What topics are covered in this section?(3)
- Muscle System
- Internal Organs
- Nervous System
Muscle Anatomy:
Sharks are comprised of about _% muscle tissue whereas humans are 35%.
85%
Muscle Anatomy:
- Most sharks are comprised of white muscle fibres up to _%.
90%
Muscle Anatomy:
- Function of white muscle?(vs red)
- burst activity
- less stamina
- Different physiological makeup vs red muscle
L> less mitochondria
L> less oxygen binding myoglobin
***aka rapid speed but not for long duration = white muscle
Muscle Anatomy:
-Lamnid sharks and a few other sharks, possess a band of what?
- Dark red muscle that runs along the flanks just under the skin
Muscle Anatomy:
- Red muscle has substantially greater __ than white. Give some characteristics.
- stamina
- more oxygen binding = red
- more mitochondria
- heat generation
**mostly runs in the core of the animal
L> core temp in here = 77 –> keeps organs warm
L> outer band of muscle matches the outside water temp
Muscle Anatomy:
- From opportunistic dissections of Porbeagle, Salmon, Shortfin mako, and white sharks, researchers have noted that the length of this band of dark muscle what?
- varies greatly among the various genera
L> variation in length of red muscle band…which conveys different swimming abilities
Muscle Anatomy: -Describe the differences in red muscle length etc in the following sharks : A. Salmon shark B. Mako C. Thrasher GW?
- All: bodies are stiffer!
L> short length of red muscle band= more stiff
Salmon>Mako>thresher (longest band) - Thresher is the most flexible of the three….its tail is very flexible and powerful bc of red muscle in the tail!
- swim with rigid body
*more energy efficient - GW: has a longer red muscle band than salmon and mako…almost to casual bedunkle
Muscle Anatomy:
- Studies indicate that as ___ increases ____ red muscle mass also increases.
- body mass increases
Muscle Anatomy:
- Porbeagle and salmon sharks (genus Lamna) typically have a very long/short band of muscle along their flanks.
- short
* * Shortfin makos are somewhat longer and those of the white shark (Carcharodon) are the longest of all
Muscle Anatomy:
- Given red muscles stamina, the White Shark’s less stiff bodied swimming style compared wit other laminas may be due to what fact?
- that it has the most extensive band of red muscle along its flank
Muscle Anatomy:
- Short red muscle = what?
- more stiff body but the swimming style is faster because they do not lose much energy and it is focused in the tail! BUT longer red muscle = more flexible
Muscle Anatomy:
- This marriage between muscle form and swimming function may result in significant what?
- advantages to the white shark
Muscle Anatomy:
- White Sharks:
- If the benefits of stiff bodied swimming comes at the cost of reduced maneuverability the development of what may partially off set that balance?
- the development of a more sinuous propulsive stroke (not that flexible but has a lot of force! )
- As such the white shark may be more maneuverable than its lamnid cousins
Muscle Anatomy:
- The ability to develop a more sinuous propulsive stroke may lead to what advantages?
- predatory advantages when pursuing swift and agile prey such as seals and sea lions
Muscle Anatomy:
- The ability to develop a more sinuous propulsive stroke may lead to predatory advantages when pursuing swift and agile prey such as seals and sea lions. If this is true than the great white has struck a highly what?
- beneficial compromise between the limitations of its body form and the adaptability of its red muscle band.
Muscle Anatomy:
- Shark swimming muscles like those of most fishes are composed of what?
- W shaped blocks called myotomes
L> interlocked so muscle contraction moves in a wave…collagen around them enhances force of contraction!
Muscle Anatomy:
- Myotomes interdigitate in complex ways, with some parts of an individual muscle block ____ and others ____ to form a series of ___.
- extending forward
- back
- intermeshing cones
Muscle Anatomy:
- The intermeshing cones formed from myotomes generates what?
- a body wave that propagates smoothly and sinuously along the body and with the addition of a caudal fin produces the vast majority of a sharks propulsive force.
