Porifera: India
Contents |
Faunal Diversity in India: Porifera
This is an extract from FAUNAL DIVERSITY IN INDIA Edited by J. R. B. Alfred A. K. Das A. K. Sanyal. ENVIS Centre, Zoological Survey of India, Calcutta. 1998 ( J. R. B. Alfred was Director, Zoological Survey of India) |
Introduction
Sponges include a group of sedentary, multicellular, marine or rarely freshwater filter-feeding animals possessing porous body. Hence these are called porifera or pore-bearers. This group is included under the phylum Porifera under the subkingdom Parazoa and occupies a position in between single celled protozoa and the most advanced 3-layered or triploblastic animals, the metazoa•. This group has an evolutionary history of about 570 million years and is represented in the extant oceans by about 5000 species now reduced to 4562 species by a latest revision (Table 1). Body 'layers' in this group are only two (i.e., diploblastic) with an outer pinnacoderm and an inner choanoderm (ectosome and endosome respectively) enclosing a middle undifferentiated mesohyal containing wandering cells. Flagellated cells lining specialised chambers are peculiar to sponges. Sponges have no histological system, but they possess only functional systems; cells can change their structure, function and position as per necessity. These peculiarities make sponge cells quite dear to physiologists and immunologists alike.
Status Of The Taxon
Global and Indian Status
Extant sponges are divided into 4 Classes; they are : Class I. Calcaria or Calcispongiae or Calcareous sponges: Typically marine, skeleton made of CaC03 and microscleres. Class II. Demospongiae or Silicious sponges: Skeleton made of hydrated silica in the form of spicules which are divisible into mega and microscleres. Some may have spicules and spongin fibers while others have only spicule or spongin fibers. Some may incorporate arenaceous objects (sand grain, foraminiferan test and so on) into their body for rigidity.
Class III. Hyalospongiae or Hexactinellida or Hexactinellid or Glass sponges: Skeleton of hydrated silica, the spicules 6-rayed as the name denotes and divisible into mega and microscleres, the former may, in some cases fuse to form' a compact felt-work. Class IV. Sclerospongiae: A very recently discovered group with spicules made of silica, CaC03 and spongin.
A comparison of the World and Indian poriferan diversity is shown in Table -1. Table -1 Showing number of species of Porifera reported from world and India Class World species Indian species 0/0
, 500 species reduced to 47 species by a latest revision and thus reducing 5000 world species of Porifera to 4562 as shown above.
Distribution
Among the sponges members of the Class Demospongiae are widely distributed. They inhabit interidal areas to hadal depths in different concentrations. In the intertidal arecr these sponges grow to massive form within the reach of any collector, and hence these are extensively used in biochemical studies. Data collected after intensive survey indicate that the Gulf of Mannar and Palk Bay are quite rich in sponge growth. A total of 275 species has been already recorded form these two areas. Specimens usually attain massive size and hence form source material for bioactive assays. Numerical abundance from other areas are : Gulf of Kutch-25 species, Andaman and Nicobar group-61 species. Nothing is known on the numerical abundance of sponges from other areas of the Indian seas. Lakshadweep group of islands have been surveyed in the past thoroughly and these surveys revealed the presence of 91 species of silicious sponges in the various Islands.
Another interesting finding is the wide distribution of coral boring sponges (mainly Cliolla spp.) in the atolls of the Archipelago. 18 species of boring sponges are known from the atolls of Lakshadweep.
List of species that are abundant in different areas is given below: Andaman and Nicobar : Dysidea herbaeea (Keller), Phyllospongia foliaseells (Pallas), P. papyraeea (Esp.) ssp. polyphylla de Laubenfels. Visakhapatnam coast: Tethytimea repens (Schmidt), Callyspongia diffusa (Ridley), C. fibrosa (Ridley and Dendy).
