Annelida Flashcards
Advantages of a Coelum
Fluid-filled cavity lying between body wall and the
gut.
Serves a variety of functions:
Hydrostatic skeleton – facilitating support & movement
(fluid has little metabolic demand)
Site for temporary accumulation and movement of
nutrients, waste, gasses (2
o circulatory system)
Space for maturation of eggs and sperm
Space allowing enlargement of internal organs
( e.g. gonads)
General External Annelid Features
Long cylindrical (vermiform) segmented body.
Metameric segmentation- obvious in especially the
primitive groups
Anterior end- prostomium (sensory)
Posterior end- pygidium
Briefly describe Annelid movement
Coelom (as hydrostatic skeleton) + muscles
of the body wall + external appendages
- Peristalsis: Alternate contraction of circular
and longitudinal muscles + setae - Wriggling/Parapodial stepping: Setae or
parapodia providing contact with the
substrate
Circular muscles extend worm
Longitudinal muscles shorten worm.
briefly describe foregut (Annelid Digestive System)
- food gathering & processing.
- mouth, proboscis (may have jaws or teeth-like
structures) - Pharynx- pumping food down into oesophagus.
- Oesophagus divided into Crop (thin walled) &
Gizzard (thick walled- muscular).
Briefly Describe Midgut (Annelid Digestive System)
MIDGUT
- long (stomach & intestine)
- extracellular digestion.
HINDGUT
- found with anus in pygidium (exception:
leeches).
Describe Annelid Circulatory/ Respiratory System
CIRCULATORY/RESPIRATORY SYSTEM
Internal transport of nutrients, wastes & respiratory
gases.
Main blood vessel: large dorsal tube the animal’s
length. Opposed by a ventral vessel.
- Blood flow is anterior in dorsal vessel & posterior
in ventral. - Anterior most lateral connectives can function as
“hearts” - Pseudoheart. - Closed blood vascular system
Briefly describe Annelid reproduction
Variable.
Hermaphrodite/Dioecious
Internal or external
fertilization.
Trocophore larva (1st larval
stage-characteristic of
annelids).
