Inteugmentary system of fishes

Inteugmentary system of fishes

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  INTEGUMENTARY SYSTEM OF FISH ANATOMYAND HISTOLOGY BY R.PRATHISHA Department of fish pathology FC&RI- Tuticorin
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  • The layersof teleost skin, comprising the cuticle, epidermis, basement membrane, dermis and hypodermis
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  EPIDERMIS • The thicknessof the epidermis varies with species, age, size and, often, stage of the reproductive cycle • It is usually thicker in those species with negligible scale cover (e.g.the eel) and also over the fins, where it is particularly well endowed with nerve end organs and mucous cells
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  • The fundamentalunit -fibrous malpighian cell • In adults the epidermis is a stratified squamous epithelium covering the body surface and investing the tail and fins.
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  This section showsthe stratified epidermis containing Malpighian cells (1) and mucous cells (arrows).The basement membrane (dark blue) is particularly thick in this image. Melanophores (dark-brown) are located in the dermis (2).
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  • They arerounded cells very similar in structure at all levels except the outermost, where they are flattened horizontally • Cytoplasm -elongated vesicles, degenerating mitochondria and some dense bundles of fibres
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  • Stratified squamousepithelium- 3 layers stratum basale/germinativum stratum of variable layers of fusiform cells the outer cuticular layer
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  The typical twolayers of teleost skin comprise epidermis (1) and dermis. This latter usually is made up of two strata: an upper spongiosum (2) right beneath the epidermis and a deeper compactum (3).Collagen is stained blue. On the striated muscles in cross (4) and longitudinal (5) sections.
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  Stratum germinativum Single layerof columnar epithelium situated on basement membrane Basal cells contain; • Large ovoid nuclei • More diffuse chromatin than nuclei in cells in other cell layers
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  Zebra fish Anautoradiograph of section of zebrafi sh skin from a specimen intraperitoneally injected with tritated thymidine two hours previously. The silver grains (dark dots) covering the nuclei of dividing cells are found at all levels of the epidermis. This is a major difference compared to mammals where only the basal layer cells (stratum germinativum) undergo mitosis!
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  In addition tolarge glandular epithelial cells (arrow)and ordinary Malpighian cells everywhere else, branched melanophores (brown-black) are illustrated.Note that the pigment cells can be found within the epidermis!
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  Stratum of variablenumbers of fusiform cells • With rigid walls, tonofibrils and irregularly shaped dense nuclei Cells: Vary from cuboidal to squamous as they approach the outer cuticular layer of the epithelium
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  CUTICLE • The externallayer, the cuticle or glycocalyx,mainly mucopolysaccharide • layer approximately 1 μ m thick.
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  Contains specific immunoglobulins and lysozymeand free fatty acids Tail skin of whiting, showing cuticle, epidermis and dermis. PAS ×142.
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  Includes; • Most stratifiedlayer of epithelium • outer mucous coating • The outer epidermal cells of fish(living)- no keratinized surface cells
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  mucus-secreting cells (magenta- 1). The other epidermis cells are filament-containing or Malpighian cells (2) always in majority. One can see chromatophores (3) in the dermis (4).
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  Unique cell types •Malpigian cells • Club cells • Chemosensory cells • Chloride cells • Mucous/ goblet cells
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  • serous cells.eg armouredcatfishes, trout, sharks And other glandular cells • albuminoid/ acidophilic gland cells eg: sharks, skates,and rays
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  Malpighian cells (2)Malpighiancells (1)
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  Mucus cells. • Coveringthe squamous epithelium • Secreted from mucus glands • Diferentiate in the stratum germinivatum and migrate towards the surface • Have basal compact nuclei • Filled with membrane enclosed packets of glycoproteins • Sulfo mucin protect fish from bacterial and fungal infections
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  This micrograph illustratesthe thick epidermis of a young specimen. This stratified layer contains numerous mucous cells filled with secretion (magenta- 1) as well as other ones (unstained - 2) having secreted their mucus to form the mucous coat (arrowheads)
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  Club cells • Giantcells(multinucleate) • Alarm substance cells Carp(Shreckstoffzellen) produces pterin which initiates alaram reactions when percieved by olfactory organs of other fishes of the school • Found in the middle of epidermis do not open to the surface of epithelium and completely distinct from mucus cells • Vary in number and size of nuclei in different species
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  Pangasius micronemusThe fright reactionelicited by alarm substance produced by special epidermal cells : the club cells (arrows). These large cells have a centrally located nucleus (1) and an eosinophilic cytoplasm(2). As they do not reach the surface of the integument, only injury of the skin can release the content of these cells into the water leading to the fright reaction of congeners. The arrowheads point to superficial mucous cells. In green, the dermis.
