Feeding and digestion in bivalves are considered to be continuous and simultaneous. The tide

influenced physiological changes in the digestive diverticula of Sunetta scripts on the basis of

histological observation was studied. The shape of the digestive diverticula changes in accordance

with the tidal level. The maximum pH value in the mantle cavity was recorded at high tide (7.46) when

the animal was covered by the almost static tidal water, the constancy in the pH of the mantle cavity

was due to the renewal of the water in the mantle cavity. At low tide the pH gradually comes down to

6.87 due to the exposure of the animal and the subsequent non-renewal of water in the mantle cavit

Dravidamani, M

Kasinathan, R

Shanmugham, A

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4 0 . C Y C L I C ACTIV ITY IN T H E DIGESTIVE DIVERTICULA OF SUNETTA SCRIPT A IN A C C O R D A N C E W I T H T IDES M. Dravidamani, A. Shanmugam and R. Kasinathan Centre of Ad\/anced Study in Mirine Biology Parangipettai - 608 502 ABSTRACT Feeding and digestion in bivalves are considered to be continous and simulatnsous. The tide influenced physiological changes in the digestive diverticula of Sunetta scripts on the basis of histological observation was studied. The shape of the disgestlve diverticula changes in accordanca with the tidal level. The niaximum pH value in the mantle cavity was recorded at high tide (7.46) when the animal was covered by the almost static tidal water, the constancy in the pH of the mantle cavity was due to the renewal of the water in the mantle cavity. At lowtida the pH gradually comes down to 6.87 du* to the exposure of the animal and the subsequent non-renewal of water in the mantle cavity. INTRODUCTION ous (Yonge 1923. 1926 a, b; Owen 1966; Purchon 1968). Mansour (1946) and Mansour The effect of tidal cycle on the physiological gek (1946) described the possibility of intra-state of the digestive diverticula of the bivalve cellular digestion in the lamellibranchs. molluscs is known since the work of Yonge (1926a). Though the overall function of The rhythmic activity of the digestive digestive diverticula of bivalves remains a diverticula in different bivalves has been studied matter of controversy, this organ has been the by different authors. Some important works subject of investigation for over 100 years. are by Morton (1956, 1969, 1970a, d, 1971, Feeding and digestion processes in bivalves 1977), McQuiston (1969) and Langton and are considered to be continuous and simultane- Gabbot (1974). 216 CMFRI Perusal of the literature clearly shows that the information on the influence of tidal cycle on the function of digestive diverticula of bivalves is very meagre except a few like Shahul Hameed (1984) in Crassostrea madrasen-sis and Anadara rhombea. The present attempt is aimed at studying the tide influenced physio-logical changes in the digestive diverticula of Sunetta scripta on the basis of histological observations. MATERIAL AND METHODS Fig. 1 Below: Mantle cavity pH in accordance with tidas. The specimens of S. ^Crz/J^a were collected Above: Showing tha different siagss.of the at the intertidal region near the mouth of Vellar d ge.tivediverticula; be — basiphii ceiis; do—digestiva estuary. The collections were carried out at cells fs-fr.gm.ntation spherule.; i - ium.n Ifv — large food vacuoles; n — nucleus; an hourly interval starting from low tide to s f v - s m . l l food vacuoles; wm - waste material. low tide extending over a period of 12 h. For every hour two specimens were collected. Immediately the pH of the mantle cavity was Inspection of sectioned digestive diverticula measured by using a BIOCHEM pm 79 model of S. scripta ftxed at hourly intervals over the pH meter. Then digestive diverticula was tidal cycle revealed that the structure of the dissected out and fixed in Aqueous Bouin's tubule underwent rhythmic histological changes solution. The materials were brought to the in accordance with the state of the tide, laboratory and embedded in paraffin wax. 8-10(i sections were taken and stained in Just before the hightide, the cells of digest-Delafield Haematokylin with Eosin as a coun- ive tubules were flattened (Fig 1). It showed .g^g. jj^ two types of cells (a) the digestive cells; (b) the basophil cells (Sumner 1966a) or 'Young cells' (Yonge 1926) The. basophil cells stained much RESULTS AND DISCUSSION darker than the digestive cells; nuclei were located basally in the digestive cell and the lumen The maximum pH value (7.46) was recorded ^f the tubule was large. During hightide the at hightide when the animal was covered by the digestive cells became swollen slightly and were almost static tidal water; the constancy in the ^^^^ cuboidal (or) columnar in form due to the pH of the mantle cavity was due to the renewal absorption of food material arriving in the lumen of the water in the mantle cavity. Similar ^f ^ ^^^ diverticula from the stomach (absorptive observation was also reported by Morton pj^gse). The number of nuclei in the 'nest (1970a) in C.erfu/a. At lowtide the pH gradually of young cells' increased apparently. After comes down to 6.87 due to the exposure of the hightide the lumen of the tubule reduced