Muscle Anatomy:
- In a cross section, shark swimming muscles form?
- bundles of concentric rings that meet at the midline of the body underneath the lateral line.
L> there is a rich network of capillaries in red …lots of oxygenated blood!
Why should you not hold a shark by the tail?
- only support for organs = collagen mesh and it can break loose very easily!
Muscle Anatomy:
- The muscle bundles that are above the lateral line are called what? Those below?
- epaxial (back)
- hypaxial (flank)
Muscle Anatomy:
- The arrangement of muscle fibbers in a shark is quite different/similar to that of a teleost.
different
Muscle Anatomy:
- Whereas in a boney fish, muscle fibers tend to loop back on themselves, in sharks the muscle fibers?
-they attach to tough longitudinal struts composed of connective tissue. These struts may act as an auxiliary muscle attachment point along the flanks compensating for shark’s lack of ribs.
Muscle Anatomy:
- Other muscles control the sharks fins via?
- raising, lowering and flexing these foils to control every aspect go swimming
Muscle Anatomy:
- In conditions under which it is difficult to breathe some sharks ___ or ____ their gill slits to move oxygen bearing water over their gill membranes.
- flare
- rhythmically pump
Internal Anatomy:
- What topics are covered in this portion?(7)
- heart
- liver
- stomach
- spleen
- reproductive organs
- kidney
- gills
Internal Anatomy:
- Heart:
- In sharks how many times is the blood pumped as it makes its passage to the gills and then through the systemic circulation before coming back to the heart.
once
Internal Anatomy:
- Heart:
- What are the four parts of a sharks heart?
- Ventricle
- Atrium
- Conus Arteriosus
- Sinus venosus
Internal Anatomy:
- Heart:
- Ventricle?
- muscular thick walled chamber that pumps the blood
Internal Anatomy:
- Heart:
- Atrium??
- thin walled, stretchy chamber that receives the deoxygenated blood before it passes into the ventricle
Internal Anatomy:
- Heart:
- Conus Arteriosus
- receives blood pumped from the ventricle. Contains valves that prevent back flow of blood. This chamber apparently helps even out the blood pressure coming from the heart.
Internal Anatomy:
- Heart:
- Sinus venosus?
- Collecting area that empties deoxygenated blood into the atrium via ONE vein!!!!! (in other fish there is usually TWO)
Internal Anatomy:
1. Heart:
-Ventral aorta?
L> also blood flow?
- large artery that receives blood from the heart. The blood flow goes: Atrium—> ventricle—->conus arteriosus—>ventral aorta. The ventral aorta branches into two main arteries that carry blood to the gills.
Internal Anatomy:
- Heart:
- Gills??
- perform gas exchange, aided by the countercurrent flow of blood and water and by the large surface area and short diffusion distance. In addition to gas exchange, gills also perform important roles in eliminating excess ions and nitrogenous waste and in regulating pH.
Internal Anatomy:
- Heart:
- Spleen??
- functions in producing and maturing some kinds of blood cells
Internal Anatomy:
- Heart:
- dorsal aorta?
- carries OXYGENATED blood from the gills to the systemic circulation.
Internal Anatomy:
- Heart:
- Afferent branchial arteries?
- carries deoxygenated blood from the ventral aorta to the gills to be oxygenated!
Internal Anatomy:
- Heart:
- Efferent branchial arteries??
- carries oxygenated blood from the dorsal aorta to the rest of the sharks body.
Internal Anatomy:
- Red blood cell production is performed by the ___, special tissue around the ___ and in at least one species it is also produced by a special structure called the _____.
- spleen
- gonads
- Lydig’s organ
L> located around esophagus
Internal Anatomy:
- In those species in which it occurs, Leydig’s organ is nestled along the top and bottom of the ?
esophagus
Internal Anatomy:
- The leydig’s organ can be quite____ a _ kilogram (_pounds) one was reported from a 1.8m (6 foot) long Bluntnose six gill shark( Hexanchus griseus)
large
- 6kg
- 5 pounds
Internal Anatomy:
- Liver:
L> It performs several functions related to ___ and ___.
