The Victorian naturalist . family and generic placementand relationship and is used as an im-portant character in taxonomic studiesof land snails. Two examples of dif-ferent tooth shape and form are givenof Victorian land snails. The smallrasping teeth of the herbivorous snailHelicarion sp. (Fig. 3) is contrastedto the long lance-shape teeth for hold-ing prey of earthworms or slugs as inthe carnivorous snail Rhydda capil-lacea (Fig. 4). Because of the diflerentfood and because these two speciesbelong to totally different family andsuper-family groupings, the shape ofthe teeth are totally diffe
The Victorian naturalist . family and generic placementand relationship and is used as an im-portant character in taxonomic studiesof land snails. Two examples of dif-ferent tooth shape and form are givenof Victorian land snails. The smallrasping teeth of the herbivorous snailHelicarion sp. (Fig. 3) is contrastedto the long lance-shape teeth for hold-ing prey of earthworms or slugs as inthe carnivorous snail Rhydda capil-lacea (Fig. 4). Because of the diflerentfood and because these two speciesbelong to totally different family andsuper-family groupings, the shape ofthe teeth are totally different. Most snails also have a jaw whichacts in conjunction with the radula infood gathering. Emptying into thebuccal cavity are the pair of salivaryglands which secrete mucus and prob-ably some enzymes to commencedigestion of the food. The food sub-stances are then passed down theoesophagus into a large holding sack,the crop. This in turn leads to thestomach from where several blind-ending diverticulae lead into the diges-. Figure 3. Scanning electron microscopepicture of the radula of a herbivoroussnail Helicarion sp from Gray, Tasmania.(640x) September/October tive gland or liver. Digestion is bothintra-cellular and extra-cellular by acomplex battery of enzymes. One of the most unusual featuresfound in some herbivorous snails isthe production of a cellulase, anenzyme which will directly affect thebreakdown of cellulose. Land snailsare one of the very few types of ani-mals which produce this enzymedirectly; even most herbivorous mam-mals such as cows and sheep have torely on a cellulase produced for themby intestinal bacteria. Because of theircellulase, snail Hver extracts were usedin early commercial fibre manufactur-ing processes. After digesting processes have takenplace the food residues are passed intothe rectum and voided as faeces. Life duration The Hfe of a snail is often limited toa year. A snail hatches when onewhorl of the shell has developed, thesize depending on t
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Keywords: ., bookcentury1800, bookdec, booksubjectnaturalhistory, bookyear1884
