Earthworm Dissection

Students will use the following tools for the earthworm dissection Scalpel Probes Dissecting Pins Rubber Padded Dissecting Tray

Scalpel

Probe

Dissecting Pins

Dissecting Pan

Before you start dissecting, find the following: Mouth Setae – the bristles used for locomotion. They are located by rubbing your fingers along the earthworm’s body. They are often times easier to feel than to see. Sperm Duct Clittelum

Sperm Duct sperm moves along here from sperm duct to another worm Sperm Groove sperm moves along here from sperm duct to another worm Sperm Duct Oviduct tube through which eggs pass

Clittelum makes mucus

Setae – bristle like structures that help the worm move

Mouth Pin your worm at the tip of the mouth and at its midpoint.

Continue your cut to the mouth Start your incision 2 cm behind the clittelum. Make sure not to cut too deeply.

Begin to separate the skin using pins

Pin the skin back as you go along the cut Pin the skin back as you go along the cut. Angle your pins outward so that are out of the way.

As you pin the skin back, take your probe and break the partitions between the segments. These are called Septum.

A comparison of systems…

Circulatory System “heart” “veins” carries blood to the “heart” “arteries” carries blood away from the “heart”

Aortic Arches - surround the esophagus and function in pumping the blood throughout the body

Aortic Arches – Earthworms have 5 pair of these simple hearts.

Aortic Arch

Ventral Blood Vessel- carries blood from the aortic arches to the rest of the body

Dorsal Blood Vessel- Returns blood to the aortic arches and has valves to prevent backflow

Digestive System Food goes from the: Mouth Pharynx Esophagus Crop Gizzard Intestine Anus

Mouth- opening at the end allowing the intake of food consisting of particles of both living and dead substances 25

Mouth

Pharynx- moves food from the mouth to the esophagus

Pharynx

Esophagus- Carries food between the pharynx and the crop

Crop – Stores food

Crop

Gizzard – grinds food

Gizzard

Intestine – Digests food

Intestine Dorsal Blood Vessel

Anus – where excrement (poop) comes out

Nervous System Ganglion- group of nerves. In the earthworm, there is a pair of ganglia in each segment and a cerebral ganglia acts like a brain

Brain

Nerve Cord and Brain

Ventral Nerve Cord- connects the ganglia in each segment of its body with the cerebral ganglia. It coordinates movement

Ventral Nerve Cord

Ventral Nerve Cord

Reproductive System Earthworms are hermaphrodites which means they have both male and female body parts

Seminal Vesicles- store sperm produced by the earthworm

Seminal Receptacles paired organs that store sperm received from another worm during copulation