- digestion and absorption
Internal Anatomy:
- Liver:
L> It performs several functions related to digestion and absorption:
- Produces ___ to aid in fat digestion.
bile
Internal Anatomy:
- Liver:
L> It performs several functions related to digestion and absorption:
- Helps control ___ level.
sugar
Internal Anatomy:
- Liver:
L> It performs several functions related to digestion and absorption:
- In addition, the livers of sharks also help to regulate ____ for swimming.
- buoyancy
Internal Anatomy:
- Liver:
L> It performs several functions related to digestion and absorption:
- In addition, the livers of sharks also help to regulate buoyancy for swimming. Explain.
- They regulate buoyancy largely by storing squalene, a low density hydrocarbon. Containing large amounts of squalene, the liver becomes less dense than the surrounding seawater, making it easier for the shark to avoid sinking like a stone.
Internal Anatomy:
- Liver:
L> Sharks have ___ livers in relation to body size.
large
Internal Anatomy:
- Liver:
L> Sharks are generally ___ than water
denser and must do some work to avoid sinking.
Internal Anatomy:
- Gallbladder?
- stores bile produced by the liver before it is delivered to the duodenum via the bile duct.
Internal Anatomy:
- bile duct?
- carries bile from the liver to the duodenum
Internal Anatomy:
- Hepatic portal vein?
- carries blood from the intestine and spleen to the liver.
Internal Anatomy:
- The size of a sharks liver may be key to the sharks what?
length
Internal Anatomy:
-What is the common name for Cetorhinus maximus?
- Basking shark
Internal Anatomy:
- The basking shark has an elongated body cavity filled with an enormous what? %%??
- oily liver which may comprise some 20-25% of its total weight
- *can cruise the water column fairly easily because of the oil!
Internal Anatomy:
- The great white has a smaller/larger liver in comparison to the basking shark?
- smaller
- 12% of the total body weight = liver
Internal Anatomy:
- In general there is an ___ relationship in sharks between activity level and liver size.
inverse
Internal Anatomy:
- In general there is an inverse relationship in sharks between activity level and liver size. Thus the white sharks relatively small liver is consistent with its ___ life style. What of the basking shark?
- active lifestyle = small liver
- it is a slow swimmer at surface (filter feeder) = larger liver
Internal Anatomy:
- Deep sea sharks ( those living in ocean depths of 300 to 1500m) have especially large reserves of????Why???
- squalene since their livers comprise 1/3 of the weight of the entire animal
L> may enhance oxygen binding
L> may produce more of a lift as such deep pressures
ex: frill shark
*** NOT 100% SURE WHY THEY HAVE THESE HIGH LEVELS HONESTLY BRAH.
Internal Anatomy:
-Digestion and Absorption:
L> Main region of the Stomach?
- the main region also called the cardiac region of the sharks stomach is muscular and stretchy with thick folds
Internal Anatomy:
-Digestion and Absorption:
L> Stomach:
- Pylorus?
- the food passes from the main region of the stomach into the lower pyloric region. At the downstream end of the pyloric region, there is a pyloric sphincter that regulates the passage of chyme (partially digested food) into the intestine.
Internal Anatomy:
-Digestion and Absorption:
L> Pancreas??
- secretes digestive enzymes into the stomach ( this is a little different from mammals, in which pancreatic enzymes are secreted into the duodenum).
Internal Anatomy:
-Digestion and Absorption:
L> Duodenum?
- the first part o the intestine in which much of the digestion occurs
Internal Anatomy:
-Digestion and Absorption:
L> Intestine??
L> at first glance what is an issue with it? Solution?
- Sharks have short intestines. At first glance the intestine doesn’t seem long enough to provide adequate surface area for absorption. However, inside the valvular region of the intestine, there is a spiral valve (similar to a spiral staircase) that provides additional surface area and slows down the passage of food.
