Some Ultrastructural Features of the Planktonic Freshwater Ciliate Limnostrombidium viride (Alveolata, Ciliophora, Oligotrichida) and Improved Diagnoses of Oligotrich Taxa

Abstract

The first transmission and scanning electron microscopical studies in combination with freeze-fracture technology have disclosed some important morphological and ultrastructural features in the freshwater oligotrichid Limnostrombidium viride. (I) The dikinetids (paired basal bodies) of the girdle kinety have a club-shaped cilium associated only with each left basal body. The electron-dense (paraflagellar) body on one side of its “9×2+2”-axoneme and the regular array of intramembranous particles indicate a sensory, perhaps photoreceptor function of these club-shaped cilia. (II) The stichomonad endoral membrane is proximally covered by a cytoplasmic fold and distally by multiple membranous layers. Thus entirely covered, the endoral is probably no longer involved in food capture; nonetheless, its associated microtubules might stabilise the cytopharynx. (III) Instead of a contractile vacuole, a horizontal ring-canal with supposed osmoregulatory function occurs. (IV) The extrusive nature of the trichites is not only observed in electron micrographs, but the attachment sites of these organelles also display a rosette of “8+1”-particles in the P-face of freeze-fracture replicas typical for ciliate extrusomes. (V) The neoformation organelle, the subsurface tube in which stomatogenesis takes place, shows short basal bodies and normal axonemes about 1 μm long. It is accompanied by numerous membrane vesicles, which might provide membrane material for the outgrowing cilia.

Somatic infraciliature in tintinnid ciliates (Alveolata, Ciliophora, Spirotricha): An ultrastructural comparison*

“…Protargol‐stained specimens of the strombidinopsid genera Strombidinopsis and Parastrombidium display argyrophilic structures extending on the right of the dikinetidal somatic kineties (Lynn et al, 1991 ; Xu et al, 2007 ) probably representing overlapping postciliary ribbons. In the oligotrichid Limnostrombidium viride , Bardele et al ( 2018 ) observed an arrangement of electron‐dense material adjacent to the dikinetids resembling the attachment sites of the ribbons I–III. While further ultrastructural studies are thus needed to elucidate the distribution of the overlapping postciliary ribbons and the extraordinary ribbons I–III among aloricate choreotrichids, overlapping postciliary ribbons and a microtubular network similar to that described for the tintinnids are highly likely absent in oligotrichids (Bardele et al, 2018 ; Fauré‐Fremiet & Ganier, 1970 ; Modeo et al, 2003 ).…”

“…In the oligotrichid Limnostrombidium viride , Bardele et al ( 2018 ) observed an arrangement of electron‐dense material adjacent to the dikinetids resembling the attachment sites of the ribbons I–III. While further ultrastructural studies are thus needed to elucidate the distribution of the overlapping postciliary ribbons and the extraordinary ribbons I–III among aloricate choreotrichids, overlapping postciliary ribbons and a microtubular network similar to that described for the tintinnids are highly likely absent in oligotrichids (Bardele et al, 2018 ; Fauré‐Fremiet & Ganier, 1970 ; Modeo et al, 2003 ). Likewise, the ribbons I–III and overlapping postciliary ribbons have not been reported from any other spirotrich (Table 1 ).…”

Trichite features contribute to the revision of the genus Strombidium (Alveolata, Ciliophora, Spirotricha)

“…They were occasionally considered skeletal elements (Fauré-Fremiet, 1924;Fauré-Fremiet & Ganier, 1970) or contractile fibers (Lohmann, 1908), although Entz Sr. (1884), Penard (1920), and Kahl (1932) noticed an ejection of these organelles. Since then, the ejection of trichites by oligotrichids sampled from marine and freshwater has been repeatedly verified in several studies, using live observation and electron microscopy (Agatha, 2003;Agatha & Riedel-Lorjé, 1997;Agatha et al, 2005;Bardele et al, 2018;Krainer, 1991;Modeo et al, 2001;Montagnes et al, 1988;Petz & Foissner, 1992;. The organelles fulfill the definition of extrusomes given by Hausmann (1978), being rapidly dischargeable, membrane-bound structures that undergo morphological changes during their transition from the resting state to the ejected form.…”

“…Limnostrombidium viride (Figure 6D; Table 2; Bardele et al, 2018). This species is the only representative of the family Pelagostrombidiidae whose trichites ultrastructurally investigated.…”

Diversity Patterns of Protists Are Highly Affected by Methods Disentangling Biological Variants: A Case Study in Oligotrich (s.l.) Ciliates

“…Ecological habitat is classified as F = freshwater (≤0.5‰), L = low-brackish (0.5–18‰), H =high-brackish (18–30‰), and M = marine (30–40‰). References [ 66 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109 , 110 , 111 , 112 , 113 , 114 , 115 , 116 ...…”