pp. 1-12

Shah Md. Golam Gousul Azam*, Umma Nahar, Nasrin Jahan Diba, Md Moniruzzaman, Sabrina Naz

Phycology and Limnology Laboratory, Department of Botany, University of Rajshahi, Rajshahi-6205, Bangladesh

* Corresponding author E-mail: gousulazam83@gmail.com

ABSTRACT

In the present study, microalgae as epiphytes on charophyta are recorded from different aquatic habitats for the first time in Bangladesh. These are Bulbochaete debaryana Wittr. & Lund. in Wittr., B. nana Wittr. var. chungkingensis Jao, B. iyengarii Sarma & Mukherjee, Oedogonium gracillimum Wittr. & Lund. Hirn f. gracillimum Tiffany, O. pygmaeum Gonz. & Jain, O. regium Hughes, O. obtruncatum Wittr. var. obtruncatum, O. gunnii Wittr. Hirn. var. breviarticulatum Jao, O. oblongellum Kirch ex Hirn.var. oblongellum Gem., O. thanense Gonz. & Jain, Microspora amoena (Kutz.) Rabenhorst, Characium ornithocephalum A. Braun, Gongrosira prostrata Jao, G. debaryana Rabenhorst, Uronema confervicola Lagerheim, Pediastrum tetras (Ehrenberg) Ralfs , Spirogyra amphimorpha Islam, Zygnema conspicuum (Hassal) Transeau, Cladophora criapata (Roth) Kützing, Rhizoclonium crassipellitum West & West, Chlorhormidium dissectum (Gay) Farooqui, Oscillatoria sancta Kutzing ex Gomont, O. geminata Menegh, Spirulina nordstedtii Turpin ex Gomont, Microchaete robusta Setchell & Gardner, Lyngbya aerugineo-coerulea (Kutz.) ex Gomont, Navicula cryptocephala Kütz., Fragilaria vaucheriae Lyngbye , Synedra ulna (Nitzsch) Ehr. We observed that each taxon had specific host preference.

Key words: Epiphytic algae, host specificity, charophyte, Bangladesh

INTRODUCTION

A large debate has focused on the nature of the intimate relationship between the epiphytic algae and its host-plant. Many authors tend to consider macrophytes as neutral substrate (Carignan and Kalff, 1982, Cattaneo and Kalff, 1980, Fontaine Iii and Nigh, 1983, Harlin, 1973, Millie and Lowe, 1983, Morin, 1986). Epiphyte plays an important role in the primary production of aquatic habitats even in case they are growing in deep. Its share forms about one- third of total primary productions (Laugaste and Reunanen, 2005).

            Charophyte is one of the most common hosts of epiphyte algae. Generally, the epiphytic algae grow upon top of filaments and internodes, sometimes they live associated with node. Epiphytic algae are found in the base cell too (Gonzalves, 1981, Mrozinska, 1985, Naz et al., 2007). Earlier, significant number of Oedogonium and Bulbocheate spp. have been reported from Bangladesh (Alam et al., 2014, Azam et al., 2016, Naz and Azam, 2008, Naz et al., 2008, Naz et al., 2009a, Naz et al., 2009b, Naz et al., 2014, Naz et al., 2007). In the present communication, the distributions and host specificity of epiphytic algal flora on charophytes have been described.

MATERIALS AND METHODS

            Charophytes were collected from September 2006 to February 2007 from different locations at Rajshahi and one location of Thakurgaon districts from shallow and deep water zone (0.5 to 12 M) by hand or by mean of iron-wire hooks tied with a long nylon rope. Collected materials were permanently preserved for the microscopic study in Transeau’s solution (Transeau, 1916). The plants were observed under a compound microscope. Excluding the basal part, each host plant was randomly cut with a blade into 10 pieces (1 cm each) with attached epiphytic algae for identification. Identification was made with the help of relevant literature following (Ahmed et al., 2007, Ahmed et al., 2009, Azam et al., 2016, Desikachary, 1959, Groves and Bullock –Webster, 1920, Groves and Bullock–Webster, 1924, Islam and Sarma, 1968, Islam and Sarma, 1976, Mrozinska, 1985, Naz et al., 2011, Pal et al., 1962, Schubert    and    Blindow,    2004, Vashista, 1976, Wood and Imahori, 1965).

