4.19 Mo

ACAROLOGIA
A quarterly journal of acarology, since 1959
Publishing on all aspects of the Acari
All information:
http://www1.montpellier.inra.fr/CBGP/acarologia/
[email protected]
Acarologia is proudly non-profit,
with no page charges and free open access
Please help us maintain this system by
encouraging your institutes to subscribe to the print version of the journal
and by sending us your high quality research on the Acari.
Subscriptions: Year 2017 (Volume 57): 360 €
http://www1.montpellier.inra.fr/CBGP/acarologia/subscribe.php
Previous volumes (2010-2015): 250 € / year (4 issues)
Acarologia, CBGP, CS 30016, 34988 MONTFERRIER-sur-LEZ Cedex, France
The digitalization of Acarologia papers prior to 2000 was supported by Agropolis Fondation under
the reference ID 1500-024 through the « Investissements d’avenir » programme
(Labex Agro: ANR-10-LABX-0001-01)
Acarologia is under free license and distributed under the terms of the
Creative Commons-BY-NC-ND which permits unrestricted non-commercial use, distribution, and
reproduction in any medium, provided the original author and source are credited.
ON THE ADULT AND IMMATURE STAGES
OF MYOCOPTES MUSCULINUS (KOCH) WITH NOTES ON ITS BIOLOGY
AND CLASSIFICATION
BY
D. P. WATSON, B. Sc., lVI.R.C.V.S.
(Royal Pree Hospital School of Medicine, Biology Dept. London, W.C. r) .
INTRODUCTION.
The purpose of this paper is to describe the immature stages of M yocoptes mttscztlimts (Koch). Detailed descriptions of the male and female are also given.
·
A key is included for separation of the stages.
The original description was of the female and was given by KocH (t84o), the
male was first described by CLAPARÈDE (1868) ; other descriptions of the male and
female are given by G. CANESTRINI (1900) and TIRABOSCHI (1904), and FLYNN (1955)
has photographed the adults. The immature stages have been only partially
figured by CLAPARÈDE (1868), BERLESE (1898) and GAMBLES (1952), who figured
the larva but failed to recognize the protonymph.
lVI yocoptes mttscttlimts (Koch) is found on the la bora tory éfnd ho use mo use
{Mtts mttsctthts} in Great Britain 'and the house mouse in lVIississippii (SMITH 1955),
but not on the wild mice, Apode?mts sylvatictts, Evotomys glareoltts and lV!icrottts
hirt%s (ELTON, FoRD, BAKER and GARDNE_R, 1931). They attach to the hairs ,of the
face close to the skin and may extend to other parts of the body (shoulders, inguinal
region, tail base) : symptoms of mange, such as hair loss, skin reddening and excessive
scratching, are produced. These symptoms increase with age and debility.
In the following descriptions the length given is that of the idiosoma, the width
is measured at the base of legs IV. An average of ten individuàls was taken in
each case.
Female (Figs. r and z.) .
Length = 300 fL, breadth 136 fL·
- The female is oval and white. The dorsal propodosomal shield partly overhangs
the gnathosoma, is smooth, except for one pair of small setae, rectangular and ends
m a fine point posteriorly. The hysterosomal shield bears small roughly square
Acarologia, t. II, fasc. 3, 1960.
-plates, posterior to this the cuticle is finely striated. Laterally the striations
follow the contour of the body outline. Ventrally, beginning at the postèrior lip
of the genital aperature, there are transverse rows of backwardly-pointing spines.
/
cl,
po
_FIG. r. - Myocoptes ·musculinus (Koch), ovigid female dorsal view; d 1-d 4 (dorsals), lp (lateral
posterior), pa. (posterior anal), sc e (external SCf!.pular) setae of the idiosoma; LA G lateral
abdominal gland ; Bursa cop. bursa copulatrix.
FIG. 2. Myocoptes musculinus (Koch), female ventral view. a.s, anal setae; gs, genital
setae ; Gen. A genital aperature ; Gen. F genital folds ; Gen. S genital sense organs.
