All known Sarcosporidia are included in a single genus Sarcocystis, Lank. (= Miescheria + Balbiania, Blanchard.) Some of the principal species are: S. miescheriana, from pigs; S. tenella, from sheep; S. bertrami, from horses; S. blanchardi, from Bovines; S. muris, from mice; S. platydactyli, from the gecko; and lastly, S. lindemanni, described from man.
4. Order—Haplosporidia. The Sporozoa included in this order are characterized by the general simplicity of their development, and by the undifferentiated character of their spores. The order includes a good many forms, whose arrangement and classification have been recently undertaken by Caullery and Mesnil (15), to whom, indeed, most of our knowledge relating to the Haplosporidia is due. The habitat of the parasites is sufficiently varied; Rotifers, Crustacea, Annelids and fishes furnishing most of the hosts. A recent addition to the list of Protozoa causing injury to man, a Haplosporidian, has been described by Minchin and Fantham (29d), who have termed the parasite Rhinosporidium, from its habitat in the nasal septum, where it produces pedunculate tumours.
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| From Minchin, in Lankester’s Treatise on Zoology, vol. Protozoa. | |
| Fig. 14.—Bertramia Asperospora (Fritsch) from the body-cavityof Brachionus. × 1040. | |
a, Young form with opaque, evenly-granulatedprotoplasmand few refringent granules;the nuclei (n) are small, andappear to be surrounded eachby a clear space. b and c, Full-grown specimenswith large nuclei and clearerprotoplasm, containing numerousrefringent granules(r. gr.). d and e, Morula stages, derivedfrom b and c by division ofthe body into segmentscentred round the nuclei,each cell so formed being aspore. Between the sporesa certain amount of intercellularsubstance or residualprotoplasm is left, in whichthe refringent granulesseem to be embedded. Themorula may break up forthwithand scatter the spores,or may first round itself offand form a spherical cystwith a tough, fairly thickwall. | f, Empty, slightly shrunken cyst,from which the spores haveescaped. g, Free spore or youngest unicellulartrophozoite. h, i, j, Commencing growth of thetrophozoite, with multiplicationof the nuclei, whichresults ultimately in formssuch as a and b. |
Bertramia, a well-known parasite of the body-cavity of Rotifers, will serve very well to give a general idea of the life-cycle so far as it has yet been made out (fig. 14). The trophozoite begins life as a small, rounded uninucleate corpuscle, which as it grows, becomes multinucleate. The multinuclear body generally assumes a definite shape, often that of a sausage. Later, the protoplasm becomes segregated around each of the nuclei, giving the parasite a mulberry-like aspect; hence this stage is frequently known as a morula. The uninuclear cellules thus formed are the spores, which are ultimately liberated by the break-up of the parent body. Each is of quite simple, undifferentiated structure, possesses a large, easily-visible nucleus, and gives rise in due course to another young trophozoite. In some instances, as described by Minchin, the sporulating parasite becomes rounded off and forms a protective cyst, doubtless for the protection of the spores during dissemination.
In some forms (e.g. Haplosporidium and Rhinosporidium) the spore-mother-cells, instead of becoming each a single spore, as in Bertramia, give rise to several, four in the first case, many in the latter. Sometimes, again, the spore, while preserving the essentially simple character of the sporoplasm, may be enclosed in a spore-case; this may have the form of a little box with a lid or operculum, as in some species of Haplosporidium, or may possess a long process or tail, as in Urosporidium (fig. 15).
The Haplosporidia are divided by Caullery and Mesnil into three families, Haplosporidiidae, Bertramiidae and Coelosporidiidae; one or two genera are also included whose exact position is doubtful.
(a) Haplosporidiidae: 3 genera, Haplosporidium, type-species H. heterocirri; Urosporidium, with one sp., U. fuliginosum; all parasitic in various Annelids; and Anurosporidium, with the species A. pelseneeri, from the sporocysts of a Trematode, parasitic on Donax.
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| From Caullery and Mesnil, Archives de zoologie expérimentale, vol. 4, 1905, by permissionof Schleicher Frères et Cie, Paris. | |
| Fig. 15.—Spores of various Haplosporidia. | |
1. Haplosporidium heterocirri: 2, H. scolopli. | 3, H. vejdovskii. 4, Urosporidium fuliginosum: |
(b) Bertramiidae: 2 genera, Bertramia, with B. capitellae from an Annelid and B. asperospora, the Rotiferan parasite above described; and Ichthyosporidium, with I. gasterophilum and I. phymogenes, parasitic in various fish.
(c) Coelosporidiiae: genera Coelosporidium, type-species C. chydoriclola; and Polycaryum, type-species P. branchiopodianum. These forms are parasitic in small Crustacea. The genus Blastulidium is referred, doubtfully, by Caullery and Mesnil to this family; but certain phases of this organism seem to indicate rather a vegetable nature.