FRESHWATER ISOPODS (ASELLIDAE)
OF NORTH AMERICA
U.S. Environmental Protection Agency
Office of Research and Development
Environmental Monitoring and Support Laboratory
Biological Methods Branch
Aquatic Biology Section
Cincinnati, Ohio 45268
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WATER POLLUTION CONTROL RESEARCH SERIES 18050 ELD05/72
(Second Printing)
FRESHWATER ISOPODS (ASELLIDAE) OF NORTH AMERICA
by
W. D. Williams
Department of Zoology, Monash University
Clayton, Victoria 3168
Australia
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Environmental Monitoring and Support Laboratory
Biological Methods Branch
Aquatic Biology Section
Cincinnati, Ohio 45268
September, 1976
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EPA Review Notice
This report has been reviewed by the Environmental
Protection Agency and approved for publication.
Approval does not signify that the contents neces-
sarily reflect the views and policies of the EPA,
nor does mention of trade names or commerical pro-
ducts constitute endorsement or recommendation for
use.
First printing, May, 1972
Second printing, September, 1976
ii
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FOREWORD
This manual was originally published as Identification Manual No. 7,
Biota of Freshwater Ecosystems, Water Pollution Control Research Series
18050 ELD05/72, U.S. Environmental Protection Agency. This series of
manuals was prepared to improve the quality of the data upon which
environmental decisions are based by providing biologists in the USEPA,
and other Federal, state and private agencies with improved taxonomic
guides for the identification of organisms collected in studies of
aquatic ecosystems. Other groups of invertebrates for which manuals
were prepared in this series include: brandhiuran crustaceans (Argulus),
amphipod crustaceans (Gammaridae), decapod crustaceans (Astacidae),
leeches (Hirudinea), freshwater nematodes (Nematoda), polychaete worms
(Polychaeta), freshwater planarians (Turbellaria), dryopoid beetles
(Coleoptera), freshwater clams (Sphaeriacea), and freshwater mussels
(Unionacea). The preparation of these documents was coordinated by the
Oceanography and Limnology Program, Smithsonian Institution.
The manuals in the Biota of Freshwater Ecosystems series supplement
identification manuals on the diatoms and midges prepared earlier by the
Aquatic Biology Methods Development and Standardization Program, Environ-
mental Monitoring & Support Laboratory-Cincinnati, Office of Research &
Development, U.S. Environmental Protection Agency, Cincinnati, Ohio, and
will be made available from this office. The Aquatic Biology Section is
responsible for the development, evaluation and standardization of
methods for the collection of biological field and laboratory data by
EPA regional, enforcement, and research programs engaged in inland,
estuarine, and marine water quality and permit compliance monitoring,
and other studies of the effects of pollutants on aquatic organisms,
including the phytoplankton, zooplankton, periphyton, macrophyton,
macroinvertebrates, and fish. The program addresses methods for:
sample collection; sample preparation; organism identification and
enumeration; the measurement of biomass, metabolic rates, and the bio-
accumulation and pathology of toxic substances; bioassay; and the
computerization, analysis, and interpretation of biological data.
Biological methods recommended for use in the Federal water pollution
control program are included in the manual, Biological Field and Lab-
oratory Methods for Measuring the Quality of Surface Waters and Effluents,
published by our program.
iii
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Identification manuals have also been prepared or are currently in
preparation or revision by our program for the following groups:
naidids, tubificids, leeches, crustacean zooplankton, stonefiies,
mayflies (Stenonema), centric diatoms, and blue-green algae. As com-
panions to the biological methods manual and the taxohomic keys, water
quality profiles have been developed or are in preparation for the
freshwater diatoms, blue-green algae, midges, mayflies, stonefiies,
caddisflies, and crustacean zooplankton.
Cornelius I. Weber, Ph.D.
Chief, Aquatic Biology Section
Biological Methods Branch
Environmental Monitoring & Support Laboratory
Office of Research & Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
September, 1976
iv
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ABSTRACT
A key is given to the North American genera (Aeellus and Livaeua) of
aSellid isopods. Another key is provided for the surface-living species
of Asetlus but lack of clear, published morphological distinctions in
the genus Liraeue prevents the construction of a key for that genus.
Notes on ecology, collection, preservation and identification are also
included.
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CONTENTS
Section Page
I Introduction 1
Collecting and Preservation 3
Identification 4
II Species List and Distribution 13
III Key to Genera of North American Freshwater Asellidae 17
IV Key to North American Surface-living Species of Aaellus 19
V References 43
VI Index of Scientific Names 45
vii
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FIGURES
Page
1 Dorsal view of male Aaellua aommunia and Liraeua sp. 4
2 Anterior head appendages of A. aommunia S
3 Posterior head appendages of A. aommunia 6
4 Peraeopod 1 of A. aormunia 7
5 Peraeopods 2-7 of A. aommunia 8
6 Pleopods 1 and 2 of A. communis 9
7 Pleopods 3-5, uropod and telson of A. aommunia 10
8 Dorsal view of head of Lirceue sp. and Aaellua sp. 17
9 Pleopod 3 of Liraeua sp. and Aaellua sp. 17
10 Various appendages of A. oaaidentalie 18
11 Endopod of pleopod 2 of A. oaaidentalia 20
12 Various appendages of A. latiaaudatua 21
13 Endopod of pleopod 2 of A. latiaaudatua 22
14 Endopod of pleopod 2 of A. aommunia 22
15 Various appendages of A. intermediua 23
16 Endopod of pleopod 2 of A. intermediua 24
17 Various appendages of A. attenuatue 25
18 Various appendages of A. raaovitzai raaovitzai 26
19 Endopod of pleopod 2 of A. raaovitzai raaov-itzai 27
20 Pleopod 1 of A. raaovitzai TaeovLtzai- 28
21 Various appendages of A. raaovitzai auetralie 29
22 Endopod of pleopod 2 of A. raaovitzai auetralia 30
23 Various appendages of A. forbeai 31
24 Endopod of pleopod 2 of A. forbeai 32
25 Endopod of pleopod 2 of A. forbeai 32
26 Peraeopod 1 of A. obtuaus 32
27 Various appendages of A. obtuaua 33
28 Endopod of pleopod 2 of A. obtuaua 34
29 Various appendages of A. montonua 35
30 Various appendages of A. nodulua 36
31 Various appendages of A. dentodoatylua 38
32 Various appendages of A. breviaouda brevicauda 39
33 Pleopod 2 of A. brevicauda breviaauda 40
34 Various appendages of A. aompuloeua 41
35 Endopod of pleopod 2 of A. aorupuloaua 41
36 Various appendages of A. kenki 42
viii
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TABLES
Page
1 Differences between Aeellue raoovitzai raaovitzai and A.
racovitzai auetralis 28
2 Differences between Asellua forbea-i and A. obtusus 34
3 Differences between Asellus brevicauda brevi-aauda and A.
brevieauda bivittatus 40
IX
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SECTION I
INTRODUCTION
The Asellidae are the most important surface-living freshwater isopods
in North America. The other isopod families which occur in North Ameri-
ca, Bopyridae, Sphaeromatidae (formerly Sphaeromidae), and Cirolanidae,
are much less important. The Bopyridae are parasitic forms, and the
Cirolanidae are spring or underground forms occurring in Mexico, areas
immediately to its north, and Virginia. The Sphaeromatidae, otherwise a
predominantly marine family, includes several species found in fresh to
brackish waters near the coast and in hot springs. Sphaeromatids and
cirolanids are easily recognised by their uropods which are attached
anterolaterally to the abdomen, and not, as in asellids, posteriorly or
posterolaterally. None of these additional isopod families, all of
whose representatives are only rarely or occasionally encountered in sur-
face fresh waters of North America, is considered further in this publi-
cation.
