INTRODUCTION
Ergasilids have attracted
since late nineteenth
have
appeared,
Ergasilus
century.
large
sieboldi
number
(1931),
Wilson
Gurney
purely
species
of the genus
(1832)
(1911), Neuhaus
Halisch
Yamaguti
from pike,
and
white
has been
(1929), Markewitsch
(1940),
(1963),
which
descriptive.
Since then the parasite
(1933),
srnirnova (1962),
are
by Nordmann
fish and eel in Europe.
of many scientists
Of the many papers
is the type
was first described
redescribed by
the interest
Fryer
Yin
(1956),
(1969,1982)
and
Kabata (1979).
Neoergasilus
japonicus
(1930)
freshwater
from
japonicus.
first
fish
Yin (1956) created
differentiated
first swimming
and the
was
Formosa
the
second
swollen into a thumb-like
leg also carries
was
as
Harada
Ergasilus
by the structure
leg which in Neoergasilus
of
by
the genus Neoergasilus
it from Ergasilus
spine
N. japonicus
in
described
segment
projection.
and
of the
is more prolonged
of
its
The
exopod
is
basis of that
a triangular
further
tooth supporting both rami .
•
redescribed
in USSR (Smirnova
1962), China (Yamaguti 1963), Czechoslovakia
France (Lescher-Moutoue
1979) and Britain
(Hanek 1968),
( Mugridge
et al
1982 and Fryer 1982).
It has been known
cyclopoid
that
morphology
Ergasilidae
with
exhibit
the primitive
few but effective,
24
adaptations
for parasitism
Kabata
(Wilson
1911, Henderson
1979 and Cressey
In literature,
disputes
1927, Bauer
1983).
on identity
of ergasilid
species
appear to occupy large space of most discussions
1935a,b;
Fryer,
1969a,b,1970;
1960,1964,
Kabata,
1962,
1979
(Halisch,
1965,1968;
and
Thatcher,
Roberts,
1981a,b,1984).
Despite this, there are still no clear morphological
j~
m= ~
,f)}~J;
arguments,
on
peP~
species
insignificant features
~cjes_
.dJJJ...D
.-Mast
identification,
which
could
are
lines
of
based
the
on
be due to inaccurate
observations.
Roberts (1969a)
reported
McDaniel (1963) and E. lizae
was
E.
definitely
versicolor)
versicolor
species, which
E.
by
while
Muller
arthrosis
later
recorded
of Kelley and Allison
arthosis
recorded
nor
E. vesicolor
that
(1936)
but
described
by
(1962)
E.
elegans(=E.
was
neither
represent
by Roberts
a
E.
different
(1969b)
as E.
cerastes.
According to Cressey
very similar
to E.
and collette
arthrosis
and
(1970) E. spatulus
can
be
separated
other similar species
only by the row of spatulate
on the first
segment
endopod
of the
broad spines on the last segment
According to Burris
and Miller
25
second
is
from
spines
leg and the
of the first leg.
(1972) E. rhinos
differs
from all North American
species
of the genus Ergasilus
in
the armature of the second antenna though the same authors
acknowledge its similarity
the above
mentioned
to E. centrarchidarum
character
and
the
except in
structure
of
the
mouth appendages.
Voth and Larson
(1968) reported
in North Dakota
(USA) but when specimens
by Johnson
(1971) he claimed
According
to
considered
E.
inflation
Johnson
E. confusus
(1971)
the
were re-examined
that was E. wareaglei.
E.
centrarchidarum,
between
from the fish
first
wareaglei
except
two
could
for the
segments
of
be
spherical
the
second
antenna of the former.
Bricker et al
(1978)
chautauquaensis
According to Thatcher
E.
megaceros
segment
species is smaller
sensillum
antennae.
(1981b) E. leoporindis
of the
first
its
third
exopod
segment
is similar to
on outer seta of
and the former
and has a longer second
on
and E.
similar except for the
but it lacks the pectination
the terminal
single
that
are morphologically
length of the second
E. bryconis
reported
antenna with a
and
not
on
the
and
E.
second as in E. bryconis.
Thatcher
and
Robertson
bryconis
are
similar
(1982)
except
26
E.
that
jaraquensis
the
former
has
two
"spinules" on the third segment of the second antenna,
which are lacking in E. bryconis. Varella (1985) described
two "spinules" on the third segment of the second antenna
of E. bryconis
collected in the same locality.
Thatcher
and Robertson (1982) also claimed that while E. bryconis
has 3 setae on each caudal ramus, E. jaraquensis
2
setae on the caudal
proved that E. bryconis,
ramus. However,
has only
Varella
(1985)
like all other ergasilids, has 4
setae on each caudal ramus.
Paperna and Lahav (1971), who described E. fryeri
Tilapia
zillii,
reported
that
the
same
from
material
was
identified by Gussiev, Shul'man and Strelkov (USSR) as E.
sieboldi
(Lahav and Sarig, 1967) and that was confirmed
also by Bauer, who rechecked the same materials. Paperna
and Lahav
(1971)
admitted
identical in most
that
details
the
except
two
leg
species
which
5
are
has
3
terminal setae in E. fryeri while only 2 setae are present
in E. sieboldi.
