Saccamoeba (Frenzel, 1892) Bovee, 1972 (ref. ID; 4891)
Class Tubulinea: Order Tubulinida: Family Hartmannellidae (ref. ID; 6789)
Family Hartmannellidae (ref. ID; 4742, 7606, 7755)

[ref. ID; 7606]
Monopodial free-living amoebae. It is distinguishable from Trichamoeba by several characters including surface structure (Page 1985) and the complete lack of pseudopodia from all floating forms. At present the two genera are also distinguished by nuclear structure. All known species of Saccamoeba have a vesicular nucleus with a central nucleolus (Page 1976), but the possibility of some diversity of nucleolar organisation amongst members of the family Amoebidae, as amongst the Thecamoebidae (Page 1976) should be kept in mind. Saccamoeba, like Trichamoeba, often has a villous uroid. (ref. ID; 7606)

Saccamoeba limax (Dujardin, 1841) (ref. ID; 7393, 7755) reported author and year? (ref. ID; 4742, 4754, 6789)
Notes; This species seems fairly common and widespread, at least in the Northern Hemisphere, whether or not the organism to which the name is here applied is the same as Dujardin's (1841) Amoeba limax (Page 1969, 1974; Bovee 1972). Two clones from Loch Morar in Scotland have been identified as belonging to the same species as the isolate from a small lake in Alabama, USA (Page 1969, 1974). Electron micrographs of the American strain and one Scottish strain are presented for comparative purposes. The amoebae of the American strain were somewhat smaller, with a mean length of 56 um compared with 63.8 um for the Scottish strain. The mean nuclear diameters were 7.1 and 8.4 um respectively. Both had truncate bipyramidal crystals, up to 30 or more per cell, with a maximum length of 2.5-3.7 um, though some amoebae lacked crystals. These crystals showed somewhat fainter optical activity than those of Mayorella spp. (Page 1983). The nucleus sometimes showed traces of an inner lamina of fibrous material parallel to the nuclear membrane, but most sections showed no trace of such a lamina. As reported previously (Page 1969), a nucleolar lacuna was very common; the material in it appeared very similar to that surrounding the nucleolus. Both strains had cup-like surface structures, apparently hexagonal in cross-section. The greater distinctness of these elements in some sections of the Scottish strain may be due to the different fixation method used of that particular cell. These elements had a diameter of approximately 40 nm and a height of nearly 20 nm above the plasma membrane. The mitochondria of both strains were oval to elliptical, never elongate in profile, with a maximum length of 1.2 um, usually less. The cristae were tubular, with a diameter of approximately 50 nm, seldom branching. Endocytic bacteria, sometimes seen to be dividing, were found in both strains but appeared somewhat less numerous in the Scottish strain. The Golgi bodies, distributed at random, were flattish or biconcave, each composed of four or five flattened saccules. They sometimes occurred in pairs, which might be at right angles to each other. The maximum over-all width was 0.7 um in the American strain and 1.1 um in the Scottish strain. The rough endoplasmic reticulum had the form of both longish, flattened tracts and roundish vesicles. The uroid, a characteristic feature in the light microscopic appearance of Saccamoeba, contained a high concentration of inclusions such as mitochondria and endocytic bacteria. Cytoplasmic filaments are especially noticeable. Sections of uroidal villi showed a small quantity of filamentous material orientated in the long axis rather than the continuous fibrous cores of anterior subpseudopodia and floating pseudopodia of such amoebae as Protacanthamoeba and Paraflabellula (Page 1981; Page and Willumsen 1983). The contractile vacuole was an especially conspicuous feature of Saccamoeba, bulging prominently either at the posterior end of just in front of the bulbous uroid, if the latter was present. A contractile vacuole, which was filling when fixed, can be seen just anterior to the uroid (American strain). The contractile vacuole of S. stagnicola is surrounded by an extensive spongiome, though the vacuole is not. Possible the vacuole (S. limax, Scottish strain) was beginning to refill after emptying incompletely. The flattened shape is characteristic of that seen in Saccamoeba when emptying has not been completed. Neither the American strain nor the two Scottish isolates form cysts in culture. (ref. ID; 7755)
Habitat; Freshwater. (ref. ID; 7393)