The North American fauna of the Asellidae is not well-known, but Williams
(1970) has revised the systematics of the surface-living species of
Asellus3 the principal genus, and the ecology of some asellids of known
identity has also been studied recently (e.g. Ellis, 1961, 1971; Clifford,
1966; Styron, 1968; Seidenberg, 1969).
For the purposes of this report, North American asellids are considered
to be represented by two genera, Liroeus and Asellus. Other generic
names that have been applied include Asellopsis, Moncasellus3 and
Caeoidotea. All species of these are now regarded as either species of
Li-voeus (=Asellopsisf Mancasellus') or Asellus (=Caeaidotea~). It has re-
cently been proposed (Henry and Magniez, 1968, 1970) that North American
Asellus species be divided between the genera ConaselluSj Asellus (of
restricted definition), and Pseudobaioalasellus. Of these, the first
two represent the elevation of former 'subgenera' to generic rank, and
the latter a newly proposed genus. It may well be that North American
asellids will prove to be a group that should legitimately be regarded
as representing several genera, but as the proposals of Henry and Magniez
were published before adequate taxonomic consideration had been given
surface-living species of North American asellids, and before systematic
knowledge of surface-living and underground species has been integrated,
such proposals seem decidedly premature to the present author. In order
not to perpetuate at generic level the sort of confusion that has exis-
ted in part at 'subgeneric1 level in North American asellids (see
Williams, 1970, p. 2), the most practical procedure for the moment is to
regard all North American species as referable to two genera only,
Asellus as defined by Birstein (1951, p. 51), and Liraeus. The former
contains both surface-living and underground species; species of the
latter typically live in surface waters only.
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L-irceus was revised taxonomically by Hubricht and Mackin (1949) who in-
cluded a key, but the revision is not entirely satisfactory in that con-
siderable emphasis was placed upon a number of apparently diagnostic
characters which in fact are subject to great variation and intergrada-
tion between species (Styron, 1969). The genus, according to Hubricht
and Mackin (1949), lacks the sort of singular characters provided for
Asellus by the structure of the male sexual pleopods (see below), and
species recognition is based upon the evaluation of many characters. In
the interests of providing some useful indications of the ecological and
geographical distributions of Lirceus species as described, a summary of
relevant data, abstracted mainly from Hubricht and Mackin (1949), has
been compiled and is given following the similar summary for Asellus com-
piled from Williams (1970) (see Species List and Distribution below), but
no attempt is made to provide a key for their identification here.
The ecological status of Asellus in North America is not clear. In most
of Europe, Asellus (as A. aquations L.) is characteristically present
within given sections of organically polluted rivers. Kolkwitz and Mar-
sson (1909) noted that it is one of the organisms abundant in the so-
called a-mesosaprobic polluted zone in particular but also occurs in the,
3-mesosaprobic zone (the 'a- and g-mesosaprobic zone1 proposed by
Kolkwitz and Marsson (1909) may be regarded as roughly equivalent to the
'recovery zone1 qf several American water pollution biologists), and
Hynes (1960) noted that Asellus is a member (with tubificids and chiron-
omids) of the 'pollution fauna' in the bad}y polluted zone of rivers
affected by organic wastes. Many investigators of North American pollu-
ted rivers make no reference to the genus in published accounts of results,
whereas others do indicate its occurrence in organically polluted rivers;
Bartsch (1948) and Bartsch and Ingram (1959), for example, indicated that
it is characteristic of the "zone of recovery'. In part, some of this
ecological uncertainty may be a reflection of the formerly unclear syste-
matic position of surface-living forms.
Because this key to Asellus has been prepared for use by biologists con-
cerned with investigating pollution of inland waters, only surface-living
forms are discussed. Neither this key nor the more detailed accqunt of
Williams (1970) should be regarded as definitive; undoubtedly much re-
mains to be discovered concerning the systematics of North American aselr-
lids. It is felt, nevertheless, that the key does deal with those species
that are most likely to be encountered.
North American species alone are considered, i.e. species occurring in the
United States and Canada. Asellids are known from Mexico (Cole and
Minckley, 1968), but are not considered here.
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COLLECTING AND PRESERVATION
A variety of methods may be used to collect specimens for qualitative
purposes. None requires elaborate apparatus or an involved technique;
freshwater asellids are easily-seen, macroscopic animals that are rela-
tively slow-moving, do not swim, and dwell amongst submerged vegetation
and bottom detritus. They are not conspicuous burrowers, although they
may often occur on the undersurfaces of submerged stones.
The most straightforward method is the direct removal by the investiga-
tor of small amounts of submerged vegetation or bottom material either
by hand or using a fine-meshed (scrim) dipnet or pondnet followed by the
searching of this material for specimens. If asellids occur they may be
handled by gripping the middle of their body with a pair of blunt forceps
held at right-angles to the long axis of the body. Searching may be
facilitated by placing the vegetation or other material to be examined
into a white> shallow dish or tray containing water to a depth of about
one inch. A tray normally used by the author measures 8 x 10 x 3 inches.
If the material is slightly teased apart after being placed in the tray
and is then undisturbed for a minute or so, specimens often become con-
spicuous by their slow movements amongst the material or by their move-
ment from the material towards clear areas of water in the tray. Such
specimens may also be removed by forceps, but a better, less damaging
method is to suck them gently with some water into a glass tube (diameter
about 3/8 inch) in which suction is maintained by a rubber bujb attached
to one end. A little practice on the part of the operator is required
with this tube method of handling specimens for satisfactory performance.
Asellids may also often be collected by removal of submerged stones and
the examination of their lower surfaces.
Specimens are best killed and preserved by directly placing them in 70-
80% ethyl alcohol. Transference to fresh alcohol after ^ few days is re-
commended. Care should be exercised to ensure that crowding of preserved
specimens does not occur, and that tubes are adequately labelled. The
maintenance of live specimens is not required for species identification.
It should be stressed that reasonably large collections are necessary for
adequate systematic examination since species identification (for both
Asellue and Livoeua"] is based on adult males only, and more than one
species may occur in the same collection. Lirceus and Asellus may also
occur together. It is suggested that 25 specimens be regarded as the min-
imal adequate number for one collection, although, of course, smaller
collections will often be useful also.
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IDENTIFICATION
For generic separation of Lirceus and Asellus and for species identifica-
tion of Asellus it will be necessary in using this publication to be
familiar with the conformation of and the terminology applied to at least
certain parts of the external structure of asellids. For confirmation of
species identity by reference to the original description or to a complete
description given elsewhere, a similar familiarity will be required with
regard to most of the remaining body parts. Before discussing the actual
technique of specimen examination, it is appropriate therefore to describe
briefly the morphology of a typical species. Asellus oommunis has been
selected for this purpose.
