Land Snails and Slugs of the Pacific Northwest

344 Pages·2013·12.989 MB·English

by  Thomas E. Burke

Land SnaiLS and SLugS
of the Pacific northweSt
the John and Shirley Byrne fund for Books on nature and
the environment provides generous support that helps make
publication of this and other oregon State university Press
books possible. the Press is grateful for this support.
Previously published with the support of this fund:
One City’s Wilderness: Portland’s Forest Park
by Marcy cottrell houle
Among Penguins: A Bird Man in Antarctica
by noah Strycker
Dragonflies and Damselflies of Oregon: A Field Guide
by cary Kerst and Steve gordon
Ellie’s Log: Exploring the Forest Where the Great Tree Fell
by Judith L. Li (illustrations by M. L. herring)
Land Snails and Slugs
of the Pacific Northwest
thoMaS e. BurKe
PhotograPhS By wiLLiaM P. Leonard
oregon State university Press corvallis
the author, photographer, and publisher gratefully acknowledge the generous
support of the u.S. Bureau of Land Management and the u.S. forest Service in
helping make possible the publication of this book.
the paper in this book meets the guidelines for permanence and durability of
the committee on Production guidelines for Book Longevity of the council on
Library resources and the minimum requirements of the american national
Standard for Permanence of Paper for Printed Library Materials Z39.48-1984.
Library of congress cataloging-in-Publication data
Burke, thomas e., 1941-
Land snails and slugs of the Pacific northwest / thomas e. Burke; photographs
by william P. Leonard.
pages cm
includes bibliographical references and index.
iSBn 978-0-87071-685-0 (alk. paper) -- iSBn 978-0-87071-686-7 (e-book)
1. Snails--northwest, Pacific--identification. 2. Slugs (Mollusks)--
northwest, Pacific--identification. i. title.
QL430.4.B876 2013
594'.317609795--dc23
2012044315
text © 2013 thomas e. Burke
Photographs © 2013 william P. Leonard
Book design by Steve connell/transgraphic
all rights reserved. first published in 2013 by oregon State university Press
Printed in china
oregon State university Press
121 the Valley Library
corvallis or 97331-4501
541-737-3166 • fax [phone]
http://osupress.oregonstate.edu
Contents
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Mollusk diversity | the importance of understanding and identifying
Mollusks | threatened Species conservation | ecological Balance
Mollusks as alternate hosts for Parasites | Mollusk ecology (habitat)
reproduction | dispersal | distribution and endemism
environmental hazards and Mortality | Predation defenses
collecting, Preparing, and Preserving | how to use this Book
nomenclature of Shell characteristics
Land Snails and Slugs of the Pacific Northwest . . . . . . . . . . . . . . . . . . . . . . . . . .31
taxonomic List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Keys to the families and genera ..........................45
SPecIeS AccouNtS
Land Snails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
Littorinidae ..........................................66
assimineidae .........................................68
Pomatiopsidae ........................................69
ellobiidae ............................................70
carychiidae ..........................................72
Succineidae ..........................................74
cionellidae (cochlicopidae) .............................88
Pupillidae ............................................95
Vertiginidae ..........................................97
Valloniidae ..........................................114
Subulinidae .........................................121
haplotrematidae .....................................122
Megomphicidae .....................................128
helicidae ...........................................132
hygromiidae ........................................135
helminthoglyptidae ..................................137
Bradybaenidae ......................................139
Polygyridae .........................................150
thysanophoridae ....................................181
oreohelicidae .......................................183
Punctidae ...........................................227
charopidae .........................................230
discidae ............................................232
helicodiscidae .......................................239
euconulidae .........................................242
gastrodontidae ......................................244
oxichilidae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .247
Pristilomatidae .......................................253
Slugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .267
Vitrinidae ...........................................268
Boettgerillidae .......................................269
Limacidae ..........................................270
agriolimacidae .......................................274
Milacidae ...........................................279
testacellidae .........................................280
arionidae ...........................................282
anadenidae .........................................289
ariolimacidae .......................................305
Binneyidae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .325
References and Literature cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .331
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .337
Acknowledgments
T. Burke
My study of the inland mollusks of the Pacific northwest over the past 35 years has
been incidental to my employment as a wildlife biologist. during that time, i have
communicated with many individuals regarding the molluscan taxa and have con-
sulted with many agency personnel and consultants regarding specific questions.
