New Record for Bangladesh : Two Species and Two Forms of Nitella Agardh

Nitella Ag. has been described (2002-2008) from different aquatic habitats. Two species and two forms are new for Bangladesh. These are: Nitella gracilis Agardh, N. batrachosperma (Thuill.) A. Braun, N. furcata var. furcata f. roxburghii (A. Br.) R.D.W. and N. acuminata A. Br. ex Wallm. var. acuminata f. capitulifera (T.F.A.) Wood.


Introduction
Ecorticate charophyte Nitella Ag. is a cosmopolitan genus of family Characeae.The number of species recognized in 1951 (Wood, 1952) was 153 and approximately 180 were listed by Wood & Imahori (1959).Wood & Imahori (1965) restricted the number to 49 only as there were fewer distinct species.Infraspecific variation of Nitella Ag. is great and mostly earlier species assigned to variety and form level (Wood & Imahori 1965).Pal et al. (1962) reported 34 species of Nitella Ag. from India, Burma, Srilanka (Ceylon), Bangladesh (East Pakistan) and Pakistan.Zaneveld (1940) reported 12 species from Malaysia and adjacent countries.In Bangladesh, Nitella Ag. had been systematically described by different researchers (Agharkar & Kundu, 1937;Kundu, 1938;Kundu, 1959;Islam & Sarma, 1976;Zaman, 2001;Naz et al., 2009) from lotic and lentic water habitats.In present communication all taxa have been documented with photo micrographic illustration and a comparative study between different researchers has also been included.

Materials and Methods
Specimens were collected from Chapai-Nawabgonj, Rajshahi and Thakurgaon district.Collected specimens were preserved in Transeau's solution (Transeau, 1916, pp.121-133) and dried as herbarium specimens for morphological observations.All specimens have been kept as herbarium in Phycology and Limnology laboratory, Rajshahi University, Rajshahi, Bangladesh and Nitella gracilis has been kept in Rostock University, Rostock, Germany.Liquid preservative is much more convenient for Charophyta, the specimens are less damaged and easier to identify.Photomicrographs of more important parts of a particular species, especially dactyls, sex organs, oospore etc. was taken with the help of Vivitar V3200 camera under a Reichert (Nr.309209) microscope.During present study 8% KOH was used to the observation the ornamentation pattern of oospore wall.
Habitat: Rice field, 5 cm depth of freshwater.

Risk of confusion:
Sterile plants of N. gracilis can be distinguished from N. wahlbergiana and N. mucronata by a more slender appearance.In contrast to N. wahlbergiana, fertile heads of N. gracilis are not condensed.N. mucronata is more robust and has a reticulate oospore membrane.Small specimens can be confused with N. confervacea (Schubert & Blindow, 2003).
Reference to Bangladesh: Not known.
Distribution: Europe: England, Ireland, Denmark, Rumania, Norway, Sweden, Finland, France, Belgium, Germany, Switzerland, Austria, Hungary, Italy, and Russia; Asia (Note 1): India, China; Africa and New Caledonia, Poland, Latvia, Czech Republic: Eight locations in Bohmen, Balkan, Estonia, and Lithuania.It is also found in freshwater in all countries bordering the Baltic Sea.
N. batrachosperma can be confused with N. hyalina, N. wahlbergiana and N. gracilis.From N. hyalina it can be distinguished by the uniform length of the branchlets.N. wahlbergiana, which also can be very small, is less slender, and most gametangia are situated on the second furcation of the branchlets (Only some on the first).N. gracilis is sparser and does not compact heads.Its dactyls are often 3-celled (Schubert & Blindow, 2003).
Reference to Bangladesh: Not known.
Distribution: Asia: India, Burma, Japan, Kazakhstan, Pakistan; Europe: France, South and Central Finland, Spain, South Norway, Italy, South Sweden, North Sweden, Denmark, Germany, Ireland, Scotland, Portugal, Belgium, Latvia and Poland; USA, Africa: Morocco; Australia, New Zealand, but not in South America.
Habitat: Canal of rice field, 2 cm depth of freshwater.
Comment: It is easily distinguished from other forms of N. acuminata by presence of reddish brown oospores with smooth membrane (Wood & Imahori, 1965).Similar observation was observed in present investigation.
Reference to Bangladesh: Not known.
Distribution: Asia: Japan; Taiwan.Note 2. Gametangial measurements are given in Table 1, 2, 3 & 4 and diversified characteristics (such as: size of nucule, corona, oospore and globule etc.) have been observed by comparative findings to different reports for N. gracilis Agardh, N. batrachosperma (Thuill.) A. Braun, Nitella furcata var.furcata f. roxburghii (A.Br.) R.D.W. and N. acuminata A. Br.ex Wallm.var.acuminata f. capitulifera (T.F.A.) Wood.In present study provides a full range of measurements (Table 3).Mann & Raju (2002) reported that there is some indication that ecological factors are capable of modifying gametangial size, the extent to which this is possible is not known for the different charophyte species.The moderate differences seen in Table 3 may be considered to fall in the normal genetic variation range of this charophyte.Zaneveld (1940) and Pal et al. (1962) only considered the measurement of oospore.But Wood & Imahori (1965) also included the measurement of globule too.