Main Content

The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Tremula

Tremula Howe & Cavalier-Smith, 2011 (ref. ID; 7130 original paper)

Cercozoa: Order Tremulida (ref. ID; 7130 original paper)

[ref. ID; 7130]
Diagnosis; Anterior flagellum inserts at anterior end of cell but, unlike in Glissandra, not in a groove or notch; posterior flagellum inserts on ventral side at a mid-cell depression or notch, where cell narrows, or apically. Often vibrates energetically during movement. Able to survive in dry soil. Sometimes with an amoeboid phase that retains both flagella. (ref. ID; 7130)
Etymology; tremulans L. trembling. (ref. ID; 7130)
Type species; Tremula longifila (ref. ID; 7130)
  1. Tremula filosa (ref. ID; 7130)
  2. Tremula longifila Howe & Cavalier-Smith, 2011 (ref. ID; 7130 original paper)
  3. Tremula vibrans (ref. ID; 7130)

Tremula longifila Howe & Cavalier-Smith, 2011 (ref. ID; 7130 original paper)

Diagnosis

18S rDNA sequence, GenBank HQ121439; ITS2 rDNA Genbank HQ176332; cell size 13.5 um (12-14.5 um). AF and PF: 40-45 um; heterodynamic, AF active, rapid waves flicker along its entire length. PF passive, trailing or anchoring cell to substratum. AF emerges at cell anterior, PF from a notch midway on ventral side. Cell rounded with tapered anterior and posterior ends or elongated and somewhat spindle-shaped; medium notch variably pronounced. Cell and flagella usually flush with substratum, cell vibrates during gliding, sending vibrations along PF; AF flickers independently. Cell occasionally rise above substratum, anchored by PF and oscillate slowly to very rapidly. Cells usually travel, though pause frequently to pivot, twirl or vibrate in one location. No pseudopodia. N usually central; cv in posterior half of cell, anterior cv sometimes visible. Cysts not observed (those observed by ATCC may be of the heterokont prey Adriamonas sp., which does make cysts), but it grew well on just Volvic and grain, suggesting it can eat bacteria instead. (ref. ID; 7130)

Comments

ATCC50530 was originally misidentified as "Cercomonas vibrans Sandon". Sandon (1927) described Cercobodo vibrans as "broader in shape than C. agilis, sometimes quite spherical; length about 15 um; movements vibratory, not spiral; amoeboid phase often with fine sometimes branching, pseudopodia" and found it in 41 of 148 soils examined. He thought it similar in many respects to Cercomonas, but differed "in the freedom of the posterior flagellum and in the greater distinctness of the amoeboid and swimming stages". In the "flagellate condition short, finger-like pseudopodia are not infrequently found on all parts of the body, but most often at the posterior end. The amoeboid phase sometimes has a single broad pseudopodium, but at other times is surrounded by long, finger-like processes, often branched". Although ATCC50530 is similar in size and position of nucleus and contractile vacuole to Sandon's C. vibrans, one obvious difference is that T. longifila is never amoeboid. A second key difference is the position and lengths of the flagella: in C. vibrans both were inserted anteriorly, the anterior flagellum "a little longer than the body, and the ...[posterior flagellum] usually twice the body length"; but in ATCC50530 the posterior flagellum inserts midway down the cell; both are approximately three times body-length. These differences make C. vibrans a different species from T. longifila: we consider it anterior Tremula species with shorter flagella and more amoeboid behavior. We base this on Sandon's description of its 'very characteristic' 'swimming' with both flagella being 'straight and almost rigid, moving with a vibratory motion which throws the whole body into vibration' and 'progression is jerky but fairly rapid, and takes place along the line of the two flagella, the body of the organism being turned at a small angle to this line.' [our italics]. Given that there was probably no conception of flagellar gliding motion in Sandon's day, his use of the word 'swimming' may be misleading and should probably be discounted as his description of its motion appears rather similar to our observations of its otherwise unique gliding motility. However, if T. filosa and C. vibrans are congeneric, the name Cercobodo is inapplicable as it is probably a junior synonym for Cercomonas (Karpov et al. 2006) and ATCC50530 is phylogenetically entirely distinct from Cercomonadida, differing also in gliding on both flagella. Tremula filosa differs from all cercomonads but Cavernomonas (Bass et al. 2009) in not obviously forming pseudopodia. The difference in posterior flagellar insertion between T. longifila and C. vibrans is insufficient to require separate genera, especially as Sandon (1927) noted that 'sometimes it passes for a short distance through the body and thus appears to be inserted laterally'; thus this rare condition in C. vibrans appears to be the norm for T. longifila. In view of these similarities, especially in their shared unusual movement, we place C. vibrans also in Tremulidae. As the range of cell shape in T. longifila is very similar to the non-amoeboid version of C. vibrans, it seems unwise to establish two separate genera for them just because of the absence of amoeboid behavior in T. longifila and its much longer flagella. Accordingly we place C. vibrans in Tremula as T. vibrans Cavalier-Smith comb. n. (Basionym Cercobodo vibrans Sandon, 1927 pp 73-73). Both Tremula species (T. longifila and T. vibrans) differ substantially from Glissandra innuerende (Patterson and Simpson 1996), the only other zooflagellate known to glide with both flagella held tightly to the substratum; it is larger, with longer flagella, more elongated; its posterior flagellum inserts differently: Glissandra flagella emerge close together from a small anterior groove associated with an apical notch, both absent in Tremula; the T. longifila posterior flagellum emerges far away from the cell apex from a lateral notch. G. innuerende is smaller (5-8 um), with equal flagella ~3.5X BL. The flagella move differently: AF of Glissandra moves only at its tip, the remainder held stiffly in the direction of movement; the T. longifila AF is much less rigid, waves passing along its entire length. Glissandra has many cytoplasmic granules, Tremula does not. Glissandra is marine; contrastingly ATCC50530 and BCKV were from dry soil or dry stream sediment, respectively. T. vibrans from soil made large, very distinctive cysts. No sequences exist for Glissandra, so we do not know if it is a cercozoan. From its morphology and behavior Glissandra is most likely a filosan cercozoan and might belong in Tremulida, but without a sequence (or evidence for any marine members of NC11) we do not place it there but as Filosa incertae sedis. (ref. ID; 7130)

Etymology

longus L. long filum L. thread. (ref. ID; 7130)

Type strain

ATCC50530 (Year unknown; dry soil, Mexico City, Mexico; T. Nerad via J. Martinez-Cruz). (ref. ID; 7130)
Another strain (BCKV), isolated from dried freshwater stream bed sediment at Beaver Creek, Montezuma Castle Monument, Arizona, USA by KV, had identical 18S rDNA and ITS1 sequences. (ref. ID; 7130)