animal and the subsequent non-renewal of and the food materials were readily observed water in the mantle cavity (Fig 1). in vacuoles of the digestive cells Shahul ^ • • ., u u .1 Hameed 1984). During lowtide the water in the mantle cavity is not replenished and the metabolic ^^ lowtide the tubules were different in activity depletes the Oj and increases the CO2 condition and the bulges at the base of the level. As a result the pH value of this non- digestive cells projected into the haemocoel due replenished water falls down. This phenomenon ^o the breakdown of food materials in the was also observed by Morton (1970a) in digestive cells. The distal surface of the C. edula. Proceeding hightide replenishes the degistive cells became swollen and was water due to which the PH increases again. loaded with indigestable wastes called BULLETIN 42 2 1 7 fragementation spherules. It has been reported by Morton {1969b) in Dreissena that the distal portion perhaps produce a fragmentation spherules and the proximal portion passes these into the haemocoel with food and waste materials. At a later stage spherules were being budded off from the distal surfaces of the digestive cells in this case the nests of young cells had apparently oriented towards the lumen of the tubules. As a result the length of the digestive cells was mostly reduced and the orientation towards the lumen of the tubule was lost. Approximately 4 h after lowtide the digestive cells are reduced in length as well as in number and only few nuclei were seen. The basiphill cells could not be distinguished from digestive cells. The lubules were in the disintegration phase. Just before the high tide the tubules showed significant increase in the size and number of the digestive cells. The basiphil cells were recognisable in small groups with a few cells (regenerative phase). The structure of the tubules essentially similar to that described in the early hjgh tide of the previous tidal cycle indicating the cyclic nature of the events. In S. scripta the tidal cycle is related with the activity of digestive diverticula. Morton (1969a) opined that the animal when submerged by the tide the food is absorbed in the digestive diverticula during hightide and intracellular digestion takes place within the digestive cells. REFERENCES LANGTON, R. W. AND P. A. GABBOT 1974. The tidal rhythm of extracellujar digestion and response to feeding in Ostrea edulis. Mar, Biol. 24 (2) : 181-187. MANSOUR, K. 1946. Food and digestive processes of the lamellibranchia. Nature, Lond., Vol. 157, pp. 482. MANSOUR K. AND J. J. BEK 1946. Extra-cellular proteolytic and lipolytic enzymes of some lamellibranchs. /Vafure, London, 158 : 378. MCQUISTON, R. W. 1969. Cyclic activity in the digestive diverticula of Lasaea rubra (Montage) Bivalvia : Eulamelamelli-branchia). Proc. malacd. Soc. London, 38: 483-492. MORTON, J .E. I956. The tidal rhythm and action of the digestive system of the Lamellibranchia Lasea rubra. J. mar. bio/Ass. U. /f. 35 : 563 586. MORTON, J. E. 1969 a. Studies on the biology o1 Dre/ssen po/ymorpha paW. 1. General anatomy and morphology. Proc. Mala-col. Soc. London, 38 : 301 -321. MORTON, B. S. 1969 b. Studies on the biology of Dreissena polymorpha pall. II. Correlation of the rhythms of adductor activity, feeding digestion and excret-ion. Proc. Malacol. Soc. Lond, 38 : pp. 401-414. MORTON, B. S. 1970 a. The tidal rhythm and rhythm of feeding and digestion in Cardum edule. J. mar. Biol. Ass. U. K., 50:499-512. MORTON, B. S 1970 b. A note on the cytolo-gical structure and function of the digestive diverticula of Macoma balthica correlated with the rhythm of l\^acoma balthica correlated with the rhythm of the tide. Malacol. Rev., 3:115-119. MORTON, B. S. 1971. The daily rhythm and tidal rhythm of feeding and digestion in Ostrea edulis Biol. J. Linn. Soc. London, 3: 329-342. MORTON, B. S. 1977. The tidal rhythm of feeding and digestion in the pacific oyster, Crassostrea gigas (Thunberg). J. Exp. Mar. Biol. Ecol., 26 : 135-151. OWEN, G. 1966, 'Digestion', chapter 2 In : physiology of Mollusca, Vol. II, Acade-mic Press, Newyork. PURCHON, R.D.I968. The Biology of the Mollusca. Pregamon Press, Oxford, 560 pp. 218 CMFRI SHAHUL HAMEED, P. 1984. Studies on the crystalline style of some bivalve molluscs of Porto Novo coastal waters. Ph. D. Thesis, Annamalai University, pp. 162. SUMNER, A. T. 1966 a. The cytology and histochemistry of the digestive gland cells of some freshwater lamellibranchs J. R. microscr Soc, 85 : 201 -211. YONGE, C. M. 1923. Studies on the compara-tive physiology of digestion. I. The mechanism of feeding, digestion and assimilation in the lamellibranch Mya. Soc. Ex Biol.. 1 : 15-63. YONGE, C. M. 1926 a. The digestive diverticula in the Lameilibranchia. Trans. R. Soc, Edins. 54 : 703-718: YONGE, C. M. 1926 b Structure and physiology of the organs of feeding and digestion in Ostrea edulis, J. mar Biol. Ass. U.K., 14 : 295-386. 

Cyclic activity in the digestive diverticula of Sunetta scripta in accordance with tides

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Cyclic activity in the digestive diverticula of Sunetta scripta in accordance with tides

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