WATER POLLUTION CONTROL RESEARCH SERIES • 18050 ELDO5/72
BIOTA OF FRESHWATER
ECOSYSTEMS
Identification
Manual
FRESHWATER
ISOPODS
(ASELUDAE)
OF NORTH
AMERICA
U.S. ENYmOHMEKWI PROTECTION AGENCY
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Biota of Freshwater Ecosystems
Identification Manual No. 7
FRESHWATER ISOPODS (ASELLIDAE) OF NORTH AMERICA
by
W. D. Williams
Department of Zoology, Monash University
Clayton, Victoria 3168
Australia
for the
ENVIRONMENTAL PROTECTION AGENCY
Project # 18050 ELD
Contract # 14-12-894
May 1972
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402 - Price $2.50
Stock Number 5501-0390
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EPA Review Notice
This report has been reviewed by the Environ-
mental Protection Agency, and approved for
publication. Approval does not signify that
the contents necessarily reflect the views
and policies of the EPA, nor does mention of
trade names or commercial products constitute
endorsement or recommendation for use.
WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes the
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Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications Branch
(Water), Research Information Division, R&M, Environmental
Protection Agency, Washington, DC 20460.
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FOREWORD
"Freshwater Isopods (Asellidae) of North America" is the
seventh of a series of identification manuals for selected
taxa of invertebrates occurring in freshwater systems. These
documents, prepared by the Oceanography and Limnology Program,
Smithsonian Institution for the Environmental Protection
Agency will contribute toward improving the quality of the
data upon which environmental decisions are based.
Additional manuals will include but not necessarily be lim-
ited to, freshwater representatives of the following groups:
amphipod crustaceans (Gammaridae), branchiuran crustaceans
(Argulus*), decapod crayfish crustaceans (Astacidae), leeches
(Hirudinea), polychaete worms (Polychaeta), freshwater plan-
arians (Turbellaria), aquatic dryopoid beetles (Dryopoidea)
and freshwater clams (Sphaeriacea).
ill
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ABSTRACT
A key is given to the North American genera (Asellus and Lirceus') of
asellid isopods. Another key is provided for the surface-living species
of Asellus but lack of clear, published morphological distinctions in
the genus L-ivoeus 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 Asellus 19
V References 43
VI Index of Scientific Names 45
VII
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FIGURES
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Dorsal view of male Asellus oomrunis and Lirceus sp.
Anterior head appendages of A. oommunis
Posterior head appendages of A. communis
Peraeopod 1 of A. oommun-is
Peraeopods 2-7 of A. aommunis
Pleopods 1 and 2 of A. communes
Pleopods 3-5, uropod and telson of A. communis
Dorsal view of head of Liroeus sp. and Asellus sp.
Pleopod 3 of Liraeus sp. and Asellus sp.
Various appendages of A. oaaidentalis
Endopod of pleopod 2 of. A. ocaidentalis
of A. latieaudatus
2 of. A. laticaudatus
of A. Gommunis
intermedius
of A. intermedius
attenuatus
raoovitzai racowitzai
raaovitzai racovitzai
racovitzai
Various appendages
Endopod of pleopod 2
Endopod of pleopod 2
Various appendages of A
Endopod of pleopod 2
Various appendages
Various appendages of A.
Endopod of pleopod 2 of A.
Pleopod 1 of A. raoovitzai
of A.
Various appendages of A. raoovitzai australis
Endopod of pleopod 2 of A. raaovitzai australis
Various appendages of A. forbesi
Endopod of pleopod 2 of A. forbesi
Endopod of pleopod 2 of A. forbesi
Peraeopod 1 of A. obtusus
Various appendages of A. obtusus
Endopod of pleopod 2 of. A. obtusus
Various appendages of A. montanus
Various
Various
appendages
appendages
of A.
of A.
Various appendages of A.
nodulus
dentadaotylus
brevicauda breviaauda
Pleopod 2 of A. brevioauda brevioauda
Various appendages of A. sorupulosus
Endopod of pleopod 2 of. A. scrupulosus
Various appendages of A. kenki
Page
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Vlll
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TABLES
Page
1 Differences between Asellus raoovitzai raoovitzai and A.
racovitzai australis 28
2 Differences between Asellus forbesi and A. obtusus 34
3 Differences between Asellus bvevloauda brevioauda and A.
bvevioauda bivittatus 40
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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, Sphaeromatldae (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
Asellus, 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 Asellops-is, Manoaselluss and
Caeci-dotea. All species of these are now regarded as either species of
LiToeus (j=Asellopsis3 Mancasellus') or Asellus (^CaeQ-tdotea). It has re-
cently been proposed (Henry and Magniez, 1968, 1970) that North American
Asellus species be divided between the genera Conasellus, 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 'subgeneric' 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 Lireeus. The former
contains both surface-living and underground species; species of the
latter typically live in surface waters only.
