ALBERT

Notes: The phoront of the apostomatous ciliate, Hyalophysa chattoni, is an encysted stage that is carried on the exoskeleton of its crustacean host until the ecdysis of the host. At molting the phoront rapidly metamorphoses to the feeding stage, excysts, and immediately begins to feed on exuvial fluid trapped in the cast-off exoskeleton. The fine structure of the resting phoront resembles that of the preceding migratory stage, the tomite. A prominent ventral tuft of cilia, the ogival field, has vanished, and the trichocysts that paralleled the kinetics have disappeared. The dense inclusion bodies that were concentrated around the mouth and falciform fields have dispersed and greatly decreased in number. The cytoplasm and its membranous organelles do not appear visibly condensed or altered from the preceding stage in the life cycle. The phoront is merely quiescent instead of dormant.Unlike the few ciliate cysts previously examined by electron microscopy, the phoront's cyst is not divisible into separable layers. It resembles the loricae of certain suctoria in being formed principally of a fibrous substance, the outer surface of which has a paracrystalline pattern. The peduncle attaching the cyst to the crab's gill is a continuation of the cyst wall although its structure is somewhat modified.The most conspicuous innovation in the phoront's fine structure is the massive tracts of microtubules that run longitudinally through the macronucleus. The microtubules are in intimate contact with Feulgen-positive chromatin masses which are crowded toward the periphery of the macronucleus.

Notes: SYNOPSIS. Hyalophysa Iwoffi sp. n. is described from the shrimp, Palaemonetes paludosus. Its life cycle is like that of other exuviotrophic apostomes. Hyalophysa Iwoffi differs from the type species, H. chattoni, in the details of its infraciliature and the shape of its macronucleus during the trophont stage. Emended diagnoses of the genus, Hyalophysa, and the species, H. chattoni, also are given.

Notes: SYNOPSIS. Terebrospira chattoni sp. n. may be a species in transition between ectosymbiosis and endosymbiosis. It penetrates the epicuticle of Palaemonetes pugio and feeds on the endocuticle by dissolving galleries through it and absorbing the products of dissolution. Although similar in some respects to species of the endosymbiotic apostome genus Synophrya, T. chattoni is clearly related to ectosymbiotic apostomes that feed on exuvial fluid. However, instead of stimulating the metamorphosis of a phoront to a trophont, the host's ecdysis stimulates T. chattoni to metamorphose from a dedifferentiated trophont with 13 meridional kineties to a protomont, a predivision stage with 10 spiralled kineties. The protomont encysts and dedifferentiates to the division stage, an orthotomont with 13 kineties, either on the new exoskeleton before ecdysis, within a chamber in the endocuticle of the old exoskeleton, or on a substrate away from the host and the molt. The site of division determines the product of the division. On the new exoskeleton, the tomites in the reproductive cyst secrete walls around themselves thereby forming the lenticular, compartmented cysts characteristic of Terebrospira. Each daughter tunnels out of its compartment into the endocuticle. Although its infraciliature remains undifferentiated like that of the orthotomont, the ciliate in the gallery is the trophont, the only feeding stage in the life cycle. Daughters originating from the division of the orthotomont in a chamber in the endocuticle swim out of the exoskeleton at ecdysis. encyst on the substrate, and presumably form tomites. When the protomont itself leaves the molt, it encysts on the substrate and divides to form daughter cells with a rosette and the pattern of ciliature of the conventional tomite of other apostome genera. Tomites carry the infection to new hosts while compartmented cysts insure that the original host retains the infection. Terebrospira chattoni is always astomatous, although a dedifferentiated oral ciliature appears in the orthotomont and persists in the trophont. Terebrospira chattoni sp. n. is separated from T. lenticularis Debaisieux the other species in the genus because the latter species may divide outside a cyst and because T. chattoni has an extra reproductive stage in its life cycle.

