Raphidiophrys

Raphidiophrys Archer, 1867 (ref. ID; 3691, 4758) or (Archer, 1867) Mikrjukov, 1996 (ref. ID; 4884 emended paper)

Actinopoda: Heliozoea (ref. ID; 4758)
Heliozoa: Centrohelida (ref. ID; 7658)

Synonym Sphaerastrum Greeff, 1873 nec Archer, 1876 (ref. ID; 3541)
See Rhaphidiophrys

[ref. ID; 1618]
Spherical; mucilaginous envelope with spindle-shaped or discoidal spicules which extend normally outwards along pseudopodia; nucleus and endoplasm eccentric; solitary or colonial; fresh water. (ref. ID; 1618)

[ref. ID; 1923]
Nucleus eccentric, generally a central corpuscle from which the axial filaments arise. Spicules scattered through the envelope, surrounding the base of the pseudopodia. (ref. ID; 1923)

[ref. ID; 4884]
Emended diagnosis; Centrohelid heliozoa with a periplast comprising one or several types of flat siliceous elements (scales). These are directed mainly in tangential direction and formed by two parallel plates connected by radial internal septae, which are seen in SEM as radial striations or ribs. Radial elements are absent in the periplast. Six species are known. (ref. ID; 4884)
Remarks; The genus seems to be rather homogeneous. A complex of species characters was formulated by Siemensma & Roijackers (1988). Discussing about centrohelids with only siliceous tangential elements in the periplast (Raphidiophrys sensu lato) we ought to pay attention to the remarkable similarity in the scale morphology between those with reticulate (P. symmetrica and P. ambigua) or smooth (P. marginata) surface and plate scales of Raphidocystis species (Rees et al. 1980; Nicholls & Durrschmidt 1985). The latter genus has two types of radial elements in the periplast (funnel-shaped and trumpet- or tube-like) besides ones mentioned above. However, after the revision of Siemensma (1991) the members of Raphidocystis, to our point of view, comprise two distinct groups. The first group includes three species of true Raphidocystis with plate-scales surrounded by a broad hollow marginal rim formed by twisted peripheral parts. Two of these species have plate-scales with reticulate upper surface identical to scales of P. symmetrica, while plate-scales of the third species have smooth surface and are similar to scales of (ii)-group of the genus Polyplacocystis. Radial elements of Raphidocystis are represented by two types: funnel-shaped and trumpet- or tube-like ones; funnel-shaped elements are surrounded by a hollow rim similar to that around plate-scales. This group includes a type-species of the genus -R. lemani Penard and two species: R. tubifera Penard and R. glabra Durrschmidt. The other part of the genus was introduced by Siemensma (1991). It includes three species described by Durrschmidt as Acanthocystis lacking the shaft. However, they differ from true Raphidocystis by i) flat plate scales, which are characteristic for the third centrohelid family Acanthocystidae Claus and ii) only one type of usually asymmetrical radial elements. We consider that these three species (R. glutinosa, R. flabellata and R. umbraculiformis) must be returned to the family Acanthocystidae as members of a new separate genus with radial elements lacking a shaft. So, we support the emended diagnosis by Nicholls & Durrschmidt (1985) but not of Siemensma (1991). (ref. ID; 4884)
Type species; Raphidiophrys viridis Archer, 1867 (ref. ID; 4884)

[ref. ID; 7350]
Raphidiophrys is known to possess a spherical cell body and a centroplast which is present in the central portion of the cytoplasm (Tilney 1971). Bundles of microtubules radiate from the centroplast and form axopodial axonemes. Each axoneme passses through the cell body and reaches to the tip of an axopodium. The axonemal microtubules are linked firmly to one another by cross-bridges forming a regular pattern. (ref. ID; 7350)

