Page images
PDF
EPUB

trated) of the larva. Spermatogenesis has been briefly described by Sharma (1943).

# in the kennel tick was studied by Stella (1938B), who "examined the course of oogenesis and spermatogenesis . . . . . from the larva to the adult (stages) ...... The gonads assume their definitive aspect and begin to function only after the last nymphal casting. The maturation with expulsion of both polar bodies occurs inside the female in the ovary. The fertile spermatozoa are formed only in the adult male and are of a unique type with flagellum and undulating membrane. The chromosomes are probably 48 in number, grouped in twelve tetrads". This paper is nicely illustrated and the reproductive organs of both sexes are described and illustrated.

Cytoplasmic inclusions in the ośgenesis of the kennel tick have been extensively reported by Das (1939), who correlated his own observations with a considerable amount of controversial conclusions by other workers.

Chromosome studies have been briefly reported by Dutt (1952).

Adult development within the nymph has been studied by YalvacTUTS39).

Excretory habits and mechanisms were investigated by Enigk and Grittner #

An "anatomical-physiological study of R. S. Ś neus" by Stella (1972) bears conclusions which I have translated freely as follows:

"(1) In the female, anatomical and histologic differentiation of most organs commences with digestion of blood; the gut develops completely and begins to function; the glands begin to activate secretion; the gonads enlarge and mature. The period of greatest functional activity corresponds nearly to the duration of the meal. Abandoning the host, the female begins oviposition, and during this period completely digests the engorged blood, thus its body, at first turgid and hard, becomes flaccid and soft. The malpighian tubules by this time are elaborating the substance

of excretion, which fills the rectal ampule, and continue elimination during deposition of eggs. The glands concerned with oviposition become active the moment it commences; thus the accessory glands of the uterus secrete a substance to facilitate the passage of the eggs to the genital aperture; the gene's organ secretes a substance which cooperates in the formation of a gluey substance. The salivary and coxal glands, the function of which is associated strictly with the digestion of blood, work afterwards at the meal, reducing and degenerating it so that by the time the female has finished oviposition hardly any traces (of ingested blood) can be found."

"(2) The young, unfed male, whose genital organs are small, shows indifference, but, differently from females, these organs mature and form sperms although the individual has not yet taken a blood meal. The gut utilizes the gross substance accumulated during the immature stage, and this is sufficient for mating, after which the individual dies. The salivary glands develop only slightly and do not secrete anticoagulin or toxin; the coxal glands do not become differentiated, and the malpighian tubules are small and in a state of repose."

"In those males that feed on blood at a certain time in their life, always after having first mated, an immediate arousing of all the physiological activities commences in those organs that, except for the gonads, have been in a torpor. The salivary glands begin functioning, as well as the coxal glands, and produce substances of agglutination and anticoagulin for the duration of the blood meal. The gut, which has completely absorbed the reserve substance, proceeds to digest the blood and the malpighian tubules send the excretory products which they have elaborated to the rectal ampule. Successively, sperm formation increases the secretory activity of the seminal vescile and of the appendage of the white gland so that a flood of viscous secretion for the dilution and nutriment of the sperm appears."

*From the examination of the anatomical and physiological results it is evident that in the male and female of R. sanguineus there exist noticeable differences in the development and period of function of the various organs," etc.

Miscellaneous

Symbiotes of the kennel tick have been noted by Cowdry (1923) and Jaschke (I933). See also Mudrow (1932).

Artificial feeding of this and other ticks by a capillary tube arrangement in order to accomplish physiological and pathogentransmission studies was described by Chabaud (1950A).

Whether host immunity is provoked by the feeding of this, and other ticks has been investigated by Brumpt and Chabaud (1947) and Chabaud (1950B), who concluded that this phenomenon does not occur when the kennel tick feeds on dogs. Guineapigs, however, react with an almost complete immunity and rabbits with a partial immunity (1950B). Infestation of guineapigs by R. s. sanguineus does not protect the host against Dermacentor pictus. The Hin: of host and kind of tick, as well as experimen methods, influence experiments of this nature, and the earlier, classical results of Trager (1939A,B,1940) should not be generalized.