Fig. 1. A, dorsal view of male Asellus aommunis; B, dorsal view
of male Lireeus sp. Drawn from preserved specimens. Original.
a.=abdomen, h.=head, t.=thorax.
There are three major body regions, the head, thorax, and abdomen (Fig. 1),
The head and abdomen appear unsegmented, whereas the thorax is divided
into seven segments. Each region bears a number of appendages projecting
either anteriorly, posteriorly, ventrally or laterally.
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Fig. 2. A. communis: A, first antenna; B, second antenna; C, upper
lip; D, lower lip. From Williams (1970).
Anteriorly, the head bears a pair of short antennae (first antennae or
antennules) and a pair of much longer ones (second antennae or, simply,
antennae) (Fig. 2A, B). Ventrally the head bears a mouth which has an
upper (or anterior) lip or flap and a bilobed, lower (or posterior) lip
(Fig. 2C, D). Posterior to the mouth is a paired series of small
appendages used in feeding; from front to back these are respectively
the mandibles, first maxillae (or maxillules), second maxillae (or,
simply, maxillae), and maxillipeds (Fig. 3A-F). In addition the head
has a pair of small eyes; these occur dorsally, one on each side
(Figs 1A, 8B).
Each segment of the thorax is dorsoventrally flattened and bears lat-
erally a leg or peraeopod (pereiopod or pereopod); in all there are
seven pairs (Fig. 1A). There are some differences in structure between
each pair of legs, but these are not great, and only the structure of
the first pair of legs of adult males is distinctly different in that
the two most distal leg segments are expanded to form a claw-like appa-
ratus (Figs 4A,B; 5A-F). The palm of this usually bears near its mid-
point a prominent triangular projection and proximally a few tooth-like
setae (Fig. 4A). Each leg consists of six apparent segments, termed
respectively the dactylus, propodus, carpus, merus, ischium and basis
of which the dactylus is the most distal; A seventh leg segment, the
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Fig. 3. A. communis: A, left mandible; B, right mandible; C, first
maxilla; D, distal margin of outer plate of first maxilla; E, second
maxilla (dorsal surface); F, maxilliped. From Williams (1970).
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Fig. 4. A. oonvnunie: A, dactylus and palm of first peraeopod; B,
first peraeopod. From Williams (1970).
coxa, is not distinct from the thorax. Dorsally, the thorax is covered
by a tergal plate, which in the second to seventh segments is expanded
to a small lobe at each anterolateral angle. Breeding females bear
ventrally a series of flaps, oostegites, which arise from near the in-
side of the base of the anterior legs and form a brood-pouch or marsu-
pium. In non-breeding females, their place is taken by small, club-
shaped structures. In males, a pair of tube-like penes arise from the
posterior, ventral margin of the last thoracic segment; the penes pro-
ject backwards.
The abdomen is conspicuously dorsoventrally flattened. In males, five
pairs of pleopods are borne ventrally, of which the anterior two pairs
are small and serve a sexual function (Fig. 6A, B). The remaining pleo-
pod pairs (3-5, Fig. 7A-C) are large, plate-like, and serve a respira-
tory function; each of these pleopods consists of a larger, more robust
and variously setose lower plate (exopod), and a smaller, fragile, non-
setose upper (or inner) plate (endopod). In females, only four pairs
of pleopods occur (the true first pair are always absent) of which the
most anterior pair consists of small and simple triangular plates,
whilst the remaining three pairs are similar to those in males.
Of greatest importance in the identification of Aeellue species is the
structure of the first and second male pleopods, and of critical impor-
tance is the conformation and shape of the tip of the endopod of the
second pleopod; especially marked variation between species is dis-
played in the structure of the endopod tip. It is for this reason that
these appendages are discussed further below firstly for A. aommunis in
particular, and secondly, with respect to the conformation of the tip of
the endopod of the second pleopod alone, for all North American species
of Aeellus in general.
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Fig. 5. A. oommun-iSf peraeopods: A, second; B, third; C, fourth;
D, fifth; E, sixth; F, seventh. From Williams (1970).
The first pleopod of the male (Fig. 6A) consists of two segments, a basal
sympod and a distal segment. The second pleopod (Fig. 6B) consists of a
large sympod bearing distally a two-segmented exopod (outermost structure)
and an unsegmented endopod (innermost structure) (Fig. 6C). The endopod
has two laterally projecting lobes basally, inner and outer apophyses.
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From near the, distal tip of the endopod (Fig. 6D, E),projects a tube-like
cannula, whilst, the distal edge of the endopod. itself gives rise to a
rounded lobe, the caudal process. This conformation of endopod tip is
unique to A. dormunis. It, and that for other North American species of
Fig..6. A. oommunie: A, first pleopod; B, second pleopod; C, dorsal
surface of endopod of second pleopod; D,E, respectively dorsal and
ventral surfaces of tip of endopod of second pleopod. (After Williams,
1970) .
can.=cannula, c.p.=caudal process, v.g.=ventral groove.
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Fig. 7. A. oommunis: A, third pleopod; B, fourth pleopod; C, fifth
pleopod; D, uropod; E, uropod and telson. From Williams (1970).
10
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Aeellusf appears to be derivable from a structure consisting in principle
of a terminal ventral groove associated with which are four terminal ele-
ments : a mesial process arising from the medial edge of the ventral
groove; a cannula, essentially a tubular prolongation of the ventral
groove; a lateral process arising from the lateral edge of the groove;
and a terminal caudal process. Loss or modification ^f these elements,
it has been suggested, can produce the conformation unique for each species
of Asellus.
A final pair of abdominal appendages project backwards from the posterior
border of the abdomen; these appendages are the uropods. Each (Fig. 7D)
consists of a basal segment, the peduncle, and two distal segments or rami,
an inner one, the endopod, and an outer one, the exopod. The upper sur-
face of the region referred to here as the abdomen in effect constitutes
the telson, also referred to as the pleotelson (Fig. 7E).
EXAMINATION TECHNIQUE. A stereoscopic and a compound microscope, a pair
of fine forceps, a mounted needle, a petri-dish (or similar container) and
microscope slides and coverslips are equipment needed for species identifi-
cation. Preliminary examination and dissection should be made using the
stereoscopic microscope with the specimens immersed in 70-80% ethyl alcohol
and illuminated by reflected light against a dark background. Further
identification is carried out by removing appropriate appendages or body
parts, mounting these on a microscope slide in a small amount of the alco-
hol from which they were withdrawn, and examining by transmitted or re-
flected light as appropriate. Such preparations are temporary; more per-
manent ones may be made using one of several mounting reagents now com-
mercially available which do not require passage of specimen material through
a series of other reagents. The author uses "Euparol" (George Gurr Ltd.,
U.K.). Readers are warned, however, that many such mounting reagents also
include clearing agents and if their action is too severe distortion and
contraction of mounted material (particularly of the endopod tip of the
second pleopod of male Asellus specimens) may occur. It is important that
this does not happen. Readers are also warned that endopod tips of the
second pleopod of male Aeellus specimens should be viewed in a variety of
positions so that a better appreciation of the arrangement of terminal
parts is gained.
11
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SECTION II
SPECIES LIST AND DISTRIBUTION
It is stressed that our knowledge of species distributions is still in-
complete so that the notes below on this subject are to be regarded as
summaries of known distributions not actual distributions.