Raphidiophrys ambigua Penard, 1904 (ref. ID; 3541, 3691 original paper, 4758) reported author and year? (ref. ID; 4009)
Raphidiophrys bruni Penard, 1903 (ref. ID; 3541), brunii Penard, 1903 (ref. ID; 3691)
Raphidiophrys capitata Siemensma & Roijackers, 1988 (ref. ID; 4758 original paper) reported author and year? (ref. ID; 4884)
Raphidiophrys coerulea Penard, 1904 (ref. ID; 3541, 3691 original paper)
Raphidiophrys conglobatum (Greeff, 1873) Penard, 1905
See; Raphidiophrys elegans Hertwig & Lesser, 1874 (ref. ID; 3541)
Raphidiophrys contractilis Kinoshita, Suzaki, Shigenaka & Sugiyama, 1995 (ref. ID; 7350 original paper)
Raphidiophrys elegans Hertwig & Lesser, 1874 (ref. ID; 3541, 3691, 4731) reported year? (ref. ID; 1923, 3497) or Hertwig & Lesser, 1874 sensu Penard, 1904 (ref. ID; 4758) reported author and year? (ref. ID; 4884)
Syn; Raphidiophrys conglobatum (Greeff, 1873) Penard, 1905 (ref. ID; 3541); Raphidiophrys orbicularis Nicholls, 1985 (ref. ID; 4758); Sphaerastrum conglobatum Greeff, 1873 (ref. ID; 3541); Sphaerastrum fockei Doflein, 1909 nec Archer, 1876 (ref. ID; 3541)
Raphidiophrys glomerata Penard
See; Raphidiophrys viridis (ref. ID; 3691)
Raphidiophrys infestans (Wetzel, 1925) Rainer, 1968 (ref. ID; 3541 redescribed paper)
Syn; Raphidocystis infestans Wetzel, 1925 (ref. ID; 3541)
Raphidiophrys intermedia Penard, 1904 (ref. ID; 3541, 3691 original paper, 4731, 4758) reported author and year? (ref. ID; 4884)
Raphidiophrys magna O'Donoghue, 1921 (ref. ID; 3541)
Raphidiophrys marginata Siemensma, 1981 (ref. ID; 4758, 7658)
Raphidiophrys marina Ostenfeld, 1904 (ref. ID; 3541, 7658 redescribed paper)
Raphidiophrys minuta Nicholls, 1985 (ref. ID; 4731) reported author and year? (ref. ID; 4884)
Raphidiophrys orbicularis Nicholls, 1985
See; Raphidiophrys elegans (ref. ID; 4758)
Raphidiophrys ovalis (Durrschmidt, 1985) Siemensma & Roijackers, 1988 (ref. ID; 4758 redescribed paper) reported author and year? (ref. ID; 4884)
Raphidiophrys pallida Schulze, 1874 (ref. ID; 3541, 3691, 4731, 4758, 7658) reported year? (ref. ID; 1618) reported author and year? (ref. ID; 5388)
Raphidiophrys schaudinni Burger, 1908 (ref. ID; 3541)
Raphidiophrys socialis Leidy, 1883 (ref. ID; 3541, 3691)
Raphidiophrys symmetrica Penard, 1904 (ref. ID; 3541, 3691 original paper, 4731, 4758, 4878)
Raphidiophrys viridis Archer, 1867 (ref. ID; 3541, 3691, 4758)
Syn; Raphidiophrys glomerata Penard (ref. ID; 3691)

Raphidiophrys ambigua Penard, 1904 (ref. ID; 3541, 3691 original paper, 4758) reported author and year? (ref. ID; 4009)

Descriptions

Scales of different shapes; ovate, elongately ovate and fusiform. The scales have a reticulate structure. (ref. ID; 4758)

Raphidiophrys capitata Siemensma & Roijackers, 1988 (ref. ID; 4758 original paper) reported author and year? (ref. ID; 4884)

Diagnosis

Scales elliptical, elongated, with rounded, often capitate poles; scale plates fuse peripherally with strongly inflexed sharp-edged rims; poles sometimes covered by a thin lamella; scales 6-14x2-4 um, with a L/B-ratio of 3.0-5.4; scales with internal radiating septa; number of septa along de border varying from 30 to 60-70 per um; edge of the scales strongly inflected. The colonies showed clusters of ca. 30 individuals. The cell diameter of colonial and solitary individuals varied between 25 and 50 um. Axopods were long and abundant, up to 170 um long. The scales are long-elliptical, compared to those of R. intermedia. The scales are half the width of those belonging to R. intermedia and R. elegans. The general appearance of the scale is that of a boat; it has slight convex sides. Often the poles are clearly capitate, which gave the specific epithet. The poles are normally rounded. Widened, somewhat blunt pores are nor rare. Both poles are often covered by a thin membrane, thus resembling a slipper. In cross section the scales show a crescent form. Numerous septa connect the upper with the lower plate of the scales. They radiate from the central axis. (ref. ID; 4758)

