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14ALGAE - ВОДОРОСЛИ
Thalassiosira duostra (Bacillariophyta), a new for the flora of Russia
freshwater diatom species
S. I. Genkal
Institute for Biology of Inland Waters of the Russian Academy of Sciences, Borok, Russia
genkal@ibiw.yaroslavl.ru
Abstract. The study of archive materials has made it possible to specify species composition of the genus Thalassiosira and discover a new for the flora of Russia representative of centric diatoms, T. duostra, in Cheboksary and Tsimlyansk reservoirs and the Oka River. The valve diameter and number of central futoportulae in the examined material differ insignificantly from the original description and published data. By the general valve outline, structure and arrangement of central and marginal fultoportulae and quantitative characteristics, T. duostra is very similar to Conticribra weissflogii and Thalassiosira faurii, which may result in inaccurate identification of these species. In the Conticribra weissflogii the rimoportula is located not in a ring of marginal fultoportulae but closer to the valve center and its internal part is significantly larger than in Thalassiosira duostra. The external arrangement of marginal fultoportulae (tubes of the processes are outwardly directed at different angles) and their internal arrangement (the processes are arranged in two rings, they are more dense in the ring which is closer to the valve face) is a good specific feature that differentiates T. duostra and T. faurii.
Keywords: Bacillariophyta, Thalassiosira, frustule morphology, scanning electron microscopy, Russia.
Thalassiosira duostra (Bacillariophyta) — новый для флоры России вид пресноводных диатомовых водорослей
С. И. Генкал
Институт биологии внутренних вод им. И. Д. Папанина РАН, Борок, Россия genkal@ibiw.yaroslavl.ru
Резюме. Изучение архивных материалов позволило уточнить видовой состав рода Thalassiosira и выявить в Чебоксарском и Цимлянском водохранилищах и в р. Оке новый для флоры России вид центрических диатомовых водорослей T. duostra. В исследованном материале диаметр створки и число центральных выростов незначительно отличались от первоописания и литературных данных. По общему абрису створки, строению и расположению центральных и краевых выростов, количественным признакам T. duostra имеет большое сходство с Conticribra weissflogii и Thalassiosira faurii, что может привести к неточной идентификации этих видов. У Conticribra weissflogii двугубый вырост располагается не в кольце краевых выростов, а ближе к центру створки и его внутренняя часть значительно больше таковой, чем у Thalassiosira duostra. Хорошим отличительным признаком между T. duostra и T. faurii является расположение краевых выростов с наружной поверхности (трубки выростов направлены наружу под разными углами) и внутренней поверхности (в виде двух колец, при этом в ближнем к лицевой части створки выросты расположены чаще).
https://doi.org/10.31111/nsnr/2019.53.1.7
7
Ключевые слова: Bacillariophyta, Thalassiosira, морфология панциря, сканирующая электронная микроскопия, Россия.
Among tens of species of the genus а Thalassiosira Cl. known for Russia only six species according to Makarova (1988) occur in freshwater waterbodies and watercourses: T. bramaputrae (Ehrenberg) Hakansson et Locker, T. guillardii Hasle, T. inserta Makarova, T. proschkinae Makarova, T. pseudonana Hasle et Heimdal, T. weissflogii (Grunow) Fryxell et Hasle. Two more species of this genus have been recorded in the Volga reservoirs later — T. faurii (Gasse) Hasle и T. gessneri Hustedt (Genkal, Korneva, 2001). Recently, Conticribra Stachura-Sushoples et Williams has been described as a new genus, and two species from those listed above have been transferred to this genus: C. guillardii (Hasle) Stachura-Sushoples et Williams and C. weissflogii (Grunow) Stachura-Sushoples et Williams (Stachura-Sushoples, Williams, 2009). In representatives of this genus, areolae from the internal valve surface are ravered with semicontinuous cribra and the rimoportula on the valve mantle replaces a fultopor-tula. Later on, the analysis of published data and materials on the alga, previously referred to T. bramaputrae in the Russian literature, has shown that its records belong to another species of the genus — T. lacustris (Grunow) Hasle (Genkal, 2011).
