morphology of locomotion

Question 1

Functional Morphology of Locomotion

Answer 1

Locomotion and shape
Drag
Moving through water
Aspect ratio
Locomotion types

Question 2

why fish need specific body shapes

Answer 2

• Water is 800X denser, 50X more viscous, and contains 95% less O2 than air, so much more energetically demanding medium in which to move
• Fish body shapes and appendages generally reflects the need to deal with high water density
• Water density adds 2 types of drag to bodies moving through it * Viscous (friction) and Inertial (pressure) drag

Question 3

Drag

Answer 3

Viscous (friction) drag:
Comes from friction between fish body and water, and influenced by smoothness and surface area
Influenced by body and fin size, shape, and fin placement (insertion) on the body
Inertial (pressure) drag:
Caused by pressure differences resulting from the displacement of water as fish moves through it
This drag increases with speed and so also impacted by body shape

Question 4

Body shape for drag reduction

Answer 4

• Streamlined body shape
• Rounded with maximum width at 0.25 body length
• 0.26 Most sharks
• 0.24 Sword fish
• 0.28 Tunas
• Teardrop or torpedo shaped body makes more laminar flow over body surface minimising wake or inertial (pressure) drag
• Wing-like fins extend laterally providing lift (can be negative lift)
• In fast swimming fish – fins fit into body grooves to minimizing drag

Question 5

to move through water:

Answer 5

Gram for gram – fish have more muscle mass than any other vertebrate
* Male Tunas can be nearly 70% muscle, which is one reason fish are so good to eat
* Fish muscles are layered not bundled, so many of the segments overlap
* Muscle segments (myomeres) are not flat but have a 3- dimensional structure that interlock along the length of the body

Question 6

Myomeres def

Answer 6

to move thorugh water; separated by collagenous septa which connect them to each other and to the skin and the bones (and backbone)

Swimming achieved by contracting myomeres in sequence on either side of the body from anterior to posterior
* Thicker myomeres more solid the fish and the faster it will be

Question 7

Collagenous septa

Answer 7

to move through water;
critically important for fish movement similar to tendons in other vertebrates
They connect
* Myomeres to myomeres and * Myomeres to skin and bones
* The median septum occur vertically on the long axis of the fish, separating the left and right muscles
* The Main horizontal septum separates the epaxial (top) muscles from the Hypaxial (bottom) muscles

Question 8

Myomere contractions

Answer 8

create undulation in the body which pushes on the water
* Newton’s 3rd law of thermodynamics makes it so
the water pushes back to thrust fish forward and up
* Thrusts the fish forward with some lateral lift (slippage) which can be corrected by either a rigid upper body or through fin re-direction

Question 9

The Aspect ratio of the Caudal fin

Answer 9

• Caudal fin shape varies tremendously among fish, and can often determine a fish’s role within the ecosystem
• Aspect ratio (AR) is the relationship between height and surface area
• High AR = reduces drag and flex in caudal region and with narrow caudal peduncle leads to – rapid sustained propulsion - Chaser
• Low AR = broad surface area powerful thrust (fast starts) but high frictional drag not sustained speed – ambush/flee

Question 10

AR formula (aspect ratio)

Answer 10

AR= height ^2/surface area

Question 11

Locomotory types

Answer 11

Undulation: Sinusoidal waves passing
Oscillation: Structures are moved back down body or fin(s) and forth to generate thrust

Two general body areas associated with swimming propulsion
Body and Caudal Fins (BCF)
Medial and Paired fins (MPF)
12 generalized types of locomotory types applied largely to fish orders and families – but also apply to unrelated taxa

Question 12

Within body and caudal fin (BCF)

Answer 12

fish are differentiated by how much body undulates vs. oscillates

Question 13

Within median and paired fins (MPF),

Answer 13

fish are differentiated by which fins are doing most of the work and whether they are undulating or oscillating

Question 14

Anguilliform

Answer 14

• Typical of elongated body shapes (eels, lampreys, some sharks)
• Most of the body contributes to propulsion by undulation (1⁄2 sine
  wave)
• Large undulations cause self-braking from high drag and slippage and so, highly inefficient
• Relatively slow and awkward but good for swimming around structures, for digging, and hiding
• Many fish begin as anguilliform swimmers but become carangiform post metamorphosis

Question 15

Subcarangiform

Answer 15

• Body shape still fusiform (torpedo shaped) and more rounded (e.g., salmon, cod, cyprinids)
• Movement still undulatory but engages less of the body
• Mainly posterior 2/3 – 1/2 of the trunk and tail, which decreases flexion
  (drag) and increases rigidity
• Low AR good for rapid starts from dead stops, excellent for ambush predators,.. but variable
• Also good at hovering and sitting in place (can then engage other forms of locomotion too)

Question 16

Carangiform

Answer 16

• Body shape becoming more laterally compressed and more teardropped (herring, characids, scombrids)
• Movement still undulatory but even less of body involved (≤ 1/3 and largely tail)
• Even less drag and higher rigidity with greater thrust and speed (but less manoeuverability)
• Higher AR meaning,…..
• Beginning aspects of a functional hinge (tendon linking tail to caudal peduncle)

Question 17

Functional hinges

Answer 17

• Common to carangiform and thunniform swimmers
• Maintain tail at ideal angle for more consistent power
  stroke
• Substantially reduces inertial (pressure) drag
• Often accompanied by stiffer bodies as collagenous septa and myomeres get thicker
• Combined with above reduces lateral lift (slippage), with even small undulations resulting in incredible speeds
• What do you think is compromised?

Question 18

Thunniform

Answer 18

• Body shape perfected for high speed which is achieved with little body undulation (mostly caudal peduncle and tail)
• Functional hinge and large tendons link myomere flexion to caudal peduncle
• Extreme body rigidity and narrow necking reduce viscous and inertial drag
• Very high AR nearing 4 - 8.5 (Marlins and sailfins can get up to 10)
• 20 m/s burst speed, 4 m/s sustained

Question 19

Ostraciiform

Answer 19

• Body shape in this group varies substantially but typically have very distinct tail (almost appear freakish)
• Propulsion mainly through tail movement back and forth (Oscillatory)
• Boxfishes are extreme case of “Ostraci-iform” locomotory style
• Most species using this locomotory type use body for other purposes and often have restricted or reduced body mobility (e.g., electric elephant fish)

Question 20

Tetraodontiform

Answer 20

• Body shape variable but clear medial fins
• Oscillatory (MPF) synchronous or asynchronous
  movement of anal and dorsal fins

Question 21

Balistiform

Answer 21

• Similar to “tetra-odontiform” but with more undulation of fins rather than oscillation

Question 22

Diodontiform

Answer 22

• Undulation of anal, dorsal, and pectoral fins

Question 23

Rajiform,amiiform and gymnotiform

Answer 23

Rajiiform
* Undulation of pectoral fins in skates and rays
Amiiform
* Main propulsive power from undulating dorsal fin (not great swimmers)
Gymnotiform
* Main propulsive power from undulating anal fin(s) (clumsy)

Question 24

Labriform

Answer 24

• Body shape typically more laterally compressed fish with often important fins
• Mostly pectoral fin based oscillatory movements - but also important contribution of body undulation
• Power stroke provides strong propulsion, recovery stroke provides lift (often look like they are hopingàswim hopping)
• Pectoral fins provide thrust and stability making these fish highly maneuverable
• Body and fin shapes are flexible and can switch to different locomotory forms when needed