Chlorophyta, Chlorophyceae): Life Cycle and Taxonomy

Fottea 12(1): 75–81, 2012 75

Ettliella tetraspora (Chlorophyta, Chlorophyceae): life cycle and taxonomy

František Hi n d á k & Alica Hi n d á k o v á

Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK–84523 Bratislava, Slovakia; e–mail: [email protected]; [email protected]

Abstract: The morphology and mode of reproduction in Ettiella tetraspora Hi n d á k 1988, a green coenobial alga described from the Czech Republic and Finland, were studied from the plankton of the water reservoir Förmitzspeicher in NE Bavaria, Germany. The morphology of cells and coenobia of the species in this population was in agreement with published data for the species, but its reproduction was not of the Oocystis – type as it has been declared in the relevant literature. The protoplast of mother cells does not divide simultaneously into 4 autospores as in many coccal green algae, but always in two autospores. The first division of the mother cell is perpendicular to the longitudinal axis of the cell and two walled daughter cells arise. Subsequently, the newly formed daughter cells divide again, but this time perpendicular to the new formed cell cross wall. Ultimately, in a new coenobium all four daughter cells are arranged in parallel. Daughter cells remain inside a slightly enlarged mother cell wall (well visible only near the cross wall) and are released by its gelatinisation. Such subsequent production of four autospores from the mother cell represents a special type of multiplication in the green coccal algae known also in some other species [e.g. Tetrastrum komarekii Hi n d á k 1977, Willea irregularis (Wi l l e ) Sc h m i d l e 1900, Makinoella tosaensis Ok a d a 1949].

Key words: autospores subsequent division, coenobial green algae, taxonomy, Oocystaceae, Scenedesmaceae, Germany

Introduction autosporulation and therefore he assigned the alga to the family Oocystaceae. When Hi n d á k During a workshop devoted to the determination (1988) established this alga as a new genus and of planktic cyanophytes and chlorophytes of species, Ettliella tetraspora, he followed this lakes and reservoirs organised by the Bavarian classification, although the release of autospores Regional Office for the Environment (Bayerisches and remnants of mother cell walls were not Landesamt für Umwelt) in Wielenbach, Germany, observed in detail. It was noticed, however, that in July 2010, samples from several local water the regular Tetradesmus – like clustering of cells bodies were analysed. In the phytoplankton sample of Ettliella is reminiscent of some representatives collected from the water reservoir Förmitzspeicher of the family Coelastraceae or Scenedesmaceae. a rare coccal green alga, Ettliella tetraspora, was In one phytoplankton sample from Bavaria, observed. coenobia of Ettliella tetraspora occurred quite The monotypic genus Ettliella Hi n d á k abundantly, thereby offering an opportunity to 1988 including E. tetraspora Hi n d á k 1988 was study the process of autosporulation in all its described on the basis of two observations. Et t l stages. These observations led to the conclusion (1965) was the first to find the alga in a fishpond that the mother cell wall does not expand before near Svitavy in Moravia, the Czech Republic, the liberation of autospores as in the Oocystaceae. but designated it as Tetrachlorella cf. alternans Probably Et t l (1965) did not depict expanded mother cell walls around daughter coenobia, but Ko r sh i k o v (?nov. var.) (cf. also Ko m á r e k & mucilaginous envelopes newly formed around Fo t t 1983; Hi n d á k 1988). Later, Hi n d á k (1988) autocoenobia. observed it in a lake near Jyväskylä, Central Finland. The morphology of cells and colonies and the formation of autospores were similar Material and Methods in material from both localities. Ettl was of the opinion that the mother cell wall expands during Plankton samples were collected from the water 76 Hi n d á k & Hi n d á k o v á : Ettliella tetraspora (Chlorophyta, Chlorophyceae) reservoir Förmitzspeicher (Förmitzsee) near or cells solitary before reproduction, embedded Schwarzenbach a.d. Saale, NE Bavaria, Germany, pH by wide homogeneous hyaline mucilaginous 7.9, July 5, 2010, by Mrs C. Hauenschild, Hof, using a envelopes. Cells in coenobia clustered into tetrads plankton net with 10 µm mesh size (Fig. 1). as in Tetradesmus G.M. Sm i t h , i.e. positioned (but Cyanophytes and algae were determined not joined) in parallel next to each other forming according to Ko r sh i k o v (1953), Hi n d á k (1977, 1980, 1984, 1988, 1990, 2008), Ko m á r e k & Fo t t a square when viewed from above, with a central (1983), Kr a m m e r & La n g e –Be r t a l o t (1986, 1988, opening (Figs 2–4). Cells broadly ovoid or short 1991a, b), Ko m á r e k & An a g n o s t i d i s (1998, 2005), cylindrical, before division slightly asymmetrical Ko m á r e k & Za p o m n ě l o v á (2007), Le n z e n w e g e r to kidney–shaped, 8–12(18) × 6–8(10) µm, ends (1999) and Ra j a n i e m i et al. (2005). Identifications broadly oval. Cell walls thick, smooth, without were performed on living material. Light microscope incrustations or conspicuous polar thickenings. observations were carried out with a Leitz Diaplan Chloroplasts single, bright green, parietal, microscope, and photomicrographs were taken with transversely pot–shaped, with a large central a Wild Photoautomat MPS45. Preserved material in formaldehyde is stored at the Institute of Botany SAS, starch–associated pyrenoid, and in cells in tetrads Bratislava. Attempts to cultivate this organism under oriented toward the external side. Reproduction by laboratory conditions were unsuccessful. autocoenobia with 4 autospores. Coenobia before autosporulation mostly disintegrating into solitary cells, losing their tetrahedrical arrangement of cells Results (Figs 5–8). When autospores are formed, colonies arise temporarily with tetrads of young cells, so Ettliella tetraspora Hi n d á k (Figs 2–9) that composite colonies exhibit cell tetrads of a Coenobia free floating, solitary, usually 4–8(16)– similar clustering (Figs 7–9). celled, ovoid to spherical, 40–60 µm in diameter, Although the product of autosporulation is one 4

