by: Juan Jaquez
17,000 living annelid species
Polychaetes there about 12,000 species.
They have multiple hairs segment.
Have parapodia that function as limbs, and nuchal organs on the neck area
Most are marine animals
a few species live in fresh water
least amount live on land
Clitellates has about 5,000 species
These have few or no hairs per segment
no nuchal organs or parapodia.
they have a unique reproductive organ a ring-shaped clitellum around their bodies
produces a cocoon that stores and nourishes fertilized eggs until they hatch.
The clitellates are sub-divided into:
Oligochaete which have few hairs
Is mostly earthworms.
have a sticky pad in the roof of the mouth.
Most are burrowers that feed on wholly or partly decomposed organic materials.
Hirudinea that are leech-shaped
best known members are leeches.
are mostly marine species that are mostly blood-sucking parasites
most freshwater species are predators
They have suckers at both ends of their bodies, and use these to move rather like inchworms.
Archiannelida annelids that live in the spaces between grains of sediment
were treated as a separate class because of their simple body structure
now are classified as polychaetes
Some other groups of animals have been classified in different groups but now are known as annelids:
Pogonophora / Siboglinidae
Echiura
myzostomida
Differences that distinguish annelids from invertebrate phyla
Their bodies are long and segments by rings called annuli Most have same organs, although sharing a common gut, circulatory system and nervous system
Their bodies are covered by an outer covering made of flexible callogen
Most annelids have closed circulatory systems
Segmentation
Most of an annelid's body consists of segments that are practically identical, having the same sets of internal organs and
external hairs and, in some species, appendages.
Most annelids have a pair of celoms or body cavities in each segment
Respiration
In some annelids, including earthworms, all respiration is done through the skin
Feeding and excretion
Most are Fillter feeders wash food particles towards their mouths.
The gut is almost a straight tube
Asexual Reproduction:
reproduce asexually, by dividing into two or more pieces or by pairing off a new individual while the parent remains a complete organism.
Sexual reproduction
people say that annelids were originally animals with two separate sexes, which released ova and sperm into the water Then fertilized eggs developed
Ecology:
Some Species fertilize soil
most species are harmful parasites
