Paramoeba

Paramoeba Schaudinn, 1896

[ref. ID; 2297]
The genus comprises amoebae which contain, in addition to the usual kind of nucleus, a DNA-rich body variously designated Nebenkorper, paranucleus or secondary nucleus. The original and type species, P. eilhardi. (ref. ID; 2297)

[ref. ID; 4178]
The genus Paramoeba is distinguished from other small marine mayorellid amoebae primarily by the presence of one or more paranuclear, DNA-containing parasomes. Parasomes are also found in the morphologically dissimilar genus Janickina, and in both genera they are very similar both histologically and ultrastructurally. The parasomes of Janickina has been interpreted as a symbiotic kinetoplastid flagellate, Perkinsiella amoebae. The genus Paramoeba is common and widely distributed, and free-living North Atlantic species have been recovered from sediment, saltmarsh, and oceanic water from the surface microlayer to a depth of at least 300 m. (ref. ID; 4178)

Paramoeba aestuarina Page, 1970 (ref. ID; 2297 original paper, 3847, 4178, 7710)
Paramoeba eilhardi Schaudinn, 1896 (ref. ID; 2039, 2297)
Paramoeba invadens Jones, 1985 (ref. ID; 3611, 4178 original paper)
Paramoeba pemaquidensis Page, 1970 (ref. ID; 2093, 2297 original paper, 2684, 3847, 4178, 4248)
Paramoeba perniciosa (ref. ID; 2684, 4178)
Paramoeba schaudinni de Fara & de Cunha & Pinto (ref. ID; 3847)

Paramoeba aestuarina Page, 1970 (ref. ID; 2297 original paper, 3847, 4178, 7710)

Descriptions

Locomotive form characteristically producing a few blunt, digitiform pseudopods from anterior hyaline region, resulting in hand-like appearance. Length often more than twice breadth in locomotion. True radiate floating form. Single vesiculate nucleus to which is joined closely a Nebenkorper or paranucleus containing a prominent, DNA-containing body. (ref. ID; 2297)
Marine amoebae. (ref. ID; 3847)

Measurements

Length locomotive form approximately 10-20 um; nucleus 2.5-3 um. (ref. ID; 2297)

Paramoeba invadens Jones, 1985 (ref. ID; 3611, 4178 original paper)

Diagnosis

Paramoeba invadens n. sp. Flattened, elongate locomotive form with mean greatest dimension ca. 22-30 um (range 10-60 um) and L:W ratio often ca. 2 (1.7-2.4). Anterior region often broader with hyaloplasm having irregular margin or short, blunt subpseudopodia, sometimes forming linguiform extensions with short subpseudopodia. Digitiform pseudopodia, to ca. 10 um long, may also occur. Single nucleus ca. 4 um in diameter. Single parasome ca. 3x2 um has Feulgen-positive poles but no central Feulgen-positive band and appears biploar or annular in living phase-contrast or fixed, stained preparations. Floating form has 3-6 short pseudopodia. (ref. ID; 4178)

