Florida Manatee Hydrodynamics Sensory System
Manatees have a hydrodynamic stimulus using vibrissae that allows them to detect obstacles in their environment. These vibrissae are located all over their body and are used to navigate their environment. Each vibrissa is known as a follicle-sinus complex (Gaspard, 2017). These vibrissae act as a nerve network and allow the manatee to detect its entire environment around it. Vibrissae are ~30 times denser on the facial region than on the post-facial body (Gaspard, 2017). This allows them to easily navigate as they can detect obstacles in front of them because of how sensitive these vibrissae are. Manatees also have poor eyesight, which means that the post-facial vibrissae could be used to easily detect food, and what is not food. They are also able to manipulate things with their lips and can use this to identify objects as well as sift things from their food.
Aquatic mammals face a unique challenge as water is much denser than air. This causes constant deflection of their vibrissae when navigating or moving in general (Gaspard, 2017). This is why Manatees have such dense vibrissae, as they need to compensate for the density of the water. If the vibrissae are not dense enough, the water will cause them to move with any movement and the manatees would not be able to distinguish anything as they are constantly getting activated. For example, we don’t notice air pressure even though it is there. We don’t notice as it is essentially irrelevant due to it being a constant pressure. We do notice changes in pressure like how manatees do with their vibrissae. The vibrissae are dense enough to not move with movement in the water but thin and sensitive enough to feel changes in their environment.
Sirenians have an array of hairs and bristles on their face that are in a pattern involving nine distinct regions on their face (Reep, 2011). This probably works similar to our tongues and allows manatees to distinguish where and what things are. This probably makes manipulating things with their lips much more efficient as they have a heightened sense of touch.
The nine distinct regions on the face of sirenians is unique and fascinating. This could be tested by stimulating different sections of the face with different materials. The use of different materials will show if they can distinguish between different materials through texture. To see if they can tell where they are being touched, tests involving touching different sections of the face or a few at ounce would be useful. This could be more accurately tested by having the manatee touch a material, and have it locate the same material. The Manatee would feel the material and would have to touch each of the materials to determine what the same one is. This could be determined by having the manatee hit a corresponding button of sorts to determine which one it has recognized. If the manatee finds the right corresponding material and push the corresponding button, it will get rewarded, and a new material would be selected. This could be used to see how many different materials and how sensitive their face really is, as well as see if they recognize materials. This would give a good perception of how they navigate their environment, as they may use this to determine where they navigate. What this means is that they navigate by touch and may avoid certain textures that are deemed dangerous. This goes the same for textures that are deemed safe, as this is probably how they determine what to eat and where to go.
Work Cited
Gaspard, J. C., Bauer, G. B., Mann, D. A., Boerner, K., Denum, L., Frances, C., & Reep, R. L. (2017).n Detection of hydrodynamic stimuli by the postcranial body of Florida manatees (Trichechusn manatus latirostris). Journal of Comparative Physiology A, 203(2), 111–120.nhttps://doi.org/10.1007/s00359-016-1142-8
n Reep, R. L., Gaspard, J. C., Sarko, D., Rice, F. L., Mann, D. A., & Bauer, G. B. (2011). Manatee vibrissae: Evidence for a “lateral line” function. Annals of the New York Academy of Sciences, 1225(1), 101– 109. https://doi.org/10.1111/j.1749-6632.2011.05992.x