RESULTS

We found 29 taxa of epiphytic algae association with belonging to different groups. Among them 21 taxa belonged to Chlorophyta, 5 to Cyanophyta, 3 to Bacillariophyta. Here, the short description of the epiphytic algae is described with their habitat.

1. Bulbochaete debaryana & Lund. in Wittr. (Gonzalves, 1981, Saito and Yamagishi, 1973)

Plant monoecious, macrandrous. Vegetative cells 20-28 μm long, 14-19 μm in diameter. Oogonium ellipsoid, situated below a vegetative cell or terminal setae. Oogonia 46-51 μm long, 22-33 μm in diameter. Oospores 37-43 μm long, 23-25 μm in diameter. Antheridium single or up to 3, 10-113 μm  long, 4-7 μm in diameter.

Habitat, date of collection and location: Low land, host plant: Nitella hyaline; Collection number N 5, September 2, 2006, Andharshura beel, Tanore, Rajshahi, Bangladesh.

2. Bulbochaete nana Wittr. var. chungkingensis Jao (Gonzalves, 1981)
Plant macrandrous, homothallic. Vegetative cells 19-25 μm long, 12-15 μm in diameter. Oogonium somewhat obovoid-ellipsoid, rarely ellipsoid, broader than that of the type, 27-32 μm. Antheridium smaller than that of the type, 8-10 μm long, 4-6 μm in diameter. Outer layer of spore wall smooth; median layer longitudinally costae.
Habitat, date of collection and location: Low land, host plant: Chara braunii; Collection number B 067, January 15, 2007, Andharshura beel, Tanore, Rajshahi, Bangladesh.

3. Bulbochaete iyengarii Sarma & Mukherjee (Sarma and Mukherjee, 1990)
Plant macrandrous, heterothallic. Vegetative cells moniliform to short cylindric, 14.0-17.5 μm long, 13.2-14.0 μm in diameter. Basal cell pointed at the base, basal cell blunt. Oogonium ellipsoid, brown, erect, 33 μm long, 22 μm in diameter. Oospore of same shape as oogonium. Usually completely filling the oogonium, oospore 19.8 μm in diameter, 28.0 μm long. Spore wall three-layered, outer layer smooth, median layer areolate. Antheridium erect, 1-2 seriate, 33.5 μm long, 9.3 μm in diameter, division horizontal.
Habitat, date of collection and location: Low land, host plant: Chara braunii; Collection number Bulbo-004, 18 November 2006, Andharshura beel, Tanore, Rajshahi, Bangladesh.

4. Oedogonium gracillimum Wittr. & Lund. Hirn f. gracillimum Tiffany (Gauthier- Lievre, 1963-64, Gonzalves, 1981)
Plant macrandrous, homothallic. Vegetative cell cylindric, 21.3-32.7 μm long, 4.5-7.2 μm in diameter. Basal cell elongate 13.5 μm long, 3.5 μm in diameter. Terminal cell obtuse. Oogonium single ellipsoid, after every 3-5 vegetative cells, 27.6 μm long, 10.7-13.95μ diameter, Oospore ellipsoid 19-23.5 μm long, 10-13.5 μ in diameter and, operculate, division superior spore wall smooth, antheridia single.
Habitat, date of collection and location: Rice field, host plant: Chara zeylanica; Collection number C 12, January 10, 2007, Sarkarpara, Thakurgaon, Bangladesh, Low land, host plant: Chara braunii; Collection number Bulbo-004, 18 November 2006, Andharshura beel, Tanore, Rajshahi, Bangladesh.

