Paraphysomonas Stokes, 1885 (ref. ID; 3814), (Kent) De Saedeler, 1929 (ref. ID; 4656) or De Saedeleer, 1929 (ref. ID; 4907, 4921, 5772)
Order Stramenopiles Patterson, 1989 (ref. ID; 4907)
Straminopiles: Chromulinales Pascher, 1912 (= Chromomonadina Klebs, 1893) (ref. ID; 5772)
Paraphysomonadaceae (ref. ID; 7657)

Synonym Physomonas (ref. ID; 3814)

[ref. ID; 3814]
The genus Paraphysomonas Stokes contains colorless flagellates with a long tinsle flagellum, a short whiplash flagellum, and silicified scales. The genus was first described in 1885 Stokes (as Physomonas) and until 1967, a single species, P. vestita, characterized by scales with a circular base plate supporting a central spine, had been described. It has been shown since, by electron microscopy, that there are many more species of Paraphysomonas all distinguished primarily by different scale types. With the exception of the large scale of P. vestita, the other species have scales near or beneath the resolution of the light microscope. (ref. ID; 3814)

[ref. ID; 4907]
Solitary heterokont cells with two unequal flagella. The short smooth accessory flagellum is often hardly visible by light microscopy. Cells of Paraphysomonas and Spumella are similar, but Spumella is naked, while Paraphysomonas is surrounded by siliceous scales In most cases Spumella and Paraphysomonas can only be distinguished by electron microscopy (Preisig & Hibberd, 1982). (ref. ID; 4907)

[ref. ID; 5772]
Biflagellate, heterokont flagellates, possessing a cell body covered with siliceous scales (Preisig, Vors & Hallfors 1991)(ref. ID; 5772)