Examined materials; CCAP 1534/6, freshwater, USA (Page, 1969), and research strain 215, from Loch Morar, Scotland. (ref. ID; 7755)
Saccamoeba limna Bovee, 1972 (ref. ID; 7393)
Habitat; Freshwater. (ref. ID; 7393)
Saccamoeba lucens Frenzel, 1892 sensu Bovee, 1972 (ref. ID; 7393)
Habitat; Freshwater. (ref. ID; 7393)
Saccamoeba marina Anderson, Rogerson & Hannah, 1997 (ref. ID; 7393 original paper)
Description; Elongate, limax amoeba (mean length 72.5 +/- 14.9 um and mean breadth 20.7 +/- 4.5 um) of variable shape especially when changing direction of locomotion, containing vacuolar-bound crystals. Cells range in size from 32 to 108 um. The length to beadth ratio is 3.5. Locomotion is steady, not eruptive, and of moderate rate 1.3 +/- 0.6 um/s. Nucleus spherical (6.0 um) with central nucleolus (2.0 um) containing a less electon dense lacuna appearing in Nomarski light optics as a central dimple. Posterior of cell with bulbous uroid characteristic of the genus Saccamoeba. Inactive, rounded cells, are 26-36 um in diameter. Fine structure is characteristic of the genus Saccamoeba, including the spherical nucleus with central nucleolus, and glycocalyx with truncated glycostyles with circular profiles in tangential section. The highly vacuolated cell contains crystals that vary in shape from rounded to cuboidal or elongate as shown by scanning electron microscopic analysis. The mitochondria have branched tubular cristae. Food vacuoles contain bacteria and diatoms. (ref. ID; 7393)
Remarks; The genus Saccamoeba includes limax amoebae with noneruptive locomotion and a prominent posterior uroid. The large vacuoles containing crystals are commonly observed in species of Saccamoeba (Bovee 1985; Page 1988). During locomotion, the crystal-containing vacuoles tend to tumble forward within the cytoplasm as the endoplasm streams forward. The light microscopic and fine structural features presented here clearly conform to the major generic features of Saccamoeba (Bovee 1985; Page 1988). Page (1983) reported a limax amoeba collected from rock pools in Norfolk, U.K. that he suggested may have been a Saccamoeba, but he did not describe it further other than showing a light micrograph. A possible marine Saccamoeba sp. (c. 50 um) has also been identified in samples from Niva Bay at a location 15 km south of Helsingor, Denmark, but it has not been described in a publication (Smirnoff, A., pers. commun). The somewhat hyaline anterior zone of the pseudopodium contains small electron-lucent vesicles of irregular shape suspended in a fine filamentous hyaloplasm. The large vacuoles that contain the crystals appear empty in transmission electron micrographs due to dissolution of the crystals during processing for embeddement in epon. However, SEM views of isolated crystals show that they are approximately 1 to 3 um in size and vary from rather rounded or to elongate bodies with somewhat irregular surface texture. The mitochondria are scattered throughout the endoplasm among the large vacuoles and are interspersed among small vesicles c. 0.5 um with densely staining membranes. Digestive vacuoles containing bacteria also are present in the peripheral endoplasm. The lacuna in the nucleolus is not species specific and has been reported in other limax amoebae including Vahlkampfia sp. (Page 1985). In overall morphology, the shape of S. marina varies from vermiform to somewhat multilobate at the anterior, although the more vermiform shape is common during steady locomotion. Floating form is irregularly lobate. The length to breadth ratio is 3.5. Saccamoeba spp. from freshwater environments tend to be larger limax amoebae. For example, Saccamoeba wakulla Bovee, 1972 from North America has lengths up to 175 um with some not exceeding 130 um (Page 1988). Sizes of other species are: Saccamoeba stagnicola Page, 1974 (30-75 um) and mean length of 50 um. Saccamoeba limna Bovee, 1972 (to 120 um), Saccamoeba lucens Frenzel, 1892 sensu Bovee, 1972, (70-100 um), and Saccamoeba limax (Dujardin, 1841) (35-85 um) with mean length of 60 um (Bovee 1972, 1985; Page 1988). The latter is closer in size to S. marina, with sizes ranging from 32 to 108 um and a mean length as reported above of c. 72.5 um. Saccamoeba limax, however, is a slender amoeba with a length to breadth ratio of 4.8 compared to 3.5 for S. marina. The former species contains bipyramidal crystals, and the size of the nucleus (6-11 um) somewhat larger than that of S. marina (Bovee 1972, 1985; Page 1988).
