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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Vampyrellidium

Vampyrellidium Zopf, 1885 (ref. ID; 654)

Phylum Sarcomastigophora Honigberg & Balamuth, 1963: Subphylum Sarcodina Hertwig & Lesser, 1874: Superclass Rhizopoda von Siebold, 1845: Class Filosea Leidy, 1879: Order Aconchulinida De Saedeleer, 1934: Family Vampyrellidae (ref. ID; 4670)

[ref. ID; 654]
The genus Vampyrellidium was described by Zopf (1885) as a new member of his family Vampyrellidae. According to Zopf Vampyrellidium differs from Vampyrella mainly in its life cycle: zoocysts and sporocysts are morphologically indistinguishable (the sporocysts having a slightly thicker wall), the resting spore does not develop within a cyst wall but as a free spore and only one amoeba emerges from both types cysts. The illustrations Zopf (1885) gave for Vampyrellidium vagans however do not indicate the presence of cyst-like stages in the life cycle of Vampyrellidium. His zoocysts most like represent spherical amoebae with completely retracted pseudopodia but without a cyst wall and the single illustration of the sporocyst is insufficient and bears no resemblance to resting stages in Vampyrella. Entz (1913) who also investigated Vampyrellidium vagans did not find cysts despite various attempts to induce cysts formation (high and low temperature, dryness, etc.). Later Ivanic (1934, 1936) described the presence of cysts in Vampyrellidium vagans. Ivanic however studied alcohol-fixed material only and for several reasons we conclude that he did not study a Vampyrellidium species at all, but rather a mixture of diverse amoebae. (ref. ID; 654)
  1. Vampyrellidium perforans Surek & Melkonian, 1980 (ref. ID; 654 original paper, 4256)
  2. Vampyrellidium vagans Zopf, 1885 (ref. ID; 654)

Vampyrellidium perforans Surek & Melkonian, 1980 (ref. ID; 654 original paper, 4256)

Diagnosis

Free living amoeba with clear, filose, sometimes branching, rarely anastomosing pseudopodia. Free floating cells spherical, 4-25 um diameter (average 20 um) with radiating filose pseudopodia. Filose pseudopodia up to 60 um long, 0.2-0.6 um wide. Cell shape of amoeboid cells highly variable from subglobose to elongate, sometimes irregular measuring 20-45x10-15 um; with filose, often branching pseudopodia and few lobose pseudopodia. Uninucleate, central nucleus (2-6 um diameter) and prominent nucleolus (1-2.7 um diameter) with smooth margin. 1-5 contractile vacuoles. Mucilaginous coat present. Reproduction by binaryfission of free amoebae, no cystlike stage occur. Amoeba feed on green algae, preferential species of Chlamydomonas. Feeding either by ingestion or by penetration of algal cell wall and uptake of cell contents with a broad, specialized pseudopodium. Empty algal cell walls expelled from the amoeba. (ref. ID; 654)

