ISSN: Res. Environ. Life Sci. 5(4) (2012)

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1 2012 RELS Impact of global warming and climate change on diversity: ISSN: The challenge of conservation of flora and fauna Res. Environ. Life Sci. 5(4) (2012) Structural organization of the epithelia lips and associated structures of fish, Pterophyllum scalrae: a histochemical investigation J.P.N. Singh 1 *, Sateesh Chandra Dubey 1 and Archana Singh 2 1 Department of Zoology, R.H.S.P.G.College Singramau, Jaunpur ; 2 Department of Zoology, T.D.College Jaunpur * drjpnsingh@gmail.com (Received: March 15, 2012; Revised received: November 01, 2012; Accepted: November 08, 2012) Abstract: Structural organization of the epithelium of the lips and associated structures of Pterophyllum scalrae is described. The upper lip is associated on its dorsal side with a membranous fold of skin and the rostral cap while the lower lip is associated on its ventral side with a fold of skin between lower lip and ventral head skin. The chemical composition of the mucous cells may be correlated with habit, habitat and feeding behaviour of pterophyllum scalrae. Elaboration of sulphated glycoprotein moieties by most of the mucous cells in different regions of the lips and associated structures may be correlated to increase viscosity of the mucus and lubrication of the surface of epithelia of lips and associated structures. This could play a vital role in providing protection to the lips and associated structures against mechanical damage to which these fishes are exposed during feeding the plant materials. Presence of both acidic and neutral glycoprotein in the mucous cells of skin folds are quite significant. Sulphated acidic glycoprotein provides extra lubrication to the surface of the fold of skin. This reduces the surface drag during their stretching enabling the jaw to protrude at the time of feeding with increasing efficiency and swiftness. Taste buds on dorsal side of upper lip of Pterophyllum scalar are prominently elevated being located on epithelial protrusion projected well above the surface may enhance the ability of the fish to sense the chemical nature of the surrounding water and food available in a particular feeding zone. Generally taste buds are absent in skin folds of Pterophyllum scalrae. Here taste buds are not necessitated or may not be of much significant value probably because the fold of skin lies in deep grooves and do not remain in direct contact with the surrounding medium except when they are temporarily stretched out for short periods during jaw protrusion for feeding. Uninucleated club cells are observed in the lips and associated structures of Pterophyllum scalrae. Information regarding functional significance of club cells is available mainly from the studies on epidermis covering general body surface of the fish. It appears that club cells are developed additionally to complement the mucous cells in the efficient functioning of the epithelium in the protection against various hazards. Presence of lymphocytes in epithelia of lips and associated structures of Pterophyllum scalrae may be associated with local defence mechanism. Key words: Pterophyllum scalrae, Lips, Glycoproteins, mucous cells Introduction Lips are evolved as modified structures of skin that border the dorsal, ventral and lateral margins of the mouth. Studies on the epithelia of the lips and associated structures in fishes, that show characteristic modification with respect to their food and feeding habits are limited and have not attracted the attention of researchers from the stand point of their structural organization and histochemistry. Agrawal and Mittal (1991) reviewed the literature and described the structural organization of epithelia of the lips and associated structures of an Indian major carp Catla catla. Agrawal and Mittal (1992, a,b,c) described the structure and histochemistry of the lips and associated structures of the fishes Rita rita, Labeo rohita and Cirrhina mrigala respectively. Pinky et al. (2002) studied the lips and associated structures in Garra lamta through scanning electron microscope. Pinky et al. (2004) observed the Kerainization in the lips and associated structure of a hill stream fish Garra lamta. Singh and Gupta (2006 a,b) studied the structure and histochemistry of lips and associated structures of the fishes Chanda ranga and Oxygaster bacaila respectively. Singh et al. (2009) gave an account of structure and histochemistry of lips and associated structures in Aspidoparia morar. Tripathi and Mittal (2010) described the Keratinization in lips and associated structures