ON TWO SPECIES OF MARINE INTERSTITIAL TARDIGRADA FROM THE EAST COAST OF INDIA

BY G. CHANDRASEKHAP~RAO (Zoological Survey of India, 27, Chowringhee Road, Calcutta-13) Received April 16, 1970 (Communicated by Dr. B. S. Chauhan, F.A.se.)

ABSTRACT The paper reports the occurrence of two species of marine interstitial , Stygarctus bradypus Schulz and carnonensis Fize, from Indian waters. The morphological variations of the Indian forms differing from the EuropeaN. species are given, along with some ecological notes.

INTRODUCTION

SEVERAL new genera and species of marine interstitial tardigrades have been described in recent years from different parts of the world (for bibliography see Renaud-Mornant, 1967). But no previous records of the fauna are known from Indian waters. The preliminary results of a collection of tardigrades made by the present author on the Waltair coast, has been published elsewhere (Chandrasekhara Rao and Ganapati, 1968). During a general marine faunistic survey of the Orissa coast undertaken by a party of the Zoological Survey of India in December 1966, the author had an oppor- tunity of examining the intertidal sands at Purl and Konarak. Two species of Tardigrada, Stygarctus bradypus Schulz and Batillipes carnonensis Fize, were encountered in the collections. The two species were also recorded on the Waltair coast and the specimens from both the areas are morpho- logically identical in structure. The occurrence of the European species on Indian coast throws considerable light on their geographical distribution.

Order : Sub-order : Family : Genus : Stygarctus Schulz Stygarctus bradypus Schulz, 1951 (Figs. 1-3) 53 54 G. CHANDRASEKHARA RAO

Schulz (1951) described the species from the beach sands of the Baltic and North Sea coasts. Later, its occurrence has been reported from Arca- chon and Bahamas in the Atlantic waters (Renaud-Debyser, 1959 a, b). The specimens collected in the present study conform to the original description except for certain minor variations in the structure of the body. The adult specimens on this coast reach a length of 120-140/z and 50-60 tz in width, while those of the European species, according to Schulz, vary between 90-150/z in length. The disposition of cephalic appendages resembles that of the specimens described by Schulz. The dimensions of the head appendages are as follows: median cirrus-12#, internal buccal cirrus-10 tz, external buccal cirrus -12 t~, cephalic papilla - 18 t~, lateral cirrus - 12 # and clava - 8 tz. The mouth cone is often protruded, giving the appearance of a conical lobe on the anterior part of the head. In the type description, the pair of dorsal hooks which are disposed obliquely on the posterior border of the second trunk segment are 23-25 tz long and slightly notched at their distal ends. In the Indian specimens, on the other hand, the dorsal hooks are 36-40 t~ long with a strong bifurcation at their distal ends.* The pair of lateral bristles on the terminal trunk segment are 32 t~ long. The divergent spikes on the posterior border of the terminal segment are slender and reach a length of 40/z. All the four pairs of walking legs are seen in dorsal view extending from lateral and posterior sides of the trunk. The digits are finger-like, while those figured by Schulz are claw-like. The two internal toes of all the legs bear slender bristles. The cuticle is opaque and light-brown. Intervening the first and the second and the second and the third trunk segments occur two pairs of dorsal oval patches, differing in shape from the rhomboid patches of the European specimens. Other features agree with those described for the type material. Family : DISCOPODIDAE Genus : Batillipes Richters .Batillipes carnonensis Fize, 1957 (Figs. 4-5) Fize (1957) described the species from the beach sands at Carnon (Hearault, France). The individuals on the Indian coast conform to the original description except for minor variations in body size, position of exter- nal buccal cirfri and the dimensions of cephalic appendages.

* However, in a personal communication Dr. Renaud-Mornant stated that the pair of dorsal hooks on the European specimens show a terminal bifurcation similar to that of the Indian speci- mens. Marine Interstitial Tardigrada from the East Coast of lndia 55

Fize gives the maximum length of the Carnon specimens as 220 tz, while the Indian specimens are smaller varying between 90-110 t~ in lengthi" and 46-54 t~ in maximum width. In the Mediterranean specimens, the external buccal cirri take their origin at the base of the inner side of the lateral cephalic lobes, while the cirri are inserted in the Indian specimens on the summit of the lateral cephalic lobes along with the clava and lateral cirrus. Among the known species of the genus Batillipes, the disposition of external cirrus in the Indian specimens occupies an intermediate position between B. carno- nensis of the Mediterranean Sea and B. similis Schulz (1955). However, this singular variation from type description does not appear to warrant the creation of a new species, as all other characters correspond with specimens from both the regions.

