Phylum Annelida the segmented worms

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1 Phylum Annelida the segmented worms
1st phyla we will talk about and what we will cover in the lab today is…

2 Annelids - segments Animals that have many segments
Include earthworms, leeches and marine polychaetes. Most annelids have chitin-reinforced bristles --setae on each side (to provide movement). Oligochaetes – few e.g. earthworms Polychaetes – many bristles per segment Provide evolution of regional specializations where some segments undergo modification to take on new functions. e.g. leeches have suckers at both ends and polychaetes have elaborate head and segments ` closely resembling feet’.

3 Annelida Characteristics
Triploblastic Organ level of organization Bilateral Symmetry Cephalization Eucoelomate

4 Different Body Cavities
Acoelomate No body cavity ectoderm mesoderm Gut endoderm

5 Different Body Cavities
Pseudocoelomate Have a “false” body cavity that is surrounded on ONE side only by mesoderm ectoderm pseudocoelom mesoderm Gut endoderm

6 Different Body Cavities
Eucoelomate Have a “true” body cavity that is completely surrounded by mesoderm ectoderm coelom mesoderm Gut endoderm

7 Annelid Characteristics
the coelom is a closed, fluid filled cavity that surrounds the gut the fluid within acts as a circulatory system mesodermal membranes (mesenteries) suspend organs in the coelom ectoderm

8 Annelida Characteristics
Protostome Development is characterized by: blastopore becomes the mouth

9 Mouth Formation Blastopore becomes the mouth and the anus forms secondarily Future anus blastopore archenteron (primitive gut) mouth

10 Annelida Characteristics
Metamerism The body is made up of serially repeating, coordinated segments called metameres that are separated from one another by septa. Each metamere contains sets of repeating organs e.g. gut, blood vessels, nerve cord, excretory organs

11 Metamerism septa

12 FEEDING Digestive tract is a long tube extending from mouth to anus
Muscular pharynx is very diversified in annelids (can include crop and gizzard similar to birds) Some have sharp teeth. Leeches use pharynx to suck blood and tissues from host Some aquatic annelids are filter feeders.

13 Annelid RESPIRATION mainly by diffusion
Aquatic annelids breath through gills (feather duster worms) Some use diffusion through skin (skin must stay moist) Class Polychaeta often has specialized structures for gas exchange (e.g. parapodia, gills)

14 INTERNAL TRANSPORT Closed circulatory system with 2 blood vessels running the length of their bodies (dorsal and ventral) In each segment, smaller ring vessels supply blood from the main vessels to organs. In earthworms, some of the ring vessels work like hearts (pumping blood to the rest of the body)

15 NERVOUS SYSTEM Some have well developed nervous system
Ventral nerve cord runs the length of the body in earthworms. Free-living marine annelids have best developed sense organs (balance organs, chemical receptors and eyes). Earthworms have no specialized sensory cells.

16 MOVEMENT Two major muscle groups (longitudinal and circular)
(Nematodes only have longitudinal muscles)

17 REPRODUCTION Most reproduce sexually
Earthworms have structure called a clitellum which secretes a mucus ring into which eggs and sperm are released during copulation.

18 Annelida Characteristics
EXCRETION excretion is accomplished by organs called nephridia (singular nephridium) Skeletal System fluid in coelom acts as a hydrostatic skeleton

19 Phylum Annelida Class Polychaeta Class Oligochaeta Class Hirudinea

20 Class Polychaeta 1st phyla we will talk about and what we will cover in the lab today is… 20

21 Class Polychaeta Poly = Many Chaeta = Bristles
Aquatic worms with bristles or projections on either side of the segments

22 Class Oligochaeta 1st phyla we will talk about and what we will cover in the lab today is… 22

23 Class Oligochaeta Oligo = Few Chaeta = Bristles
Includes earthworms, burrowing worms

24 Class Hirudinea 1st phyla we will talk about and what we will cover in the lab today is… 24

25 Class Hirudinea Leeches: _external parasites_
Have powerful suckers at each body end Produce an anti-coagulant (prevents blood from clotting) so that they can continue to drink the host’s blood. Leeches can swallow up to 10X their weight in blood and can survive off one meal for a whole year! Often used for medical purposes.

26 Class Polychaeta 1st phyla we will talk about and what we will cover in the lab today is…

27 Class Polychaeta all marine
this class contains 2/3 of all known Annelids have a well developed head with specialized sense organs 1st phyla we will talk about and what we will cover in the lab today is…

28 Class Polychaeta have many setae (chitonous bristles secreted by the epidermis) (Poly = many, chaeta= setae) these setae are arranged in bundles on paddle-like appendages called parapodia 1st phyla we will talk about and what we will cover in the lab today is… setae

29 Class Polychaeta Parapodium setae 1st phyla we will talk about and what we will cover in the lab today is… The parapodia function in gas exchange, locomotion, and feeding.