Rameswaram area : Callyspongia spp., Dysidea fragilis (Montagu), lrcinia fusea (Carter), Fasciospongia eavemosa (Schmidt), Dendrilla nigra (Dendy), Haliclona temliramosa (Burton), Sigmadocia fibulata (Schmidt), 10trochota baculifera (Ridley), Tedania allhelans (Lieberkuhn), Endectyon frllticosa (Dendy), Clathria frondifera (Bowerbank), C. procera (Ridley), Biemna fortis (Topsent), Spirastrella inconstans (Dendy), Prostylyssa foetida (Dendy), Cinaehyra cavernosa (Lmk.), Aurora globostellata (Carter). Tutjcorin area: Petrosia testudinaria (Lmk), Clathria frolldifera (Bowerbank), Axinella donllalli (Bowerbank), Spirastrella inconstans (Dendy), Prostylyssa foetida (Dendy). Lakshadweep : Heteronelna erecta Keller, Callyspongia fibrosa (Ridley and Dendy), Tedania anhelans (Lieberkuhn), Sigmadocia fibulata (Schmidt).
Distribution of boring sponges in the natural molluscan beds of chank, mussel, rock oyster, pearl oyster, etc., found along the southwest coast of India has been worked out. It could be seen from the survey that 6 species of boring sponges are very active in these beds and all are potentially capable of devastating the beds totally. Above studies further revealed that some boring species, which are totally inactive in natural condition, may suddenly become active at time causing wide-spread mortality to molluscs.
Detailed investigations made in the past on boring sponges infecting the economically important molluscan beds and coral reefs revealed the existence of 32 species of boring sponges referable to 13 genera under 3 orders, viz., Hadromerida, Epipolasida, and Carnosida, the dominant family being Clionidae of the Order Hadromerida.
Biological Diversity And Its Special Features
An examination of the sponge fauna of Indian seas reveals that it is dominated by Demospongean species (88.8%) followed by those of
Hyalospongiae (9.1%) and Calcispongiae (2.1%) (Table 2). This composition is in full agreement with that in the world oceans. It is stated in literature that only 60% of the total Indian sponge fauna is documented till date. A thorough qualitative appraisal only will reveal the actual.
Endemic And Threatened Species
13 species of freshwater sponges are reported to be endemic to India based on our present level of knowledge. In the marine realms it is impossible to evaluate endemism as many of our inshore areas and also of other countries are poorly investigated. No sponge of Indian seas is considered a 'threatened species' in the strict sense of the term. No species of sponge from India is included in the Indian or International Scheduled list, and are presently not covered under any law.
Value
Recent studies revealed that sponges contain several peculiar chemical compounds which are not found in any other animals. Arabinose nucleosides isolated from Teillya cnJPla have proven cancer inhibiting properties and this discovery has triggered off a world-wide interest in the biochemistry of this group. In India too, several institutions have taken up the extraction and characterization of several pharmacologically active compounds from sponges. Freshwater sponges cannot be said to be of any use to man as they pollute water, block up water pipes and cause irritation to human skin through contact. Some recent publications show that these sponges would be of much help in water quality and palaeoclimatic studies. Sponge cells of both marine and freshwater may also serve as a mighty tool in both cellular and immunological studies.
The boring sponges cause Widespread mortality among corals. These sponges etch out minute CaC03 particles of identical size and shape from the coral substrate, both living and dead and hence this can be considered bioerosion on a microlevel. Since this type of etching out is going on in a microlevel nobody will take notice of it easily. Such weakened coral substrate may crumble at slightest pressure causing landslides. This problem should be tackled by both geologists as well as biologists alike for a better understanding of the impact of waves and tides on a completely riddled out coral frrne-work with a view to suggesting remedial measures in time.
Boring sponges can cause considerable damage to the outer hard shells of live molluscs (chank, oyster, mussel, etc.) producing several physical and physiological manifestations. Investigations made in the past have revealed that these boring sponges can migrate to culture systems from wild stocks of molluscs causing both physical and physiological 'stress' to cultured stocks resulting in diseases. So far 12 different diseases have been documented from live molluscs. When a boring sponge infects a live pearl oyster shell the oyster will have to waste a lot of nacreous material and energy to repair the holes made at the inner aspect of the shell by sponge. In this process, the pearl producing capacity of the oyster is considerably curtailed. More work in this line is necessary to assess whether sponge infection will reduce the pearl producing capacity of the oyster or not. Two species of boring sponges (Cliona margaritifera and C. lobala) have entered into active phase in our beds around 1980, and these are now spreading in our molluscan beds. The former species caused Widespread depletion of the Ceylon pearl oyster beds around 1902 and then entered into a quiescent stage later. The reappearance of this species in the southwest coast of India poses a serious threat to both southwest and southeast coasts of India where many economically important molluscan beds are located.
