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
Class Actinopterygii
“rays” + “fins/wings”
- >34, 600 spp.
- Ray fins: rays form a joint with pectoral girdle
Class Actinopterygii -> subclass Cladistia
- AKA Polypterids; reedfishes and bichirs
- 13 spp.
- sister group “to the rest”
- unique dorsal finlets
- thick ganoid scales
- diphycercal tail
- lungs (air breather)
Class Actinopterygii -> subclass chondrostei -> Acipenserids: paddlefishes and sturgeons
- 29 spp.
- cartilaginous endoskeleton
- some ossification
- heterocercal tail
- spiracle (retained)
- modified ganoid scales
- scutes (sturgeons)
- electroreceptors on paddle
Class Actinopterygii -> Subclass neopterygii -> Holosteans: gars and one bowfin
- 8 spp. (only one bowfin)
- light ossification over cartilaginous skeleton
- “ganoid” scales
- Abbreviated heterocercal tail
- lungs/swim bladder for breathing + buoyancy
Class Actinopterygii -> subclass Neopterygii -> Teleosts: 99% (the rest!)
- > 25, 000 spp.
- Ossified bony skeleton
- homocercal tail (some secondarily modified)
- loss of basal bones in fins (only fin rays)
- cycloid or ctenoid scales
- swim bladder (from lung)
- pharyngeal jaws (keep food from escaping)
- mobile premaxilla jaw
Clade Sarcopterygii
- “flesh + fins/wings”
- 8 spp.
- Unique monobasal pectoral and pelvic fin attachments to girdle; homologous to humerus/femur
Sarcopterygii -> Class Actinistia: Coelacanths
- “Living Fossils”
- “Hollow + spine”
- 2 spp.
- Rostral organ (electroreceptive)
- Lobed structure of 2nd dorsal, anal fins
- Modified cosmoid scales; spikey surface
- Muscular lobe in center of tail
Sarcopterygii -> Class Dipnoi: Lungfishes
- “two + breathing”
- closest *living relatives to tetrapods
- double circulation (i.e., lungs-heart-body-heart
- crushing tooth plates
- diphycercal tail
1. South American lungfish - 1 spp.
- well developed lungs
- choanae/internal nares (i.e., will drown in water!)
2. African lungfish - 4 spp.
- well developed lungs
- estivation capability
3. Australian lungfish - 1 spp
- strongest fins (swimming)
- gill respiration
- i.e., the most aquatic
Clade Tetrapodomorpha -> Superclass Tetrapoda
Devonian World
- 2 major land masses: Gondwana and Euramerica
- Climate warm; continental centers dry; no polar ice caps
- Extensive shallow seas
- Plant “explosion”; terrestrial forests (end)
- Diverse arthropods (end)
Late “Fishapods”
- Late Devonian lobe-finned fish and amphibious tetrapods
- What features evolved in aquatic “fishapods” that made move to land possible?
- Eusthenopteron
- Late Devonian (385 mya)
- Strictly aquatic
- 1 upper arm bone (humerus) and 2 forearm bones (radius and ulna)
- Tiktaalik
- 375 mya
- “the perfect intermediate”
- No operculum and detached shoulder girdle = neck!
- i.e. can lift the head
- Some support on fins
- Weight bearing girdles, wrists
- Acanthostega - “Boris”
- End Devonian (365 mya)
- 8 toes/digits on limbs = tetrapod
- Beginning of connection of pelvic girdle
- Weight support
- Icthyostega
- 365 mya
- Shoulder girdle and muscles
- Pelvic girdle strongly attached!
- 7 toes/digits = tetrapod
- Fish-like tail (i.e., still aquatic)
- Amphibian skull and lungs, ear to detect airborne sounds
