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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Peregrinia

Peregrinia Cavalier-Smith, 2011 (ref. ID; 7130 original paper)

Family Peregriniidae Cavalier-Smith, 2011 (ref. ID; 7130)

[ref. ID; 7130]
Diagnosis; Large freshwater non-thecate amoeboflagellates; move by amoeboid creeping, not swimming or flagellar gliding; surface covered in single layer of two-tiered siliceous scales visible only by electron microscopy; scales oval in surface view with inrolled sides to the upper tier, oblong in lateral view with more convex upper surface; highly metabolic flattened amoebae with lamellar and finger-like pseudopodia. Cysts unknown. (ref. ID; 7130)
Etymology; peregrinus L. wanderer for its creeping behaviour. (ref. ID; 7130)
Type species; Peregrinia clavideferens (ref. ID; 7130)
  1. Peregrinia clavideferens Howe, Arndt & Cavalier-Smith, 2011 (ref. ID; 7130 original paper)
  2. Peregrinia limax Cavalier-Smith comb. n. (ref. ID; 7130)
    Basionym; Gyromitus limax Swale & Belcher, 1975 (ref. ID; 7130)

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

Diagnosis

Type 18S rDNA sequence, GenBank DQ211593; ITS rDNA GenBank HQ176336; cell size very visible, 25.4 um (14-40 um); cell flattened (disc-like), irregular-shaped, very amoeboid, constantly changing. Highly metabolic; flagella usually not visible. Finger-like and long tapering filose, sometimes branching, pseudopodia all over cell. Often a lamellar sheet projects from leading edge, from which filose and finger-like pseudopodia extend and contract as cell creeps along substratum. Thickly covered with numerous scales of bilaterally asymmetric, rounded three-dimensional oblong shape, tapering somewhat like a sequashed elongated but bilaterally asymmetric barrel, with bowed sides, up and bottom (0.21-0.25x0.51-0.62 um); oval in surface view with lateral lips typically more strongly inrolled than in P. limax often so as to virtually touch each other, but sometimes less pinched in laterally; scales with a fenestrated flange on the more curved side (unlike P. limax) and with slightly indented ends with three thick struts connecting the two bowed surfaces. Numerous large and small vacuoles throughout cell. Culture medium Volvic and grain; bacterivorous. Vacuolate cysts frequent, round, 12.3 um (11-14 um) diameter. Two flagella visible in light microscope only when culture first isolated. (ref. ID; 7130)

