Carnivory and herbivory

1. Carnivory and herbivory Capture and ingestion: teeth, mouthparts Snail teeth: odontophore Gut tubes: assembly-line processing

2. Carnassial teeth • The shearing (scissor-like) action of carnassial teeth in modern carnivores is generated when the inner surface of the fourth upper premolar (blue) passes outside the outer surface of the first lower molar (red). This upper and lower-jaw tooth combination is characteristic of both feliform (cats) and caniform (dogs) carnivores, and is thus a synapomorphy* for these groups. Carnassial teeth in a sabretooth cat (Smilodon) The shearing (scissor-like) force of the carnassials acts to create shear strain in bones. The cusps of the upper and lower teeth are shaped to cradle and contain any roll of the cylindrical bone; the shear forces of the closing jaws, delivered from above and below, should be offset transversely, i.e., the teeth don’t line up on each other, just as the cutting blades of scissors are offset. *From Wikkipedia: a synapomorphy is a trait shared by two or more taxa (in this case families of cats and dogs) and their most recent common ancestor whose own ancestor does not possess the trait. So the common ancestor of cat and dog families had carnassials but not its ancestor. From web: Steven M. Carr

3. Though it seems odd to refer to canine (dog) teeth in the cat family, and other non-dog families, it is the huge canines that give the sabre-tooth cats their notoriety. The way these teeth worked in bringing down prey has been an ongoing subject of debate. Papers to read (courtesy of Kendra Lahut) offer some thoughts on how Smilodon used its canine teeth • McHenry, C.R. 2007. Supermodeledsabercat, predatory behavior in Smilodonfatalisrevealed by high-resolution 3D computer simulation. Proceedings of the National Academy of Sciences USA 104: 16010: 16015. • Christiansen, P. 2007. Comparative bite forces and canine bending strength in feline and sabretooth felids: implications for predatory ecology. Zoological Journal of the Linnean Society 151: 423-437.

4. Narwhal whale • The narwhal is a medium-sized (body length 4-5 m) toothed whale living in the Canadian Arctic and Greenland waters. Males have a long, straight, helical tusk, an incisor tooth modified and extending asymmetically from the upper left jaw, 2-3 m long. The species feeds on bottom-living fish, e.g, halibut, at depths of up to 1500 m under dense pack ice.These whales are remarkably able deep divers: 800 – 1500 metres! • The tooth that is modified into a tusk is not used to help obtain food.A female narwhal has a shorter, and straighter tusk. Pictures taken from web

5. Excluding seeds and fruits herbivory on green tissue of plants is characteristic of three large groups of animals: gastropods, Orthoptera (grasshoppers and allies) and ruminant tetrapods. In the mouth region of a gastropod there is a skeletal element, a plate called the odontophore, that acts as backing for a ribbon of horny (keratin) teeth, the radula. The odontophore is a very mobile skeletal element and can be protruded far out through the mouth of a snail; this deployment involves antagonistic protractor and retractor muscles.Theodontophore can be applied against substrate (rocks, coral heads, aquarium glass) that is covered with greeh algae. The ribbon is then pulled to and fro by muscle antagonists and slips over the edges of the odontophore. The radula, a ribbon of ‘emery cloth’, rasps off algae as the radula retracts and the alga is ingested by the snail. Gastropoda: phylum Mollusca: snails are examples of a microphagous herbivores

6. Teeth of the radula of gastropods are species diagnostic Pictures from the web