Fig. 1. Locality where Ettiella tetraspora was collected: the water reservoir Förmitzspeicher in NE Bavaria, Germany (photo C. Hauenschild, summer 2010). Table 1. List of cyanophytes and algae found in the phytoplankton of the water reservoir Förmitzspeicher, Germany.

Cyanophyceae Chlorophyceae Aphanocapsa delicatissima W. et G.S. We s t Carteria globosa Ko r sh i k o v ex Pa s c h e r Aphanocapsa planctonica (G.M. Sm i t h ) Ko m á r e k et Chlamydomonas passiva Sk u j a An a g n o s t i d i s Eudorina elegans Eh r e n b e r g Aphanothece clathrata W. et G.S. We s t Asterococcus limneticus G.M. Sm i t h Aphanothece nidulans Ri c h t e r in Wi t t r o c k et No r d s t e d t Ankistrodesmus falcatus (Co r d a ) Ra l fs Chroococcus limneticus Le m m e r m a n n Ankistrodesmus spiralis (W.B. Tu r n e r ) Le m m e r m a n n Chroococcus minutus (Kü t z i n g ) Nä g e l i Botryococcus braunii Kü t z i n g Eucapsis minor (Sk u j a ) El e n k i n Closteriopsis acicularis (G.M. Sm i t h ) J.H. Be l c h e r et Merismopedia glauca (Eh r e n b e r g ) Kü t z i n g Sw a l e Merismopedia minima Be c k Coelastrum pseudomicroporum Ko r sh i k o v Microcystis aeruginosa (Kü t z i n g ) Kü t z i n g Coenochloris polycoccus (Ko r sh i k o v ) Hi n d á k Microcystis flos–aquae (Wi t t r o c k ) Ki r c h n e r Coenocystis planctonica Ko r sh i k o v Snowella litoralis (Hä y r é n ) Ko m á r e k et Hi n d á k Crucigeniella apiculata (Le m m e r m a n n ) Ko m á r e k Synechococcus endophyticus (W. et G.S. We s t ) Jo o s t e n Desmodesmus abundans (Ki r c h n e r ) E.H. He g e w a l d Woronichinia naegeliana (Un g e r ) El e n k i n Desmodesmus armatus (Ch o d a t ) E.H. He g e w a l d Oscillatoria limosa Ag a r d h ex Go m o n t Desmodesmus brasiliensis (Bo h l i n ) E.H. He g e w a l d Pseudanabaena catenata La u t e r b o r n Desmodesmus communis (E.H. He g e w a l d ) E.H. He g e w a l d Pseudanabaena mucicola (Na u m a n n et Hu b e r –Pe s t a l o z z i ) Desmodesmus dispar (Br é b i ss o n ) E.H. He g e w a l d Sc hw a b e Desmodesmus maximus (W. et G.S. We s t ) E.H. He g e w a l d Anabaena mucosa Ko m á r k o v á –Le g n e r o v á et El o r a n t a Desmodesmus serratus (Co r d a ) An, Fr i e d l et E.H. Anabaena planctonica Br u n n t h a l e r He g e w a l d Desmodesmus subspicatus (Ch o d a t ) E.H. He g e w a l d et A. Bacillariophyceae Sc h m i d t Aulacoseira ambigua (Gr u n o w ) Si m o n s e n Dictyosphaerium tetrachotomum Pr i n t z Cyclotella balatonis Pa n t o c z e k Ettliella tetraspora Hi n d á k Discostella pseudostelligera (Hu s t e d t ) Ho u k et Kl e e Komarekia appendiculata (Ch o d a t ) Fo t t Melosira varians C. Ag a r d h Monoraphidium griffithii(B e r k e l e y ) Ko m á r k o v á – Stephanodiscus medius Hå k a n ss o n Le g n e r o v á Achnanthes laevis Oe s t r u p Oocystella borgei (J. Sn o w ) Hi n d á k Achnanthes lanceolata ssp. frequentissima La n g e –Be r t a l o t Oocystella lacustris (Ch o d a t ) Hi n d á k Achnanthes minutissima Kü t z i n g Oocystella marssonii (Le m m e r m a n n ) Hi n d á k Achnanthes cf. petersenii Hu s t e d t Pediastrum biradiatum Me y e n Achnanthes cf. saccula J. R. Ca r t e r Pediastrum boryanum (Tu r p i n ) Me n e g h i n i Caloneis silicula (Eh r e n b e r g ) Cl e v e Pediastrum duplex Me y e n Cymbella gracilis (Eh r e n b e r g ) Kü t z i n g Pediastrum tetras (Eh r e n b e r g ) Ra l fs Cymbella silesiaca Bl e i s c h Pseudodictyosphaerium minusculum Hi n d á k Eunotia bilunaris (Eh r e n b e r g ) Mi l l s Pseudodidymocystis inconspicua (Ko r sh i k o v ) Hi n d á k Eunotia praerupta var. bidens (Eh r e n b e r g ) Gr u n o w Pseudokirchneriella contorta (Sc h m i d l e ) Hi n d á k Fragilaria crotonensis Ki t t o n Pseudokirchneriella irregularis (G.M. Sm i t h ) Hi n d á k Fragilaria tenera (W. Sm i t h ) La n g e –Be r t a l o t Scenedesmus acuminatus (La g e r h e i m ) Ch o d a t Fragilaria ulna var. acus (Kü t z i n g ) La n g e –Be r t a l o t Scenedesmus arcuatus (Le m m e r m a n n ) Le m m e r m a n n Frustulia vulgaris (Thw a i t e s ) De To n i Scenedesmus obliquus (Tu r p i n ) Kü t z i n g Gomphonema angustatum (Kü t z i n g ) Ra b e n h o r s t Scenedesmus obtusus Me y e n Gomphonema parvulum (Kü t z i n g ) Kü t z i n g Selenastrum bibraianum Re i n s c h Navicula capitata Eh r e n b e r g Tetraedron caudatum (Co r d a ) Ha n s g i r g Navicula capitatoradiata H. Ge r m a i n Willea irregularis Sc h m i d l e Navicula cryptocephala Kü t z i n g Navicula cryptotenella La n g e –Be r t a l o t Zygnematophyceae Navicula detenta Hu s t e d t Cosmarium circulare Re i n s c h Navicula rhynchocephala Kü t z i n g Cosmarium hornavanense Gu t w i n s k i Nitzschia angustiforaminata La n g e –Be r t a l o t Staurastrum cuspidatum Br é b i ss o n Nitzschia fonticola Gr u n o w Staurastrum mucronatum Ra l fs ex Ra l fs Nitzschia hantzschiana Ra b e n h o r s t Staurastrum planctonicum Te i l i n g Nitzschia cf. liebetruthii Ra b e n h o r s t Staurastrum punctulatum Br é b i ss o n Nitzschia palea (Kü t z i n g ) W. Sm i t h Nitzschia valdestriata Al e e m et Hu s t e d t Euglenophyceae Pinnularia divergens var. media Kr a m m e r Trachelomonas planctonica Sw i r e n k o Tabellaria flocculosa (Ro t h ) Kü t z i n g Figs 2–9. Coenobia of Ettiella tetraspora from natural material: (2) coenobia at low magnification; (3) coenobia from the top and lateral view; (4) coenobia from the lateral view; (5, 6) disintegration of coenobia; (7 – 9) division of cells into two daughter cells.

–celled coenobium, the protoplast of mother cells (Fig. 9). Finally, in a new coenobium all four and subsequently daughter cells divides always daughter cells are arranged in parallel (Fig. 3). into two steps. First division of the mother cell is Our material does not differ significantly perpendicular to the longitudinal axis of the cell from published descriptions of the species except and two walled daughter cells arise (Figs 7, 8). for the size of cells and coenobia, which are larger Subsequently, new daughter cells divide again, but than mentioned by Et t l (1965) or Hi n d á k (1988). perpendicular to the new cell wall. Daughter cells In contrast to a previous observation of the alga remain in a slightly enlarged mother cell wall near from Finland, 2–celled coenobia were not found the cross wall and are released by its gelatinisation in the German material. Fig. 10. Tetrastrum komarekii, formation of 4–celled coenobia. Fig. 11. Willea irregularis, formation of 4–celled coenobia.

