Int. J. Biol. Res., 2(2): 143-146, 2014.

POPULATION DENSITY OF AND ACMAEA (: ) AT VARIOUS TIDAL ZONES ON THE ROCKY COAST OF MANORA, KARACHI, PAKISTAN

Muhammad Humayun Atta1*, Adnan Mujahid2 and Furqana Chaghtai1

1Centre of Excellence in Marine Biology, University of Karachi, Karachi-75270, Pakistan. 2M.A.H. Qadri Biological Research Center, University of Karachi, Pakistan *Corresponding author e-mail: [email protected]

ABSTRACT

The Cellana and Acmaea are well known gastropods of the rocky intertidal zones of Manora, Karachi coast. They are conspicuous at each tidal zone along with dense algal mats. Their maximum population density was recorded in the mid-tidal zone. Yearlong field studies of these limpets for twelve consecutive months displayed higher population density for Cellana as compared to Acmaea. The maximum average population density per m2 of Cellana was recorded to be 43 in September in the mid-tidal zone. Average maximum density per m2 of Acmaea was noted to be 17 in mid-tidal zone in January. The minimum density was recorded to be 7 for these in the month of February in high tidal zone.

Keywords: Inter-tidal zone, Mid-tidal zone, Population density, Manora (Karachi), Cellana and Acmaea.

INTRODUCTION

Limpets constitute a conspicuous and well known group of the gastropod molluscs which are worldwide in distribution. They can be used as best contender for environmental monitoring (Davies et al., 2005). The storms and desiccation may direct their occurrence over the coast. The limpets also play important role in the ecosystem, being herbivores (Humayun and Chaghtai, 2012) at both temperate and tropical latitudes (Liu, 1994; Dunmore and Schiel, 2000). The population dynamics of various limpets has been studied in various parts of the world (Lewis and Bowman, 1975; Thompson, 1980; Fletcher, 1987; Bosman and Hockey, 1988; Misra and Kundu, 2005). The population dynamics and growth of limpets have been reported to vary among different habitats (Thompson, 1980; Creese, 1980; Bosman and Hockey, 1988). Factors which influence the population structure of limpets include associations with some other species (Johnson et al., 1997), discharge of the sewage waste (Hindell and Quinn, 2000), density (Boaventura et al., 2002) and predation (Lewis and Bowman, 1975). Marine intertidal organisms, like limpets have to cope with severe environmental conditions during low tide period associated with thermal and desiccation stresses (Christopher, 2003). The selection of particular habitats like pits, crevices, cracks play a vital role in reduction of thermal and other physical stresses. These places are cooler, more humid, and support more micro algae and provide them more shelter from water flow than open areas. Topographic features of the environment and distribution of organisms are thought to be directly related with each other. Crevices are often conspicuous feature of the rocky coasts which are cooler and humid. However, other factors such as seasons, height on the shore and tidal conditions also seem to alter the conditions. Population density of limpets remains relatively uniform on various sizes of the rocks. The results of studies of 1500km coastline of South African coast showed that no significant difference of population densities was found on larger and smaller rock patches (Victoria et al., 2012). In Pakistan, mollusks have been a subject of investigations by many researchers like (Tirmizi and Zehra, 1982, Moazzam and Rizvi, 1983; Zehra and Parveen, 1991; Ahmad and Siddique, 1997; Shamim, 2001; Afser, 2009; Bano, 2009; Humayun and Chaghtai, 2012; Atta et al., 2013) on different aspects of mollusks but Population density of these two coexisting limpets (Cellana and Acmaea) at the commercially and biologically important on rocky shore of Manora which is still un-described. The study of population density of limpets over such populated coast like Manora is undertaken which is the first of its type and hopefully will help us in future to compare their densities in other rocky coasts of Pakistan.

MATERIALS AND METHODS

The aim of present work was to ascertain the population density of the two limpets (Cellana and Acmaea) inhabiting rocky shore of Manora (240. 48, 670 5E) of the Karachi coast .These study area is located along Northern Arabian Sea (Fig. 1). Observations were made in the field from January 2008 to December 2008 by the establishment of quadrates in the intertidal zone of Manora. The quadrates of 1 m2 each were placed at an interval of about 5m apart from each other (Fig. 2). These were established in low, mid and high tidal zones. The site was visited twice in a month. For sampling a fixed route was followed throughout the study period and samples were collected from low to high tidal zone. Sampling was done by hand picking. Limpets were identified according to Khan and Dastagir (1971) and Tirmizi and Zehra (1982). 144 Muhammad Humayun Atta et al.,

Fig. 1. Cellana and Acmaea in their natural habitat. Fig. 2. A quadrate placed in the study area of Manora.