5. Oedogonium pygmaeum Gonz. & Jain (Gonzalves, 1981)
Plant macrandrous, homothallic, usually 3 to 5 celled. Vegetative cells slightly capitellate, 16-19 μm long, 4-6.1 μm in diameter. Basal cell depressed hemispheric, 10-11.5 μm in diameter, 9 μm long. Oogonium single, globose to subpyriform-globose, 17-21μ long, 14 μ in diameter, operculate, division superior. Oospore globose filling the oogonium, 13.9 μm in diameter and 19 μm long. Gonzalves (1981) described this species incompletely without mentioning the description of the male portion but during present study it appeared to be homothallic and macrandrous. Other description of this species fits well with the description of Oedogonium pygmaeum.
Habitat, date of collection and location: River, host plant: Nitella furcata; Collection number N 13, November 11, 2006, the Padma River (Dashmaria Ghat) Rajshahi, Bangladesh.

6. Oedogonium regium Hughes (Gonzalves, 1981)
Plant nannandrous, idioandrosporous; vegetative cell capitellate, 27-36 μm long, 4-6.5 μm in diameter. Oogonia depressed globose, 21μm in diameter, 22 μm long. Operculate, division supramedian often opening like a beak like manner. Oospore globose not filling the oogonium, 18 μm long, 17 μm in diameter. Spore wall smooth. Androsporangia present. Dwarf male unicellular, situated on the oogonia. 8.5- 9.3 μm long, 6 μm in diameter.
Habitat, date of collection and location: Rice field, host plant: Chara vulgaris; Collection number C 7, February 2, 2007, Kharail Beel, Trimohini, Mohanpur, Rajshahi, Bangladesh.

7. Oedogonium obtruncatum Wittr. var. obtruncatum (Gauthier- Lievre, 1963-64, Gonzalves, 1981)
Plant nannandrous, gynandrosporous. Gonzalves reported this taxa as also as idioandrosporous but during the present study this stage was not observed. Vegetative cell evidently capitellate, 49.5-54.8 μm long, 16.5-23 μm in diameter. Basal cell elongate, terminal cell apically obtuse. Oogonia single or 2-4 series, ellipsoid, 57.1-61.4 μm long, 44.9-47.2 μm in diameter, operculate, division supreme, operculum small. Oospore identical in shape to the oogonium and nearly filling it, 55.8μ long, 40.6-41.7 μm in diameter. Oospore wall smooth. According to Gonzalves, gynandrosporous habit, capitellate vegetative cells, supreme operculum and unicellular dwarf males are characteristics of this taxa which is similar to the present specimen.
Habitat, date of collection and location: River, host plant: Chara braunii; Collection number C 004, December 17, 2006, the Boral river (The East side of Charghat Bridge), Rajshahi, Bangladesh.

8. Oedogonium gunnii Wittr. Hirn. var. breviarticulatum Jao (Gauthier- Lievre, 1963-64, Gonzalves, 1981)
Plant macrandrous, homothallic. Vegetative cell cylindric, 17-32 μm long, 7.5-11 μm in diameter. Basal cell hemispheric, 13.2 μm long, 9 μm in diameter. Oogonium single, depressed globose, 27.4 μm long, 19 μm in diameter, division narrow, but distinct. Oospore in shape to the oogonium, incomplete filling, 25 μm long, 16.9 μm in diameter.

Antheridium single, hypogynous, 7μm long, 6.3 μm in diameter, spermatozoid single.
Habitat, date of collection and location: River, host plant: Lychnothamnus barbatus; Collection number L 100, November 17, 2006, The Boral river (The East side of Charghat bridge), Rajshahi, Bangladesh.

