MFWB_A - Annelids

coelom

compartmentalised into metameric segments (all contain organs and tissues)

chaeta/setae

bristles on each segment, some can protrude from parapodium and become leg like

classes of annelids

Polychaeta, oligochaete, hirundinae

Polychaeta

mainly marine, brightly coloured predators, large jaws

suspension Polychaeta

mucous, suspension feeding, parapodia, everted pharynx that can be retracted

oligochaetas

earthworms, freshwater and terrestrial, no parapodium, fixed number of body segments and no cephalisation

hirudinea

leeches, mainly aquatic, evolved anterior and posterior suckers - anterior acts as a mouth, feeds on prey, no segments

common features of all annelids

metamerism, compartmentalised segmented coelom, paired epidermal chaetae

Polychaeta feeding

non retractable jaws, complex heads with many numbers of appendages, L-shaped tubes/burrows, secretes own tube and siphons water

oligochaeta feeding

use pharynx to pump particles into digestive system, deposit feeders

hirudinea feeding

specialised anti-coagulant saliva (hirudin), specialised blood, find host by heat and chemical receptors

Polychaeta locomotion

diverse range, errant, sedentary, e,g., neresis - paired sets of dorsal longitudinal muscles contract on one side, compressing serum, other side expands, parapodia and chaeta push water behind

oligochaeta locomotion

two sets of muscles in different contractions, some have longitudinal, circular, creates overall forward motion, peristalsis (internal movement of fluids)

hirudinea locomotion

due to having no segments, one side of body cannot be moved independently from another, move anterior and bring posterior towards it

Polychaeta reproduction

enlarge eyes and parapodia to increase the release of gametes, controlled by pheromones, and both adults die afterward therefore cost effective when finding a mate but high when large number of gametes produced

oligochaetas reproduction

hermaphrodites, copulation is required, transfers eggs to cocoon

hirudinea reproduction

hermaphrodites, similar to oligochaetas, cocoons stuck to objects