Pakistan Journal of Marine Sciences, Vol. 19(1&2), 1-5, 2010. FIRST SCANNING ELECTRON MICROSCOPIC REPORT OF CHAETOCEROS PSEUDOCURVISETUS (BACILLARIOPHY- CEAE) ISOLATED FROM NORTH ARABIAN SEA DURING TASMAN SPIRIT OIL SPILL Asma Tabassum, Hina S. Baig and Aliya Rehman Department of Botany, University of Karachi, Karachi-Pakistan (AT); National Institute of Oceanography, Karachi-Pakistan (HSB); Department of Botany, University of Karachi, Karachi-Pakistan (AR). ABSTRACT: Present study is the first detailed taxonomic report of Chaetoceros pseudocurvisetus from North Arabian Sea bordering Pakistan especially during Tasman oil spill accident. Valve profile with SEM image has been provided. KEY WORDS: Planktonic, marine, diatom, Arabian Sea. INTRODUCTION A marine planktonic diatom Chaetoceros was first erected by Ehrenberg in 1844 (Rines, 1999). It is the most widest and diversified genus among marine planktonic diatom (Cupp, 1943). It is comprised of more than 400 species (Hasle and Syvertsen, 1997). Genus Chaetoceros is characterized by mainly chain formation and very few exist as solitary form (Sunesen, Hernandez-Becerril and Sar, 2008). About 24 taxa of Chaetoceros were previously recorded from North Arabian Sea (Moazzam, 1973; Hina et al., 1995; Hina and Rabbani, 1995; Hina, 2007; Hina et al., 2007; Hina et al., 2007; Tabassum and Saifullah, 2010). All reports were based on light microscopic illustrations. This study describes first record from the study area along with scanning electron microscopic description of Chaetoceros pseudocurvisetus. Present paper will fill the lacuna of detailed taxonomic structure of a very important fraction of centric diatom community structure. MATERIALS AND METHODS A total of 5 phytoplankton samples were collected after Tasman spirit oil spill (Map). Light and scanning microscopy were carried out. For exclusive scanning electron microscopic studies, samples were handled using cold H 2 O 2 method (Karthick et al., 2010). Drops of treated samples were then coated with gold targets. Scanned images were taken from coated samples by using JEOL # JSM 6380 A. Observation: Chaetoceros pseudocurvisetus Mangin (Figs. 1 & 2) References: Cupp, 1943, p. 138, Fig. 94; Hendey, 1964, p. 134, Plate 18, Fig. 1; Hasle and Syvertsen, 1997, p. 211, Plate 44; Shevchenko et al., 2006, p. 251, Figs. 107-109 (253).
2 Pakistan Journal of Marine Sciences, Vol. 19(1&2), 2010. Fig. 1 Map showing affected area of Clifton indicating sampling stations (1 to 5) after TSOS Map showing affected area of Clifton indicating sampling stations (1 to 5) after TSOS. Diagnosis: Curved chains with rectangular and concave valves, apertures lanceolate connected by poles; mantle concave, small slit in centre; setae with short or no basal part, directing outwards Chains, curved setae raised along the same side of chain. Cells joined by fusion of sibling setae and at the edges of valves by four elevated projections (arrows). Morphometric data: Apical axis: 20 μm Foramina: 12 μm Local Distribution: Chaetoceros pseudocurvisetus was commonly found at station 2 (Table 1) of Tasman Spirit Oil Spill. General Distribution: Cupp, 1943, West Coast of North America; Hendey, 1964, British Coastal Waters, Shevchenko et al., 2006, Peter the Great Bay, Sea of Japan.
Tabassum et al: First SEM report of Chaetoceros pseudocurvisetus 3 Fig. 1. SEM of Chaetoceros pseudocurvisetus showing elevated projections (arrows). Fig. 2. Chain of Chaetoceros pseudocurvisetus under light microscopy.
4 Pakistan Journal of Marine Sciences, Vol. 19(1&2), 2010. Table 1. Occurrence of Chaetoceros pseudocurvisetus. Station Species 1 2 3 4 5 Chaetoceros pseudocurvisetus - + - - - Table 2. Comparision of morphometric data of Chaetoceros pseudocurvisetus among earlier and present study Cupp, 1943 (Pacific Hasle Syvertsen, & Shevchinko et al., 2006 Ocean) 1997 (Sea of Hendey, 1964 (British Coastal Water) Japan) Present study (North Arabian Sea) Apical axis 13µm - 19µm 15µm - 40µm 12µm - 50µm 15µm - 35µm 20µm Foramina - - - - 12µm DISCUSSION Chaetoceros pseudocurvisetus was identified from the study area after Tasman spirit oil spill. Scanning electron micrograph of the specimen was studied in detail. The chain of this species is curved and all the setae are oriented to the same side of the chain. There are other two species that share this feature C. debilis and C. curvisetus but in this case it is pseudocurvisetus because cells in chains are joined by fusion of sibling setae and at the edges of valves by four elevated projections (arrows) (Fig. 1). Moreover, present study reveals the fact that species was very rare and observed only in one station (Table 1). Morphometric data agreed with the previous reports of other workers from respective area of study (Table 2). This species was predominantly present in cold winter-spring season where as was found in low abundance in summer (Shevchinko et al., 2006). REFERENCES Cupp, E.E. 1943. Marine Plankton diatoms of the West Coast of North America, Bull Scripps Inst. Oceanogr., 5: 1-238. Hasle, G. R. & E. E. Syvertsen. 1997. Marine Diatoms (5-386). In: Identifying Marine Phytoplankton. (Ed): C. R. Tomas. Academic Press, San Diego, California, pp.1-385. Hendey, N. Ingram. 1964. An introductory account of the smaller algae of British coastal waters. Part 5: Bacillariophyceae (Diatoms). In Ministry of Agriculture, Fisheries and Food. Fishery Investigations series IV, HMSO, London, pp.317. Hina S. Baig, N. Khan & Rizvi, S.H.N. 1995. Distribution of Chlorophyll a and Phytoplankton along the Karachi Coast. Pro. Of Pak. US Conf. edit. By Thompson & Tirmizi, 509-517.
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