Phylogenetic position and taxonomy of three heterocytous ...

Polar Biol (2012) 35:759–774 DOI 10.1007/s00300-011-1123-x

ORIGINAL PAPER

Phylogenetic position and taxonomy of three heterocytous cyanobacteria dominating the littoral of deglaciated lakes, James Ross Island, Antarctica J. Komárek · L. Nedbalová · T. Hauer

Received: 21 March 2011 / Revised: 18 October 2011 / Accepted: 21 October 2011 / Published online: 19 November 2011 © Springer-Verlag 2011

Abstract Several communities of autotrophic microorganisms, in which cyanobacteria are dominant or play a substantial role in their structure, were studied on the deglaciated Ulu Peninsula, northern part of James Ross Island, NW Weddell Sea, Antarctica, in 2007–2009. Our results were compared with similar data from maritime Antarctica (King George Island, South Shetland Islands, 2005). Characteristics and taxonomic description of three important heterocytous species, which participate in cyanoprokaryotic assemblages in the littoral of small lakes, seepages, and on wetted rocks during the Antarctic summer season, are included in this study. They belong to the form-genera Calothrix and Hassallia, respectively, and are unidentiWable according to the present determination literature. Therefore, after a polyphasic evaluation, they are described as three new species, Calothrix elsteri sp. nova, Hassallia andreassenii sp. nova, and Hassallia antarctica sp. nova. 16S rRNA gene sequencing of isolated strains conWrmed the taxonomic position of all three species, and their ecology and seasonal development are described. All three discovered species are dominant in distinct communities with a specialized ecology and may be endemic for coastal maritime Antarctica.

J. Komárek (&) · L. Nedbalová · T. Hauer Institute of Botany AS CR, Dukelská 135, 379 82 Tlebok, Czech Republic e-mail: [email protected] J. Komárek · T. Hauer Faculty of Science, University of South Bohemia, Braninovská 31, 370 05 Beské Bud5jovice, Czech Republic L. Nedbalová Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Prague, Czech Republic

Keywords Heterocytous cyanobacteria · Antarctica · Lakes · New species · Ecology

Introduction Stable cyanobacterial communities in Antarctic habitats (developing with the same dominant morpho- and genotypes in each Antarctic summer season) have distinct seasonality and develop during each polar summer with characteristic species composition and structure (zonation) of mats. Numerous dominant species are ecologically specialized to the extreme Antarctic conditions (in their corresponding type of habitats) and may be endemic. Analyses of the molecular background of natural samples and isolated strains (cf. Gordon et al. 2000; Nadeau et al. 2001; Taton et al. 2003, 2006; Casamatta et al. 2005; Jungblut et al. 2005; Strunecký et al. 2010; etc.), as well as the distinct morphology and ecology of various Antarctic populations and strains (Broady and Kibblewhite 1991; Komárek 1999; Komárek and Elster 2008; etc.), support the taxonomic separation of numerous Antarctic cyanobacterial morpho- and ecotypes. We describe three heterocytous species in this article, which are dominant in cyanobacterial communities in the littoral zone of several lakes on James Ross Island in the northwestern part of the Weddell Sea. Their ecological role (participation on calcium carbonate precipitations) in aquatic microcommunities and unique morphology cannot be connected with any other known taxon. All three studied species are therefore important and speciWc for the extreme microhabitats in the described Antarctic lakes. Because they were never found and detected in ecosystems of other parts of the world, they can be local or endemic taxa in these communities. Of course, this conclusion must be

123

760

supported by further investigation. We compare our results also to similar localities in maritime Antarctica, particularly King George Island (South Shetland Islands).

Localities and methods Type material of our new species is described from the littoral of freshwater lakes near the eastern coast of the Ulu Peninsula in the northern part of James Ross Island, NW part of the Weddell Sea. It is situated east from the northern end of the Antarctic Peninsula, from which it is separated by the approximately 10–12 km wide Prince-Gustav Channel. The island was connected with the peninsula until the 1980s by continual shelf ice, which melted in recent decades. Numerous moraines and relatively old lakes with characteristic microXora occur in the mountainous deglaciated eastern part of Ulu Peninsula (Fig. 1). The formation of the lakes under study was connected with the last deglaciation period during Termination I and early Holocene (7,000– 12,000 years) and they belong to the oldest lakes in the area (Hjort et al. 1997). For an ecological description of the whole area, see Komárek and Elster (2008) and Komárek et al. (2008). Our main samples were collected from three areas during the Antarctic summer seasons (January to March) 2007, 2008, and 2009 (Fig. 1): 1. In the northeastern part of the Ulu Peninsula and in the vicinity of two Lachman Lakes (»10 m above see level; cf. Fig. 2a). They are shallow water bodies (up to 0.5 m deep, area 30,000 m2—Lachman I and 15,000 m2—Lachman II) without ice cover and neighboring snow Welds in the summer season (from December to March). They have a muddy-stony littoral and their bottom is formed by a thick muddy layer, originating mostly from a high input of cretaceous sediments. There are numerous seepages and small shallow pools around the lakes, sometimes fed by small streams Xowing from distant melting snow Welds. Rich cyanobacterial populations and communities develop regularly in these habitats. Black mats of Calothrix with dark brown sheaths occur on wet or Xooded stones, while clusters of one type of Hassallia (designated of Hassallia antarctica) sporadically occur in small water puddles in seepages. 2. Two characteristic lakes (Green Lake I—»70 m above see level, Green Lake II—»40 m above see level (Fig. 2b), about 1 m deep and with an area of 5,000 and 3,000 m2, respectively) occur in a small mountainous area in the eastern part of the Ulu Peninsula near Andreassen Point. The littoral is stony, composed of basaltic stones with spaces between the rocky blocks,

