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Coccidia
1911 Encyclopedia Britannica
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I.-Iv]] represents the schizogony, commencing with infection of an epithelial cell by a sporozoite or merozoite. After stage IV the development may start again at stage I, as indicated by the arrows; or it may go on to the formation of gametocytes (V). V-VIII represents the sexual generation. The line of development, hitherto single (I-IV) becomes split into two lines - male (VI 6, VII VIII and female (VI VII VIII ?), culminating in the highly differentiated microand mega-gametes. By conjugation these two lines are again united. IX, X, show the formation of the zygote by fusion of the nuclei of the gametes. XI-XV, sporogony. H.C, hostcell; N, its nucleus; mz, merozoite; szt, schizont; ky, karyosome (or fragments of same); n.n, daughter-nuclei of schizont; pl.gr, plastinoid grains; ooc, oocyst; n.zyg, zygote-nucleus (segmentation-nucleus); sp.m, spore-membrane (sporocyst); rp, residual protoplasm of oocyst (" reliquat kystal "); rp.sp, residual protoplasm of spore (" reliquat sporal "); sp.z, sporozoite.
a, Young schizont in a cluster of spermatogonia; the host-cell (represented granulated) and two of its neighbours are greatly hypertrophied, with very large nuclei, and have fused into a single mass containing the parasite (represented clear, with a thick outline). The other spermatogonia are normal. b, Intracellular schizont divided up into schizontocytes (c), each schizontocyte giving rise to a cluster of merozoites arranged as a " corps en barillet "; spg, spermatogonia; h.c, host-cell; N, nucleus of host-cell or cells; n, nucleus of parasite; szc, schizontocyte; mz, merozoites; r b, residual bodies of the schizontocytes. (From Minchin, after Siedlecki.) ,ip.Sp -ode. C FIG. 4. - [[Phases Of Caryotropha Mesnilii, Siedl. (Par. Polymnia Nebulosa). Vi]]. 616.
FIG. 5. - [[Schizogony Of Adelea Ovata, A. Schn (Par. Lithobius Forficatus]]). a-c, generation; d-f, generation. a, Full-grown 7 schizont (megaschizont), with a large nucleus (n) containing a conspicuous karyosome (ky). b, Commencement of schizogony; the nucleus has divided up to form a number of daughter-nuclei (d.n). The karyosome of stage a has broken up into a great number of daughterkaryosomes, each of which forms at first the centre of one of the star-shaped daughter-nuclei; but in a short time the daughterkaryosomes become inconspicuous. c, Completion of schizogony; the 7 schizont has broken up into a number of megamerozoites mz) implanted on a small quantity of residual protoplasm (r.p.). Each 7 merozoite has a chromatic nucleus (n) without a karyosome.
d, Full-grown o schizont (microschizont), with nucleus (n), karyosome (ky), and a number of characteristic pigment-granules (p.gr).
e, Commencement of schizogony. The nucleus is dividing up into a number of daughter-nuclei (d.n), each with a conspicuous karyosome (ky). f, Completion of schizogony. The numerous micromerozoites mz) have each a nucleus with a conspicuous karyosome (ky) at one pole, and the protoplasm contains pigment-granules (p.gr) near the nucleus, on the side farthest from the karyosome. (From Minchin, after Siedlecki.) a, Minchinia chitonis (E.R.L.), (par. Chiton); b, Diaspora hydatidea, Leger (par. Polydesmus); c, Echinospora labbei, Leger (par. Lithobius mutabilis); d, Goussia motellae, Labbe; e, Diplospora (Hyaloklossia), lieberkuhni (Labbe), (par. Rana esculenta); f, Crystallospora crystalloides (Thel.), (par. Motella tricirrata). (From Minchin; b and c after Leger, the others after Labbe.) FIG. 6. - [[Association And Conjugation In Adelea Ova Ta]]. a, Young microgametocyte (gamc.) attached to a megagametocyte (4 gamc.). The nucleus of the microgametocyte gives rise to 4 daughter-nuclei (c) which become (d) 4 microgametes gam.). e, One of the microgametes penetrates the megagamete, which forms a fertilization-spindle composed of male and female chromatin and chr.). The other 3 microgametes and the residual protoplasm of the microgametocyte (r.p.) perish. The karyosome of the megagamete has disappeared, as such. f, Union of the chromatin of both elements, to produce the zygote-nucleus (n.zyg.). (From Minchin, after Siedlecki.) FIG. 8. - [[Sporogony And Spore-Germination In Barroussia Ornata, A. Sch., From The Gut Of Nepa Cinera]]. a, Oocyst with sporoblasts; b, oocyst with ripe spores; c, a spore highly magnified, showing the single sporozoite bent on itself; d, the spore has split along its outer coat or epispore, but the sporozoite is still enclosed in the endospore; e, t the sporozoite, freed from the endospore, is emerging; f, the sporozoite has straightened itself out and is from its envelopes. (From Wasielewski, after A. Schneider.) d e FIG. 7. - Spores Of Various Coccidian Genera.
