Adaptation of Trypanosomes.
These flagellates may exhibit power of adaptation to changes of environment, such as those due to the administration of drugs, change of host, etc. A few examples of such mutations may be briefly considered:—
(1) Blepharoplastless Trypanosomes.—T. brucei may become resistant to pyronin and oxazine. Accompanying this drug resistance is a change in morphology, namely, the loss of the blepharoplast (Werbitzki).[112] A race or strain of blepharoplastless trypanosomes may be thus produced which retains its characteristic feature after as many as 130 passages (Laveran).[113] Oxazine is the more powerful drug, and it acts directly on the blepharoplast. (Compare the natural blepharoplastless character of T. equinum.)
(2) Reference has been made on p. [93] to the experiments of Gonder, who showed that a strain of T. lewisi rendered resistant to arsenophenylglycin lost its resistance after passage through the rat louse. This is in marked contrast with the retention of drug resistance during passage by inoculation from rat to rat.
(3) T. lewisi from the blood of a rat when transferred to a snake seems largely to disappear, as very few flagellates are seen. When blood from the snake is inoculated into a clean rat, then trypanosomes reappear in the rat, but they are not all like those originally inoculated. It seems certain that, in such a case, changes in form and virulence of the trypanosome have occurred. Similar experiments were made with T. brucei from rats to adders and other animals and back to rats. Changes in the form and virulence of T. brucei occurred.
These interesting experiments were performed by Wendelstadt and Fellmer.[114]
Genus. Herpetomonas, Saville Kent, 1881.
Herpetomonas is a generic name for certain flagellates possessing a vermiform or snake-like body, a nucleus placed approximately centrally, and a blepharoplast (kinetic nucleus) near the flagellar end. There is no undulating membrane (fig. [49], a). The organisms included in this genus certainly possess one flagellum, while according to Prowazek (1904) Herpetomonas muscæ-domesticæ, the type species, possesses two flagella united by a membrane. Patton,[115] Porter[116] and others affirm, however, that the biflagellate character of H. muscæ-domesticæ (from the gut of the house-fly) is merely due to precocious division. The matter is further complicated by the generic name Leptomonas, given by Kent in 1881, to an uniflagellate organism found by Bütschli in the intestine of the Nematode worm, Trilobus gracilis. This parasite, Leptomonas bütschlii, has not yet been completely studied. Until these controversial points relating to the identity or separation of Herpetomonas and Leptomonas have been satisfactorily settled, we may retain the better known name Herpetomonas for such uniflagellate, vermiform organisms. However, the name Leptomonas, having been used by Kent two pages earlier in his book (“Manual of the Infusoria”) than Herpetomonas, would have priority if the two generic names were ultimately shown to be synonymous.
A full discussion of these interesting and important flagellates hardly comes within the purview of the present work; brief mention can only be given here to certain species.