Coenobia of E. tetraspora occurred but Ko m á r e k & Fo t t (1983) classified the genus quite abundantly among other members of the Tetrachlorella Ko r sh i k o v (together with T. cf. phytoplankton assemblage of the water reservoir alternans nov. var. (?) sensu Et t l ) in the family Förmitzspeicher. The cyanophycean water bloom Scenedesmaceae. However, the latter authors consisted mainly of colonies of Woronichinia noted that the parallel arrangement of cells in a naegeliana (Un g e r ) El e n k i n with endogloeic coenobium precludes the classification of this alga Synechococcus endophyticus (W. et G.S. We s t ) in the genus Tetrachlorella Ko r sh i k o v 1953 which Jo o s t e n (Hi n d á k 2008), Microcystis aeruginosa is characterised by flat coenobia, and suggested (Kü t z i n g ) Kü t z i n g and filaments of Anabaena that it might be considered as a new species and mucosa Ko m á r k o v á –Le g n e r o v á et El o r a n t a genus. Hi n d á k (1988) on the basis of material (Ko m á r e k & An a g n o s t i d i s 1998; Ra j a n i e m i from a Finnish lake accepted this opinion and et al. 2005; Ko m á r e k & Za p o m n ě l o v á 2007). established Ettliella tetraspora as a new member The diatoms Fragilaria crotonensis Ki t t o n and of the family Oocystaceae, although the release F. tenera (W. Sm i t h ) La n g e –Be r t a l o t were of autospores and remnants of mother cell walls amongst the dominant phytoplankton species. were not observed in detail. In the following list of found taxa we used the Successive cell division of mother cells classification system by Hi n d á k & Hi n d á k o v á into 4 autospores is character that is found also (1998), which has been adopted for the algal flora in other coccal green algae, e.g. Tetrastrum databank at our institute. komarekii Hi n d á k (Fig. 10), Willea irregularis The occurrence of Ettliella tetraspora in (Wi l l e ) Sc h m i d l e (Fig. 11) (Ko r sh i k o v 1953; the plankton of stagnant mesotrophic water basins Hi n d á k 1977, 1980, 1988; Ko m á r e k & Fo t t seems to be typical for the species. In the Czech 1983) and Makinoella tosaensis Okada (Hi n d á k Republic it was found in a fishpond near Svitavy & Hi n d á k o v á 2010). Although the final product (Et t l 1965), and we have reported this species of autosporulation in these genera is a 4–celled from the lake Patalakti near Jyväskylä in Finland coenobium, mother cells and subsequently (Hi n d á k 1988). However, St o y n e v a (2000) daughter cells do not divide simultaneously into 4 recorded E. tetraspora from the Alepou swamp, autospores, but always into two parts/autospores, a wetland on Southern Black Sea coast, Bulgaria, not in four or more parts/autospores like in many but did not provide a description or figure. coccal green algae. Similarly, the chloroplast divides before the protoplast division only in two portions, not in four. Discussion The placement of the genus Ettliella into a higher taxonomic unit is not yet clear. The mode of The taxonomic position of Ettliella tetraspora [as reproduction, together with the feature that mother Tetrachlorella cf. alternans Ko r sh i k o v (?nov. var.)] cell wall does not significantly enlarge before the in the Chlorococcales was originally determined release of autospores, precludes the placement of by Ettl, who placed it in the family Oocystaceae, Ettliella in the family Oocystaceae. The method of coenobium formation is suggestive of a taxonomic nižších a vyšších rastlín Slovenska [Checklist of affinity with the family Scenedesmaceae sensu non–vascular and vascular plants of Slovakia]. – Ko m á r e k & Fo t t (1983), particularly the subfamily pp. 12–100, Veda, Bratislava. Hi n d á k , F. & Hi n d á k o v á , A. (2010): First record of Crucigeniodeae and the genus Willea Sc h m i d l e . However, there are some arguments to let Ettliella Makinoella tasaensis Okada (Chlorophyceae, Oocystaceae) outside East Asia. – Fottea 10: tetraspora placed in the Oocystaceae. Members of 141–144. the other genera with similar propagation pattern Ko m á r e k , J. & An a g n o s t i d i s , K. (1998): as Ettliella like Makinoella and Tetrachlorella are Cyanoprokaryota 1. Teil Chroococcales. – already molecular–phylogenetic characterized In: Et t l , H.; Gä r t n e r , G.; He y n i g , G. & and confirmed members of the Oocystaceae Mo l l e n h a u e r , D. 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