The Journal of Indian Botany/Volume 1/May 1920/Observations on the Volvocaceae of Madras

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OBSERVATIONS ON THE VOLVOCACEAE OF MADRAS*

BY

M. O. Parthasarathy Ayyangar, M.A.,

Acting Professor of Botany, Presidency College, Madras.

Though there have -been some very valuable contributions by algologists like Fritsch (3 and 4), West (6) and (7), Wallich (5), Zeller (10), and others, on the Fresh-water Algal Flora of the Indian region, there has been practically, with the exception of some stray notes, (l, 2, and 8 page 178), no account whatever, either syste- matic or ecological of the Volvocaceae of India.

Fritsch (3) in his systematic account of the Algal Flora of the Tropics does not refer to the Volvocaceae at all, though records of their occurrence have not been wanting, one of them, (Fleodorina), having been recorded by himself (2) from Ceylon. Again West G. S. 9) has recorded some new African species of Volvox. He says (8, (page 182), " Volvo x africanus is known to occur only from the plankton of Albert Nyanza." He has also recorded Pleodorina illinoisemis from Madras (8, page 178). He, however, expresses the opinion that the members of this family are on the whole cold water types (8, page 429). It would therefore appear that the mem- bers of the Volvocaceae are regarded by European algologists as preeminently cold water types. The primary object of this paper is to draw attention to the very common and abundant occurrence of this family in Madras, a typically semi-dry tropical place. In fact as may be seen below they attain their maximum development only during the warmer parts of the year.

Climatic Details

Madras is quite different from the other parts of India as regards its supply of rain. While all -the other parts of India get their maximum supply of rain during the months June to September from the S. W. or Summer Monsoon, the Madras coast districts (from Ganjam to Negapatam) get their chief rain supply during the months October to December from the N. E. or Winter Monsoon. The S. W. Monsoon is only of minor importance on the Madras coast and moreover does not directly bring any rain to Madras. During the breaks in this monsoon on the west coast and towards

• A paper read before the Botanical Section of the Indian Science Con-

gress Meeting at Nagpur, 1920. the end of ifc, when its force gets more and more spent, we in Madras get small showers (local showers) at very frequent intervals.

The effect of these small intermittent summer showers is, falling as they do on a parched up soil, merely to wet the surface soil and to fill up the various small depressions in the ground, causing numerous rain water pools all over the place. During these Summer Monsoon months the water in these pools is constantly changing its level. Thus after a fairly good rain the depressions are filled up. During the succeeding rainless days, the level of the water goes down slowly, and in the shallower depressions the water dries up completely. In the deeper pools, however, where the water does not get com- pletely dried up, a fresh rain sends the level up once more. And this process is repeated again and again.

During the N. E. or Winter Monsoon, the rains are heavy and generally continuous. And all the big tanks, streams, ponds, pools, and all low-lying tracts of land get filled up and often overflow. The numerous small rain-water pools that are merely filled up during the Summer Monsoon Season are during this season completely flooded and practically washed out.

The temperature during the S. W. Monsoon months though slightly lower than in May is still fairly high and the sky is generally cloudy and the weather very sultry, the month of September being the most sultry and trying part of the whole year. But with the advent of the N. E. or the Winter Monsoon, the temperature soon goes down and the weather, though the sky is often cloudy, is quite cool and pleasant.

The following table gives the details of the temperature, rain- fall and cloud values of the different months of 1919 at Madras : —

Occurrence of the Volvocaceae

The members of this group occur in different kinds of situation ; rain-water pools, permanent pools, ponds, ditches, water tubs, paddy- fields, streams, and tanks. They occur throughout the year but attain their greatest development and occur as dominant forms only during the summer monsoon season in the many small rain-water pools that are then formed. During the colder season, though they occur in various situations, they never reach the abundance noticeable in the rain-water pools formed during the summer season, but occur only as subordinate forms, though occasionally Volvox or Pleodorina, may occur for very brief periods as dominant forms in certain waters. I shall now take up the summer monsoon rain-water pools as being the more interesting of the two.

Summer rain-water pools

After the first few summer showers, the water collected in the various rain-water pools all over the place, begins to turn green. And an examination of a drop of this green water shows countless numbers of some member or members of the Volvocaceae. The following genera have been collected by me in these pools during the summer monsoon season : — Chlamydomonas, Carteria, Gonium, Pandorina, Eudorina, and Volvox. All excepting Volvox were found in great abundance.