Remarks

The specimens, reported by Nicholls and Durrschmidt (1985) as R. elegans, undoubtedly belongs to this species. The scales drawn by Rainer (1968) and described as belonging to the solitary form of R. elegans probably represent scales of R. capitata. Calculations from his pictures gave a scale size of 9.0x3.5 um, which agrees with our results. (ref. ID; 4758)

Type locality

Collected both in Sweden and the Netherlands. (ref. ID; 4758)

Raphidiophrys contractilis Kinoshita, Suzaki, Shigenaka & Sugiyama, 1995 (ref. ID; 7350 original paper)

Descriptions

The present species has a spherical cell body and a number of axopodia radiating from the cell surface. As is characteristic of the centrohelid heliozoans, a centroplast was present in the center of cell body, and a nucleus was located near the periphery of the cytoplasm. This species usually lives solitary. However, when there is large increase in cell number in a culture dish, 100-300 organisms often gather to form a colony. When the cells make such a colony, the axopodia tend to become interconnected firmly to those of the neigbouring organisms, and the colony cannot be reduced to single cells by a simple pipetting. It is known that the cells to Raphidiophrys elegans always form colonies, in which adjacent cells are linked by special cytoplasmic bridges (Hertwig and Lesser 1874; Page and Siemensma 1991). In the present species, however, such connecting bridges were not observed. The diameter of the cell body in the present species (n=250) was found to vary from 7 to 19 um (14.2 um in average) with the largest number in the range between 12 and 14 um. Axopodial length was between 60 and 110 um, and 84 um on the average. The axopodia contained many granular kinetocysts. Finally, it is featured by that so-called mucus sheath does not typically develop around the cell body of the present species. (ref. ID; 7350)

Remarks

Pattern of axonemal microtubules: The present heliozoans has a centroplast which functions as a microtubule organising center, from which the axonemal microtubules extend radially. The pattern of microtubules was a complex of hexagons and triangles, possibly linked by regulary-located cross-bridges. From this morphological feature, possible genus names for the present heliozoan would be restricted to either Raphidiophrys, Acanthocystis or Heterophrys (Bardele 1975, 1977; Page and Siemensma 1991; Tilney 1971) (ref. ID; 7350)
Structure of cell surface-coating scales: The cell body of the present species was found to be surrounded by a thin layer of scales when observed with Nomarski interference optics. Acanthocystis (Page and Siemensma 1991; Siemensma 1981; Siemensma and Roijackers 1988) and Heterophrys (Bardele 1973; Page and Siemensma 1991) are known to have needle-like structures called spicules around the cell body. In the present heliozoans, however, we could not observe any cell-coating structures other than the scales, indicating that the present species belongs to the genus Raphidiophrys. Scales of Raphidiophrys are generally elliptic, nearly circular or long spindle-shaped, sometimes with curved edges, and their size and surface patterns are considered to be important in classifying the species of the genus Raphidiophrys (Page and Siemensma 1991; Siemensma and Roijackers 1988). According to Nicholls and Durrschmidt (1985) and Page and Siemensma (1991), the scales of Raphidiophrys can be separated into three groups featured by (A) meshed patterns, (B) pattern of wavy, radiating ridges and (C) no typical pattern. By electron-microscopic observation, the shape of the scale was found to be oblong, resembling the shape of a rubber boat, without any typical patterns on its surface. The size of the scales was measured as 2.2-7.5 (long axis, L) x 1.1-2.6 (short axis, S) um with L/S ratio usually between 2.0-2.6, sometimes up to 3.0. Observations with ultrathin sections showed that the scale was composed of a single plate with curved edges, resembling a dish. The convex surface of the scale always faces towards the cell body, which is also shown by scanning electron micrograph. It has been documented earlier that the scales of the genus Raphidiophrys are "siliceous" (Rainer 1968), but no chemical examination has been reported. In order to clarify the elemental composition of the scales, X-ray microanalysis was carried out. The carbon-coated scales showed a very high level of silicon signal compared to those for other elements, indicating that the scales of this heliozoan species are silicic. Among various species of Raphidiophrys, R. marginata (Page and Siemensma 1991; Siemensma 1981) seems to be most closely related to the present species, as the scale of R. marginata is similar in shape (oblong shape with L/S ratio of 1.9-2.6) and has no typical pattern on its surface (Nicholls and Durrschmidt 1985; Page and Siemensma 1991; Siemensma 1981; Siemensma and Roijackers 1988). However, the scales of R. marginata are reported to have rounded poles (Nicholls and Durrschmidt 1985; Page and Siemensma 1991) which are absent in the present species. In addition, when the sizes of the scale and the cell body are compared, those for the present species (scale size: 2.2-7.5x1.1-2.6 um, cell size: 7-19 um) are much smaller than R. marginata (scale size: 5.9-10.0x2.5-3.9 um, cell size: 25-30 um) (Nicholls and Durrschmidt 1985; Siemensma and Roijackers 1988). These facts led us to conclude that the present species is a new species belonging to the genus Raphidophrys. Compared with other known species, this species is one of the smallest members of the genus Raphidiophrys. (ref. ID; 7350)
Rapid axopodial contraction: The axopodial contraction was often observed when a food flagellate attached to the tip of an axopodium, and the axopodium shortened instantaneously to about one quarter of its initial length. The process of axopodial contraction in the present species of Raphidiophrys was examined by monitoring the distance between a food flagellate, C. elongatum, and the cell surface of the heliozoan. Measurements were made at intervals of 1/30 sec from a video recording. In this example, the prey attached to the tip of an axopodium and stopped swimming at about 270 msec after the onset of the observation. The axopodial contraction started with a delay of 70 msec after apparent attachment of the prey, and the contraction was recorded in just one or two frames of the video recording, thus the velocity of contraction is considered in the order of 1 mm/sec, similar to the value reported for Echinospharium (Ando and Shigenaka 1989; Matsuoka et al. 1986; Shigenaka et al. 1982; Suzaki et al. 1980, 1992) and Actinophrys (Kinoshita et al. 1993). No such contactile axopodial behaviour has been reported so far for any existing species in the genus Raphidiophrys. (ref. ID; 7350)