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Lirceus 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 Livoeus 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. aquatious 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
g-mesosaprobic zone (the 'a- and g-mesosaprobic zone' proposed by
Kolkwitz and Marsson (1909) may be regarded as roughly equivalent to the
'recovery zone' of 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 badly 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 account of
Williams (1970) should be regarded as definitive; undoubtedly much re-
mains to be discovered concerning the systematics of North American asel-
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 bulb 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 a 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
Asellus and L-irceus} is based on adult males only, and more than one
species may occur in the same collection. Liraeus 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 eommunis has been
selected for this purpose.
Fig. 1. A, dorsal view of male Asellus communis; B, dorsal view
of male Lirceus 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. aommun-Ls: 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. oommunis: 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. oomrmn-Ls: 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 Asellus 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. communis 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 Asellus in general.
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Fig. 5. A. eommuniSf 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. eommunis. It, and that for other North American species of
v. g.
D
Fig. 6. A. cormunis: 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. communis: A, third pleopod; B, fourth pleopod; C, fifth
pleopod; D, uropod; E, uropod and telson. From Williams (1970).
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Ase11us3 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 Asellus specimens should be viewed in a variety of
positions so that a better appreciation of the arrangement of terminal
parts is gained.
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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 brevieauda brevicauda Forbes, 1876. Springs and spring-fed
streams in large but relatively restricted area of east-central
United States: Arkansas, Illinois, Kentucky, Missouri.
Asellus brevicauda bivittatus Walker, 1961. Known only from one
locality, Doe Run, a spring-fed creek in Kentucky.
Asellus eorrmmis 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 dentadaatylus 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 intermedius 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 lat-Leaudatus 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.
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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 occidentalis Williams, 1970. Spring-brooks, streams, rivers,
marshy edges of lakes in far northwestern United States and extreme
southwestern Canada: Oregon, Washington; British Columbia.
Asellus racovitzai racovitzai 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 racovitzai australis Williams, 1970. Creeks and rivers in south-
eastern United States: Florida, Georgia.
Asellus scrupulosus Williams, 1970. Vernal and woodland pools in West Vir-
ginia.
Genus Lirceus
Lirceus alabamae Hubricht and Mackin, 1949. Seeps and springs in Alabama.
Lirceus bicuspidatus Hubricht and Mackin, 1949. Springs, seeps, creeks,
and streams in Arkansas.
Lirceus bidentatus Hubricht and Mackin, 1949. Known only from a seep in
Arkansas.
Lirceus brachyurus (Harger, 1876). Springs and small streams of Atlan-
tic drainage from northeastern Pennsylvania to northern Virginia:
Pennsylvania, Virginia.
Lirceus fontinalis Rafinesque, 1820. Typically in springs but also in
drain outlets, seeps and streams: Georgia, Illinois, Indiana, Ken-
tucky, Ohio, Tennessee.
Lirceus garmani Hubricht and Mackin, 1949. Springs, seeps, creeks,
streams (sometimes temporary) and ponds (also sometimes temporary)
in Arkansas, Kansas, Missouri, Oklahoma.
Lirceus hargeri Hubricht and Mackin, 1949. Springs in Tennessee and
Virginia.
Lirceus hoppinae hoppinae (Faxon, 1889). Springs in Missouri (see
Carman, 1889) .
Lirceus hoppinae ozarkensis Hubricht and Mackin, 1949. Springs and
sometimes streams in Missouri and northern Arkansas.
Lirceus hoppinae ouachitaensis (Mackin and Hubricht, 1938). River tri-
butaries in Oklahoma.
Lirceus 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.
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Lireeus louisianae (Mackin and Hubricht, 1938). Spring-fed marshes,
temporary pools, sloughs, roadside ditches, small streams, seeps:
Arkansas, Illinois, Louisiana, Missouri.
LiToeus megapodus Hubricht and Mackin, 1949. Springs in Missouri.
Liraeus riahardsonae Hubricht and Mackin, 1949. Known only from a drain
outlet in Ohio.
tr-ilobus 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) : Livaeus 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, Liraeus sp.;
B, Asellus sp. Original
ca.=carina, e.=eye.
