Habitat Ecology of Sea Cucumbers from Thirumullavaram Rocky Shore, South Kerala




Дата канвертавання21.04.2016
Памер35.77 Kb.
Habitat Ecology of Sea Cucumbers from Thirumullavaram Rocky Shore, South Kerala
*Deepa R. Pillai and L. Ponnu.

Post Graduate Department of Zoology, M. S. M. College, Kayamkulam, Kerala, India- 690502.



*Corresponding author email: deepakudassanad@rediffmail.com
Abstract

Sea cucumbers belonging to the class Holothuroidea, are marine invertebrates, habitually found in the benthic areas and deep seas across the world. The present study aimed at identification and study of the ecological aspects of sea cucumbers from the inter tidal rocky shore of Thirumullavaram. The period of study was from February to June 2014. Identification is based on the microscopic examination of spicules. Two species identified in the present study are Holothuria cinerascens and Holothuria pardalis. The water quality parameters in the study area highly influenced the very ecology of the sea cucumbers.



Keywords: Holothuria cinerascens, Holothuria pardalis, rocky shore, Thirumullavaram, spicules
Introduction

Sea cucumbers belonging to the class Holothuroidea, are marine invertebrates, habitually found in the benthic areas and deep seas around the world. They are usually soft bodied echinoderms comprising a diverse group of flexible, worm like organisms with a leathery skin and gelatinous body look like a cucumber. The holothurian takes fine particles of sand and mud into their mouth by means of tentacles. The flexible body wall containing circular and longitudinal muscles and a skeleton made up of isolated calcite particles called spicules. The spicules may toughen the skin and represent a vestige of the normal endoskeleton. Sea cucumbers feed on tiny particles like algae, minute aquatic animals, or waste materials. They are the consumers and bioturbators of surficial sediment. The sea cucumbers are an important component of the marine ecosystem and they play an important ecological role in nutrient cycling and bioturbation processes in marine benthic communities. Aspidochirot sea cucumbers are a conspicuous component of the macrobenthos of trophical marine environments. Their extracts are used in traditional Japanese medicine and several bioactive compounds of medical importance are isolated from sea cucumbers. They play important role in nutrient recycling and bioturbation process. Apart from this ecological significance sea cucumber is processed and the body wall is used as food in beche-de-mer industry throughout Indo-pacific (Conand 1997). Global export trends indicate that wild cucumbers are currently over-exploited (Conand & Byrne 1993).

The intertidal rocky shore is an extreme habitat. Due to water movements associated with tides, waves and spray, conditions affecting different levels on the rocky shore vary continuously. The structure and composition of marine benthic communities are influenced by environmental factors, including temperature, pH, salinity, dissolved oxygen and sediment characteristics. Substrate type and availability of shelter also influence the distribution of sea cucumbers. It has been suggested that alternate feeding strategies co-vary with environmental variables such as pressure, salinity, and physiological effects (Roberts, 2000). The present study investigates identification of sea cucumbers and ecological study of these species collected from Thirumullavaram rocky shore.

Materials and methods

For the study of eco-physiology and feeding biology, two species of sea cucumbers were collected from Thirumullavaram rocky shore (8.90 N, 76.60 E) near Kollam. The area is partially formed of rocky substratum and sand and subjected to heavy wave action. The upper region of the coast is almost protected by keeping massive rock boulders. The massive rock projects from the sea, at about 2 kilometers from the shore which form an ideal habitat to many fouling organisms. It is visible from the shore during low tides. Collections were made from February to June 2014 during low tides. A total of 4 specimens of the two species were collected. Eco physical analysis of water samples were done in all these months.



Collection of sea cucumbers

The two holothurian species collected in this study were Holothuria cinerascens (Brant) and Holothuria pardalis (Selenka 1867) and were collected by hand picking during low tide with the help of local fishermen. They were transported to the laboratory in well oxygenated polytene bags. In the laboratory they were maintained at room temperature (280C-300C) in glass tanks containing sea water and died specimens are preserved in 70% ethanol.

Identification is largely based on microscopic examination of the spicules by placing a small piece of skin on a slide and adding a few drops of NaOH or KOH. The slide was then dried and observed under binocular microscope using high power objective (45x). Drawings were made using camera lucida and identification was made after Clark and Rowe (1971).