RESULTS

The population of both organisms varied in low-, mid and high tidal zones significantly (Fig, 3) as given by the ANOVA (Table 1). Both limpets showed higher density on the clear rocks of the coast whereas lesser density over rocks with dense algal encrustation. Maximum average population density of Cellana per m2 was recorded to be 43 in September in the mid-tidal zone and minimum density per m2 was noted to be 7 in high-tidal zone in the month of February. Average maximum density of Acmaea was noted to be 17 in mid-tidal zone in January and minimum density was recorded to be 7 in the February in high tidal zone. The comparative study of Cellana and Acmaea revealed that both species possess maximum densities at the mid- tidal zones (MTZ). The density of Cellana was greater than Acmaea in this zone. Both species exhibited minimum densities in the high-tidal zone (Fig. 3). The maximum total zonal population density was recorded in September to be 620 individual for the Cellana and 240 animals were recorded for the Acmaea. In intertidal area the lowest density of Cellana at Manora was 360 and 150 individual for Acmaea in the month of October.

DISCUSSION

Cellana sp. and Acmaea sp. are the commonest limpets of the rocky shores of Manora (Karachi), Pakistan coast. The studies which are carried out in different parts of the world have shown that these two limpets prefer to dwell over clean and clear rocks which are devoid of dense growth of any of seaweeds (Rao and Ganapati, 1971; Dunmore and Schiel, 2003) . They are also visible over the rough rock surfaces. They are also found in crevices and tide pools. The limpets residential preferences match with the topographic conditions of Manora where bare rocks and less dense growth of algae over the rock was observed. So, reasonable population density of Cellana and Acmaea was observed in such rocky habitats. Moreover, they are abundant in crevices which are humid cooler places and promote more micro algal growth (Jackson, 2010), where desiccation stress is low which also prevents them from heat in summer and ultimately decreases their mortality (Liu, 1994). Moreover plenty of micro algal food is in easy access of the species which could be the major factor for high population density of limpets in much habitat. Monthly monitoring of these limpets at Manora showed that both Acmaea and Cellana are in abundance in the mid-tidal zone as compared to the low and high-tidal zones. Similar results are also documented by the Brazilian investigators (Marcelo Tanaka et al., 2002) and Kiwi researchers (Dunmore and Schiel, 2003).

Table 1. One-way ANOVA: Density per m2 of Cellana versus intertidal Zones at Manora. Source df SS MS F P Zones 2 22354 11177 42.16 0.000 Error 249 66013 265 Total 251 88367 One-way ANOVA: Density per m2 of Acmaea versus intertidal Zones at Manora Source df SS MS F P Zones 2 5832.2 2916.1 78.75 0.000 Error 249 9220.8 37.0 Total 251 15053.0 Population density of Cellana and Acmaea at rocky coast of Manora 145

60 Cellana sp. LTZ MTZ HTZ

50

40

30

Population density 20

10

0 Jan Feb Mar Apr May Jun Jul Aug Sep O ct Nov Dec Months

25 Acmaea sp. LTZ MTZ HTZ

20

15

10

Population density

5

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Months

Fig. 3. Population density per m2 of Cellana sp. and Acmaea sp. in a costal rocky outcrop of Manora, Karachi. LTZ, Low tidal zone; MTZ, mid tidal zone and HTZ, High tidal zone.

REFERENCES

Afser, N. (2009). Study of some imposex Gastropods species from the polluted marine waters along the coast of Karachi. Ph.D. Thesis. 239 Pp. University of Karachi, Karachi, Pakistan. Ahmed, M. and G. Siddique. (1997). Histology of gonads and cephalic brood pouch of the marine gastropod Planaxis sulcatus of Karachi coast. Hydrobiologia, 350: 127-130. Atta, H.M, A. Mujahid and F. Chaghtai. (2013). Movement of common rock clinger limpet, Cellana sp., on the rocky shore of Manora, Karachi, Pakistan. Bano, A. (2009). Distribution, Abundance and reproductive biology of siphonarid limpets (Gastropoda: Pulmonata) occurring on the two rocky shores of Karachi, Pakistan. Ph.D. Thesis. University of Karachi, Pakistan. pp. 201. Boasman, A.L. and P.A.R. Hockey. (1988). Life history patterns of populations of limpet granularis: the dominant roles of food supply and mortality rate. Oecologia, 75: 412-419. Boaventura, D., L. Cancela da Fonseca and S. Hawkins. (2002). Analysis of competitive interactions between the limpets Patella depressa Pennant and Patella vulgata L., on the northern coast of Portugal. Journal of Experimental Marine Biology and Ecology, 271: 171-188. Christopher, D.G. Harley and Brain S.T. Helmut. (2003). Local and regional-scale effects of wave exposure, thermal stress, and absolute versus effective shore level on patterns of intertidal zonation: Limnology and Oceanography, Vol .48 Pp.1498-1508. Creese, R.G. (1980). Analyses of distribution and abundance of populations of the high shore limpet, Notoacmaea petterdi .Oecologia, 45: 252-260. Cellana sp.