-
The setae of the, idiosoma are strong, simple and smooth, with slightly tlùc;lœned
bases. They are arranged as in figure r. The naming of the dorsal setae presented
sorne difficulty. The two setae half way along the posterior part of the boçly and
just anterior to the transverse striations are close together and in the usual d 2
'.
-337position, but owing to the arrangement and number of the other setae present; it
was not possible to designate d 2 to this pair of setae. It has, therefore, been assu- ·
med that da have migrated forwards and come to lie in the d 2 position anterior to
the lateral abdominal gland ; there is a small lp in the usual position posterior to
the gland. d 1 and d 2 are rather lateral in position and are found at the bases of
legs III and IV respectively. Very small sub-terminal d 4 setae are present. d 1
and d 2 are approximately half the length of sc e. At the hind end between da and
d 4 by careful focussing is seen th"e bursa copulatrix opening to the exterior by a subterminal aperature and leading to the ovary by a fine coiled duct. Ventrally
' .
3
·FIG. 3· - 1Vfyocoptes musculinus (Koch), right leg I of female, dorsal view. wl' w 3 , cp, a solenidia; aa, d, e, f, la, ra, wa setae; TA tarsus, TI tibia, GE genu, FE f~mur, TR trochanter.
FIG. 4· - Myocoptesm usculinus (Koch), right leg II of female, dorsal view. w 1 solenidion;
d seta.
·FIG. 5· - Myocoptes musculinus (Koch), left leg III of female, a, a diagram in the closed
position, b, drawing to show the leg partly extended, c, diagram of section with hair in position. TA, TI, GE, FE, TR segments of the leg.
fairly strong apodemes are present, each ending separately. Small cup-shaped
thickenings are found on the èpimera of the coxae of legs II, III and IV, these are
probably muscle insertions of the specialized hair-grasping legs III and IV. The
genital aperature is transverse and has two thickened lips anteriorly corresponding
in position to the paired longitudinal folds of the free-living Tyroglyphidae. On
the internai surface of the lips are rudiments of the genital sense organs ("genital
suckers "). The usual genita1 and anal setae are · present. Posterioriy the long
strong and slightly recurve.d pa setae are seen, flanked by the small sa setae.
':fhe gnathosoma is of the normal sarcoptiform pattern, consisting of simple
chelate chelicerae overhanging the fused pedipalps, and is used for prehension and
chewing of the host's superficial epidermallayers of skin. The palps of the pedipalps bear two pairs of setae, one pair being very long. The gnathosoma is movable
on the body by means of a ·n eck of soft chi tin and this is sometimes seen partially
overhanging the base of the mouthparts ventrally.
Legs I and II are simple, five jointed and end in a large lobed sucker; no claw
is present. Various setae and solenidia are present and figured (see figs. 3 and 4)
and follow closely the arrangement for Otodectes (Grandjean, 1937). The ' sensory
pit at the base of the tarsus is also present. Leg I differs fr9m that of the freeliving Tyroglyphidae in a number of r~spects. w 2 is missing, as it is in I)ermatophagoides sp., which may be parasitic or free-living. cp is shorter !han that of
leg II and is blunt-ended, in free-living forms it ends in a point. Only one cr is
present, there are usually two in free-living ones, although so~e free-living forms
for example species of Schweibea, only have one. w r occupies the position of d, so
becoming terminal as is customâry in many parasitic acarid mites ; d is present
though small. Setae u, v, p and q are missing (as in Otodectes). The remaining
setae of leg I are arranged as in Otodectes except that bais missing. The chaetotaxy
of leg II is essentially the same as that of leg I ; w r is terminal in position unlike
Otodectes and Dermatophagoides where it is nearer the base of the ,t arsus, it is longer
than w r of leg I and ends l.n a blunt hook. d is very long.
