Pleuroplitoides
Pleuroplitoides Foissner, 1996 (ref. ID; 2128)
[ref. ID; 2128]
Pleuroplitidae with isomorphic dorsal brush composed of 2 rows of paired, shortened cilia. (ref. ID; 2128)
Comparison with related genera; Pleuroplitoides is distinguished from Pleuroplites, the sole other member of the family, by the structure of the dorsal brush. It consists of 2 rows of in Pleuroplitoides and more than 3 rows in Pleuroplites. Furthermore and more importantly, the rows of Pleuroplitoides are isomorphic, i.e., consist of pairs of basal bodies (dikinetids), while those of Pleuroplites are hetero-morphic, i.e. composed of normal somatic cilia (monokinetids) interspersed between dikinetids with shortened cilia. (ref. ID; 2128)
Etymology; Composite of pleuroplites (laterally armed soldier) and oides (similar, to Pleuroplites). Masculine gender. (ref. ID; 2128)
Type species; Pleuroplitoides smithi (ref. ID; 2128)
- Pleuroplitoides smithi Foissner, 1996 (ref. ID; 2128)
Descriptions
Twenty three ciliary rows on average, 2 of them differentiated to brush in anterior quarter. Extrusomes rod-shaped, very slender, about 5 um long, form elliptical patch between two ventrolateral ciliary rows. Macronucleus reniform, micronucleus globular. Slightly reniform to bursiform, dorsal side convex, ventral slightly concave; prepared specimens ellipsoid or pyriform, i.e. inflated in mid-body or at posterior end. Anterior end transverse truncate, posterior broadly rounded. Transverse section roundish with sharp ribs left of ciliary rows. Macronucleus in or near centre of cell, with many globular and ellipsoidal nucleoli. Micronucleus near macronucleus. Contractile vacuole in posterior end. Fifty to hundred extrusomes in dense, elliptical bundle located ventrolaterally, i.e. about 130 degrees clockwise from dorsal brush, between two slightly widened ciliary rows; individual toxicysts very fine and thus easily overlooked in live cells, distal end however strongly argyophilic and thus very prominent in prepared specimens. Cortex flexible, distinctly furrowed by ciliary rows. Cytoplasm usually with many 2-5 um sized, colourless fat globules and few, large food vacuoles containing residues of ingested ciliates (Gonostomum affine). Swims rather slowly by rotation about main body axis. Cilia 8-10 um long, rather widely spaced arranged in longitudinal rows commencing closely underneath circumoral kinety. Dorsal brush cilia very closely spaced, in vivo about 4 um long and slightly inflated at distal end. Oral bulge very similar to that of Papillorhabdos, i.e. flat, inconspicuous and slightly depressed in centre. Circumoral kinety at base of oral bulge, composed of dikinetids having only posterior basal body ciliated. Oral basket inconspicuous in live cells, but rather distinct in protargol impregnated specimens, composed of bifurcated nematodesmata originating from oral dikinetids. Nematodesmata also originate from 3-5 monokinetids at anterior end of all somatic kineties and extend obliquely to oral basket. Silverline system very fine-meshed, as in other gymnostomatids. (ref. ID; 2128)
Notes
Plueroplitoides smithi differs from Pleuroplites australis Foissner, 1988, which also occurs in Antarctica, not only by the generic characters mentioned but also by its larger size (70-100 um vs. 35-50 um) and extrusomes (5 um vs. 2.5 um) as well as by the reniform (globular in P. asutralis) macronucleus and the higher number of somatic kineties (23 vs. 14). These species are thus easily distinguished even in live condition. However, P. smithi is easily confused with Fuscheria terricola, also occurring in Antarctica. This species highly resembles P. smithi in all characters except for the extrusomes, which are located in the centre of the oral bulge, a very useful character for distinguishing P. smithi and F. terricola in live condition. (ref. ID; 2128)
Etymology
Named in honour of Professor Dr H.G. Smith (Coventry Polytechnic, England), who undertook many interesting studies on Antarctic soil protozoa. (ref. ID; 2128)
Measurements
In vivo about 70-110x30-40 um. (ref. ID; 2128)