Talassiosira duostra Pienaar was described from the Vaal River in South Africa (Pie-naar, Pieterse, 1990). The species is characterized by the presence of central fultoportu-lae, located eccentrically and valve face areolae arranged in fascicles. Later this species was recorded in European waterbodies and watercourses (Kiss etal, 2001, 2012; Woital, Kwandrans, 2006; Perez et al, 2009). T. duostra is characterized as a freshwater, probably mesogalobic species that occurs in eutrophic lakes and rivers (Kiss et al., 2012). By valve morphology, T. duostra is similar to T. weissflogii and T. faurii. In some cases, this causes inaccuracies in T. weissflogii identification in waterbodies and watercourses of Russia (Genkal, Golokolenova, 2008; Genkal, Kulikovsky, 2009; Genkal, Okhapkin, 2013).
This study, based on archive materials collected by the author, aims at specifying the species composition of the genus Thalassiosira in waterbodies and watercourses of the Russian Federation.
Material and Methods
Phytoplankton samples for this study were collected from Cheboksar (July 1981), Tsimlyansk (July 2007) reservoirs and the Oka River (July-August 2011).
Diatom frustules were cleaned from the organic matter by cold burning (Balonov, 1975) with sulphuric acid and potassium dichromate. Cleaned specimens were dried onto stubs, coated with gold using an EIKO-IB-3 sputter coater and examined using a JSM-25S scanning electron microscope operating at 15 kV.
Results and Discussion
In studied material, we found isolated valves of T. duostra with a valve diameter ranging from 23.6 to 30 jm, and round, randomly arranged, valve areolae (Plate I, 3). Externally, central fultoportulae appear as circular openings, slightly rising above
Plate I. Thalassiosira duostra (1-4), Conticribra weissflogii (5, 6). 1-3 — external view of the valve (arrows central fultoportulae), 4, 6 — internal view of the valve (arrows rimoportula and central fultoportulae), 5 — external view of the valve (arrows rimoportula). Scale bars: 1-3, 5, 6 — 5 |im; 4 — 10 |im.
the valve surface (Pl. I, 1-3) and internally — as short tubes surrounded by four pores. The number of central fultoportulae varies from 3 to 9 and the processes are arranged in a circle (Plate I, 1-3). There is a ring of 7-11 marginal fultoportulae in 10 |im at the junction of the valve face and the valve mantle (Plate I, 1-4). Externally, they appear as along tube, internally — as ashort tube surrounded by four pores (Plate I, 1-4). The rimoportula is located in the ring of marginal fultoportulae (Plate I, 4). Externally, this process appears as along tube of the same size as the marginal fultoportulae, internally — as a small radially oriented fissure (Plate I, 4). We found the internal surface of only one valve in the analyzed material with some marginal fultoportulae and one rimoportula. The second process was likely to be covered with mud.
In our material, maximum valve diameter and number of central fultoportulae are greater than in the literature (Table 1). According to the original description, the central fultoportulae are eccentrically located, V of the valve radius apart, often in groups of 2, 3 or 4 processes (Pienaar, Pieterse, 1990). Valves with two and up to six processes have been recorded in the natural Brazil population. The processes on the valve are arranged in one or several groups. The same number of central fultoportulae is observed in the culture, with similar arrangement as in the natural population but often almost at the valve margin (Torgan et al, 2006). Some researchers give a higher number of central processes in T. duostra and present pictures with the fultoportulae arrangement similar to ours (Kiss et al., 2012: Fig.6 A, B). Our data on the shape of areolae, number of marginal fultoportulae in 10 |im, number of rimoportulae and location of the latter corresponds to the published data (Table 1). Arrangement of valve face areolae in fascicles (or sectors) is one of the main diagnostic features of T. duostra (Table 1). However, in LM and SEM images presented in the original description (Pienaar, Pie-terse, 1990: Figs 1-3) as well as in other publications (Torgan et al., 2004; Kiss et al, 2012), no distinct arrangement of areolae in sectorsis can be seen. Also, as opposed to the natural population, a random arrangement of valve areolae has been recorded in the culture of T. duostra (Table 1).