It could also be seen that the incidence of boring sponges on the cultured molluscs (raft culture) was higher than that seen on natural molluscan beds.
Number of boring species infecting the cultured molluscs was also found high. The reason is that nature plays an important role in keeping the abundance of these pests at a lower level when untampered by external influences. But increased incidence and also the numerical abundance on cultured molluscs might be an indicating that the ecological equilibrium which is at play in the natural beds is no longer in operation in these artificial systems.
One species of boring sponge, viz., Cliona vastifica, could succeed in migrating to the estuarine realms of our coasts by virtue of its low salinity tolerance. This species might pose a serious threat to our future molluscan culture farms along the various estuaries.
Threats, Conservation And Future Studies
Since no commercial exploitation and export of sponges are attempted at present there is no need to think of any imminent threat of depleting the beds. But in future any attempt to initiate exploitation and export of this commodity should be discouraged. However, those species mentioned against each area under the subhead "distribution" should not be destroyed beyond a certain level even for experimental purposes by the various institutions in India. Scientists from India, interested in getting samples for research, may collect them judiciously without depleting the resources. This may be done by adopting 'conservative pruning' or cutting parts of the specimen leaving the rest in Sitll to regenerate and grow. Blasting and dredging will generate much silt and this may settle on the surface of sponges killing them and hence such activities should be banned. Specimen collectors use certain chemicals to make specimens immobile for a while. Such chemicals are likely to affect sponges which grow in neighbouring areas. So specimen collection using such chemicals should be banned altogether.
Pumping out hot-water/ effluents into the coastal areas by Thermal Plant/Factories should be banned as any rise in temperature might prove detrimental to marine life as a whole. Those who make collections from the intertidal areas may be advised not to tum any stone or coral piece upside down. Some species of sponges, unable to tolerate direct sunlight, settle on the undersurfaces of hard objects and grow. When they are kept exposed to direct sunlight they may perish in a day or two. Sponges constitute a major group among fouling organisms. But hitherto, no exhaustive work has been done on sponges in this regard. An exhaustive survey in this line may be undertaken with reference to culture systems, intake pipes of thermal plants, etc.
A variety (celj/onensis) of the common 'bath sponge' Spongia officina/is is distributed in good concentration along the Gulf of Mannar coast. Ecology and biology of this variety should be studied in detail as it forms a 'store house' of several ch~micals with biomedical properties.
Though India has a vast coast line practically no survey has been made to study the benthic life either quantitatively or qualitatively. This is true with all other minor groups of animals such as alcyonarians, antipatharians, ascidians as well. All these animals have corne into the limelight recently on account of peculiar chemical compounds they elaborate. Prostaglandins extracted from gorgonids, arabinose nucleosides from sponge Tetltya crypta are examples to cite a few. Some of the above resources are now being exported to foreign countries for a paltry sum and these countries are making immense profit from our resources. So what seems quite plausible is that we should step up synthesising these chemicals that act as 'wonder drugs' and then release them in market. Speaking revenue-wise this could be a better deal than sending the valuable resources for a paltry sum.
As the first step in this direction an attempt may be initiated to assess the availability and magnitude of all such minor resources possessing biomedical properties. Extensive survey along the continental shelf of India using unified sampling procedures should be undertaken. The data thus amassed should be entrusted to various experts for further studies leading to the assessment both in time and space. At present we have no expert to study groups such as alcyonaria, ascidian, antipatharia, etc. The responsibility of training hands, wherever necessary, should be shouldered by National Institutions that are competent.
Sponges, as mentioned in the introductory part, form an ancient group which can elaborate peculiar chemical compounds with biodynamic potentials. Arabinose nucleosides isolated from Tetltya crypta and its use in the treatment of cancer have recently triggered off a world-wide interest in this group and since 1963 several groups all over the world are interested in the biochemistry of sponges. In India also several institutions are now actively engaged in this challenging field of research. Though our efforts are still at infancy more and more funding agencies are coming forward to finance any such venture liberally. No doubt, it is a good sign, but unless the activities of each research group are monitored well from the inception itself there is every chance that research activity of one group may get duplicated by others unknowingly.
