Three topics covered in this chapter?
- external anatomy
- skeletal anatomy
- tooth morphology
In terms of external anatomy what are some topics covered? (6)
- body design
- pitch, yaw and roll
- scales (not true scales)
- hydrodynamics
- sensory
- skin
Scales are modified what?
teeth derived from the skin
Body Design:
- Give a general description of the body shape
- Sleek, fusiform shape for most sharks, narrow caudal peduncle, streamlined tail with high aspect ratio ( fast swimming)
- large pectoral fins
- Large first dorsal fin
Body Design:
- Explain aspect ratio in terms of a fast swimming shark .
- length is long and narrow and very thin width for tail = high aspect ratio
Body Design:
- caudal peduncle ?
- a narrow one is seen in sharks that are fast swimmers!
Body Design:
- Pectoral fins originate ___ of the sharks centre of gravity and have _____ like cross section.
- forward
- hydrofoil-like ( flat on lower surface, convex on upper)
Body Design:
- Pectoral fins generate ___% of the sharks lift. They also carry heavy ___ and ___ stalling speed for___. They are also ____ for maneuvers.
- 25
- load
- low
- stalking prey
- flexible
- allows a shark to swim slowly without sinking
Body Design:
- what does the angle of the pectoral fin impact? (2)
- it impacts the sharks stalling speed and drag!
Body Design:
- Pectoral fins are used in ___ displays.
threat
l> down= annoyed…expect rapid burst of speed
L> straight out= mellow
Body Design:
- Pelvic fins can be ___ controlled.
finely
Body Design:
- Dorsal fins have a short what?
free rear trip (reduces turbulence from water…reducing drag)
L> provides stabilization from rolling and is dexterous
Body Design:
- Explain the leading and trailing edge of the dorsal fin!
- leading edge: straight edge
- trailing edge: curved in edge
Body Design:
- cartilage of a shark is reinforced with?
- calcium
Explain what yaw, pitch and roll are!
- Yaw: up and down
- Pitch: left to right via pectoral?
- Roll: side to side via nose
Body Design:
- Caudal fin can be deeply ____ and ___ aspect ratio. (maximum thrust with minimum drag)
- forked
- high
Body Design:
- lateral keel is present on some sharks and is located where?
- on tail…..for high speed sharks….reduces drag
Body Design:
- Second dorsal and anal fins are important because?
- they have pivoting base and long free rear tip and may help store laminar flow (resistance while moving through water) over posterior part of body.
Body Design:
- denticle bristling??
- when the scales are lifted from the body enhancing water flow…
Body Design:
- lamina boundary layer?
- straight…..not much resistance..boundary layer is fine.
- when the shark flexes it causes boundary layer separation which creates vortices from water flow…(via moving tale side to side)
- When denticle bristling occurs they hold the boundary layer in place enhancing water flow.
Body Design:
Shark scales are also called ____. What do they do?
- denticles
- reduce turbulence and enhance laminar flow.
L> reduces energy requirement as well. - smal grooves which enhance flow of water.
- keeps flow of water close to the body
Body Design:
Where are the most moveable scales located?
- mouth and the sides of the body.
Body Design:
- Explain the components of denticles.
- Enamel: outside portion of scale (spine)
- Dentine: inside of the spine
L> attaches to a basal plate - Melanophore: colour of scale
* pulp cavity
**dermis: melanophore and basal plate
Body Design:
Describe a short fin mako’s scales.
- they differ in size and flexibility all over the body.
L> shark controls the scales via skin
Body Design:
- Males of many species have clasper spurs which are?
- enlarged denticles that help anchor their intromittant organs inside the female’s vent during copulation
Many skates have bucklers, describe them. Also explain malar and alar which male skates have.
- they are enlarged thorn like denticles covering parts of the body..
- spines that are hook like structures which they use to hang onto the females during courtship and matting.
Aside from the previous benefits mentioned about sharks hydrodynamically sculpted denticles what is another benefit? Also compare them to scales seen on teleosts.
L> also describe it in terms of as a side effect benefit.
- stealth
- the large overlapping scales of teleosts are not nearly as hydrodynamically clean as the dermal denticles of sharks.
- If you were to place the same hydrophone near a cruising shark, no such swimming sounds would be heard. Sharks are literally silent hunters.
L> this hydrodynamic-side effect confers tremendous advantages for great whites when stalking prey since the helpless fish or sea lion almost never hears the shark that caught it.
Hydrodynamics:
- Water is __ or more ___ (resistant to flow) than air. As a result, water ??
- denser
- viscous
- does not move easily around a moving body
Hydrodynamics:
- Drag????
- an unavoidable consequence of living in the aquatic environment and may be defined as resistance to moving through a fluid.
Hydrodynamics:
- Boundary layer??
- layer of fluid that sticks to and is carried along with the surface of a moving body CREATING DRAG.
Hydrodynamics:
- Drag increases with what four things?
- speed
- fluid density
- object size
- shape
* *sharks bodies are usually designed in such a shape that reduces drag…streamline
Hydrodynamics:
- the key to understanding drag is the distinction between what two things?
- Turbulent
2. Laminar flow
Hydrodynamics:
- Turbulent?
