Euglenophyceae, Schoenichen in Eyfurth & Schoenichen, 1925

Poniewozik, Małgorzata, Duangjan, Kritsana, Pekkoh, Jeeraporn & Wołowski, Konrad, 2020, Algae of bromeliad phytotelmata in the Queen Sirikit Botanical Garden, Chiang Mai, Thailand, Phytotaxa 432 (1), pp. 17-37 : 24

Euglenophyceae

The euglenoid diversity of bromeliad phytotelmata is interesting and includes both photosynthetic and non-photosynthetic representatives. The non-photosynthetic euglenoids are commonly found in phytotelm habitats due to the abundance of organic matter from which they can acquire energy ( Jones 2000). Carrias et al. (2014) recorded three non-photosynthetic euglenoid species from the genera Menoidium and Astasia in sun-exposed bromeliad tanks in French Guiana, while Ramos et al. (2017a) recorded seven euglenoid taxa in the genera Euglena and Phacus , apart from colourless species, from eastern Brazil. Other studies, however, recorded no euglenoids in phytotelm tanks of Saxony, Germany ( Gebühr et al. 2006) and southeastern Brazil ( Sophia et al. 2004). The present study recorded 31 taxa of euglenoids that included 18 non-photosynthetic taxa, mainly from the genera Astasia , Peranema and Petalomonas . Taking into account “hospitality” of the phytotelms, the most extreme conditions were noted for the microhabitat in Neoregelia “Fireball”, in which the highest water temperature, 29°C, was recorded. Additionally, the pH was low (5.45) and orthophosphate content reached 2.920 mg /L. Though the conditions were extreme compared to the other microhabitats studied, 13 taxa of non-photosynthetic euglenoids, represented mainly by Astasia spp. were noted there. Two of the euglenoid species are rarely recorded across the world - Astasia comma E.G.Pringsh. ( Fig. 3–2 ) and Gyropaigne ukrainica Assauł ( Fig. 3–5 ). Astasia comma is a rare species worldwide, but records from several localities are known (e.g., Kukharenko 2002; Schroeckh et al. 2003; Poniewozik 2014; Ramos et al. 2017a). Additionally, Astasia representatives are good research objects for molecular studies ( Leander et al. 2001; Müllner et al. 2001; Busse & Preisfield 2002, 2003). Gyropaigne ukrainica is a rare species and apart from the original description by Asauł (1966), it has been recorded only twice so far. It was collected in an acidic ditch with decaying vegetation in North Maharashtra, India ( Kumawat & Patil 2011), and in the western part of Ukraine within flood-land water bodies of Desna-Starahuta National Nature Park ( Burova & Zhezhera 2013). It is worth emphasizing that these species were recorded neither from natural habitats nor semi-natural in Thailand although several papers about euglenoid flora have been published so far ( Duangjan & Wołowski 2013, Duangjan et al. 2014, 2017).The other species of heterotrophic euglenoids were not common in worldwide habitats either. Sunlight availability seems to be the key regulating factor in the development of that group of protists in shaded or sun-exposed bromeliads. A higher incidence of photosynthetically active radiation promotes a rise in temperature and primary production in the water column, which results in an increase in oxygen concentration ( Guimaraes-Souza et al. 2006), hence it may increase development of euglenoids that prefer warm waters ( Heckman et al. 1996; Rahman et al. 2012; Poniewozik 2016; Poniewozik & Juráň 2018) and other thermophilic algae. Conversely, shadow sites promote growth of heterotrophic organisms, such as non-photosynthetic euglenoids. They are commonly found in water bodies with limited light availability and often also rich in organic matter, where they feed on bacteria and organic solutes and, similar to other mixotrophs (e.g. cryptomonads) ( Lenard 2015; Lenard & Ejankowski 2017), do not rely on sunlight for photosynthesis. Our data support those found in Brouard et al. (2012) that photosynthetic euglenoids prefer insolated bromeliads, while non-photosynthetic ones prefer shaded plants. In the study of Ramos et al. (2017a) a great species abundance was observed for pigmented euglenoids, especially for Euglena mutabilis , one of the species in the sun exposed bromeliads in the present study. Laessle (1961) observed very abundant growth of euglenoids ( Trachelomonas sp. and Euglena spirogyra Ehrenb. ) in Jamaican bromeliads exposed to strong sunlight. Apart from trachelomonads that were, in his opinion, a source of food for Chironomus species, he found some diatom and green algal species ( Laessle 1961). Our results, in conjunction with previous observations on occurrences of euglenoids in bromeliads, indicate shadowed sites are proper for colourless euglenoids, while sun-exposed plants create favorable conditions for especially pigmented euglenoids, although colourless specimens can also be found there. Advantageous occasion to settle tanks exposed to the sunlight by algae having chloroplasts may be explained by other studies, which provided results that bromeliads that develop directly under the sunlight receive a higher incidence of light radiation as well as rain and a smaller input of organic matter (e.g. leaves), contrary to the bromeliads that develop in the shadow of plants ( Scarano et al. 2002). Fenchel et al. (1998) noticed a higher intensity of heterotrophic metabolism in the water column in individuals from Neoregelia cruenta growing in shadow sites than in sun-exposed. They observed reduced oxygen concentrations and increased ammonium concentrations that indicated the prevalence of heterotrophic in relation to the autotrophic processes ( Fenchel et al. 1998). The highest organic matter input and the lowest solar radiation promoted more favorable conditions to a more heterotrophic metabolic balance in the studies on bromeliads in Brazil ( Guimaraes-Souza et al. 2006). Some authors reported that bromeliads exposed to the sunlight were settled by a greater number of taxa from different groups and they were characterized by greater richness than these ones growing in the shadow ( Brouard et al. 2011, Ramos et al. 2017a). Apart from light - shadow preferences, organic matter content is a very important factor for growth of euglenoids, regardless of whether green or colourless. In natural environments they are regularly found in organically rich, however typically small volume basins like temporary ponds, oxidation ponds of sewage treatment plants ( Padisák et al. 2003). Due to their preferences and tolerances of high BOD, euglenoids (with exception of Trachelomonas species) constitute W1 functional group - the unit that, due to condition demands, is typically occurring of small organic ponds being indicator organisms for that kind of water bodies ( Reynolds et al. 2002).

