have a common ancestor from which all members of the phylum Mollusca, living and extinct, are descended.

EARLY MOLLUSKS

The earliest mollusks were small (1/25–1/12 in/1–2 mm), marine, bilaterally symmetrical animals, with an anterior head, a ventral foot, and a posterior mantle cavity that contained paired gills, sensory organs called osphradia, openings of the genital and excretory organs, and the anus. The head contained a mouth with a radula, a ribbonlike feeding structure unique to mollusks that is like a flexible rasp. The foot was an elongated structure used for locomotion, and the visceral mass, situated above the foot, contained the major organ systems, including the heart, kidneys, digestive glands, and gonads. The nervous system consisted of three pairs of ganglia, one for each body region (the head, foot, and viscera). A cuticle covering the body secreted calcareous spicules or scales.

Over the course of geological time, the descendants of this common ancestor diversified and differentiated, giving rise to multiple branches, each with distinctive features and adaptations. Many of the most basal of these branches, the classes within the phylum Mollusca, diverged during the Cambrian period. Some, such as the Gastropoda, Bivalvia, and Cephalopoda, underwent significant anatomatical changes, producing combinations of features that enabled rapid exploitation of new environments. Other classes (among them the Polyplacophora, Monoplacophora, Scaphopoda) retained their basic anatomical organization; they persist to the present day, little modified and with comparatively low diversity. Mollusks are so ancient and diverse that there are few diagnostic characters that are both unique to Mollusca and ubiquitous to all its classes.

CHITONS

The chitons (Class Polyplacophora) have elongated, flattened, bilaterally symmetrical bodies covered by a shell of eight overlapping transverse plates that are surrounded by a cuticularized girdle (muscular band). The foot is long and muscular, and flanked on both sides and by a long mantle cavity that contains multiple pairs of gills (from 6 to 88). The head is reduced, lacking eyes and tentacles. Light-sensing cells that are unique to chitons pass through tiny canals in the shell plates. All chitons live in the ocean, most on rocky bottoms in fairly shallow water where they graze on algae and sponges.

GASTROVERMS

Gastroverms (Class Monoplacophora) are relatively small (1/36–1 1/2 in/0.7–37 mm), ovate, bilaterally symmetrical mollusks that have a single, conical, limpetlike shell with eight pairs of serially repeated muscle scars. They were thought to be extinct, but thirty living species have been discovered since 1957, nearly all from deepsea habitats (571–21, 289 ft/174–6,489 m), where they inhabit muddy, rocky, or gravelly bottoms. All feed on organic matter and on small animals in the sediment.

BIVALVES

Bivalves (Class Bivalvia) are the second largest class of mollusks. They have a bilaterally symmetrical body that is completely enclosed in a shell consisting of two valves (left and right) that are connected by an elastic ligament. The head is reduced, and the radula is absent. Most bivalves have a capacious mantle cavity that accommodates large gills. In addition to being a respiratory organs, they filter food particles from the water. Some primitive forms feed directly on the organic matter in fine sediments, a few specialized groups derive nutrition from symbiotic algae or bacteria, while others capture and consume small crustaceans and worms in the deep sea. Most bivalves burrow in sand or mud, some in wood, clay, or coral. Some attach to hard substrates with threadlike strands (byssus), others by cementing one of their valves. Several different groups have adapted to freshwater habitats.

SCAPHOPODS

Scaphopods or tusk shells (Class Scaphopoda) comprise a small group of about 600 living species. They have tall, bilaterally symmetrical bodies completely contained in a long, curved, tapering tubular shell that is open at both ends. Scaphopods lack eyes and gills. They burrow in soft bottoms using a foot that emerges from the larger opening. The smaller opening remains near the surface of the sediment. Scaphopods feed on microscopic organisms in the sediment, which they capture with thin, threadlike tentacles called captacula.

GASTROPODS

Gastropods or snails (Class Gastropoda) comprise the largest class of mollusks. During their larval stage, all gastropods undergo torsion, a process that twists the animal until the formerly posterior mantle cavity is rotated to a position over the head, resulting in an asymmetrical animal with a single coiled shell. Snail shells assume a variety of forms, ranging from microscopic (1/75 in/0.3 mm) to enormous (39 in/1 m). The shell of a snail may be external, internal, or entirely absent. Like bivalves, snails inhabit all marine and freshwater habitats. Unlike any other mollusks, snails developed lungs and have also colonized land environments ranging from forests to mountains to deserts. Snails may be herbivores, carnivores, parasites, filter feeders, detritivores, or even chemoautotrophs.

CEPHALOPODS

The earliest cephalopods (Class Cephalopoda) had external shells, with chambers that were interconnected by a tube that allowed them to become gas-filled and buoyant. During the course of their evolution, the vast majority of cephalopods have lost an external shell. Some, including sepia, cuttlefish, and squid have internal shells that have been reduced to various degrees; octopuses lack any shell at all. Some cephalopod lineages developed the ability to swim by undulating their fins, as well as by jet propulsion.

Cephalopods inhabit all oceans at all depths. Many live in shallow coastal areas, while others are pelagic, spending their lives swimming or drifting through the open ocean at great distances from surface, shore or bottom. Cephalopods range from 1 in (25 mm) to more than 46 ft (14 m) in length, and include both the Giant Squid and the even larger Colossal Squid, the largest known invertebrate. All are predatory, with the head and mouth surrounded by muscular, sucker-bearing tentacles that capture prey, which is then eaten with a parrotlike beak and radular teeth.

CHAPTER 2

WHAT IS A SHELL?

As broadly defined, a shell is a hard outer covering that encases certain organisms, usually for the purpose of protecting them from the environment. Many organisms, ranging from microscopic foraminifera to turtles, produce shells using a variety of materials.

HOW A SHELL FORMS

External shells composed of calcium carbonate are secreted by many invertebrate phyla, among them Cnidaria (corals), Arthropoda (crabs and barnacles), Echinodermata (sea urchins), Brachiopoda (lamp shells), and Bryozoa (moss animals), yet the term "shell" or, more specifically "seashell" almost inevitably conjures the image of the calcified external skeleton of a mollusk. These molluscan shells are the subject of this book.

The shell is secreted by the mantle (or pallium), a specialized tissue that is present...

Details zur Ausgabe

• Verlag: University of Chicago Press
• Erscheinungsdatum: 2010
• Sprache: Englisch
• ISBN 10: 0226315770
• ISBN 13: 9780226315775
• Einband: Gebundene Ausgabe
• Auflage: 1
• Anzahl der Seiten: 655
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Nicht verfügbar