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 contractCircular muscles relax

Longitudinal muscles relaxCircular 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 - CH2

CH2OH

O

NH

O = C - CH2

O

N - acetylglucosamine polymer

OH H

H

OH

H

H

O

CH2OH

H

H

OH H

n

Insect Integument (Exoskeleton)

CO

NH CO

NH CO

NH CO

NH CO

NH CO

NH

CO

NH CO

NH

CO

NH CO

NH CO

NH CO

NH

hydrogen bonds

NH

O = C - CH2

CH2OH

O

NH

O = C - CH2

OH H

H

OH

H

H

O

CH2OH

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

CH2

Protein Protein

OH

OH

CH2

CH2

O

O

CH2

CH2

OH

OH

CH2

CH2

Protein Protein

N-acetyl dopamine N-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/mm2

Insect Leg - Articulation

monocondylic

Decreasing mobility

Increasing strength

dicondylic

leg leg

Insect Leg Muscles

Extensor

Flexor

Dicondylic joint

Scorpion leg musculature

Echinodermata – tube feet – back to hydrostatics

Motion of tube feet - video

Echinoderm structure

Echinoderm structure

Tube Foot Structure

Ampullar muscle

Postural muscle

Longitudinal retractor

Radial canal

muscle

Valve Resultant action

1 Contracts Relax Close Extend tube foot

2 Relax Relax Contract Close Shorten tube foot

3 Contract Contract Relax Close Move foot to the side

4 Contract Contract Relax Close Move foot to the side

5 Contract Relax Close

6 Contract Open Extra extension of tube foot

1.

2.

3.4.

5.

6.

valve