Genus Asellus
Asellus attenuatus Richardson, 1900. Known only from one locality,
Dismal Swamp, Virginia (see Richardson, 1901).
Asellus brevioauda brevioauda Forbes, 1876. Springs and spring-fed
streams in large but relatively restricted area of east-central
United States: Arkansas, Illinois, Kentucky, Missouri.
Asellus brevioauda bivittatus Walker, 1961. Known only from one
locality, Doe Run, a spring-fed creek in Kentucky.
Asellus aommunis Say, 1818. Creeks, rivers, ponds, lakes, reser-
voirs, occasionally in swamps. Not present in the Great Lakes.
Mainly distributed in northeastern United States and south-
eastern Canada, but has also been recorded from Colorado and
Washington, Complete list of States and Provinces: Colorado,
Maine, Maryland, Massachusetts, New Jersey, Pennsylvania,
Vermont, Washington, West Virginia; Nova Scotia, Ontario.
Asellus dentadactylus Mackin and Hubricht, 1938. Small creeks in
Arkansas and Louisiana.
Asellus forbesi Williams, 1970. Typically in temporary ponds, flood
pools, and sloughs, but also in marshes, small creeks, and
occasionally lakes. Has been collected from Lake Huron at a
depth of 15 meters. Distributed over very large area of east-
central United States and in southern Ontario. Complete list
of States and Provinces: District of Columbia, Indiana, Iowa,
Kentucky, Maryland, Michigan, Missouri, North Carolina, Ohio,
South Carolina, Virginia, West Virginia, Ontario.
Asellus intermed-ius Forbes, 1876. Typically in running waters (creeks,
streams and rivers), but also in springs, ditches, ponds, lakes.
Large area of east-central United States and southern Ontario:
Illinois, Indiana, Iowa, Kentucky, Michigan, Missouri, Wisconsin;
Ontario.
Asellus kenki Bowman, 1967. Springs and spring-fed creeks (not in
large streams and ponds) in small area near Washington, D. C.:
District of Columbia, Maryland, Pennsylvania, Virginia.
Asellus latieaudatus Williams, 1970. Small creeks and ponds in south-
eastern United States: Kentucky, Louisiana.
Asellus montanus Mackin and Hubricht, 1938. Creeks, streams, sloughs
in Arkansas and Oklahoma.
Asellus nodulus Williams, 1970. Swamps, roadside ditches, streams, and
spring outlets in Maryland.
13
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Asellus obtusus Williams, 1970. Swamps, roadside ditches, temporary ponds,
rivers, small streams in small region of southeastern United States:
Florida, Georgia, Louisiana.
Asellus occidental-is Williams, 1970. Spring-brooks, streams, rivers,
marshy edges of lakes in far northwestern United States and extreme
southwestern Canada: Oregon, Washington; British Columbia.
Asellus vaoovitzai. vacovitzai Williams, 1970. Creeks, rivers, ponds,
swamps, small lakes, and great Lakes down to 42 meters. Mainly dis-
tributed in northeastern United States and southeastern Canada, but
has also been recorded from Washington. Complete list of States
and Procinces: District of Columbia, Indiana, Maryland, Massachusetts,
Michigan, Vermont, Washington; Ontario, Quebec. It is the dominant
Great Lakes species except for Lake Michigan from where it is still
unrecorded (see Racovitza, 1920)
Asellus racowitzai. australis Williams, 1970. Creeks and rivers in south-
eastern United States: Florida, Georgia.
Asellus sarupulosus Williams, 1970. Vernal and woodland pools in West Vir-
ginia.
Genus Livceus
Liraeus aldbamae Hubricht and Mackin, 1949. Seeps and springs in Alabama.
L-irceus bicuspidatus Hubricht and Mackin, 1949. Springs, seeps, creeks,
and streams in Arkansas.
L-irceus bidentatus Hubricht and Mackin, 1949. Known only from a seep in
Arkansas.
Lirceus bvachyurus (Harger, 1876). Springs and small streams of Atlan-
tic drainage from northeastern Pennsylvania to northern Virginia:
Pennsylvania, Virginia.
Liraeus fontinalis Rafinesque, 1820. Typically in springs but also in
drain outlets, seeps and streams: Georgia, Illinois, Indiana, Ken-
tucky, Ohio, Tennessee.
Liraeus garmani Hubricht and Mackin, 1949. Springs, seeps, creeks,
streams (sometimes temporary) and ponds (also sometimes temporary)
in Arkansas, Kansas, Missouri, Oklahoma.
Liraeus hargeri Hubricht and Mackin, 1949. Springs in Tennessee and
Virginia.
Lirceus hoppinae hoppinae (Faxon, 1889) . Springs in Missouri (see
Carman, 1889).
Liraeus hoppinae ozarkensis Hubricht and Mackin, 1949. Springs and
sometimes streams in Missouri and northern Arkansas.
Lirceus hopp-inae ouaahitaensis (Mackin and Hubricht, 1938). River tri-
butaries in Oklahoma.
Liraeus lineatus (Say, 1818). Rivers, creeks, sloughs, swamps, lakes
including Great Lakes. Distributed in Great Lakes region and
southeastern United States from Virginia to Florida and Alabama.
Complete list of States and Provinces: Alabama, Florida, Georgia,
Illinois, Indiana, Michigan, New York, South Carolina, Tennessee,
Virginia; Ontario.
14
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Liraeus louisianae (Mackin and Hubricht, 1938). Spring-fed marshes,
temporary pools, sloughs, roadside ditches, small streams, seeps:
Arkansas, Illinois, Louisiana, Missouri.
Lirceue megapodus Hubricht and Mackin, 1949. Springs in Missouri.
Lirceue richardeonae Hubricht and Mackin, 1949. Known only from a drain
outlet in Ohio.
Lirceus trilobus Hubricht and Mackin, 1949. Known only from woodland
pools in Oklahoma.
15
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SECTION III
KEY TO GENERA OF NORTH AMERICAN FRESHWATER ASELLIDAE
Lateral margin of head produced to form thin plate covering or over-
hanging base of mandible, this plate frequently but not always
incised (Fig. 8A). Anterior margin of head with pointed median
protuberance (carina) between bases of antennules (Fig. 8A) .
Distal segment of exopod of pleopod 3 (outer gill operculum)
approximately hemispherical in shape, with division between it
and proximal segment running obliquely backwards from inner
distal angle (Fig. 9A): Liroeus Rafinesque
(species not identified here; see Introduction)
Lateral margin of head not produced to cover or overhang base of man-
dible (Fig. 8B). Anterior margin of head without a median protu-
berance between bases of antennules (Fig. 8B). Distal segment of
exopod of pleopod 3 (outer gill operculum) sub-quadrangular in
shape, division between it and proximal segment running approxi-
mately at right-angles to long axis of specimen and commencing
well anterior to inner distal angle of appendage (Fig. 9B):
Asellus St. Hilaire (page 19)
Fig. 8. Dorsal view of
head: A, Liroeus sp.;
B, Asellus sp. Original
ca.=carina, e.=eye.
Fig. 9. Third pleopod: A, Liroeus
sp.; B, Asellus sp. Original.
