02 June 2015 Annelida.ppt 1

Phylum Annelida

“segmented worms”

02 June 2015 Annelida.ppt 2

Phylum Annelida• Phylum Annelida

• Latin “ringed” analogy to tree annual rings

~ 9000 species

• Body plan •Tube-in-tube, Protostomous

•Bilateral symmetry

•Coelomate, “split” coelom

• Marine, aquatic, terrestrial

02 June 2015 Annelida.ppt 3

Phylum Annelida• Tissues and organs differentiated • Segmentation highly developed• Mesodermal “blocks,” each with own coelom

• Septa between segments

02 June 2015 Annelida.ppt 4

Phylum Annelida• Hydrostatic skeleton

• Fluid pressure in coelom provides support & locomotion

• Circular muscles

• Longitudinal muscles

• Peristaltic locomotion

02 June 2015 Annelida.ppt 5

Function of a hydrostatic skeleton

02 June 2015 Annelida.ppt 6

Phylum Annelida• Setae (“bristles”) of chitin• “anchors” for earthworm

• “paddles” for polychaete

• Enlarged as jaws in leeches, some polychaetes

02 June 2015 Annelida.ppt 7

Animal Life

• Ways the needs of cells are met• Food

• O2 and CO2 exchange • Across epidermis, some have “gills”

• Waste removal• Metanephridia in each segment

02 June 2015 Annelida.ppt 8

Phylum Annelida

• Special concerns of a multicellular animal• Circulation closed

• Coordination: Nervous system with paired ventral cords

• Structural support: Hydrostatic

• Movement: Hydrostatic

• Maintenance of water balance: Segmental metanephridia.

• Reproduction• Usually sexual, sexes separate or hermaphroditic

02 June 2015 Annelida.ppt 9

Phylum Annelida

• Closed circulatory system• Multiple “hearts”

• Hemoglobin • not in blood cells

• reddish-pink color

02 June 2015 Annelida.ppt 10

Phylum Annelida

• Central nervous system• Dorsal brain

• Pair of nerves on sides of esophagus

• Paired ventral nerve cords with paired ganglia in each segment

• Transverse nerves connect ganglia in each segment

02 June 2015 Annelida.ppt 11

Phylum Annelida

• Earthworms’ paired nerve cords are fused into single ventral cord

• Arthropod better illustrates primitive nervous system of both phyla.

02 June 2015 Annelida.ppt 12

Phylum Annelida

• Metanephridia for excretion of metabolic waste products

02 June 2015 Annelida.ppt 13

Phylum Annelida “Class Polychaeta”• Mostly marine, very

diverse (polyphyletic )

• “many setae,” clusters with 20+ setae

• parapodia

02 June 2015 Annelida.ppt 14

Phylum Annelida Superclass Errantia

• Mostly marine, diverse active swimmers, predators

• “many setae,” clusters with 20+ setae

• parapodia

02 June 2015 Annelida.ppt 15

Phylum Annelida

Superclass Sedentaria• Mostly marine,

sedentary tube builders, filter feeders

• Class (?) marine tube worms

• Class (?) Clitellata• With clitellum

02 June 2015 Annelida.ppt 16

Phylum Annelida

Class (?) Clitellata • Clitellum

• Aquatic & terrestrial

Subclass (?) Oligochaeta• Few setae in 2-4 clusters per

segment

02 June 2015 Annelida.ppt 17

Phylum Annelida

Subclass (?) Hirudinea• pair of bladelike “jaws”

• posterior “suction cup”

• Predators

• External parasites, “bloodsuckers”

• Secrete anticoagulants

• Medicinal use

02 June 2015 Annelida.ppt 18

Phylum Annelida

Class Hirudinea Hirudin from leech,

Hirudo medicinalis, inhibits blood clotting

H. medicinalis, registered as “medical device.”