Etymology

The present new species was named Raphidiophrys contractilis after this characteristic behavior of its axopodia. (ref. ID; 7350)

Type specimens

Type specimens of the present new species can be obtained directly from Dr. T. Suzaki, Laboratory of Cell Physiology, Faculty of Integrated Arts and Sciences. Hiroshima University, Higashi-Hiroshima 739 Japan, and/or from the American Type Culture Collection, 12301 Parklawn Drive, Rockville, Maryland 20852, USA. (ref. ID; 7350)

Raphidiophrys elegans Hertwig & Lesser, 1874 (ref. ID; 3541, 3691, 4731) reported year? (ref. ID; 1923, 3497) or Hertwig & Lesser, 1874 sensu Penard, 1904 (ref. ID; 4758) reported author and year? (ref. ID; 4884)

Synonym

Raphidiophrys conglobatum (Greeff, 1873) Penard, 1905 (ref. ID; 3541); Raphidiophrys orbicularis Nicholls, 1985 (ref. ID; 4758); Sphaerastrum conglobatum Greeff, 1873 (ref. ID; 3541); Sphaerastrum fockei Doflein, 1909 nec Archer, 1876 (ref. ID; 3541)

Re-diagnosis

Scales nearly orbicular to broadly ovate, sometimes oblong; scales often more or less curved with the poles bended downwards; scales 6.2-8.6x4.4-6.5 um with a L/B ratio usually 1.1-1.4, sometimes up to 2.0; scales with internal radial septa; number of septa along the border varying from 30 to 60 per 10 um; edge of the scales strongly inflected. Both solitary and colonial forms were collected. Colonial forms showed clusters of 6-27 individuals, though the light microscopic preparations gave the impression that larger colonies might have broken in two or more sub-colonies, probably due to the transfer of the material by pipetting onto the slides. Colonial and solitary forms show no differentiation in shape and structure of the scales. Though only visible in side view, the scales are often slightly curved, the two poles bending downwards. Not seldom, strongly folded scales are present among more flattened scales. These scales have a saddle-like appearance. The wide folded rim has its largest diameter near the poles. Light microscopically these scales have the appearance of crescents and show these forms in every position. These folded scales probably permit a more suitable arrangement around the axopods. A close arrangement of these scales gives it the appearance of a tube. Saddle-shaped scales were also pictured by Rainer (1968). (ref. ID; 4758)

