Lumbricus terrestris - preserved specimens for dissection

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Randall Haynes
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1 Lumbricus terrestris - preserved specimens for dissection External Anatomy: Prostomium (observe under dissecting microscope for external sensory organs), peristomium, clitellum, setae (dissecting microscope), metameres, pygidium (periproct) Internal Anatomy: Pharynx, Anterior ganglion (brain), pharynx (is it jawed?), pseudohearts, esophagus, esophageal glands, calciferous glands, crop, gizzard, intestine, nephridia, dorsal and ventral bv Associate structures with specific segments! What are the functions of these structures and how do they relate to the animal s lifestyle? Male: Seminal receptacles, seminal vesicles, testes Female: Ovary Are these animals monecious or diecious? - model: Some of the smaller features such as the pseudohearts and anterior ganglion, nephridia and some of the reproductive structures are small and as such easier to find on the model

2 Lumbricus terrestris - cs slide (pre and post clitellum) Body Wall: Cuticle, epidermis, circular muscles, longitudinal muscles, setae Excretory: Nephrostome, nephridium bladder and nephridiopore Body cavity: Coelom, dorsal bv, ventral bv, nerve cord (dorsally or ventrally located?), chloragogue cells (Store nitrogen and neutralize toxins. What is their equivalence in vertebrates?),, typhlosole (dorsal flap in intestine, anterior or posterior to clitellum?), digestive tract (can you tell which part of the digestive tract you are looking at?) lined with gastrodermis. You may need to look at more than ONE slide in order to find all these different structures!

3 Nereis virens - preserved specimens for dissection Is this an errant or a sedentary polychaete? How can you tell? External anatomy: Prostomium, peristomium, prostomial palps and tentacles, eyes (located on the pro- or peristomium?), jaws, tentacular cirri, pygidium with caudal cirri Appendages: notopodium, neuropodium, dorsal cirrus, ventral cirrus, setae (Falcigers vs spinigers. What is the difference? Simple vs compound setae? What is the difference?), aciculum (acicula) Internal anatomy: alimentary canal (What is the difference between Nereis and Lumbricus?), mesenteries, eggs (if animal is reproductive, will be loose in coelomic fluid, so make a wet mount of the coelomic fluid), dorsal and ventral bv Other Polychaete worms: Chaetopterus sp. parchment tube worm -peristomium extended into a collar, greatly enlarged notopodia behind the 10 th segment (parapodia appear fan shaped), suckered neuropodia

4 refer to textbook etc. information to understand how the lifestyle of the animal works with its morphology! Sabella sp. fan worms - crown of tentacles called radioles, parapodia reduced or absent Amphitrite sp. - - elongated gills and tentacles, parapodia reduced or absent Aphrodite aculeate - body covered in a dense mat of setae, received its name due to its ventral appearance (which is what?)

5 Hirudo medicinalis (most popular preserved specimen) - medicinal leech - preserved specimens for dissection (may be Hirudo) External anatomy: Dorsal eyes, (anterior to mouth) metameres and annuli (subdivisions of the metameres, not true segments, often obscure the 32-4 true segments), anterior sucker (central mouth), jaws? (presence of jaws indicates that you are looking at Hirudo, posterior sucker, anus, male pore (segment 10, penis might be everted), female pore (segment 11) Internal anatomy: (you will have to cut ventrally, how can you tell dorsal from ventral surface?), buccal cavity (with jaws?), intestine, gastric caecae, rectum - slide, to find further internal features and compare to preserved specimen proboscis and proboscis cavity, male and female atrium (how do you distinguish?), ovary, testes, (vas deference), intestine, gastric caecae, rectum, dorsal anus

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CHAPTER 17. Annelids 17-1

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CHAPTER 17. Annelids 17-1 CHAPTER 17 Annelids 17-1 Characteristics of the Phylum Annelida Diversity Exhibit segmentation or metamerism Bodies composed of repeated units Each unit contains components of most MAJOR organ systems