- turbulence is a form of fluid flow in which the molecules of the fluid move over a surface in irregular paths resulting in the exchange of momentum from one portion of the fluid to another. (this equals= higher drag)
Hydrodynamics:
- Laminar flow??
- laminar means in layers.
- this is referring to fluid flow in which the molecules of a fluid move over a surface in discrete layers without fluctuations, so that successive particles passing the same point have the same velocity.
Hydrodynamics:
- Explain laminar flow in terms of energy.
- A smooth laminar flow is more efficient than and thus preferable to a turbulent flow.
- ** laminar: water moves faster in the centre vs sides.
- ** turbulent flow: water moves slow because it is on the sides.
Hydrodynamics:
- what is the simplest way to achieve minimum drag?
- through streamlining
Hydrodynamics:
- explain a streamlined shape.
- it is longest in the direction of travel and tapered on both ends.
- but optimizing laminar flow is not as simple as one would imagine.
Hydrodynamics:
- Theoretically the optimal shape for streamlining is?
- has its maximum diameter at the anterior third of the object with ratio of length to width of 4.5(most common)
- max diameter = 1/3 down the body…which is the most hydrodynamically favoured shape.
L> this is usually where the dorsal fin is found!
Hydrodynamics:
- Amongst the fishes which is closest to the theoretical hydrodynamic shape??
- Tuna
As the length of the shark increases the fitness ratio _____. Explain.
- increases
- the longer it is the more streamline it will be and therefore the less drag it will produce
- more torpedo shaped…
Which has a better fitness ratio: Adults vs pups.
- Adults
Lift:
- The essence of lift is?
- suction
Lift:
- Bernoulli’s principle??
- a foil with a curved upper surface moving through a fluid medium causes the fluid to move faster over the upper surface than the lower; this greater speed creates a negative pressure (suction) above the foil.
Lift:
- angle of attack??
- the plane of a foil relative to the long axis of the body to which it is attached.
Lift:
- The greater the angle of attack??
- ## the more both lift and drag (which operate at right angles to one another) increase.
Lift:
- When does stalling occur?
- this occurs when laminar flow separates from the surface of a foil. The speed at which this occurs sic allied the stalling speed and varies with the size and shape of foil.
Sensory:
- Lateral line system?
allows sharks to locate prey over long distances via sensing low frequency vibrations using mechanoreceptors including neuromasts.
Sensory:
- components of lateral line system?
- surface pore between denticles
- tubule which is open to sea water
- lateral line canal
- neuromasts pertruding into the canal….
L> attach to nerves - gelatinous dome encases the neuromast.
Sensory:
- Ampullae of Lorenzini?
- electroreceptors that are found mostly on the head region of the shark which are used to guide them to their pretty by detecting the weak electric fields from animals and possibly temperature, water pressure and salinity.
- arrangement of these is just as unique as the scales on a shark…identification method!
Skin:
- Beneath the ___ skin of sharks, lurks yet another feat of hydrodynamic engineering. What is it?
- sandpapery
- The inner, thickest layer of a sharks skin is a white sheath of fabric composed largely of a very touch, rather springy protein called collagen.
Skin:
- collagen??
- the major fib ours constituent of skin, tendon, ligament, and bone and is probably the most abundant protein in the Animal kingdom.
Skin:
- Collagen
L> It is very elastic in sharks and is in sheets surrounding the shark like a?What is directly related to this?
- corset
- speed
Skin:
- Collagen:
L> It’s springiness is responsible for?(kangaroos)
- much of the energy recovery in the achilles tendon of kangaroos, enabling these outback bounders to hop farther than they could powered by muscles alone.
Skin:
- Collagen:
L> It owes its wonderful properties to ?
- its structure
L> triple stranded helical coils that are bound together to form fibrils. These fibrils in turn lie in helices around a sharks body..left to right.
Skin:
- Collagen:
L> Its alternating layers the collagen fibrils describe right and left handed helices. These helices are arranged along the body at?
- various angles to the long axis of the shark (from 90 degrees behind the skill to nearly 0 in the caudal fin)
Skin:
- Collagen:
L> the collagen corset provides??
- These sheaths of collagen form kind of a corset /firm anchor for swimming muscles to attach to and the skin acts as sort of an external skeleton which increases muscle efficiency.
- *ensures lift
Skin:
- Collagen:
L> In Lemon Shark ( Negaprion brevirostris) it was found that the muscle attachments to this collagen corset act as?
- found that the muscle attachments to this collagen corset act as a collective external tendon promoting more efficient transmission of muscular force to the tail.
Skin:
- Collagen:
L> Explain changes in the angle of collagen fibrils during swimming
- they prevent tension loss or skin wrinkling on the concave side of the shark thereby maintaining the bodes internal pressure.
L> therefore muscular energy invested by a shark towards flexing its body during swimming is transmitted rearward and largely recovered by the snap of this collagen corset especially near the caudal fin where it can contribute most forcefully toward propulsion.
Skin:
- Collagen:
- when a shark turns there is no?
creasing/overlap of skin bc the collagen prevents this
Palaeontologists Wolf- Ernst Reif and David Weishampel published a paper describing the anatomy and mechanics of the crescent shaped tail in lamnid sharks. In this paper they confirmed what ?