Internal Anatomy:
-Digestion and Absorption:
L>How many types of intestinal valves are there?
three
Internal Anatomy:
-Digestion and Absorption:
L> What happens to food that cannot pass through the sharks intestinal valve?
- the shark inverts its to mach and passes out food it cannot digest.
Internal Anatomy:
-Digestion and Absorption:
L> What are the three types of intestinal valves?
- Spiral valve
- Scroll valve
- Ring valve
Internal Anatomy:
-Digestion and Absorption:
L> Scroll intestinal valve?
- resembles a loose roll of paper (ex: lemon shark)
Internal Anatomy:
-Digestion and Absorption:
L> Ring intestinal valve?
- resembles a tightly packed lamellae ( plates)
(ex: lamnoids….such as white sharks) - food has to pass through each valve/stack…very slow passage! they only eat every four days! …this increases absorption
Internal Anatomy:
-Digestion and Absorption:
L> Spiral intestinal valve?
- resembles a spiral stair case
L> rings basically going down the shark
**see ppt if confused on what it looks like
Internal Anatomy:
-Reproduction:
L> Testes?
- they are internal and located in the anterior end of the body cavity within the epigonal organ (part of the immune system–> helps with blood cell production)
Internal Anatomy:
-Reproduction:
L> The urinary and reproductive tracts join together to form what?
- the urogenital sinus
Internal Anatomy:
-Reproduction:
L> From the urogenital sinus the sperm is eventually released into the groove of the ____ and is delivered to the female during copulation.
- claspers
* *why two claspers? no clue..they only use one during copulation
Internal Anatomy:
-Reproduction:
L> What are the three types of testes in elasmobranchs?
- Radial testes
- Diametric testes
- Compound testes
Internal Anatomy:
-Reproduction:
L> 1. Radial Testes?
**who is this seen in?
- found in the basking and lamniform sharks, are enclosed in the epigonal organ and the cells that will eventually become sperm begin development at the center of the lobe and proceed to the outer edge for further transport.
* ** radiate out from the core to the outer regions!
Internal Anatomy:
-Reproduction:
L> 2. Diametric Testes??
**found in which elasmos??
- These protrude from the surface of the epigonal organ and the developing cells transport from wall to wall.
* * found in requiem sharks of the family carcharhinidae !
Internal Anatomy:
-Reproduction:
L>3. Compound Testes??
- Shows a little of both of the diametric and radial testes arrangements
L> found in most bastiods typically
Internal Anatomy:
-Reproduction:
L> Which test is often larger?Also seen in?
- the right is often larger than the left
L> right may be used more?
**this is also seen in ovaries !
Internal Anatomy:
-Reproduction:
L> The left ovary in most elasmos is?
reduced and produces few or perhaps no eggs
** weight saving mach to have more room for the liver possibly?? No clue.
Internal Anatomy:
-Osmoregulation
L> Rectal gland?
- concentrates salt ions ( particularly Na+ and Cl-) in the urine before the urine is eliminated via the cloaca.
Internal Anatomy:
-Osmoregulation
L>Kidney?
- eliminates excess water and salts but very little urea. Urine passes from the kidney to the rectal gland
- urea is concentrated in the tissues of the shark to help with osmoregulation …slightly hypo osmotic to the environment .
Shark Nervous System:
- Does it vary across all species?
yep
Shark Nervous System:
- Cerebellum controls a lot of??
- a lot of primitive functions
Shark Nervous System:
- Sharks and rays vary in the ___ and ___ of their brains.
- size
- structures
Shark Nervous System:
- Some organisms such as the squaloid sharks, have ___ brains, while those of others, such as makos, grey sharks (tiger sharks), hammerhead sharks and great white sharks, have much __ brains.
- small
- larger
Shark Nervous System:
- While many sharks have brain size: ___ ratios which are similar to bony fish, other posses ratios observed in ?
- body
- mammals and birds
Shark Nervous System:
- why is larger brain needed?
- to meet the needs of a larger body….it requires more brain power to man everything
Shark Nervous System:
- What is the body to brain size ratio called?
