Phoronida: India
Contents |
Faunal Diversity in India: Phoronida
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
The phylum Phoronida comprises slender worm-like, free-living solitary and sedentary creatures of various sizes housed in a self-secreted tube of leathery, membranous or limy texture, with a terminal lophophore in the form of a horse-shoe that embraces the mouth, with recurved digestive tract having an anal opening near the mouth, with a closed circulatory system and a pair of metanephridia.
Status Of The Taxon
Global and Indian Status
Eleven species are so far known under this taxon found in several substantial areas of all oceans and seas and most of the species can be considered as cosmopolitan. Of them, only three species, one being cosmopolitan, are reported from the Indian coast. No phoronid species has yet been described as a keystone species.
Distribution
Of the three species, cosmopolitan form Phorollis australis are reported to occur in Gujarat coast; second one, Phorollis psammophila (= P. arc/litecta), an Atlantic form, reported from Porto Novo, Tamil Nadu coast and the Gulf of Mannar and the third one, Phorollis bhadllraii described from the sandy beach of Digha, West Bengal and the species is not rec0r;Ped elsewhere so far.
Biological Diversity And Its Special Features
As a small group this phylum possesses only two genera, namely, Phorol1is and Phorol1opsis and of them, former contains eight species. The genus Plzorollopsis possesses the epidermal collar-fold below the lophophore, while the genus Phorollis has no such collar-fold.
Pltoro"is b1laduraii lives singly in sandy bed and P. psammophila dwells singly in a separated tube while P. australis is a commensal form inhabiting inside the leathery tube of Ceria"t/lIIs sp., a sea-anemone.
Endemicity
Only one species PllOronis bltaduraii is endemic to Indian coast and reported from sandy bed of Digha coast, West Bengal as mentioned earlier.
Value
This group is still regarded as of academic" as well as scientific interest and used in the biological laboratories for scientific experiments.
Threats And Conservation
The main threat to this taxon is the destruction of habitats. During educational field trips the college students regularly visit sea coasts and collect Ceriant1lus (Sea-anemone) in which the phoronid inhabits. Moreover, for collection of this sea-anemone they dig the substratum at random and thereby damage the habitat. Very recently measures have been taken to prevent the destruction of habitat. Government has declared the area of Gulf of Mannar and Gulf of Kutch as Marine National Park and thereby removal of natural wealth from the aforesaid areas may be checked.
Selected References
Ganguly, D. N. and Majumder, N., 1967. On a new species of Phoronis (Phoronida). J. %001. Soc. India, 19 (1) : 7-11. Gravely, P. H., 1927. Gephyrea and Phoronis. Bull. Madras Govt. MilS., n.s. 1 : 88. Haldar, B. P., 1981. On the climatology of the Beyt Island, Western India with special reference to the systematics of Plwronis australis Haswell (Phoronida). Ind. J. Zoot., 22(1) : 59-63. Nair, K. K. and Shaw, J. S., 1956. On the occurrence of Plwronis al/stralis, off the coast of Port Okha (Okhamandal, India). J. Univ. Bombay, 2S : 66-69.
Phoronida
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Introduction
Phoronids, so far known, are limited to shallow waters of tropical and temperate zones. They are best known along the European coasts as the marine littoral fauna and are better known than elsewhere.
The rust scientific notice of the phylum was after the finding of J. Muller (1846, 1847) of a characteristic swimming larva which was mistaken as an adult form and named as Actinotrocha branchiata. Gegenbaur (1854) correctly recognised it as a larval stage. Adult phoronid was discovered by Wright (1856) and gave the name Phoronis (from Greek mythology) without any idea of their relationship to the actinotroch larva. Kowalevsky° (1867) studied the metamorphosis actinottoch larva and realised that it is the larval stage of Wright's worm Phoronis. The name Phoronida for the group was coined by Hatschek (1888) and was differently spelt by Lang (1888) as Phoronidea. The former name was adopted by Hyman (1959) who placed it in the rank of phylum.
The Phoronida are tubicolous, vermiform coelomates, with a terminallophophore in the form ofa horse-shoe that embraces the mouth, with recurved digestive tract having an anal opening near the mouth, with a closed circulatory system and a pair of metanephridia.
