Phylum: Annelida - segmented worms

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1 Phylum: Annelida - segmented worms
Class: Oligochaeta Class: Polychaeta Class: Hirudinea

2 Oligochaeta

3 Class: Polychaeta Bristle worm
is poisonous and attacks sea anemones

4 Class: Hirudinea

5 Christmas tree worm

6 Class: Polycheata

7 P O L Y C H A E T C L A S S

8 Yikes!!

9 Characteristics of Phylum :Annelida—Little rings
True coelom Each compartment is surrounded by peritoneum which forms dorsal and ventral mesenteries that covers all the organs Hydrostatic skeleton Closed circulatory system

10 True coelom

11 *Centralized Nervous System*
Brain Double ventral nerve cord Pair of ganglia in each segment Lateral nerves

12 *Centralized Nervous System*

13 Sensory organs Taste buds Statocysts - balance sensory receptor
Photoreceptor eyes with lenses in some

14 Circulatory System Blood flows entirely in closed vessels
Some spp. have hearts Blood contains hemoglobin, which increases oxygen carrying ability Phylum Annelida

15 Excretory system Pair of nephridia in each segment

16 Respiration By gas exchange through Skin Gills
Parapodia - fleshy paired appendages

17 Body plan Bilateral Metameric-repeating segments
(metamerism allows for budding) Setae-small hairs or sometimes parapodia, i.e. small appendages

18 Body plan Setae (“bristles”) of chitin “anchors” for earthworm
“paddles” for polychaete Enlarged as jaws in leeches, some polychaetes

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20 Reproduction Sexes are usually separate with gonads occurring in each segment Some species have gonad specific segments Breeding is usually seasonal (spring or fall) As gametes mature they fill the coelom and are released by the nephridia Fertilization can be internal or external Trochophore larvae develop, which are remarkably similar to the Molluscs

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22 Skin Contains glands to secrete mucous and setae

23 Nutrition Eat any dead organic material
Consume up to one half their body weight every day

24 Nutrition Annelids range from carnivores, herbivores, scavengers, deposit feeders, and filter feeders With very few defenses, many remain in a burrow or secreted tube Carnivores can capture prey with strong jaws and quickly drag it back to its burrow Can use a muscular pharynx = eversible proboscis

25 Digestion mouth esophagus crop intestines gizzard
Mechanical –grinding in the gizzard Chemical in the intestines Extracellular and intracellular digestion

26 Environmental role Can be found in fresh water, salt water, soil
Helps aerate/renutrify gardens Medicinal purposes

27 Classes How do we classify these segmented worms into different classes?

28 Class: Polychaeta (many setae or hairs)
20+ setae per segment Well differentiated head Specialized sense organs Parapodia No clitellum Mostly marine predators, e.g. “Barry” the seaworm

29 Class: Polychaeta (many setae or hairs)

30 Class: Oligochaeta (Few long hairs)
Clitellum Few long, short or straight setae; 2-4 clusters per segment Land or marine, some parasites

31 Class: Oligochaeta (Few long hairs)

32 Class: Hirudinea Flattened dorsalventrally
Mostly freshwater, some marine Fluid feeder (blood) Clitellum Setae have developed suckers Specialized proboscis

33 Class: Hirudinea Class Hirudinea pair of bladelike “jaws”
posterior “suction cup” Predators External parasites, “bloodsuckers” Secrete anticoagulants Medicinal use

34 Blood Sucker The salivary glands excrete hirudin which prevents the blood from coagulating May also secrete an anaesthetic and substance to dilate small blood vessels Blood is broken down by symbiotic bacteria that is then used by the leeches Leeches were commonly used in the 19th century for bloodletting Recent medical uses are to relieve pressure after vascular tissue is damaged Snake bites or the reattachment of a finger or ear Phylum Annelida