Biology of Aquatic Organisms Fish anatomy 1
Biology of Aquatic Organisms
Biology of Aquatic Organisms
Fish anatomy
Prof. Dominique Adriaens
Dept. of Biology
K.L. Ledeganckstraat 35, B-9000 Gent

Biology of Aquatic Organisms Fish anatomy 2
What are fishes?
What are fishes?
Myxini
(hagfish)
Petromyzontiformes
(lampreys)
Chondrichthyes
(cartilaginous fishes)
Selachii
(sharks)
Batoidea
(rays)
Holocephali
(chimaeras)
Osteichthyes
(bony fishes)
Actinopterygii
(ray-finned fishes)
Sarcopterygii
(lobe-finned fishes)
GNATHOSTOMATA
VERTEBRATA

shark
• Body regions
– head
– trunk
–tail
Biology of Aquatic Organisms Fish anatomy 6
External morphology
External morphology
-
-
shark
shark
• Head parts
–rostrum
– skull
– pharynx
•spiraculum
• 5 (sometimes 6-7) gill slits
Hexanchus griseus
six-gill shark
Biology of Aquatic Organisms Fish anatomy 7
External morphology
External morphology
-
-
shark
shark
• Head ‘openings’
–mouth
– spiraculum and gill slits

-
-
shark
shark
• Tail appendices
–fins
• dorsal fin (optional)
• anal fin (optional)
• Tail appendices
–fins
• caudal fin
– dorsal lobe (vertebral column)
– ventral lobe
Biology of Aquatic Organisms Fish anatomy 10
Internal morphology
Internal morphology
-
-
shark
shark
• Integumentary system
– skin
• epidermis
– epithelial structure
– non-vascularised
– chromatophores
– enameloblasts
» enameloid layer of
placoid scales
• dermis

Internal morphology
Internal morphology
-
-
shark
shark
• Skeletal system
– cartilage
• hyaline cartilage
• mineralised cartilage
– deposition of hydroxy-apatite
minerals
– areolar
» growth rings in vertebrae
–prismatic
» very dense
» laid down in prismatic
pattern
– globular
» nanoscale globular
mineral condensations
Hyaline cartilage
(Scyliorhinus caniculus)
Mineralised cartilage
(Rhinoptera bonasus)
(From Summers, 2000)
form tesserae:
chain of mineralised blocks
Biology of Aquatic Organisms Fish anatomy 13
Internal morphology

• neurocranium
–rostrum
– rostral fenestra
– nasal capsules
– epiphyseal foramen
– pore of endolymphatic ducts
–orbita
» antorbital process
» eye losely attached or
with optic pedicel
» postorbital process
– brain case
– otic capsule
– occipital region
Biology of Aquatic Organisms Fish anatomy 15
Internal morphology
Internal morphology
-
-
shark
shark
• Skeletal system
– cranial skeleton
• splanchnocranium
– mandibular arch
» palatoquadrate
» Meckel’s cartilage
» labial cartilages
– hyoid arch
» basihyal

(
Cetorhinus maximus
Cetorhinus maximus
–
–
basking shark)
basking shark)
Jaw protrusion and cutting
Jaw protrusion and cutting
(
(
Carcharias
Carcharias
carcharodon
carcharodon
–
–
great white)
great white)
Jaw protrusion and cutting
Jaw protrusion and cutting
(
(
Isistius brasiliensis
Isistius brasiliensis
–
–
cookie cutter shark)
cookie cutter shark)
Biology of Aquatic Organisms Fish anatomy 17

– postcranial skeleton
• median fins
– dorsal and anal fin
» basal pterygiophore
» radial pterygiophores
» ceratotrichia
» spine (sometimes)
• caudal fin
– dorsal lobe
» vertebral column
» radial pterygiophores
» ceratotrichia
– ventral lobe
» enlarged haemal arches
» ceratotrichia
Biology of Aquatic Organisms Fish anatomy 19
Internal morphology
Internal morphology
-
-
shark
shark
• Skeletal system
– appendicular skeleton
• pectoral girdle
– scapulocoracoid
• pectoral fin
– basal pterygiophores
» propterygium
» mesopterygium