I 2

FIGS. 1-3. Stygarctus bradypus Schulz. Fig. 1. Adult from Indian waters, dorsal view. Figs. 2-3. Head and second trunk se[ment of the European specimens (after Sehulz, 1951).

The dimensions of the head appendages are as follows: median cirrus--10/z, internal buccal cirrus--13 tz, external buccal cirrus--16 tL, clara--20 t~, and laternal cirrus--24 tz. In general, the length of cephalic appendages in Indian specimens is seen gradually to increase from the median cirrus to the lateral cirrus, differing from the European specimens. Each of

"i' In a personal communication Dr. Renaud-Mornant stated that the body size in the genus Batillipes depends very often on age, availabilit}, of food and n~tture of environment, 56 G. CHANDRASEKttARA RAO the first three pairs of legs bears a slender spine 3 tz long on the dorsal surface. These spines have not been reported on the Mediterranean specimens at the time of their description. Mrs. Fize noticed the presence of these spines in a subsequent study of the material (personal communication). The curved spines on the inner side of the fourth pair of legs attain 12-15 tL while the caudal spine reaches 10-12 t~ long. The cuticle is transparent and finely striated. The posterolateral corners of the body bear a pair of slender bristles 15/z long on the dorsal surface, characteristic of the genus. 4 5

FlOS. 4-6. Figs. 4-5. Batillipes carnonensis Fize. Fig. 4. Adult animal from Indian waters, dorsal view. Fig. 5. Anterior end of Mediterranean specimens showing head appendages (after Fiz'e, 1957). Fig. 6. B. similis Schulz. Anterior end showing head appendages (after Schulz, 1955).

ECOLOGICAL NOTES

Five specimens of S. bradypus were collected at Puri and Konarak while two specimens of B. carnonensis were encountered only at Konarak in association with the former species. Both the species were encountered in the same biotope throughout the year in moderate numbers in the beach sands on the Waltair coast. The forms inhabited the medium sands 25-40 cm. below surface near the half-tide level. The texture of the sands varied between 200/~ and 500 tz in mean diameter. The organic detritus of the sands appeared rich in some of the finer substrates. The temperature in the habitat varied from 24 ° C, to 28 ° C., while the salinity of the interstitial water ranged Marine Interstitial Tardigrada from the East Coast of India 57 between 28~oo and 31~oo. The habitat is associated with considerably low values of dissolved oxygen compared with adjacent sea-water.

The tardigrades keep themselves slowly creeping over the surfaces of the sand grains. They are sluggish and gregarious in habits. The forms exhi- bit a positive thigmotaxis and firmly adhere to sand grains when there is a commotion in the environment. In feeding, they are omnivorous, sucking fine particles of detritus, bacteria and smaller protozoans. Other groups of interstitial encountered in the same biotope along with the tardigrades are ciliates, nematodes, gastrotrichs, oligochaetes, isopods and halacarids.

ACKNOWLEDGEMENTS

The author is grateful to Dr. A. P. Kapur, Director, Zoological Survey of India, for facilities and affording opportunity to participate in the Orissa Coastal Survey. His grateful thanks are also.due to Dr. J. Renaud-Mornant, Museum National d'Histoire Naturelle, Paris, for furnishing some relevant information pertaining to the identification of the two species.

REFERENCES Chandrasekhara Rao, G. "The interstitial fauna inhabiting the beach sands of Waltair and Ganapati, P. N. coast," Proc. hath. lnst. Sci. lndia, 1968, 34 (2), 82-125. Fize, A. .. "Description d'une espece nouvelle de Batillipes ¢arnonensis," Bull. Soc. Zool. Ft., 1957, 32, 430-33. Renaud-Debyser, J. .. "Sur quelques Tardigrades du Bassin d'Arcachon," Vie et Milieu, 1959a, 10 (2), 135--46. .. "Etudes sur la faune interstitielle des iles Bahamas. III. Tardi- grades," Ibid., 1959b, 10(3), 296--302. Renaud-Mornant, J. .. Tardigrades de la Baie Saiut-Vincent Nouvelle- Caiedonie, Editions de la Fondation Singer--Po]ignac, Paris, 1967, pp. 103-17. Schulz, E. .. "Uber Stygarctus bradypus einen Tardigraden aus dem Kusten- grundwasser und seine phylogenetische Bedeutung," Kieler Meeresf, 1951, 8(1), 86-97. .. "Studien an marinen Tardigraden," Ibid., 1955, 11 (1), 74-79.