New data on Myxomycetes of North-Eastern Russia

Results of the study of species diversity of myxomycetes in North-Eastern Russia are presented. Moist chamber cultures were prepared with samples of leaf litter from Republic of Sakha (Yakutia) and Magadan oblast and with samples of bark from two sample plots in the vicinity of Yakutsk and Neryungri. A total of 49 species in 23 genera, 9 families, and 5 orders were recorded during the study.


Introduction
Myxomycetes (plasmodial slime molds) are a group of free-living protists belonging to Amoebozoa [1]. Their life cycle includes mobile trophic stages without hard cell wall, resting, and reproductive stages; the latter are represented various types of fruiting bodies. No regular studies of myxomycete communities of North-Eastern Russia were conducted to date. Magadan Oblast and Chukotka Autonomous Okrug are relatively well-studied: there were recorded 40 and 50 species, respectively [2][3][4][5]. In Republic of Sakha (Yakutia), two species were found before our study: Fuligo septica (L.) F.H. Wigg. [6] and Lycogala epidendrum (L.) Fr. [7]. The present study summarizes moist chamber data for Sakha for the first time and lists new findings for Magadan Oblast. Part of the results of the study was presented at the International science forum "Lomonosov" [8]. Fragments of dry grass litter of last year (primarily Poaceae and Cyperaceae) were collected as a substrate in the localities 1-25 and 28-34. Sample plots were established in Loc 26 and 27; there, bark from 5 most abundant tree species was collected as a substrate (Pinus sp., Alnus sp., Popolus sp., Larix sp., Salix sp., and Betula sp.).

Materials and methods
Substrate samples were collected in the sterile paper bags, where they were dried at room temperature without sunlight. This study presents the results of 261 experiments with moist chamber cultures: 187 with samples of bark and 74 with samples of grass litter.
Moist chamber cultures were performed according to the standard technique [9]. Petri dishes 10 cm in diameter were lined with filter paper, which was then wetted with water. The substrate fragments were distributed evenly on the Petri dish bottom so the entire surface could be observed. After the substrate fragments were placed in the chamber, it was wetted with excessive amount of water. The Petri dishes were checked on the second day, and excess water was either removed or added. Small amounts of water were added during the next waterings depending on a given substrate. The chambers were checked and watered at least every 10 days over the course of 3 months. During checks, fruit bodies from the moist chambers were mounted on paper tray using standard technique [10] and were placed in a matchbox in the herbarium. A species from single substrate was considered as a single specimen, even the substrate was placed in several moist chambers. Therefore, all fruit bodies of a given species that were found during all checks in all chambers were included in one specimen, even if content of the corresponding paper bag were distributed between two or more chambers [9].
Taxon authors are given in accordance with nomenclatural information system of Eumycetozoa [12]. In this study, we used the system of class Myxomycetes as proposed by C. Lado and U. Eliasson [13].
All collected specimens were deposited in the Myxomycetes collection of Department of Mycology and Algology, Faculty of Biology, Lomonosov Moscow State University (acronym MYX) and in Popov Herbarium of Central Siberian Botanical Garden, Siberian Branch of Russian Academy of Sciences (acronym NSK).

Annotated list of species
The list of species below is in alphabetical order. New species for Magadan Oblast are marked with " †"; for the Republic of Sakha, "*".
*  [14]. Its main special feature are the sparingly branched and heavily calcified capillitium. These tubes extend away from the peridium and are attached to the base of sporangium. After the dehiscence of sporangium, well noticeable tooth-like processes remain on the inner surface of peridium. It is believed that this species is widespread but does not occur in mass anywhere [15].

Discussion
A total of 49 species from 23 genera, 9 families, and 5 orders were identified during this study with 261 moist chamber cultures. The highest number of species was in the orders Physarales (17 species) and Trichiales (15 species), compared to the number of species in the other orders: Stemonitidales (9 species), Cribrariales (5 species) и Echinosteliales (3 species). The highest number of species was noted in the genera Didymium (6 species), Physarum, Perichaena (5 species), and Trichia and Licea (4 species each). A total of 9 species were added to the list of myxomycetes of Magadan Oblast, and 44 species were added to the list of myxomycetes of Sakha.
The results can be divided into two groups. As a result of 74 moist chamber cultures where grass litter was used as a substrate, 30 species were found. In 187 cultures with tree bark as a substrate, 25 species were found. However, only 6 species (12%) formed fruit bodies on both types of substrate, indicating certain substrate preferences of most species we recorded. This result highlights the need for comprehensive studies of species diversity that would use for the moist chamber cultures all available substrates such as rotten wood, leaf litter, and dung of herbivores. Moist chamber culture technique along with the collection of specimens in the field are necessary for revealing the most complete morphospecies list of a given territory [9].