of a fresh water fish, Puntius sophore in relation to its feeding ecology. The aim of present investigation has been to study the structural organization and histochemistry of epithelia of lips and associated structures of Pterophyllum scalrae an omnivorous surface feeder fish. It belongs to the family chaetodontidae, sub order Percoidei and order perciformes. It prefers slow moving and still water bodies heavily planted with strap leaved plants such as Valisneria and Echinodorus. Materials and Methods Live specimens of Pterophyllum scalrae cm in length were purchased from Sibaco fish emporium, Jaunpur, were kept in the laboratory and fed on dried prawn powder. The upper and lower lips were excised along with structures associated with them and fixed in 10% neutral formalin and aqueous Bouins fluid, paraffin embedded sections were cut at 5 µm and were stained with Ehrlich s haematoxylineosin (HE), Verhoeff s haematoxylin eosin (VHE), papaniclaou s stain (PS), Mallory s triple stain (MTS) and with the meathods to locate and differentiate protein and carbohydrate contents in the cellular components following Lillie (1954), Gurr (1958), Bancroft and Stevens (1982) and Pearse (1985). Results In Pterophyllum scalrae the mouth is terminal bordered by thin and movable lips. The upper lip is associated with a conscipicuous rostral cap and the fold of skin between the upper lip and rostral cap. The lower lip is associated with the fold of skin between the lower lip and the ventral head skin (Plate I a) Structural Organization: The histochemical investigations have shown that, the epithelia of the lips and structures associated with them exhibit a significant diversity in the distribution and histochemical nature of their cellular components. Upper lip: The dorsal side epithelium of upper lip differs from that of ventral side. Epithelium on the dorsal side of upper lip: The free surface of the dorsal side of upper lip is smooth. It consists mainly epithelial cells, mucous cells, club cells, lymphocytes and taste buds. The superficial layer epithelial cells appear polygonal, often being flattened or some what rectangular (Plate I b,). The middle layer epithelial cells are Research in Environment and Life Sciences 195 Special Issue Editor: Dr. J.P.N. Singh

2 Table-1: A Summary of the histochemical reactions showing carbohydrate and proteins moieties in cellular components in the epithelia of the lips and associated structures of Pterophyllum scalrae Histochemicsl techniques Epithelial cells Mucous Cells Club cells Lymphocytes Supeficial Layer Middle & Basal Layer No treatment/schiff Periodic acid/schiff (PAS) + M + M + M + M - Acetylation/PAS Deacetylation/PAS + M + M + M + M - Diastase/PAS Alcian Blue (AB)/pH 2.5 +GBL +GBL +GBL +GBL - High Temp. methylation/ab ph High Temp. methylation/ Saponification/AB ph 2.5 +GBL +GBL ++GBL +GBL - Mild methylation/ab ph 2.5 +GBL +GBL ++GBL +GBL - Alcian blue ph 1.0 +GBL +GBL +GBL +GBL - Alcian blue ph 2.5/PAS +PUR +PUR +PUR +PUR - Mercury bromophenol blue ++BL ++BL ++BL +BL ++BL Acid solochrome cyanine-r + R + R - + R - Ninhydrin/Schiff + PUR + PUR - + PUR - Deamination/ninhydrin/Schiff Dimenthyl aminobenzaldehyde (DMAB) nitrate +PUR - +PUR +PUR - Iodination/DMAB-nitrate +BL - +BL +BL - Iodination/Million reaction - - Perfomic acid/alcian blue (PFA/AB) Dihydroxy dinaphthyl disulphide (DDD) Million reaction R - Sakaguchi Reaction Phenylglyoxal/Sakaguchi reaction Feulgen reaction ++M + M + M + M ++M Symbols: - negative; +weak; ; +, moderate; ++, strong; +++, very strong; BL, blue GBL, greenish blue; M, magenta; PUR, purple; ; in peripheries R, Red arranged in several layers. They often appear vertically elongated or some what spherical in the deeper layers and gradually acquire a polygonal or vertically compressed shape towards the surface (Plate Ib). The basal layer epithelial cells are arranged in a single layer on a thin non-cellular basement membrane (Plate Ib). The nuclei of the epithelial cells, in general, are centrally placed, being elongated or flattened and have distinct chromatin material and nucleoli. They stain moderately blue with HE (Plate I b), PS and blue black with VHE. Lymphocytes in the basal layer are enclosed in lymphatic spaces. The flask shaped mucous cells are restricted mainly to the superficial layer of the epithelium and void their secretions on the surface through narrow pores (Plate Ic). The club cells are generally observed in the dorsal side of upper lip. The taste buds are located in the dorsal side of upper lip projected well above the general surface of epithelium. They may be one or two supported by papillae