Legs III and IV are highly specialized for attachment to the hair of the host
(see fig. 5). They generally appear shorter and thicker than legs I and II, because
the terminal joints fold over the enlarged genu-femur. They are heavily sclerotised and normally held bent up against the body. Within the high lateral walls
of the gutter-shaped femur is a low hillock (fig. 5 a) bearing diagonal grooves. and
acting as a comb against which the h~ir is trapped when the tibia and tarsus are
pressed over it. The genu is gutter-shaped too and the adges of the flattened
tibia and tarsus are thickened and raised. The trochanter is ball-shaped and, by
means of three diagonal muscles, capable of movement in any direction. This
facilitates attachment to the host's haïr which when trapped is bent into a W and
very difficult to dislodge (fig. 5 b, c). There are few setae present, other setae may
have been incorporated into the comb or specialise~ lateral walls of the joints.
Male (fig. 6 and 7.)
Length
= rgr
'fL, width
= 136
fL·
The male is more heavily sclerotised than the female, its shape less liable to
distortion when pres~rved. In preserved material the idiosoma is roughly triangular, due to the fourth pair of legs being held against the body; in living material
it is roughly ovoid to globular and leg IV is held away from the body.
The idiosoma is more coarsely wrinkled thanJ.n the female and there is no hysterosomal shield. Dorsally and posterioriy ther'e is a Y-shaped chitinous thickening where the penial muscles attach. Ventrally there are no spines and tl,te
,a podemes are very strong; those of legs I and II join to give a Y-shape~ arrange-
-339
ment either side. There is no sternum. The penis is found between the fourth
pair of legs and the genital fold is horse-shoe shaped; three pairs of small genital
setae are present. The longitudinal slit anus is flanked by a pair of suckers ; the
anus of the female has well-developed lips, these are not seen in the male. At the
8
6
FIG. 6. - Myocoptes' musculinus (Koch), male dorsal view (preserved material), wa bifid seta
of tarsus.
FIG. 7· - Myocoptes musculinus (Koch), male ventral view (fresh material). Ap r, Ap 2 apodemes of legs I and II ; Ep epimeron.
FIG. 8 . - lVIyocoptes musculinus (Koch), right leg IV of male, ventral view. cr solenidion.
posterior end, the body carries a very fine translucent ventral flap which is bilobed. Eà ch lobe bears one pair of long (present in the female) recurved setae and
several pairs of small setae (see fig. 8). The dorsal shield and gnathosoma are as
m the female.
Legs I and II are unmodified and as in the female, leg III is adapted for hair
-340clasping. Leg IV is enlarged, strong and recurved. I t bears few setae and ends
in a strong claw and group of four small spines ; there is a sub-terminal solenidion,
<p (fig. 7) . Between the dorsal shield and leg I and legs I and II are found chitinous
struts, roughly triangular in outline, which are pro~ongations of the apodemes and
afford extra muscle attachment areas. The body setae generally are as for the
female, they are thicker and stronger and, due to the shorter body length, appear
longer; they are, however, approximately the length of those of the female. Only
one pair of anals is present.
·
The chaetotaxy of the legs I, II and III is as for the female, except that the
seta wa on tarsi I and II is 'bifid (fig. 6).
'
Larva (fig. g).
Length = r56 fL, width = 8o fL ·
The larva is ovoid in shape and has three pairs of legs, legs II and III are widely
separated by the bilobed humeral prominence. Dorsally there is a smooth hysterosomal shield, posteriorly and laterally are fine striations follo~ing the body
contours. Ventrally, beginning at ·the level of the transverse groove (seen by
transparency), are a number of longitudinal rows of long (twice the length of those
of the female) backw'ardly-pointing spines with broad op~n bases (fig. g). The
dorsal propodosoma shield is oval, _bears two depressions and no setae, and does not
overhang the gnathosoma, so that there is a distinct gap between the mouthparts
and the anterior edge of the shield ; there is a posterior spine on the shield. The chaetotaxy of the idiosoma is as the female, with the exception that d 4
is missing ; there is only one pair of genital setae, there are n_o genital setae in freeliving acarids. There is no genital aperature, the anus has a thickened lip, and the
usual anal setae are present. Vestiges of coxal rods (" bruststiele ") are present
on coxà I. Dorsally d 3 is nearer the end of the body than in the female, this is
also the case in free-living acarid forms. The gnathosoma is as for the female:
The chaetotaxy ·of the legs is as the female with one exception ; w 3 on -the
tarsus of leg I is missing, as it is in other larval acarids. Legs II and III resemble
1
those of the female, legs III being adapted for holding the host's hair.