By the general valve outline in internal and external views and arrangement of central fultoportulae T. duostra is similar to Conticribra weissflogii (Plate I, 5, 6; Genkal, Kulikovsky, 2009). The main quantitative diagnostic features of these species coincide too (Table 2). It should be noted that Thalassiosira duostra, T. faurii and Conticribra weissflogii can be present together in samples (Genkal, Golokolenova, 2008; Genkal, Okhapkin, 2013), that causes some problems in the identification of these morphologically similar species. For that reason, in some cases, Thalassiosira duostra valves were identified as Conticribra weissflogii (Genkal, Kulikovsky, 2009: Fig. 2: 2, 3, 7; Genkal, Golokolenova, 2008: Fig. 5: 8; Genkal, Okhapkin, 2013: Fig. 2b). The position and structure of rimoportula is a good differential characteristic of Thalassiosira duostra and Conticribra weissflogii (compare Plate I, 4, 6). By the general valve outline in internal and external views and arrangement of central fultoportulae T. duostra is similar to T. faurii (Genkal et al., 2007). The ranges of variations in quantitative characteristics
Table 1
Morphological characters of the Thalassiosira duostra on the basis of published data
Reference numbers Characters 1 2 3 4* 4** 5 6***
Diam., |im 10.3-25.7 11-21 7.2-23 11.9-16.8 5-12 7-26 17-47
Valve face areola in 10 |im 25-30 18-24 10-23 18-24 17-30 10-30 14-17
Areola shape on the valve face round round, polygonal round round, elongate, polygonal round or Polygonal
Areolar pattern fasciculate fasciculate fasciculate disarranged
Valve mantle areolae in 10 |m 21-40 15-30 25-30 30-37 15-40 20
Areola shape on the mantle round elongate round elongate, polygonal
Number of valve face fultopor-tulae 2-4 5-8 5-8 4-6 3-6 2-8 2-8
Number of marginal fultopor-tulae in 10 |m 5-11 9-11 7.4-15 7-10 6-8 8-11 4-7
Number of rimoportulae 1-2 1 1-2 1 1 1-2 1-5
Note. Reference numbers: 1 — Pienaar, Pieterse, 1990; 2 — Li et al, 2013; 3 — Kiss et al., 2001; 4 — Torgan et al., 2006; 5 — Kiss et al., 2012; 6 — Roubeix et al, 2014. * — natural population, **— culture material, ***— as Thalassiosira faurii.
coincide in these two species well (Table 2). Kiss et al. (2001, Figs 1, 2) illustrate T. duostra with SEM images. In our opinion, these are pictures of T. faurii, since the external tubes of marginal fultoportulae are directed at different angles. In the work by Roubeix et al. (2014) there is a description of T. faurii and illustrations of a form very similar to T. duostra. The external arrangement of marginal fultoportulae (tubes of the processes are outwardly directed at different angles) and their internal arrangement (the processes are arranged in two rings, they are more dense in the ring which is closer to the valve face) is a good specific feature that differentiate T. duostra and T. faurii (Genkal et al, 2007).
Table 2
Morphological characters of the Thalassiosira duostra, T. faurii and Conticribra weissflogii
on the basis of published data
Diam. of valve, |im Number of valve face fultoportulae Number of marginal fultoportulae in 10 |m Number of rimoportulae Number of satellite pores of central fultoportulae Number of satellite pores of marginal fultoportulae
Conticribra weissflogii (after Genkal, Kulikovsky, 2009)
10-35 (?)12-28 8-16 1 3-4 4 (3)
Thalassiosira faurii (after Genkal et al., 2007)
13.6-66.6 2-10 5-14 2-4 (5?) 4 4
T. duostra (summary data from Tablel)
5-26 2-8 5-15 1-2 4 4
Acknowledgements
This study was performed within the framework of the state assignment "Systema-tics, Diversity and Phylogeny of Aquatic Autotrophic Organisms in Russia and Other Regions of the World" (№ AAAA-A18-118012690095-4).
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Makarova I. V. 1988. Genus: Thalassiosira Cl. Diatomovye vodorosli SSSR (iskopaemye i sovremen-nye). T. II, vypusk 1 [The diatoms of the USSR (fossil and recent). Vol. II, fasc. 1]. Leningrad: 58-81. (In Russ.).
Perez M. C., Maidana N. I., Comas A. 2009. Phytoplankton composition of the Ebro River estuary, Spain. Acta Botanica Croatica 68(1): 11-27.
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Stachura-Sushoples K., Williams D. M. 2009. Description of Conticribra tricircularis, a new genus and species of Thalassiosirales, with a discussion on its relationship to other continuous cribra species of Thalassiosira Cleve (Bacillariophyta) and its freshwater origin. European Journal of Phycology 44(4): 477-486. https://doi.org/10.1080/09670260903225431
Torgan C. L., Vieira A. A. H., Giroldo D., Santos C. B. 2006. Morphological irregularity and small cell size in Thalassiosira duostra maintained in culture. Eighteenth International Diatom Symposium. Miedzyzdroje: 407-416.
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Литература
[Balonov] Балонов И. М. 1975. Подготовка водорослей к электронной микроскопии. Методика изучения биогеоценозов внутренних водоемов. М.: 87-89.