Paraphysomonas antarctica Takahashi, 1987 (ref. ID; 5772)
Remarks; This species is a member of the "imperforata complex." The scales resemble those of P. imperforata sensu stricto, but according to Takahashi (1987) they differ in three respects: 1) the diameter of the basal plate and the length of the spines are twice as great as those of P. imperforata; 2) the ratio of the length of the spine tip to the length of the total spine is 1/4.6 (1/4.6 arrow 0) compared to 1/2 (1/2 arrow 1) in P. imperforata; 3) the thickness of the spine at the transition zone between the tip and the main part of the spine changes abruptly, instead of gradually as in P. imperforata. These distinctions are only valid on the condition that the large-scaled forms of P. imperforata sensu lato are transferred to other species (Takahashi 1987). The smallest scales of the cells of P. antarctica from Belize are generally much smaller than previously reported (Takahashi 1987). This invalidates Takahashi's distinction No. 1. The finding of intermediate scale types, which fit the size range given for P. imperforata sensu stricto, but that have spines with an abrupt change in thickness, a characteristic for P. antarctica, invalidates Takahashi's distinction No 3. The dimensions of the scales of the specimens from Belize may cover both P. antarctica and P. imperforata sensu stricto. This "polymorphy" may be exhibited by the scales of a single cell. All scales may, however, be referred to P. antarctica strictly following Takahashi's distinction No. 2. At present, this distinction is the only criterium on which P. antactica may be separated. Paraphysomonas antarctica has previously been reported only from cold seawater and sea-ice, and the scales of the cold-water specimens were found to be in close agreement with the description (Vors 1992, 1993). It is interesting to note that the present aberrant specimens of P. antarctica and P. imperforata originate from warm-water cultures (20 degrees C), indicating that the temperature may influence the size of the scales. (ref. ID; 5772)
Previous records (marine): Known from temperate, arctic and antarctic sites (Vors 1992). (ref. ID; 5772)
Paraphysomonas erinacea Stefanova & Kalina, 1992 (ref. ID; 4822 original paper)
Diagnosis; Cells motile, spherical, solitary living, 12.7-13.6 um in diameter (according to dried preparation), covered with two types of scales. Plate-scales elliptic without ornamentation, 3.5 x 2.2 um in size. Spine-scales with circular basal disc, 1.5-1.8 um in diameter. On the disc is one deep indentation. Spines straight or bent, tapered, 6-7 um long. (ref. ID; 4822)
Comments; P. erinacea sp. n. differs from P. vestita and P. imperforata by the existence of two scale types. The two mentioned species have only one type of scales. (ref. ID; 4822)
Type locality; Rarely in plankton sample collected in Mach's basalt quarry near Semily town (Eastern Bohemia), April 1991, water temperature 10 degrees C, pH 8.2. (ref. ID; 4822)
Paraphysomonas cf. homolepis Preisig & Hibberd (ref. ID; 4822)
Description; Only single plate-scale was found. Scale flat, lace-like with concentric rows of apertures, 0.6 um in length. (ref. ID; 4822)
Comments; Similar scale was described for P. butcheri Pennick & Clarke, 1972. (ref. ID; 4822)
Paraphysomonas imperforata Lucas, 1967 (ref. ID; 3814, 4907, 5772) reported year? (ref. ID; 4878, 7657)
Description; See P. vestita. (ref. ID; 3814)
Remarks; Paraphysomonas imperforata is a well studied and extremely polymorphic species (Preisig & Hibberd 1982; Takahashi 1987). The size values of the specimens from Belize have been included for comparison with P. antarctica from the same locality. (ref. ID; 5772)
Previous records (P. imperforata sensu lato); Widespread in fresh and marine waters at arctic, antarctic, temperate, and sub-tropical sites (Takahashi 1987). (ref. ID; 5772)
Measurements; Scales 1.1-2.0 um diam., spines 2.0-7.4 um long. (ref. ID; 7657)
Paraphysomonas pileata Stefanova & Kalina, 1992 (ref. ID; 4822 original paper)
Diagnosis; Cells motile, solitary living, covered with three types of scales. Plate-scale (1) elliptic with smooth rim and one axial rib, inner scale area with net-like structure of irregular meshes. Scale size: 5.1 x 3.1 um high, margin 0.25 um wide. Hollow cup-shaped (2) scales with fairly circular base provided with smooth margin and conically shaped upper part with knob-like tip is formed of net-like material. Cup-shaped scale size: 2.6-3.2 um high, about 3 um diameter of base. Spine-like scales (3) with conical basal part run out in 15.5 um long spine with knob-like tip. (ref. ID; 4822)
Comments; P. pileata is not similar to any other Paraphysomonas species. Cup-shaped scales of P. cancellata Preisig & Hibberd differ in shape and structure. (ref. ID; 4822)
Type locality; Rarely in plankton sample collected in Mach's basalt quarry near Semily town (Eastern Bohemia), May 1991, water temperature 10 degrees C, pH 8.7. (ref. ID; 4822)
Paraphysomonas punctata Zimmermann (ref. ID; 7657)
Measurements; Scale 1.5-1.8 um. (ref. ID; 7657)
Paraphysomonas cf. vestita De Saedeleer, 1929 (ref. ID; 4907)
Description; Cells 11-14 um long, solitary, very plastic: roundish - ovate - cylindrical, surrounded by numerous delicate spine-scales about 9 um long visible by light microscopy. Two heterodynamic flagella: one curved about 30 um long, and one short up to 5 um long. Nucleus anterior, one lateral contractile vacuole. Cells either attached to substrate - and then more or less round in shape - with long flagellum beating fast, or swimming with long flagellum directed forward in an arc. Swimming flagellates often become elongated. In dying specimens with a low frequency of beating the long flagellum clearly beats with a sine wave. (ref. ID; 4907)
Comments; The only species in the genus with spines visible by light microscopy are P. vestita, P. imperforata Lucas 1967, P. gladiata Preisig & Hibberd 1982. P. vestita usually differs from the two latter because of its larger size - 10-25 um vs. 2-8 um - (Hanel 1979; Thomsen 1975; Preisig & Hibberd 1982; Vors 1992) and because the scales are clearly visible by light microscopy in P. vestita, while frequently they are barely visible in P. imperforata and P. gladiata (Lucas 1967; Tong, pers, com.). However since species distinction in Paraphysomonas is based exclusively on scale morphology (Preisig & Hibberd 1982, 1983), the observed form is only assigned tentatively to P. vestita. (ref. ID; 4907)
