Sistem integumen Penutup tubuh ikan kulit sisik jari

Sistem integumen Penutup tubuh ikan (kulit, sisik, jari sirip, tulang kepala, warna, kelenjar beracun)

Fungsi kulit tubuh ikan • • Pertahanan pertama terhadap penyakit Perlindungan terhadap kondisi sekeliling Alat bantu pernafasan Tempat kelenjar beracun Sumber pewarnaan Sumber cahaya Tempat lendir dan bau yang khas

epidermis • Stratum germinativum – – – Cuboidal Mitotic Division Migrate Distally Differentiate Sloughed off (aktif membelah untuk mengganti sel yang terlepas dan untuk pertumbuhan) • Synthesis of keratin – Water insoluble protein that fills cells – Stratum corneum of Vertebrates Selalu basah karena sel-sel kelenjar di seluruh permukaan tubuh

Dermis – – – Proximal Migration and differentiation of of collagen fibers and other structures Untuk ikan bersisik berperan dalam pembentukan sisik) Two layers • • – – Stratum laxum (spongiosum) Stratum compactum Blood vessels, nerves, pigment cells Endotherms – bases of hair and feathers + erector muscles ¶ “Ancient and persistent potential to form bone”

Fish No dead cells like mammals, cells alive, no keratin production in cells except for horny teeth of lampreys and nuptial tubercles Glands 1. Unicellular - abundant mucous glands in epidermis. • maintains stable internal environment • protects form bacteria, ectoparasites • reduces drag when swimming Some glands (granular) secrete pheromones when fish injured, triggers reaction in nearby fish

2. Multicellular glands growing down into dermis are uncommon • large slime glands in hagfish • poison glands (spines) • light generating glands Photoblepharon Flashlight fish – contains symbiotic bacteria, shutter mechanism Angler fish

Flatfish camouflage operates through visual system (blinded fish go dark) but still uses sympathetic ns & MSH to alter chromatophore units

Bony scales Same as bone in mammals, osteocytes, lacunae, canaliculi, hydroxyapatite mineral, teleosts have acellular bone. Develop in exactly the same way as teeth, original dermal cells of papilla are neural crest.

Next, epidermal cells induced to AMELOBLASTS to form enamel organ = enamel. Next ameloblasts induce odontoblasts in dermal cells underneath Enamel, hardest tissue in body, 96% hydroxyapatite. If deposited in waves gives lamellar appearance

Shark has vascular cavity, but same materials. Very hard capping material Isolated remnants of the early jawless fishes which first evolved – cosmoid plates – dermal armour.

lendir • Gel protein (muein), tersentuh air menjadi lendir, tebal pada ikan tidak bersisik • Fungsi lendir: • a. mengurangi gesekan dengan air, ikan bisa berenang • • • cepat B. permeabel, mencegah keluarmasuknya air melalui kulit C. mencegah infeksi D. penutup luka E. mencegah kekeringan kulit F. bahan pembuat sarang (ikan paru-paru saat tidur musim panas, ikan sepat jawa dan sepat siam membuat sarang dari lendir saat memijah)

lendir

• Fish are aquatic – Conservation of structure and function among the different fish groups. – Bony scales • Characterize the skin of most fishes • Substances (tissues) that contribute to bony scales – Bone – Dentine – Enamel

Function of bony scales • Protection from parasites, other predators • Positioning: – Slide one atop the next – Allow for the distortion of body • Hydrodynamic function to reduce drag • Feeding

• Cellular Bone – Extra-cellular matrix of collagen fibers – Embedded in polysaccharide ground substance – Matrix laid down by osteoblasts • Differentiate from mesenchyme cells of the dermis – Calcium phosphate crystals (hydroxyapatite) bind to fibers – During osteogenesis • Osteoblasts mature and become entrapped in matrix – osteocytes • Osteocytes are located in lacunae – Small cavities interconnected by canals (canaliculi) – Cell processes are extended through these canals • Bone of fish scales – “dermal bone” (cf. “cellular bone”)

