morphology of locomotion Flashcards
Functional Morphology of Locomotion
Locomotion and shape
Drag
Moving through water
Aspect ratio
Locomotion types
why fish need specific body shapes
- 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
Drag
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
Body shape for drag reduction
- 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
to move through water:
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
Myomeres def
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
Collagenous septa
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
Myomere contractions
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
The Aspect ratio of the Caudal fin
- 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
AR formula (aspect ratio)
AR= height ^2/surface area
Locomotory types
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
Within body and caudal fin (BCF)
fish are differentiated by how much body undulates vs. oscillates
Within median and paired fins (MPF),
fish are differentiated by which fins are doing most of the work and whether they are undulating or oscillating
Anguilliform
- 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
Subcarangiform
- 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)
Carangiform
- 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)
Functional hinges
- 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?
Thunniform
- 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
Ostraciiform
- 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)
Tetraodontiform
- Body shape variable but clear medial fins
- Oscillatory (MPF) synchronous or asynchronous
movement of anal and dorsal fins
Balistiform
- Similar to “tetra-odontiform” but with more undulation of fins rather than oscillation
Diodontiform
- Undulation of anal, dorsal, and pectoral fins
Rajiform,amiiform and gymnotiform
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)
Labriform
- 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
