Phylum Annelida

Phylum Annelida From the Latin Annellus a “______________”. ______________ body ______________ – segment in the body ________ Small ____________ structures ___________ in leeches ___________ divided by septa ______________ tissue 3

Phylum Annelida The segments of an annelids body are separated by __________________ called septa. Most of these segments are the ________ but a few are modified to perform special _______________ such a photoreceptors, antennae, etc. 4

Metamerism Septa Pygidium Prostomium Peristomium

Phylum Annelida Annelids range in size from the ______________________, of which Michrochaetus rappi (Michrochaetus michrochaetus) is the largest average length of _____ m (54 ins) and a record breaking specimen has been recorded that measured ____ metres (22 ft) in length, it was 2cm (0.8 ins) in diametre. The smallest Annelid known to science is Chaetogaster annandalai full grown at ___ mm (0.02 ins).

General Annelid Anatomy

Body Plan ________________ ________________ symmetry _______ coelom Annelids are the first major phyla showing _______________ (metamerism) which is advantageous to _______________, safety, and tagmatization

Feeding Annelids have a ___________ digestive system The digestive tract is a long tube from the _______ to the _______. Their system contains mouth, ___________, esophagus, ________, ___________, intestine and anus They have a pharynx which is used to ________ up the larger particles of food. 9

Feeding Some annelids are ______________. Carnivorous annelids can _________ the pharynx through the mouth. These have two or more sharp ______ attached to it which are used to catch its prey. In earthworms the pharynx acts like a _______ pulling in soil and detritus through the mouth and ___________ it into the gut. In ___________ annelids the pharynx is used to suck _______ from the host. Some aquatic annelids are _______ feeders and use __________ structures to catch food particles.

Respiration Aquatic annelids breathe through ______. Many annelids take in ___________ and give off carbon dioxide through their ______. The skin must stay _________ for this type of gas exchange to occur. ______________ annelids secrete a thin protective coat called a __________ to hold moisture around them. 11

Circulatory System Annelids usually have a ___________ circulatory system with ______ blood vessels running the length of the body. In earthworms there are several ______ vessels connected to these blood vessels in the _____________ part of the worm. The ring vessels are _____________ and contract in rhythm so they are sometimes referred to as _________. They do help _________ blood through the system. In other annelids the blood is moved around by the worms _____________. 12

Closed Circulatory System 13

Excretion Solid waste is removed through the anus while waste resulting from ___________ activity is removed by a pair of ___________ in each segment of the body. 14

Nervous System Annelids have a well developed nervous system. ________ organs are most developed in the _____________ marine annelids. They often have sensory ___________, photoreceptors, two or more eyes, and ___________. 15

Nervous System cont’d A statocyst is an organ used to detect _________ while they are in the water. Many other annelids have simpler sensory systems like the earthworm. They rely only on _______ in their skin to sense their environment. 16

Nervous System Fig. 17.15 17 17

Movement Annelids have ______ major groups of muscles they use to move. ___________________ muscles run from the front to the rear. These make the worm __________ when they are contracted. The other group runs in __________ around the worm. When they are contracted they make the worm __________. These two muscle groups are used together to help the worm __________ forward. 18

Movement

Setae – help in movement

Reproduction Most annelids reproduce _____________ but a few can reproduce by ___________. Oligochaetes are ______________________ and during copulation they line up facing in the ___________ direction The ___________ secretes a mucous that holds the worms in place Later, the clitellum acts as a ___________ where the fertilized _____ develops 21

Earthworm Reproduction 22

Trochophore larva Apical tuft Stomach Ciliary band Mouth Anus

Annelid development

Classification Class Polychaeta (many hairs) Class Oligochaeta (few hairs) Class Hirudinae (leeches)

Class Polychaeta Many _______ Parapodia = “____________” Characterized by paired _______________ appendages on the segments. The appendages are tipped with ___________ that help the move about. They live in the _________, usually around reefs. 26

Fig. 17.3 27 27

Class Polychaeta Parapodium Head Tentacle 28

Polychaete Worm _____________ Jaw Tentacle Everted pharynx Palp Eye Cirrus Parapodium 29 29

Nereis 30

Class Polychaeta Fireworm 31

Sedentary Polychaete Lugworm Fig. 17.5 32 32

Fig. 17.4 33 33

34

Pelagic* Polychaete *Drift in the open ocean 35

36

37

38

Class Oligochaeta Few _________ have bristles but they are much ___________ and help the earthworm ___________ through the soil. ___________ _____ parapodia ________________ Both male and female parts 39

Earthworms play an important role in soil fertility Return ___________ to soil by decomposing dead leaves and organic matter Burrowing allows ____ and water to penetrate to roots Tunnels __________ soil so roots can grow more easily “intestines of the earth” -Aristotle 40

Lumbricus terrestris - earthworm __________ soil Exceedingly important in soil ____________, particularly in temperate areas. Without them, ________________ and perhaps the whole of human society as we know it would never have evolved. 41

External Structures of an Earthworm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. External Structures of an Earthworm

The Anatomy of an Earthworm Section 27-3 Anus Clitellum Circular muscle Longitudinal muscle Nephridia Ganglia Ring vessels Reproductive organs Ventral blood vessel Ganglion Brain Mouth Dorsal blood vessel Crop Gizzard Body segments Setae

Fig. 17.12c

Body wall Epithelium Circular muscle Longitudinal muscle

Class Hirudinea - Leeches No ______ Anterior & posterior _________ Most live in ________ water Feed Invertebrates Body fluids ________

Class Hirudinea Usually no more than __ cm in length but some tropical species can reach ____ cm. After they attach to a host they release a substance called ___________ into the wound. This keeps the blood from ___________. A leech can take in up to ____ times its weight in blood during a single feeding. 47

48

49

50

51

Fig. 17.21

PARASITIC SEGMENTED WORMS LEECHES Medical uses