Page images

is explained on the basis of William‘ (l923,l924.A,B) and Buxton's (l932,l933) exposition of the comparatively high humidity in sand, cracks of walls, and soil in areas that are otherwise dry. Brett's discussion and the comparison of his findings with those of Gun. liffe and of other workers, especially those of Robinson (19420) discussed on p. 137, which corroborate those of Brett, should be studied for their practical importance by anyone concerned with

Q. moubata. Since only careful and thorough research in the field as well as in the laboratory can conclusively settle the matter,

a more complete discussion of this question is hardly in order here.

[merged small][graphic][merged small]

No thorough studies of the internal anatomy and histology of _Q. moubata have been undertaken. What has been done on certain aspects of these subjects is reviewed in the following paragraphs. On the whole, workers have been content to accept Christophers' (1906) careful though still somewhat general description of the internal anatomy of O. savi i as also applicable to 0. moubata. Recently, Bugdorfer_(l§§I§ Efis provided a short account of the internal anatomy of 0. moubata and some of his excellent illustrations are reproduced-(Figures 56 to 58). However, 9. moubata deserves more specialized attention than it has thus far been accorded. These two species differ in habits, habitats, distribution, and receptivity to pathogenic organisms. It may be expected, therefore, that under their leathery shells, which also differ, significant anatomical and physiological differences remain to be demonstrated.

Internal Anatomy

The general featues of the internal anatomy of these two species are similar and Christophers' (loc. cit.) description of a dissection of 0. savi n ' as presented'beI3w: applies equally well to Q. nnubata ‘($1 own differences noted):


“Over the whole dorsum lies a fine membranous ex. pansion of tracheae and trabeculae of the fat body. Lying in this, in the median line, is the delicate tubular heart. Posteriorly, at about the junction of

the middle with the posterior third of the body, this is considerably dilated. Stripping off the expansion, the main mass of the viscera, consisting'largely of

the large dark red blood sacs of the alimentary canal, are exposed. By carefully unavelling these, the ar. rangement of long diverticula, described later, can

be made out. Lying upon the diverticula in the posts. rior portion of the body is the over , studded with developing ova. Upon either side 0 the ovary are

the coiled oviducts, and in the middle line is the large conspicuous_bII3bed spermatheca (uterus). In almost every region of the body a portion of the thin coiled mal i hian tubules will be found. Behind the sperma. theca is an opaque white organ, having very thin sac. cular walls and filled with characteristic white secretion from the malpighian tubules. This is the rectum (rectal ampulla), which in ticks serves as an excretory bladder. By displacing the diverticula from the extreme anterior portion of the body a bilobed glandular organ, the cephalic gland ( ene's or an) is displayed. Further back, the bulbous e s of t e c eliceres with radiating muscular fibres are seen. Around them will be noticed the ringlike chitinous fold at the base of the rostrum. By displacing to one side the whole of the anterior and lateral diverticula, a member of further structures are apparent. Passing in from the stigmatic (spiracular) openings is a leash of tracheal branches, of which the large anterior ventral trachea is the most conspicuous. Lying upon the origin of the first and second legs is the large racemose gland which functions as the salivar land in ticks. Lifting this gland by its posterior

ex remity, which lies on the anterior ventral trachea, an tracing it forward, the short salivary duct will be apparent entering the ringlike fold of chitin, already mentioned, immediately beneath the cheliceres. Lying partly under the salivary gland, and partly internal

to this structure is (the large, saccular coxal or an) conspicuous from the number of tracheae which suppIy it.


“By careful examination, the delicate, colorless esoph§1_s can be made out entering the lower surface of t e arge median blood sac of the alimentary canal, whilst lying behind the spermatheca is the fine hair. like termination of the sac in the rectum, To the rec.

tum can be traced the attached end of the two extremely
long malpighian tubules. To display the esophagus in
its passage from the pumping organ to the alimentary sac
it is necessary to tear away the dense mass of muscle
from which it will be seen to emerge. By seizing the
muscular mass boldly in the forceps, the unattached
entosternum surrounded with muscle will come away,
exposing the central lion, perforated by the eso-
phagus. By seizing t e us ends of the cheliceres
they may be drawn from their sheaths. Lying beneath
them is the horizontal entosclerite of the head. Beneath
this, again, is a dense mass of muscle within which lies

the chitinous pumping pharyn.