30 Class Polychaeta Tagmatization (tagmosis)
the fusion and specialization of formerly metameric segments 1st phyla we will talk about and what we will cover in the lab today is…

31 Class Polychaeta Many are filter-feeders with specialized structures
1st phyla we will talk about and what we will cover in the lab today is…

32 Class Polychaeta Many are predatory with specialized structures
1st phyla we will talk about and what we will cover in the lab today is…

33 Class Polychaeta Many construct their own homes out of CaCO3 or sand debris and mucous 1st phyla we will talk about and what we will cover in the lab today is…

34 Class Polychaeta Reproduction usually dioecious
no permanent sex organs; gametes are shed into coelom fertilization is usually external indirect development  trocophore larvae 1st phyla we will talk about and what we will cover in the lab today is…

35 Class Polychaeta Epitoky
In some species, the rear portion of the worm (“epitoke”: carries the eggs or sperm), breaks off from the body and swims to the surface to reproduce. The remaining benthic worm (“atoke”) continues to feed and grow and will eventually produce new epitokes. In other species, there are pelagic individuals that resemble epitokes but the entire individual swims to the surface where the body wall ruptures, filing the water with eggs and sperm. To synchronize these spawnings, this swarming behavior is usually triggered by the full moon. 1st phyla we will talk about and what we will cover in the lab today is…

36 Ecology a fireworm Polychaetes often have effective
defense strategies: some have tubes to hide in some have vicious jaws some have modified “stinging” setae 1st phyla we will talk about and what we will cover in the lab today is… a fireworm

37 Ecology Some Polychaetes have a mutualistic relationship with their host for example, many scaleworms are found near, or in the mouth, of brittlestars, starfish, and sea urchins. The scaleworm eats its host’s leftovers and with its vicious jaws, it will attack any predator trying to eat it’s host. 1st phyla we will talk about and what we will cover in the lab today is…

38 Class Oligochaeta 1st phyla we will talk about and what we will cover in the lab today is…

39 Class Oligochaeta terrestrial, freshwater and marine
have few setae (Oligo = few, chaeta = setae) usually feed on detritus (decaying organic matter) have specialized digestive system to obtain the maximum amount of nutrients out of the detritus (e.g. typhlosole, gizzard, crop…)

40 Class Oligochaeta typhlosole-
infolding of the dorsal side of the intestine increases surface area for absorption of nutrients typhlosole gut

41 Class Oligochaeta Locomotion Circular muscle contraction
Longitudinal muscle contraction

42 Class Oligochaeta Reproduction usually monoecious cross-fertilize by
exchanging sperm clitellum testis

43 Ecology Earthworms are essential soil aerators
If all the material ever moved through earthworms was piled up, the heap would rise 30miles , more than 5 times the height of Mount Everest!! Worm Grunting: A saw or leaf spring of a pick-up 1st phyla we will talk about and what we will cover in the lab today is… stob

44 Class Hirudinea 1st phyla we will talk about and what we will cover in the lab today is…

45 Class Hirudinea usually freshwater but there are some marine and terrestrial species no septa between metameres no setae have 2 suckers

46 Class Hirudinea have an extendable proboscis for feeding

47 Class Hirudinea usually have a fixed number of segments (34)
each metamere consists of several annuli (think accordion) 1 metamere annuli

48 Class Hirudinea Locomotion
Lack septa between metameres, so they are incapable of moving like Oligochaetes. Instead, they use their anterior and posterior suckers to move. 1st phyla we will talk about and what we will cover in the lab today is…

49 Class Hirudinea Reproduction usually monoecious cross-fertilize by
exchanging sperm 1st phyla we will talk about and what we will cover in the lab today is…

50 Ecology Although some leeches are parasitic blood suckers (can be temporary or permanent), many are predators. 1st phyla we will talk about and what we will cover in the lab today is…

51 Ecology Leeches have been used medicinally since the 19th century.
Currently they are used to increase blood flow following reconstructive surgery Hirudin is a powerful anticoagulant that is found in the salivary glands of leeches 1st phyla we will talk about and what we will cover in the lab today is…

52 How do the Annelids fit in?
Oligochaeta Hirudinea Polychaeta Nematoda Rotifera metamerism Nemertea Platyhelminthes Cnidaria Porifera eucoelomate protostome unknown common ancestor