n e 8,ga m -- freed digestive juices, which are thus enabled to reach the spores and cause the rupture of the sporocysts. As the result of instructive experiments, Metzner has shown that it is the pancreatic and not the gastric juice by which this liberation of the germs is effected. The liberated sporozoites creep out and proceed to infect the epithelial cells. The sporozoites (XV.) are from 15-20 p, long by 4-6 µ wide; they are fairly similar to merozoites in form, structure and behaviour, the chief point of distinction being that they have no karyosome in the nucleus (cf. above).
Comparing the life-cycle of other Coccidia with that just described, a greater or less degree of modification is frequently met with. In the process of schizogony two orders of division sometimes occur; the parent-schizont first divides up into a varying number of rounded daughter-schizonts (schizontocytes), each of which gives rise, in the usual manner, to a cluster of merozoites,' which thus constitute a second order of cells. Siedlecki (1902) has found this to be the case in Caryotropha mesnilii (fig. 4), and Woodcock (1904) has shown that it is most probably really the same process which Smith and Johnson (1902) mistook for sporogony when originally describing their Coccidian of the mouse, Klossiella. In Caryotropha, a perfectly similar state of affairs is seen in the formation of microgametes from the microgametocyte; this is additionally interesting as showing that this process is neither more nor less than male schizogony.
Coming to the sexual generation, considerable variation is met with as regards the period in the life-history when sexual differentiation first makes its appearance. Sexuality may become evident at the very beginning of schizogony, as, e.g. in Adelea ovata (Siedlecki, 1899), where the first-formed schizonts (those developed from the sporozoites) are differentiated into male and female (microand mega-schizonts) (see Plate II., fig. 5). Correspondingly, the merozoites, to which they give rise, are also different (microand mega-merozoites). In one or two cases sexuality appears even earlier in the cycle, and has thus been carried still farther back.
The Coccidia, as a whole, have not developed the phenomenon of association of the sexual individuals prior to gamete-formation which is so characteristic of Gregarines. Their method of endeavouring to secure successful sporulation, and thus the survival of the species, has been rather by the extreme specialization of the sexual process. In place of many female elements, which the primitive or ancestral forms may be assumed to have had,2 there is always, save possibly for one exception, 3 only a single relatively huge megagamete formed, which offers a comparatively easy goal for one of the many microgametes. Nevertheless in the effort to render fertilization absolutely certain, a few Coccidia have acquired (secondarily) the power of associating; a state of things which enables those forms, moreover, to effect an economy in the number of male gametes, only three or four being developed. Instances are seen in Adelea mesnili (Perez, 1903), A. ovata (fig. 6), and Klossia helicina (Siedlecki, 1899). It is very interesting to note that, in the two last cases, unless this association of the microgametocyte with the megagametocyte occurs, neither can the former produce male elements (microgametes) nor can the female individual maturate and become ready for fertilization. (Concerning this question of association see also Gregarines.) In sporogony, great variation is seen with respect to the number of spores and sporozoites formed; and, as in Gregarines, these characters are largely used for purposes of classification, under which heading they are better considered. Usually, the spores (fig. 7) are quite simple in outline, and not produced into 1 The merozoites are frequently arranged like the staves of a barrel - whence the term barillet, which is frequently used.
2 In Cyclospora, Schaudinn (1902) has noted certain abnormal cases of the persistence and further multiplication of the " reductionnuclei " of the female element (i.e. the nuclear portions given off during maturation), followed by multiple fertilization. This occurrence points strongly to the conclusion that there were originally many female gametes (cf. also the sporoblasts of Gregarines).
The remarkable forms parasitic in Cephalopods (of late known as Eucoccidium), if still ranked with the Coccidia, furnish an exception (see below).
spines or processes; exceptions are found, however, in a few instances (e.g. Minchinia chitonis). In one case (Coccidium mitrarium), the oocyst itself, instead of being spherical, is curiously shaped like a mitre.
The life-history as a whole is invariably undergone in a single host, i.e. there is no alternation of true hosts. 4 Schaudinn, in his work on the Coccidia of Lithobius (1 900), showed that the oocysts, expelled with the faeces may be eaten by wood-lice (Oniscus),. but when this happens they pass through the intestine of the wood-louse unaltered, the latter not being an intermediate host but merely a carrier.
