Phylum Annelida

What is the prominent infolding of the intestine called?

Typhlosole

What do most annelids have that lie above the pharynx?

Bilobed dorsal ganglia

What does the name Oligochaeta mean?

Few setae

Where is each nephridium enveloped?

In a dense network of cappilaries

What is done with nitrogenous wastes?

Nitrogenous wastes which remain in fluid are expelled as a dilute urine through a small pore which opens externally.

What does the clitellum do?

Secretes a mucous coccon which will be shed with both eggs and sperm and within which the embryos will develop.

What are some of the characteristics of Annelids?

Triploblastic,eucoelomate, bilaterally symmetrical, protostomes, trochophore larvae, segmented, gas exchange through skin or gills, closed circulatory system, excretion by segmented paired nephridia, and anterior ganglia and ventral nerve cord

Next what should you locate?

Two small eye shaped openings on the fifteenth segment. These are the openings of the Vas deferens where the sperm are released

What is the typhosole?

An infolding of the dorsal wall of the intestine which increases surface area for absorption and slows the passage of food, allowing more time for digestion.

What does each nephridium consist of?

A bladder and coiled glandular loops which are fragmented during sectioning.

What kind of circulatory system do annelids have?

A closed circulatory system in which blood flows anteriorly along the dorsal blood vessel and is then pumped by five aortic arches (also called the hearts) down towards the ventral blood vessel.

What is beneath the epidermis?

A layer of circular muscle foloow by a feathery looking longitudinal muscle.

What extends from the ventral ganglia?

A longitudinal ventral nerve cord extends from the ventral ganglia and runs the length of the body.

What is just below the intestine?

A much smaller ventral blood vessel

What should you identify?

Aortic arches or hearts and the dorsal blood vessel in your dissected earthworm.

What are paradpodia?

Appendages that function in gas exchange and locomotion

In contrast to all flatworms and roundworms what are all annelid worms?

Are eucoelomates ( have a true coelom)

What does blood transport?

Blood transports nutrients absorbed by the intestine, oxygen that diffuses into the worm across the moist body surface, and metabolic wastes.

How do the structures look?

Both seminal vesicles and seminal receptacles are whitish bulb like strucutres however the seminal vesicles are much larger and wrap around the esophagus.

What is the outermost layer made up of?

Chloragogen cells which are modified peritoneal cells.

What is the space between the body wall and the intestine?

Coelom

What are important components in the in annelid movement?

Coelom, segmentation, and the presence of circular muscles and longitudinal muscles are important components in annelid movement

What is the excretory system in annelids?

Complex when you consider their fairly close relationship to nematodes.

What and how many is the phylum Annelida comprised of?

Comprised of aprxx 9,000 species of segmented worms

What do they lack which parts?

Do not possess a head and they have few bristles or setae.

In phylum Annelida the fluid of the body cavity also serves as what?

Hydrostatic skeleton.

What are some names of some common worms in this group?

Earthworms, freshwater worms, and the leeches

What are some examples of annelids?

Earthworms,leeches, and marine feather duster worms.

Soil mixed with detritus (dead organic matter?) enters what and is made up of what?

Enters the mouth and passes through the muscular pharynx, where it is compacted.

What should you notice when looking at the cross section?

Fairly thick, multi-layered body wall

Where does food go from the crop?

Food passes into a thick muscular gizzard and food is ground into smaller fragments by tiny stones that were ingested and stored in the gizzard.

What do segmental vessels and cappilaries do?

Form other connections between the ventral and dorsal blood vessels.

What does each nephridium have?

Has an internal ciliated opening, which lies in the coelom and collects fluid from the coelomic cavity in the adjacent anterior segment.

What are earthworms in reproduction?

Hermaphrodites, having both male and female reproductive organs.

What is then secreted and why?

Hirudin is then secreted into the wound to prevent coagulation of the blood.

Finally where does food enter?

In the intestine and inside the intestine digestion is completed and nutrients are absorbed into the circulatory system.

What is the innermost layer lining the lumen?

Intestinal epithelium(endoderm)

Where does food then pass?

Into the crop where it is temporarily stored.

How is the intestine structured?

It is multi- layered.

How is the ventral blood vessel attached?

It is often hanging off to one side attached to the intestine by a mesentery.

What do they lack that is seen in the polychaetes?

Lack specilization seen in Polychaetes.

What do most polychaetes have along their parapodia?

Many bristles or setae

How are many of the structures drawn?