Paraphysomonas vestita Stokes, 1885 (ref. ID; 3814) or (Stokes) De Saedeler, 1929 (ref. ID; 4656) reported year? (ref. ID; 4822, 4878), (Stokes) De Saedeleer (ref. ID; 7657)
Syn; Monas vestita (Stokes) Reynolds (ref. ID; 4656); Physomonas vestita Stokes (ref. ID; 4656)
Description; Paraphysomonas vestita has a long tinsle (flimmer) flagellum (40 um) covered with mastigonemes, each with 2 hair points. The 2nd flagellum is much shorter (6 um), curved, and without appendages. Many scales surrounded the cell. Each scale is composed of a circular base plate (1.5-2.5 um in diameter) from which arises a long (4-9 um) central spine. The cells have a nucleus in the anterior part beneath the basal bodies of the flagella. The single large Golgi complex is located to one side of the nucleus. Both the perinuclear space and the Golgi frequently contain promastigonemes. A food vesicle with bacteria is located in the posterior region of the cell. Scale-containing vesicles, mitochondria, ribosomes, and an occasional lipid body also are found in the cytoplasm. (ref. ID; 3814)
[Formation of scales]: Scale production is initiated by 2 plate-like cisternae of endoplasmic reticulum (ER) which come to lie one above the other. The ER cisternae have ribosomes attached to the outside of their membranes, although as scale production proceeds the membranes become smooth. One of the 2 cisternae becomes the scale-containing vesicle, while the other appears to mold the scale-containing vesicle into the shape of the mature scale. The vesicle that dose not contain the scale migrates into the center of the future scale-containing vesicle, causing the latter to assume the shape of a scale, with a circular base plate and a hollow spine. The vesicle that contains no scale actually pushes up through the center of the spine to its tip. This vesicle appears to be consumed as it pushes itself up the center of the spine, thus less of it is left at the base. Silicon is then laid down, in association with fibrillar material, within the scale-containing vesicle which has been molded into the shape of the mature scale. The process results in the scale having a small hole in the center of the base plate beneath the spine which can be seen when the spine is broken from the base plate in dried preparations. Fully formed scales are nearly as long as the diameter of the cell. These scales within the vesicles are then moved to the outside of the cell. It was simply stated in earlier papers on Paraphysomonas that the scales arose in vesicles (Manton & Leedale 1961) or that they arose in Golgi vesicles (Lucas 1968). One reported contained a speculation that they originated in vesicles derived from the ER, in a manner similar to the formation of silicified scales in the Chrysophycean alga, Synura (Leadbeater 1972). The authors of the aforementioned papers were working with material either collected in the wild mixed with other organisms, or with cell occurring as contaminants in culture of another alga. These conditions resulted in only a few cells being observed in thin sections. That the scales do not arise in Golgi vesicles can be deduced from the following observations: (a) the Golgi vesicles are frequently filled with promastigonemes, but promastigonemes are never seen in the scale-containing vesicles; (b) the scale-containing vesicles have ribosomes on the outside of the membranes as does the rough ER; (c) the scale-containing vesicles are found throughout the cytoplasm, not only in the area of the Golgi complex. The method of scale formation in Paraphysomonas is similar to that in Synura, except that in the latter genus the molding force for the scale-containing vesicle comes from the chloroplast ER instead of an ER vesicle as in Paraphysomonas. (ref. ID; 3814)
Cells solitary, colourless, having one type of scales. Spine-scales with circular plate of thicker margin and with tapered hollow spine running out from plate centre. Plate diameter about 2 um, spine length 3 um. (ref. ID; 4822)
Comments; [Salinity tolerance]: Utilizing a synthetic seawater mix (Rilamix, Carolina Biological Supply), P. vestita was found to be capable or euryhaline growth in salinity ranging from near that of distilled water (distilled water plus nutrient) to 91 o/oo (2.6 x seawater). While being viable at the upper limit of the range, the cells often became immobile. The euryhaline nature of P. vestita, previously suspected from the finding of P. vestita scales, but not whole cells, in brackish water, seawater, and fresh water, raises the question of the validity of the species P. imperforata. When Lucas described P. imperforata in 1967, P. vestita has only been reported from fresh water and was presumed to occur only in the freshwater environment. On finding cells similar to P. vestita, but somewhat smaller and with a narrower range of scale dimensions, in seawater, Lucas described a new species. Subsequently Thomsen (1975) showed that the scale-to-spine ratios of P. imperforata were well within those of P. vestita, invalidating the taxonomic value of this characteristic. Thomsen also stated that the spine width in P. imperforata changed abruptly near the tip, becoming thinner, a characteristic shown in one of Lucas's micrographs, but not commented on in his description of P. imperforata. In lucas's photomicrographs only a small portion of the scales appear to have this characteristic, the remainder being similar to those of P. vestita. In a photomicrograph of scales of P. imperforata from Japan (Takahashi 1976) there is no thinning of the spine at the tip. It is questionable whether a minor feature such as this justified the separation of the organisms into 2 species and, therefore whether P. imperforata should be regarded as a form of P. vestita; the trivial name "imperforata" would then become a synonym of "vestita". Takahashi (1976) described a P. vestita with somewhat different scales as a form of the species. (ref. ID; 3814)
Measurements; Scales 1.9-2.7 um diam., spines 4.3-9.0 um long. (ref. ID; 7657)