The order Coccidiidea is divided into four families, characterized by the number of sporocysts (if any) found in the oocyst. Fam. Asporocystidae, Leger. No sporozoites are Classifi- formed in the oocyst, the sporozoites being unenclosed cation. (gymnospores).
Genus, Legerella, Mesnil. This genus actually conforms to Aim& Schneider's original definition of Eimeria, which was founded on what were really the schizogonous generations of other forms, then thought to be distinct. In view of the great confusion attending the use of this name, however, Mesnil (190x) has suggested the new one here adopted. Two species known, L. nova and L. testiculi, both from different species of Glomeris, a Myriapod; the former inhabits the Malpighian tubules, the latter the testis.
Fam. Disporocystidae, Leger. The oocyst contains 2 spores. Genus 1. Cyclospora, A. Schneider. Spores dizoic, i.e. with two sporozoites. C. glomericola, from the intestinal epithelium of Glomeris, and C. caryolytica, from the intestinal epithelium of the mole, intranuclear.
Genus 2. Diplospora, Labbe. Spores tetrazoic. D. lacazei, from many birds, is the best-known species; and others have been described from different Sauropsida. D. lieberkiihni is an interesting form occurring in the kidneys of the frog, which it reaches by way of the circulation.
Genus 3. Isospora, Schn. Spores polyzoic. Founded for I. rara, parasitic in the black slug (Limax cinereo-niger). Many authors consider that Schneider was mistaken in attributing many sporozoites to this form, and would unite with it the genus Diplospora. Fam. Tetrasporocystidae, Leger. The oocyst contains 4 spores. Genus 1. Coccidium, 5 Leuckart. The spores are dizoic and the sporocysts rounded or oval. A very large number of species are known, mostly from Vertebrate hosts. C. cuniculi (= C. oviforme) from the rabbit (intestine and diverticula), but also occurring sometimes in other domestic animals; C. falciformis, from the mouse; C. faurei from sheep; and C. schubergi, from Lithobius (a centipede), are among the best-known forms. All of them may cause disastrous epidemics of coccidiosis.
Genus 2. Paracoccidium, Laveran and Mesnil. This genus is distinguished from Coccidium by the fact that the sporocysts become dissolved up in the oocyst, thus leaving the 8 sporozoites unenclosed, recalling the condition in Legerella. P. prevoti, unique species, from the frog's intestine.
Genus 3. Crystallospora, Labbe. Spores also dizoic, but having the form of a double pyramid. C. crystalloides from a fish, Motella tricirrata. Genus 4. Angeiocystis, Brasil. Apparently 6 sporozoites, but the only species, A. audouiniae, has only been briefly described; from a Polychaete (Audouinia). Fam. Polysporocystidae, Leger. The oocyst contains numerous spores.
There are several genera with monozoic spores, characterized by variations in the form and structure of the sporocysts, e.g. Barroussia, Schn. (fig. 8), Echinospora, Leger, and Diaspora, Leger; most of these forms are from Myriapods.
Genus Adelea, Schn. Dizoic spores; sporocysts round or oval, plain. Several species are included in this well-known genus, among them being A. ovata, A. mesnili, A. dimidiata; most of them are parasitic in Insects or Myriapods.
Genus Minchinia, Labbe. Dizoic spores; the sporocysts are produced at each pole into a long filament. M. chitonis, from the liver of Chiton (Mollusca).
Genus Klossia, Schn. The spores are tetrazoic (or perhaps polyzoic). K. helicina from the kidney of various land-snails is the best-known form. Usually said to have 5 to 6 spores, but Mesnil considers that the normal number is 4, as is the case in another species, K. soror. Genus Caryotropha, Siedlecki. Many spherical spores (about 20) 4 Again with the exception of Eucoccidium. 5 Purists in systematic nomenclature maintain that this name should be relinquished in favour of Eimeria, since the latter was the first legitimate generic name given to a Coccidian. But one reason against the use of Eimeria has been stated already (it should be used for E. (Legerella) nova, if anywhere); and in addition, the word Coccidium and its important derivatives are now so universally established that it would be little short of ridiculous to displace them.
each with 12 sporozoites. C. mesnilii, unique species, from the spermatogonial (testis) cells of Polymnia (a Polychaete). An interesting point in the schizogony is the formation of schizontocytes (see above).
A Coccidian parasitic in the kidneys of the mouse has been described by Smith and Johnson (1902) and named by them Klossiella, on the ground that it possessed many spores, each with about 20 sporozoites. Woodcock has shown, however, that the authors were in all probabilit y dealing with a similar modification of schizogony to that which obtains in Caryotropha. The sporogony of this form (and hence its systematic position) remains at present, therefore, quite unknown.