9. Oedogonium oblongellum Kirch ex Hirn.var. oblongellum Gem. (Gauthier- Lievre, 1963-64, Gonzalves, 1981)
Plant macrandrous, homothallic. Vegetative cells cylindric, 14-27 μm long, 6.8-7.9 μm in diameter. Terminal cell obtuse. Oogonium single obovoid-ellipsoid, 30 μm long, 22 μm in diameter, division superior. Oospore, ellipsoid, nearly filling the oogonium, 26 μm long, 18.9 μm in diameter. Spore wall smooth. Antheridia three, hypogynous, 6.8 μm long, 3.3 μm in diameter; division horizontal.
Habitat, date of collection and location: Rice field, host plant: Chara vulgaris; Collection number C 7, February 2, 2007, Kharail Beel, Trimohini, Mohanpur, Rajshahi, Bangladesh.
10. Oedogonium thanense Gonz. & Jain (Gonzalves, 1981)
Plant macrandrous, heterothallic. Vegetative cell slightly capitellate, 72.6-82.2 μm long, 14.2-17.5 μm in diameter. Basal cell elongate, 51.5 μm long, 18.8 μm in diameter. Terminal cell setiferous, up to 195 μm long, oogonia terminal, single, ovoid to ovoid ellipsoid, 40.9 μm in diameter and 51.5 μm long, operculate division superme; Wall of oogonium thick, Oospore identical in shape to the oogonium which it fills, 34.3 μm in diameter and 40.6 μm long; spore wall smooth.
Habitat, date of collection and location: Rice field, host plant: Chara zeylanica; Collection number C 12, January 10, 2007, Sarkarpara, Thakurgaon, Bangladesh.

11. Microspora amoena (Kutz.) Rabenhorst (Ahmed et al., 2007, Islam and Khatun, 1966)
Cells cylindrical, slightly constricted at cross walls, 35-60 μm long, 15-30 μm broad at septum. Cell wall moderately thick, about 3-5 μm in thickness. Chloroplast covering entire portion of cell wall. H-pieces clearly evident.
Habitat, date of collection and location: Rice field. Host plant: Chara braunii; Collection number K 4, October 17, 2006. Kharail Beel, Trimohini, Mohanpur, Rajshahi. The Boral River. The East side of the Charghat bridge, Charghat, Rajshahi Host plant: Chara braunii; Collection number B 17, November 17, 2006. Dashmaria Ghat. The Padma River, Rajshahi, Bangladesh. Host plant: Chara zeylanica Collection number N 5, November 11, 2006.
12. Characium ornithocephalum A. Braun (Ahmed et al., 2007)
Cells narrowly elongate ovoid to fusiform, erect with a short oblique tip, stipe short. Cells 7-18 μm broad, 20-45 μm long. Chloroplast laminate, parietal with a prominent pyrenoid.
Habitat, date of collection and location: Rice field. Sarkarpara, Thakurgaon, Bangladesh. Host plant: Chara braunii; Collection number S 4, January 10, 2007.

13. Gongrosira prostrata Jao (Ahmed et al., 2007)
Thallus irregularly branched, encrusted on substratum. Prostrate system prominent, irregular branches forming disc-like structure. Cells brown in color, cylindrical, barrel-shaped, angular, 10-21 μm broad, 11-30 μm long. Large cells 25 μm broad, 31 μm long at the centre of thallus, cell wall thick, hard, warted. Chloroplast single, parietal, with 1-3 pyrenoids.
Habitat, date of collection and location: Low land (Rice field). Host plant: Nitella hyaline; Collection number N 5, September 2, 2006. Andharshura beel, Tanore, Rajshahi, Bangladesh.

14. Gongrosira debaryana Rabenhorst (Ahmed et al., 2007)
Thallus deep green, cushion-like. Prostrate part not found, erect part with short branched filaments. Branching lateral, cells cylindrical, barrel-shaped or angular. Basal cells mostly short and narrow, 11-40 μm broad, 8.9-37.5 μm long. Apical cells elongated and wide, 14-54.5 μm broad, 17-60.5 μm long, often spherical, 20-50 μm in diameter. Cell wall thick, up to 3 μm in diameter. Chloroplast massive with several pyrenoids.
Habitat, date of collection and location: Low land (Rice field). Host plant: Nitella hyaline; Collection number N 5, September 2, 2006. Andharshura beel, Tanore, Rajshahi, Bangladesh.
15. Uronema confervicola Lagerheim (Ahmed et al., 2007)
Filaments long, straight or curved, attached by elongated disc shaped basal cell. Cells 8.3-41.9 μm long, 4.5-8.3 μm broad. Terminal cells pointed or less pointed measuring upto 23 μm. Chloroplast parietal with 1-2 pyrenoids.
Habitat, date of collection and location: The Boral River. The East side of the Charghat bridge, Charghat,Rajshahi, Bangladesh. Host plant: Chara vulgaris; Collection number C 7, November 11, 2006.