like projections from the underlying connective tissues. (Plate-I b). Ventral side of Upper lip: The free surface of the ventral side of the upper lip is also smooth.the epithelial cells in the basal layer are cuboidal and in remaining layers are polygonal (Plate Id). The superficial layer epithelial cells at interval exfoliate at the surface. The nuclei of the exfoliating epithelial cells, in contrast, appear small, rounded with indistinct compact chomatin material and nucleoli. (Plate-Id). Lymphocytes are generally not obsreved. The superficial layer epithelial cells along with the mucous cells are found detached from the epithelium.the mucous cells are generally round in shape and restricted mainly in the surface layer and underlying middle layer (Plate Ie). Club cells are not discernible in the epithelium. Taste buds are also not observed. Research in Environment and Life Sciences 196 Lower lip - Dorsal side of the lower lip: The free surface of the dorsal side of lower lip is more or less smooth. The epithelial cells resemble in structural organization and histochemical characterization to epithelial cells of dorsal side of upper lip (Plate If,IIg). Mucous cells are flask shaped found in the superficial layer and underlying layer (Plate- IIa). Club cells smaller in size are infrequently seen in the middle layer of epithelium (Plate-If). Taste buds are also observed in the epithelium of dorsal side of lower lip located in deeper layer and are surrounded by concentric whorls of epithelial cells. Taste hairs are also seen (plate-if). Ventral Side of Lower Lip: The epithelium on the ventral side of the lower lip is quite thick (Plate-IIc) and the free surface is smooth. It is composed of multilayered epithelial cells, two to four layeres of rounded mucous cells situated between superficial layer and underlying layers of epithelial cells(plate IIc) and lymphocytes infiltrating the basal layer and deeper layer epithelial cells. The epithelial cells in surface layers are cuboidal equipped with dilated healthy nuclei with nucleolous (Plate- IIb). The epithelial cells in the middle layers are vertically elongated with healthy nuclei. The basal layer epithelial cells are columnar with centrally located nuclei. Club cells and taste buds are not observed. Skin Fold: The epithelium of both dorsal and ventral skin fold is devoid of taste buds and club cells. The basal layer epithelial cells are small and cuboidal with centrally located rounded nuclei (Plate-IId). Epithelial cells above the basal layer are polygonal with elongated nuclei. The epithelial cells in the superficial layer and middle layer are flattened. The mucous cells are flask shaped crowding in surface layers opening to the surface by minute pores forming a slimy mucous coat on the surface (Plate-IIe). The epithelium is relatively thinner than

3 a b c d e f Plate I (a)photograph of Pterophyllum scalrae.. Plate I (b) (c) : Photographs of the cross section of dorsal side of upper lip of Pterophyllum scalarae. (b)showing structural organization of the epithelium divided in to superficial layer epithelial cell (SEC), middle layer epithelial cells (MEC) and basal layer epithelial cells (BEC). Note basophilic mucous cells(mc) in surface layer, club cells(cc) with shrinked cytoplasm and typical taste bud (TB) with distinct cellular components (HE) X (c) Epithelium on the dorsal side of upper lip showing greenish blue flask shaped mucous cells (arrow) is surface layer and moderate purple rounded mucous cells (barred arrow) in deeper layers (AB/PAS) X 600. Plate I (d) (e): Microphotographs of the cross section of ventral side of upper lip of Pterophyllum scalrae.(d)showing structural organization of ventral side of upper lip divided in to superficial layer epitelial cell (SEC), middle layer (MEC) and basal layer epithelial cells (BEC). Note exfoliation(arrow) in superficial layer epithelial cells (HE) X (e) Showing greenish blue mucous cells (arrow), mucous cells with magenta colour reaction (barred arrow). Note moderate purple reaction in epithelial cell (EC) (AB/ PAS) X 600. (f) :Photomicrographs of the cross section of dorsal side of lower lip of Pterophyllum scalrae showing mucous ells (MC) club cells (CC) and epithelial cells (EC). Note taste bud (TB) with distinct cellular components (barred arrow) and eosinophilic taste hairs (arrow) (HE) X 1000 the lip epithelia.lymphocytes are more than other region of lips and associated structures. Rostrum: The epithelium of rostrum consisting, superficial layer, middle layer and basal layer epithelial cells. The club cells are mostly rounded in shape occupy in middle layer