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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Rhabdonella

Rhabdonella Brandt, 1907

[ref. ID; 3597]
Lorica conical or elongate chalice-shaped; oral border with a gutter between the inner and outer rims, the former usually erect and the latter flaring, a little low than the former; bowl gradually tapering in the anterior part, abruptly narrowing in the aboral region, usually having a slender pedicel pointed or perforated at its tip; wall separated in the bowl, composed of a fine prismatic structure, with a number of longitudinal or more or less spiral ribs which often branch on the surface and with minute fenestrae between ribs in many cases. (ref. ID; 3597)
Type species; Rhabdonella spiralis (Fol) Brandt (ref. ID; 3597)

[ref. ID; 4046]
A characteristic of the genus is the "gutter" of the anterior rim. (ref. ID; 4046)
  1. Rhabdonella amor (Cleve, 1900) (ref. ID; 4600) or (Cleve) Brandt (ref. ID; 3597, 4046)
  2. Rhabdonella apophysata (ref. ID; 3319)
  3. Rhabdonella brandti Kofoid & Campbell, 1929 (ref. ID; 4600)
  4. Rhabdonella conica Kofoid & Campbell, 1929 (ref. ID; 4600) reported author and year? (ref. ID; 4464)
  5. Rhabdonella cornucopia (ref. ID; 4464)
  6. Rhabdonella elegans Jorgensen (ref. ID; 3597) or (Jorgensen) Kofoid & Campbell (ref. ID; 4046)
  7. Rhabdonella indica Laackmann (ref. ID; 3597)
  8. Rhabdonella parvula Hada, 1938 (ref. ID; 3597 original paper)
  9. Rhabdonella poculum (Ostenfeld & Schmidt, 1901) (ref. ID; 4600) or (Ostenfeld & Schmidt) Kofoid & Campbell (ref. ID; 3597)
  10. Rhabdonella spiralis (Fol, 1881) (ref. ID; 4600) reported year? (ref. ID; 1940) or (Fol) Brandt (ref. ID; 3597) reported author and year? (ref. ID; 4464)

Rhabdonella amor (Cleve, 1900) (ref. ID; 4600) or (Cleve) Brandt (ref. ID; 3597, 4046)

Descriptions

Lorica conical, 2.0-2.3 inner oral diameters in length; outer rim little lower than the inner, 1.10-1.22 inner oral diameters; bowl gradually narrowing to the acute aboral end; aboral region forming an inverted cone of 40-48 degrees; wall separated in the upper 0.1 of the lorica, bearing about 20 vertical ribs which sometimes branch. (ref. ID; 3597)
Longitudinal ribs, that sometimes branch, extend the length of the lorica; irregularly positioned pores are present between the ribs. (ref. ID; 4046)

Comments

The species differs from R. indica Laackmann in being larger and having fewer ribs, and from P. poculum (Ostenfeld & Schmidt) in the absence of a conspicuous aboral horn and the small number of striae. (ref. ID; 3597)

Measurements

Length 75-90; inner oral diameter 37-40 um. (ref. ID; 3597)
The dimensions of the lorica are: length 66-91, width 43+/-4.3 um (n=5). (ref. ID; 4046)

Rhabdonella elegans Jorgensen (ref. ID; 3597) or (Jorgensen) Kofoid & Campbell (ref. ID; 4046)

Descriptions

Lorica chalice-shaped, 3.0-4.8 inner oral diameters in length; outer oral rim somewhat flaring, 1.14-1.23 inner oral diameters; bowl slightly conical (9-15 degrees) in its anterior part, then abruptly narrowing (34-55 degrees) in the aboral region; pedicel often elongated, 0.30-0.47 of the total length, gradually tapering (3-10 degrees) to a pointed tip; wall usually apparently separated in the bowl but weakly in the pedicel, having many longitudinal ribs (about 25) on the surface and numerous small fenestrae between them. (ref. ID; 3597)

Comments

The species differs from R. spiralis (Fol) in the small lorica and the short conical bowl. This species is exceedingly variable in size, form, and number of ribs, especially in the shape of the aboral region and in the elongation of a pedicel. The four species, brandti, valdestriata, inflata, and quantula of Kofoid & Campbell (1929), all belong to this species: the latter two have an inconspicuous distal pore, which is not of the usual construction in Rhabdonella. They can not be distinguished, because their differences seem to be individual variations. In the present investigation specimens of Kofoid & Campbell's brandti type with a stout pedicel were most frequently found, and those of quantula type consisting of a conical bowl and a slender pedicel were rarely detected from outside the barrier of the Palao Islands and the south-west of Formosa. There were observed stout conical specimens like Jorgensen's fig.67 (1924) and those provided with a pore at distal end of a pedicel. (ref. ID; 3597)
Hada included in this species Rhabdonella brandti Kofoid & Campbell, Rhabdonella valdestriata Brandt, Rhabdonella inflata Kofoid & Campbell, and Rhabdonella quantula Kofoid & Campbell. The lorica of R. elegans is characterized by its highly tapered posterior region. Longitudinal ribs, that sometimes branch, extend the length of the lorica; irregularly positioned pores are present between the ribs. Rhabdonella elegans differs from Rhabdonellopsis apophysata Cleve in the greater number of striations the lorica and in the absence of a posterior knob. (ref. ID; 4046)