Protonymph (fig. ro).
Length = r85 fL, width = rzo fL·
The protonymph is globular and six legged. It is very like the larva except ·
that the legs are roughly equidistant and corresponding to leg IV in position is a
small internai lateral prominance. The body striations are similar to the female
and there in a medial hysterosomal plate. The chaetotaxy of the idiosoma is as
the female, with the exception that two pairs of genital setae are lacking as in the
larva. The d 4 setae ·are present. The legs resemble those of the larva, w 3 being
still missing from leg I.
-
34I
9
g. - JVlyocoptes musculinus (Koch), larve ventral view. d 3 , gs setae of the idiosoma;
PS position of dorsal propodosomal shield ; CR coxal rods ; HS position of dorsal hysterosomal shield.
' propodosomal
FIG. IO. JV!yocoptes musculinus (Koch), prcitonymph dorsal view. d 4 seta; PS
shield; HS hysterosomal s):lield; P rudiment of leg IV.
FIG.
T?'itonymph (fig. rr, rz).. Length = zrz fL, width =
IJI
fL·
The tritonymph is eight legged and very like the female, but slightly more globular. The body striations are as the female, and the hysterosomal shield surface
is covèred with squarish plates. Ventrally long rows of small spines, diverging
posteriorly, occur between the coxae of legs II and III. Similar transverse rows
of spines are found between the bases of leg IV and extending backwards. At the
edges of the body these may be seen as uprisings of the cuticle (fig. rz). The
chaetotaxy of the idiosoma is as the female ; ventrally three pairs of genital setae
are present though there is no genital aperature. The apodemes are strong and
well-marked, and lend a characteristic architecture to the chitin of the idiosoma
ventrally.
The chaetotaxy of the legs is as for the female, w 3 is found on the tarsus of
)eg I for the first time during development of the stages. There is a chininous
thickening at the base of leg II (femur), n'ear the base of the seta vF.
12
Il
FIG. rr.. - 1\!Iyocoptes musculinus (Koch), tritonymph dorsal view.
,Nlyocoptes musculinus (Koch), tritonymph ventral view. gs genital setae.
FIG. 12. -
Key to the ad%lt and
I.
, 2.
J.
-
4·
-
immat~tre
stages.
With 3 pairs of legs :. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . z.
\Vith 4 pairs of legs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3·
With rectangular dorsal propodosomal shield overhanging the gnathosoma and an
internal prominence in the position of leg IV (fig. ro)...... . . . . . . . . . . . . Protonymph
With oval shield not overhanging gnathosoma and without internal prominence .....
Larva.
With 4th pair of legs strong, recurved and ending in a claw ............. ~.... Male
1
With 4t11 pair of legs short and modifi.ed into hair holding organs . .......... . . : . . 4·
\Vith transverse genital aperature ......................... ; .. -. . . . . . . . Female
Vi'ithout transverse genital aperature .... : . . . . . . . . . . . . . . . . . . . . . . . . . . . Tritonymph
. ,.
-343
Life cycle.
The life cycle is completed within fourteen days, the detailed times have not
yet been worked out. Young mice are fi.rst infected at 4 r/z days, when the mites
are found on the vibrissae. At 9 days they are scattered, when the body hairs
·have grown. Eggs (zoo X 45 fL) are laid, one at a time, by the adult females and
attached to the proximal part of the hairs of the chin of the mouse. Symptoms of
mange are more dependent on the age of the mouse and its general condition than
on the number of mites present.