Comments

HFCC94 was identified as Gyromitus sp. when its 18S rDNA was sequenced (Wylezich et al. 2007). To clarify the difference between Peregrinia and Gyromitus we summarize here past knowledge of Gyromitus strains and scale morphology. The Gyromitus type species is G. disomatus (Skuja, 1939), a free-swimming monad, barely metabolic with two flagella emerging from an anterior depression, 15-22 um long, 11-19 um wide, but with an ability to emit pseudopods from a posterior notch; it differed from Peregrinia by not becoming an amoeba with no visible flagella. The biflagellate strain of Swale and Belcher (1974) emitted pseudopods from its posterior while swimming and would also settle and transform into an amoeba with thin branching pseudopods similar to those of P. clavideferens and no apparent flagella (unlike Skuja's organism, so might not be the same). Two other Gyromitus species are known: G. cordiformis (Skuja, 1948), whose scale type is unknown, and G. limax (Swale and Belcher 1975) that we now treat as a second Peregrinia species because its scales are similar to those of P. clavideferens. The Gyromitus strains studied by Nicholls (1979) from six Ontario lakes were definitely not P. limax; he thought most of the identical to those of Swale and Belcher's strain and called them all G. disomatus, but recognised that some were clearly different. However, none of those he illustrated are 'identical' of those of Swale and Belcher; his five micrographs show at least four distinct scale types and, if each species has only one, may represent five species; as he saw some forms with pseudopodial tails but never a fully amoeboid stage like that of Swale and Belcher (1976), at least some of his strains may be closer to the original G. disomatus than was theirs. Nicholls seems to have been unaware of G. cordiformis or the need to observe characters such as the position of contractile vacuoles (which he did not record) to distinguish the two species. However, as G. cordiformis (Skuja 1948) produced pseudopods from the middle of a marked ventral groove (not a terminal notch as in disomatus), Nicholls' mention of 'tails' suggests that at least some of his were more disomatus-like. Nicholls noted that the latticed cylinder wall of the Canadian strains had 4-8 rows of pores; by contrast in the single UK strain (probably the only one in clonal culture) the scales seem very uniform with four rows of medium sized pores of equal size in the cylinder wall (Swale and Belcher 1974). Unfortunately Nicholls did not mention which micrographs came from different samples; his Figure 5 shows scales much deeper in proportion to their length than the UK strain or any others he illustrates; as they apparently have eight rows of pores of equal size it cannot be the same species. By contrast his other scales are much shallower, somewhat more like those of the UK strain in depth. But their pores are clearly different; his Figure 8 and 9 might be one species as both show two prominent central rows of very large holes; as he mentions four rows, he presumably includes also the somewhat smaller pores visible in the dense rims of these sclaes - if we had included these rim pores for the UK strain the pore rows would number six, not four; thus the different number of pore rows and much larger pore size of the two main rows compared with the UK strain means they are probably separate species. His Figure 7 differs radically from the other four and from that of Belcher and Swale in that the lower rim with the sieve-like plate has a much smaller diameter than the upper rim, so this is yet another species. His Figure 6 has more equal sized rims but they are much more delicate than the heavily inrolled rim of the UK strain. Thus, there is evidence for at least five different species of Gyromitus with scales of this oval sieve type, which Nicholls (1979) demonstrated contain silica; the non-scale phenotype of these strains embranced that of G. disomatus but as their scales all differ we shall never know exactly which scale type was present in Skuja's original. It is therefore best to call all these strains G. aff. disomatus until a new culture becomes available suitable for defining a neotype. Nicholls convincingly demonstrates that Hymenomonas prenanti (Lecal 1965) was not a new species of haptophyte but a misidentidifed Gyromitus. But we do not agree that is was the same species as that of Swale and Belcher (1974) as unlike theirs it appears to have at least two kinds of scales (if those in his Figure 1 really came from one cell): tall, ones with about six rows of small holes similar to those of Nicholls' figure 5) and squat ones about half as tall, more like other strains of Nicholls or Swale and Belcher but apparently not precisely the same as any of them. Until a G. disomatus neotype of known scale type is established we cannot say whether H. prenanti is a superfluous synonym for G. disomatus as Nicholls argued or whether prenanti is instead a fourth species of Gyromitus (most likely). What is clear is that P. clavideferens scales differ from all the G. aff. disomatus strains (Nicholls 1979; Swale and Belcher 1974) so radically that it cannot be G. disomatus and must be a separate genus, whereas 'H.' prenanti scales (Lecal 1965) are sufficiently like G. aff. disomatus to be congeneric. Scales of both Peregrinia species resemble those of Thaumatomonadidae in having an upper plate, unlike all G. aff. disomatus, which fits the position of Peregrinia as sister to Thaumatomonadidae on our tree. so we assign Peregrinia to Thaumatomonadida. However, as the upper plate of Peregrinia has a central cleft with inrolled margins, we exclude Peregrinia from Thaumatomonadidae, whose scales were bilaterally symmetric ovals or triangular with a upper plate having in entire (cleft-free) centre (Thaumatomastix additionally makes long spine scales with round or triangular basses). (ref. ID; 7130)

Etymology

clavus L. nail, rudder; deferens L. bearing; for its filose pseudopodia. (ref. ID; 7130)

Type strain

CCAP 1956/1; HFCC94 (2001; freshwater, Schoehsee, nr Ploen, Germany; C. Wyezich; = Gyromitus sp. of Wylezich et al. 2007). (ref. ID; 7130)