every question and every specimen sent to me has provided a learning experi-
ence. Personnel of the u.S. forest Service, u.S. Bureau of Land Management, u.S.
fish and wildlife Service, and washington department of fish and wildlife who
provided specimens and site information are too numerous to list, but i gratefully
acknowledge the contributions from each.
this work was initiated under a challenge cost-Share agreement and associ-
ated contracts with the u.S. department of the interior, Bureau of Land Manage-
ment, oregon State office, Spokane district, Spokane, washington. the continued
efforts of neal hedges and Kelli Van norman of those offices kept the project on
track, and their support is greatly appreciated.
others with whom i worked particularly closely include dr. Joseph furnish,
nancy duncan, Stephen dowlan, dr. John applegarth, roger Monthy, ted
weasma, darby hansen, Jo ellen richards, Patty garvey-darda, heather Mur-
phy, Susan Piper, tom Kogut, Mitch wainwright, Judy Murray-hoder, Brigitte
ranne, Jim Baugh, John Musser, and erik ellis. Paul hendricks provided invalu-
able information on Montana mollusks and their distribution, as well as shells
to photograph. casey richart provided information acquired through his many
invertebrate surveys and studies. My special thanks to contract administrators and
assistants on various mollusk projects: neal hedges, Barb Behan, Joan Ziegltrum,
dale Swedberg, darci rivers Pankratz, and Sarina Jepsen.
the late dr. terrence frest of deixis consultants lent his expertise in consulting
on disjunct populations and undescribed species. he and his colleague edward
Johannes provided specimens and locations for specific taxa and invaluable infor-
mation from their experience, as well as copies of many reports from their work.
Mr. Bill Leonard, whose skill and patience with the camera provided the pho-
tographs used to illustrate the species, the figures of shell characteristics, and the
7
8 Land SnaiLS and SLugS of the pacific northweSt
slugs for this work, also lent his invaluable knowledge acquired through his study
of slugs.
Special thanks are due to dr. Barry roth and dr. timothy Pearce for their
reviews of the manuscript and their many comments and suggestions for its im-
provement. i also wish to thank the academy of natural Sciences of Philadelphia
for permission to use many quotes and citations from Pilsbry’s monographs, Land
Mollusca of North America (North of Mexico).
finally, my wife carol deserves special recognition for her patience as i worked
many long days and nights and for her assistance in reviewing the manuscript. i
also thank the doctors and nurses of Providence St. Peter hospital and the re-
gional hospital for their patience and indulgence of me as for months i sat by
carol’s bed, often working on my laptop and always praying for her recovery from
leukemia and the drastic side effects of chemotherapy; thanks to god that she is
still with me.
Acknowledgments
W. Leonard
as a young man i had the incredible good fortune to take a class from acclaimed
nature photographers Larry west and John Shaw. over the past three decades
Larry has unselfishly shared macrophotography techniques that he personally pio-
neered, techniques that enabled me to make the photographs in this book. i am
likewise deeply indebted to tim Pearce, Lyle chichester, and tom wilke for gener-
ously sharing their precious time, knowledge, and technical expertise. i also thank
my friends and collecting companions Jim Baugh, casey richart, Steve herman,
Brad Moon, Kristiina ovaska, Bob Storm, Kelley Jorgensen, and Joan Ziegltrum;
and, especially, my family—Vicki, nick, and Megan, for their companionship, pa-
tience, and assistance on many road trips around the Pnw. without their support,
my contribution to this book would not have been possible. Lastly, i thank tom
Burke for opening my eyes to the diversity of mollusks in my adopted home—the
Pacific northwest.