The behaviour of these organisms in the summer rain-water pools is rather interesting. As was pointed out above, the rains during this season are small in quantity and occur at frequent intervals. During the rainless days succeeding a rainy day the water level in the pool goes down gradually and when almost near the bottom a fresh rain comes in and the level of the water goes up once more ; and this process is repeated again and again throughout the season.

A few days after the filling up of a pool, the level goes down somewhat and a greenish scum is noticeable on the surface which soon extends deeper and becomes greener. And an examination of a drop of this green water shows large numbers of some member or members of the Volvocaceae (mixed up of course with some diatoms, and some other plankton algae, such as Scencdesmus, Coelastram, etc.). As the level goes down, the water gets even more green in colour. But when the pool gets filled up in the next rain, the green colour does not get thinner through dilution but disappears totally. After the level goes down somewhat again as before, a thin green scum is formed and as the level goes down still more the colour deepens and the organisms are seen in large numbers as before. And this interest- ing process is repeated again and again. There is yet another interesting behaviour on the part of these organisms. Very early in the mornings the organisms are not so noticeable, but a little later they swim actively all over the water. Towards the middle of the day they recede below again, and towards the evening they float up and form a sort of green mucilaginous film on the surface. In this condition they are generally more quiescent and often are dividing and forming daughter cells or colonies.

Beach Pools

Sand is removed from the Madras Beach for building purposes and fairly deep hollows are formed in the sands very near the shore. During the monsoon seasons a large quantity of rain- water flows down from the Marina Road (which runs parallel to the seashore and is at a higher level than the sandy beach), and fills up these depressions in the sand. Again during the rainy weather the waves are rougher and some sea water also flows over the sandy shore into these pools. These pools, sometime after their formation, both during the summer monsoon and winter monsoon seasons, are soon peopled by large numbers of some member or members of the Volvocaceae. The most interesting feature of these pools is that the wet sand all round the edge of the pool to a distance of a foot or two is quite green. On lightly scraping the surface with a knife I found that the sand was green only near the surface. Microscopical examination of the wet sand revealed a large number of Chlamydomonas and other members of the Volvo- caceae swimming actively in the thin film of water surrounding the sand particles. Some of this green sand was collected by scraping the surface lightly and shaken with some water. The water became quite green leaving the sand in its normal colour. A drop of this green water examined under the microscope showed the organisms actively swimming about. I found this same preference for the wet banks in other similar situations also. The organisms prefer this situation probably because of better conditions of aeration. In another instance I found that a depression in the beach sands was merely wet at the bottom without any water in it. The surface of this depression was covered by a very thin layer of dry sand which was blown over by the wind. On removing this dry sand lightly with a knife I found the lower layer of sand wet and greenish. I also found that the greenness was confined only to a thin layer at the top and lower down the green colour was absent. I shook some of this green sand with water and found that its greenness was due to a large number of Chlamydomonadine cells which had lost their cilia and were quiescent.

2563—43 This invasion by the free swimming Chlamydomonas of a wet sub-aerial region, in the first place, and, in the second place, its losing its cilia under a comparatively drier condition, suggests a probable method by which some of the sub-aerial unicellular Green Algae might have evolved from some free swimming Chlamydomonadine type.

Genera collected

The following genera have been collected by me at Madras : — Chlamydomonas, Carteria ; Gonium, Pandorina, Eudorina, Pleodorina and Volvox. The most common ones were Chlamydomonas and Car- teria among the unicellular forms, and Pandorina and next Eudorina among the coenobial forms. Gonium was a rarer form. Pleodorina was still rarer. But the rarest was Volvox.

These forms I must however point out were always associated with a sprinkling, large or small, of other plankton forms of Algae, and Flagllate (such as Euglena, etc.).

One feature which was particularly noticeable in the summer rain-water pools was the complete absence of Spirogyra and the other filamentous Green Algae, and the extreme scarcity of the Blue Green Algae.

Enemies of the Volvocaceae

The bottom of the pools very often showed large numbers of amoebae ; and these injested a large number of the unicelluler algae during the times when the latter settled down at the bottom. I came across many amoebae, with Chlamydomonas in their bodies and I saw some actually in the act of in jesting them.

In another pool I found Pandorina and Eudorina swimming with one or two, sometimes even four, or five, small round colourless Protozoons attached to their mucilaginous envelope. On further exa- mination I found that these Protozoons gradually made their way in- side and swallowed some of the cells of the colony. Later on they escaped from the colony leaving a big rent in the mucilaginous enve- lope. Many specimens of Pandorina and Eudorina were found by me with a big rent in their body and a few of their cells missing.

