Fig. 66.—Spores of various Gregarines. a, Xiphorhynchus. b, Ancyrophora. c, Gonospora. d, Ceratospora. (After Léger.)
There are variations in the morphology and life-cycle of gregarines besides those that have been mentioned. It is not within the scope of this book to discuss them in detail, but the following may be noted:—
Morphological differentiation of gametes may occur as in Stylorhynchus oblongatus (fig. 65), which differentiation is probably of a sexual nature.
The sporocyst really consists of two layers, an epispore and an endospore. Externally the spores of different gregarines show great variety in shape and markings, and spines, or long processes may be present (fig. 66).
The resistant spores serve for the transmission of the gregarines from host to host. The mode of infection is contaminative, the spores expelled with the dejecta of one host being absorbed with the food of a new host.
The Gregarinida may be classified as follows:—
Sub-order I.—Eugregarinea, without schizogony.
Tribe 1.—Acephalina.—Without an epimerite and non-septate; often “cœlomic” (body-cavity) parasites. E.g.: Monocystis, with several species parasitic in the seminal vesicles of earthworms. Many other genera parasitic in Echinodermata, Tunicata, Arthropoda, etc.
Tribe 2.—Cephalina.—With an epimerite, either temporarily or permanently, in the trophic phase. Usually septate (except Doliocystidæ). Many families, genera and species. Common in the digestive tracts of insects. E.g.: Gregarina, with several species, Gregarina ovata in the earwig, Gregarina blattarum in the cockroach, Stylorhynchus in beetles, Pterocephalus in centipedes, etc.
Sub-order II.—Schizogregarinea, with schizogony.