Descriptions

Vampyrellidium perforans exists in two different life forms, a free floating ("planktonic") form and a life form attached to a solid substrate ("amoeboid" life form). Cells of the planktonic life form are usually spherical with long, rarely branching filose pseudopodia radiating from the cells surface. The diameter of the cells (without pseudopodia) varies between 4 and 25 um (on the average 20 um). The length of the filose pseudopodia is variable, but may reach 60 um. At their proximal end the pseudopodia are maximally 0.6 um wide, at their tip only 0.15-0.3 um. Cells of the amoeboid life form exhibit a much greater variety of cell shapes from subglobose to elongate and often irregular shapes. The average cell dimensions out of 50 cells measured are 20-45x10-15 um. The amoeba flattens on the substrate and with respect of formation of pseudopodia often shows bipolarity. Pseudopodia of "amoeboid" cells are of two types, either filose or lobose. Filose pseudopodia are more variable in length and overall shape as in "planktonic" cells. Proximally they are 1.3-3.3 um wide. Towards their tip they taper and at their tips are only 0.15-0.3 um wide. Often filose pseudopodia arise from broad hyaline lobes. Branching of filose pseudopodia is more pronounced than in cells of the planktonic life form and even anastomoses between adjacent pseudopodia were sometimes seen. The cells are uninucleate. The nucleus contains one prominent nucleolus centrally located with a smooth margin. The diameter of the nucleus is variable from 2-6 um, that of the nucleolus from 1-2.7 um. The relation of diameters between the nucleus and it nucleus is always constant and about 2:1. Depending on the cell size 1-5 contractile vacuoles may be present in the peripheral parts of the cytoplasm. Contractile vacuoles reach a maximum size of 3.5-4 um directly before discharge and fill again in approximately 10 sec. Size and number of food vacuoles may differ considerably depending on different feeding behavior. With Indian ink a mucilaginous coat can be demonstrated surrounding the cell of V. perforans. Its extension is variable and roughly approximates the length of the filose pseudopodia. The mucilaginous coat is absent, when no filose pseudopodia are developed. Within the coat no bacteria are present and in cultures containing bacteria these are virtually excluded from the surface of the mucilaginous coat. Filose pseudopodia may be formed in two different ways depending on the different types of life forms: In amoeboid cells a broad and rather short ectoplasmic lobopodium develops from with a slender filose pseudopodium arises. The lobopodium gradually tapers and takes part in the formation of the filose pseudopodium. In the planktonic life form a filose pseudopodium may be formed without any prior lobopodial extension, the whole process is completed within a few seconds. Retraction of a filose pseudopodium also shows some variations. Refolding of distal parts of the pseudopodium is usually involved in the retraction process ("en bajonette"-retraction). At the contact zone between the refolded part and the main part of the pseudopodium a small granule is formed. Granules only move to the cell surface and not in distal direction (retraction by "candling"). Several granules may be formed simultaneously and during proximal movement often fuse with each other. With phase contract microscopy no axial filament was seen in filose pseudopodia. During movement of amoeboid cells filose pseudopodia attach to the substrate and gradually shorten without development of granules, the cell body is thereby passively moved. In about 5-10 sec. a distance is covered which approximates the length of the amoeba. During movement the amoeba exhibits polarity, the filose pseudopodia at the anterior end of the cell are usually more numerous than at the posterior end. At both sides of the amoeba only few filose pseudopodia are formed. A change of moving direction is initiated by a sudden development of new filose pseudopodia at a particular place on the cell surface. The free floating form is not only passively distributed by currents present in the culture medium, but the amoebae are probably able to regulate their sinking rates actively. This suggestion is based on the observation that amoebae are referentially planktonic if the food organism is planktonic, or move along a substrate, if the food organism accumulates at the bottom of the culture vessel. How the sinking rate is regulated is unknown, but an involvement of the filose pseudopodia in this process seems likely. (ref. ID; 654)
  • Life cycle: In culture Vampyrellidium perforans reproduces by binary fission only. Sexual stages have not been observed. Mitosis has not been followed but cell division starts by vacuolization of cytoplasm and development of an oval cell shape. Within 5-20 min two daughter cells have separated. They are often still connected by a long, thin cytoplasmic strand. Cell division may lead to equal or unequal daughter cells. Fusion of two or three amoebae to form plasmodia was occasionally observed. The primary events of this process include establishment of contact between filose pseudopodia of different amoebae. The pseudopodia fuse at their tips and then shorten. Eventually the cells surfaces of both amoebae touch and the plasma membranes fuse. The nuclei can approach each other in the plasmodium, but a fusion of nuclei was never observed. The further fate of a plasmodium has not been followed. Temporary food plasmodia were more often found, the individual cells separate when leaving the exhausted food. (ref. ID; 654)

    Remarks

    Vampyrellidium perforans is unlike Nuclearia moebiusi because it has a perinuclear striated band and cytoplasmic microtubules, and it produces massive pseudopodia. A striated band is present in N. simplex (Mignot and Savoie 1979) and probably also in N. radians (also referred to as Nucleosphaerium tuckeri and Nucleosphaerium radians (Cann 1986; Cann and Page 1979). Despite the presence of the band, N. simplex has no cytoplasmic microtubules (Mignot and Savoie 1979). This feature was not mentioned in a recent description of the type species of the genus Nuclearia (Cann 1986). Because of these similarities between V. perforans and various members of the genus Nuclearia, we conclude that these genera are closely related and that they should be classified together. For the moment, it seems appropriate to place all amoebae with filose pseudopodia and flattened mitochondrial cristae within the family Nucleariidae. On the basis of the information available to date, the nucleariid filose amoebae comprise at least four genera (Nuclearia sensu Patterson (1984), Pinaciophora, Pompholyxophrys, and Vampyrellidium). Pompholyxophrys and Pinaciophora can be easily distinguished by the siliceous artifacts that make up the periplast ensheathing the cell body (Patterson 1985). On the basis of the information derived from a small number of species, it would be appear that Vampyrellidum differs from Nuclearia because it can feed by penetration, has cytoplasmic microtubules, and is able to form massive pseudopodia. More work is needed to determine whether these features are consistent within the two genera. The ability of filose amoebae to feed on algal cells by penetration has apparently arisen independently among the nucleariid and vampyrellid amoebae. Confusion between Vampyrella and Vampyrellidium is understandable, especially as both genera use specialized pseudopodia during the breakdown of the algal cell wall (Hulsmann 1982; Surek and Melkonian 1980). This may be linked to a need to apply lytic enzymes to the cell wall so that it may be breached. Despite the similarities in appearance by light-microscopy and feeding behavior, the ultrastructural differences have revealed that these traditional criteria are unreliable. Many of the species studied previously by light-microscopy alone are in need of re-investigation to clarify their taxonomic position. (ref. ID; 4256)

    Type locality

    Freshwater, feeding on Chlamydomonas cribrum Ettl in Loughrigg Tarn, Lake District (England) in April 1977. (ref. ID; 654)