Introduction
this work is intended as a guide for the identification of land snails and slugs of the
Pacific northwest, for use by biologists and other interested individuals who wish
to identify most species in the field or laboratory without the necessity of dissecting
the animals or sending them to a genetics laboratory. while not all species can be
positively identified without the aid of dissection or molecular analysis, with this
guide and some practice, most specimens should be recognizable to species. if a
more exact identification is required, the specimens can be forwarded to a mala-
cologist or genetics laboratory for further study. however, interested biologists and
students of nature will find a large degree of satisfaction in observing and identify-
ing these animals for themselves, and there is a definite need for such guides to
identification of the lesser-known animals.
it has long been the practice to dissect gastropods in order to determine their
phylogeny and even to confirm certain specific taxa. in today’s taxonomy, analysis
of the organism’s dna is now complementing the study of anatomy. Both of these
disciplines are important to the overall understanding of relationships between
species and other taxonomic groups, but they are best left to the specialists. in
many instances, even dna analysis fails to answer all of the questions, and current
taxonomy often uses groups of closely related clades instead of classes, orders, or
groups of species. analysis of variations in dna requires a computer to sort out
findings; thus the study is enhanced. But such necessary technology need not con-
strain the ability or the interest of the naturalist in the fieldwork of conservation.
it is hoped that this guide will be a useful tool, enabling field biologists and
other students of nature to continue working in the front lines of natural resource
management and conservation. May we never lose the fascination that led us to
these explorations, or the curiosity that continues to attract young and old alike to
these essential fields of study.
Mollusk Diversity
Mollusca is the second largest phylum of animals on earth, exceeded only by
arthropoda, which contains the insects, arachnids, crustaceans, and other groups
of jointed-legged invertebrates. Most of the better-known classes of mollusks occur
in marine environments and include such diverse groups as the polyplacophorans
9
10 Land SnaiLS and SLugS of the pacific northweSt
Land and Freshwater Mollusks of the Pacific Northwest
Phylum Mollusca
Class Bivalvia (Pelecypoda)—clams and mussels
order Heterodonta—includes Corbiculidae and Sphaeridae (asian
clams, pea clams, and fingernail clams)
order Schizodonta—includes unionidae and Margaritiferidae
(freshwater mussels)
Class Gastropoda—snails, slugs, and limpets
Subclass eugastropoda—gill-breathing aquatic snails; aperture closed
with an operculum
order neotaenioglossa—mostly marine and aquatic snails; some
salt marsh inhabitants
Subclass Pulmonata—air-breathing snails and slugs; operculum lacking
order Basommatophora—mostly aquatic snails and limpets; in this
work, one salt marsh species and one species of land snail
order Stylommatophora—land snails and slugs
(chitons), the bivalvia (clams, oysters, mussels), the scaphopods (tooth or tusk
shells), the gastropods (snails, abalones, limpets, sea slugs), and the cephalopods
(octopus, squid, cuttlefish, nautilus). although only two of these classes occupy
the aquatic and terrestrial habitats of inland north america, most people are sur-
prised at how diverse and abundant these animals are.
the two classes of inland mollusks of the Pacific northwest include four orders
of gastropoda (snails and slugs) and two of Bivalvia (freshwater mussels or clams).
our study is limited to the terrestrial gastropods, composed of land snails and slugs
that inhabit the Pacific northwest region of the united States, with four salt marsh
inhabitants from the Pacific coast also included. those four are usually considered
marine species, but inhabit areas that are not regularly inundated (see the intro-
duction to the taxonomic list for more details); they are often omitted from books
on seashells as well as from those on inland species.
for this work, the Pacific northwest is defined as the entirety of the states of
washington, oregon, and idaho, and the part of Montana west of the continental
divide. Because the ranges of many species are poorly understood, and because
extensions to the known ranges are continually being discovered, other species
are included that are not known to occur within that area but which occur near
its periphery.