IDENTIFICATION

Males, though extremely variable in many morphological characters, retain a set of certain features that are constant and differentiate them easily. (1) Posteromedian and paramedian grooves are always present and distinct; and (2) no matter how variable the general scutal punctations may be, four more or less regular rows of widely spaced punctations, always larger and most commonly somewhat deeper than all others on the scutum, can be distinguished (when the specimen is turned obliquely to the source of the light) extending from the level of the paramedian grooves to the level of the eyes.

Males vary considerably in overall size, measuring from l. 7 mm. to 4.4 mm. long, or even more. Variation among most characters, except interstitial punctation, usually can be associated with size and robustness, though, uncommonly, a large or even enormous specimen is seen with weakly chitinized features normally associated with otherwise poorly developed, runty specimens.

A typical male, measuring some 3.0 mm. long, is pale yellow, brown, or reddish brown; has a pearshaped body; slightly convex scutum; deep lateral grooves and distinct festoons; a narrowly elongate or oval but medially expanded, deep posteromedian groove; shorter and broader but equally deep paramedian grooves; very slightly convex eyes; sharply angular basis capituli; elongate, angular, adanal shields that in the posterior half of their length are usually distinctly widened and anteriorly are elongately subtriangular; and fairly distinct accessory shields.

Scutal punctations always consist of four regular or irregular rows of fairly large more or less discrete punctations, among which a variable number of small to large interstitial punctations are indiscriminately scattered.

If the specimen is engorged, the pearshape of the body is frequently exaggerated by integumental bulging laterally and posteriorly, from eye to eye, and the legs are successively larger from the anterior to the posterior pair; the posterior pairs are often massive and armed with a formidable tarsal hook ventrally.

The single character that most frequently confuses identity of this species is the density and size of interstitial punctations. The general conception of this species is one of a tick with four more or less definite rows of larger punctations among which rather few and smaller insignificant punctations are promiscuously scattered. This form (Figure 289) is found throughout northern Sudan and Egypt, but in southern Sudan occurs, to the best of our knowledge, only on larger groundfeeding birds, such as bustards and storks. In typical southern Sudan specimens, interstitial punctations are larger, deeper, and more numerous (Figure 293). If it were not for the four rows of largest punctations, one would be tempted to refer to much of this material as R. sulcatus (as, indeed, some students of African and South American ticks are doing). In central Sudan, most specimens are fairly heavily punctate. (Although we have large files of notes on variation among specimens from throughout the world, a further discussion of this matter should await a thoroughly exhaustive study).

Spiracular plates in this species are surprisingly variable. These differences appear to be often correlated with nutrition

(Cunliffe 1914A) but other factors must also be involved since the plates of Egyptian average specimens are sometimes massive.

In smaller, weaker, poorly nourished individuals, the color is either pale or darker than usual, the scutal grooves are less distinct, the adanal shields are more linear and have more rounded junctures (similar to those of R. appendiculatus), the basis capituli is more linear, the legs are # and other characters are less distinctly pronounced. However, a definite trace of the critical characters remains in all except exceedingly few, obviously misformed specimens.

Females are equally as variable as males. The above remarks concerning scutal punctations also apply to the female except that the larger punctations are less uniformly in rows but are scattered even more indefinitely over the central area of the scutum. In areas where males are lightly punctate, interstitial punctations of females are frequently more dense. The elongate scutum, normally five-sixths as wide as long, narrows acutely posterior of the eyes; halfway from the posterior margin of the eyes to the posterior angle the margin normally is obtusely angled, and at the posterior point there is a minute marginal expansion. Though difficult lucidly to describe, this slightly undulating scutal pattern forms a most distinctive picture after one has examined large series of specimens. This outline may be more generalized in poorly developed individuals, and its length-width ratio may be more equal, but it is often maintained even in runts and weak individuals. The usually pronounced lateral grooves of the scutum are additionally picked out by being inset with large punctations; they extend about three-fourths of the scutal length; though in lightly punctate specimens the lateral grooves are often less definite. In the cervical areas, shagreening or coarse punctations may occur and the scapulae usually have a group of large punctations. A Females of this species cannot be keyed in Zumpt's (1950A) revision, since the wrong section of couplet 21 applies.7

The immature stages have been described by Cunliffe (1914A), Theiler (1973E), c: (1946), Feldman-Muhsam (1952A), others noted in REMARKS, above, and in numerous other reports.

NOTE: For further references to variation, related species and subspecies, etc. , see REMARKS, above.

« PreviousContinue »