The Phoronida are slender solitary worms that inhabit leathery tubes, glued with particles of foreign matter. A number of individuals are commonly associated together, their tubes being twisted around one another; but their bodies are separate. The most conspicuous feature of the animal is its terminal crown of tentacles or lophophore, consisting of a single row of tentacles borne on a double ridge of body wall, curved into crescen°tic shape. Mouth lies between two ridges of the lophophore. The anus is dorsal and outside two lophophore, at the summit of a median longitudinal ridge. The body is elongated aborally and may attain a length of about 20 cm. Phoronids are hennaphroditic or dioecious.
The Phoronida are exclusively marine and are found sparingly over a wide geographical range but are apparently absent from polarand subpolar waters. They are limited to the upper littoral zone (above 50 m) and no record from deep sea till date is available. They range from very small about 6 mm long with 18 to 25 tentacles to about 200 mm with around 1600 tentacles. Species living in sandy bottom• have separate, perfectly cylindrical, erect tubes, covered with fme sand grains.
In some species, the tubes of the aggregation may form an inextricable tangle adherent to shells, pilings, and the like and in others the membranous tubes enclosing the worms are themselves enclosed in burrows of mollusk shells or calcareous rock. Most remarkable habitat has been observ~ in Phoronis austrialis, whose delicate transparent tubes occupy the interstices of the cni~Cerianthus and when the host with draws inside its tube, the phoronid is seen radiating in the expanded strate from the aperture. Phoronids exhibit great power of regeneration, when kept in laboratory aquaria, often casting their tentacular crowns and regenerating new ones.
Historical Resume
The knowledge of phoronids from the Indian coast is very poor. The pioneering work on this particular group comprising only a couple of species from India, however, dates back to the earlier part of this century. Gravely (1927) explored, at least, one undetermined species of Phoronis from the Porites Bay ofKrusadai Island in southern India. Subsequently, Nair and Shaw (1956) recorded Phoronis australis from the Beyt Island of Okhamandal in western India while Ganguly and Majumder (1967) described Phoronis bhaduraii from Digha, Midnapore district in eastern India. The record of P. australis in the Beyt Island by Nair and Shaw was confumed by Haldar (1981).
Estimation of Taxa
There are 11 known species assigned to two genera, Phoronis and Phoronopsis. Genus Phoronis is identified by the absence of the epidermal collar fold below the lophophore where as in die genus Phoronopsis it is present
Emig (1982) reviewed the biology of Phoronida and provided a list of species as follows:
Genus Phoronis Wright, 1856
P. australis Haswell, 1883 (includes P. buskii)
P. bhadUTaii Ganguly &Majumdar, 1967
P. hippocrepia Wright, 1856 (includes P. caespitosa, P. capensis, P. gracilis, P. kowalevskii)
P. ijimai Oka, 1897 (includes P. vancouverensis)
P. muelleri Selys-Longchamps, 1903
P. ovalis Wright, 1856 P~ pallida Silen, 1952
P. psammophila Corl, 1889 (includes P. sabatieri &architecta)
Genus Phoronopsis Gilchrist, 1907
P. albomaculata Gichrist, 1907
P. californica Hilton, 1930
P. harmeri Pixell, 1912 (includes P. pacifica, striata &viridis)
Distribution pattern of Phoronida in India
Region No. 0/ species
Gujarat including Gulf of Kutch 1 Tamil Nadu, including Gulf of Mannar 1 West Bengal 1
As per the available infonnation on 3 species known from India, P horonis australis is found in the tubewall of cerianthids, P. psammophila lives in the soft substratum and P. bhadurii occurs in compact sandy substratum.
Besides taxonomy no other infonnation on this group, except Haldar's (1981) contribution on the ecology and systematics of P. australis is available.
Expertise India
In ZSI
B. P. Haldar, Zoological Survey of India 27, J.L. Nehru Road, Calcutta -700 016
Elsewhere
K. Balasubrahmanyan, Centre of Advance Study in Marine Biology, Annamalai University, Parangipattai, 608 502, Tamilnadu
Abroad
C. C. Emig, Museum National d'Histoire Naturelle, Rue de Buffon, 75231 Paris, Cedex OS, France.
S. F. Rainer, University of New South Wales P.O. Box 1, Kensington New South Wales 2033, Australia
Selected References
Emig, C. C. 1974. The systematics and evolution of the phylum Phoronida. Zeit. Zoo I. Syst. Evol., 12 (2) : 128-151, 20 figs., 3 pIs, 9 tabs.
Emig, C. C. 1982. The biology of Ph or onida. Advances in Marine Biology, 19 : 1-89.
Hyman, L. H. 1959. The Invertebrates : Smaller Coelomate Groups. McGraw-Hill Book Company, New York, London, Toronto, : 228-272.
