Olfaction
Chemoreceptors are classified by their location. The sense of smell, or olfaction involves chemoreceptors usually located in the nasal passages. Sniffing the air for the sampling of chemicals can be energetically costly but some reptiles, such as the crocodile are able to close both the glottis and gular fold to momentarily isolate the nostrils and mouth. The floor of the pharynx is then depressed allowing fresh air to be exclusively drawn into the olfactory chamber allowing the animal to sample new chemicals without respiratory ventilation.
The vomeronasal, or Jacobson’s organ is a sensitive chemosensory organ commonly found in herptiles (demonstrated in the image above), with the exception of most turtles and crocodilians where is it absent or substantially underdeveloped. It is a secondary olfactory system that is especially sensitive to chemicals important in social or reproductive behaviour. Snakes and lizards will sweep the air with their tongues to sample for airborne particles, then retract the tongue into the mouth to deliver these chemicals to the vomeranasal organ. Many species are able to release chemical messages (known as pheromones) into the environment, which impacts on the behaviour or physiology of the recipient of the same species. They represent one avenue of communication between individuals and are often detected by specialised receptor organs. Pheromones are produced in exocrine glands and affect sexual activity (produced by the females when they are ready to breed and received by the males) or are used to demonstrate territoriality.
In plethodontid, or lungless salamanders, a pair of sunken grooves connects the front of the mouth to the nostrils. These nasolabial grooves help to transport chemical signals (such as pheromones or the scent from food) to the vomeronasal organ in the nasal cavities. These salamanders will additionally investigate by touching their nose to the substrate, known as “nose-tapping”, in order to gather chemical cues important for territory identification along the nasolabial grooves.
The vomeronasal, or Jacobson’s organ is a sensitive chemosensory organ commonly found in herptiles (demonstrated in the image above), with the exception of most turtles and crocodilians where is it absent or substantially underdeveloped. It is a secondary olfactory system that is especially sensitive to chemicals important in social or reproductive behaviour. Snakes and lizards will sweep the air with their tongues to sample for airborne particles, then retract the tongue into the mouth to deliver these chemicals to the vomeranasal organ. Many species are able to release chemical messages (known as pheromones) into the environment, which impacts on the behaviour or physiology of the recipient of the same species. They represent one avenue of communication between individuals and are often detected by specialised receptor organs. Pheromones are produced in exocrine glands and affect sexual activity (produced by the females when they are ready to breed and received by the males) or are used to demonstrate territoriality.
In plethodontid, or lungless salamanders, a pair of sunken grooves connects the front of the mouth to the nostrils. These nasolabial grooves help to transport chemical signals (such as pheromones or the scent from food) to the vomeronasal organ in the nasal cavities. These salamanders will additionally investigate by touching their nose to the substrate, known as “nose-tapping”, in order to gather chemical cues important for territory identification along the nasolabial grooves.
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