146 Muhammad Humayun Atta et al., 60

50 Davies, M.S., D. Proudlock and A. Mistry. (2005). Metal concentration in the radula of the common limpet, Patella vulgata L., from 10 sites in the U.K. Journal of Ecotoxicology, 14: Pp. 465-475. Dunmore, R.A. and D.R. Schiel. (2003). Demography, competitive interactions and grazing effects of intertidal limpets in southern 40 .New Zealand. Journal Marine and Freshwater Research, 37: 171-182. Fletcher, W.J. (1987). Life history dynamics of the limpet Patelloida alticostata in intertidal and sub tidal environments. Marine Ecology Progress Series, 39: 115-127. 30 Hindell, J.S. and G.P. Quinn. (2000). Effects of sewage effluent on the population structure of Brachidonetsrostratus (Mytilidae) on a temperate intertidal rocky shore. Marine and Freshwater Research, 51: 543-551. Humayun, M.A. and F. Chaghtai. (2012). Micro and Macro algal gut content assessment of two limpet species from Buleji and

Population density Population 20 Manora, the rocky coasts of Karachi, Pakistan. Int. J. Bio. Biotech., 9(1-2): 75-79. Jackson, A.C. (2010). Effects of topography on environment: Journal of Marine Biological Association of U.K, 90: 169-192 Cambridge University Press. 10 Johnson, M.P., M.T. Burrows, R.G. Hartnoll and S.J. Hawkins. (1997). Spatial structure on moderately exposed rocky shore: Patch scales and the interaction between limpets and algae. Marine ecology Progress Series, 160: 209-215. Khan, M.D. and S.H. Dastagir. (1971). On the Mollusca: Gastropoda fauna of Pakistan. Records of the Zoological Survey, Pakistan. 0 Lewis, J.R. and R.S. Bowman. (1975). Local habitat-induced variations in the population dynamics of Patella vulgata L. Journal of Jan ExperimentalFeb Mar MarineApr BiologyMay andJun EcologyJul, 17: 165Aug-203.Sep Oct Nov Dec Liu, J.H. (1994). The ecology of Hong MonthsKong limpet and Patelloida pygmaea: Distribution and population dynamics. Journal of Molluscan Studies, 60: 55-67. Marcelo-Tanaka, Tiago E.M. DuqueLTZ-EstradaandMTZ CláudiaHTZ A. Magalhães. 2002. Dynamics of Acmaeid limpet Collisella subrugosa and vertical distribution of size and abundance along a wave exposure gradient. Journal of Molluscan Studies, 68: 55-64. Misra, S. and R. Kundu. (2005). Seasonal variations in population dynamics of key intertidal mollusks at two contrasting locations. Aquatic Ecology, 39: 315-324. Moazzam, M. and N. Rizvi. (1983). Settlement of oyster Larvae in Pakistani waters and its possible implication for setting up oyster culture. Proceedings: Symposium. Coastal Aquaculture, 2: 467-474. Rao, M. and P. Ganapati. (1971). Ecological studies on a tropical limpet structural variatioin shell in relation to the distribution. Marine Biology, 9: 109-114. Shamim, S. (2001). Studies on Distribution and reproduction Ecology of Onchidium verruculatum (Cuvier) (Mollusca : Gastropoda : Pulmonata) M.Phil thesis submitted to CEMB University of Karachi Pakistan, Pakistan. Pp 72. Thompson, G.B. (1980). Distribution and population dynamics of the limpet Patella vulgata L. in Ban try Bay. Journal of Experimental Marine Biology and Ecology, 45: 173-217. Tirmizi, N.M. and I. Zehra. (1982). Illustrated key to Families of Pakistani Marine Molluscs Pp. 46. Pakistan Science Foundation Islamabad. Victoria J. Cole Mail, Linda G. Johnson and D.M. Christopher. (2012). Effects of Patch-Size on Populations of Intertidal Limpets, Siphonaria sp., in a Linear LandscapePLOS/One December 20: 2012 Zehra, I. and R. Parveen. (1991). Studies on the breeding season, egg capsule and early Larval Development of Thellostyla albicilla (Linne, 1758) from Karachi coast Pakistan. Journal of Zoology, 23(1): 35-38.

(Received April 2014; Accepted November 2014)