The Biology of Fish I Flashcards
Describe the Deep sea Anglerfish
- order Lophiiformes
Juvenile Antarctic icefish
Chionodraco hamatus
Blind Mexican cavefish
Astyanax fasciatus
Leafy sea dragon
Phycodurus eques
What are fish?
- grade, not clade
- share common characteristics
- paraphyletic group: contains most recent common ancestor, but does not contain all the descendants of that ancestor
What are the main extant groups of fish:
- Agnatha (cyclostomes)
- Chondrichthyes
- Osteichthyes
- Actinopterygians
- Sarcoptergyians
Describe the Agnathans
- jawless fishes
- absence of paired fins
- notochord in larvae and adults - 7 or more gill pouches
- two chambered heart
Describe Hagfishes morphologically
- extant Agnathan
- vertebrates: embryos have neural crest
- craniate: 3-part brain in brain-case
- paired sense organs
- ventral heart with red blood
- no jaws
- long, thin body
- tail fin
- many pairs of gill pouches
- simple myotomes (not divided in D and V blocks)
- stiff fibre-sheathed notochord but no vertebrae
- many pairs of tidal gill pouches
- single nasal capsule
- only one semi-circular canal in statocyst
- no pepsin nor HCl in stomach
- segmental excretory funnels in trunk
- no paired fins
Describe Hagfishes ecologically
- Benthic marine scavengers
- rasping tooth-plates move apart-together to eat into dead fishes
Describe Myxine glutinosa
- hagfish
- can exude large quantities of mucus
- tie the body into a knot and run the knot either way along the body to escape or shed slime
Describe Lampreys
- extant agnathans
- long, cylindrical marine fish with vertebral structures.
- ectoparasitic on other fishes to which they adhere by suction
- rasp the flesh of their prey with oral tooth-plates.
Describe the morphology of lampreys
- disc-shaped mouth
- openings of gill pouches
- no paired fins
- dorsal fin
- 3-part brain in brain-case
- paired sense organs
- ventral heart with red blood
- cartilaginous incomplete vertebrae around the notocord
- many pairs of tidal gill pouches
- single nasal capsule
- only two semi-circular canal in statocyst
- myotomes not divided in D and V blocks
- no pepsin nor HCl in stomach
- segmental excretory glomeruli in trunk
Describe lamprey gill ventilation
tidal ventilation of the gill pouches allows the lamprey to remain attached and to breathe while rasping away with its muscular tongue, eating into its prey.
Describe lamprey gill morphology
- tongue at anterior end of pharynx
- gill epithelia
- common water tube separate from oesophagus
- tidal flow into and out of gill pouches
Describe the anadromous lifecycle of lampreys
- ascend rivers or streams
to breed (migration triggered by temperature) - males and females construct nest
- females lay eggs
- males fertilise
- larvae radically different from parents
- leave nest
- currents carry them downstream
- larvae burrow into mud
- spend a number of years as filter feeders
- metamorphosis produces parasitic juvenile
- adults live in oceans or big lakes
Describe the major stages in the evolution of fishes
- Basal stock: segments, no brain
- Craniata: brain, no vertebrae
- Agnatha: vertebrae, no jaws
- Gnathostomata: gill-arches –> jaws
- Chondrichthyes:
cartilaginous skeleton - Actinopterygians:
most fish - Osteichthyes
- Sarcoptergyians:
lobefins - Tetrapods
Describe the evolution of jaws
- major step in vertebrate evolution
- new feeding regimes: herbivory, predation
- manipulate objects (to build nests, grasp mates during mating, care for young etc.)
Describe derivation of the Gnathostomes
- duplication of the Hox gene complex
- paired fins (increased manoeuvrability)
- well developed lateral line
- 3rd semicircular canal in inner ear (better 3D orientation)
- more complex vertebrae
- ribs
- two nostrils
Describe the evolution of jaws
- Gnathostomes are very active with high metabolic demands
- derived feature = powerful mechanism for pumping water over gills
- mandibular gill arch evolved into protojaws: forceful ventilation.
- pharynx can be filled then emptied by spreading then compressing rays of the arches
Describe the agnathan condition
- pre-mandibular
- cranial nerves
- mandibular arch
- gilll arches
- notochord
- gill 9
- spinal cord
- gut
- no jaws
Describe the jaws of a dogfish
- jaw from mandibular gill arch
- cranial nerves
now associated ear with jaw
Describe detection of fluid movement
- neuromasts excited by bending in one direction; inhibited in the opposite direction
- e.g. in A, fasciatus
neuromasts
- basic displacement-sensitive cells
- present on the surface of all fishes
- kinocilium
- stereocilia
- superficial v canal
Describe superficial neuromasts
- naked
- set on the surface along the body
Describe canal neuromasts
- set in formal canals opening to the outside
- low-pass filter
lateral lines run along
either side of the spine
Describe statocysts
- craniate head contains paired statocysts in the inner ear
- statoliths (ossicles) give up-down information; displaced by acceleration.
- swirling in the semicircular canals; caused by angular acceleration
Describe Hagfishes’ statocysts
have a single semicircular canal
Describe lamprey’s statocysts
two
Describe Gnathostome (+ us) statocysts
three
Three paired canals allow
discrimination of rotational accelerations in yaw, pitch and roll axes as well as translational accelerations in any plane.
Describe Euthacanthus
- early Devonian acanthodian fish
- paired rows of spiny finlets between the pharynx and anus
Describe the Acanthodes (Perm.)
reduced to discrete paired pelvic and pectoral fins.
Describe the functions of fins
- locomotor functions
- non-locomotor functions
Describe the locomotor functions of fins
- increase manoeuverability and stability
- unpaired dorsal and anal fins control tendency to roll or yaw
- paired pectoral and pelvic fins control pitch and act as brakes
Describe Lionfish, Pterois volitans
- spiny fins used in defence
- evolve to inject poison when combined with glandular secretions
Describe the non-locomotor function of fins
- colourful
- used to send signals to potential mates, rivals and predators
- e.g. Apistogramma cacatuoides
Which forces act on fish while swimming:
DRAG
THRUST
Swimming modes associated with
- body or caudal fin swimming
- median or paired fin swimming
body or caudal fin swimming
achieves greater thrust and acceleration
median or paired fin swimming
Achieves greater manoeuverabilitity
Describe Anguilliform (eel) swimming
- wave passes backwards, increasing in amplitude
- travelling wave pushes water backwards
- push force generated increases from head to tail
- reaction force on the fish is equal and opposite to the “push” on the water generated by the wave
- thrust components summate but the sideways components (roughly) cancel out.
Describe the reaction forces of eels swimming
can be resolved into longitudinal thrust components and sideways components.
Describe Carangiform (trout) swimming
- amplitude of undulation is small at the head and large at the tail
- major forces are produced at or near the tail
- middle parts of the body do not contribute much to the thrust
Describe vortex generation and shedding
- swimming involves generation and shedding of vortices, forming a train
- a vortex has mass and velocity so, by Newton’s 3rd law, the fish swims
Describe Thunniform (tuna) swimming
- oscillation largely confined to the tail
- tall tail acts on a large volume of water
Describe propeller efficiency
- if the mass of water moved backwards by the fish is far larger than that of the fish, the water will move backwards slowly but the fish will move forwards rapidly
- because the tall tail acts on a large volume of water, “propeller” efficiency is high.
Describe the main forms of drag
- skin friction between fish and boundary layer (mucus, scale adaptations)
- pressures formed in pushing water (hence fish shape)
- energy lost in vortices formed around fins
Pressures in pushing water
- disc
- sphere
- teardrop
