Gyrosigma

Habitat and distribution:

 

Gyrosigma is a widespread freshwater alga in Kanglung. Its habitat includes small pond, ditches, stagnant waters and drain waters. It rarely occurs in the fast flowing streams.
— Damchoe Gyeltshen and Namgay Rinchen, B.Sc. Life Sciences 2017

General  characteristics:
1. Pennate diatoms [1].
2. Cells sigmoid in outline, broad in the central region and narrow towards the apices [1].
3. Two plates like chloroplasts on either side of the longitudinal axis or are present lying either side of the gridle [2, 1].
4. The poles are rounded [1].
5. The striate on the valve surface are both parallel to the raphe and also transverse [1].
6. Reproduce vegetatively by cell-division and sexually by auxospores [2].
7. Radially symmetrical [2].

Key characteristics:

1. Raphe and axial area are uncommonly curved in Gyrosigma [2].
2. The raphe is S-shaped [1].

3. They exhibit characteristic gliding movement, caused by streaming cytoplasm by circulation within the raphe, and by the extrusion of mucilage[3].

Gyrosigma showing clear S-shaped raphe, rounded poles and scattered pyrenoids . . .

Freshwater fossil diatoms are present in the waters indicating high alkalinity [4]. It belongs to pennate type of diatom under Naviculaceae family.

 

Video:Video link

References:

[1] Edward G Bellinger and David C Sigee. Freshwater algae: identification and use as bioindicators. John Wiley & Sons, 2015.
[2] FE Fritsch. reprinted 1948. The structure and reproduction of the algae, 1, 1935.
[3] Gerald Webber Prescott. The algae: a review. Nelson, 1969.
[4] OP Sharma. Algae. series on diversity of microbes and cryptogams, 2011.
[5] Felix Eugene Fritsch. The structure and reproduction of the algae. At The University Press; Cambridge, 1948.

 

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