[Genkal] Генкал С. И. 2011. К морфологии, таксономии и распространению в России Thalassiosira bramaputrae и T. lacustris (Bacillariophyta). Новости систематики низших растений 45: 20-26.
[Genkal, Golokolenova] Генкал С. И., Голоколенова Т. Б. 2008. Центрические диатомовые водоросли Цимлянского водохранилища. Поволжский экологический журнал 3: 178-189.
[Genkal, Korneva] Генкал С. И., Корнева Л. Г. 2001. Новые находки диатомовых водорослей (Centrophyceae) из волжских водохранилищ (Россия). Альгология 11(4): 457-461.
[Genkal, Kulikovsky] Генкал С. И., Куликовский М. С. 2009. К морфологии, экологии и распространению Thalassiosira weissflogii (Bacillariophyta). Поволжский экологический журнал 3: 183-189.
[Genkal, Okhapkin] Генкал С. И., Охапкин А. Г. 2013. Центрические диатомовые водоросли (Centrophyceae) нижнего течения р. Оки (Российская Федерация). Гидробиологический журнал 49(1): 44-61.
[Genkal, Terenko] Генкал С. И., Теренько Л. М. 2014. Новые данные к флоре центрических диатомовых водорослей (Centrophyceae) Черного моря. Гидробиологический журнал 50(2): 38-49.
[Genkal et al.] Генкал С. И., Теренько Л. М., Нестерова Д. А. 2009. Новые данные к флоре центрических диатомовых водорослей (Centrophyceae) Придунайского района Черного моря. Гидробиологический журнал 45(4): 52-72.
[Genkal et al.] Генкал С. И., Щербак В. И., Майстрова Н. В. 2007. Морфологическая изменчивость и таксономия Thalassiosira fauri (Gasse) Hasle (Bacillariophyta). Новости систематики низших растений 41: 26-33.
Kiss K. T., Acs E., Houk E. V., Marvan P., Ector L. 2001. Thalassiosira duostra Pienaar a new centric diatom for the European algal flora. 12th Hungarian algological meeting. Pecs, Hungary, 1518 May 2001. Pecs: 28.
Kiss K. T., Klee R., Ector L., Acs E. . 2012. Centric diatoms of large rivers and tributaries in Hungary: morphology and biogeographic distribution. Acta Botanica Croatica. 71(2): 311-363. https://doi.org/10.2478/v10184-011-0067-0
Li Y., Zhao Q., Lu S. 2013. The genus Tahalassiosira of the Guangdong coast, South China Sea. Botanica Marina 56(1): 83-110. https://doi.org/10.1515/bot-2011 -0045
[Makarova] Макарова И. В. 1988. Род: Thalassiosira Cl. Диатомовые водоросли СССР (ископаемые и современные). Т. II, вып. 1. Л.: 58-81.
Perez M. C., Maidana N. I., Comas A. 2009. Phytoplankton composition of the Ebro River estuary, Spain. Acta Botanica Croatica 68(1): 11-27.
Pienaar C., Pieterse A. J. H. 1990. Thalassiosira duostra sp. nov. a new fresh water centric diatom from the Vaalriver, South Africa. Diatom Research 5(1): 105-111. https://doi.org/10.1080/0269249X.1990.9705096
Roubeix V., Chalie F., Gasse F. 2014. The diatom Thalassiosira faurii (Gasse) Hasle in the Ziway-Sha-la lakes (Ethiopia) and implications for paleoclimatic reconstructions: Case study of the Gla-cial-Holocene transition in East Africa. Palaeogeography, Palaeclimatology, Palaeoecology 402: 104-112. https://doi.org/10.1016Xj.palaeo.2014.03.014
Stachura-Sushoples K., Williams D. M. 2009. Description of Conticribra tricircularis, a new genus and species of Thalassiosirales, with a discussion on its relationship to other continuous cribra species of Thalassiosira Cleve (Bacillariophyta) and its freshwater origin. European Journal of Phycology 44(4): 477-486. https://doi.org/10.1080/09670260903225431
Torgan C. L., Vieira A. A. H., Giroldo D., Santos C. B. 2004. Morphological irregularity and small cell size in Thalassiosira duostra maintained in culture. Eighteenth International Diatom Symposium. Miedzyzdroje: 407-416.
Woital A. Z., Kwandrans J. 2006. Diatoms of the Wyzyna Krakowsko-Czestochowska upland (S Poland) — Coscinodiscophyceae (Thalassiosirophycidae). Polish BotanicalJournal 51(2): 177-207.