Descriptions

Subcircular; disc-shaped spicules having thickened edges and forming elongate cone-shaped accumulations around the pseudopodia. Nucleus single, placed eccentrically. One contractile vacuole. Green zoochlorellae sometimes present. Often numbers of these individuals are grouped into colonies, jointed by protoplasmic processes. Habitat aquatic plants. (ref. ID; 1923)
The cell has a thick gelatinous coat composed of minute spines and no boundary of the ecto- and endoplasm. The nucleus with a karyosome is rather large, and many contractile vacuoles are scattering in the cell. (ref. ID; 3497)

Comments

Scales of R. elegans are distinguished from those of R. minuta which lack a curved rim. (ref. ID; 4758)

Measurements

Diameter 30-40 um. (ref. ID; 1923)
Diameter of a cell, 20-30 um; length of axopodia 40-50 um. (ref. ID; 3497)
Our results are in accord with those of Penard (1904; 7.5-8.0x6.0-6.25 um; L/B=1.3), Wailes (1921; 7-8x6 um; L/B=1.2), Hovasse (1964; 7.5-8.0x6.0-6.4 um; L/B=1.2; with a total number of ca. 100 septa along the rim), Rainer (1968; ex icon.: 5.0-7.5x1.5 um). (ref. ID; 4758)

Raphidiophrys intermedia Penard, 1904 (ref. ID; 3541, 3691 original paper, 4731, 4758) reported author and year? (ref. ID; 4884)

Diagnosis

Scales oblong, 7.2-12.7 um long and 3.1-4.8 um broad with a L/B ratio of 1.7-2.3 (mean 2.0); scales with internal radial septa; number of septa along the border varying from 29-33 per 10 um. Penard (1904), in diagnosing this species, describes the scales as having the shape of a parallelogram. The long sides of most scales run nearly parallel, a feature which is hardly observed among related species. Scales of other species have more convex sides. According to Penard (1904) the length of the scale is twice the breadth. The size of the scales is in accord with those reported by Rainer (1968; 5-9 um long; ex. icon.) and Siemensma (1981; 5-9 um). The shape and structure of the scales illustrated by Nicholls and Durrschmidt (1985) agree well with our result. The reported breadth of 2-3 um, however, is not in accord with our result, nor is the length. When the breadth of the scales is calculated from the photomicrographs, a breadth of 3.2-4.5 um is found, a length of 6.0-10.2 and a L/B ratio of 1.9-2.4. (ref. ID; 4758)

Descriptions

The scale measured 8.2x3.7 um. While similar to those of R. elegans. The scales of R. intermedia differ in being more oblong and having a pronounced and more uniform rim. (ref. ID; 4731)

Raphidiophrys marginata Siemensma, 1981 (ref. ID; 4758, 7658)

Descriptions

The scales are ovate; larger scales tend to be naviculoid. Size of the scales 5.9-10.0x2.5-3.9 um. L/B ratio 1.9-2.6 (mean 2.2). (ref. ID; 4758)
Widespread fresh-water species. Previously it was recorded in marine waters by Bardele (1981) as R. marina Ostenfeld, 1904. Cells 25-35 um in diameter; differ from the diagnosis by more narrow scales, 8.0-9.0x1.7-2.0 um. (ref. ID; 7658)

Raphidiophrys marina Ostenfeld, 1904 (ref. ID; 3541, 7658 redescribed paper)

Emended diagnosis

Cells 25-40 um in diameter. Periplast comprising long (25-35 um) and thin (0.50-0.65 um) tangental elements, slightly tapering towards the blunt apices; they seem to be solid; a central broadening is absent. (ref. ID; 7658)

Remarks

The most similar species is fresh-water R. pallida Schulze, 1874. However, the typical scales of R. pallida are tubular and their central parts are widened (unwrapped) and bounded by a rim formed by their rolled edges. On the contrary, the scales of R. marina seem to be solid (non-tubular) and void of any central widening; they are somewhat similar to the organic tangental spicules of Heterophrys fockii Archer, 1869 and may be the most primitive siliceous scales of acanthocystids. The organisms reported by Bardele (1981) as R. marina coincide the diagnosis of R. marginata Siemensma, 1981. In natural environments the species was collected in the North Sea (Ostenfeld 1904) and the White Sea (Mikrjukov 1994). (ref. ID; 7658)

