Locomotion and Movement

Animal Physio

What makes locomotion so challenging

• Overcoming inertia 

• Overcoming frictional drag from the environment 

• Defying gravity

Porifera Movement Strategy

• Adult sponges

  • Sessile but can creep

  • No muscles or nervous tissue 

  • Some may have “whole body contractions” as individual cells compress in a synchronized way!

• Larvae Sponges

  • Ciliary Swimmers! 

  • Very Cute.

Cnidarian Movement Strategy

• Structure: Hydrostatic 

• Movement: Contractual fibers/epitheliomuscular & nerve net

• The key feature is the presence of myofibrils (muscle filaments) within a portion of the cell. These filaments allow the cell to contract, enabling movement and other muscle-like actions!

• More Specifically…

  • Jellies: Jet propulsion 

  • Coral larvae: Ciliary swimmers

  • Anemones: Pedal creeping, free swimming

Epitheliomuscular

• a specialized cell found in simple animals like cnidarians (such as Hydra and jellyfish). It combines the features of an outer epithelial cell (covering surfaces) with the contractile traits of a muscle cell (allowing movement

• Derived from ecto/endoderm, whereas muscles for other phyla are derived from the mesoderm

• Integrated into their epithelial tissues, rather than specialized muscle tissue layers 

• If sarcomeres are present, they are shorter than those in other animals

Playthelmenthes Movement Strategy

• Ciliary Gliding 

  • I have cilia on my ventral surface, which beat in a coordinated manner, pushing against a secreted mucus layer to facilitate smooth gliding!

• Muscular

  • Circular Muscles: These muscles encircle the body. Contraction squeezes the body, causing the flatworm to become thinner.

  • Longitudinal Muscles: These muscles run along the length of the flatworm's body. Contraction shortens the body.

  • The coordinated action of circular and longitudinal muscles allows flatworms to move in a wave-like or undulating motion!

Rotifera Movement Strategy

• Ciliary

  • Coronal cilia can be used to assist in movement 

• Muscular

  • Circular Muscles: These muscles encircle the body. Contraction squeezes the body, causing the rotifer to become thinner.

  • Longitudinal Muscles: These muscles run along the length of the body. Contraction retracts the foot or head. 

Mollusca Movement Strategy

• Muscular Foot

• Muscular System

  • Circular & Longitudinal Muscles work to generate complicated movement patterns, oftentimes, where pressure on a contained fluid helps extend or retract body parts.

  • Mostly Circular Muscles aid in directional movement using environmental fluid

• Hydrostatic

  • Brings water into the mantle and shoots it out the siphon 

Annelida Movement Strategy

• Muscular

  • Segmentation allows circular and longitudinal muscles to change the shape of individual segments!

• Hydrostatic 

  • Segments have fluid filled compartments

• Setae

  • Tiny bristle-like structures protrude from each segment. (not the same as cilia) 

  • Provide grip on the substrate during movement

  • Controlled by small muscles—can be retracted or extended.

Nematoda Movement Strategy

• Exoskeleton

  • Cuticle - made mostly out of collagen, the cuticle provides structure as well as surface area for muscle attachments.

  • Hydrostatic

    • Pushes against the exoskeleton 

  • Muscular

    • Longitudinal Muscles Only! 

    • Movement is whip-like and chaotic!

Arthropoda Movement Strategy

• Exoskeleton

  • Made mostly out of chitin, provides structure and attachment points for muscles

• Muscular

  • Muscles attach to inner surfaces of exoskeleton in antagonistic pairs

  • Flexors & extensors control limb bending and straightening.

  • No circular or longitudinal body wall muscles!

Echinodermata Movement Strategy

• Hydrostatic

  • Water vascular system

• Endoskeleton

  • Porous calcite, may articulate (IE mouth parts)

• Muscular

  • Structurally simple, helps moves spines or legs 

• Mutable connective tissue

  • Tissue that has weird mechanical properties, making their collagen stiff or soft in seconds!

  • This "switching" ability is crucial for various echinoderm behaviors, including posture maintenance and defensive mechanisms, like autotomy!

  • This ability is not found in any other animal phyla!...and has only been studied in Sea Cucs. 

Vertebrata General Movement Strategy

• Skeletal muscles paired with an endoskeleton; provides internal support and jointed leverage.

• Axial (along the spinal column) and appendicular (limbs) structures

Fish Movement Strategy

• Axial Movement - Myomeres on the left and right sides contract in alternating waves creating side-to-side movement

• Fins aid in steering, stabilization, and propulsion.

Amphibian Movement Strategy

• Aquatic: Axial muscles still prominent for swimming

• Terrestrial: Axial & Appendicular → Pectoral & pelvic girdle strengthen. Vertebral column stiffens to support weight out of water

Reptile Movement Strategy

• Lizards

  • Undulatory walking, but with more appendicular muscle development and more control over tail (balance, climbing, speed) 

• Snakes

  • Lateral Undulation (Serpentine): Wavelike, muscles contract sequentially on alternating sides.

  • Concertina Locomotion: Like an accordion! - Snake anchors part of the body, extends forward, then pulls rest of body forward.

  • Rectilinear Locomotion: Slow, straight-line crawling. Muscles pull belly scales forward one section at a time

Bird Movement Strategy

• Locomotion types - Powered flight, walking, gliding

• Appendicular musculature adaptations:

  • Pectoralis major: wing downstroke 

  • Supracoracoideus: wing upstroke

• Skeletal adaptations:

  • Fused bones - rigid skeleton for flight efficiency.

  • Honeycombed bones to reduce weight.

Mammal Movement Strategy

• Locomotion: Walking, running, jumping, climbing, swimming 

• Muscular System: Large, regionally specialized limb muscles.

• E.g., gluteals, hamstrings, gastrocnemius for running/jumping

• Skeletal System: Upright posture increases stride efficiency

Ultra Fast Movements

• Muscles alone can’t always deliver the extreme speed or force required for some animal movements.

• Instead, animals use power amplification — storing energy and releasing it suddenly like a catapult or spring!

• What is ATP is not enough?

  • Muscle slowly contracts → storing energy in elastic structures

  • Latch prevents release

  • Latch is released → stored energy unleashes movement faster than muscles alone could manage

Cilia

tiny, hair-like structures on the outside of animals that help to facilitate movement and other things

power amplification

a biological process where organisms use elastic structures like springs, latches, and specialized linkages to store and release muscular energy. This mechanism allows animals to produce sudden, ultrafast movements that far exceed the normal speed and power limits of direct muscle contraction.