123

Polar Biol (2012) 35:759–774

which are partly Xooded and covered with a thin layer of water. The blackish bioWlm with dominant Calothrix is developed on the stony surface (Fig. 2c); strains of a distinct, speciWc Hassallia type were isolated from the same habitat (Fig. 2d). Macroscopic clusters of H. antarctica type develop in holes between stones. 3. Black Lake (170 m above see level, 0.5 m deep, area 5,000 m2) is situated close to Torrent Valley (SE part of Ulu Peninsula), where several lakes are located on a plateau called Lagoons Mesa, south from St. Martha Cove (Fig. 1). The character of the littoral is similar to the Green Lakes with marked black mats dominated by Calothrix covering the whole lake bottom. The temperature, conductivity, dissolved oxygen, and pH of the lakes were measured in the Weld using a YSI 600 m. Chlorophyll-a concentrations were determined Xuorometrically (TD-700 laboratory Xuorometer, Turner Designs, USA). Samples were gently Wltered through glass Wber Wlters (Whatman GF/F, UK), and the Wlters were kept frozen until analysis. Extraction was performed after the addition of 90% acetone and methanol at 65°C as according to Pechar (1987). Ecological data are presented with each species. The populations of collected cyanobacteria were studied under an Olympus BX51 optical microscope (up to 1,000£ magniWcation and conWrmed by phase contrast) and preserved with formaldehyde. Part of the fresh material was used immediately for cultivation in BG11 medium, diluted to 1/2 concentration of nutrients. The natural material was inoculated on solid (agarized) medium and kept under natural illumination and temperature in the Weld before the transport to laboratories in Europe (in cool box). The isolated strains (Table 1) were transferred to the laboratories and kept in the Algological Department of the Institute of Botany of the Academy of Sciences of the Czech Republic in Tlebok, in temperature 10–12°C and under 18–25 mol m¡2 s¡1 illumination by Xuorescent lamps. The samples of Calothrix and Hassallia from other aquatic habitats of Ulu Peninsula (James Ross Island) and locations on King George Island, South Shetlands, maritime Antarctica (deglaciated areas of Admiralty Bay and Fildes Peninsula) were used for morphological comparison of our populations. 16S rRNA gene sequencing was used for phylogenetic evaluation. The total genomic DNA was extracted using a protocol published by Yilmaz et al. (2009). The 16S rRNA gene and associated 16S–23S gene internal transcribed spacer region (ITS) of strains were ampliWed from the genomic DNA by PCR using the oligonucleotide primers: primer 1 (5⬘-CTC TGT GTG CCT AGG TAT CC-3⬘) (Wilmotte et al. 1993; Boyer et al. 2002) and primer 2 (5⬘-GGG GAA TTT TCC GCA ATG GG-3⬘) (Nübel et al. 1997;

Polar Biol (2012) 35:759–774

761

Fig. 1 The northern part of James Ross Island (Ulu Peninsula) with localities of studied lakes (Lachman I and II, Green Lakes I and II, and Black Lake). Topography based on the map by Czech Geological Survey (2009)

Boyer et al. 2002). AmpliWcation was performed in a Biometra® T3 thermocycler. Reactions were cycled with an initial denaturation step at 95°C for 5 min, followed by 35 cycles of DNA denaturation at 94°C for 1 min, primer

annealing at 55°C for 45 s, strand extension at 72°C for 2 min, and a Wnal extension step at 72°C for 10 min. PCR products were puriWed from the gel using QIAquick gel extraction kits (Qiagen) and sequenced directly by cycle

123

762

Polar Biol (2012) 35:759–774

Fig. 2 Localities of our strains, a Lachman II Lake, b Green II Lake, c surface of stones covered with dominant black mats of Calothrix elsteri, d stones with small calcareous precipitations covered by

Table 1 List of studied and sequenced strains (CCALA = Culture Collection of Algae at the Laboratory of Algology, Institute of Botany AS CR, Tlebok, Czech Republic—http://www.butbn. cas.cz/ccala/index.php)

Name

Strain

Locality

Calothrix elsteri

CCALA 953 (BL2)

James Ross Isl., Black Lake (surface of stones in littoral)

H. andreassenii

CCALA 954 (L27)

James Ross Isl., Green Lake II (surface of stromatolites)

H. antarctica

CCALA 955 (GL2)

James Ross Isl., Green Lake I (among stony blocks in littoral)

H. antarctica

CCALA 956 (GL6)


H. antarctica

CCALA 957 (GL22)


sequencing using the BigDye™ Terminator Cycle Sequencing kit V3.1 (Perkin-Elmer). Primers used for the cycle sequencing of 16S rRNA were the same primers used for PCR ampliWcation. The 16S rRNA gene sequences were used for the phylogenetic analysis. The 16S rRNA sequenced fragments were assembled into contigs of length 1,111–1,144 bp using EditSeq™ and SeqMan™ II software (DNAStar, Madison, WI, USA). The nucleotide sequences of 16S rRNA gene obtained in this study and related ingroup and outgroup sequences obtained from GenBank, EMBL, and DDBJ were aligned using MAFFT (Katoh et al. 2002), and ambiguous or hypervariable sites were

123

community of Calothrix elsteri, H. andreassenii, and green algae (Pseudendoclonium sp.)

removed using BioEdit 7.0.5.3 (Hall 1999). Alignments were analyzed and phylogenic trees produced by SeaVIEW 4.2.11 (Gouy et al. 2010) and Mr. Bayes 3.1.2 (Huelsenbeck and Ronquist 2001) softwares.

Results The studied populations of Calothrix and Hassallia from Ulu Peninsula do not correspond morphologically and ecologically to any previously described members of mentioned genera.

Polar Biol (2012) 35:759–774

763

Fig. 3 Comparison of the type strain of Calothrix elsteri with other up to now sequenced Calothrix strains derived from GenBank. The support values are given for Maximum likelihood, Maximum parsimony, and Bayesian posterior probabilities. The values cut-oVs for bootstrap and probability are 50 (0.5 resp). Our reference strain CCALA 953 (accession number FR822750) is printed bold

Calothrix elsteri Calothrix elsteri grows commonly in seepages in the vicinity of the Lachman Lakes in the northeastern part of the Ulu Peninsula (Fig. 1) and particularly in the littoral and benthos of several old lakes (Green Lake I, Green Lake II, Black Lake). It forms a black bioWlm, which covers the upper sur-

face of stones. It is common particularly in the littoral zone of lakes and adjacent seepages, where the stony substrate is Xooded for a long period or continuously by water. In seepages, it prefers slightly streaming water, while in lakes, it grows on stones in the benthos or in the littoral with an intense spray of water. Its phylogenetic position was conWrmed by 16S rRNA gene sequencing (Fig. 3).