- that the skin is the most important attachment site for shark swimming muscles and among other things described the tendons that transmit muscular energy from the tail stalk to the tail via the lateral keels.
Palaeontologists Wolf- Ernst Reif and David Weishampel found what about the lateral keels of a lamnid shark?
- they serve as a kind of pulley system, adding the elastic snap of collagen to the tail lashing power of the posterior trunk muscles.
Palaeontologists Wolf- Ernst Reif and David Weishampel found that lateral keels serve as a kind of pulley system, adding the elastic snap of collagen to the tail lashing power of the posterior trunk muscles. This may explain why even a small to medium sized short fin mako can do what?
- break a fisherman’s leg with a single tail wallop and how this species can repeatedly leap up to 20 feet ( 6 meters) out of the water.
The great white is also known to leap out of the water on occasion especially when?
- it is in the pursuit of a speedy prey, so this energy efficient tendon (lateral keel) system may give this paramount predator the kind of propulsive edge it needs.
Certain parts of a sharks cartilaginous skeleton is reinforced by what?
- calcium salts
L> jaws, pectoral girdle etc
Is a sharks jaw attached to the skull?
no
- this is why it shoots forward
What makes up a sharks jaw??(5)
Mandibular arch:
- Palatoquadrate arch(upper jaw)
- Meckel’s cartilage (lower jaw)
Hyoid arch:
L> Ceratohyal (ventral) –> lower jaw portion
L> Hyomandibula( dorsal..closer to spine) –>
upper jaw portion
L> Basihyal: end of ceratohyal
What are the cartilaginous structures that collectively make up the sharks ‘skull’ called?
- Chondrocranium
Skates and Rays:
- head region is called?
- Neurocranium
Skates and Rays:
- upper jaw?
- lower jaw?
- Palatoquadrate arch(upper jaw)
2. Meckel’s cartilage (lower jaw)
Shark tooth terminology:
1. Labial Surface?
- outer…towards the cheek.
L> faces out from the mouth
Shark tooth terminology:
2. Lingual surface?
- inner
- towards tongue
- faces into the mouth
Sharks have ___ row(s) of teeth.
multiple
What are the three basic types of teeth found in sharks?
- Slender, awl-like grasping teeth ( as in short fin mako and sand tiger)
- Blunt, mosaic-like crushing teeth
- Triangular blade like teeth
The cowtail stingray and atlantic stingray both have what kind of teeth?
- crushing teeth!
Basking shark has how many rows of teeth??
-5
Basking shark teeth description.
- less than a cm long
- not used for food/prey
- maybe for mating since skin is so tough?
Describe the components of a shark tooth!
- Crown = height of the tooth to the cusp.
- Cusp= base of the crown
- Base= underneath the cusp
What can we estimate from anterior tooth length of a shark?
- length of the shark…..
Symphysial bars?
- where the right and left parts of the jaw meet
L> tooth here in the center= symphysial tooth
Describe the distribution of teeth in a sharks jaw.
- Larges= anterior
- Slight change in size from anterior=Intermediate teeth
- Smaller than the anterior (middle sized teeth)=Lateral teeth
- Smallest teeth out of all of them present on the jaw =Posterior
What is the dental formula of a great white shark?
2A, 1Int, 5L, 4P/ 3A, 5L, 3P
Like the dermal denticles from which they are derived, shark teeth are ___, ___ and ___ continuously throughout life.
- grown, shed and replaced
Are the teeth in sharks firmly attached or loosely attached?
- loosely via a membrane inside the jaw and not set firmly into the jaw like most vertebrates nor in the cum tissue itself.
As each tooth grows and develops what happens to the membrane?
- it is pushed forward by replacement teeth developing.
Describe replacement teeth in comparison to the original functional teeth prior.
- each replacement tooth is slightly larger than the one before it as though keeping up with the sharks overall growth.
In most sharks including GW teeth are produced and shed ___. Exception?
- individually.
- exception: Cookie cutter shark… ( Isistius brasiliensis)
L> a small species notorious for biting plugs of flesh from large pelagic fishes and cetaceans… the interlocking lower jaw teeth and shed and replaced as ONE UNIT. (same as upper) - This ensures a saw like dentition at all times.
L> usually when eating they only take out the blubber layer.
The rate of tooth replacement varies with what factors?
- water temperature
- if the tooth is upper or lower
- age
- feeding habits
- and species
Tooth replacement rate has been measured in only a few species ranging from - days per row. (functional row).
9-36
L> this is why teeth fossils are so abundant.
In general _ water temperature plus ___ of the shark = lower teeth replacement rate.
- colder
- older age
Which is faster: upper jaw teeth replacement or lower?
- upper! due to differences in the way each is used during feeding.
Describe feeding with GW in terms of teeth.
- vigorous side to side head shaking employs when tacking large prey maximizing the efficiency of the saw like cutting edge of the broad upper teeth. Bc of this action it imposes greater wear and tear on the upper teeth vs lower. Therefore a faster replacement rate is needed for upper.