17
-------
I. p..
\
Fig. 10. A. oaoi.dentdli'8. A, dactylus and propodus of first peraeo-
pod; B, first pleopod; C, second pleopod; D, E, respectively dor-
sal and ventral surfaces of tip of endopod of second pleopod; F, uropod;
G, uropod and telson. (After Williams, 1970).
can.= cannula, l.p.= lateral process, v.g.= ventral groove.
18
-------
SECTION IV
KEY TO NORTH AMERICAN SURFACE-LIVING SPECIES OF ASELLUS
The following key is of use only for adult male specimens; as indicated
in the text above, it is the males which in Asellus provide the diagnos-
tic characters for the species separation. Females cannot be identified
at present. In the key, the terms mesial process, lateral process,
caudal process, ventral groove, and cannula refer to structures at the
tip of the endopod of the second pleopod. All drawings of the first and
second pleopods, unless contraindicated, are of right pleopods. With
respect to the surface of these, ventral=anterior, and dorsal=posterior.
All principal distinguishing characters have been used in compiling the
key, and are illustrated in the accompanying figures (no direct refer-
ence may be made to such characters in the final part of the couplet for
each species). In certain cases, to aid identification some quantitative
data are given in tabular form.
1 Palm of propodus of peraeopod 1 lacking triangular process near
midpoint, but with 3-5 teeth-like spines variously arranged
(Fig. 10A). Pleopod 1 distinctly longer than pleopod 2, dis-
tal segment with numerous long plumose setae (Fig. 10B). Pleo-
pod 2 with mesial and caudal processes not developed, but lat-
eral process large, projecting beyond cannula, and distally
recurved (Figs 10D, E, 11A-E); endopod shape and relative pro-
portions of segments as in Fig. IOC. Both exopod and endopod
of uropod longer than peduncle (Fig. 10F, G): A. occidentalis
Palm of propodus of peraeopod 1 usually (not always) with both
a large triangular process near midpoint and some teeth-like
spines variously arranged. Pleopod 1 either longer than
pleopod 2 and distal segment with numerous long plumose
setae, or shorter to subequal in length to pleopod 2 and
lacking distal plumose setae. Lateral process of pleopod 2
either absent or developed in conjunction with mesial process
(i. e. not as shown in Figs 10D, E, 11A-H); endopod shape
and relative proportions of segments more or less dissimilar
to those shown in Fig. IOC. Exopod of uropod typically
shorter than peduncle, endopod usually subequal in length
to peduncle (but sometimes longer) 2
2(1) Pleopod 1 usually subequal in length to pleopod 2 or distinctly
shorter, distal segment subovate to subrectangular without
long plumose setae on distal margin but with few to numerous
short simple setae. Pleopod 2 with prominent cannula,
often wide, never hidden ventrally by lateral or mesial
processes 3
Pleopod 1 usually distinctly longer than pleopod 2, distal
segment usually subovate, often curved outward, and with
few to numerous long plumose setae on distal margin. Pleopod
2 with small, narrow cannula sometimes hidden ventrally by
lateral or mesial processes 10
19
-------
Fig. 11. A. occidental-is. Variation in morphology of tip of
endopod of second pleopod. A-E, ventral views; F-H, dorsal
views. From Williams (1970).
3(2) Pleopod 2 with neither mesial nor caudal processes developed,
only cannula projects distally from endopod tip (Figs 12D,
E, 13A-F); dorsal surface of distal end of endopod with
numerous minute comb-like structures (Fig. 12D); endopod
shape and proportion of segments as in Fig. 12C. Both rami
of uropod always flat, lanceolate and broad (Fig. 12F, G):
A. lat-Leaudatus
Caudal process of pleopod 2 always more or less developed, mesial
process either developed or not, cannula never only process
to project distally from endopod tip; dorsal surface of dis-
tal end of endopod usually lacking minute comb-like struc-
ture (if present, these extend on to caudal process); endo-
pod shape and proportions of segments more or less dissimilar
to drawings of Fig. 12C. Rami of uropod either flat, lance-
olate and broad or linear and narrow 4
4(3) Mesial process of pleopod 2 scarcely or not present 5
Mesial process of pleopod 2 present and well-developed 6
5(4) Inner and outer basal apophyses of endopod of pleopod 2 distinct
(Fig. 6B, C); caudal process usually broadly rounded, cannula
long and narrow (Figs 6D, E, 14A-M); shape of endopod and
proportions of segments as in Fig. 6B: A. oomrrtunis
Inner basal angle of endopod of pleopod 2 obtuse, sharply angled,
or produced into small, acutely pointed apophysis, outer basal
apophysis not distinct (Fig. 15C); caudal process often with
acutely pointed apex, cannula short and wide (Figs 15D, 16A-
H); shape of endopod and proportions of segments as in Fig.
15C: A. interme
-------
\
Fig. 12. A. laticaudatus. A, dactylus and propodus of first perae-
opod; B, first pleopod; C, second pleopod; D, E, respectively dor-
sal and ventral surfaces of endopod of second pleopod; F, uropod; G,
uropod and telson. (After Williams, 1970).
can.= cannuia.
21
-------
Fig. 13. A. laticaudatus.
endopod of second pleopod.
Variation in morphology of tip of
A-F, ventral views. From Williams (1970)
M
Fig. 14. A. aommunis. Variation in morphology of tip of endopod
of second pleopod. A-M, ventral views; A-K, specimens from eastern
States and southeastern Canada; L, specimen from Washington; M,
specimen from Colorado. From Williams (1970).
22
-------
Fig. 15. A. intermedius. A, dactylus and propodus of first perae-
opod; B, first pleopod; C, second pleopod; D, E, respectively dor-
sal and ventral surfaces of tip of endopod of second pleopod.
(After Williams, 1970).
can.= cannula, c.p.= caudal process, v.g.= ventral groove.
23
-------
Fig. 16. A. intermedius. Variation in morphology of tip of endo-
pod of second pleopod. A-H, ventral views. From Williams (1970).
7(6) Antenna 2 slightly longer than body. Pleopod 1 distinctly
shorter than pleopod 2, division of distal and proximal
segments incomplete (Fig. 17B). Caudal process of pleopod
2 rounded, not well-developed (but clearly present), and
lacking associated hooks and setae; cannula and subequal
mesial process extending beyond caudal process (Fig. 17D,
E); shape of endopod and proportions of segments as in
Fig. 17C. Rami of uropod linear, narrow and subequal in
length to each other (endopod only slightly longer) (Fig.
17F) : A. attenuates
Antenna 2 usually shorter than body but sometimes subequal.
Pleopod 1 subequal in length to or slightly longer than
pleopod 2, division between distal and proximal segments
more or less complete (Figs 18B, 20A-H, 21B). Caudal pro-
cess of pleopod 2 distinctly developed, large, terminating
in prominent apex, usually with several fine comb-like struc-
tures on dorsal surface and some lateral setose processes;
cannula and mesial process usually not extending distally
beyond caudal process (Figs 18D, E, 19A-J, 21D, E, 22A-F);
shape of endopod and proportions of segments more or less
dissimilar to Fig. 17C. At least endopod of uropod lanceo-
late, distinctly longer than exopod (Figs 18F, 21F)
A. Tooovitzai. 8
24
-------
Fig. 17. A. attenuatus. A, dactylus and propodus of first peraeopod;
B, first pleopod; C, second pleopod; D, E, respectively dorsal and
ventral surfaces of tip of second pleopod; F, uropod. (After Williams,
1970).
can.= cannula, m.p.= mesial process, v.g.= ventral groove.
