Lecture 7_Teleosts

Review—Evolution and Phylogeny
Lecture 6b
Determining a Phylogenetic Tree—1
• Based on shared characters (traits)
– Internal or external
• Major derived characters (synapomorphies)—
large scale relationships
– Examples: physostomus vs. physoclistous, ctenoid
scales, thoracic pelvic fins
Determining a Phylogenetic Tree—1
• Secondarily derived traits—fine scale
– Typically many traits are examined
• Meristic counts and anatomical features
Determining a Phylogenetic Tree—1
Determining a Phylogenetic Tree—2
• Fossil record often used to determine ancestral
origins of major lineages
Determining a Phylogenetic Tree—3
• Gene sequencing and DNA fingerprinting
commonly used to determine relationships
• Molecular clocks—Genes used to determine
when major branch points occur
– Technique uses specific genes known to evolve at
a constant rate
• No selection pressure
• Genetic drift
Determining a Phylogenetic Tree—3
• Molecular clocks must be calibrated—example
– Branching point for birds and mammals  310 mya
• Extensive fossil record
– Hypothesis: all mammals are equally different from
any bird species, at this gene site
Class Actinopterygii
Class Sarcopterygii
Primitive Fishes Phylogeny Fish-like form
True teeth
Swim bladder
Originated 215 mya
> 26,000 species
Adaptations of jaws, fins, swim bladder, & skeleton
All possess_____ or ______ scales, mobile maxilla
bone, & ________ caudal fin
– Scales overlap like shingles  greater flexibility
Detached maxilla,
scales, homocercal tail
Leptocephalus larvae
Weberian ossicles
Physoclistous swim bladder
Protrusible premaxilla
Teleost Evolution: jaws & feeding
Premaxilla bone
Maxilla bone
Bowfin—non-teleost fish
Synapomorphy—jaw morphology #1
• Protrusible jaw
• Posterior connection of maxilla bone freed
• Swings forward
• Benefits?
Synapomorphy—jaw morphology #2
Pipette mouth—premaxillary
bone also freed
• Structure slides along
groove over skull
Pipette mouth advantage
• Increased suction power; more focused
Flow speed (m/s)
Gape & protrusion (mm)
– Tradeoff  gape reduction
– Ideal for small prey
• Attack speed also 
• Suction not always
• LMB almost 2x
Pharyngeal teeth
• Protrusion of jaws has tradeoff
– Maxillary bone not toothed in advanced forms
• Pharyngeal teeth well developed in many teleosts
– Gill arches, tongue, bones on roof of mouth
Moray eel—pharyngeal jaws
• Eels have weak suction power
– Swallowing prey more difficult
• Modified anterior gill arches
– Project forward to draw prey in
Moray eel—pharyngeal jaws
Herbivorous teleosts
• Almost all non-teleosts are carnivorous
• Most herbivorous teleosts in freshwater or on
coral reefs
– Feed on algae or aquatic plants
– Many temperate species are omnivorous
Herbivorous teleosts
• Plants  thick cell walls made of cellulose
– How do mammals overcome this?
• Herbivores have pharyngeal mills or gizzards
• Highly acidic stomachs & long intestines
– High intake, low assimilation
Paired fin placement and function
Pectoral fins
placed higher
Pelvic fins thoracic
Synapomorphies—paired fin placement
More primitive  pectorals ventral to gills; horizontal
– Paired fins for stabilization & braking, no spines
Derived  pectorals behind gills & vertical; pelvics thoracic
– Pectorals  maneuvering & thurst
– Pelvic fins  braking & stabilization
• Defense
Paired fin adaptations—more advanced teleosts
Dorsal fin
Two dorsal fins
Synapomorphy—Dorsal fin
More primitive  single, only soft-rays, less articulating
– Prevents rolling
More advanced  Two fins
– Anterior fin spinous and retractable
• Function—
– Posterior fin soft rays, articulating
• Function—
Dorsal fin adaptations—more advanced teleosts
Bone reduction occurred throughout
teleost evolution
• Vertebrate reduction— > 60 in elopomorpha 
< 30 in advanced forms
• Reduction in vertebral accessories (ribs)
• Fewer bones in skull and tail
• Scales reduced in size and thickness
Tetraodontiformes—four teeth
• Most derived and recently evolved group
– Originated 65 mya
– 360 living species—mostly marine
• Many bones fused or lost
• 16 vertebrae
• Premaxilla and maxillary fused
• Pelvic fins lost
• Scales modified into small spines or ossicles, or
bony plates
Many have adapted to previously unoccupied niches
– Diet of sponges, sea urchin, coral, jellyfish
– Some eat benthic or pelagic invertebrates
Fin swimmers—types?
Triggerfish and filefish—leatherjackets
• Make noise grinding teeth or drumming swim
bladder with pectoral spine-bone
• Locking dorsal spine
• Eyes move independent
“the fish that sews with a
needle and grunts like a pig
Puffers—fill stomach to puff up  3x volume
– Stomach may  volume 100x
– Causes spines to erect—diodontidae
• Freshwater species
• Viscera and eyes are toxic
– 2nd most toxic vertebrate
Fugu anyone?
Four species
• Mola mola  weigh > 4000 lbs.
• > 300 million eggs in larger sunfish  low ________
• Highest among vertebrates
• Much of skeleton cartilaginous—secondarily derived
• Feed on abundant jellyfish
• Common bycatch on driftnet and longline fisheries
Slender Mola

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