Bony scales • Bone is deposited by osteocytes on the periphery of a developing scale • Osteocytes move centrifugally away from center of scale • No bone cells or processes are left behind • Then dentine and enamel layers can be added to the surface of the bone for increased hardness of scale

Dentine and Enamel • Mesenchymal aggregation (papilla) beneath basement membrane • Basal cells above the papillae respond and differentiate into ameloblasts – Ameloblasts – collectively called the enamel organ – Secrete enamel – Retreat • Underlying dermal cells differentiate into odontoblasts – secrete dentine – Retreat in direction opposite of ameloblasts – Leave long cytoplasmic processes – dentine tubules

Types of Bony Scales • Cosmoid plates and scales – Ostracoderms – Cosmine – “dentine” • Ganoid plates and scales – Actinopterygian fishes – Bichirs (Polypterus), Garpikes

Types of Bony Scales • Modern – Cycloid and Ctenoid – Most teleosts

Dermal Scales Figure 8. 7: Cycloid, ctenoid, placoid, and ganoid scales of modern fish.

Figure 8. 8: Derivatives of primitive dermal bone.

Dermal Scales Figure 8. 9 • Ctenoid scales – Growth rings or annuli • Fish have no epidermal scales – Scales are dermal

Sisik ikan • Cycloid dan ctenoid: bentuk sangat tipis, transparant, tidak mengandung dentin dan enamel, terdapat pada ikan bertulang sejati. Cycloid terdapat pada ikan berjari sirip lemah (Malacopterygii). Ctenoid terdapat pada ikan berjari sirip keras (Acanthopterygii) • Cosmoid: pada fosil ikan, komponennya virodentin, cosmin, isopedin (bahan tulang) dan pembuluh darah kecil

Sisik ikan • Ganoid: pada ikan Actinopterygii, lapisan luar mengandung garam organik (ganoine) • Placoid: pada ikan Chondrichthyes, seperti duri, bahan sama seperti gigi. Lapisan terluar dilapisi enamel yang membungkus dentin. Didalam dentin ada canaculi, ada pembuluh darah dan ujung syaraf dermis

Sisik placoid

placoid • • Placoid scales – paleozoic sharks, elasmobranchs – Also called dermal denticles – Spinous process • From dermis – Dentine, surrounding a vascular pulp cavity and capped by enamel – Become teeth at jaws

Sisik cosmoid

Sisik ganoid

Sisik ikan cycloid dan ctenoid

Letak sisik ikan • Menyeluruh (belakang operculum sampai sirip caudal): ikan betok/betik, ikan gabus • Tidak merata: polyodon (dibawah operculum), tongkol (bagian depan dorsal dibelakang kepala), ikan mas (disekitar lateral line) • Tidak bersisik: ikan lele • Setengah bagian sisik menempel pada kantong di dermis dengan susunan seperti genting (anterior: tidak berwarna, posterior: berpigmen)

Sisik ikan • Selama pertumbuhan ikan, sisiknya bertambah (ukuran) tidak dalam jumlahnya • Ruptur sisik: bisa diganti sisik baru • Garis lingkaran (circulus) selalu bertambah selama hidup ikan • Circulus yang berdempetan = annulus, annuli (banyak), untuk menghitung umur ikan • Sisik lateral line tidak bisa digunakan untuk menghitung umur ikan

Warna ikan • Intensitas warna ikan berkurang saat ikan mati • Warna ikan bisa lebih indah dibanding warna burung atau kupu-kupu • Tidak semua ikan berwarna cerah, terkadang berwarna coklat, abu-abu, hitam yang merata di seluruh tubuh • Warna ikan merefleksikan tempat hidupnya • Ikan dasar: warna pucat di bagian perut dan gelap di bagian punggung