There are several doubtful or insufficiently known genera, e.g. Bananella, Goussia, Hyaloklossia, Gonobia, Pfeifferella and Rhabdospora, many of which probably represent only schizogonous generations of other forms. (For information concerning these see Labbe, 1897.) Lastly it remains to mention the extremely interesting forms parasitic in Cephalopods. For some years these have provided a fruitful source of discussion to systematists. Here it may be stated simply that their systematic position and nomenclature were thought to have been finally settled by the researches of Jacquemet (1903) and Liihe (1902) in the following terms: Genus Eucoccidium. Li he (syn. Legerina Jacq.), Coccidia possessing polysporous oocysts and lacking schizogony, parasitic in Cephalopods. Two well-known species: E. eberthi (Labbe), (=Benedenia seu Klossia e. seu octopiana), parasitic in Sepia, which is trior tetra-zoic; and E. octopianum (Schn.), (syn. Benedenia seu Klossia o.) from Octopus, which is polyzoic, having Io to 12 sporozoites. In both forms cysts containing megaspores and megasporozoites, and others containing microspores and microsporozoites are found, considered as representing sexual differentiation thrown back to the very earliest stages of the life-cycle.
Quite recently much additional light has been thrown upon our knowledge of these parasites, including a new one, E. jacquemeti. Moroff (1906) has shown that not one but many megagametes are formed, and fertilized by the microgametes. For this reason he regards them as Gregarines rather than Coccidia. Further, Leger and Duboscq (1906) have found that the characteristic coelomic parasites (Aggregata) of Crustacea, generally regarded as gymnosporous Gregarines (i.e. Gregarines in which the sporozoites are naked) constitute in reality nothing more or less than a schizogonous generation of these Cephalopodan parasites, which have thus an alternation of true hosts. The ripe sporocysts from the Cephalopod are eaten by a particular crab (e.g. Portunus or Inachus, according to the parasite), the sporozoites are liberated and traverse the mucous membrane of the intestine, coming to rest in the surrounding lymphatic layer. Here a large " cyst " is formed, projecting into the body-cavity, the contents of which give rise to a great number of merozoites. On the crab being devoured by the right species of Cephalopod, the merozoites doubtless give rise to the sexual generation again.
As the name Aggregata is much the older, and as, moreover, there is no longer any reason to retain that of Eucoccidium, these parasites must in future receive the former generic appellation. With regard to the various specific names, however, they remain quite unsettled until the life-history is properly worked out in different cases (see also Gregarines).
It seems to the writer a much more open question than Moroff and Leger and Duboscq apparently suppose, whether these parasites are to be relegated to the Gregarines. For undoubtedly they have many Coccidian features, and on the other hand they differ in many ways from Gregarines. The chief feature of agreement with the latter order is the possession of many female gametes. As already said, there can be little doubt that this was the condition in the Coccidian ancestor, and it is by no means impossible that one or two forms existing at the present day remain primitive in that respect. On the other hand, the advanced character of the parasitism (the parasites remaining intracellular up to and including gameteformation); the entire lack of the characteristic feature of association; the schizogony, which is only a very rare occurrence in Gregarines, and which, in the present case, strongly suggests the process in Caryotropha and Klossiella; and, last but not least, .the varying number of the sporozoites (3 in one form, 10-15 in others), which is very different from the almost constant number (8) in Gregarines, are all characters in which these forms agree with Coccidia and not with Gregarines. Having regard to these points, the writer is inclined, for the present, to consider Aggregata as an offshoot rather from the Coccidian than from the Gregarine branch of the Ectosporan tree.
