Skeleton, Integument & Fin Architecture : Fish Biology Midterm II

Osteology

The scientific branch of biology dedicated to the study of bone structures

Integument

the transitional protective boundary that shields the fish from surrounding aquatic environments includes both skin (epidermis/dermal layers) and dermal scales

Neurocranium

Braincase, encloses the brain and primary sensory organs. Formed by 4 distinct regions

Ethmoid, Orbital, Otic, Basicranial

4 regions of Neurocranium

Ethmoid Region

Anterior-most cartilaginous/bony region around the jaws

Orbital Region

Surrounds and protects the eye orbits

Otic Region

Formed by 5 cartilage bones that encase the inner ear chamber

Basicranial Region

Forms the base and posterior wall of the skull, joining the braincase to the vertebral colum

Branchiocranium

Visceral Arches, Endoskeletal arches originally supporting the gill apparatus, comprising the Mandibular arch (jaws), Hyoid arch, Opercular arch, Palatine arch, and Branchial complex

Protocercal

Primitive, symmetrical fin wrapping around the neural/hemal spines (eg. hagfish, lampreys)

Heterocercal

Assymmetrical tail where the vertebral colum flexes dorsally into the elongated upper lobe (e.g. sharks, sturgeons)

Homocercal

Externally symmetrical cadual fin supported internally by hypural plates on a modified urostyle (e.g. teleosts)

Leptocercal

Secondarily tapered, whip-like tail structure (e.g. coelacanth, lungfishes)

Spiny Rays

Rigid hard, unsegmented solid

Spiny Rays

Unbranched single spine element

Spiny Rays

Single median structure (unpaired)

Soft Rays

Flexible, segmented along length

Soft Rays

Frequently branched distally ray branching pattern

Soft Rays

Bilateral paired halves (left/right hemirays)

Placoid

pulp core, dentine, vitrodentine enameloid capP

Placoid

Elasmobranchs (sharks, rays)

Placoid

Tooth-like; reduces hydrodynamic drag

Ganoid

Isopedine bone base with heavy ganoine enamel

Ganoid

Gars (Lepisosteidae, Sturgeons)

Ganoid

Heavy, interlocking protective armor plates

Cycloid

Thin, flexible dermal bone with concentric circuli

Cycloid

Soft-rayed teleosts (salmonids)

Cycloid

Smooth edge; minimizes swimming friction

Ctenoid

Thin dermal bone with ctenii (comb teeth) on edge T

Ctenoid

Spiny-rayed teleosts (percoids)

Ctenoid

Disrupts boundary layer turbulence