Fig. 9. Third pleopod: A, Liroeus
sp.; B, Asellus sp. Original.
17
-------
Fig. 10. A, oooidentdlis. A, dactylus and propodus of first peraeo-
pod; B, first pleopod; C, second pleopod; D, E, respectively dar-
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. oocidentalis
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. oocidentalis. 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-ioaudatus
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. eommunis
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. i-ntermedius
6(4) Cannula of pleopod 2 long and narrow or triangular 7
Cannula of pleopod 2 relatively short and wide 9
20
-------
Fig, 12. A. lati-oaudatus. 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.= cannula.
21
-------
Fig. 13. A. latioaudatus.
endopod of second pleopod.
Variation in morphology of tip of
A-F, ventral views. From Williams (1970)
Fig. 14. A. oommun-Ls. 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. attenuatus
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. racowitzai- 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. raaovitsai raeovitsai. 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. vacovi-tza-L raoov-itza-i
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. vaaovitzai australis
Fig. 19. A. vacovitzai 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 racovitzai. Variation in shape of first
pleopod.
TABLE 1
SOME DIFFERENCES BETWEEN TWO SUBSPECIES OF ASELLUS RACOVITZAI
(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
vaeowitza-i
0.44-0.80
0.60
0.08
1.05-1.89
1.34
0.18
0.96-2.00
1.45
0.20
2.34-3.20
2.78
0.24
A. racovitzcci
australi-s
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. raoovitzai 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.
-------
Proximal pro-
with long stout
Mesial process
Fig. 22. A. racovitzai 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. fovbesi
Antenna 2 usually subequal in length to body.
jection on palm of propodus of peraeopod 1
seta (never a tooth-like seta) (Fig. 26),
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
-------
m. p.
v.g.
Fig. 23. A. 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. obtusus. 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
-------
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*
+ 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. montanus; 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).
'v.g.'= 'ventral* groove.
35
-------
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 'ventral'
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. 30D. 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, dentadaetylus
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. brewioauda brevioauda
[Pending a further examination of specimens, two subspecies
of A. bTevioauda have tentatively been proposed by Williams
(1970), A. bvevi.cau.da brevieauda Forbes, 1876, and A. brevi-
occuda 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. bvevioauda bveviaauda, 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. brewicauda brevieauda. 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. serupulosus
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. keriki.
39
-------
Fig. 33. A. brevicauda brevicauda. Variation in shape and pro-
portions of segments of second pleopod. From Williams (1970).
TABLE 3
PRINCIPAL DIFFERENCES BETWEEN TWO SUBSPECIES OF ASELLUS BEEVICAUDA
(males only)
(From Williams 1970, Table 3)
A. brevioauda A. brevioauda
brewioauda bivittatus
Antenna 1
Antenna 2
Peraeopod 1
Pleopod 1
Pleopod 2
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
length 6
No. plumose setae on distal
segment
width "^P°d
No. plumose setae on distal
segment of exopod
uropod length
telson length
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
5.5
8-9
31-44
5-6
absent
3-4
0.50-0.62
4-6
1.25-1.60
5-10
0 ^6 0 4.4
40
-------
Fig. 34. A. serupulosus. A, dactylus and propodus 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. sorupulosus. 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., kenki. A, first pleopod; B, distal margin of first
pleopod; C, second left pleopod; 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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Bartsch, A. F. and W. M. Ingram, 1959. Stream life and the pollution
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Bowman, T. E. 1967. Asellus kenki, a new isopod crustacean from springs
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Ellis, R. J. 1961. A life-history study of Asellus intermedius Forbes.
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Forbes, S. A. 1876. List of Illinois Crustacea, with descriptions of
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43
-------
Mackin, J. G. and L. Hubricht, 1938. Records of distribution of species
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of four new species of Manoasellus and Asellus (Asellota, Asellidae).
American Midland Naturalist, 19:628-37. [A. dentadactylus, A. mon-
tanus, L. louisianae, L. hoppinae ouachitaensis described]
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communis Say. 7, Les pleopodes I and II des^Asellides; Morpholo-
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Notes et Revue, 58:79-115.
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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.
