Presentation on theme: "The Animal Clade Chordata Ancestral Choanoflagellate Cnidaria Hemichordata Echinodermata Extant deuterostomia Arthropoda Annelida Mollusca protostomia."— Presentation transcript:
The Animal Clade Chordata Ancestral Choanoflagellate Cnidaria Hemichordata Echinodermata Extant deuterostomia Arthropoda Annelida Mollusca protostomia coelomates Nematoda Rotifera pseudo- coelomates Platyhelminthes acoelomates radiata bilateria eumetazoa (true tissues) Porifera parazoa loss of chloroplast, colonial organization This cladogram omits several smaller animal phyla!
Animals Domain Eukarya Kingdom Animalia Phylum Mollusca 35,000 species making this the second-largest phylum of Animalia
Polyplacophora: chitons The most-primitive mollusc has 8 valves (plates) protecting its soft tissues beneath. The chiton foot attaches to rocks and the animal uses its radula to scrape organic material from the rock surfaces.
res/animal%20diversity/protostomes/chiton_ventral_surface.jpg After working hard to remove the suck rock organism from the rock, the ventral surface of the chiton shows the obvious mollusc features. gills foot mouth (radula inside)
The chiton has multiple eyes. Some are just light-sensitive spots. The primary eyes are of a lens-type. Many chiton species lack eyes.
mouth radula valve plates gonad heart pericardial cavity (coelom) mantle anus foot digestive gland nephridium stomach ventral nerve cord (not shown) This cartoon shows a longitudinal slice of a chiton with the three principal parts: foot (locomotion or attachment), visceral mass (internal organs), and mantle (secretes valves). auricle ventricle nephridiopore gonopore hemocoel dorsal aorta
As for all other molluscs, chitons use a radula to scrape their food from environmental surfaces. Below is a radula removed from a chiton mouth.
Gastropoda: snails and relatives (slugs) Snails have a single spiral-shaped valve (univalve) Slugs and nudibranchs have lost this feature. foot shell eye optical tentacle sensory tentacles gonopore
And now for a look inside our gastropod mollusc… The shell obviously provides a hard covering for the visceral mass. The snail shown here is a pulmonate, with a vascularized mantle cavity serving as a lung. Vascularizing this led to loss of the gills in most gastropods. The gastropods, are clearly hermaphroditic, and some are self-fertile. Trochophore larva: Veliger larva:
This is a slug, its mantle is reduced to a saddle and does not secrete a shell. The other features of the snail are all present. mantle foot skirt optical tentacles sensory tentacles
Here is the longitudinal section of an optical tentacle. The eye of the slug is a lens-type eye. retinal cell: 11. microvilli 12. pigment cell 13. light sensitive cell 1. digitate ganglion 2. collar cell 3. olfactory nerve 4. tentacle retractor muscle 5. lateral processed cell 6. lateral oval cell 7. optic nerve 8. accessory retina 9. lens 10. retina
Here is a micrograph of a longitudinal section of a snail eye olfactory ganglion olfactory nerve lens retina optic nerve The tentacle has all of the optical, sensory, and neural parts we expect for vision. The tentacle has all of the sensory, and neural parts we expect for chemical sensation too. The sensory tentacles have these features too.
pneumostome optical tentacles sensory tentacles mantle foot skirt The slug shows the pneumostome in the mantle for breathing.
These two slugs are showing mating behavior. The slugs are dangling on a slime thread and grip each other with their feet. The slugs evert their reproductive organs out through the gonopore. The organs unite and spermatophores are exchanged. Sperm are stored in a spermatheca for a week or more. Syngamy and deposition of zygotes occurs later.
graphics/jpegs/aopercu.jpg Bivalva: bivalves This group includes the clams, oysters, mussels, and scallops. Their body is typical mollusc too, but with two hinged valves (shells)
Here is a cartoon of a lateral view of the foot, visceral mass and mantle Adductor muscles to hold the valves together. Bivalves have gills rather than lungs. Their incurrent siphons take in plankton lodging in mucus. The mucus laden particles gather on the gills (palps) and enter the mouth. The mouth lacks the radula.
This cartoon is shows a plane of section perpendiular to the previous one. The foot can push a bivalve through sediments. The food-trapping gills are used for gas exchange. The heart pumps the blood into the hemocoel bathing the tissues. It goes through the gills for gas exchange. The blood then returns to the heart. Nephridia cleanse the blood of nitrogenous waste. hinge and ligament nephridium mantle shell gills foot gonad intestine heart
Here are three different molluscs. Between the valves of the bivales the mantle fringe is quite visible. With the valves ajar, the bivalve can carry out its filter feeding. If you swim nearby, the bivalve adductor muscles snap the valves shut.
How does the bivalve know you are swimming by? Eyes!
Here are close-ups of the bivalve eye and a cartoon of its structure. This gives the impression of being somewhat intermediate between a lens-type and a pinhole-type eye.
Tridacna crocea Gymnodinium microadriaticum
Cephalopoda: the chambered nautilus, squid, and octopus valve operculum tentacles eye The nautilus has gastropod features
This Caribbean reef squid is small. The giant squid is the largest invertebrate animal known…17 meters long…2 tons! Two grasping tentacles Smaller arms surround the mouth mantle fin eye chromatophores
Contrary to the filename, this is a Humboldt squid. It is certainly large, but is not the giant squid. Between the tentacles part of the beak is shown. The eyes face the mans knee and elbow. The mantle is in his lap and the fin is over his shoulder.
The squid eye is a lens-based eye, rather than a pinhole eye. Is this cartoon correct, based upon your dissection of the squid in class? retina lens Advantage: collects more light
Another cephalopod is the octopus. It obviously has eight tentacles surrounding the mouth…no, duh! This one is obviously swimming.
Here is another swimming octopus. The idea of cephalopod (head- foot) is shown nicely here. Behind one tentacle the siphon is showing the basis for jet-action locomotion among cephalopods.
Note: I am fairly certain that the animal shown above on the right is a squid, rather than an octopus: Squid eye What kind of eye does an octopus have?