- Encephalization quotient
L> takes brain and body size and scales it to proportions of other animals for similar scale. (aka compares it to what it should be based on other organisms similar to it)
Shark Nervous System:
- Among sharks and rays the encephalization quotient can range from __ to__.
0.25(smaller than that expected for an animal of that size) to 2.77(larger than that expected of animal of that size)
Shark Nervous System:
- If the ratio of the telencephalon size to body size is determined , some rays have a value __ that of Squalus and hammerhead sharks have a value __ that of Squalus. Other brain areas have been observed to vary in size.
- 9x
- 5x
Shark Nervous System:
- General description of make up of nervous system
- Olfactory sac
- olfactory tract
- Forebrain
- Midbrain
- Cerebellum
- Hindbrain
Y shaped…..tips to bottom in that order
Shark Nervous System:
- Cerebrum?
controls voluntary actions (part of bran more separated up front)
Shark Nervous System:
-Cerebellum?
(brain-like brain) motor control and movement
Shark Nervous System:
-Medulla ?
(off spinal cord) cardiac, respiratory, autonomic functions
Shark Nervous System:
- Midbrain?
relay information system for the auditory, visual, and motor systems of the body.
Shark Nervous System:
- hindbrain?
-the hindbrain processes most sensory information and moves the head
Shark Nervous System:
-Olfactory bulbs and tract?
the sense of smell
Shark Nervous System:
- Hammerhead has what brain regions present?
- Cerebrum
- Cerebellum (largest)
- Medulla
- Olfactory bulb and tract
Shark Nervous System:
- Ray has what brain regions present?
- reduced cerebrum
- slightly larger midbrain in comparison to the Mustelus canis
- reduced medulla (smallest of the three elasmos looked at )
- olfactory bulbs are smaller than the other two examined
- smallest cerebellum of the three
Shark Nervous System:
- smooth dogfish has what brain regions?
- Midbrain (smallest vs ray)
- Cerebellum = larger than hammer
- medulla= smaller than hammer but larger than the ray
- cerebrum severely reduced
- olfactory bulbs are larger than ray but smaller than hammer
Shark Nervous System:
- How many pairs of cranial nerves do they have?
10 pairs
Shark Nervous System:
- What does the brain size portions of the hammerhead and dogfish shark show?
- hammer head = active predator <- larger cerebrum and cerebellum
- dogfish= deep dwelling/ not so active
Shark Nervous System:
- What are the four cranial nerves we went over in class?
- Olfactory (first nerve)
- Optic (second nerve)
- Trigeminal (fourth nerve)
- Vagus ( fifth nerve)
Shark Nervous System:
- Olfactory nerve?
- sensory nerve …concerned with the sense of smell
Shark Nervous System:
- Optic nerve?
- also a sensory nerve ..concerned with sight
Shark Nervous System:
- Trigeminal nerve?
- arises from the anterior end of the medulla. It is a mixed motor and sensory nerve which has four branches that enervate the face, eyes, mouth and jaws. The superficial opthalmic nerve is one of the four branches. It has a general sensory function for the skin of the rostrum
Shark Nervous System:
- Vagus nerve?
- the longest of the cranial nerves. It is a mixed motor and sensory nerve that arises at the posterior end of the medulla it innervates the gills, throat, esophagus, stomach, intestine and body wall.
Shark Nervous System:
- Sharks do or do not reportedly feel pain?
- reportedly do not feel pain since they lack the proper receptors
Shark Nervous System:
- What are nociceptors?
- pain receptors
L> sharks do not have these (elasmobranchs) –>fish world in general is thought to lack these
**normally embedded in the dermis
Shark Nervous System:
- If sharks do have feel pain than?
- we have yet to understand the mechanism
Shark Nervous System:
-What is a hypothesis as to why they lack nociceptors?
- feeling pain is not essential for their survival
- maybe feeling pain is selective?
L> why is this since they have such advanced sensory reception in other ways?
