Skeletal System, Skin, & Scales Chapter 3

1. Skeletal System, Skin, & Scales Chapter 3

2. Fish Skulls • Neurocranium • Chondocranium • Dermatocranium • Splanchiocranium • Gills • Jaws

4. Ethmoid Region • Medial Ethmoid • Lateral Ethmoids • Vomer

5. Orbital Region • Frontals • Parasphenoid • Pterosphenoid • Orbitosphenoid • Basisphenoid • Infraorbitals • Preorbitals (lacrymal) • Postorbitals • Suborbitals

6. Otic Region • Parietals • Sphenotic • Pterotic • Prootic • Epiotic

7. Otic Region • Parietals • Sphenotic • Pterotic • Prootic • Epiotic

8. Basichranial Region • Supraoccipital • Exocipitals • Basiocipital • Parasphenoid

9. Jaw Structure • Premaxilla • Maxilla • Supramaxilla • Palatine • Dentary

12. Gill Coverings • Preopercle • Opercle • Subopercle • Interopercle • Branchiostegals

13. VertebralColumn

14. Paired Fins

17. Soft Finned Rays Spines vs. Rays Rays Soft, unpointed Segmented Branched Bilateral (lt. and rt. halves) Spines Hard, pointed tissue Unsgemented Unbranched Solid

18. Fins

19. Fins

20. Dorsal (medial) Fins

21. Caudal Fins • Caudal fins are highly variable in shape but essentially serve the same function; that being forward motion, although some do it better than others and some provide additional benefits.

22. Protocercal—primative, extends around the posterior end (lancelets)

23. Leptocercal—dorsal and anal rays joined with caudal • around posterior of fish (lungfishes, coelocanth).

24. Heterocercal—unequal lobed, vertebral column extends • into the upper portion (sharks, sturgons, gar)

25. Homocercal—equal lobes (most bony fish)

26. Isocercal—last vertebrae modified (cods)

27. Gephyrocercal—”bridge tail” • Dorsal and anal fins have grown around • posterior end of fish. (Mola)

28. Scales

29. Placoid scales Found in sharks and rays, and can vary greatly in external appearance. They do not increase in size as the fish grows, instead new scales are added. Placoid scales are often referred to as denticles. Placoid scales consist of a flattened rectangular base plate which is embedded in the fish, and variously developed structures, such as spines, which project posteriorly on the surface. The spines give many species a rough texture. Placoid scales of the Broadnose Sevengill Shark.

30. Skin from Sharks

31. Cosmoid scales Common to Lungfishes (family Ceratodidae) and some fossil fishes. Similar to placoid scales (Probably evolved from the fusion of placoid scales.) Two basal layers of bone, a layer ofdentine-like cosmine, and an outer layer of vitrodentine. Scale becomes larger as fish grows and new bone is added to the basal layers. Scanning electron micrograph of the cosmoid scales of a Queensland Lungfish (Krefft, 1870).

32. Ganoid Scales Found in bichirs (Polypteridae), Bowfin (Amia calva), paddlefishes (Polyodontidae), gars (Lepisosteidae), and sturgeons (Acipenseridae) and some fossil paleoniscoid fishes. Rhomboid shape with articulating peg* and socket joints between them. Actually, modified cosmoid scales with a bony basal layer, a layer of dentine, and an outer layer of ganoine (an inorganic bone salt). *articulating peg

33. Cycloid and Ctenoid Scales Found in bony fishes (the Teleostei). Overlapping = flexibility, over cosmoid or ganoid scales. Cycloid scales—smooth posterior margin, no ctenii. (Greek "cyclo“ or circle.)

34. Ctenoid scales Note: spiny posterior margins (Greek "cteno", comb-like ctenii on the margin of the scale.)

35. Both consist of two main region: surface "bony" layer (Ca2+ salts) & deeper fibrous layer (collagen). Leads to concentric growth rings on the scale (estimate age).