Feeding morphology Flashcards
Factors that affect morphology of feeding (4)
- Jaw protrusion
- Pharyngeal Jaws
- Dentition
- Mouth position
- Diet in many fish can be predicted by _____
body shape, mouth position and jaw shape, and dentition
what is thought to be key innovation in the fish evolutionary tree
Jaw protrusion
Jaw protrusion is most common in which kind of fish?
most common in higher
Teleost:
- cichlids,
- clupeids
- percids
- centrarchids
- labrids
jaw protrusion
- Creates suction that can pull in prey from as far away as 1⁄2 - 3⁄4 head lengths away
Extremely high suctions by Venturi effect (creating vacuum)
Faster than swimming and can increase
attack speeds by up to 40%
Jaw protrusion phases
- Preparatory phase
- Expansion phase
- Compression phase
- Recovery phase
Jaw protrusion Preparatory phase (1)
– Buccal cavity pressure increased resulting from inward squeezing suspensorium (cheeks and gills), and raising mouth floor (tongue)
Jaw protrusion expansion phase (2)
Lower jaw depressed, premaxilla protrudes, suspensorium expands and mouth floor lowers creating high negative pressure or vacuum suction
Jaw protrusion compression phase (3)
Pressure increases as mouth closes, bones move back into position while opercular valves open to release water under high pressure out of opercular opening (over the gills)
Jaw protrusion recovery phase (4)
Bones, muscles and pressure in the buccal cavity returns to pre- preparatory conditions
Fish jaws types
In non-protractible jaws
* Muscles work to expand buccal and opercular cavity and raise
the cranium
* Pulling mandible down pulls on the premaxilla via attachments to the maxilla
In protractible jaws
* As above, but premaxilla slides down a rostrum creating
longer narrower tube
* Elongated tube and negative pressure creates Venturi effect and thus strong suction
Jaw protrusion patterns are based on what?
More than 8 different patterns based on:
- gape size,
- biting force,
- amount of protrusion
also 4 different pathways for mouth protrusion**
Pharyngeal jaws
Moving water back to gills pushes food back to pharyngeal area
* In many Teleost (derived fishes), pharyngeal basket developed into extra jaws including teeth
* These fishes are called pharyngognathous
* Lower jaw formed from paired 4 - 5th ceratobranchial
(often fused)
* Upper jaw formed into dermal plate attached to epibranchial bones (top of gill arches)
* Induce secondary gape limitation
How do pharyngeal jaws affect a fishes diet?
pharyngal jaws occur in very back of mouth (where closing looks in picture), mouth used to catch fish, pharyngeal jaws used to process.
this affects what a fish can eat because prey must fit in mouth and fit in pharyngel jaws; two factors
Pharyngeal jaws purpose and shape
- Serve to direct, reposition, crush and disarticulate food
- Have teeth that vary by species but also by individuals
within species (see dentition next) - Different species have different shape, size and dentition of pharyngeal jaws
- Different pharyngeal jaw shapes in neotropical cichlids from geometric morphometrics analyses
Dentition
Teeth arranged in one to several rows or patches
* Sometimes pointed and canonical (e.g., wolfish) , other times triangular and sharp and
serrated (sharks and piranhas)
* Teeth can also be modified into flattened plates arranged like paving stones for crushing (e.g., rays and some sharks)
* Which prey is targeted often predictable by teeth type
Dentition
In bony fishes (teleosts)
Teeth are continuously replaced, sometimes in blocks or rows
highly variable with some families and species with no teeth (e.g., sturgeon), to several tooth spiked bony plates (e.g., monkfish)
can also be hinged (e.g., pikes and hakes), where teeth can bend inwards when passing prey but spring back by elastic ligaments to prevent escape
Dentition types
Caniniform teeth
Villiform teeth
* Cardiform teeth
Molariform teeth
Beak-like
Caniniform teeth
- Recurved with sharp points
- Serve to hold and grasp prey (e.g., Tigerfish - Hydrocynus
vittatus) - Especially useful to subdue struggling prey (in piscivores)
Villiform teeth
-common for small fish
- Numerous small needle-like teeth,
- In surface-dwelling or benthic predators (e.g., pike, lizardfish)
- Like sand paper – helps grasp prey into buccal cavity (piscivores, zooplanktivores, insectivores)
Cardiform teeth
- Fine pointed teeth arranged closely together (e.g., Snook,
Largemouth bass, billfishes - Tunas) - Typical in chase down and swallow-whole predators - Mostly designed to reduce escapement
Molariform teeth
- Pavement / molar like flattened crushing teeth
- For hard prey items like gastropods, molluscs, sea-urchins, etc.. (e.g., horn shark, freshwater drum)
Beak-like
- Teeth closely packed incisor types forming a beak (e.g.,
parrot fish) - Can be fused or separated
- Typically accompanied by hard molariform teeth more posteriorly
- For hard prey / food items such as coral and encrusted prey like barnacles etc.., (e.g., triggerfishes)
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Gillrakers
Cartilaginous projections pointing inward and forward along the inner edge of gill arch
Highly heritable trait in many fish types (e.g., coregonids, cichlids, gasterosteiformes, etc,..)
Structures that aid in capture and retention of engulfed prey
Gillrakers in coregonids study
- In lakes with 1 species, LSR fish with gill raker average numbers 18-34 found in all depth zones
- In lakes with 3 species, Gill rakers averages by zones are very different
Gillrakers in coregonids study results
proof theres a link in food, habit they use, and gill rakers since different types of fish in different zones had different gill raker average numbers
Mouth Positions
Terminal mouths
Superior mouths (supraterminal)
Inferior mouths (subterminal)
Suctorial mouths
Terminal mouths
- body terminates in mouth where upper and
lower jaw align - Chasers / filterers / siphoners
Superior mouths (supraterminal)
- lower jaw extends more anterior than upper
- Good for feeding on surface prey capturing from underneath
Inferior mouths (subterminal)
- upper jaw extends more anterior than lower
one - Feeding by either picking or scraping
Suctorial mouths
- Designed for sucking / scraping surfaces in high energy environments
Combined locomotory and feeding morphology
Mouth and feeding morphology and overall body shape morphology outline much of the functional features or functional morphology of fishes
Can be used to make important inferences on typical feeding types or guilds among fishes and help understand the ecology of given species
Also allows a better understanding of how fish use their environments and what features in those environments have likely shaped the fish’s evolutionary history
Feeding types
Zooplanktivores
- Small streamlined torpedo shaped bodies
- Terminal and protractible mouths forming a funnel
- Forked tails, with high aspect ratios (AR) for fast and sustained swimming
- Mostly lacking in significant teeth
- Many thin long, tightly packed gill rakers
ex; herring, mackerel
Feeding types
Lurking ambush piscivore
- Elongate (tube-like) bodies
- Long jaws with many sharp projecting teeth to
grab and hold prey - Broad tails with mid-level AR for fast burst pushes
- Posteriorly placed median fins set far back
- Reduced gillrakers,
ex; pike, barracuda