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  Heteropneustes fossilis Head epidermisstained immunohistochemically with an antibody against a family of stress proteins(heat shock proteins, HSP 70). The alarm substance cells (club cells) are heavily stained (arrows) unlike the mucous cells which are negative (arrowheads).Note some basal filament-containing cells (1) and melanophores (black) of the dermis underneath the epidermis basement membrane (2).3 :dermis1
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  Granule cells • Granulecells are found in a wide variety of teleost epidermes but as yet no function has been described • Other cells found in the epidermis include lymphocytes,macrophages and large clear cyst - like structures,of putatively cellular origin, which are especially prominent in the Gadidae.
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  Scales • Provides protectionto the outer surface of the epithelium • Histologically scales are acelluar dermal bone • Mineralized matrix around collagen • Anchored in dermal pockets between layers of collagen in stratum spongiosm of dermis& and epidermal basement membrane
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  Scales (1) originatein dermal scale-pockets and protrude posteriorly (short arrows) where they are covered by the epidermis (2).The epidermis is thinner (arrowheads) above the free portion of the scales The long arrow points to the stratum laxum of the dermis. Stratum compactum is stained green. Skeletal (epaxial) muscle cells fill the lower half part of the image
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  Symphysodon aequifasciatus Scales (arrows)embedded in the dermis,.The (*) pinpoints a scale-pocket actually formed by a skin fold in which a scale is seated. The arrowhead points to the epidermis
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  Anguilla anguilla Europeaneel have minute bony scales (arrows) barely visible to the naked eye. Scales and dermis (*) are unreactive as compared to the epidermis (in brown except for the mucous cells).
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  The placoid scalesof living Chondrichthyans are isolated tooth- like denticles. Each of them contains a pulp cavity (partially visible - arrow) and consists of a dermal bony basal plate (1), a middle layer of dentine and a spine (2) covered with enamel. The scalespenetrate the surface of the epidermis at the time of hatching.
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  This micrograph illustratesa fragment of ctenoid scale. The small stiff spines (arrows) on its free posterior surface differentiate ctenoid from cycloid scales which lack such spines
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  • Parts ofupper and lower scale covered by epidermis Connecting cells: Hyposquamal cells Present as 2 or 3 layers on the underside of the scale or the surface close to the body Hyposquamal cells connected episquamal cells by radius cells.
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  Dermis • Underneath theepidermis Inner stratum spongiosm Outer stratum compactum
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  Gnathonemus petersi Thetypical two layers of teleost skin comprise epidermis (1) and dermis. This later usually is made up of two strata: an upper spongiosum (2) right beneath the epidermis and a deeper compactum (3).Collagen is stained blue. On the striated muscles in cross (4) and longitudinal (5) sections.
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  Collagen fibres • Fishessuch as glass catfish, glass eel, the arrangement of collagen fibres is extremely regular • Allowing light to pass through the dermis unreflected • In these fish the peritonium is pigmented to protect the abdominal organs from light
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  Heteropneustes fossilis Stratum laxumdepends on whether or not there are scales and can even be absent as in this case. At the contrary, a stratum compactum (1)is always present and is important in locomotion
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  Pigment cells • Dermiscontains pigment cells that can occur in layers at different levels • Pigment cells contain vareity of pigments other than melanin Carotenoids Pterin Guanine crystals(silvery color)
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  Melanophores • Containing melaninabsorbs the entire visible range of light Astronotus ocellatus Melanophores (dark-brown) are located in the dermis (2)
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  Thalassoma pavo Dermalmelanophores photographed on isolated scales of this gorgeously coloured fish. Here these cells have a relatively small diameter (about 2500 cells /scale). Note numerous cell processes extending from the cell bodies. The central cell on the image shows aggregated melanin (with no processes).
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  Pangasius micronemusThe fright reactionelicited by alarm substance produced by special epidermal cells : the club cells (arrows). These large cells have a centrally located nucleus (1) and an eosinophilic cytoplasm(2). As they do not reach the surface of the integument,only injury of the skin can release the content of these cells into the water leading to the fright reaction of congeners. The arrowheads point to superficial mucous cells. In green, the dermis. Pterin
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  Xanthophores • Contains rhodopterinand carotenoid granules and appear yellow to orange
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  Iridophores • Cells thatcontain platelets of guanine or hypoxanthine are called iridophores • These cells reflect light rather than absorb it giving fish their shiney appearance
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  Hypodermis • Lies betweenthe stratum spongiosm of the dermis and skeletal or muscular elements beneath the skin • Primarily consists of areolar connective tissue and is usually most prominent along the flanks. • Head region- the hypodermis is indistinguishable from the stratum spongiosum • It is a frequent site of development of inflammatory processes
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  Fins • Large foldsof skin with special support • Covered by stratified squamous epithelium continuos with the epidermis of the body • The underlying dermis have reduced stratum compactum and increased hypodermis
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  Soft segmented rays Pairedlepidotricha composed of dermal bone that develops from the same primorida as the scales
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