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Molluscs & Annelids Zoology LS2014, Donald Winslow 3 March 2008,

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Presentation on theme: "Molluscs & Annelids Zoology LS2014, Donald Winslow 3 March 2008,"— Presentation transcript:

1 Molluscs & Annelids Zoology LS2014, Donald Winslow 3 March 2008,
Following Hickman, et al., 2008 Ch. 16 (pp , ) Ch. 17 (pp )

2 Molluscs & Annelids Protostome Spiral cleavage Mosaic development
Eucoelomate Schizocoelous coelom formation Many have trochophore larvae

3 Phylum Mollusca Coelom usually only around heart
Unsegmented with organ systems Trochophore & veliger larvae in many Gills (ctenidia) or lung Circulatory system usually open Variation in body size Mantle, mantle cavity, shell, foot, head

4 Molluscan characteristics
Radula & odontophore Visceral mass Surface epithelium, cilia & mucous glands Metanephridic kidneys (drain from coelom) Empty liquid waste into mantle cavity Usually nerve ring & paired ganglia Mostly dioecious

5 Phylum Mollusca Classes Caudofoveata & Solenogastres
Class Monoplacophora—one shell plate Class Polyplacophora—8 shell plates Class Scaphopoda—tusk shells Class Gastropoda—snails & slugs Class Bivalvia—clams, mussels, etc. Class Cephalopoda—squid, octopus, etc.

6 Class Gastropoda Snails w/ coiled or uncoiled shells
Slugs w/ no shells Pulmonate land snails & slugs Marine nudibranchs (no shell, “sea slugs”) Poisonous cone shells Conchs, whelks, limpets, abalones

7 Class Bivalvia Clams, scallops, mussels, oysters
Zebra mussels, shipworms, giant clams

8 Class Cephalopoda Giant squid Cuttlefish Octopus Chambered nautilus

9 Phylum Annelida

10 Developmental characteristics
Spiral cleavage & mosaic development Protostome Eucoelomate Schizocoelous coelom formation Segmentation (metamerism) External rings called annuli Few differences between segments

11 Morphological characteristics
Bilateral symmetry Chitinous setae (bristles) Parapodia in Class Polychaeta Cerebral ganglia 2 ventral nerve cords with giant axons Ganglia & lateral branches in each segment

12 Specialization of annelid head
Tactile organs Taste buds Statocysts Photoreceptors

13 Annelid circulatory system
Closed Dorsal blood vessel pumps blood Aortic arches control blood flow Ventral blood vessel Respiration by skin, gills, or parapodia

14 Digestion and excretion
Complete digestive tract Unsegmented digestive tract Nephridia in each segment remove waste from blood.

15 Reproduction of annelids
Complete regeneration when injured Monoecious or dioecious sex Trochophore larvae in some taxa Budding in some taxa

16 Sections of annelid body
Prostomium (“head”) Somites (“body”) Pygidium (“tail”)

17 Annelid coelom Septa divide coelom and separate segments.
Fluid in coelom provides hydrostatic pressure for “hydrostatic skeleton”. Epidermis secretes cuticle. Peritoneum (visceral & parietal) Mesenteries (dorsal & ventral)


19 Phylum Annelida Class Polychaeta Class Oligochaeta
Mostly marine Some tube-dwelling Mostly dioecious (separate sexes) Class Oligochaeta Earthworms and other terrestrial & freshwater species Class Hirudinida—leeches and relatives

20 Examples of polychaetes
Nereis Eunice viridis—Samoan palolo worm Featherduster worms Chaeopterus

21 Earthworms Mix, aerate, hydrate, & fertilize soil
React to many stimuli, learn Hermaphroditic, testes, ovaries Seminal vesicles, oviducts, seminal receptacles Clitellum, fertilization in cocoon Freshwater oligochaetes with gills

22 Leeches Ectoparasitic Anterior & posterior suckers Medicinal uses

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