C las si fication.
Myocoptes 1n%SCtûin%S (Koch) \Vas classifi.ed by VITZTHUi\'1 (1942) and BAKER
and WHARTON (1952) in the family Listrophoridae, members of which live and ding
on to the hairs of mammals, actually feed on the hair and scrape its surface (T. E.
HuGHES 1954) and_cannat leave hold of the hair. The gnathosoma is much moilified in connection with this habit. lVIyocoptes shows a greater resemblance to
Otodectes (in chaetotaxy of legs, bell-shaped suckers of legs, structure of gnathosoma,
feeding habits, bilobed posterior end of abdomen of male, presence of propodosomàl
or hysterosomal dorsal shields, absence of v i setae). It is, therefore, suggested
that it is placed in the Psoroptidae.
Acknowledgments.
l wish to thank the Co un cil of the Royal Free Hospital School of Medicine for facilities
for carrying out the work ; and Dr. A. M. HUGHES for her helpful guidance at ali stages and
especially for reading the paper and checking the drawings.
REFERENCES
BAKER (E. W.) et WHARTON (G. W.). - An Introduction to Acarology. (The Macmillan
Company, N. Y., pp. 376-378, 1952).
BERLESE (A.). No. 2. Acari. Myriop. et Séorp. Ital. Pt. XCI Padua, 18g8.
CANESTRINI (G.). Prospetto dell' Acarofauna italiana, pt. VII (Famiglia Listrophoridae,
pp. 883-901)' 1897·
CLAPARÈDE (E.). Studien an Acariden (Zeitschr. f. Wiss. Zool. 18, pp. 445-546, 1868).
ELTON (C.), FORD (E. B.), BAKER (J. R.) et GARDENER (A. D.). Health and parasites of a
wild mouse population. (Proc. Zool. Soc. London, Part 3, pp. 657-721, 15 text fig.,
1931).
EwiNG (H. E.). A Manual of External Parasites. (U. S. Bureau of Ento. MDCCCCXXIX,
1929).
FLYNN (Robert, J.). Control of Ectoparasites in Mice. (Proceedings of the Animal Care
Panel, Vol. 6, pp. 75-91, 1955).
Acarologt:a, t. II, fasc. 3, 1960.
23
-344 ,(R. Moylan). Myocoptes nu-tsculinus (Ko;h) cmd Myobia musculi (Schrank), two
species of mite· commonly parasitizing the laboratory mouse. (Brit. Vet. J. Vol. roS,
No, 6, p. rg4, rgs~.
_<-;.RANDJEAN (F.). Otodectes cynotis (Hering) et les prétendues trachées des Acaridiae. (Bull.,
Soc, zool. Fr. 62, pp. 280-290, 2 text fig., I937)·
(;RAND JEAN (F.)' La chaetotaxie des pattes chez les Acaridiàe. Bull. Soc. zool. Fr. 64, pp. so6o, 2 text fig., I939·
- /
HUGHES _(T. E.). The internat anatomy of the mite Listrophorus leuckarti (Pagenstecher
r86r). (Proc. zool. Soc. Lond. r24, pp. 239-256, r954).
KocH (C. L.). C. M. A. Deutschl. fasc. s., fig. r3 (Sarcoptes musculitius), r84o.
SMITH (William, W.). The Abundance and Distribution of the Ectoparasites of the House
Mouse in Mississippi. (J. Parasit. XLI (4r), pp. 58-62, rg55).
TIRABOSCHI (G.), Myocoptes musculinus Claparède. (Arch. P<\-rasit . .vo. 8, p. 327, rgo4).
YITZTHU1I (H. Graf.) ~ [(lassen und Ordnungen. des Tierreich . (Ed. H . G. Bronns, Leipzig,
I943).
.
.
(;AMBLES