123

764

Polar Biol (2012) 35:759–774

Fig. 4 Calothrix elsteri, natural material: a–d variability of Wlaments, e detail of a Wlament, f–g details of terminal hairs, h–i formation of hormogonia, j–k bases of Wlaments, l–m young Wlaments, n empty sheath. Orig

Calothrix elsteri spec. nova Morphological characters (Figs. 4, 5) Filaments Xexuous, solitary, or gathered in irregular groups and clusters, up to 360 m long (rarely longer), continually narrowed toward ends, widest at the base, 11–16 m wide, but not onion-like widened. Sheaths Wrm, thin up to slightly thickened and slightly laminated, yellow–brown to dark brown up to brown–blackish, sometimes telescopic and rarely frayed at the ends. Trichomes narrowed to the apex, not constricted at crosswalls, continually narrowed to the not very long, cellular hair, which is §0.8–1 m wide; constrictions are rare only in young trichomes and hormogonia. Cells shortly cylindrical, shorter than wide, rarely up to isodiametrical, mostly olive-green, dirty blue–green to yellow–brown,

123

slightly granulated, only toward ends (in hairs) elongated and §hyaline. Heterocytes basal, subspherical to slightly oval, hyaline, unipored, very rarely two together; rarely develop intercalary, slightly oval heterocytes. Akinetes were not observed. Reproduction by disintegration of thallus and (2)6-10(12)-celled, monoseriate hormogonia, which are usually 5–7 m wide. A few morphologically and ecologically identical strains were isolated from James Ross Island, from which strain BL 2 (CCALA 953) was used for experiments and molecular analyses. Other strains were contaminated in such a degree that the results (more or less identical) were not accepted for the Wnal evaluation. 16S rRNA gene sequencing found similarity below 94.5% to all other related Calothrix strains, which supports together with the morphological and ecological markers the taxonomic classiWcation on the speciWc level (Fig. 3).

Polar Biol (2012) 35:759–774

765

Fig. 5 Calothrix elsteri: a–f natural material, g–j strain CCALA 953; a–b solitary trichomes, c germinating hormogonia, d detail of a basal heterocyte, e small colony, f Wlaments in developed mats; g growth of

trichomes on agar plates, h–i solitary trichomes from a culture (brown sheaths disappeared), j liberated hormogonia

Diagnosis

gata, plus minusve ad 360 m longa, basim 11–16 m lata, ad apices longe capilliformes. Vaginae Wrmae, tenues vel paucim dilatatae, paucim laminosae, luteo-fuscae ad intense fuscae, interdum apice Xabelliformes. Trichoma

Filamenta heteropolares, Xexuosa, solitaria vel in coloniarum irregularis, planis, graminiformes, epilithicis aggre-

123

766

Polar Biol (2012) 35:759–774

Fig. 6 Phylogenetic tree of related and morphologically similar Coleodesmium and Hassallia strains. The support values are given for Maximum likelihood, Maximum parsimony, and Bayesian posterior probabilities. The cutoVs for bootstrap and probability values are 50 (0.5 resp). Our strains are printed bold

cum heterocytis basalibus, ad dissepimenta not constricta, ad apices tenuis hyalinisque deinceps ad 0.8 m attenuata. Cellulae breve cylindricae ad quadraticae, aeruginosae vel olivaceae ad luteo-fuscae, paucim granulosae, in capillis elongatae at plus minusve hyalinae. Heterocytae basales, subsphaericae vel paucim ovales, hyalinae, cum poro unico, raro binae, rarissime intercalares. Sporae carentes. Reproductio disintegratione Wlamentis, vel hormogoniis uniseriatis, 2–12-cellularibus, 5–7 m latis.—Typus: exsiccatum No BRNM HY2360 in depositum (Moravian Museum Brno, Czech Republic); icona typica: Wgura nostra 4; cultura typica: CCALA 953.—Habitatio: ad saxa inundata cum incrustationibus calcareis, in partes littoralibus lacubus antarcticis; locus classicus: lacus “Black Lake” dictus, James Ross insula, Mare Weddell. Etymology Species ad honorem Assoc. Prof. Josef Elster, Ph.D. (Tlebok, Czech Republic), chief of the phycological program at the Czech Antarctic scientiWc station “Johann Gregor Mendel”, nominata. Ecology Basic characteristics of lake water were measured in the lakes with C. elsteri as the dominant component of benthic mats (Green Lake I, II and Black Lake). Due to the geological character of their catchments (basalts), pH of the lakes was alkaline (7.6–8.6). The lakes were ice free during the Antarctic summer season, with temperature of the lake water slightly surpassing 10°C on sunny days. Conductivity was 50–130 S cm¡1, and the concentration of dissolved oxygen was 12.0–13.7 mg l¡1 (100% saturation to 128% oversaturation). Concentration of chlorophyll-a in the lake water ranged from 1 to 6 g l¡1.

