Revision of Strombidium paracalkinsi (Ciliophora: Oligotrichea: Oligotrichia), with Comparison of Strombidiids Bearing Thigmotactic Membranelles

Abstract

This study analyses the morphological characters of Strombidium paracalkinsi, a species bearing thigmotactic membranelles, collected from Jangmok Bay at the southern coast of Korea. The small subunit ribosomal RNA gene of S. paracalkinsi was sequenced for the first time. By a combination of characters, the thigmotactic membranelles of S. paracalkinsi differ from the thigmotactic membranelles of other strombidiids. They are (1) positioned on dorsal side, (2) contiguous with three membranelles of the adoral zone, but separated by nonciliated portions of the polykinetids, and (3) composed of two rows of kinetids. Except for the thigmotactic membranelles, the morphology of S. paracalkinsi conforms to the diagnosis of the genus Strombidium. Our phylogenetic tree confirms the nonmonophyly of the genus Strombidium. The thigmotactic membranelles are a promising feature for a future split of the genus Strombidium, but require further studies, especially on Strombidium calkinsi Fauré-Fremiet 1932.

Overview of the Diversity, Phylogeny and Biogeography of Strombidiid Oligotrich Ciliates (Protista, Ciliophora), With a Brief Revision and a Key to the Known Genera

“…Members of the family Strombidiidae Fauré-Fremiet, 1970, are reported to be ubiquitous and to episodically dominate the microzooplankton community in both coastal and oceanic waters ( Sherr and Sherr, 1987 ; Dolan et al, 2013 ; Sun et al, 2019 ; Yang et al, 2020 ). Due to their wide distribution, high abundance, and fast growth rate ( Montagnes, 1996 ; Santoferrara and McManus, 2017 ), numerous studies focusing on the taxonomy and phylogeny of strombidiids have been carried out (e.g., McManus et al, 2010 ; Agatha, 2011 , 2014 ; Lee et al, 2015 ; Liu et al, 2015a , 2016 ; Liu W. et al, 2017 ; Gao et al, 2016 , 2017 ; Li et al, 2020 ). The somatic ciliature of most strombidiids usually includes a girdle kinety (GK) and a ventral kinety (VK) although there is considerable variation of these two among the 12 genera of the family Strombidiidae and in some species the ventral kinety is lacking ( Lynn, 2008 ; Song et al, 2009 ; Agatha, 2011 ).…”

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 ...…”