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Phylum Annelida.

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Presentation on theme: "Phylum Annelida."— Presentation transcript:

1 Phylum Annelida

2 Phylum Annelida “little ring” Segmented worms 15,000 species
Marine worms freshwater worms terrestrial worms Leeches worldwide distribution Soft body Repeating segments allow independent movement

3 Size of Annelids <1mm  many meters
Megascolides australis up to 7.5 m!

4 Architectural patterns of animals
Architectural patterns of animals. These basic body plans have been variously modivied during evolutoinary descent to fit aimals to a great variety of habitats. Ectoderm is shown in gray, mesoderm in red, and endoderm in yellow Fig. 9.9

5 Fig. 9.9

6 Trochophore larva

7 Characteristics of Phylum Annelida
triploblastic schizocoelomate

8 In enterocoelous formations, the ceolom comes from pouches of the primitive gut (archenteron)
Fig. 9-13, p188

9 Characteristics of Phylum Annelida
Coelom partitioned by walls (septa) Serial (repeating) segmentation= metamerism Each segment= metamere/ somite

10 Development of Metameric, Coelomic Spaces

11 Characteristics of Phylum Annelida
External evidence of septa= circular grooves called annuli (rings) Septa annuli

12 Advantages of metamerism
greater flexibility of movement, compare to nematode Components organ systems repeated w/i segments (repeated excretory, nervous, circulatory structures) Built-in redundancy- increases survival

13 Note: Not all organ systems are metameric ie, digestive system extends the length of the organism and is differentiated along its length

14 Characteristics of Phylum Annelida
Greater flexibility demands greater fine motor skills Highly developed, centralized nervous system brain Ventral nerve cord Ganglion in each metamere

15 Movement in Phylum Annelida
Fluid-filled coelom (except Subclass Hirudinea) = hydrostatic skeleton Longitudinal and circular muscles

16 Characteristics of Phylum Annelida
Closed circulatory system (except some leeches) Blood vessels and aortic arches (“hearts”) Branch to every metamere

17 Excretory System of Annelids
Consists of paired metanephridia (in most) Excretory tubes with ciliated funnels that remove waste from the coelomic fluid open to the outside via excretory pores.

18 Phylum Annelida: Classes
Class Polychaeta Class Clitellata Sublass Oligochaeta Subclass Hirudinea Fan Worms clip

19 Class Polychaeta poly = many; chaeta = bristles Mostly marine
Example: Neries video Mostly dioecious

20 Class Polychaeta (cont’d)
Parapodia fleshy segmented appendages for locomotion & breathing have numerous setae at ends of parapodia Fireworm (Hermodice carunculata)

21 Class Polychaeta (cont’d)
Gas exchange across parapodia

22 Class Polychaeta (cont’d)
parapodia have numerous setae at ends Tiny chitinous bristles Chitin= tough, flexible polysaccharide; not soluble in water Provide anchorage Swimming Fireworm (Hermodice carunculata)

23 Class Polychaeta (cont’d)
well differentiated head (prostomium) with specialized organs (eyes, jaws)

24 Class Polychaeta (cont’d)
Many are euryhaline (able to tolerate a wide range of salinity conditions). Live under rocks, coral crevices, abandoned shells. Serve as the basis for many marine food chains.

25 Class Clitellata Earthworms and leeches Few/no setae Possess clitellum

26 Class Clitellata (cont’d)
Clitellum secretes mucus for cocoon, copulation

27 Class Clitellata (cont’d)
monoecious, cross-fertilization

28 Subclass Oligochaeta oligo = few; chaeta = bristles
Terrestrial, freshwater, some marine Example: earthworms, night crawlers

29 Subclass Oligochaeta (cont’d)
Prostomium lacks sensory structures Parapodia are absent Prostomium  2. Mouth   3. Buccal cavity  4. Pharynx  5. Esophagus   6. Nephridia  7. Seminal vesicles  8. Dorsal blood vessel  9. Ventral blood vessel10. Aortic arches11. Suprapharyngeal ganglion12. Circumphar. connective13. Ventral nerve cord bioweb.uwlax.edu/.../ earthworm_model_1a.htm

30 Subclass Oligochaeta (cont’d)
Feeds on organic or vegetable matter in soil May be as many as 50,000/acre Earthworms very beneficial in aerating the soil. capable of recycling up to 18 tons of soil/acre annually food

31 Do these questions now…
The coelomic cavity of annelids is usually divided by walls called ________ What is metamerism? What are the advantages of metamerism? Is any part of the annelid not metameric? What part? To what class do earthworms and leeches belong?

32 Subclass Oligochaeta (cont’d)
Gas exchange across moist skin  to circulatory system

33 Subclass Hirudinea Leeches Mostly freshwater
possess clitellum – apparent only during reproduction have annelid characteristics but generally lack setae Monoecious, cross-fert. Generally dorsoventrally flattened

34 Subclass Hirudinea (cont’d)
Predatory Attach to host via 2 suckers

35 Subclass Hirudinea (cont’d)
Locomotion More complex muscle system- includes oblique + dorsoventral muscles “inchworm” movement via suckers

36 Subclass Hirudinea (cont’d)
Have a fixed number of metameres Internal septa are lacking coelom functions as a single, large chamber with connective tissue, muscle, and spaces

37 Subclass Hirudinea (cont’d)
Gas exchange across skin (in most)

38 squeamish?

39 Medicinal leech Attach via suckers, pierce skin with sharp proboscis.
Leeches cure Attach via suckers, pierce skin with sharp proboscis. Proboscis resembles 3 circular saw blades. Salivary glands secrete local anesthetic and an anti-coagulant. remove hematomas resulting from surgery 15 ml blood/meal hematomas (areas of blood leakage)


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