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How to achieve protein diversity by genome and transcriptome processing is essential for organismal complexity and adaptation. The present work identifies that the macronuclear genome of Halteria grandinella, a cosmopolitan unicellular eukaryote, is composed almost entirely of gene-sized nanochromosomes with extremely short nongenic regions., How to achieve protein diversity by genome and transcriptome processing is essential for organismal complexity and adaptation. The present work identifies that the macronuclear genome of Halteria grandinella, a cosmopolitan unicellular eukaryote, is composed almost entirely of gene-sized nanochromosomes with extremely short nongenic regions. This challenges our usual understanding of chromosomal structure and suggests the possibility of novel mechvanisms in transcriptional regulation. Comprehensive analysis of multiple data sets reveals that Halteria transcription dynamics are influenced by: (i) nonuniform nanochromosome copy numbers correlated with gene-expression level; (ii) dynamic alterations at both the DNA and RNA levels, including alternative internal eliminated sequence (IES) deletions during macronucleus formation and large-scale alternative splicing in transcript maturation; and (iii) extremely short 5′ and 3′ untranslated regions (UTRs) and universal TATA box-like motifs in the compact 5′ subtelomeric regions of most chromosomes. This study broadens the view of ciliate biology and the evolution of unicellular eukaryotes, and identifies Halteria as one of the most compact known eukaryotic genomes, indicating that complex cell structure does not require complex gene architecture.

Halteria grandinella (M��ller, 1773) Dujardin, 1841 Distribution. BRAZIL: Paran�� River between the Nupelia���s Field Station and the district of Porto S��o Jos��, S��o Pedro do Paran�� (Buosi et al. 2014 b, 2015), (Ad). DOMINICAN REPUBLIC: (Foissner et al. 2003). MEXICO: Coffee plantation La Onza, near Coatepec (Dur��n-Ram��rez et al. 2015), (Th); Coffee plantation Virginia Armand, near Coatepec (Dur��n-Ram��rez et al. 2015), (Th); Santuario del Bosque de Niebla, near Xalapa (Dur��nRam��rez et al. 2015), (Th). VENEZUELA: South margin of the Henri Pittier National Park, Biological Station Rancho Grande (Foissner 2016)., Published as part of Dur��n-Ram��rez, Carlos Alberto, Dias, Roberto J��nio Pedroso & Estrada, Rosaura May��n-, 2020, Checklist of ciliates (Alveolata: Ciliophora) that inhabit in bromeliads from the Neotropical Region, pp. 1-36 in Zootaxa 4895 (1) on page 10, DOI: 10.11646/zootaxa.4895.1.1, http://zenodo.org/record/4321437, {"references":["Buosi, P. R. B., Utz, L. R. P., de Meira, B. R., Segovia da Silva, B. T., Lansac-Toha, F. M., Lansac-Toha, F. A. L. & Velho, L. F. M. (2014 b) Rainfall influence on species composition of the ciliate community inhabiting bromeliad phytotelmata. Zoological Studies, 53, 1 - 12. https: // doi. org / 10.1186 / s 40555 - 014 - 0032 - 4","Buosi, P. R. B., Cabral, A. F., Utz, L. R. P., Vieira, L. C. G. & Velho, L. F. M. (2015) Effects of seasonality and dispersal on the ciliate community inhabiting bromeliad phytotelmata in riparian vegetation of a large tropical river. Journal of Eukaryotic Microbiology, 62 (6), 737 - 749. https: // doi. org / 10.1111 / jeu. 12232","Foissner, W., Struder-Kypke, M., van der Staay, G., Moon-van der Staay, S. & Hackstein, J. (2003) Endemic ciliates (Protozoa, Ciliophora) from tank bromeliads (Bromeliaceae): a combined morphological, molecular, and ecological study. European Journal of Protistology, 39, 365 - 372. https: // doi. org / 10.1078 / 0932 - 4739 - 00005","Duran-Ramirez, C. A., Garcia-Franco, J. G., Foissner, W. & Mayen-Estrada, R. (2015) Free living ciliates from epiphytic tank bromeliads in Mexico. European Journal of Protistology, 51, 15 - 33. https: // doi. org / 10.1016 / j. ejop. 2014.09.002","Foissner, W. (2016) Terrestrial and semiterrestrial ciliates (Protozoa, Ciliophora) from Venezuela and Galapagos. Denisia, 35, 1 - 912."]}

The contiguous sequence of the SSU rDNA, ITS 1, 5.8S, ITS 2, and approximately 1370 bp at the 5(') end of the LSU rDNA was determined in 25 stichotrichs, one oligotrich, and two hypotrichs. Maximum parsimony, neighbor-joining, and quartet-puzzling analyses were used to construct individual phylogenetic trees for SSU rDNA, for LSU rDNA, and ITS 1+5.8S+ITS 2, as well as for all these components combined. All trees were similar, with the greatest resolution obtained with the combined components. Phylogenetic relationships were largely consistent with classical taxonomy, with notable disagreements. DNA sequences indicate that Oxytricha granulifera and Oxytricha longa are rather distantly related. The oligotrich, Halteria grandinella, is placed well within the order Stichotrichida. Uroleptus pisces and Uroleptus gallina probably belong to different genera. Holosticha polystylata (family Holostichidae) and Urostyla grandis (family Urostylidae) are rather closely related. These rDNA sequence analyses imply the need for some modifications of classical taxonomic schemes.