Eco physical analysis of Marine water

Water samples were collected fortnightly from the sea surface in a clean polythene container from February to June 2014. Water samples were collected during morning hours in between 8.00 to 10.00 am with 1 litre containers from the sea with the help of local fisher men and analysis were done in the laboratory of MSM College, Kayamkulam. Dissolved oxygen (DO), temperature, PH, salinity and total dissolved solids (TDS) were detected using standard procedures (APHA 2007). ……………….



Results and Discussion

Sea cucumbers are abundant among rocky shore of Kerala. In present study 2 species of sea cucumbers were collected from Thirumullavaram which is rocky belt near Kollam. The ecological parameters of the two species of sea cucumber, and water quality of the study area (table1) were observed and measured during the study period. It was found that Holothuria cinerascens were sluggish and remained in their rocky surface habitat. Holothuria pardalis is somewhat more active. Both the species occurred together in the same region.

The identification of the specimen was done with the spicules collected from body wall. Because of high tide and rough sea, sea cucumbers were not available in all months. Holothuria cinerascens were collected on the months of March and April. Holothuria pardalis was collected on the months of February and April.

Identification

Holothuria pardalis (Selenka 1867) (Class : Holothuroidea; Order : Aspidochirotida; Family: Holothuriidae) This species were 19- 30 cm in length. Tentacle peltate and 20 in number. It is cylindrical and tapering at its ends. It is a small species, with a smooth tegument, and a thin pliable body. Color of the specimen is chocolate brown with 8 to 10 dark spots arranged in two rows along the dorsal side. Its spicules are clumsy tables (Fig. 1 A1, A2) with a low to moderate spire and a spiny disc, and buttons, usually irregular (Fig. 1 B1-B3). Calcareous ring consists of 5 large radials and 5 short interradials.
Holothuria cinerascens (Brant) (Class: Holothuroidea; Order: Aspidochirotida; Family : Holothuriidae)

This species were 9.5 – 11 cm in length. Tentacle peltate and 19 in number. Color of the specimen is dark brown on both dorsal and ventral side. Its spicules were finely spinose rods (Fig. 2 A1, A2), and tables (Fig. 2 B1, B2) with a reduced disc, but bearing a characteristic maltese cross. Calcareous ring consists of 5 large radials and 5 short interradials.



Ecological studies

Habitat

Holothuria cinerascens were collected from the rocks of Thirumullavaram at a depth of 5m. They occurring gregariously on the rock surface and usually get exposed during low tide. They remain firmly attached to the rocks with pedicels. They were found to be searching food with this extended tentacles.



Figure 1. Holothuria pardalis



Figure 2. Holothuria cinerascens

Holothuria pardalis were found among gravel rich rocks on Thirumullavaram with algal coating. They were found with their extended podia on the dorsal side. They were few in number and seen active in feeding with peltate tentacles.

Table 1. Eco- physical parameters of the study area (February -June 2014)

Parameters

February

March

April

May

June

Temperature (0C)

29

29.5

30

28

22

pH

7.4

7.6

7.8

7.2

7

DO (mg/l)

4

4.6

4.7

5.35

6

Salinity( ppt)

34

34.5

34

32

31.2

TDS

81

80

84

90

94

Among the ecological parameters studied temperature, salinity, and total dissolved solids showed wide variation where as pH, dissolved oxygen show comparatively less variation. Temperature has a major influence on growth and physiology. Water temperature also plays a fundamental role in the biological activities of sea cucumbers. The high temperature noticed during pre-monsoon period may be due to solar radiation and low temperature during the starting of monsoon (June) may be due to heavy rain. The present results are in conformity with the earlier findings of Suresh et al. (1978), Divakaran et al. (1980) and Rani et al. (1981). The pH values ranged between 7 and 7.8 in the present investigation. The high value of pH during pre-monsoon may be due to the uptake of CO2 by photosynthesizing organisms mainly phytoplanktons. This view was supported earlier by Raman & Prakash (1989). Low pH values noticed during the monsoon periods found to be associated with low salinity values as a result of dilution of surface water by heavy precipitation and land drainage. This result is in conformity with the reports of Anbazhagan (1988).