epithelial cells. The contents of these cells exhibit, variable degrees of shrinkage and vacuolization with various fixatives (Plate II f,g). Superficial layer epithelial cells are cuboidal. The basal layer epithelial cells are low columnar and middle layer epithelial cells are vertically elongated with distinct nuclei (Plate IIf). Mucous cells are rounded in shape and open to the surface by minute pores to void their secretions (Plate II g). Histochemistry: Epithelial Cells: Superficial layer epithelial cells in lips and associated strucutres appear homogenous and slightly eosinophilic in HE,PS and VHE (Plate-Ib,IId,IIf,If,), stain purplish in MTS and show moderate reaction to mixture of neutral and acidic glycoproteins (Plate-Ic,Ie,IIa) and strong reaction for general protein a weak reaction to basic protein and protein bound NH 2 groups (Table-1). The reaction for glycoproteins in relatively strong at the free margins of superficial layer epithelial cells (Plate-Ic,IIe). The epithelial cells in the middle layer and basal layer show relatively less intense reaction for glycoprotein and various protein end groups. Lymphocytes: Lymphocytes enclosed within characteristic lymphatic spaces are observed mainly between the basal layer and lower middle layer epithelial cells. The lymphocytes are rounded, oval or irregular in out line, each having an off-centered nucleus with dense, compact chromatin material, a nucleolus and thin rim of cytoplasm. The cytoplasm stains light blue in HE and PS. The nuclei stain deep blue in HE and PS and bluish black in VHE. In addition both the cytoplasm and the nuclei stain strongly for general protein (Table 1). Mucous Cells: The mucous cells from different locations appear light blue in HE (Plate-Ib,IIc,IIf,If,IIb), PS and unstained in VHE, and do not show a positive reaction to protein end groups. The peripheral cytoplasmic regions of these cells, however, show a moderate reaction to general protein. The mucous cells on dorsal side of the upper lip in the surface layers stain strongly for sulphated acidic and non sulphated acidic glycoproteins. The intensity of reaction in underlying rounded mucous cells is relatively stronger (Plate-Ic). On the ventral side of upper lip and dorsal side of lower lip (Plate-Ie,Ig) mucous cells show moderate reaction for acidic glycoproteins. The reaction is relatively Research in Environment and Life Sciences 197

4 a b c d e f g Plate II.(a) Photomicrographs of the cross section of dorsal side of lower lip of Pterophyllum scalrae showing distribution of mucous cells staining strong greenish blue (arrrow) for acidic glycoprotein and weak purple (barred arrow) for mixed glycoprotein. Also note strong reaction in epithelial cells (AB/PAS) X 600.(b) Photomicrographs of the cross section of ventral side of lower lip of Pterophyllum scalra showing basophilic mucous cells (MC) in surface layer and columnar cells with healthy nuclei in middle and underlying layer (arrow) (HE) X 1000.(c) Photomicrographs of the cross section of ventral side of lower lip of Pterophyllum scalarae Showing crowding of rounded mucous cells stained turquoise blue (arrow), weak blue (barred arrow) for acidic glycoprotein and weak purple (vibrated arrow) for mixed glycoprotein. Note epithelial cells (EC) stained dark purple. Also note PAS postitive basement membrane (BM) (AB/PAS) X 600.Plate II (d) (e) : Photomicrographs of the cross section of skin fold between upper lip and rostral cap (d) and fold of skin between lower lip and ventral head skin (e) of pterophyllum scalarae(d)showing greenish blue stained mucous cell (arrow) for acidic glycoprotein and weak purple reaction (barred arrow) for mixed glycoprotein. Note moderate purple reaction in epithelial cells (EC) (AB/PAS) X 600. (e)showing irregular shaped mucous cells staining strongly greenish blue (arrow) in surface layer, slimy mucous coat on the surface (Vibrated arrow) and moderate purple rounded mucous cells (barred arrow) in between middle and basal layer (AB/PAS) X Plate II (f) (g) : Photomicrographs of the cross section of rostral cap of pterophyllum scalarae.(f)showing distribution of basophilic mucous cells (MC) and eosinophilic club cells (CC) with shrinked cytoplasmic contents (HE) X 600.