History of Protozoology

(b) Sub-order Haemosporidia. Coccidiomorpha whose zygotes are without a membrane; they show alternation both of genera tions and of hosts. They are parasites of the red blood corpuscles of mammals and birds. Many pathogenic. Important types: Plasmodium vivax, P. falciparum (the cause of ague or tertian fever in man), Plasmodium malariae (quaternary malaria), La verania malariae (tropical fever of man), Haemoproteus (various birds).

The Babesiae lie very close to the true haemosporidians but their fertilization and development are insufficiently known. They are parasites of the red blood corpuscles (intermediate hosts, ticks) and often pathogenic. Important types : Theileria parva (coastal fever of cattle in Africa), Babesia bigemma (Texas fever of cattle in America), Babesia canis (malignant jaundice of dogs).

2.

Order Gregarinidae. Telosporidia whose bodies have usually a definite individual shape. The zygote changes into a spore which contains many sporozoites.

(a) Sub-order Eugregarinaria (Gregarines). The body of the typical gregarine is made of at least two elements—the protomer ite and the deuteromerite, the latter containing the nucleus (see fig. 25) ; a third element when present is called the epimerite, and is usually developed as an attachment organ. The possession of longitudinal and circumferential myonemes is highly characteris tic ; the peculiar creeping movement described earlier is also char acteristic. The gregarines are parasites of the gut and body cavities of invertebrate animals and are for the most part harmless. They occur chiefly in insects and annelid worms, living not inside the cells but (at least in their young stages) clinging to them by the epimerite. The mature animals are usually quite freely motile. Alternation of hosts does not occur. True gregarines cannot repro duce agametically but onry sexually, as shown above. It should also be mentioned that the cysts in which the gametes are enclosed can produce processes of various forms which assist in the distri bution of the spores. Important types : Monocystis (in the semi nal vesicles of various earthworms), Gregarina blattarum (in the gut of the cockroach), Gregarina cuneata (in the gut of the larvae of the meal-bug).

(b) Sub-order Schizogregarinaria. These gregarines are transi tional forms between the true gregarines and the coccidians; the vegetative individuals are not far removed in body structure from the gregarines but can reproduce asexually like the coccidians by multiple division. Fertilization however is like that in the grega rines ; but only small numbers of gametes and spores are formed. The Schizogregarinaria flourish in various invertebrate animals, such as insects and crabs, but are for the most part innocuous. Some, such as Porospora, have an alternation of hosts. Important types: Ophryocystis (Malpighian tubules of the meal-bug), Poro spora (gut of the lobster and other crustaceans, with fertilization in mussels).

4. Class Neosporidia.

Multinucleate plasmodial Protozoa almost destitute of cell organoids; the spores are equipped with a complex polar capsule. Entirely parasitic, nutrition osmotic. No flagellate stage. Some forms show an amoeboid movement.

I.

Order Myxosporidia. The vegetative individuals are more or less formless clumps, often showing amoeboid movement ; they contain in the fully developed condition many thousands of nuclei. They are able to reproduce themselves asexually both by simple fission and by gemmation ; they can also form spores, though whether fertilization precedes this process, or follows it, we cannot say. The Myxosporidia flourish in the tissues and body cavities (such as gut and gall-bladders) of fishes and amphibians, and some are pathogenic. Important types : Myxobolus pfeifferi (cause of barbel-pest), Myxobolus neurobius (forms swellings in the brain and spinal marrow of trout and graylings), Myxidium lieberkiihnii (urinary bladder of pike; harmless).

2. Order Microsporidia. The vegetative individuals look just like those of the Myxosporidia and simply multiply asexually. The Microsporidia are all cell-parasites of various animals ; many are pathogenic for the vegetative individuals may grow to an enormous size and thus cause swellings. Important types : Glugea anomaly (in stickleback, pathogenic), Thelohania (in larvae of gnats), Nosema apis (cause of Isle of Wight disease of bees), Nosema bombycis (cause of pebrine disease of silk worms).