Notes: SYNOPSIS. The fine structure of the organelles concerned with the ingestion of exuvial fluid by the trophont of the apostome ciliate, Hyalophysa chattoni, has been examined. One of the taxonomic characteristics of the order Apostomatida is that cytostomes of ciliates within the taxon are reduced and evolving toward astomy. When examined by electron microscopy the cytostome of H. chattoni appears as a small region of active pinocytosis which is continuous with a very large cortical area, the extended cytostome. The fine structure of the extended cytostome resembles that of the cytostomes of ciliates from other orders in that it is covered by a single membrane underlain with microtubular ribs. Beneath the extended cytostome are accumulations of peculiar organelles that may represent stored membrane for recycling during food vacuole formation. Associated with the site of pinocytosis is a complex fiber that may be contractile.

Notes: SYNOPSIS. The schizonts of Haemoproteus columbae resemble the exoerythrocytic schizonts of avian Plasmodium in their fine structure. Haemoproteus infects endothelial cells and grows several hundredfold in volume, destroying the cytoplasm and nucleus of the host cell. The schizont's plasma membrane is trilamellar with a dense outer lamella. Some schizonts have micropores in their plasma membranes, but there is no evidence for ingestion thru them. Instead, numerous vesicles and channels fill the host cell cytoplasm and give its plasma membrane and periparasitic vacuolar membrane the appearance of active pinocytosis. The parasite's membrane shows no sign of pinocytosis, indicating that it probably feeds by diffusion. The growing schizont has numerous mitochondria, nuclei, and ribosome-rich cytoplasm which contains electron-lucent vacuoles and clefts. The latter appear to be artifacts of fixation.

Notes: SYNOPSIS. The first sign of merozoite formation in schizonts of Haemoproteus columbae is the accumulation of dense material at intervals beneath the plasma membrane of the schizont. The schizont's membrane then invaginates in deep furrows cleaving the parasite into pseudo-cytomeres. thereby increasing the area of membrane available for differentiation. Signs of differentiation appear under this membrane as soon as it is formed. Rhoptries and polar rings develop in the region of the dense accumulations, the cytoplasm containing these structures begins to elevate, and each evagination differentiates into a merozoite. When the merozoite is half-formed, the cytostome appears, then dense bodies at the apex of the organism, and finally a spherical body intimately associated with a mitochondrion. These merozoites of Haemoproteus are assumed to be the forms that penetrate erythrocytes and become gametocytes. They contain the same organelles as merozoites of Plasmodium. However, the merozoites of Haemoproteus are oval like the erythrocytic merozoites of Plasmodium rather than elongate like the exoerythrocytic merozoites. This body shape may be a generic characteristic or it may indicate a structural difference between exoerythrocytic merozoites and merozoites that infect erythrocytes.When the merozoites of Plasmodium, Haemoproteus and Leucocytozoon are compared, the first 2 genera appear closely related, but Leucocytozoon seems very different. Perhaps it should not be included within the Haemoproteidae.

Notes: SYNOPSIS. The nature and sequence of changes involved in the metamorphosis of the phoront of Hyalophysa have been examined in the light microscope using both living and silver-impregnated ciliates. The phoront's infraciliature, which resembles that of the migratory tomite, differentiates to the trophont (feeding stage) infraciliature without an intervening dedifferentiation. The primary visible event of metamorphosis is the growth of the metastomial area that distorts the meridional somatic kineties so that they curve or spiral around it. The distinct borders and intense argentophilia of the metastomial area suggest that it is a discrete organelle which is probably involved in the management and concentration of a large volume of dilute food. The anterior ventral field of kinetosomes, whose presence distinguishes Hyalophysa from Gymnodinioides, forms from a disorganized anterior segment of falciform field 9.The rapid and pronounced elongation of the somatic kineties supports our view that the kinetodesmos elongates by the sliding of its component subfibrils upon one another, and that the accessory kinetosomes seen in the electron microscope become functional at metamorphosis. The movement of the kineties and contractile vacuole pore during metamorphosis suggests that differentiation in this instance is not directed by pellicular “fields” but by morphogenetic movements of the underlying cytoplasm.