(g)Showing distribution of mucous cells in the epithelium strongly stains for acidic glycoprotein (arrow) and weakly stain for mixed glycoprotein (barred arrow). Note basement membrane (BM) (AB/PAS) X 600. weak in the peripheries of these cells. Oozing of glycoprotein moieties from these cells in intercellular spaces of epithelial cells is observed (Plate-IIe,IIa), Table1). The mucous cells on the ventral side of the lower lip display very strong reaction for sulphated acidic glycoprotein, moderate reaction for non-sulphated acidic glycoprotein (Table 1). Some cells also show moderate reaction for mixed glycoprotein moieites (Plate-IIc). The mucous cells in the epithelia of rostrum (Plate-IIe) and the fold of skin between upper lip and the rostrum and between the lower lip and the skin on the ventral side of the head(plate-iie) show strong reactions for sulphated acidic and non sulphated acidic glycoprotein (Table-1). Club Cells: Club cells are oval, rounded or elongated. Like those in the epidermis covering the general body surface of the fish (Singh and Mittal, 1990), each of them has a single, rounded, centrally placed healthy appearing nucleus, which stains moderately blue in HE, PS (Plate-Ib,IId) and bluish black in VHE. The contents of these cells exhibit variable degree of shrinkage with various fixatives. They appear homogenous and pink with HE, PS and VHE. A narrow perinuclear zone however, remains unstained, They show strong reaction for general proteins, moderate reaction for basic protein, protein bound NH 2 groups and tyrosine. The peripheries of these cells show relatively weak reaction for protein end groups (Table-1). Taste Buds: The taste buds are pear shaped located mainly in the outer layers of the epithelium, often projecting at the surface (Plate- Ib,If). Mostly they are supported by papillae from the sub-epithelial tissue, through which they get their nerve and blood supply. The neuro epithelial cells and surrounding supporting cells are not differentiated from each other. They are eosinophilic and show moderate Research in Environment and Life Sciences 198

5 reaction for neutral glycoprotein and general protein and weak reactions for basic proteins, protein bound NH 2 groups, tyrosine and tryptophan. Discussion Pterophyllum scalarae is very popular tropical fresh water fish because of its unique shape and interesting personality Pterophyllum scalarae are curious about their environments and can become very territorial. Pterophyllum scalrae is an omnivorous surface feeder fish. It is aggressive eaters because of its aggressive feeding habit. Pterophyllum scalrae feed on many types of food including flakes, dried and live foods. It prefers slow moving and still water bodies heavily planted with strap leaved plants such as valesnaria and Echinodorus. The epithelia of lips and associated structures in Pterophyllum scalrae show significant modification in relation to the adaptation of the fish to their particular habit, habitat and feeding behaviour. In Pterophyllum scalrae all the regions of the lips and associated structures are heavily equipped with mucous cells secreting glycoprotein of different classes. The mucous cells of the rostral cap display reaction for acidic and mixed glycoprotein moieties. The mucous cells in the skin fold between upper lip and rostral cap stain mainly for acidic and mixed glycoprotein while in the skin fold between lower lip and ventral head skin consist a mixture of acidic and neutral glycoprotein moieties and their secretion on the surface of the epithelium is mainly acidic glycoprotein in nature. The chemical composition of the mucous cells may be correlated with habit, habitat and feeding behaviour of pterophyllum scalrae. Elaboration of sulphated glycoprotein moieties by most of the mucous cells in different regions of the lips and associated structures may be correlated to increase viscosity of the mucus and lubrication of the surface of epithelia of lips and associated structures. This could play a vital role in providing protection to the lips and associated structures against mechanical damage to which these fishes are exposed during feeding the plant materials. Presence of both acidic and neutral glycoprotein in the mucous cells of skin folds are quite significant. Sulphated acidic glycoprotein provides extra lubrication to the surface of the fold of skin. This reduces the surface drag during their stretching enabling the jaw to protrude at the time of feeding with increasing efficiency and swiftness. The skin folds are situated in grooves, where the possibility of deposition of foreign matter increases. Tibbetts (1997) has shown that neutral glycoproteins are less viscous than the acidic glycoproteins produced by the mucous cells in alimentary tract of Arrhamphus selerolepis Kreffti. Mittal etal. (2004) have also observed secretion of neutral glycoproteins by type C mucous cells in the epithelium on inner surface of operculum in Lepidochepalichthys guntea. Neutral glycoproteins being