Warna ikan • Ikan laut memiliki 3 warna dasar, ikan di permukaan laut bewarna keperakan, kemerahan di perairan agak dalam, dan ungu kehitaman atau hitam di laut dalam • Ikan yang hidup di karang memiliki totol warna sesuai lingkungannya (mimieri) • Ikan bisa berkamuflase warna karena adanya predator, disebabkan stimuli mata (perubahan secara cepat) dan hormon (perubahan secara lambat)

warna ikan

Sel warna ikan • Iridocyte (leucophore dan guanophore), tersusun dari guanin, merefleksi warna di luar tubuh = sel kaca • Chromatophore, ada di dermis, jika warna mengumpul ikan berwarna pucat, jika menyebar, warna menjadi jelas, ikan berwarna cerah

• Chromatophore dasar ada 4: erythrophore (merah oranye), xanthophore (kuning), melanophore (hitam), guanophore (putih keperakan karena sel iridocyte)

Body Coloration 1) source of color a) pigment color - chromatophores for yellows, reds, oranges, browns, & blacks b) structural color - iridophores (reflection) & light refraction for blues, silvers, & rainbows

2) patterns (pp. 152 -153) a) countershading 1) dark blue or black dorsally, white or silvery ventrally 2) results in blue water "camouflage“ 3) observed most frequently in pelagic cruisers

b) camouflage 1) matching the background coloration 2) usually involves having irregular dark blotches and spots 3) typically seen in benthic fishes, especially benthic ambush predators (e. g. , frogfishes, gobies, & many scorpionfishes) 4) some fishes (e. g. , flatfishes) may exhibit rapid color changes in response to different backgrounds

b) camouflage 5) matching downwelling light Hatchet fish Cookie cutter shark

c) disruptive coloration 1) color pattern breaks up the silhouette of the fish 2) may involve dark bars across the eye and tail region 3) seen in many demersal fishes such as butterflyfishes

d) bars and stripes 1) bars are vertical (e. g. , manini) 2) stripes are horizontal (e. g. , ta'ape) 3) seen frequently in schooling demersal fishes 4) may confuse potential predators by making it difficult to select individual prey from the school

e) misdirection 1) false eye spots, etc. 2) observed in many demersal butterflyfishes

f) advertising coloration 1) bright, obvious color patterns 2) possible functions a) advertising a cleaning station (e. g. , cleaner wrasses) b) advertising a warning (e. g. , nohu) c) advertising for mates (e. g. , male parrotfishes) Hawaiian cleaner wrasse Nohu

g) mimicry 1) imitating other creatures 2) seen in a few demersal and benthic fishes 3) examples a) blenny (Aspidontus taeniatus) mimics cleaner wrasses b) shortnose wrasse mimics Potter's angel which sports a defensive spine

g) mimicry 4) leafy sea dragon (Australia)

h) uniform red coloration 1) most often observed in deep-dwelling or night active demersal fishes 2) examples include opaka, oweoweo, menpachi, & squirrelfishes

i) noctural versus diurnal color changes j) male versus female color differences k) juvenile versus adult color differences Bluehead wrasse Stoplight parrotfish Dragon wrasse

Organ bercahaya

Asal cahaya pada ikan • Bakteri yang bersimbiose dengan ikan, terdapat pada kantong kelenjar epidermis. Contoh ikan famili Monocentridae, Gadidae, Leognathidae, Serranidae, Macroridae • Pemantulan cahaya diatur oleh jaringan yang berfungsi sebagai lensa. Bagian berlawanan lensa banyak pigmen yang berfungsi sebagai pemantul. Pemancaran cahaya yang dikeluarkan bakteri diatur oleh kontraksi pigmen yang berfungsi sebagai iris mata

Asal cahaya pada ikan • Dikeluarkan langsung oleh sel kulit ikan = photophore/ photocyte • Elasmobranch: Etmopterus, Benthobatis, Spinax • Teleost: Batrachoididae, Stomiatidae

Kelenjar beracun

• Potamotrygon, ikan air tawar di Amerika, memiliki racun seperti racun ular • Ikan lepu tembaga (Synanoeja sp): racunnya pada lapisan kulit penutup jari-jari keras D dan V • Ikan beronang (Sigamus spp), kelenjar beracun pada jari-jari sirip keras D dan V • Ikan pari : racunnya pada ekor • Ikan lele lokal jawa, kelenjar racunnya pada jari-jari keras D dan P