25
-------
Fig. 18. A. racovitzai racovitzai. A, dactylus and propodus of first
peraeopod; B, first pleopod; C, second pleopod; D, E, respectively
dorsal and ventral surfaces of tip of endopod of second pleopod; F,
uropod. (After Williams, 1970).
can.= cannula, c.p.= caudal process, m.p.= mesial process, v.g.= ventral
groove.
26
-------
8(7) Distal segment of pleopod 1 more or less subrectangular (Fig.
18B). Cannula of pleopod 2 triangular in shape, not markedly
thickened on outer margin (Figs 18D, E, 19A-J); shape of end-
opod and proportions of segments as in Fig. 18C. (Table 1):
A. raoovitzai- racovitzai
Distal segment of pleopod 1 more or less subovate (Fig. 20A-H).
Cannula of pleopod 2 not conspicuously triangular in shape,
and outer margin thickened (Figs 21D, E, 22A-F); shape of
endopod and proportions of segments as in Fig. 21C. (Table 1):
A. racovitzai australis
Fig. 19. A. racovitzai racovitzai. Variation in morphology of tip of
endopod of second pleopod. A-J, ventral views; A-H, J, specimens
from eastern States and southeastern Canada; I, specimen from Washing-
ton. From Williams (1970).
27
-------
Fig. 20. A. racovitzai raaovitzai. Variation in shape of first
pleopod.
TABLE 1
SOME DIFFERENCES BETWEEN TWO SUBSPECIES OF ASELLUS RACOVlTZAI
(males only) ,
(From Williams 1970, Table 4)
length of antenna 2
body length
Pleopod 2
length of endopod
length of distal segment of exopod
Pleopod 2-distal segment of exopod
length
width
Pleopod 2 -endopod
length
width
Range
M*
± S.D.
Range
M*
± S.D.
Range
M*
± S.D.
Range
M*
+ S.D.
A. raeovitzai
racovitzai.
0.44-0.80
0.60
0.08
I.b5-1.89
1.34
0.18
0.96-2.00
1.45
0.20
2.34-3.20
2.78
0.24
A. racovitza-i
., aus traits
0.67-1.00
0.80
0.09
0.72-1.20
0.96
0*11
1.48-2.47
1.78
0.25
2.15-2.80
2.49
0.17
* difference between means highly significant in all comparisons (by "t"
test, P = < 0.001)
28
-------
Fig. 21. A. raaovitzai australis. A, dactylus and propodus of first
peraeopod; B, first pleopod; C, second pleopod; D, E, respectively
dorsal and ventral surfaces of tip of endopod of second pleopod; F,
uropod. (After Williams, 1970).
can.= cannula, c.p.= caudal process, m.p.= mesial process, v.g.=
ventral groove.
29
-------
Fig. 22. A. raeovitzai australis. Variation in morphology of tip
of endopod of second pleopod. A-F, ventral views. From Williams
(1970).
9(6) Antenna 2 usually shorter than body length. Proximal pro-
jection on palm of propodus of peraeopod 1 typically with
tooth-like seta (Fig. 23A). Mesial process of pleopod 2
usually long and not very wide; cannula of moderate width
(Figs 23D, E, 24A-G); endopod shape and/or proportions of
segments as in Figs 23C, 25A-J; proximal segment of exopod
frequently with marginal setae (Fig. 23C). Uropods mostly
subequal in length to telson. Both telson and uropods only
moderately setose laterally (Fig. 23F, G) (Table 2):
A. forbesi
Antenna 2 usually subequal in length to body. Proximal pro-
jection on palm of propodus of peraeopod 1 with long stout
seta (never a tooth-like seta) (Fig. 26). Mesial process
of pleopod 2 usually short and wide, cannula very wide with
recurved outer lip (Figs 27C, D, 28A-H); endopod shape and
proportions of segments as in Fig. 27B; proximal segment of
exopod without marginal setae (Fig. 27B). Uropods distinct-
ly longer than telson and both telson and uropods very
setose laterally (Fig. 27E) (Table 2): A. obtusus
10(2) Body of endopod and associated terminal processes of pleopod
2 arranged in spiral fashion so that 'ventral1 groove
actually lies dorsally (Fig. 29C, D, E); cannula not
visible; endopod shape and proportions of segments as in
Fig. 29C. Endopod of uropod shorter than peduncle (Fig.
29F): A. montanus
Body of endopod of pleopod 2 not spirally arranged although
some torsion may be displayed by terminal processes (i.e.
not as indicated in Fig. 29C, D, E); cannula (at least tip)
visible from ventral or dorsal view; endopod shape and
proportions of segments more or less dissimilar to Fig.
29C. Endopod of uropod typically longer than or subequal
in length to peduncle 11
30
-------
C.P.
V.g.
Fig. 23. 4. forbesi. A, dactylus and propodus of first peraeopod;
B, first pleopod; C, second pleopod; D, E, respectively dorsal and
ventral surface of tip of endopod of second pleopod; F, uropod; G,
uropod and telson. (After Williams, 1970).
can.= cannula, c.p.= caudal process, m.p.= mesial process, v.g.=
ventral groove.
31
-------
Fig. 24. A. forbesi. Variation in morphology of tip of endopod
of second pleopod. A-H, ventral views. From Williams (1970).
Fig. 25. A. forbesi. Variation in shape of endopod of second
pleopod. From Williams (1970).
Fig. 26. A. obtusus. Distal segments
of first peraeopod with dactylus and
palm of propodus shown in greater de-
tail. From Williams (1970).
32
-------
Fig. 27. A. obtueus. A, first pleopod; B, second pleopod; C, D,
respectively dorsal and ventral surfaces of endopod of second pleopod;
E, uropod and telson. (After Williams, 1970).
can.= cannula, c.p.= caudal process, m.p.= mesial process, v.g.=
ventral groove.
33
-------
H
Fig. 28. A. obtusus. Variation in morphology of tip of endopod
of second pleopod. A-H, ventral views. From Williams (1970).
TABLE 2
SOME DIFFERENCES BETWEEN TWO SPECIES OF ASELLUS (males only)
(From Williams 1970, Table 5)
Maximum body length (mm)
length of antenna 2
body length
Pleopod 2 -proximal segment
Number of marginal setae
Pleopod 2 -endopod
length
width
uropod length
telson length
Range
M*
± S.D.
of exopod
Range
M*
± S.D.
Range
M*
i S.D.
A. forbesi
18.5
0.5-1.0
0.75
0.12
0-4
1.65-2.64
2.05
0.22
0.67-1.5
1.16
0.20
A. obtusus
12.5
0.8-1.5
1.03
0.19
0
1.39-1.84
1.63
0.15
1.0-2.0
1.48
0.32
* difference between means highly significant in all comparisons (by "t"
test, P =<0.001)
34
-------
Fig. 29. A. montgnus; A, dactylus and propodus of first peraeopod;
B, first pleopod; C, second pleopod; D, E, respectively dorsal and
ventral surfaces of tip of endopod of second pleopod; F, uropod.
(After Williams, 19"?0).
'v.gf.'= 'ventral1 groove.
35
-------
v.p.'