Descriptions

Locomotive form: Locomotive forms of amoebae from cultures and from fresh tissues are similar. The amoebae are flattened and elongated in the direction of the travel, with a length:width ratio of approximately 2:1. There is considerable variation in form, and irregular outlines are common, but typical actively moving forms are broader anteriorly with a hyaloplasmic region occupying up to about 25% of the total length of the amoebae. The margin of the hyaloplasm is irregular and produces short, blunt, conical subpseudopodia that measure up to 1-3 um in length. Longer, digitiform subpseudopodia can also occur. No longitudinal ridges have been seen. Reversal of direction often produces transitory posterior and anterior hyaloplasmic regions of similar extent. The broad hyaline front is often split into two or more hyaloplasmic extensions, which may become linguiform and often have subpseudopodia, giving the appearance of bifurcate or trifurcate tips. Occasional digitiform pseudopodia, up to approximately 10 um in length, may arise from or adjacent to the hyaloplasmic region. Transitory, smaller (5 um or less), thin, digitiform pseudopodia often arise along the lateral edges of the amoeba. Sometimes, particularly in rapidly advancing forms and in semifloating forms, only long digitiform pseudopodia may be present, with the hyaloplasm temporarily reduced or absent. (ref. ID; 4178)
Floating form: Typical floating forms have a discrete central mass 5-13 um in diameter (average 8.5 um, n=35) with short pseudopodia (ratio of pseudopodial length:diameter of central mass=0.9). The pseudopodia are few in number (3-6 pseudopodia are common), and radiate floating forms with numerous long pseudopodia have not been seen. Floating forms do not appear to form very readily in normal culture conditions. (ref. ID; 4178)
Semifloating and tissue-dwelling forms: Amoebae dislodged from tissues or in fresh coelomic fluid often appear intermediate in form between locomotive and floating. The cytoplasm may be partially contracted but is no reduced to a small discrete central mass, and the length:width ratio is usually less than 2. Pseudopodia are variable in size and shaped and can arise at any point on the surface. Often 1-6 pseudopodia are present, arising from 1, 2, or 3 main axes. These is no expanded hyaloplasmic region. Pseudopodia may be long and digitiform (9-17 um in length; 3-6 um in width at the base) or short and conical or digitiform (2-4 um in length; 1 um at the base). Broad or linguiform pseudopodia may bear subpseudopodia. Pseudopodia are extended and withdrawn rapidly without adhesion to the substrate. These semifloating forms also occur within ampullae, where the fluid is constantly circulated by ciliated coelomic lining cells. This can sometimes be observed in whole mounts of fresh ampullae, which are thin-walled and retain their ciliary current well in simple squash preparations. Amoebae whirl in the current, together with a variety of host coelomocytes and necrotic cells. Amoebae within tissues appear rounded. Pseudopodia may be absent or short and broad. These amoebae often appear stationary, but they are capable of moving between cells without adopting a typical locomotive form. They can conveniently be observed in the thin tissues of amupllae in squash preparations. Amoebae within the walls of ampullae have been observed to move through the cell layers of the all (coelomic lining, muscle, connective tissue, eithelium), emerging into the medium and adapting and semifloating form as they leave the tissue. Movement into nerve tissue or into coelomocyte clumps in coelomic fluid has also been observed and can be rapid; amoebae can move between the surface cells and disappear from view in less than a minute. (ref. ID; 4178)

Comments

In size and surface ultrastructure, P. invadens closely resembles P. pemaquidensis Page, 1970, but in locomotive forms and scarcity of supernumerary parasomes it is much closer to P. aestuarina Page, 1970. These is insufficient information from the parasitic P. perniciosa Sprague, Beckett & Sawyer, 1969 to determine where these features fall within the limits of variability for this species, but P. perniciosa appears to be a larger, less elongate organism, and there has been no success in maintaining it in culture. The staining affinity of the parasome in P. invadens is quite distinct from that in the other species, lacking any indication of a Feulgen-positive central band and with densely Feulgen-positive poles. (ref. ID; 4178)

Habitat

Marine amoeba. (ref. ID; 3611)
Tissues of Strongylocentrotus droebachiensis from sublittoral zone, Atlantic coast of Nova Scotia; experimentally in seawater surrounding diseased sea urichins. Free-living habitat or other potential hosts not known. (ref. ID; 4178)

Type slide

Holotype and paratype slides retained for deposition in the National Museum of Natural Sciences, Ottawa, Additional paratypes remain with the author. (ref. ID; 4178)

Paramoeba pemaquidensis Page, 1970 (ref. ID; 2093, 2297 original paper, 2684, 3847, 4178, 4248)

Descriptions

Locomotive form with rather extensive anterior hyaline zone, with irregular anterior margin and occasionally conical pseudopods projecting ahead of anterior margin in locomotion. Length usually greater than breadth during locomotion. True radiate floating form. Single vesiculate nucleus to which is joined closely a Nebenkorper or paranucleus containing a prominent, DNA-containing body. (ref. ID; 2297)
Marine amoebae. (ref. ID; 3847)

Measurements

Length of locomotive form approximately 14-38 um; nucleus 3-6 um. (ref. ID; 2297)

Paramoeba schaudinni de Fara & de Cunha & Pinto (ref. ID; 3847)

Descriptions

Marine amoebae. (ref. ID; 3847)