Novel Species of Centrohelid Heliozoans (Centroplasthelida) for Freshwaters of Central and Southern Vietnam
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IOLOGY, MORPHOLOGY, AND SYSTEMATICS OF HYDROBIONTS
Novel Species of Centrohelid Heliozoans (Centroplasthelida) for Freshwaters of Central and Southern Vietnam D. G. Zagumyonnyia, *, E. S. Gusevb, A. A. Mylnikova, and A. P. Mylnikova, † aPapanin
Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, Nekouzskii raion, Yaroslavl oblast, Russia b Institute of Plant Physiology Russian Academy of Sciences, Moscow, Russia *e-mail: [email protected] Received November 1, 2018; revised April 9, 2019; accepted January 28, 2020
The species diversity, distribution, and morphological features of centrohelid heliozoans (Centroplasthelida) (Haptista: Centroplasthelida Febvre-Chevalier et Febvre, 1984) from freshwaters of Central and Southern Vietnam have been studied using scanning electron microscopy (SEM). Twelve species, belonging to Acanthocystidae, Choanocystidae, Pterocystidae, Raphidiophryidae, and Raphidocystidae families, have been found. Eleven species are new for Vietnam. Illustrated descriptions of species found are provided. The morphology of investigated centrohelids mainly corresponds to published data; however, some differences have been shown. The diversity of heliozoans in Vietnam and other regions has been discussed. Keywords: protists, centrohelid heliozoans, Heliozoa, Centrohelida, Vietnam, skeletal elements, scales, spicules, scanning electron microscope DOI: 10.1134/S1995082920030165
INTRODUCTION Centrohelid heliozoans are a group of heterotrophic amoeboid organisms with spine symmetry which belongs to the Haptista Cavalier-Smith, 2003 group, related to the SAR supergroup (Adl et al., 2019). Centrohelids are ubiquists, found in benthos, periphyton, and plankton of marine and freshwater ecosystems. They play a large role in the conversion of matter and energy and serve as an important link in microbial food webs. Centrohelid heliozoans (with the exception of the Oxnerella genus) have external skeletal elements. They are represented by spine or plate silicon scales or organic spicules. The structure of these elements is very important for species identification. The small size of the skeletal elements and their complex structure make it necessary to use electron microscopy to study these structures (Leonov and Plotnikov, 2009; Mikryukov, 2002; Mikrjukov and Croome, 1998). A correspondence was noted between the morphological data of the covering elements and the data of molecular phylogenetics (Cavalier-Smith and von der Heyden, 2007; Zlatogursky and Klimov, 2016). The distribution and diversity of centrohelid heliozoans is studied unevenly and insufficiently. New species have been described on a regular basis as of late † Deceased.
Abbreviations: SEM, scanning electron microscope.
(Prokina et al., 2019; Shshkin et al., 2018; Tikhonenkov and Mylnikov, 2011; Zlatogursky, 2014; Zlatogursky et al., 2019; etc.). However, there are no data on this group of protozoa for most regions. Until recently, there has been no information about the centrohelid heliozoans of Vietnam. The first informa
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