123

The lake habitat of C. elsteri is characterized by marked water level Xuctuations. During the summer season, a large part of the littoral becomes dry and its striking black color is caused by the desiccated mats with dominance of C. elsteri. In Green Lake I and II, benthic mats on stones are co-dominated by an unknown Wlamentous green alga from the genus Pseudendoclonium, which forms macroscopic, roughly circular tufts. Simple Wlamentous Phormidium sp. and Leptolyngbya sp. are also present in the mats, together with pennate diatoms. An interesting feature of mats in the Green Lakes is their mineralization (formation of macroscopic crystals of calcium carbonate), which was observed on stones. The benthic community in Black Lake is also dominated by C. elsteri. This species is accompanied by macroscopic spherical colonies of Nostoc sp., coccal green algae, and pennate diatoms. Hassallia andreassenii and H. antarctica Various populations, corresponding phenotypically to the related cyanobacterial genera Coleodesmium and/or Hassallia, occur in various freshwater habitats in the maritime, coastal areas in Antarctica. Four strains from this group (Table 1), which were studied in detail, were isolated from the littoral of Green Lake I and II, and surrounding seepages (Figs. 1, 2). After analyses by 16S rRNA gene sequencing, it was found that the whole cluster contains two taxonomic types corresponding both genetically and morphologically to the cluster (genus) Hassallia (Fig. 6) and it is related both morphologically and genetically to the genus Coleodesmium. Morphological features of both types also correspond in main markers (structure of thallus, type of false branching, structure of trichomes, position of heterocytes) to this generic unit. Both these subgeneric types diVer also ecologically.

Polar Biol (2012) 35:759–774

767

Fig. 7 Hassallia andreassenii, natural material: a–d variability of fasciculated colonies, e–g terminal parts of Wlaments, h detail of an old part of a Wlament, i–k production of hormogonia and monocytes, l–n various types of heterocytes, o necridic cell, p–r germination hormogonia with heterocytes. Orig

The most characteristic strains were selected as reference strains of H. andreassenii (CCALA 954) and H. antarctica (CCALA 957) and used for 16S rRNA gene sequencing. The diVerence in % of similarity between both these strains was larger than 1.5% (98.4% of similarity). Hassallia populations (both species) grow also in two diVerent microhabitats: (i) Populations with slightly narrower trichomes belong particularly to communities with characteristic structure growing on the surface of stones and participating on the formation of calcareous precipitates (H. andreassenii). This type is therefore ecologically important, particularly in stony littoral zones of lakes, in which arise limestone precipitates. (ii) The second type of Hassallia (H. antarctica) occurs mainly in macroscopic clusters in

spaces between stony blocks in the littoral parts of the lake. They are continually Xooded by water and partly attached to stony walls. Morphologically similar smaller populations occur in slightly diVerent habitats (wetted rocks), but their relation is not yet clear. Because both these strains are distinguishable ecologically and morphologically and diVer distinctly in the phylogenetic tree (comp. strains CCALA 954 and CCALA 957), we designate them as separate species, H. andreassenii and H. antarctica (comp. Figs. 6, 7, 8, 9, 10). These species of the genera Hassallia, being related and morphologically similar to Coleodesmium, were compared with other species of this genus (cf. Komárek and Watanabe 1990) and with strains available in GenBank (Fig. 6).

123

768

Polar Biol (2012) 35:759–774

Fig. 8 Hassallia andreassenii: a–d natural material, e–f trichomes from culture CCALA 954

Hassallia andreassenii spec. nova Morphological characters (Figs. 7, 8) Filaments grow in macroscopically visible, yellow brown to brown Xat mats with fasciculated Wlaments, falsely branched; branches tightly joined to the main Wlaments. Filaments and branches of the same morphology, 12.4–20 m wide. Sheaths Wrm, thick, laminated, dark brown, cylindrical, Wrstly closed, later open, or gelatinized at the ends. Trichomes cylindrical, not constricted at cross-walls (very rarely slightly constricted), 7.5–13 m wide, sometimes slightly narrowed at the ends. Cells cylindrical, in the upper parts usually shorter than wide, less frequently (in old trichomes) cylindrical up to slightly longer than wide, with blue-green or olive-green content, sometimes with scarce larger granules, terminal cells widely rounded. Heterocytes basal and intercalary, solitary, rarely up to 2(3) in a row,

123

spherical, hemispherical, cylindrical, ovoid or slightly oval, developing particularly at the base of branches. Akinetes not known. Reproduction mainly by solitary cells (monocytes) or up to 12-celled hormogonia, not constricted at cross-walls, separated by help of necridic cells. One strain was isolated from calcareous precipitates in Green Lake II, Ulu Peninsula (near Andreassen point), James Ross Island, Antarctica. We describe taxonomically the species based on the type and reference strain CCALA 954. Diagnosis Filamenta irregulariter in fasciculis fuscis, microscopicis ad macroscopicis aggregata, cum multis ramiWcationibus falsis, heteropolaribus, in partes basales ad terminales separantur; rami plus minusve arcte simul paralleliterque aggregati. Filamenta ramique pariter lata, cylindrica, 12.4–20.0 m lata. Vaginae Wrmae, latae, plerumque apice apertae, laminosae,

Polar Biol (2012) 35:759–774

769

Fig. 9 Hassallia antarctica, natural population: a–c variability of branched colonies, d scheme of the branched colony, e terminal parts of branches, f–g details of Wlaments, h–i branching of young Wlaments, j–k disintegration of Wlaments in hormogonia, l–m germinating hormogonia

fuscae, raro clausae ad apice gelatinosae. Trichoma cylindrica, praecipue ad dissepimenta not constricta vel paucim constricta, 7.5–13 m lata, rarissime ad apices paucim angustata. Cellulae cylindricae, brevior quam latae in partes apicalibus, in trichomatis adultis interdum paucim longior quam latae, aeruginosae vel olivaceae, interdum cum granulis magnis solitariis; cellulae terminales, plus minusve rotundatae. Heterocytae basales ad intercalares, solitariae, rare ad 3 in series, sphaericae, hemisphaericae, cylindricae, ovales, praecipue basim ramis evolutae. Sporae carentes. Reproductio monocytis vel hormogoniis ad 12-cellularibus, ad dissepimenta not constrictis, cum necridiis separantur.— Typus: exsiccatum No BRNM HY 2361 depositum; icona

typica: Wgura nostra 7; cultura typica: CCALA 954.—Habitatio: Ad saxa inundata cum incrustacionibus calcareis, in partes litoralibus lacubus antarcticis; locus classicus: lacus “Green LakeII” dicto, James Ross insula, Mare Weddell. Etymology The speciWc epitheton was selected according to the name of the original locality. The type strain was isolated from the Antarctic Green Lake II, situated near Andreassen Point, which was called after a member of the Nordenskiöld’s expedition, which discovered and described this part of Antarctica.

