Minimassisteria
Minimassisteria Arndt & Cavalier-Smith (ref. ID; 7130 original paper)
Class Granofilosea Cavalier-Smith and Bass, 2009: Order Leucodictyida Cavalier-Smith, 1993: Family Massisteriidae Cavalier-Smith, 1993 (ref. ID; 7130)
[ref. ID; 7130]
Diagnosis; Trimorphic naked filose rhizopodial biflagellate. Trophic phase feeds by non-anastomosing filose pseudopodia that bear obvious granules at intervals along their length. With distinct swimming form and (unlike Massisteria its closest relative) a crawling form with a thicker non-granular anterior tractional pseudopodium. Heterotrophic. (ref. ID; 7130)
Etymology; mini small, plus massisteria, for its similarity to Massisteria. (ref. ID; 7130)
Type species; Minimassisteria diva (ref. ID; 7130)
- Minimassisteria diva Arndt & Cavalier-Smith (ref. ID; 7130 original paper)
Minimassisteria diva Arndt & Cavalier-Smith (ref. ID; 7130 original paper)
Diagnosis
Sequences GenBank EF405665 (18S rDNA) EF405698 (ITS1) from the Cologne strain HFCC380. Trimorphic, with stationary feeding forms with slender granular filopodia stretched in all directions over the substratum; crawling forms that creep with thicker non-granular filopodia; and swimming monads.
- Feeding form: flattened body attached to the substrate. Cell body 2.3-5.0 um (average 3.2+/-0.5 um, n=33). 1-15 radiating delicate filopodia with up to about 11 granules (probably extrusomes); length from a few to 52 um (average 30.5+/-12.8 um, n=10). Aggregations of cells on substratum, where attached cells multiplied by fission.
- Swimming form: attached cells change into sausage-shaped swimming stages, more slender than trophonts (2 by 4.5 um in size), have one anterior and one trailing flagellum, each ~4 um long, and move relatively fast. Within few minutes, swimming stages may attach to the substratum reforming trophonts. Flagella are partly resorbed and shorter than in swimming stage (<2 um). Generally, trophont flagella are montionless and hard to see. Phagotrophic, capture bacteria.
- Cysts: 2.5-3.0 (mean 2.7) um diameter, the foregoing describe the Cologne strain. The Oxford strain trophonts had similar cell body size, 3 um (2.5-3.5 um); the two flagella, approximately 0.5 < 1X BL emerge at (thus defined) cell anterior; usually held curved towards the posterior flush with the surface either on the same or one on each side of cell; PF straight and usually non-motile. AF curved and occasionally slowly extends perpendicular to the cell then returns with rapid flicking motion. Cells globose, with several long granular non-anastomosing filose pseudopodia in contact with substratum at all points; very little cell activity seen; though most granules stationary, some move up or down filopodia. Long cells, or those collected in groups, often surrounded by and embedded in debris. Swimming form morphologically like Cologne strain, except flagella unequal; swims shorter AF first, spinning/rotating on longitudinal axis and sinuously through water column. Grows in artificial seawater with mixed bacteria to high density. Cysts not obseved in Oxford strian. No cv; n central.
- Crawling form: one major pseudopodium (thicker and shorter than in trophonts, so granules invisible), posterior flagellum trails, typically with other thick pseudopods on either side. (ref. ID; 7130)
Comments
Minimassisteria diva 18S rDNA sequence from both our isolates is identical to marine sediment environmental clone he17 (Bass et al. 2009), which in most datasets including many other Granofilosea is a long-branch member of a robustly supported marine clade including Massisteria marina. (ref. ID; 7130)
Etymology
diva L. goddess, but named after deep-sea expedition DIVA on which HFCC380 was collected [Northern Cape Abyssal Plain (28 degrees 6.8'S, 7 degrees 20.8'E) at depth of 5036 m; strain isolated March 4th, 2005 (R/V "Meteor", Cruise M63/2, station #38)]. (ref. ID; 7130)
Examined specimens
Two strains were isolated independently by the Oxford and Cologne laboratories; as they have identical 18S sequences we publish together to avoid assigning different names to one species. Type strain CCAP 1947/1 isolated by Ema Chao (Oxford) as a contaminant in a marine culture of Oxnerella sp. that was cultured DB from muddy coastal sand (Walney Island, Cumbria, UK) (2009; GenBank HQ176324). (ref. ID; 7130)