Dissolved oxygen content plays a role in controlling the metabolic processes of living organisms. Low oxygen values during pre-monsoon might be due to low solubility as the salinity was high. The same effect of salinity on dissolved oxygen concentrations was confirmed by the earlier observations of Shibu (1991) and Neena (1999). Though salinity in the marine environment does not fluctuate considerably, a slight change in salinity will reflect on the physical, chemical and biological factors; Goswami & Singhal (1974). The maximum value of salinity obtained during pre-monsoon period in the present study may be due to favorable conditions for increased evaporation. Low salinity values during post-monsoon period may be due to the fresh water flow and low evaporation (Pati 1980). The maximum value for total dissolved solids was obtained during monsoon period and low value obtained during pre-monsoon period. This may be explained as a result of added nutrients through land drainage during monsoon period. This result agrees with the findings of Mrutyujaya et al. (1994).

Conclusion

The present study shows that Thirumullavaram rocky belt is an ideal habitat for sea cucumbers. Two species of sea cucumbers were collected and identified as Holothuria cinerascens and Holothuria pardalis. Sea cucumbers by their deposit, detritus feeding behavior play very significant role in ecological sustainability by nutrient recycling and mixing of oxygen. The ecological parameters in the habitat of sea cucumbers observed, showed that there exist monthly variation in certain parameters like salinity, temperature, dissolved oxygen and total dissolved solids.



Acknowledgements

The authors thank the Principal, M.S.M. College, Kayamkulam, Kerala, India for encouragement and providing facilities for the study. The authors are grateful to the University Grants Commission (UGC), India for funding the project (MRP(S)-1396/11-12/KLKE011/ UGC-SWRO)



Reference

Anbazhagan P. 1988. Hydrobiology and benthic ecology of Kodaikkarai coastal and sanctuary (south-east coast of India). Ph.d Thesis, Annamalai University, 208.pp.

APHA 2007. Standard methods for the examination of water and waste water American Public Healh Association, 21 st ed-Washington DC P.948.

Clark AM, Rowe FWE. 1971. Monograph of the shallow water Indo- West Pacific echinoderms. Trusties of the British Museum (Nat.Hist.) London: 250, 12pls.

Conad C. 1997. Asexual reproduction by fission in Holothuria atra. Variability of some parameters in population from the tropical Indo Pacific. Oceanologica Acta 19 (3-4) 209-216.

Conad M. Byrne. 1993. A review of recent developments in the world sea cucumber fisheries. Mar. Fish. Rev., 55(4): 3-13.

Divakaran O, Arunachalam M, Nair NB, Padmanabhan KG. 1980. Studies on the zooplankton of Vizhinjam inshore water, south west coast of India. Mahasagar, Bull. Nat. Inst. Oceanogr.13 (4): 335-341.

Goswmi SC, Singal SYS. 1974. Ecology of Mandovi and Zuari estuaries: Plankton community in relation to hydrographic conditions during monsoon months. Indian J. Mar. Sci., 3:51-57.

Mrutynjaya Rao I, Vishnu Murty M, Satyanarayanan D. 1994. Nutrient relationships in the seaweeds of Visakapatnam, east coast of India. Ind. J. Mar. Sci., 23:43-46.

Neena Suzzan Joshua. 1999. Screening, isolation and Characterization of Bioactive compounds from Marine Organisms. Ph.d Thesis in Aq. Biol and Fisheries Uty. Of Kerala.

Pati S. 1980. Observations on the hydrography and inshore plankton of the Bay of Bengal off Balasore. Hydrobiologia 70: 123-132.

Raman AV, Prakash PK. 1989. Phytoplankton in relation to pollution in Visakhapatnam harbor, east coast of India, Ind. J. Mar. Sci., 18:33-36.

Rani MJK, Ramachandran Nair R, Vasanthakumar R. 1981. Zooplankton in the inshore waters of Vizhinjam, Trivandrum, J. Mar. Biol. Ass. India., 23 (183):62-76.

Roberts. D. 2000. Classification and the holothurian tentacle. In Proceedings of the International Echinoderm Conference. Tampa Bay. (ed)J.M. Lawerence. A.A Balkemma. Rotterdam.pp. 117-122.

Shibu S. 1991. Ecology of the Paravur Lake. Ph.D. Thesis, University of Kerala.

Suresh K, Reddy MPM, Kurian NP. 1978. Hydrographical features of nearshore water along Mangalore coast. Ind. J. Mar. Sci., 7:141-145.



База данных защищена авторским правом ©shkola.of.by 2016
звярнуцца да адміністрацыі

    Галоўная старонка