Aristotle describes 5 senses touch, hearing, vision, smell, and taste in living organisms but now scientist explain many senses in vertebrates and Invertebrates. Here we provide you with the brief description of all of them.
Sensory Receptors in INVERTEBRATES
These receptor sense changes in pressure. And they are more likely to be present in insects, Jellyfishes, and ocean-dwelling invertebrates. Scientist don’t know the exact structure of this.
These receptors response to the chemical changes. It is the universal sense. It is first discovered by zoologist in animal kingdom. Even though the unicellular Protozoa lifestyle depends upon Chemo receptors . They used this for capturing prey , defence , mating , avoidance behaviour to salt , salt ,alkali and acidic stimuli.
Silkworm uses chemo receptors present on their antennae to locate their mates. Female silkworm secretes “Bombykol” as a sex attractant.
These receptors are used to detect gravity. Gravity can be measured by invertebrates. With the structure called statolith. Animal use this stone-like statolith, to find their position in space. They also use this to find their movements.
These are found in gastropods, insects, jellyfishes and worms etc.
These detect the water content, present in the atmosphere. Animals orient their physiology and modify it with respect to moisture in the environment.
These are the receptors that respond to sound. They are present mainly in the insects. Grass hoper and cicadas have photoreceptors which are called tympanic or tympanal organs.
These detect light. All these receptors have light sensitive pigments in it, for example chlorophyll and carotenoids etc.
Euglena has photoreceptors called stigma and phototoreceptor is the swelling present at the base of the flagellum however stigma is the shield of it that, contains red carotenoid granules. Stigma only helps in finding light direction.
Multicellular animals contain light receptors that can be classified into 3 basic forms.
Ocelli, Compound Eye, and Complex Eye.
These are commonly called stretch receptors. Present in insects as a receptor that detects the internal organ response to stretching that is occur mechanically inside the body.
These are touch receptors, present in the epithelium or outer surface of animal or the projection of epithelium Bristles, spines , setae, and tubercles are the examples of it.
As name show these detect temperature stimuli. for example leeches draws towards warm blooded host through heat sensing mechanism .
Various receptors are present in vertebrates that detect specific stimuli and generate generator potential, however in aquatic vertebrates, a lateral line system is present for sound, electromagnetic, and pressure detection. In terrestrial animals Ears, tympanum are present. For vision Compound Eyes are present. For smell Nostrils, Nose, etc are present which detect the smell, In some animals amphibians and reptiles tongue is also use for smell detection. Similarly for taste tongue is present. Special mechanoreceptors are present on the skin as well.