123

770

Polar Biol (2012) 35:759–774

Fig. 10 Hassallia antarctica: a–e natural samples, f–h Wlaments from culture (CCALA 957): a–b small fasciculated colonies, c germinating hormogonia, d–e type of branching, f young Wlaments, g branching of young Wlaments, h trichomes from old culture. Orig

Ecology

Hassallia antarctica spec. nova

Hassallia andreassenii is a part of the microalgal/cyanobacterial community participating in the formation of calcareous precipitates on the surface of stones in the littoral of the Xat lake Green Lake II. The basic characteristics of Green Lake II: pH = 8.6, conductivity 91 S cm¡1, concentration of dissolved oxygen 13.7 mg l¡1 (»130% saturation). The concentration of chlorophyll-a in the lake water was 1 g l¡1. H. andreassenii accompanies the dominant Calothrix elsteri in the littoral of Green Lake II.

Morphological characters (Figs. 9, 10)

123

Filaments heteropolar, grow in macroscopic, dark brown up to blackish fasciculated clusters, with false branching and branches slightly and irregularly divaricated. Filaments and branches are § of the same morphology, cylindrical, 11.2– 17.5 m wide. Sheaths Wrm, relatively thick, laminated, yellowish to yellow–brown, cylindrical, closed at the apex. Trichomes cylindrical, not constricted up to slightly

Polar Biol (2012) 35:759–774

constricted at cross-walls, (7.4)8.6–12.3 m wide. Cells cylindrical, up to shortly barrel-shaped, always distinctly shorter than wide, blue-green or olive-green, with slightly, irregularly granulated content; terminal cells rounded, sometimes larger that vegetative cells, longer and with hyaline content. Heterocytes mainly basal, intercalary (usually before the false branching), solitary or in pairs, rarely up to three in a row, hemispherical, rarely up to oval, sometimes slightly complanated, of the same width as the vegetative cells. Akinetes not known. Reproduction by hormogonia, mostly 7–8 m wide, (2)4-12(14)-celled. The three isolated strains from all studied Antarctic habitats have slightly diVerent genetic diversity. Diagnosis Filamenta heteropolares, cum partes basalibus ad terminalibus, plus minusve Xexuosa vel arcuata, in fasciculis fruticosis, irregularis, fuscis ad atrofuscis, consociata, false ramiWcata, cum ramis paucim irregulariterque divaricatis. Filamenta ramique pariter cylindrice, plus minusve 11.2– 17.5 m lata. Vaginae Wrmae, laminatae, lutescentes vel luteo-fuscae, saepe apice clausae. Trichoma cylindrica, ad dissepimenta not vel constricta, 7.4–12.3 m lata. Cellulae cylindricae ad breve barriliformes, semper brevior quam latae, aeruginosae vel olivaceae, contentu paucim granuloso; cellulae terminales distinctae, interdum paucim dilatatae, rotundatae et contentu hyalino. Heterocytae praecipue basales, intercalares ante ramiWcationibus, solitariae vel binae, hemisphaericae ad ovales, interdum paucim complanatae, 7.5–12.5 m latae. Akinetes carentes. Reproductio praecipue hormogoniis, 2–14-cellularis, 7–8 m latis.— Typus: exsiccatum No BRNM HY 2362 depositum; icona typica: Wgura nostra 9, cultura typica: CCALA 957.—Habitatio: Inter saxis in partes litoralibus lacubus, ad saxis humosis, in fossis vel paludis antarcticis, facultative inundatis; locus classicus: in partes litoralibus lacus “Green Lake I” dicto, James Ross insula, Mare Weddell. Etymology The species is named according to the specialized, original locality on the Antarctic continent. Ecology Hassallia antarctica grows in similar localities as H. andreassenii; however, their preferences of microhabitat are diVerent. In contrast to the epilithic growth of Calothrix elsteri and H. andreassenii, H. antarctica was found in stone crevices, being only loosely attached to the substrate. It has also a wider distribution in coastal Antarctica and wider ecological plasticity. It develops in water between

771

stony blocks in the littoral of lakes and occurs also in localities in seepages (in water among stones) or on dripping rocks (localities—James Ross Island: among littoral stones in both Green Lakes I and II, seepages near Lachman Lake, littoral of Monolith Lake; King George Island: wet rocks in SW shore of Maxwell Bay).

Discussion The modernization of cyanobacterial taxonomy, especially according to molecular methods, continues to pose a number of challenging problems. For example, the species concept for cyanobacteria is still unclear, as with numerous other prokaryotic organisms (Castenholz 1992; Johansen and Casamatta 2005 and others). However, the identiWcation of cyanobacterial infrageneric units is important for various ecological and experimental investigations, which is the reason why morphologically characterized taxa (traditional species), derived from old, morphologically oriented taxonomy with the traditional nomenclature, are still commonly used. Especially in multicellular types of cyanoprokaryotes, where the morphological infrageneric diversity is wide (sometimes of such a degree that some phenotypic markers are often in agreement with the phylogenetic characteristics), the speciWc units can be satisfactorily deWned. We accept therefore the more or less conventional species concept, which is formulated, e.g., in Komárek (2010, p. 254), and which corresponds to the present knowledge of cyanobacterial diversity. The aYliation of all species to the same genotype, a small diVerence (usually between 95 and 99% genetic similarity) in phylogenetic evaluation (identiWed by 16S rRNA gene sequences) and the presence of autapomorphic morphological markers are the basic criteria of this species concept, which we have used also in the deWnition of our taxa (Johansen and Casamatta 2005; Komárek 2011). Our new species from James Ross Island correspond with the present criteria for species delimitation. The genus Calothrix is surely heterogeneous according to morphological characters as well as the phylogenetic positions of individual strains. Up to now, they were not many Calothrix strains sequenced, but they occur in a few diVerent positions in the tree derived from 16S rRNA gene sequencing (Fig. 3). Our representative strain from Antarctic habitats belongs in the cluster of other typical Calothrix-types, but diVers in their genetic similarity (94.5%) and clearly by phenotype and ecological markers. Several special species of Calothrix were described from Antarctica already by Fritsch (1912; C. antarctica, C. gracilis, C. intricata). These species were recorded also by later authors (comp. Prescott 1979), but they diVer substantially in their morphological characters from our populations. Also Calothrix