It is generally seen that chemical studies relating to a particular species of sponge culminate in the isolation and characterisation of a particuIaz: chemical compound, but its potential as drugs is neither assessed nor attempts to release it in market as drugs are made. This will relegate the status of these peculiar chemicals as mere subjects of academic interest. Hence, institutions competent enough to tackle the follow-up action should come forward to assess the potential of these chemicals as drugs and their use in the treatment of systemic diseases in man and animal. Perusal of literature dealing with marine products chemistry reveals that many species that are distributed in the Indian seas have been thoroughly worked out in the past by other countries. As such, an inventory of such species becomes inevitable and this could be done partly by gleaning through existing literature and partly through direct contact with foreign research organisations. It is also necessary to have proper interaction with major museums of the world as well as with experts mthe various fields of zoology for training our Scientists in the respective fields.
Selected References
Annandale, N. 1915 a. Indian boring sponges of the family Clionidae, Rec. Indian MilS., 11 : 1-24. Annandale, N. 1915 b. Some sponges parasitic on Clionidae with further notes on that family. Ibid., 11 : 457-478. Annandale, N. 1911. Freshwater sponges and polyzoa, Fallna British India, including CelJlon and Bllrma, pp. 27-126, 241-245. Burton, M. 1963. A revision of the classification of the Calcareous sponges. British Mus. (Nat. Hist) Pub\., pp. 1-693. Burton M. & Rao, H. S. 1932. Repolrts on the shallow-water marine spognes in the collection of the Indian Museum. Rec. Indian Mus., 34 : 299-356.
Dendy, A. 1887. The sponge fauna of Madras. A report on a collection of sponges obtained inthe neighbourhood of Madras by Edgar Thuston. Ann. Mag. nat. Hist., 20(5) : 153-164. Dendy, A. 1915. Report on the calcareous sponges collected by Mr. James Hornell at Okhamandal in Kattiawar in 1905•1906. Rep. Govt. Baroda Mar. Zool. Oklultlumdal, 2: 79-91. Dendy, A. 1916. Report on the non-calcareous sponges collected by Mr. James Hornell at Okhamandal in Kattiawar in 1905-1906, Ibid., 2 : 96-146. Dendy, A. & Burton M. 1926. Report on some deep-sea sponges from the Indian Museum collected by R.I.M.S. Investigator. I. Hexactindlida and Tetraxonida (Pars). Rec. Indian Mus., 28 : 225-248.
Khera, S. & Chaturvedi, Y. 1976. Check-list of Indian Freshwater sponges. Miscellaneous publication occasional paper No.4, Rec. zool. Surv. India, 1-29 pp. Kumar, D. A. 1925. Report on some Tetraxonid spongs in the collection of Indian Museum. Rec. Indian Mus., 27 : 211-229.
Penney, J. T. & Racek, A. A. 1968. Comprehensive revision of a worldwide collection of freshwater sponges (Porifera: Spongillidae). Bull U.S. natn. Mus., No. 272 : 184 pp. Soota, T. D., Pattanayak, J. G. & Saxena, M. M. 1983. On some freshwater sponges from Gujarat (India). Rec. zool. Surv. India, 81 : 255-260. Thomas, P. A. 1976. The history of spongology of India Ocean. J. mar. bioi. Ass. India, 18 (3) : 610-218 (This contains a number of other references). Thomas, P. A. 1979. Boring sponges destructive to economically important molluscan beds and coral reefs in the India seas. Indian J. Fish., 26 (1 & 2) : 163-200. Thomas, P. A. 1983a. Distribution and affinities of the sponge fauna of the India Ocean. J. mar. bioi. Ass. India, 25 (1 & 2) : 7-16.
Thomas, P. A. & Mathew, K. J. 1986. Sponges collected during the Third Indian Antarctic Research Expedition with descriptions of Isodictya echinata Sp. Nov. Third Indian Expedition to Antarctica, Scientific Reports, 1986. DOD Technical Publication No.3: 109-116.
Vosmacr. G. C. J. 1928. Bibliography o/sponges. Cambridge University Press. pp. 1-234.
