Animal Diversity Exam 2 - Phylum Annelida

What does “polychaete” translate to and what is it referring to?

“many haired”; these organisms are covered in setae/hair

What does “oligochaete” translate to and what is it referring to?

“few haired”; these organisms lack setae/hair

Describe the following body features of an annelid:

1. Germ layers

2. Body cavity

3. Symmetry

4. Development (__stome,cleavage type, embryo type, __coelous)

5. Skeleton

6. Metamerism

1. Germ layers: Triploblastic

2. Body cavity: Coelomate

3. Symmetry: Bilateral

4. Development: protostome, spiral cleavage, mosaic embryo, schizocoelous

5. Skeleton: hydrostatic

6. Metamerism: YES! coelomic cavity is highly developed; each segment has its own independent cavity.

What is the taxonomic structure of Phylum Annelida?

- Family Chaetopteridae — parchment worms (not currently classified to the class/ordinal level)

- Class Errantia — free-moving polychaetes

- Class Sedentaria –- some polychaetes, oligochaetes and leeches

• - Order Clitellata

  • - Family Lumbricidae –- earthworms

  • - Family Hirudinidae –- leeches

Describe the unique metamerism of annelids.

Each segment:

• is walled off from other segments via a septum

• has its own set of metanephridia (most segments)

What muscle types are present in annelids?

Circular and longitudinal

Epidermis in annelids is covered by ___, which helps retain moisture.

Cuticle

Describe the excretory system of an earthworm (Lumbricidae).

Uses metanephridia; some species will pass waste between segments to be processed in other segments; works like a simplified mammal kidney

In what three ways do annelids respire?

1. Cutaneous respiration (diffusion through cuticle): earthworms and burrowing polychaetes of Class Sedentaria

2. Gills: feather duster worms and lugworms of Class Sedentaria

3. Parapodia: tube-dwelling polychaetes of Class Errantia

Which annelid class has parapodia?

Class Errantia

What is the larval stage of Class Errantia?

Trochophore larvae

What are the functions of parapodia in Nereis?

Useful for locomotion, sensing, anchoring (if a burrowing taxa), and respiration (especially important for respiration in Nereis as they have no gills).

What structures make up the parapodia (Class Errantia)?

Each parapodia has 2 lobes:

- notopodium (dorsal/top lobe)

- neuropodium (ventral/bottom lobe)

Each lobe has an aciculum (a chitinous spine) running through it for support

Setae on the parapodia help with movement, anchoring, and sensing

Prostomium (Nereis):

Head region (NOT considered first true segment)

Peristomium (Nereis):

First true segment

Pygidium (Nereis):

Last segment bearing anus and 2 cirrus extending outward

Which Class of Annelids makes up the majoriy of Phylum Annelida?

Class Sedentaria (~2/3ds of all Annelids)

T/F: earthworms don’t have setae.

False; earthworms do have setae.

Describe, in detail, the feeding behavior of earthworms (Lumbricidae).

Mouth > pharynx > esophagus > crop > gizzard > intestine > anus

1. Decaying organic matter and sediment is moistened by the mouth and sucked in by the pharynx like a straw

2. Crop: stores food

3. Gizzard: grinds food up, separates food from soil particles

4. Intestine: digestion and absorption

• Typhlosole: tissue that extends into lumen (middle) of intestine; increases surface area = increased absorption; creates a “U-shape” on a cross-section

  • Chloragogen cells: specialized cells lining the intestinal wall that synthesize glycogen and fats and help with transport

Describe, in detail, the reproductive and copulatory behavior of earthworms (Lumbricidae).

Mostly monecious with simultaneous outcrossing (sperm is deposited in both individuals during copulation)

Somites 9-15 contain reproductive tissues:

• 15: where sperm is released from

• 9/10: Seminal recepticles

• 14: where eggs are released from

1. Copulation:

• individuals line up in opposite directions

• sperm released from segment 15 and travels posteriorly in seminal groove to be transferred to the seminal receptacles (somites 9 and 10) of its mate where it is stored for future fertilization

2. Post-copulation:

• cocoon moves anteriorly; once it reaches segment 14, eggs are released into cocoon

• once the cocoon + unfertilized eggs reach segments 9 and 10, the sperm fertilizes the eggs as it moves across seminal receptacle

• cocoon w/ fertilized zygotes slip off anterior end of worm

• young mature within cocoon

Do leeches always have the same (set) number of segments?

Yes

Why do leeches appear to have more segments than they really do?

Most species have 3 annuli per segment (areas where it looks like there should be an interior septa, but there isn’t one)

T/F: leeches have reduced or no internal septa.

True

What adaptations do leeches have to accommodate being fluid-feeders?

1. Gut is specialized for storing fluids/blood (expandable and stretchy)

2. Many pouches (ceca) off the intestine

What do leeches use for locomotion?

They use their suckers to move around inchworm-style

How many suckers do leeches have?

2; one anterior sucker and one posterior sucker.

Where are the sensory organs located in leeches?

The central annulus of each segment