Fig. 30. A. nodulus. A, dactylus and palm of first peraeopod; B,
first peraeopod; C, first pleopod; D, second pleopod; E, F, respec-
tively dorsal and ventral surfaces of tip of endopod of second pleopod;
G, uropod; H, uropod and telson. (After Williams, 1970).
'd.p.'= dorsal process, 'v.p.'= ventral process.
36
-------
11(10) Cannula of pleopod 2 completely enclosed between two promin-
ent, heavily sclerotized, non-dentate, broadly rounded
'ventral'and 'dorsal' processes (Fig. 30E, F); distal end
of endopod with small degree of torsion so that 'ventral1
groove lies laterally; endopod shape and proportions of
segments as in Fig. 30D. Endopod of uropod distinctly
longer than peduncle (Fig. 30G, H): A. nodulus
Cannula of pleopod 2 not enclosed between two processes as des-
cribed above (i.e. not as indicated in Fig. 30E, F); dis-
tal end of endopod not displaying any obvious sign of
torsion; ventral groove distinct; endopod shape and pro-
portions of segments more or less dissimilar to drawing
of Fig. 300. Endopod of uropod typically only slightly
longer than or subequal in length to peduncle 12
12(11) Cannula of pleopod 2 visible from ventral view, lateral pro-
cess not (or only slightly) developed, mesial process prom-
inent and bifid, caudal process wide and irregularly dentate
(Fig. 31D, E); endopod shape and proportions of segments
as in Fig. 31C: A. dentadaatylus
Cannula of pleopod 2 often hidden by lateral process in ventral
view, lateral process well-developed, mesial process prom-
inent but with either rounded or dentate distal margin (not
bifid), caudal process absent or rounded (not dentate);
endopod shape and proportions of segments more or less dis-
similar to Fig. 31C 13
13(12) Caudal process of pleopod 2 absent, distal dorsal surface of
endopod with numerous minute setae, lateral process non-
sclerotized with rounded margin, mesial process obtusely
dentate (Fig. 32C, D); endopod shape and proportions of
segments with some variation but typically as shown in
Figs 32B, 33A-G. Uropods about half as long as telson
(always<0.7), peduncle about as wide as long (Fig. 32E):
A. brevioauda bYewLaauda
[Pending a further examination of specimens, two subspecies
of A. bYevioauda have tentatively been proposed by Williams
(1970), A. bYevioauda bYevioauda Forbes, 1876, and A. bYevi-
oauda bivittatus Walker, 1961. The differences between them
are small and mainly involve slight differences in setation,
segment proportions, and number of segments in antennal fla-
gella. Table 3 details the principal differences.]
Distal endopodial processes of pleopod 2 (considered as a
whole) of shape and arrangement other than as described
for A. bYevioauda breviaauda, distal dorsal surface of
endopod lacks minute setae; endopod shape and proportions
of segments more or less dissimilar to drawings of Figs
32B, 33A-G. Uropods subequal to or slightly longer than
telson, peduncle always longer than wide 14
37
-------
Fig. 31. A. dentadaotylus. A, dactylus and propodus of first perae-
opod; B, first pleopod; C, second pleopod; D, E, respectively dor-
sal and ventral surfaces of tip of endopod of second pleopod; F,
uropod. (After Williams, 1970).
can.= cannula, c.p.= caudal process, m.p.= mesial process, v.g.=
ventral groove.
38
-------
Fig. 32. A. brevicauda brevicauda. A, first pleopod; B, second
pleopod; C, D, respectively dorsal and ventral surfaces of tip of
endopod of second pleopod; E, uropod. (After Williams, 1970).
can.= cannula, l.p.= lateral process, m.p.= mesial process, v.g.=
ventral groove.
14(13) Cannula of pleopod 2 small and narrow, lateral process pointed,
mesial process obtusely dentate, caudal process absent (Figs
34D, E, 35A-G); endopod shape and proportions of segments
as in Fig. 34C: A. scrupulosus
Cannula of pleopod 2 not small and narrow, lateral process
rounded, mesial process not dentate (but with rugose pos-
terior lobe), caudal process present, broadly rounded with
some rugosities (Fig. 36D, E); endopod shape and propor-
tions of segments as in Fig. 36C: A. kenki
39
-------
Fig. 33. A. breviaauda brevioauda. Variation in shape and pro-
portions of segments of second pleopod. From Williams (1970).
TABLE 3
PRINCIPAL DIFFERENCES BETWEEN TWO SUBSPECIES OF ASELLUS BREVICAUDA
(males only)
(From Williams 1970, Table 3)
Antenna 1
Antenna 2
Peraeopod 1
Pleopod 1
Pleopod 2
A.
Maximum body length (mm)
No. segments in flagellum
No. segments in flagellum
No. teeth-like setae on
dactylus
Triangular process near mid-
point of palm of propodus
No. coupling hooks on sympod
width , . . ,
lengtn
No. plumose setae on distal
segment
length A
width "ymp0d
No. plumose setae on distal
segment of exopod
uropod length
telson length
breviaauda
breviaauda
17.0
11-17
60-124
6-14
present
4-7
0.40-0.50
5-11
1.37-2.00
12-17
0.48-0.68
A. breviaauda
bivittatue
5.5
8-9
31-44
5-6
absent
3-4
0.50-0.62
4-6
1.25-1.60
5-10
0.36-0.44
40
-------
Fig. 34. A. scrupulosus. A, dactylus and pfopodus of first peraeopod;
B, first pleopod; C, second pleopod; D, E, respectively dorsal and ven-
tral surfaces of tip of endopod of second pleopod; F, uropod. (After
Williams, 1970).
can.= cannula, l.p.= lateral process, m.p.= mesial process, v.g.=
ventral groove.
Fig. 35. A. ecrupuloBue. Variation in morphology of endopod tip of
second pleopod. A-C, E, G, ventral views; D, F, dorsal views.
From Williams (1970).
41
-------
Fig. 36. A. keriki. A, first pleopod; B, distal margin of first
pleopod; C, second left pieopod; D, E, respectively dorsal and ventral
surfaces of tip of endopod of second left pleopod. (After Bowman, 1967)
can.= cannula, c.p.= caudal process, l.p.= lateral process, m.p.= mesial
process, v.g.= ventral groove.
42
-------
SECTION V
REFERENCES
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Works Journal* 20:292-302.
Bartsch, A. F. and W. M. Ingrain, 1959. Stream life and the pollution
environment. Public Works, 90:104-110.
Birstein, Ya. A. 1951. Freshwater Isopods (Asellota). Fauna S.S.S.B.,
7(5); 148pp.[English translation by Israel Program for Scientific
Translations, 1964]
BowMan, T. E. 1967. Asellus kenki, a new isopod crustacean from springs
in the eastern United States. Proceedings of the Biological
Society of Washington, 80:131-140. [A. kenki described]
Clifford, H. F. 1966. The ecology of invertebrates in an intermittent
stream. Investigations of Indiana Lakes and Streams, 7(2):57-98.
Cole, G. A. and W. L. Minckley, 1968. A new species of aquatic isopod
crustacean (genus Asellus] from the Pueblo plateau, central
Mexico. Proceedings of the Biological Society of Washington, 81:
775-60.
Ellis, R. J. 1961. A life-history study of Asellus intermedius Forbes.
