Raphidocystis
Raphidocystis Penard, 1904 (ref. ID; 3691 original paper) or Penard emend. Nicholls & Durrschmidt (ref. ID; 4884)
Subclass Centrohelidia: Heliozoa (ref. ID; 7574)
Synonym Choanocystis Penard, 1904 (ref. ID; 3541)
[ref. ID; 1618]
Spicules of various forms. (ref. ID; 1618)
[ref. ID; 4884]
Emended diagnosis; Centrohelid heliozoa with the periplast comprising three types of scales: straight tubular or trumpet-like scales, smaller funnel-shaped scales, and elliptical or subrectangular plate-scales. Plate-scales have a conspicuously broad peripheral rim, an either smooth or patterned central area and a well-developed or vestigial median rim. Some remarks must be done about the type-species of Raphidocystis - R. lemani Penard. This species was described by Penard (1902) as lacking plate-scales in the periplast. However, there are not known acanthocystids of raphidiophryids lacking plate scales. Some specimens of R. lemani were observed by the author on the Kuybishev water reserve (central Russia). They have very few plate scales with reticulate surface similar to R. tubifera. We consider Penard did not observe its plate-scales because they are very few. (ref. ID; 4884)
- Raphidocystis glutinosa Penard, 1904 (ref. ID; 3541, 3691 original paper)
- Raphidocystis infestans Wetzel, 1925 (ref. ID; 1618)
- Raphidocystis lemani Penard, 1891 (ref. ID; 3541, 3691)
Syn; Acanthocystis lemani Penard, 1891 (ref. ID; 3541) reported year? (ref. ID; 3691); Acanthocystis lemani var. plonensis Zacharias, 1894 (ref. ID; 3541) reported year? (ref. ID; 3691); Heterophrys pavesii Garbini, 1898 (ref. ID; 3541) reported year? (ref. ID; 3691); Raphidocystis lemani Penard, 1904 (ref. ID; 3541)
- Raphidocystis lepidula (Penard, 1904) Rainer, 1968 (ref. ID; 3541 redescribed paper)
Syn; Choanocystis lepidula Penard, 1904 (ref. ID; 3541)
- Raphidocystis simplex (Schaudinn, 1897) (ref. ID; 3691) or 1898 (ref. ID; 3541)
Syn; Acanthocystis simplex Schaudinn, 1898 (ref. ID; 3541) reported year? (ref. ID; 3691); Raphidocystis simplex Penard, 1904 (ref. ID; 3541)
- Raphidocystis stellata Penard, 1904 (ref. ID; 3541, 3691 original paper)
- Raphidocystis tubifera Penard, 1904 (ref. ID; 3541, 3691 original paper, 4710, 7574) reported year? (ref. ID; 1618, 4878)
Descriptions
Thin axopodia twice the body diameter; without radial spicules; feeds on ciliates. (ref. ID; 1618)
Measurements
Body 20-40 um in diameter. (ref. ID; 1618)
Raphidocystis tubifera Penard, 1904 (ref. ID; 3541, 3691 original paper, 4710, 7574) reported year? (ref. ID; 1618, 4878)
Descriptions
Spicules tubular with enlarged extremity; fresh water. (ref. ID; 1618)
[ref. ID; 7574]
- Morphology of the scales. Raphidocystis tubifera produces scales of three distinct types: long narrow scales resembling straight trumpets (type S1), shorter funnel-shaped scales (type S2) and flat oval scales (type S3). The S1 scales are tubular and taper gradually from a flared open end to a narrow closed end which is usually slightly globular; these scales vary between 15 um and 25 (+) um in length, the main tubular part being typically 0.3-0.6 um in diameter; they lack surface pattern but display fine serrations at the flared end. These S2 scales also appear slightly globular at the closed end; their open ends are circular, 2.5-3.5 (+) um in diameter and the scales vary in length from 2.5 to 4.5 um, the Canadian examples being the longest. These scales are composed of a reticulate material, and a distinct rim surrounds the open end; in section this portion of the scale is seen to be hollow and reflexed. The S3 scales are oval, 5.0-6.0x2.5-3.0 um, and are composed of a similar reticulate material to the S2 scales; each scale has a fine longitudinal midrib and a thickened rim which can be shown from sectioned material to be hollow and raised on one face of the scale only, allowing "upper" and "lower" surfaces to be distinguished by SEM. These scales may be identified as belonging to Raphidocystis tubifera from the works of Penard (1904) and Rainer (1968). (ref. ID; 7574)
- Distribution of scales on the cell surface. The long S1 scales extend radially from the cell with their flared ends outermost while the scales of the two remaining types form a dense layer closer to the cell through which the S1 scales project. With SEM, the external surface of this dense layer can be seen to be made up from the open ends of S2 scales which are, therefore, oriented with their closed ends towards the cell membrane. Evidence from dissociating scale cases and from sections suggests that the flat S3 scales are located, rim outermost, between the cell membrane and the S2 layer, although such an arrangement cannot be directly observed from whole cells. Individuals of R. tubifera from our sites typically bear 50-100 (+) S1 scales, although occasional cells in both British and Canadian material appeared to lack S1 scales entirely. S2 scales are difficult to count using LM or TEM but the SEM micrograph suggests that these number well over 100 per cell. The S3 scales are also numerous but their number is more difficult to estimate. (ref. ID; 7574)
- Appearance of living cells in the light microscope. In fresh collections, cells of R. tubifera appear as free-floating colourless spheres surrounded by radiating axopodia; the latter are sensitive to disturbance and are usually retracted on addition of a coverslip to a fresh preparation. Without flattening the cell, only the S1 scales are distinct although the dense layer corresponding to the S2 and S3 scales may also be seen. The protoplast typically measures 10-25 um in diameter and the S2/S3 layer has a thickness of ca. 5 um. In flattened preparations, details of individual scales become visible and the distribution of the three types is apparent. The use of phase optics allows the principal cell contents to be seen: these include the excentric nucleus and the central granule (centriaster) characteristic of Heliozoa in the subclass Centrohelidia. (ref. ID; 7574)
Remarks
Previous descriptions of R. tubifera (Penard 1904; Rainer 1968) have included drawings based upon light microscopy only. Penard remarked that the S1 scales (-aiguilles tubulaires-) were difficult to discern except in dried preparations; with phase or interference contrast, however, they are visible on the cell in life. The S2 scales are not included in the type illustration (Penard 1904, p.194) although their presence is noted in the accompanying text. Rainer, on the other hand, depicts all the three scale types. Diameters of cells excluding the scale covering are given as 18 um (Penard) or 10-27 um (Rainer), which are in agreement with those of the present specimens. Penard describes long (S1) scales 13 um in length and oval (S3) scales 7x3 um; Rainer describes oval scales 6-8x3-4 um and depicts S1 scales up to 18 um long. Our S1 scales are thus somewhat longer than those previously reported. (ref. ID; 7574)
Examined material
Samples of surface water which yielded material of R. tubifera were collected by A.J.J.R. and G.F.L. from Sawley Dene, North Yorkshire, England (Grid Ref. SE 263667) in August and October 1976 and October 1977, at temperatures of 12-20 degrees C and pH 7.9-8.2, and by D.A.D. from Callanan Lake, Cariboo District, British Columbia, Canada (lat. 52 degrees 07'N, long. 122 degrees 35'W) in July and October 1978, at temperatures of 18.8-19.6 degrees C and pH 8.35-8.80. (ref. ID; 7574)
Measurements
Diameter about 18 um; envelope 25 um. (ref. ID; 1618)