16. Pediastrum tetras (Ehrenberg) Ralfs (Ahmed et al., 2007)
Colony entire, 4-8 celled. Inner cells with 4-6 straight sides but with one margin deeply incised. Peripheral cells crenate with a deep incision in outer face, their lateral margins adjoined along of their length. Cells 4.3-6.9 μm wide, 5.7-9.2 μm long.
Habitat, date of collection and location: River; Host plant: Chara braunii; Collection number B 17, November 11, 2006, the Boral River (East side of the Charghat bridge, Charghat, Rajshahi, Bangladesh).
17. Spirogyra amphimorpha Islam (Ahmed et al., 2007, Vashista, 1976)
Plants having two kind of filaments, male filaments with vegetative cells 110.9-207.6 μm long and 71.2-75.6 μm broad. Female filaments with vegetative cells 128-167 μm long, 123-135 μm broad, with plane end walls. Chloroplasts 3-4, conjugation scallariform, tubes formed by both gametangia. Receptive gametangia shorter, wider, slightly inflated towards conjugating canal. Zygospore ellipsoid, 135 μm long, 84-95 μm broad, filling gametangial cell vertically, light yellow color, zygospore wall smooth.
Habitat, date of collection and location: Rice field, host plant: Chara braunii; Collection number K 4, December 17, 2006, Kharail Beel, Trimohini, Mohanpur, Rajshahi, Bangladesh; Rice field, host plant: Chara zeylanica and Nitella hyalina. Collection number C1 & N10, December 17, 2006. Kharail beel, Trimohini, Mohanpur, Rajshahi, Bangladesh.

18. Zygnema conspicuum (Hassal) Transeau (Ahmed et al., 2007, Islam and Khatun, 1966)
Filaments yellowish-green. Vegetative cells 62-96 μm long, 21-278 μm broad, cylindrical, slightly constricted at septum, slightly swollen at middle of cell. Conjugation scalariform. Zygospore mostly in canal, rarely towards one gametangium, zygospore globose or depressed-globose, 14-17 μm long, 24.2-31.9 μm broad, wall scrobiculate, light brown.
Habitat, date of collection and location: Rice field. Sarkarpara, Thakurgaon, Bangladesh, Host plant: Chara zeylanica; Collection number C12, January 10, 2007.

19. Cladophora criapata (Roth) Kützing (Ahmed et al., 2007, Islam and Alam, 1980, Islam and Hossain, 1978, Prescott and Vinyard, 1965)
Thallus attached, filamentous, branched. Branching mainly unilateral or opposite, long tapering. Cells cylindrical, wall smooth, thin. Cells of main axis 27-60μm broad,156-670 μm long. Primary branch cells 20-43 μm broad, 215-780 μm long. Rhizoids 15-23 μm in diameter.
Habitat, date of collection and location: The Boral River. The East side of the Charghat bridge, Charghat Rajshahi, Bangladesh, Host plant: Lychnothamnus barbatus; Collection number C 100, November 17, 2006.
20. Rhizoclonium crassipellitum West & West (Ahmed et al., 2007, Islam and Alam, 1980, Prescott and Vinyard, 1965)
Thallus free floating or terrestrial on moist sandy soil. In terrestrial forms unicellular rhizoids frequently develop. Cells cylindrical, regular wall thick, lamellate, filament 23-38 μm broad, 44-151 μm long. Cell wall 4-7.5 μm thick.