Figures

FIGURE 3. 1—Anisonema pusillum A.C.Stokes, 2—Astasia comma E.G.Pringsh., 3—Distigma steinii E.G.Pringsh., 4—Entosiphon sulcatus (Dujard.) F.Stein, 5—Gyropaigne ukrainica Asauł, 6—Peranema deflexum Skuja, 7—P. sacculus Christen, 8—Peranema sp., 9—Petalomonas angusta (G.A.Klebs) Lemmerm., 10—Rhabdomonas costata (Korshikov) E.G.Pringsh., 11—Rh. incurva Fresen., 12— Phacus hyalina Skvortsov. Scale bars = 10 µm.

FIGURE 4. 17—Euglena mutabilis F.Schmitz, 18—Euglenaria anabaena (Mainx) Karnkowska & E.W.Linton, 19-Phacus inflexus (Kisselev) Pochm., 20—Ph. longicauda (Ehrenb.) Dujard., 21—Ph. orbicularis fo. communis T.G.Popova, 22—Strombomonas scabra (Playfair) Tell & Conforti, 23—Trachelomonas oblonga Lemmerm., 24—T. pulcherrima Playfair. Scale bars = 10 µm.

FIGURE 5. 1—Ankistrodesmus fusiformis Corda, 2—Dictyosphaerium sphagnale Hindák, 3—Dictyosphaerium sp., 4—Kirchneriella lunaris (Kirchner) K.Möbius, 5—K. obtusa (Korshikov) Komárek, 6—Monoraphidium contortum (Thur.) Komárková-Legnerová, 7—M. griffithii (Berk.) Komárková-Legnerová, 8—M. tortile (West & G.S.West) Komárková-Legnerová. Scale bars = 10 µm.