Notes: SYNOPSIS. A new apostome ciliate was discovered in collections at Friday Harbor, Washington and the San Francisco area. All stages of the life cycle were studied in both living and stained condition.Dormant encysted stages (phoronts) occur on the gills of Pagurus hirsutiusculus. Excystation occurs in synchrony with the molting of the host yielding the trophic stage (trophont), which feeds on the exuvial fluids trapped in the crab's cast-off exoskeleton. The trophont becomes greatly enlarged as a result of feeding, and the cytoplasm and organelles become compressed into a thin cortical layer. Each fully grown trophont encysts (becoming a tomont) as a prelude to repeated binary fission, which results in the release of actively motile offspring (tomites). These disperse and promptly resume the encysted phoront stage on the host's gills.The Chatton-Lwoff silver impregnation method revealed that all stages of the life cycle have nine somatic kineties. In the trophont stage they are accompanied by an anterior ventral field of scattered clumps of kinetosomes. During conjugation the partners attach by their ventral surfaces between kineties 1 and 9 and at the left of the ventral field.The tomite stage was stained with Protargol. In addition to the characteristic features of the foettingeriid tomite also revealed by the Chatton-Lwoff method, Protargol revealed the following heretofore undescribed morphological features: a short row of kinetosomes immediately anterior to the ogival field; a line paralleling the left margin of the field; the continuity of kinety 8 with falciform field 8; the entrance of kinety 9 into the mouth and its ending against the rosette (an enigmatic organelle characteristic of Foettingeriinae).Feulgen stains showed that the chromatin in the macronucleus is dispersed in aggregates whose size and number vary with the stage of the life cycle. The major period of chromatin synthesis appears to be during the early tomont stage, when Feulgen-positive material increases visibly in amount and intensity of staining.This apostome ciliate was characterized as a new genus on the basis of the infraciliature of the trophont stage, its conjugation with ventral surfaces appressed, and its life cycle. It is named Hyalophysa (hyalo = glassy, physa = bubble) chattoni.

Notes: SYNOPSIS The sexes of mature gametocytes of Haemoproteus columbae Kruse circulating in the blood of the domestic pigeon can be identified in the electron microscope by the same criteria that distinguish them in the light microscope. The microgametocyte has a large nucleus and pigment granules restricted to the 2 extremities of its halter-shaped cells. The macrogametocyte has dense granular cytoplasm with scattered pigment granules and a small central nucleus. The sex of young gametocytes cannot yet be recognized.When blood containing mature gametocytes is cooled outside the body of the host visible signs of gametogenesis appear within 30 seconds. The earliest signs are increasing electron lucidity of the cytoplasm and separation of the outer membrane from the body of the parasite. The membrane may form vesicles or whorls or lie free in the erythrocyte's cytoplasm. The middle membrane of the parasite becomes the plasma membrane. Axonemes and microtubules appear in the cytoplasm and nucleoplasm of the microgametocyte. The macrogametocyte lags slightly behind the microgametocyte in development. With the first signs of differentiation, the host cell cytoplasm begins to disappear. The fate of the outer membrane and the erythrocyte's cytoplasm suggests the release of a lytic substance by the parasite.

Notes: SYNOPSIS. The structural changes leading to the formation of motile microgametes from a single immobile intracellular gametocyte have been examiued in the electron microscope. After pigeon blood infected with Haemoproteus columbae was exposed to the air at room temperature for a few minutes axonemes appeared in the parasite's cytoplasm and the cytoplasm itself appeared less dense. The axonemes were connected with bundles of intranuclear microtubules that were perhaps spindle fibers. No conventional kinetosomes or centrioles have been observed.After the microgametocyte left the erythrocyte, it assumed the shape of a polarized slug or a dumb-bell. Half of the organism was surrounded by a single membrane and filled by part of the nucleus. The other half was surrounded by the remains of the multiple membranes of the gametocyte and contained pigment granules, mitochondria, axonemes and nuclear extensions. The axonemes and nuclear extensions were segregated at the periphery of the cell, exterior to the gametocyte's inner membrane, and were assembled in situ into microgametes. The mature microgamete appeared to peel off from the gametocyte, leaving a residual body.