Morphogenesis during cell division was investigated in oligotrichous ciliate,Halteria grandinella utilizing protargol impregnated specimens. The cortical morphogenetical pattern ofHalteria grandinella is generally similar to that given by Faure-Fremiet. The proter inherits the parental adoral zone of membranelles (AZM) apparently unchanged; in the opisthe the oral primordium develops de novo from a single. AZM-anlage; somatic cirri for both the proter and opisthe are separately differentiated from 10 (seldom 9) cirral primordia that originate de novo from 10 latitudinal developmental analagen. The anlage of paroral membrane of opisthe forms just to the right of the posterior end of the oral primordium. Each streak of cirral primordia develops 4 groups of basal body pairs: both of the anterior two consist of only one pair of basal bodies, on the contrary, each of the last two groups has 2 basal body pairs.

Summary Waters in large parts of the United States were sampled for Halteria bifurcata and Halteria grandinella. Live specimens were examined and measured by dark phase-contrast microscopy and photomicrography. The two species were mostly found together. H. bifurcata, for which measurements are provided, normally has a barb on one of its bristles number 1. Two new aberrant forms of H. bifurcata, as well as the previously reported aberrant types, are described and discussed. All the aberrant H. bifurcata forms are associated with shallow waters. Dimensions for several H. grandinella stocks are given and effects of ambient temperatures on structure are suggested.

A ciliated protozoan, Halteria grandinella, swam backward rapidly with a migration distance per second attaining 100 times the cell size. This high swimming velocity was accompanied by a high frequency of ciliary beating. Recordings with a high-speed digital video (10(3) frames/s) revealed that the frequency during forward and backward swimming was, respectively, 105 +/- 10 Hz and 260 +/- 30 Hz. These frequencies are the highest among cilia and flagella reported to date. Electron microscopic observation of the ciliary structure confirmed normal 9 + 2 arrangements of the axoneme except that cilia for migration are bundled into membranelles. Ciliary beating of saponin-treated cells was reactivated by the addition of Mg2+ -ATP, although the beating amplitude was smaller than that of intact cells. Kinetic analysis of the ATP-dependent increase of beating frequency revealed that the maximal frequency in the presence of free Ca2+ and 0.9 microM Ca2+ was approximately 60 and 110 Hz, respectively. A possible mechanism to increase beating frequency with Ca2+ is discussed.

The jumping behavior of Strobilidium velox and Halteria grandinella was analyzed videographically. On average, undisturbed cells of these species jumped 1.7–3.6 and 8 times per minute and spent 0.8 and 1.0% of their time jumping, respectively. Both ciliate species initiated jumps after encounters with rotifer predators. S. velox jumped on contact with Asplanchna girodi, traveling a mean distance of 1.5 mm (33 body lengths) at a mean velocity of 7 mm/s (154 body lengths/s) at 17°C. H. grandinella jumped on contact or near contact with Synchaeta pectinata, traveling a mean distance of 0.37 mm (18 body lengths) at a mean velocity of 2.76 mm/s (131 body lengths/s) at 20°C. The maximum velocity recorded during these escape jumps was 16.07 mm/s for S. velox and 3.70 mm/s for H. grandinella. In S. velox, swimming velocity during jumps was not significantly correlated either with swimming velocity just before jumping (mean = 0.15 mm/s) or with distance traveled. In H. grandinella, jumping velocity and distance also were not significantly correlated. Jumping in S. velox and H. grandinella was calculated to require approximately 149% and 41 % of total metabolic rate, respectively. Jumping seemed to be an effective defense against rotifer predation. Only 3% of 93 S. velox cells contacted by A. girodi were captured, and only 12% of 92 H. grandinella cells contacted or closely approached by S. pectinata were captured; all other cells jumped away. A predation experiment showed that A. girodi was about twice as, and significantly more, likely to ingest Paramecium tetraurelia as S. velox in a mixture of equal numbers of these ciliates. The swimming velocity of S. velox during jumps is the highest one so far reported for an oligotrich, and equals the highest one reported for any ciliate (Mesodinium rubrum).

Total cellular DNA from the ciliates Halteria grandinella and Trithigmostoma cucullulus was analyzed by agarose gel electrophoresis. The macronuclear DNA (MAC DNA) of Halteria consisted of very small fragments, which suggests that the MAC DNA organization of oligotrichs resembles that of hypotrichs (gene-sized DNA). The MAC DNA of Trithigmostoma, a cyrtophorid having a heteromeric MAC, also existed as small fragments, but with a significant fraction (20–30%) comprising larger molecules unresolved by the method used. It is suggested that MAC heteromery is related to the differential localization of two kinds of DNA molecules of different sizes.

These experiments have been carried out during the past year for the purpose of finding out whether the products of nucleoproteid breakdown have any effect upon the division rate of free-living cells, the ultimate aim being to get some light on the controlling factors of cell division.Two ciliated protozoa were used. One, Actinobolus radians Stein, lives exclusively on a diet of Halteria grandinella, another ciliate. The other, Blepharisma undulans Stein, lives on bacteria. Four control lines of each have been watched, fed, and the number of divisions recorded daily, and curves based upon the averaged division rates for five day periods, give the fluctuations in vitality of the organisms as measured by the division rates. Periods of depression, and of decreasing and increasing vitality have been clearly marked. Individuals for experimentation were in all cases sister cells of the control lines of the same dates.The results show that amino acids and their derivatives have but slight effect on the division ...