LOCOMOTION II: SEGMENTATION AND BEYOND

The next step - worms

Annelida - a significant improvement in body architecture SEGMENTATION Dividing the body into smaller repeated units

Annelida - a significant improvement in body architecture SEGMENTATION - Why?? 1. Allows more precise movement - reorient and twist part of the body

Annelida - a significant improvement in body architecture SEGMENTATION - Why?? 2. Allows muscle contraction without bulging Standard coelomate body plan. mesoderm = muscle If muscle contracts without segments contracting area

Annelida - a significant improvement in body architecture SEGMENTATION - Why?? 2. Allows muscle contraction without bulging If muscle contracts without segments If muscle contracts with segments Area of contraction is restricted

Annelida - a significant improvement in body architecture SEGMENTATION - Why?? 2. Allows muscle contraction without bulging

Longitudinal muscles contract Circular muscles relax Longitudinal muscles relax Circular muscles contract

Earthworm movement Centre of contraction Affected segments

Polychaete worms Add a new feature – appendages

Polychaete worms Parapodia

Nereis Two kinds of locomotion 1) Slow crawl Recovery stroke Propulsive stroke Contraction of levator muscles Contraction of transverse parapodial muscles

Nereis Two kinds of locomotion 1) Slow crawl 2) Fast crawl

ARTHROPODS: HARD AND CRUNCHY

Insect Integument (Exoskeleton) NH O = C - CH 2 CH 2 OH O NH O = C - CH 2 O N - acetylglucosamine polymer O HH H OH H H O CH 2 OH H H OH H n

Insect Integument (Exoskeleton) CO NHCO NHCO NHCO NHCO NHCO NH CO NHCO NH CO NHCO NHCO NHCO NH hydrogen bonds NH O = C - CH 2 CH 2 OH O NH O = C - CH 2 O HH H OH H H O CH 2 OH H H OH H

Insect Integument (Exoskeleton) N - acetylglucosamine polymer microfibril sheets of microfibrils orientation of microfibrils changes

Insect Integument (Exoskeleton) Protein Matrix

Insect Integument (Exoskeleton) Cross linking of protein matrix

Insect Integument (Exoskeleton) OH Cross linking of protein matrix OH C CH 2 Protein OH CH 2 O O OH CH 2 Protein N-acetyl dopamineN-acetyl dopamine quinone

What other common material has cross-linked fibres in a matrix? Plywood Oriented Strand Board (OSB) Plywood

Insect Integument (Exoskeleton) Tensile strength of sclerotized chitin (sclerotin) kg/mm 2

Insect Leg - Articulation monocondylic Decreasing mobility Increasing strength dicondylic leg

Insect Leg Muscles Extensor Flexor Dicondylic joint

Scorpion leg musculature

Echinodermata – tube feet – back to hydrostatics Motion of tube feet - video

Echinoderm structure

Tube Foot Structure

Ampullar muscle Postural muscle Longitudina l retractor Radial canal muscle ValveResultant action 1ContractsRelaxCloseExtend tube foot 2Relax ContractCloseShorten tube foot 3Contract RelaxCloseMove foot to the side 4Contract RelaxCloseMove foot to the side 5ContractRelaxClose 6ContractOpenExtra extension of tube foot

6. valve