EQUIPMENT AND Dissection scope with illuminator

MATERIALS: Dissection kit with fine scissors

Dissection tray with 9 dissection pins

Preserved earthworm, Lumbricus terrestris, (rinsed)

1) Before you start, study the model of the earthworm, and identify the features listed below. Then examine your preserved specimen:

a) Counting only entire segments, how many are there anterior to the clitellum?

b) Feel for the rows of setae along the lateral/ventral surface.

c) Locate the sperm duct (vas deferens) openings (larger, puffy) (segment 15)

d) Locate the oviduct openings (tiny indentations) (segment 14)

2) Make the dorsal cut exactly in the middle of the back before you pin down the specimen. (Dorsal side is darker than ventral.) Snip very shallowly from the clitellum anteriorly until you reach the first segment. Do not cut underlying organs.

3) Remove the stage clips from the dissection scope and place the dissection pan so that it is well back and balanced on the stage. Pin the specimen so that the first segment is at one side of the view, with the ventral side down: Gently separate the skin from the underlying fascia (web-like fibers attaching the skin to the organs below) and pin open back to the clitellum using 6 more pins.

4) Identify and illustrate:

Gastrointestinal tract pharynx initial receiving chamber for food, covered with fascia

esophagus swallowing tube from pharynx to crop (under hearts)

crop storage chamber for ingested food, usually dark

gizzard grinder to macerate food (tough, usually light))

intestine performs digestion and absorption

typhlosole dorsal invagination in gut, seen in cross section

Reproductive system seminal vesicles 3 pairs, large, white, fragile, contain testes

seminal receptacles small, in segments 9 and10

Circulatory system five pairs of hearts surround the esophagus, (segments 7-11)

dorsal blood vessel connects pairs of hearts

ventral blood vessel visible when intestine is pushed to side

Nervous system ganglia dual structure above pharynx front ("bikini")

nerve cord visible when intestine is pushed to side,

lateral nerves branch off of nerve cord within each segment

Excretory System metanephridium (serves as a kidney) In cross section.

CLEAN UP: Wash and dry dissection tools, rinse dissection tray and invert to drain. Dispose of earthworm, replace dissection scope and illuminator with properly wound cord back in its home in the storage cabinet.