Despite the large number of ergasilids described to date,
the
literature
contains
a
fairly
small
number
of
fragmented, sometimes confusing, reports on the life cycle
of ergasilid copepods.
centred
around
the
However, most of the dispute is
number
of
the
nauplial
According to Willson (1911) E. centrarchidarum
nauplius and two metanauplius
described the same stages
stages.
for E.
27
briani
stages.
has
one
Halisch
(1940)
while
Gurney
(1933) described
four
yin
gasterostei.
Sinergasilus
major
More recent work
naupliar
(1956)
stages
mentioned
for
five
Thersitina
stages
for
though he described only two of them.
by
Zmerzlaya
(1972) on E.
sieboldi,
Musselius (1967) and Mirzoeva (1972,1973) on S. lieni, Ben
Hassine
(1983) on E.
also
bryconis
development.
of
the
lizae
revealed
and Varella
three
stages
(1985) on E.
of
nauplial
Fryer (1978) concluded that the development
nauplii
is
very
imperfectly
known
for
ergasilid species but is probably similar in all.
most
Kabata
(1981) believed that the six nauplii of the free living
cyclopoid copepods tend to be abbreviated in parasitic
copepods and in all ergasilids only three naupliar stages
have remained.
However,
that N. japonicus
Urawa et al (1980a) confirmed
has six nauplius stages.
As far as the copepodid stages
studies have confirmed
are concerned all early
that in ergasilids so far studied
five stages exist in addition to the free living adult
cyclopoid stage (Gurney, 1933; Yin, 1956; Mirzoeva, 1972;
Zmerzlaya,
1972;
Urawa
et
al,
1980b;
Ben
Hassine
&
Raibaut, 1981; Ben Hassine, 1983 and Varella, 1985) with
the exception of Halisch (1940) who described
only four
stages for E. briani.
In view of all these discussion and arguments, bearing in
mind all previous studies on E. sieboldi and N. japonicus,
the present .study was carried using SEM
28
for the first
time
to
investigate
the
morphology
of
the
parasi tic
females in order to elicit more of the external
these
species.
criterium
in
As
the
the
morphology
taxonomy
of
1970 and Kabata
1979,1981)
more light on the taxonomy
represents
ergasilids
Harada 1930, Yin 1956, Yamaguti
anatomy of
1963, Fryer
a
major
(Wilson
1911,
1965, Robert
this study was meant
of these
genera
to shed
and hence
the
whole family.
Despite the
sieboldi
earlier
life
living stages
findings
cycle,
by
successful
in laboratory
in more detail
of the free-living
intrafamilial
morphology
stages
has
not
been
phylogenic consideration
of
during
SEM.
offer
(Kabata
taken
on E.
the
free
the course
The morphology
valuable
1976)
into
(Izawa, 1987).
29
(1972)
to study the development
using
might
relationships
rearing
conditions
of this study gave an opportunity
and morphology
Zmerzlaya
clues
as the
taxonomic
to
larval
and
MATERIAL
Females Ergasilus
AND
sieboldi
carp, rainbow trout
in Middle Thames
were
and bream
valley
Females Neoergasilus
METHODS
collected
taken
throughout
japonicus
the fins of bream taken
from
tench,
from different
the period
were
also
from Boldermere
sites
1986-1988.
collected
Lake
from
(Surrey)
in
the summer 1987.
The copepods
were
fins of the
respective
water to remove
carefully
mucus
hours at
0
4 C,
then
rinsed in distilled
washed
large
washed
cell
in
remove the glycerol,
and
specimens
stubs,
and
specimens
(3 drops
in
and transferred
were
in
for
10-15
washed
16%
in 3
glycerol
mucus.
To
were changed three times in
for 6 hours,
grades
critical
coated
24-30
buffer
sonicate
shaken
were
for
to draw out any attached
increasing
aluminium
to
and
distilled
Specimens
phosphate
Specimens
20% ethanol, shaken continuously
ethanol,
in
of Tween-80
disruptor
water
solution for 12 hours
absolute
1%
for 30 minutes
1987).
distilled
in
gills
glutaraldehyde
solution
water)
seconds (Felgenhaur,
dehydration
debris.
the
water. To remove any debris,
100 ml of distilled
changes of
fish,
buffered
were placed in a dilute
to an ultrasonic
from
host
and
fixed in 4% phosphate
removed
with
Cambridge Stereoscan-100.
30
point
gold
of
ethanol
dried,
and
followed
by
to
dry
mounted
on
viewed
with
a
1137 specimens
of
E.
sieboldi
japonicus were examined
Similarly free-living
and examined
and
218
for the external
specimens
anatomy.
31
N.
anatomy.
stages of E. sieboldi
for external
of
were prepared