[A. 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]
44
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SECTION VI
INDEX OF SCIENTIFIC NAMES
alabamae (Liroeus) 3 14 garmani (Liroeus) 3 14
aquations (Asellus) 3 2 hargeri (Liroeus) 3 14
Asellidae, 1 hoppinae hoppinae (Liroeus )3 14
Asellopsis3 1 _ ouaohitaensis (Liroeus) 3 14
Asellus, 1,2,3,4,7,11,13,17 _ ozarkensis (Liroeus), 14
_ aquatiaus, 2 intermedius (Asellus), 13,20,23,24
_ attenuatus, 13,24,25 kenki (Asellus), 13,40,42
_ brevioauda bivittatus, 13,37,40 latioaudatus (Asellus) 3 13,20,21,22
__ brevioauda, 13,37,39,40 lineatus (Liroeus), 14
_ oommunis, 4,5,6,7,8,9,10,13,20, Liroeus3 1,2,3,4,14,17
22 _ alabamae, 14
_ dentadaetylus 3 13,37,38 _ biauspidatus ^ 14
_ forbes-i, 13,30,31,32 _ bidentatus3 14
_ -inteYmedius , 13,20,23,24 _ braehyurus, 14
_ kenki-j 13,40,42 _ fontinalis, 14
_ lat-i-caudatus j 13,20,21,22 _ garman-i, 14
_ montanuSj 13,30,35 _ hargeri^ 14
_ noduluSj 13,36,37 _ hoppinae hoppinae 3 14
_ obtusus3 14,30,32,33,34 __ ouaehitaensis 3 14
_ oooidentalis 3 14,18,19,20 __ ozarkensis3 14
_ racovitzai australis3 14,27,28, _ lineatus 3 14
29,30 _ 1ouisianae3 15
__ racovitzai3 14,26,27,28 _ megapodus3 15
j 14,40 _ richardsonae 3 15
_ _
attenuatus (Asellus) 3 13,24,25 _ trilobus, 15
bicuspidatus (Livoeus) 3 14 louisianae (Liroeus) ,15
bidentatus (Liroeus )3 14 Manoasellus3 1
Bopyridae, 1 megapodus (Liroeus )3 15
braohyuvus (Liroeus )3 14 montanus (Asellus) 3 13,30,35
brevioauda bivittatus (Asellus)3 13, nodulus (Asellus)3 13,36,37
37,40 obtusus (Asellus) 3 14,30,32,33,34
_ brevioauda (Asellus), 13,37,39, oooidentalis (Asellus) 3 14,18,19,20
40 Pseudobaioalasellus 3 1
Caeoidotea3 1 raoovitzai australis (Asellus),, 13,
Cirolanidae, 1 27,28,29,30
oommunis (Asellus) 3 4,5,6,7,8,9,10, _ raoovitzai (Asellus) 3 13,26,27,
13,20,22 28
Conasellus3 1 richardsonae ( Liroeus )3 15
dentadaotylus (Asellus), 13,37,38 sorupulosus (Asellus) 3 14,40,41
fontinalis (Liroeus) 3 14 Sphaeromatidae, 1
forbesi (Asellus), 13,30,31,32 Sphaeromidae , 1
trilobus (Liroeus) 3 15
45
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
I. Report Wo.
3. Accession No.
w
4. Title BIOTA OF FRESHWATER ECOSYSTEMS IDENTIFICATION MANUAL 5. Report Date
NO. 7. Freshwater Isopods (Asellidae) of North America, 6
9. Organization Monash University,
Clayton, Victoria,
Australia
12. Sponsoring Of sanitation
IS. Supplementary Notes
8. Performing Organization
Report No.
10. P
11. Contract/Grant No.
14-12-894
'13'. Type of Report and
Period Covered
16. Abstract A key is given to- the North American genera (Asellus and Liroeus') of
asellid isopods. Another key is provided for the surface-living species
of Asellus but lack of clear, published morphological distinctions in
the genus Liroeus prevents the construction of a key for that genus.
Notes on ecology, collection, preservation and identification are also
included.
17 a. Descriptors
*Aquatic fauna, *Isopods, Distribution, Preservation,
17b.identifiers *Identification Manual, illustrated key, *Asellidae, *North America,
Species List, Collection,
lJc.CO WRR Field A Group j QA
18. Availability
19. Security Class.
(Report)
20. Security Class.
(Page)
21. No. of
Pages
22. Price
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D. C. ?Q2<»Q
Abstractor *• D- Williams
{institution Monash University, Victoria, Australia.
WRSIC 102 (REV. JUNE 1971)
4 U. S. GOVERNMENT PRINTING OFFICE : 1672 O - 468-267
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