Another enemy which plays havoc with these forms is a kind of Eotifer. This was found in very large numbers in a tub containing Pleodorina and Eudorina devouring them in large numbers.

I came across a Chironomus larva ("Blood-worm"), devouring large quantities of Pandorina. This larva has the habit of constructing out of the materials of its environment such as silt, etc., a kind of case for itself by fastening with the help of a silk-like secretion of its sali- vary glands. I kept some quantity of live Pandorina in a dish. The next morning I found a large number of green cases attached to the bottom of the dish ; and inside each case was a Ghironomus larva which escaped out on being disturbed with a needle. An examination of a green case showed that it was made up of large numbers of Pandorina colonies. The larva on being examined under the micros- cope showed that it had been feeding on these Pandorina colonies ; for its alimentary canal was full of them.

Another curious phenomenon noticed by me was a tiny unicellular Blue Green Alga attached to the body of a Ohlamydomonas. This Blue Green Alga was evidently getting a free ride at the expense of the Ohlamydomonas and benefiting by the advantages of the locomotion, viz., better aeration and better food supply. Often there was more than one rider on a single Ohlamydomonas, sometimes as many as five or more. I occasionally came across a few cases where the riders were too many in number for the poor Ohlamydomonas to carry, which was therefore unable to move at all.

Summary

The following members of the Volvocaceae have been collected from Madras : --Ohlamydomonas, Carteria, Gonium, Pandorina, E ado - rina Pleodorina and Volvox. The last two are generally very rare forms.

Though thase forms may occur in various parts of the year and in various situations, they attain their greatest luxuriance only in the many small rain-water pools formed by the showers of the Summer Monsoon season which at Madras are generally light and irregular, though frequent.

The organisms seem to like light of moderate intensity. They come up sometime after sun-rise and if, in the middle of the day, the sun-light is too strong, recede below and come up again towards the latter part of the day and form a thick green film on the surface. In this condition the organisms are generally very inactive. They sink down again during the night. If the weather is cloudy they do hot sink down in the middle of the day, nor do they float up, towards the evening to form a film, but are active throughout the day.

In certain rain-water pools formed in the Madras Beach, these organisms are often found in large numbers on the wet sand around the pool giving it a green colour. This situation is sought by them probably for securing better aeration. In one of these pools where the water had disappeared the wet sand was greenish, and its greenness was due to many quiescent Chlamydomonadine cells without cilia, This invasion of a sub-aerial region by a free swimming aquatic form suggests how some sub-aerial unicellular Green Algae might have originally evolved from some free swimming Chlamydomonadine type. Certain very small animals were observed to live on some mem- bers of this group. The most interesting among them -was a Chiro- nomus larva (a kind of " blood-worm"), which fed very largely on Pan- dorina colonies and at the same time made a case to live in out of these colonies by fastening a large number of them together by means of a silk-like secretion from its salivary glands.

Literature Cited

1. Carter, H. J. — On Fecundation in Eudorina elegans and Crypto-

lena : Ann. and Mag. Nat. Hist. 3, II, 237, 1858.

2. Fritsch, F. E; — The Occurrence of Pleodorina in the Freshwater

Plankton of Ceylon, New Phyfc. Ill 122, 1904.

3. Do. The Sub-aerial and Freshwater Algal Flora of the

Tropics. Annals of Botany, XXI April 1907.

4. Do. A General consideration of the Sub-aerial and

Freshwater Algal Flora of Ceylon. Proc. Koy. Soc. B. Vol. 79, 1907.

5. Wallicb, G. C— Desmidiaceae of Lower Bengal. Ann. Mag. Nat.

Hist. Ser. 3, V. i860.

6. West, W. and West, G. S. — A contribution to the Freshwater

Algae of Ceylon. Trans. Linn. Soc. Bot. Ser. 2, Vol. VI, part 3, 1902.

7. Do. Freshwater Algae from Burma, including a few

from Bengal and Madras. Ann. Eoy. Botan. Gard. Calcutta, Vol. VI, part II, 1907.

8. West G. S.— Algae, Cambridge Botanical Handbooks, Vol. I.

9. Do. Some new African species of Volvox. Journ.

Quekett. Micr. Club. Ser 2. XI, Nov. 1910. lO.IZeller. — A few records of Algae collected by Kurz in Arracan and British Burma. Journ. Asiat. Soc. Bengal, XLII, pt, ii, 1873.