123

772

parietina (Broady 1986, 1996; Ohtani 1986; Ohtani and Kanda 1987) or Calothrix cf. parietina (Broady 1989), which were usually recorded in previous phycological papers from Antarctica, can belong in the similar taxonomic group as our C. elsteri. However, C. parietina, which is considered cosmopolitan, is highly variable according to the literature, occurs in an enormous number of various habitats, and is published in diVerent concepts. The genetic identity of all such morphologically, ecologically, and geographically diverse populations is quite impossible and it is not yet solved. The Antarctic populations are usually not documented. A very good drawing was presented by Ohtani (1986), but it is only one from many later concepts of C. parietina and the identity with the type is questionable. The diversity of “Calothrix parietina types” can be solved only by molecular analyses. For C. elsteri, the combination of its unique ecology and distinct morphology (clearly diVerent also from the original concept of C. parietina), and isolated position in the phylogenetic tree (inside of the genus Calothrix—see Fig. 3), collectively provides strong support for description this taxon as a distinct species. Another Calothrix species (C. epiphytica), cited from Antarctica by Hirano (1965), is known mostly from European freshwaters with plenty of vegetation and its occurrence in Antarctica is improbable. It is interesting that the mat formed by C. elsteri contained abnormal phospholipids with very-long-chain anteiso branched fatty acids (from C20 to C30; Iezanka et al. 2009). Concerning algae and cyanobacteria, the presence of these fatty acids was reported only in cryptoendolithic microbial communities from Antarctica up to now (Matsumoto et al. 1992). Only a few strains of Hassallia or Coleodesmium were sequenced to date (cf. Flechtner et al. 2002). The genus Hassallia is genetically near to Coleodesmium, and both types are very hard to distinguish morphologically (morphology of cells, type of false branching). Hassallia has not yet been recorded from localities in continental Antarctica. Both of the genera Hassallia and Coleodesmium were not accepted in old identiWcation manuals and they are also not commonly mentioned in Antarctic papers (comp. Prescott 1979). However, similar types were usually identiWed by authors working only with morphological features as members of the genus Tolypothrix. Prescott (1979) mentioned several species from continental Antarctica (without subantarctic islands). T. bouteillei, which is recently also classiWed into the genus Hassallia, was recorded by Akiyama (1968) and Broady et al. (1987), but the ecology of the type species is very diVerent and its identity with Antarctic populations is improbable. Another species, T. conglutinata, is cited by Wille (1924) and Hirano (1965); however, it is a very problematic species, originally described from wet rocks in Italy. Other species, e.g., T. fragilis (Akyiama

123

Polar Biol (2012) 35:759–774

1968) and T. tenuis (Broady 1986, 1996) have diVerent ecologies, and their presence in Antarctica should be conWrmed by molecular methods. A detailed drawing, which resembles well our Hassallia species, was published by Ohtani (1986) as Tolypothrix sp. as epiphytic on mosses near Syowa Station. The genetic relatedness of this specimen with our material is quite probable. All of these types are similar also to the genus Coleodesmium, but their phylogenetic position (according to our analyses) is located inside the Hassallia cluster. Our populations are also morphologically diVerent from any Coleodesmium species known from other habitats and regions (cf. Komárek and Watanabe 1990). In comparison with up to now described species of the genus, H. andreassenii represents clearly a special type inside the Hassallia cluster (cf. Komárek and Watanabe 1990; Flechtner et al. 2002), which is well characterized also morphologically and phenotypically. The species H. andreassenii is particularly ecologically limited in a special Antarctic habitat and occurs only among calcareous precipitates in the littoral of Antarctic lakes near the east coast of the Ulu Peninsula. It is interesting that the typical strain of H. andreassenii is phylogenetically close to the strain AY493596, designated as Coleodesmium sp. (in GenBank), also isolated from Antarctica. H. antarctica is related to the characteristic species of Hassallia, which was already sequenced (H. byssoidea), but both types diVer slightly genotypically one from another and distinctly by their morphology and ecology. H. antarctica seems to have a wider ecology and was found in more variable habitats (littoral of lakes, wet rocks, seepages). It is also distributed in more various microhabitats, e.g., in the littoral zone of lakes in seepages and on wet rocky walls. However, its respective distribution outside of the Antarctic continent should be controlled. All of our species were studied Wrstly from natural populations and later isolated in unialgal monospeciWc cultures. This method enabled their polyphasic evaluation, based on molecular sequencing and study of their morphological variability. However, comparison of the same populations from nature and cultures proved that all strains change substantially their morphology after isolation (disappearance of typical form of colonies, modiWed and reduced false branching, reduction of sheaths, etc.). The taxonomic description of strains and species only from culture conditions must be done therefore very carefully with respect to the original material from nature. It is necessary to mention also the function of Calothrix species in various ecosystems of polar regions. It was stressed in Arctic ecosystems, e.g., by Gardel and Drouet (1960) or Vincent (2000), and the phylogenetic and ecological comparison of populations from similar subpolar habitats will be important. The same is valid for the