Transactions of the American Microscopical Society, 80(1):80-102.
1971. Notes on the biology of the isopod Asellus tomalensis
Harford in an intermittent pond. Transactions of the American
Microscopical Society, 90(1):51-61. [synonym of A. occidentalis
Williams, 1970]
Forbes, S. A. 1876. List of Illinois Crustacea, with descriptions of
new species. Bulletin of the Illinois Museum of Natural History,
1:3-25. [A. brevicauda brevicauda and A. intermedius described]
Carman, S. 1889. Cave animals from southwestern Missouri. Bulletin of
the Museum of Comparative Zoology at Harvard University, 17(6):225-
39. [L. hoppinae hoppinae described by Faxon]
Harger, 0. 1876. Description of Mancasellus brachyurus, a new fresh-
water isopod. American Journal of Science and Arts, ll(3):304-5.
[L. brachyurus described]
Henry, J. -P. and G. Magniez, 1968. Sur la systematique et la biogeo-
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des Sciences, Paris, 267:87-9.
^_ 1970. Contribution a la systematique des Asellides (Crustacea
Isopoda). Annales de SpelSologie, 25(2):335-67.
Hubricht, L. and J. G. Mackin, 1949. The freshwater isopods of the
genus Lirceus (Asellota, Asellidae). American Midland Naturalist,
42(2):334-49. [L. hargeri, L. alabamae, L. richardsonae,
L. megapodus, L. hoppinae ozarkensis, L. bidentatus, L. bicuspida-
tus, L. garmani, L. trilobus described]
Hynes, H. B. N. 1960. "The biology of Polluted Waters." Liverpool Uni-
versity Press, Liverpool, 202 pp.
Kolkwitz, R. and M. Marsson, 1909. Okologie der tierische Saprobien.
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Internationale Revue der gesampten Hydrobiologie und Hydrographie,
2:126-152.
43
-------
Mackin, J. G. and L. Hubricht, 1938. Records of distribution of species
of isopods in central and southern United States, with descriptions
of four new species of Mancasellus and Asellus (Asellota, Asellidae).
American Midland Naturalist, 19:628-37. [A. dentadactylus, A. mon-
tanus, L. louisianae, L. hoppinae ouachitaensis described]
Racovitza, E. G. 1920. VII. Notes sur les isopodes. 6, Asellus
communis Say. 7, Les ple'opodes I and II des Asellides; Morpholo-
gic et development. Archives de Zoologie experimental et generale.
Notes et Revue * 58:79-115.
Rafinesque, C. S. 1820. Annual synopsis of new genera and species of
animals, plants etc. discovered in North America. Annals of Nature,
1:1-16. [L. fontinalis described]
Richardson, H. 1900. Synopses of North American invertebrates. VIII. The
Isopoda. Part II. American Naturalist, 34:295-309.
1901. Key to the isopods of the Atlantic coast of North America
with descriptions of new and little known species; Proceedings of
the United States National Museum, 23:494-579. [A. attenuatus
described]
Say, T. 1818. An account of the Crustacea of the United States. Journal
of the Academy of Natural Sciences of Philadelphia, 1:374-401, 423-33.
[4. communis, L. lineatus described]
Seidenberg, A. J. 1969. Studies on the biology of four species of fresh-
water isopods (Crustacea, Isopoda, Asellidae) in east-central Illin-
ois. Ph. D. dissertation, University of Illinois.
Styron, C. E. 1968. Ecology of two populations of an aquatic isopod,
Lirceus fontinalis Raf., Ecology, 49:629-36.
1969. Taxonomy of two populations of an aquatic isopod, Lirceus
fontinalis Raf.* American Midland Naturalist, 82:402-16.
Walker, B. A. 1961. Studies on Doe Run, Meade County, Kentucky, IV. A
new species of isopod crustacean (genus Asellus') from Kentucky.
Transactions of the American Microscopical Society, 80:385-90. [A.
brevicauda bivittatus described]
Williams, W. D. 1970. A revision of North American epigean species of
Asellus (Crustacea:Isopoda). Smithsonian Contributions to Zoology,
49:1-80. [A. racovitzai racovitzai, A. racovitzai australis, A.
forbesi, A. obtusus, A. laticaudatus, A. scrupulosus, A. nodulus,
A. occidentalis described]
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SECTION VI
INDEX OF SCIENTIFIC NAMES
alabamae (Liroeus), 14
aquatiaus (Asellus), 2
Asellidae, 1
Asellopsis, 1
Asellus, 1,2,3,4,7,11,13,17
aquatiaus , 2
attenuatus, 13,24,25
breviaauda bivittatus, 13,37,40
breviaauda, 13,37,39,40
oommunis, 4,5,6,7,8,9,10,13,20,
22
dentadaotylus, 13,37,38
forbesi, 13,30,31,32
intermedius, 13,20,23,24
kenki* 13,40,42
latioaudatus, 13,20,21,22
montanus, 13,30,35
nodulus, 13,36,37
obtusus, 14,30,32,33,34
oaoidentalis, 14,18,19,20
raoovitzai australis, 14,27,28,
29,30
raoovitzai, 14,26,27,28
sorupulosus, 14,40
attenuatus (Asellus), 13,24,25
biauspidatus (Liraeus), 14
bi-dentatus (Liraeus), 14
Bopyridae, 1
braohyurus (Liroeus)3 14
brevicauda bivittatus (Asellus), 13,
37,40
brevioccuda (Asellus)3 13,37,39,
40
Caeo-idotea., 1
Cirolanidae, 1
oommunis (Asellus), 4,5,6,7,8,9,10,
13,20,22
Conasellus, 1
dentadactylus (Asellus), 13,37,38
fontinalis (Lirceus), 14
forbesi, (Asellus), 13,30,31,32
garmccn-i (Liraeus), 14
hargeri (Liraeus), 14
hoppinae hoppinae (Liraeus), 14
ouaohitaensis (L-irceus), 14
ozarkensis (Liraeus), 14
intermedius (Asellus), 13,20,23,24
kenki, (Asellus), 13,40,42
laticaudatus (Asellus), 13,20,21,22
lineatus (Liroeua), 14
Lirceus, 1,2,3,4,14,17
alabamae, 14
biauspidatus, 14
bidentatus, 14
brachyurus, 14
fontinalis, 14
garmani, 14
hargeri, 14
'hoppinae hoppinae, 14
ouaohitaensis, 14
ozarkensis, 14
lineatus, 14
louisianae, 15
megapodus, 15
riohardsonae, 15
trilobus, 15
louisianae (Liraeus),IS
Manoasellus, 1
megapodus (Liraeus), 15
montanus (Asellus), 13,30,35
nodulus (Asellus), 13,36,37
obtusus (Asellus), 14,30,32,33,34
ooaidentalis (Asellus), 14,18,19,20
Pseudobaiaalasellus, 1
raoovitzai australis (Asellus), 13,
27,28,29,30
raoovitzai (Asellus), 13,26,27,
28
rio'hardsonae (Liraeus), 15
sarupulosus (Asellus), 14,40,41
Sphaeromatidae, 1
Sphaeromidae, 1
trilobus (Liraeus), 15
.S. GOVERNMENT PRINTING OFFICE: 1976-657-695/6121 Region No. 5-11
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