Etymology; Saccamoeba marina is named for its clearly marine habitat where it was isolated. (ref. ID; 7393)
Habitat; Marine, fine sandy, surface sediments, low in organic content 0.3% (w/v) with salinity of c. 32 ppt. (ref. ID; 7393)
Type locality; Isolated from sediments in Kames Bay in the Firth of Clyde. (ref. ID; 7393)
Specimen deposited; A holoype specimen (gultaraldehyde/osmium fixed slide, registration number 1996:5:28:3) has been deposited with the British Museum of Natural History, London. (ref. ID; 7393)
Saccamoeba stagnicola Page, 1974 (ref. ID; 7393, 7755)
Notes; In the nucleus no trace of an inner fibrous lamina was found, and nucleolar lacunae, though occasionally seen, were less common that in S. limax. The surface coat appeared at first sight to consist of many short filaments like those common in the family Amoebidae (Page and Baldock 1980; Page and Robson 1983), but closer examination revealed that these were delicate, probably hexagonal elements about 25 nm high with a similar transverse diameter. They appeared less cup-shaped than those of S. limax. The surfaces of both strains of S. stagnicola were very similar. The mitochondria were often elongate, though circular and oval profiles were also seen. Some of the longer ones, which might reach a length of 1.9 um were constricted in the middle. The tubular cristae, about 50 nm in diameter, had a twisting appearance but not a regular helical structure; branching was rather rare. Both strains contained endocytic bacteria, possibly of two kinds, which were occasionally seen to be dividing. These were not enclosed in amoebic membranes. The Golgi bodies, distributed at random, were flattened or slightly biconcave, usually with five flattened saccules, with an over-all width up to 1 um. The rough endoplasmic reticulum had the form of small, slightly compressed vesicles. The cyst wall could be studied only in strain CCAP 1572/2, because the capability of strain 1572/1 to produce cyst has been greatly reduced since a few months after its isolation (Page 1974). The cyst wall consisted of two distinct layers: an inner, very lightly staining layer, with a regular thickness of 0.3-0.4 um, which appeared to be made up of finely fibrous material, much of it orientated radially to the cell surface; and an outer, much more densely staining layer of fibrous material, with the fibres generally parallel to the cell surface. The outer layer was very irregular in thickness, measuring approximately 0.5-0.8 um over much of its extent. Occasionally it was somewhat separated from the inner layer. These description accords well with the earlier light microscopic report (Page 1974), and the irregular outer layer undoubtedly corresponds to the sticky coat described then. (ref. ID; 7755)
Habitat; Freshwater. (ref. ID; 7393)
Type locality; Both original strains (CCAP 1572/1 (strain 127 of Page 1974)) and (CCAP 1572/2 (strain 134 of Page 1974) were isolated (from different sites) in the Cambridge area (Page 1974). (ref. ID; 7755)
Saccamoeba wakulla Bovee, 1972 (ref. ID; 7393)
Habitat; Freshwater. (ref. ID; 7393)