lophophorates and echinoderms

Lophorophorates features

sessile suspension feeders enclosed in a secreted exoskeleton

some are colonial

bryozoa (moss animals)

• colonial individual zooids secrete a house and multiply asexually

• members of the colony are connected by funicular cords where nutrients is exchanged

• zooids are less than 1mm up to 2million in single colony

• marine ususally

what are the advantages of being in a colony

• endless series of genetically identical modules the slow down in growth does not occur as usual

• growth actually accellerates w increasing colony size

• feeding non dividing zooids at the centre contribute nutrients to the active ones at the periphery

characters of echinodermata

• spiny skin

• secondarily radially symetrical

• calcereous endoskeleton made by mesodermal tissue:

• larvae are bilaterally symetrical

• oral and aboral surfaces

• embryology deuterostomous

• gut usually complete

• sea stars evert part of the stomach over prey, secrete enzymes and absorb partially digested soup

• no excretory organs and no specally organs for gas exchange

• circulatory system (when present

• nervous system decentralised

• dioecious

• fluid filled canals for the tube feet for locomotion and feeding

mutable connective tissue

• rapid and reversible change in stiffness often within few seconds under nervous control

• change in viscocity of collagen fibres

• ionic movements alter weak interaction between the macromolecules

• means muscle tone can be alteresd without energy involved w muscular contraction

crinoidea (feather stars and sea lillies

• suspension feeders

• mouth is surrounded by feeding arms and is linked to a u shaped gut

• anus located on the oral disc near the mouth

• 5 arms are subdivided into 10 or mire

• feather stars are impressive swimmers

sea stars (asteroidea0

• scavengers

• invasionary species

• starfishes

• problem for conservation

holothuroidea: sea cucumbers

• suspesion or deposit feeders

• pharynx lies behind the mouth anf is usrrounded by a ring of ten calcereous plates

• sea cucumbers extract oxygen from water in a pair oof respiratory trees that branch in the cloaca just inside the anus