Measurements

Length 140-205; inner oral diameter 35-48; outer oral diameter 40-60; length of the pedicel 55-94 um. (ref. ID; 3597)
The dimensions of the lorica are: length 164, width 48. SEM length 157, width 44 um (n=1). (ref. ID; 4046)

Rhabdonella parvula Hada, 1938 (ref. ID; 3597 original paper)

Descriptions

Lorica very small, subconical, 1.74 inner oral diameters in length; outer oral rim more or less flaring (35 degrees), its diameter 1.17 inner oral diameters; bowl most inflated at the portion of the suboral 0.25 of the total length, in greatest diameter 1.3 inner oral diameters, convex conical in the posterior half with a blunt end; wall single-layered except in the region of the oral gutter, almost hyaline, with numerous longitudinal striae running on the entire surface of the lorica. (ref. ID; 3597)

Comments

The new species differs from R. amor (Cleve) and R. indica Laackmann in being smaller and more dilated and from Protorhabdonella curta (Cleve) in having a distinctly developed oral gutter. This is the most primitive species in Rhabdonella showing a simple form and a weakly differentiated oral gutter, and also is related to Protorhabdonella because of the close resemblance to P. curta in size and form. (ref. ID; 3597)

Measurements

Length 40; inner oral diameter 23 um. (ref. ID; 3597)

Rhabdonella poculum (Ostenfeld & Schmidt, 1901) (ref. ID; 4600) or (Ostenfeld & Schmidt) Kofoid & Campbell (ref. ID; 3597)

Descriptions

Lorica stout, goblet-shaped, 1.8-2.2 inner oral diameters in length; inner oral rim erect or somewhat curved inwards, outer one flaring, 1.15-1.26 inner oral diameters; bowl subcylindrical in its main part; aboral region abruptly narrowing (70-95 degrees) to a stout pedicel forming a cone of 20-45 degrees; wall single-layered except a border of an oral gutter, ornamented with numerous vertical striae which sometimes branch. (ref. ID; 3597)

Comments

The species differs from R. amor (Cleve) in having a differentiated pedicel and numerous striae. (ref. ID; 3597)

Measurements

Length 80-96; inner oral diameter 38-44; outer oral diameter 44-51 um. (ref. ID; 3597)

Rhabdonella spiralis (Fol, 1881) (ref. ID; 4600) reported year? (ref. ID; 1940) or (Fol) Brandt (ref. ID; 3597) reported author and year? (ref. ID; 4464)

Descriptions

Lorica elongate, slender, 5-9 inner oral diameters in length; inner rim erect, outer one widely flaring (55-70 degrees), 1.2-1.3 inner oral diameters bowl gradually tapering (2-11 degrees) in its anterior main part, abruptly narrowing (18-37 degrees) posteriorly to a prolonged pedicel which is slender, 0.35-0.52 of the total length, and pointed or perforated at the terminal; wall perfectly separated almost through the lorica except the distal part of the pedicel of an imperfect separation, fenestration on the bowl always visible. (ref. ID; 3597)

Comments

The species differs from R. elegans Jorgensen in greater size, slender contour, and an elongation of the bowl. The species was first described by Fol (1881), and then it was again recorded by Biedermann (1893) under the different specific name, striata. Afterwards, Brandt (1907) divided it into several varieties and Kofoid & Campbell (1929) raised them to the rank of species. The identification of the species is, therefore, considerably confused at present. The species shows marked variation in dimensions, proportions, outline, and caudal elongation. From collections of the East Indies two distinguishable forms were observed; the short one is 264-320 um long and has a pointed tip, usually appearing in neritic plankton and being very similar to Biedermann's Tintinnus striatus (1893, Pl.3, fig.13a), Brandt's var. indopacifica (1906, Pl.52, fig.1), Jorgensen's species including var. elongate (1924, figs.68,69) and Marshall's specimen (1934, fig.23), while the other elongate one is 432-460 um long and provided with a long, slender pedicel perforated at the terminal, often occurring in open waters of the South China and Sulu Seas and agreeing with Kofoid & Campbell's R. conica (1929). It is considered that they are probably to be united into this species, because several intermediate forms were recorded by Brandt (1906-07) under names, R. spiralis and R. spiralis var. indopacifica. (ref. ID; 3597)

Measurements

Length 264-460; inner oral diameter 51-53; outer oral diameter 60-65; length of the depicel 96-240 um. (ref. ID; 3597)