Many of the structures such as the nephridia are drawn in three dimensions but appear as cross section on the slide so may look quite different.

What is a small description of polychaetes?

Marine annelids having well developed heads with eyes and antennae. Parapodia.

What are two common example?

Marine feather duster worms and fire worms

What is another way that leeches acquire their food?

Most are bloodsuckers which attack a variety of hosts.

What structures should you identify in the digestion of earthworms?

Mouth, pharynx, esophagus, crop, gizzard, intestine, anus.

What is another big group of annelids?

Oligochaetes

What is one of the main groups of annelid worms?

Polychaetes

What happens when the circular muscles are relaxed and the longitudinal muscles that run lengthwise in the segment are contracted?

Segment shortens

What does segementation do?

Segmentation improves control of movement and allows different parts of the body to be moved independently of one another.

What is an important adaptation seen in annelids?

Segmentation or subdivision of the body is an important adaptation

What should you be able to observe?

Seminal vesicles which contain the testes and seminal receptors which receive sperm released by its mate.

What does the annelid excretory system include?

Series of excretory organs called nephridia, one pair in every segment except the first three and the last one

How do you locate the dorsal surface of the earthworm?

Should have a dark line (dorsal blood vessel) running down it and the posterior end is farthest from the clitellum.

How do some leeches acquire their food?

Some leeches are predacious and capture their prey such as worms, snails, and insect larvae, and swallowing them whole.

What does the anterior end bear?

The anterior end also bears small pits that are sensitive to touch and odors.

How are body organs supported?

The body organs of eucoemlomate animals are supported in pouches of peritoneal tissue instead of floating freely within the cavity.

What does the digestive tube do?

The digestive tube is made up of structures that perform specialized digestive functions as food moves down the length of the earthworm.

What is just beneath the cuticle?

The epidermis

What does the epidermis play a significant role in excretion?

The epidermis of the worm also plays a significant role in excretion:For example about half of the total nitrogen excreted is in the mucous of earthworms secreted by the epidermis.

What is the large stained structure in the center?

The intestine

What is the location of the intestine?

The intestine begins at the posterior end of the gizzard and continues to the anus, where undigested material is expelled

What is just above the intestine and attached to it?

The large dorsal blood vessel(often stained red)

Suspended in the coleom on either side of the intestine what will you see?

The nephridia

What does the outer section of the body wall consist of?

The outer covering consists of a thin layer of cuticle

What happens when the circular muscles around the segment are contracted?

The segment gets longer because the fluid in the coelom cannot be compressed

At some point posterior to the clitellum push the intestine to one side of the body wall and decide what should you find?

The thin whitish thread located beneath the intestine in the ventral nerve cord.

How is the intestinal wall different from roundworms?

There are additional layers of tissue surrounding the intestinal epithelium.

What are the two small whitish lobes?

These are the bilobed dorsal ganglia or brains which are embedded in the muscle tissue on the anterior surface of the pharynx.

Leeches are what?What is their form?

They are orsoventrally flattened and tappered at both ends.

What do they do after attaching to the host?

They use their small blade-like jaws to open the hosts skin or they secrete an enzyme that dissolves the skin.

What does this facilitate?

This facilitates the reabsiorption of certain salts and minerals back into the blood in the capillary bed.

Why is this an important adaptation?

This is an important adaptation because many annelids live in environments where certain salts and other minerals are limited.

What happens in each segment?

Three small segmental nerve cords branch off from the ventral nerve cord and extend toward the dorsal surface.

What are the dorsal ganglia connected to?

Ventral ganglia which lie just below the pharynx.

Below the intestine what will you find?

Ventral nerve cord

Can they self fertilize?

While they produce eggs and sperm they cannot self fertilize and must exchange sperm with another worm.

What are wastes processed within?

Within the long, coiled, tubular nephridium.

What do eucoelomates display with their body plan?

display the most complex type of body plan

What kinds of habitats do they inhabit?

marine, freshwater, and terrestrial habitats

What do these layers include?

muscle, blood vessels

In animals that possess a true coelom what is the mesoderm derived lining of the body cavity called?

peritoneum

Where to find info on dissection?

pg 231

The innermost layer of the body wall is what?

single-layer of flattened cells called peritoneum.

What are the first and last segments modified to form?

suckers

Where does the compacted material then pass?

through the esophagus which is covered dorsally by three pairs of seminal vesicles and the aortic arches.