Habitat, date of collection and location: River, host plant: Lychnothamnus barbatus; Collection number C 100, November 11, 2006, The Boral River (East side of the Charghat bridge, Charghat,Rajshahi, Bangladesh).
21. Chlorhormidium dissectum (Gay) Farooqui (Ahmed et al., 2007)
Filaments mostly long, but fragmented into short length, redily break up into single cells. Cells cylindrical to barrel-shaped, thin-walled, 7.5-13.0 μm long, 6.3-8.5 μm broad. Chloroplast single covering half of cell with a pyrinoid.
Habitat, date of collection and location: The Boral River. The East side of the Charghat bridge, Charghat, Rajshahi. Host plant: Lychnothamnus barbatus; Collection number C 100, November 11, 2006.

22. Oscillatoria sancta Kutzing ex Gomont (Desikachary, 1959, Islam and Hossain, 1978, Islam and Uddin, 1978a)
Thallus composed of many trichomes, aggregated, dark-blue to dark-grey mass, thin. Each trichome may be straight or slightly curved, distinctly constricted at the cross walls. Trichome end briefly attenuated. Cells 8.2-15.0 um broad and 2.5-5.9 um long, granulate at the cross walls. End cell flattened, hemispherical, slightly capitates.
Habitat, date of collection and location: Dashmaria Ghat. The Padma River, Rajshahi, Bangladesh; Host plant: Chara zeylanica; Collection number N 5, November 11, 2006.
23. Oscillatoria geminata Menegh (Islam and Hossain, 1978)
Thallus delicate, pale blue-green. Trichome straight, cross walls constricted. Cells longer than the breadth, 3-4.5 μm broad, 10-14 μm long. End cell pointed.
Habitat, date of collection and location: Dashmaria Ghat. The Padma River, Rajshahi, Bangladesh; Host plant: Chara zeylanica; Collection number N 5, November 11, 2006.
24. Spirulina nordstedtii Turpin ex Gomont (Desikachary, 1959)
Trichome very long (165 m), upto 2 m in diameter, regularly spirally coiled, blue-green, spirals 2.5-4.29 m distant.
Habitat, date of collection and location: Low land (Rice field). Host plant: Chara braunii; Collection number A 2, September 2, 2006. Andharshura beel, Tanore, Rajshahi, Bangladesh.
25. Microchaete robusta Setchell and Gardner (Desikachary, 1959)
Filaments solitary or several (5-10 together), radiating from a common centre with a gregarious growth, straight or slightly curved, uniformly broad, up to 261 μm long, 13.7-16.9 μm broad, constricted at the cross walls. Cells usually subquadrate, spheroidal, 7.5-11.0 μm long and 4.6-8.9 μm wide. Cell contents granular at the cross walls. Heterocysts single, basal or intercalary, rectangular, rarely subquadrate, 11.0 μm wide, 8.9-14.3 μm long.
Habitat, date of collection and location: The Boral River. The East side of the Charghat bridge, Charghat,Rajshahi, Bangladesh; Host plant: Lychnothamnus barbatus; Collection number C 100, November 11, 2006. Rice field. Sarkarpara, Thakurgaon, Bangladesh. Host plant: Chara zeylanica. Collection number C12, January 10, 2007.
26. Lyngbya aerugineo-coerulea (Kutz.) ex Gomont (Naz and Zaman, 2000)
Filamentous, solitary or sometimes forming light green expanded thallus, flexuous, fragile, mucilage sheath thin, firm, not lamellated or coloured violet. Cells 5-11 μm broad and 2-3.3 μm long. Trichome not constricted at the cross walls, sometimes granulated, trichome apex occasionally capitates.
Habitat, date of collection and location: Dashmaria Ghat. The Padma River, Rajshahi, Bangladesh; Host plant: Chara zeylanica, Collection number N 5, November 11, 2006.
27. Navicula cryptocephala Kütz (Ahmed et al., 2009, Germain, 1981)
Frustules 34.65 m long and 10.725 m broad at the middle.
Habitat, date of collection and location: Rice field, host plant: Chara zeylanica; Collection number C 12, January 10, 2007. Sarkarpara, Thakurgaon; and host plant: Chara braunii, Collection number S 4. Sarkarpara, Thakurgaon, Bangladesh.
28. Fragilaria vaucheriae Lyngbye (Ahmed et al., 2009)
Each frustule 105.6 m long and 6 colony of frustules are 84 m broad.
Habitat, date of collection and location: Rice field; host plant: Chara zeylanica. Collection number C12, January 10, 2007, Sarkarpara, Thakurgaon; Rice field; host plant: Chara braunii; Collection number C 9, November 11, 2006, the Padma River (Dashmaria Ghat), Rajshahi, Bangladesh.