Locality

The marine aquaria in the Institute for the Biology of Development. (ref. ID; 7658)

Raphidiophrys minuta Nicholls, 1985 (ref. ID; 4731) reported author and year? (ref. ID; 4884)

Descriptions

A single scale only was observed from Australian samples, circular-ovate in outline, 2.0x1.7 um, with short and long radially disposed ribs, and no marginal rim. (ref. ID; 4731)

Raphidiophrys ovalis (Durrschmidt, 1985) Siemensma & Roijackers, 1988 (ref. ID; 4758 redescribed paper) reported author and year? (ref. ID; 4884)

Diagnosis

Observed scales ovate, with inflected, sharp-edged, narrow rims; scale size 6.4-12.7x3.0-6.4 um, with a L/B-ratio of 1.4-2.3; number of septa along the border varying from 65-70 per 10 um. The size of the scale is larger than the type, but this species shows a large variation in scale size within a specimen (Nicholls and Durrschmidt 1985). Calculations derived from that photomicrograph showed a range between 4.4 and 9.0 um. The shape and structure of the scales in our specimen resemble closely that of the type. The upper plate of the scale is very fragile and sensitive to drying. Notwithstanding the weight of other scales, they easily collapse or split along the septa. (ref. ID; 4758)

Remarks

Scales of R. ovalis were published by Siemensma (1981) under name of R. intermedia and were considered by Nicholls and Durrschmidt (1985) to belong to a subspecies of R. (orbicularis) elegans. The distinctly ovate shape and the fragile structure of these scales, strongly different from all other known Raphidiophrys, justify the recognition at species level. (ref. ID; 4758)

Raphidiophrys pallida Schulze, 1874 (ref. ID; 3541, 3691, 4731, 4758, 7658) reported year? (ref. ID; 1618) reported author and year? (ref. ID; 5388)

Diagnosis

Cells 84-140 um in diameter; scales spindle-shaped, in the centre ca. 1.2 um wide, tapering to the tubular ends, each ca. 0.6 um thick and terminating in sharply pointed poles. The narrow scales have strongly inflected margins, leaving the impression of a narrow slit ca. 0.4 um wide and 2.6-3.2 um long; scales 10-36 um long; scale structure smooth. A lamellate nature of the scales could not be detected by SEM observations. Nicholls and Durrschmidt (1985) described the scales as smooth and patternless. (ref. ID; 4758)

Descriptions

Outer gelatinous envelope crowded with curved lenticular spicules, forming accumulations around pseudopodia; ectoplasm granulated; nucleus eccentric; contractile vacuoles; axial filaments arise from the central granule; solitary; among vegetation in still fresh water. (ref. ID; 1618)
The scales observed were 8.9-15.2 um long by 0.5-0.7 um wide at their centre, patternless other than for a central suture. (ref. ID; 4731)

Measurements

Diameter 50-60 um; nucleus 12-15 um in diameter; spicules 20 um long. (ref. ID; 1618)

Raphidiophrys symmetrica Penard, 1904 (ref. ID; 3541, 3691 original paper, 4731, 4758, 4878)

Descriptions

Scales with a reticulate pattern. SEM observations showed holes in the scale surface. Obviously, the reticulate pattern is formed by secondary layer on the scale plate, whereas the perforations indicate the absence of a first layer at some places. The shape of the scales is ovate to elongately ovate. (ref. ID; 4758)

Raphidiophrys viridis Archer, 1867 (ref. ID; 3541, 3691, 4758)

Diagnosis

Cells usually in colonies, each colony with 5-18 individuals; individuals ca. 50 um in diameter; scales rodlike, with strongly inflexed margins, leaving a narrow slit; exterior of the scale ornamented with rows of papillae; papillae at the poles ca. 0.1 um high, becoming smaller towards the centre of the scale; scales sometimes capitate at the rounded poles; scales 15-37 um long and ca. 1 um wide; number of septa along the margin 50-60 per 10 um. (ref. ID; 4758)

Remarks

The existence of septa in scales of this species was noticed by Penard (1904), unaware of the real meaning of the striations he saw. Similar striations were seen by Siemensma (1981) on scales embedded in Naphrax. This image is caused by air trapped between the two scale plates and the septa. (ref. ID; 4758)