Skeletal System, Skin, & Scales

Chapter 3

Skeletal System, Skin, & Scales

Chapter 3

Fish Skulls

• Neurocranium– Chondocranium

– Dermatocranium

• Splanchiocranium– Gills

– Jaws

• Neurocranium– Chondocranium

– Dermatocranium

• Splanchiocranium– Gills

– Jaws

Region Dermal Bone

Ethmoid Medial Ethmoid

Orbital Frontal

Otic Parietals

Basicranial None

Ethmoid Region

• Medial Ethmoid

• Lateral Ethmoids

• Vomer-vomerine

teeth

• Medial Ethmoid

• Lateral Ethmoids

• Vomer-vomerine

teeth

Orbital Region

• Frontals• Parasphenoid• Pterosphenoid• Orbitosphenoid• Basisphenoid• Infraorbitals• Preorbitals (lacrymal)• Postorbitals• Suborbitals

• Frontals• Parasphenoid• Pterosphenoid• Orbitosphenoid• Basisphenoid• Infraorbitals• Preorbitals (lacrymal)• Postorbitals• Suborbitals

Otic Region• Parietals

• Sphenotic

• Pterotic

• Prootic

• Epiotic

• Parietals

• Sphenotic

• Pterotic

• Prootic

• Epiotic

Otic Region• Parietals

• Sphenotic

• Pterotic

• Prootic

• Epiotic

• Parietals

• Sphenotic

• Pterotic

• Prootic

• Epiotic

Basichranial Region• Supraoccipital

• Exocipitals

• Basiocipital

• Parasphenoid

• Supraoccipital

• Exocipitals

• Basiocipital

• Parasphenoid

Jaw Structure

•Premaxilla•Maxilla•Supramaxilla•Palatine•Dentary

Gill Coverings

• Preopercle• Opercle• Subopercle• Interopercle• Branchiostegals

• Preopercle• Opercle• Subopercle• Interopercle• Branchiostegals

Vertebral ColumnVertebral Column

Paired FinsPaired Fins

Soft Finned RaysSpines vs. Rays

SpinesHard, pointed tissueUnsgementedUnbranchedSolid

RaysSoft, unpointedSegmentedBranchedBilateral (lt. and rt. halves)

FinsFins

Fins

Dorsal (medial) FinsDorsal (medial) Fins

Life imitates art??Life imitates art??

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.

• 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.

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

Leptocercal—dorsal and anal rays joined with caudal Leptocercal—dorsal and anal rays joined with caudal

around posterior of fish (lungfishes, coelocanth).around posterior of fish (lungfishes, coelocanth).

Heterocercal—unequal lobed, vertebral column extends

into the upper portion (sharks, sturgons, gar)

Homocercal—equal lobes (most bony fish)Homocercal—equal lobes (most bony fish)

Isocercal—last vertebrae modified (cods)Isocercal—last vertebrae modified (cods)

Gephyrocercal—”bridge tail”Gephyrocercal—”bridge tail”Dorsal and anal fins have grown aroundDorsal and anal fins have grown around

posterior end of fish. (Mola)posterior end of fish. (Mola)

ScalesScales

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

Placoid scales of the Broadnose Sevengill Shark.

Skin from Sharks

Cosmoid scalesCosmoid scalesCommon to Lungfishes (family Common to Lungfishes (family Ceratodidae) and some fossil fishes.Ceratodidae) and some fossil fishes.

Similar to placoid scales (Probably Similar to placoid scales (Probably evolved from the fusion of placoid evolved from the fusion of placoid scales.) scales.)

Two basal layers of bone, a layer ofTwo basal layers of bone, a layer of dentine-like cosmine, and an outer layer dentine-like cosmine, and an outer layer of vitrodentine. of vitrodentine.

Scale becomes larger as fish grows and Scale becomes larger as fish grows and new bone isnew bone is added to the basal layers.

Scanning electron micrograph of the cosmoid scales of a Queensland Lungfish (Krefft, 1870).Scanning electron micrograph of the cosmoid scales of a Queensland Lungfish (Krefft, 1870).

Found in bichirs (Polypteridae), Bowfin Found in bichirs (Polypteridae), Bowfin (Amia calva), paddlefishes (Polyodontidae), (Amia calva), paddlefishes (Polyodontidae), gars (Lepisosteidae), and sturgeons gars (Lepisosteidae), and sturgeons (Acipenseridae) and some fossil (Acipenseridae) and some fossil paleoniscoid fishes. paleoniscoid fishes.

Rhomboid shape with Rhomboid shape with articulating pegarticulating peg* and * and socket joints between them. Actually, socket joints between them. Actually, modified cosmoid scales with a bony basal modified cosmoid scales with a bony basal layer, a layer of dentine, and an outer layer layer, a layer of dentine, and an outer layer of ganoine (an inorganic bone salt).of ganoine (an inorganic bone salt).

Ganoid ScalesGanoid Scales

*articulating peg

Cycloid and Ctenoid Scales

Found in bony fishes (the Teleostei). Found in bony fishes (the Teleostei). Overlapping = flexibility, over cosmoid Overlapping = flexibility, over cosmoid or ganoid scales.or ganoid scales.

Cycloid scalesCycloid scales—smooth posterior margin, —smooth posterior margin, no ctenii. (Greek "cyclo“ or circle.)no ctenii. (Greek "cyclo“ or circle.)

Ctenoid scalesCtenoid scalesNote: spiny posterior marginsNote: spiny posterior margins

(Greek "cteno", comb-like ctenii on the margin of the scale.) (Greek "cteno", comb-like ctenii on the margin of the scale.)

Leads to concentric growth rings on the scale (estimate age).Leads to concentric growth rings on the scale (estimate age).

Both consist of two main region: Both consist of two main region: surface "bony" layer (Casurface "bony" layer (Ca2+2+ salts) & deeper fibrous layer (collagen). salts) & deeper fibrous layer (collagen).