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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Membranicola

Membranicola Wilhelm Foissner, Helmut Berger, and Jochen Schaumburg, 1999 (ref. ID; 4613 original paper)

[ref. ID; 4613]
Diagnosis; Tintinnidiidae with tubular, agglutinated lorica subterminally closed by a distinct membrane, in the centre of which the cell is attached. Two ventral organelles; anterior portion of leftmost somatic ciliary rows distinctly cured ventrally. (ref. ID; 4613)
Comparison with related genera; When we commenced the field work for this book, we did not except to find a new tintinnid because freshwater tintinnids are well known and have a small diversity. It was thus a great surprise to discover a new species, which even belongs to a new genus. Membranicola tamari is unique among the known freshwater and marine tintinnids in having the lorica subterminally closed by a membrane which is secreted during lorica construction and rather fragile because it is poorly preserved in specimens prepared for scanning electron microscopy. The stalk-like posterior end of the cell is attached to the centre of the membrane, which stains with methylene blue and invariably spreads in the subterminal portion of the tubular lorica. Thus, both lorica ends are open. The location and structure of the ventral organelles are as in other members of the family, e.g. Tintinnidium fluviatile. Likewise, the somatic ciliary pattern is similar to members of Tintinnidium (dikinetids having only the posterior basal body ciliated), except for the leftmost ciliary rows, whose anterior portion is distinctly curved, extending almost horizontally to the main body axis. (ref. ID; 4613)
Etymology; Composite of the Latin noun membrana (membrane) and the Latin verb cola (inhabiting), meaning "a ciliate attached to a membrane". Feminine gender. (ref. ID; 4613)
Type species; Membranicola tamari nov. spec. (ref. ID; 4613)
  1. Membranicola tamari Wilhelm Foissner, Helmut Berger, and Jochen Schaumburg, 1999 (ref. ID; 4613 original paper)

Membranicola tamari Wilhelm Foissner, Helmut Berger, and Jochen Schaumburg, 1999 (ref. ID; 4613 original paper)

Diagnosis

Cell with stalk-like process in vivo about 120x40 um, broadly ellipsoidal with stalk about as long as body proper. Two macronuclear nodules with single micronucleus in between. On average 12 adoral membranelles and 12 somatic ciliary rows with highly differentiated ciliature. Lorica in vivo about 117x43 um, tubular, mainly composed of agglutinated diatom frustules. (ref. ID; 4613)

Descriptions

1) Body of about same size as lorica, that is, 90-160x35-45 um, including stalk-like, contractile cytoplasmic process anchoring cell to lorica membrane; stalk at least as long as body proper in fully extended specimens, which protrude up to 25 um beyond lorica opening; contracted specimens about half as long as extended ones. 2) Body of fully extended specimens broadly ellipsoidal with posterior half narrowed stalk-like and anchored to centre of subterminal lorica membrane; slightly contracted specimens cylindrical. Underneath ventral anterior end an inconspicuous bulge bearing two short, highly specialized ciliary rows ("ventral organelles"). Cell retracts into or leaves lorica when disturbed. 3) Two ellipsoidal, closely spaced macronuclear nodules in mid-body. Micronucleus between or at edge of abutting macronuclear beads, conspicuous in vivo because compact and up to 8 um across. 4) Contractile vacuole near anterior end, that is, in peristomial bottom, which can move up and down. 5) Cytoplasm, although colourless, often spotted due to 5-10 um sized food vacuoles with algal remnants. 6) 10-11, usually 10 ciliary rows on ellipsoidal body portion. Rows composed of basal body pairs having only the posterior basal body ciliated, of similar length, except for leftmost row (number 10 or 11), which is distinctly shorter than rows 4-6; anterior portion of leftmost two rows conspicuously curved ventrally, extending almost horizontally to longitudinal body axis; length of cilia, that is, highly different within and among ciliary rows. Two short, transversely oriented ventral ciliary rows (organelles) with conspicuous, 20-25 um long cilia on bulge underneath adoral zone of membranelles; anterior row (ventral organelle 2) invariably composed of 8 oblique basal body pairs having only the posterior basal body ciliated; posterior row (ventral organelle 1) roughly parallel to anterior row, left third usually curved posteriorly, composed of 16-20 ciliated basal body pairs. 7) Oral apparatus occupies anterior end of cell, consists of 12-13 (15 in Fuschlsee population) membranelles with 20-25 um long cilia forming conspicuous, circular adoral zone; undulating membrane, although rather long, inconspicuous because deep in buccal cavity. 8) Continuously swimming, that is, not jumping and spinning like other oligotrichs. 9) Lorica in vivo 90-160x40-50 um (outer dimensions of inhabited and very likely mature loricae, mean=117x43 um, n=19; prepared loricae shorter probably due to some shrinkage), tubular, rarely slightly curved and/or slightly widened anteriorly or posteriorly, flexible, consists mainly of agglutinated diatom frustules, even if mineralic seston is abundant, both ends transversely truncate and slightly irregular due to projecting agglutinated material; subterminal lorica membrane 10-30 um part from posterior end, thin and hyaline, thus easily overlooked in deserted loricae. (ref. ID; 4613)

Comments

Live specimens of M. tamari are easily identified by the subterminal lorica membrane. However, the membrane is often lost in deserted loricae and/or preserved specimens, which can be identified by two features: (i) the tubular, rather compact and stout lorica (length:width ratio 2.7:1, >3:1 in Tintinnidium fluviatile, T. pusillum and Tintinnopsis cylindrata) and (ii) the 2 macronuclear nodules. The last character is, however, found in two other freshwater tintinnids, namely Codonella cratera (lorica amphoriform, many ciliary rows forming dense field on left side) and Tintinnidium ephemeridum (lorica gelatinous and funnel-shaped, ciliary pattern not known). (ref. ID; 4613)

Etymology

We dedicate this new species to Dr. Henry Tamar (Indiana State University, USA), who significantly contributed to the knowledge of plankton ciliates and enriched our book with his excellent micrographs. (ref. ID; 4613)

Type location

Plankton of a eutrophic lake (Wallersee) in Salzburg, Austria (47 degrees 55'N, 13 degrees 10'E). (ref. ID; 4613)

Type slides

Five slides (1 holotype, 4 paratypes) with protargol-impregnated specimens have been deposited in the Oberosterreichische Landesmuseum in Linz (LI), Austria. (ref. ID; 4613)