"In the male, in the position of the ovary in the
female, there is a delicate tube abundantly supplied
with trachea. On either side this is continuous with
a coiled duct much resembling the oviduct in the female.
In the middle line, much in the position of the sperma-
theca in the female, is a curious lobular organ, the
white glan ......“ (that) is pobably concerned in the
elaboration of spermatophores.

Following this, Christophers (fig. eit.) presented a more complete account of each structure a_§eneralized description of the digestive process in 0. savi n '. This should be consulted by anyone interested in the internai anatom and function of either species. Sections of Christophers' study dealing with the digestive system are abstracted below because of their relation to theingestion, development, and passage of pathogenic spirochetes and other organisms, but it is advisable first to mention more recent stdies of feeding organs and mechanism.

Feeding and Digestive Organs

The capitulum and related organs of 0. moubata have been studied in considerable detail by Bertram'(l9§9] and reviewed in relation to these organs throughout the Arachnida by Snodgrass (1948). Both papers, which also review previous studies and concepts, deserve careful study. Because of their specialized nature, a short abstract of either of these two studies hardly

does it justice. Snodgrass observes that “the exact method by which a tick bites perhaps needs more study than has been given to itm 0

According to Bertram, the capitulum of 0. moubata is es. sentially similar to that of other argasid ticks ‘see Christophers 1906 for Q. savi n i, Robinson and Davidson l9l3A,B,l9l4 for g.

rsicus, True I855 for Q. coriaceus, and Sen 1934,1935 for Q. Egolozani) although certain modifications in the eyeless tampan are either absent in other species or have not been adequately described. Bertram also differs widely from Sen in explanation of specific structures and fundamental interpretations.

The capitulum (Figures 59 and 60), situated in a depression (camerostome) of the anteroventral body surface, consists of a median hypostome flanked by a pair of four_segmented palpi and a pair of long, shaftlike chelicerae arising from a conical pro_ longation of the basis capituli. Each of these hollow appendages contains haemocoele. The hypostome is concave dorsally; ventrally it bears rows of distinctive retrograde denticles. The chelicerae distally each bear a small, triangular, articulated digit, attached by flexor and extensor muscles, with laterally directed denticles. These digits make the initial incision in the skin.

A triple sheath arrangement of no little complexity encases the chelicerae proximally. The buccal canal (i.e. wmouth“) lies between the dorsal chelicerae and the ventral hypostome; poximally it is much compressed. The size of this canal is somewhat in. creased by the medial emargination of the closely appressed cheliceral sheaths and by the dorsal groove C“guttef') of the hypostome which forms a food conduit. Extending into the center of the buccal canal is a hollow, "tongue_like process", the basal fusion of which with the hypostome forms a dorsal, blindlyaending pouch, the buccal cavity, into which a salivary duct issues at each posterolateral angle. The buccal canal opens directly into the pharynx, as one might logically assume it should, except

that previous workers have found tnat in other ticks the basal fusion of the hypostome, palpi, and dorsal conical prolongation of the basis capituli causes the pharynx to open into the floor of the buccal cavity.


basis capituli M.D.HG. expanded base of chelicera M.D.PH. buccal canal 0.P . buccal cavity P.C. . camerostome

chelicera PH. cone sheath S.CH. digit of chelicera S.CH. dorsal conical prolongation SUB.CH.P. of basis capituli TG. salivary duct TH. flange of chelicera


hood V.R. constrictor muscles of

pharynx V.S. Figure 59.


dilator of hypostomal gutter dilator muscles of pharynx

pharyngeal orifice posterior part of closed



outer sheath

inner sheath

subcheliceral plate process transverse bar formed by fusion of lateral thickenings of tongue_like process ventral rod of tongue_like process

ventral scutum in cavity of closed chamber

Longitudinal vertical section, diagrammatic Z-After Bertram (l939)J7


- 163 _


« PreviousContinue »