less viscous may be easily washed away along with deposited foreign matters in the grooves and thus prevents the deposition of foreign matters in the grooves. Mittal et al. (2009) also observed the mucous cells are associated with multiple functions particle entrapment, lubrication, passage of food and protect the epithelium from possible abrasion in the buccal cavity of Cirrhinus mrigala. Taste buds on dorsal side of upper lip of Pterophyllum scalar are prominently elevated being located on epithelial protrusion projected well above the surface. Pinky et al. (2002) have shown that the taste buds located on the elevation of the epithelial surface on rostral cap and adhesive pad of an Indian hill stream fish Garra lamta may enhance the ability of the fish to sense the chemical nature of the surrounding water and food available in a particular feeding zone. Mayer-Rochow Research in Environment and Life Sciences 199 (1981), who observed taste buds on distinct dome like elevation on the surface of tongue of several fish species, suggested that elevated taste buds could have a superior perception of taste, in contrast with nonelevated ones or with receptors sunken below the level of the tongue. The same was also suggested for Salmo gairdneri (Ezeasor, 1982). Singh and Singh (2006) have also observed taste buds in the epidermis of Glossogobius giuris on elevated surface. Taste buds on the dorsal side of lower lip of Pterophyllum scalrae are located in deeper layer and are surrounded by concentric whorls of epithelial cells, characteristic concentric whorls of epithelial cells encircling the taste buds are interesting. Such arrangement of epithelial cells have also been reported in Clarias batrachus (Garg et al., 1995), in cod (Harvey and Batty, 1998), in Lepidocephalichthys guntea (Mittal et al., 2004). Harvey and Batty (1998) stated that the characteristic ring of epithelial cells may make it possible to locate and count taste buds even when their apex was damaged or missing. Generally taste buds are absent in skin folds of Pterophyllum scalrae. Here taste buds are not necessitated or may not be of much significant value probably because the fold of skin lies in deep grooves and do not remain in direct contact with the surrounding medium except when they are temporarily stretched out for short periods during jaw protrusion for feeding. Agrawal and Mittal (1991) have also observed absence of taste buds in skin folds and their presence on lips in Catla catla. Mookerjee and Ganguly (1952) reported the absence of taste buds while Moitra and Bhowmik (1967) reported numerous taste buds in young and comparatively fewer in adult Catla catla. Singh and Gupta (2009) observed the taste buds in the lips and associated structures of Aspidoparia morar. Uninucleated club cells are observed in the lips and associated structures of Pterophyllum scalrae. The uninucleated club cells have been observed in the epithelia of lips and associated strucutres of Catla catla (Agrawal and Mittal; 1991) and Cirrhina mrigala (Agrawal and Mittal, 1992c) while binucleated club cells have been noticed in the epitehlia of lips and associated structures of Rita rita (Agrawal and Mittal; 1992a). Uninucleated conditions of club cells in the epidermis of several fishes belonging to diverse groups has also been reported by previous workers e.g. all Gonorhynchiformes (Pfeiffer, 1960; Pfeiffer and Pletcheer, 1964), some siluridae and Trichomy cteridae (Pfeiffer, 1963a), Mysgurnus fossilis and Nemachilus barbatulus (Jakubowski, 1958, 1959) belonging to the family Gadidae, pleuronecters (Jakubowski; 1960a) belonging to family pleuronectidae, Anguilla anguilla and Anuille spp. (Jakubowski, 1960b; Henrikson and Matoltsy; 1968c) belonging to the family Anguillidae, Wollago attu (Kapoor, 1965) belonging to the family siluridae and Cordoras aeneus (Henrikson and Matoisy, 1968c) belonging to the family callichthyidae. Information regarding functional significance of club cells is available mainly from the studies on epidermis covering general body surface of the fish. It appears that club cells are developed additionally to complement the mucous cells in the efficient functioning of the epithelium in the protection against various hazards. Precise chemical nature of the club cells secretion is poorly understood. The present histochemical study shows that the contents of the club cells in epithelium of lips and associated structures of Pterophyllum scalrae are mainly proteinaceous in nature like those in epidermis of various ostariophysan species (Whitear and Mittal, 1983). Recently Genten and Danguy (1990) using lectins, which are probes

