Osteichthyes - the Bony Fishes Flashcards
Osmoregulation Strategies
Iso/Hyper/Hypoosmotic regulation:
- Kidneys, gills, special organs (e.g. rectal galnd), other barriers (e.g., skin, scales, armor
Agnathans:
Isosomotic to thei env:
- Internal solute conc is very similar to that of salt water
- Permeable skin
Chondrichthyes Osmoregulation
Hyperosmotic to their env.
(i.e., saltier than sea!)
- live in SW so counterintuitive, why?
- Retaining (urea) in tissues to help retain water; so also need TMAO
- Rectal gland: secrete salts (balance)
- FW rays also hyperosmotic but don’t retain urea, reduced rectal gland
Other Osmoregulation strategies
Marine Bony Fish:
Hypoosmotic to env
- Internal (solute) lower than SW around
Freshwater Bony Fish:
Hyperosmotic to their env
- Internal (solute) higher than FW around
Osteichthyes
- “bone + fish”
1. Class Actinopterygii- ray-finned fishes
- Clade Sarcopterygii
- lobe-finned fishes
- tetrapods
Characteristics- Ossified endochondral bone
- Dermal body operculum
- Dermal bony scales
- Lungs/swim bladder
- tetrapods
- ray-finned fishes
- ossified endochondral bone
Ossification:
- laying down new bone by osteoblast cells
Endochondral ossification:
- replacing cartilage model
- bony fishes and tetrapods only
- formation of long bones, growth, and repair
- Dermal Bony Operculum
- Increase respiratory efficiency
- smooth outer surface for streamlining
- Dermal Bony Scales
- From body plate armour… to small, flexible, streamlined scales of bony base = lightweight!
- Scales are dermally-derived
- cartilaginous fish: placoid scales
- Bony fishes: bichirs, gars and bowfins (modified), paddlefishes (modified): ganoid scales
- Higher order bony fishes: *Cycloid (e.g. salmon) and *ctenoid (e.g. perches) scales
- Lungs/swim bladder
Physostomous:
- gas exhchange vis esophagus
Physoclistous:
- gas exchange via blood
Adaptations of Bony Fishes
- Locomotion: pushing against water
- Buoyancy: swim bladder for neutral buoyancy
- Respiration: oxygen less abundant
- Water and ion balance: exchanges with water
- Reproduction: mainly broadcast spawning
- Locomotion
Bu
- Buoancy
Fish are slightly heavier than water
- Swim bladder, as a gas-filled space, is the most efficient flotation device
- Swim bladder arose from paired lungs of primitive Devonian bony fishes
- Respiration
- Gill rakers, arches, filaments, lamellae, blood vessels, capillaries
- Countercurrent gas exchange -> extremely efficient
- osmotic regulation
- Freshwater fish
- the fish has a higher fluid (salts) than surrounding water
- must stop water implosion!
- hyperosmotic regulators
- Dilute urine; salt absorbing cells - Marine Fish
- This fish has less fluid (salts) than surrounding water
- Must stop dehydration!
- Hypoosmotic regulators
- Drink lost; salt secretory cells
Diadromous Fishes: Anadromous or Catadromous
Anadromous: born in FW, go to SW, back to FW (Salmon, lampreys)
Catadromous: born in SW, go to FW, back to SW (e.g. eels)
Adapt by:
- progressive changes in physiology and appearance (i.e. growth)
- Hormonal production and activation of chloride cells
- Change drinking amounts
- Changes in kidney functions/urine flow
- Reproduction
- Dioecious
- Mostly external fert/oviparous
- Some anadromous/catadromous
- Various external development/life stages
- Various parental care strategies