Polar Biol (2012) 35:759–774

Coleodesmium/Hassallia taxonomic complex, the occurrence of which in both polar regions should be compared more in detail in future comparative studies. Another problem concerns the ecology and geographic distribution of cyanobacterial Antarctic populations. Up to now, numerous Antarctic cyanobacteria have been suggested to have a widespread global distribution based on morphological or molecular analyses (e.g., Wynn-Williams 1991; Broady and Smith 1994; Jungblut et al. 2010). However, just the paper of Jungblut et al. (2010) (and also other similar studies, e.g., Taton et al. 2003, 2006) yields a perfect documentation of existence of isolated phylogenetic clusters in polar regions (“cold ecotypes”, “Arc”- genotypes). A wide distribution of our three species is improbable outside Antarctica. They were found (in rich populations) under very speciWc extreme and unique ecological situations in isolated habitats of Antarctic lakes, where they play continually a dominant role in communities, which are fully adapted to the speciWc conditions. They could be present in similar habitats in other cold environments, but they represent clusters, which were not yet conWrmed from other populations outside Antarctica, especially by molecular gene sequencing (data of this problematic see also in Garcia-Pichel et al. 1998; Garcia-Pichel 2008, etc.). Similar situation concerns also other taxonomic groups. For example, the study of freshwater diatoms of Ulu Peninsula resulted in the description of several new species and conWrmed the presence of a highly speciWc Xora in the lakes and seepages (Kopalová et al. 2011). Acknowledgments This study was conducted during the stay of the authors in the Polish Antarctic station Henryk Arctowski in 2004–2005 (headed by Prof. Stanisiaw Rakusa-Suszczewski and Prof. Adam Barcikowski) and mainly in the Czech station J.G. Mendel (headed by Prof. Pavel Pronek and Prof. Milon Barták) in 2007 and 2009. We are indebted particularly to Assoc. Prof. Josef Elster for all support of our work, help, and valuable data. The access to the MetaCentrum computing facilities provided under the programme “Projects of Large Infrastructure for Research, Development, and Innovations” LM2010005 funded by the Ministry of Education, Youth, and Sports of the Czech Republic is appreciated/acknowledged. The technical work in laboratories was performed by Jana Knokhousová and Dana Kvehlová. We thank Dr. Keith Edwards for language correction. The work was supported by grants AV0Z60050516, IAA600050704, MSM6007665801, MSM0021620828 and GA CR 206/08/0318.

References Akiyama M (1968) A list of terrestrial and subterranean algae from the Ongul Islands, Antarctica. Antarct Rec 32:71–77 Boyer SL, Johansen JR, Flechtner VR, Howard GL (2002) Phylogeny and genetic variance in terrestrial Microcoleus (Cyanophyceae) species based on sequence analysis of the 16S rRNA gene and associated 16S–23S its region. J Phycol 38:1222– 1235 Broady PA (1986) Ecology and taxonomy of the terrestrial algae of the Vestfold Hills. In: Pickard J (ed) Antarctic Oasis: terrestrial envi-

773 ronments and history of the Vestfold Hills, chapter 6. Academic Press, Australia, pp 165–202 Broady PA (1989) Survey of algae and other terrestrial biota at Edward VII Peninsula, Marie Byrd Land. Antarct Sci 1:215–224 Broady PA (1996) Diversity, distribution and dispersal of Antarctic terrestrial algae. Biodivers Conserv 5:1307–1335 Broady PA, Kibblewhite AL (1991) Morphological characterization of Oscillatoriales (Cyanobacteria) from Ross-Island and Southern Victoria Land, Antarctica. Antarct Sci 3:35–45 Broady PA, Smith RA (1994) A preliminary investigation of the diversity, survivability and dispersal of algae introduced into Antarctica by human activity. Proc NIPR Symp Polar Biol 7:185–197 Broady PA, Given D, GreenWeld L, Thompson K (1987) The biota and environment of fumaroles on Mt Melbourn, Northern Victoria Land. Polar Biol 7:97–113 Casamatta DA, Johansen JR, Vis ML, Broadwater ST (2005) Molecular and morphological characterization of ten polar and near-polar strains within the Oscillatoriales (Cyanobacteria). J Phycol 41:421–438 Castenholz RW (1992) Species usage, concept, and evolution in the cyanobacteria (blue-green algae). J Phycol 28:737–745 Czech Geological Survey (2009) James Ross Island—Northern Part. Topographic map 1:25000, CGS, Praha Flechtner VR, Boyer SL, Johansen JR, DeNoble ML (2002) Spirirestis rafaelensis gen. et sp. nov. (Cyanophyceae), a new cyanobacterial genus from arid soils. Nova Hedwigia 74:1–24 Fritsch FE (1912) Freshwater algae. National Antarctic “Discovery” Expedition 1901–1904. British Mus Nat Hist 6:1–66 Garcia-Pichel F (2008) Molecular ecology and environmental genomics of Cyanobacteria. In: Herrero A, Flores E (eds) The Cyanobacteria. Molecular biology, genomics and evolution. Caister Academic Press, Norfolk, pp 59–87 Garcia-Pichel F, Nübel U, Muyzer G (1998) The phylogeny of unicellular, extremely halotolerant cyanobacteria. Arch Microbiol 169:469–482 Gardel RW, Drouet F (1960) The cyanobacteria of the Thule area, Greenland. Trans Am Microsc Soc 79:256–272 Gordon DA, Priscu JC, Giovannoni S (2000) Origin and phylogeny of microbes living in permanent Antarctic lake ice. Microb Ecol 39:197–202 Gouy M, Guindon S, Gascuel O (2010) SeaView version 4: a multiplatform graphical user interface for sequence alignment and phylogenetic tree building. Mol Biol Evol 27:221–224 Hall TA (1999) BioEdit: a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. Nucl Acids Symp Ser 41:95–98 Hirano M (1965) Freshwater algae in the Antarctic region. In: van Mieghem J, van Oye P, Schell J (eds) Biogeography and ecology in Antarctica, vol. 15. Monogr Biol, pp 127–193 Hjort C, Ingólfsson Ó, Möller P, Lirio JM (1997) Holocene glacial history and sea-level changes on James Ross Island, Antarctic Peninsula. J Quart Sci 12:259–273 Huelsenbeck JP, Ronquist F (2001) MRBAYES: Bayesian inference of phylogeny. Bioinformatics 17:754–755 Johansen JR, Casamatta DA (2005) Recognizing cyanobacterial diversity through adoption of a new species paradigm. Algolog Stud 117:71–93 Jungblut AD, Hawes I, Mountfort D, Hitzfeld B, Dietrich DR, Burns BP, Neilan BA (2005) Diversity within cyanobacterial mat communities in variable salinity meltwater ponds of McMurdo Ice Shelf, Antarctica. Environ Microbiol 7:519–529 Jungblut AD, Lovejoy C, Vincent WF (2010) Global distribution of cyanobacterial ecotypes in the cold biosphere. ISME J 4:191–202 Katoh K, Misawa K, Kuma K, Miyata T (2002) MAFFT: a novel method for rapid multiple sequence alignment based on fast Fourier transform. Nucleic Acids Res 30:3059–3066