6 for localizing terminal sugar residues or carbohydrate sequence of oliogosachharides have demonstrated the existance of glycoconjugates in club cells in the epidermis of various teleosts. Serotonin and bombesin have also been demonstrated in club cells of some teleosts (Zaccone et.al., 1990, 1999). it is probably that club cells have multiple functions. Singh et al. (2009) also observed the presence of club cells in the lips and associated structures of Aspidoparia morar. Presence of lymphocytes in epithelia of lips and associated structures of Pterophyllum scalrae may be associated with local defence mechanism. Mittal and Munshi (1974), Phromsuthirak (1977), Mittal et al. (1978), Iger and Abraham (1990) have also observed increased occurrance of these cells in the epidermis of fish species in different pathological states and have associated the lymphocytes with immunological reaction of the fish, playing an important role in local defence mechanism. Generally the number of lympthocytes in the epidermis in tropical species in higher than in temperate fish (Mittal et al., 1980). In general the lymphocytes are more numerous in skin folds between rostrum and upper lip and lower lip and ventral head skin than lips and other associated structures. The epithelium of skin folds may be subjected frequently to various pathogens due to their following features; 1. The epithelia of skin folds are thinner than the epithelia of lips and other associated structures. 2. The skin folds lie in groove, where the foreign substances are more often deposited. 3. The epithelium of skin fold is prone to mechanical damage during its stretching at the time of food catching in fishes References Agarwal, N. and Mittal, A.K.: Epithelium of lips and associated structures in Indian major carp, Catla Catla. Japan, J. Ichthyol., 37: (1991). Agrawal, N. and Mittal, A.K.: Structural modification and histochemistry of the epithelia of lips and associated structures of a carp-labeo rohita. Eur. Arch. Biol., 103: (1992a). Agrawal, N. and Mittal, A.K.: Structural organization and histochemistry of the epithelia of lips and associated structures of a carp-cirrhina mrigala. Can J. Zool., 70: (1992b).. Agrawal, N. and Mittal, A.K.: Structure and histochemistry of the epithelia of lips and associated structure of a catfish Rita rita. Jap. J Ichtyol., 39: (1992c). Ezeasor, D.N.: Distribution and ultrastructure of taste buds in the oropharyngeal cavity of the rainbow trout, Salmo gairdneri Richardson. J. Fish Biol., 20: (1982). Garg, T.K., Deepa, V. and Mittal, A.K.: Surface architecture of the opercular epidermis and epithelium lining the inner surface of the operculum of a walking cat fish-clarias batrachus, Japan J. Ichthyol., 37: (1995). Genten, F. and Danguy, A.: A comparative histochemistry analysis of glycoconguiates in secretory cells of fish epidermis by use of biotiny late lectins. Z. Mikrosk. Anant. Forsch., 104: (1990). Gurr, E.: Methods of analytical histology and histochemistry, Leonard, Hill, London. pp 631 (1958). Harvey, R. and Batty, R.S.: Cutaneous taste buds in cod. J. Fish, Biol., 53: (1998). Henrikson, R.C., and Matoltsy, A.C.: The fine structure of teleost epidermis. 3. Club cells and other cells types. J. Ultrastruct. Res., 21: (1968). Jakubowski, M.: The structure and vascularization of the skin of the pondloach (Misgurnus fossilis L.). Acta. Biol. Crac. (Zool)., 1: (1958). Jakubowski, M.: The structure and vascularization of the skin of the stoneloach (Nemachilus barbatulus L.) and burbot (Lota lota L.). Acta. Biol. Crac (Zool), 2: (1959). Jakubowski, M.: The structure and vascularization of the skin of the leathern carp (Cyprinus carpio L. var. nuda) and flounder (Pleuronected flosus luscus pall)., Acta. Biol. Crac. (Zool)., 3: (1960a). Jabubowski, M.: The structure and vascularization of the skin of eel (Anguilla anguilla L.) and viviparous blenny (Zoarces viviparous.l.). Acta.Biol. Crac.(Zool)., 3: (1960b). Lillie, R.D.: Histopathologic techniques and Practical histochemistry. The Blakistan Division, McGraw-Hill Book Co. New York, pp 501 (1954). Mayer-Rochow, V.B.: Fish tongues-surface fine structures and ecological considerations. Zool. J. Linn Soc., 71: (1981).. Mittal, A.K. and Munshi, J.S.D.: On the regeneration and repair of superficial wounds in the skin of Rita rita (Ham) (Bagridae, Pisces). Acta. Anat., 88: (1974). Mittal, A.K. and Banerjee, T.K.: A histochemcal study of the epidermal keratinization in the skin of a fresh water teleost Bagarius bagarius (Ham) (Sisoridae-Pisces). Mikroskopie, 30: (1974). 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