29. Synedra ulna (Nitzsch) Ehr. (Ahmed et al., 2009, Islam and Chowdhury, 1979, Islam and Haroon, 1975)
Frustules 118.8 m long and 9.9 m broad at the middle; at the tip 2.97 m in broad.
Habitat, date of collection and location: Rice field, Host plant: Chara zeylanica; Collection number C 12, January 10, 2007, Baliadangi, Sarkarpara, Thakurgaon, Bangladesh.
Discussion
The species number of epiphytic algae on the three genus of charophytes were different from each other. The epiphytic algae on Chara vulgaris represented in 3 taxa, 12 taxa on Chara zeylanica, 9 taxa on Chara braunii, Nitella hyalina in 4 taxa and 5 taxa on Lychnothamnus barbatus and only one taxon on Nitella furcata respectively (Table1). The predominant species of epiphytic algae on the three genera of charophytes belongs to Oedogonium sp. and Bulbochaete sp. Although diatoms were represented by only five taxa as epiphytes on charophytes, they always exhibited much higher abundance than the rest of the reported algal taxa. Among the five, Fragilaria sp. appeared to be the dominant. Similar findings were also supported by (van Dam and Mertens, 1993). They commented the species number was different because the habitat structure had pervasive effects on community composition and diversity while working on the occurrence of epiphytic algae on three streams in Northern China. They further added the epiphytic algae on Chara vulgaris resulted in 49 species, 37 species on Cladophora fracta and only 6 species on Batrachospermum arcuatum, respectively and in terms of the seasonality, there was an obvious seasonal trend in species number of epiphytic algae: spring > autumn > summer > winter (Hu et al., 2012). These results were quite similar with the present study. Charophytes plays an important role in increasing water transparency (Nõges et al., 2003). In the present communication, we also found charophytes are grown well in more transparent water and on that charophyte a good number of epiphytic algae were grown. There could have been a distinct positive relation with the water transparency and epiphytic algae. This point demands further detailed investigation. During present communication, the results indicate that there were some environmental factors influenced the epiphytic algae in different extents. The key factors were pH and depth (data not shown). In macrophyte species Chara vulgaris L. and Cladophora glomerata Kiitz.) and one angiosperm Potamogetón densus L., considerable heterogeneity was observed in density of the epiphytic populations between the plant species studied as regards, the composition of these algal populations showed a conspicuous degree of homogeneity within each macrophytic species. The epiphytic algae occupy specific microhabitat niches on their host plants according to a non stochastic pattern of distribution (Comte and Cazaubon, 2002). In the present investigation, we can also confirm that algal taxa growing epiphytically on the charophytes had distinct host specificity (Table 1).

Conclusions
This is the first study to evaluate the epiphytic algal host specificity on charophytes in Bangladesh so that its contribution to the host specificity of different epiphytic algae may be established. As there is no other documentation in the host specificity, therefore, no such comparison could be done; rather this work can be mentioned as a pioneer study for future. In term of biodiversity conservation, apart this information derived from this documentation could be helpful because of their host specificity; as these microalgae lives on specific host.
As in Bangladesh habitat loss and habitat destruction are one of the major causes of aquatic biodiversity loss, information gathered in this present documentation can be used for the biodiversity conservation of the concerned epiphytic algal taxa. To know the details host specificity of epiphytic algae, a good number of studies should be carried out on aquatic plants. However, it could be helpful for conserving the primary producer by giving special concentration on the certain group of algae. Much more attention is needed at molecular level to confirm the host specificity.

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