Bibliography. -The following are some of the important papers dealing with the order :-G. Bonnet-Eymard, " Sur l'Evolution de l'Eimeria nova, Schneider," C.R. Soc. Biol. 52, p. 659, 1900; L. Brasil, " Sur une Coccidie nouvelle, &c.," C.R.Ac. Sci. 139, p. 645, 1904; L. Cuenot, " Le'gerella testiculi n. sp., &c.," Arch. Zool. exp. (N. et R.), (3) To, P. 49, 6 figs., 1902; M. Jacquemet, " Sur la systematique des Coccidies des Cephalopodes," Arch. Protistenk. 2 p., 190, 1903; A. Labbe, " Recherches zoologiques, cytologiques et biologiques sur les Coccidies," Arch. zool. exp. (3), 4, p. 5 1 7, 3 pls., 1897; A. Laveran, " Sur lesmodes dereproduction d'Isospora lacazes," C.R. Soc. Biol. 50, p. 1139, 1898; A. Laveran and F. Mesnil, " Sur deux Coccidies intestinales de la Rana esculenta," op. cit. 54, p. 857, 9 figs., 1902; A. Laveran and F. Mesnil, " Sur la Coccidie trouvee dans le rein de la Rana esculenta, &c.," C.R.Ac. Sci. 135, p. 82, to figs., 1902; A. Laveran and F. Mesnil, " Sur quelques Protozoaires parasites d'une tortue, &c." t. c. p. 609, 14 figs., 1902; L. Leger, " Sur une nouvelle Coccidie 'a' microgametes cilies," op. cit., 127, p. 418, 1898; L. Leger, " Sur la morphologie et le developpement des microgametes des Coccidies," Arch. zool. exp. (N. et R.) (3), 6, 1898; L. Leger, " Essai sur la classification des Coccidies, &c.," Ann. Mus. Nat. Hist., Marseille (2), Bull. i. p. 71, 4 pls., 1898; L. Leger, " Sur la presence d'une Coccidie coelomique chez Olocrates, &c.," Arch. zool. exp. (N. et R.) (3), 8, p. i., 1900; L. Leger, " Sur le genre Eimeria et la classification des Coccidies," C.R. Soc. Biol. 5 2, p. 575, 1900; L. Leger and O. Duboscq, " Recherches sur les MVlyriapodes de Corse et leurs parasites," Arch. zool. exp. (4), 1, p. 307, 24 figs., 1903; L. Leger and O. Duboscq, " Sur l'evolution des Gregarines gymnosporees des Crustaces," C.R.Ac. Sci. 142, p. 1225, 1906; L. Leger and O. Duboscq, " L'Evolution dune Aggregata de la seiche chez le Portunus depurator," C.R. Soc. Biol. 60, p. 1001, 1906; M. Liihe, " Uber Geltung and Bedeutung der Gattungsnamen Eimeria and Coccidium," C. B. Bakter (I) 31 Orig, p. 77 1, 1902; C. B. Bakter, " Die Coccidien-Literatur der letzten vier Jahre," Zool. Centrlbl. 10, 45 pp., 1903; F. Mesnil, " Sur la conservation du nom generique Eimeria, &c.," C.R. Soc. Biol. 52, p. 603, 1900; F. Mesnil, " Les Travaux recents sur les Coccidies," Bull. Inst. Pasteur, i. pp. 473, 505, 1903; R. Metzner, " Untersuchungen an Coccidium cuniculi," Arch. Protistenk. 2, p. 13, pl. ii. 1903; G. Moussu and G. Marotel, " La Coccidiose du mouton et son parasite," Arch. Parasitol. 6, p. 82, pp figs., 1902; T. Moroff, " Sur l'evolution des pretendues Coccidies des Cephalopodes," C.R.Ac. Sci. 142, p. 652, 1906; C. Perez, " Le Cycle evolutif de l'Adelea mesnili, &c.," Arch. Protistenk. 2, p. I, pl. I, 1903; F. Schaudinn, " Untersuchungen fiber den Generationswechsel bei Coccidien," Zool. Jahrbiicher (Anat.) 13, p. 197, 4 pls., 1900; F. Schaudinn, " Studien fiber krankheitserregende Protozoen-I. Cyclospora caryolytica, &c.," Arb. kais. Gesundh.-amte, 18, p. 378, 2 pls., 1902; M. Siedlecki, " Reproduction sexuee. .. chez. Coccidium prqprium," C.R. Soc. Biol. 50, p. 664, figs., 1898; ?M. Siedlecki, " Etude cytologique. .. de la Coccidie de la seiche, &c.," Ann. Inst. Pasteur, 12, p. 799, 3 pls., 1898; M. Siedlecki, " Etude cytologique. .. de Adelea ovata," op. cit. 13, p. 169, 3 pls., 1899 M. Siedlecki, " Cycle evolutif de la Caryotropha mesnilii, &c.," Bull. Ac. Cracovie, p. 561, 5 figs., 1902; T. Smith and H. P.
J ohnson, " On a Coccidian (Klossiella muris, gen. et spec. nov.), &c.," J. 6, p. 303, 3 pls., 1902; H. M. Woodcock, " Notes on Sporozoa, I. On Klossiella muris, &e.," Q.J. micr. Sci. 48, p. 153, 2 figs., 1904. (H. M. Wo.)
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Bibliography Information
Chisholm, Hugh, General Editor. Entry for 'Coccidia'. 1911 Encyclopedia Britanica. https://www.studylight.org/encyclopedias/eng/bri/c/coccidia.html. 1910.