123

774 Komárek J (1999) Diversity of cyanoprokaryotes (cyanobacteria) of King George Island, maritime Antarctica—a survey. Algolog Stud 94:181–193 Komárek J (2010) Recent changes (2008) in cyanobacterial taxonomy based on a combination of molecular background with phenotype and ecological consequences (genus and species concept). Hydrobiologia 639:245–259 Komárek J (2011) Introduction to the 18th IAC Symposium in Beské Bud5jovice 2010, Czech Republic. Some current problems of modern cyanobacterial taxonomy. Fottea 11:1–7 Komárek J, Elster J (2008) Ecological background of cyanobacterial assemblages of the northern part of James Ross Island, NW Weddell Sea, Antarctica. Pol Polar Res 29:17–32 Komárek J, Watanabe M (1990) Morphology and taxonomy of the genus Coleodesmium (Cyanophyceae/Cyanobacteria). In: Watanabe M, Malla SR (eds) Cryptogams of the Himalayas, vol 2, Central and Eastern Nepal, Tsukuba, pp 1–22 Komárek J, Elster J, Komárek O (2008) Diversity of cyanobacterial microXora of the northern part of James Ross Island, NW Weddell Sea, Antarctica. Polar Biol 31:853–865 Kopalová K, Nedbalová L, De Haan M, de Vijver BV (2011) Description of Wve new species of the diatom genus Luticola (Bacillariophyta, Diadesmidaceae) found in lakes of James Ross Island (Maritime Antarctic Region). Phytotaxa 27:44–60 Matsumoto GI, Friedmann EI, Watanuki K, Ocampo-Friedmann R (1992) Novel long chain anteiso-alkanes and anteiso-alkanoic acids in Antarctic rocks colonized by living and fossil cryptoendolithic microorganisms. J Chromatogr 598:267–276 Nadeau TL, Milbrandt EC, Castenholz RW (2001) Evolutionary relationships of cultivated Antarctic oscillatorians (cyanobacteria). J Phycol 37:650–654 Nübel U, Garcia-Pichel F, Muyzer G (1997) PCR primers to amplify 16S rRNA genes from cyanobacteria. Appl Environ Microbiol 63:3327–3332 Ohtani S (1986) Epiphytic algae on mosses in the vicinity of Syowa Station, Antarctica. Mem Natl Inst Polar Res 44:209–219 Ohtani S, Kanda H (1987) Epiphytic algae on the moss community of Grimmia lawiana around Syowa Station, Antarctica. Proc NIPR Symp Polar Biol 1:255–264

123

Polar Biol (2012) 35:759–774 Pechar L (1987) Use of an acetone: methanol mixture for the extraction and spectrophotometric determination of chlorophyll-a in phytoplankton. Algolog Stud 46:99–117 Prescott GW (1979) A Contribution to a bibliography of Antarctic and Subantarctic Algae. Bibliotheca Phycol 45:312 Iezanka T, Nedbalová L, Elster J, Cajthaml T, Sigler K (2009) Very-long-chain iso- and anteiso-branched fatty acids in N-acylphosphatidylethanolamines from a natural cyanobacterial mat of Calothrix sp. Phytochemistry 70:655–663 Strunecký O, Elster J, Komárek J (2010) Phylogenetic relationships between geographically separate Phormidium cyanobacteria: is there a link between north and south polar regions? Polar Biol 33:1419–1428 Taton A, Grubisic S, Brambilla E, de Wit R, Wilmotte A (2003) Cyanobacterial diversity in natural and artiWcial microbial mats of Lake Fryxell (McMurdo Dry Valleys, Antarctica): a morphological and molecular approach. Appl Environ Microbiol 69:5157–5169 Taton A, Grubisic S, Balthasart P, Hodgson DA, Laybourn-Parry J, Wilmotte A (2006) Biogeographical distribution and ecological ranges of benthic cyanobacteria in East Antarctic lakes. FEMS Microbiol Ecol 57:272–289 Vincent WF (2000) Cyanobacterial dominance in the polar regions. In: Whitton B, Potts M (eds) Ecology of the Cyanobacteria: their diversity in space and time. Kluwers Academic Press, The Netherlands, pp 321–340 Wille N (1924) Süsswasseralgen von der Deutschen Südpolar-Expedition auf dem SchiV „Gauss“. I. Teil. Süsswasserlagen vom antarktischen Festlande. Deutsche Südpolar-Expedition 1901–1903. Auftr Reichsmin Botanik 8:373–407 Wilmotte A, Van der Auwera G, De Wachter R (1993) Structure of the 16 S ribosomal RNA of the thermophilic cyanobacterium Chlorogloeopsis HTF (‘Mastigocladus laminosus HTF’) strain PCC7518, and phylogenetic analysis. FEBS Lett 317:96–100 Wynn-Williams DD (1991) Aerobiology and colonization in Antarctica. In: Hjelmroos M et al (eds) Proc 4th Internat Conference Aerobiol, Stockholm, 1990, vol 30, pp 380–393 Yilmaz M, Philips EJ, Tillett D (2009) Improved methods for the isolation of cyanobacterial dna from environmental samples. J Phycol 45:517–521