//
you're reading...

Behavior

What’s up with Whiskers?

Hanke, Wolf, and Guido Dehnhardt. “Vibrissal touch in pinnipeds.” Scholarpedia of Touch. Atlantis Press, 2016. 125-139. doi:10.4249/scholarpedia.6828

Figure 1: Harbor Seal with lots of whiskers. Source: https://commons.wikimedia.org/wiki/File:Kiotari_at_the_MMC_by_Aaron_J_Cohen.JPG

Figure 1: Harbor Seal with lots of whiskers. Source: wikimedia

For mammals without fingertips, there are whiskers (vibrissae). You know, those adorable little hairs at the end of cat and dog snouts? Whiskers have a much more important role than just aesthetics though; at their bases there are receptors that make them great for feeling.   Little information is available about the neurophysiological system of whiskers, especially for pinnipeds, flipper-footed marine mammals like sea lions, seals, and walruses. Part of this limitation is attributed to the difficulties of observing whisker use in the natural environment, i.e. underwater.

Observations so far have taught scientists that whiskers on pinnipeds are above the eyes, above the snout, and on true seal species, they are also above the nostrils (Figure 1). They count between 15-350 per side depending on the species; table 1 is basic summary of the number of whiskers on different pinnipeds.

Table 1: summary of whisker types of various pinnipeds

Table 1: summary of whisker types of various pinnipeds

Whiskers are anchored in a nerve heavy housing called the follicle-sinus complex (F-CS; see figure 2 in the original article for a well labeled diagram). The F-CS is a skin capsule with blood filled sinuses and a hair follicle. The sinuses supply nutrients and influence the whiskers ability to sense.

FC-Ss in pinnipeds are unique from other mammals, with the exception of the sea otter, because they have three sinuses: a ring sinus, a lower cavernous sinus, and an upper cavernous sinus. The ring sinus, and the lower cavernous sinus are common; the upper cavernous sinus is not well studied but is believed to protect sensory receptors from cooling by surround water.

Figure 2: Smooth (top) vs. Undulated (bottom) whisker types. Source: https://en.wikipedia.org/wiki/Whiskers

Figure 2: Smooth (top) vs. Undulated (bottom) whisker types. Source: wikipedia

Additional unique features of FS-C structures in pinnipeds are that ten times more nerve fibers are found in the deep vibrissal nerve than in terrestrial mammals, and the cross sectional shape of the hair shaft in pinnipeds is oval while in terrestrial mammals it’s round. The shape of the long cross section is variable between pinnipeds, either smooth and waved (undulated), depending on the species (Table 1; Figure 2).

Sinuses and cross sectional shapes both play an important role in whisker sensitivity because they influence elastic deformation. For harbor seals the unique undulated cross sectional shape decreases the vibrations brought on by swimming and causes the elasticity of the whiskers to decrease when submerged in water, both resulting in enhanced sensory receptions in the FC-S. Although neural responses in all pinnipeds were observed regardless of position, length, or cross section of the whisker, which suggests that they are all important for sensing.

Apart from social interaction on land, whiskers are typically reserved for underwater use so observations are difficult to make. Previous work concluded that evident from a lack of a developed biosonar (sensing by sound- like bats and dolphins) physiology and the presence of whiskers suggest that they are a vital part of sensing.

Direct touch experiments have been used to investigate whisker ability further. The experiment was designed so that at the sound of a buzzer a trained, blindfolded sea lion started to investigate objects.   From this experiment scientists learned that pinnipeds explore an object by moving their heads while the whiskers are in contact with said object. Similar experiments have been used to observe pinnipeds distinguish between shapes and surface structures. They appear to distinguish by size based on the number of whisker in contact with an object.

Figure 3: Harbor seal swimming. Source: https://en.wikipedia.org/wiki/Harbor_seal#/media/File:Pinniped_underwater.jpg

Figure 3: Harbor seal swimming. Source: wikipedia

Hydrodynamic experiments were used to access the whiskers ability to sense movement in the water column. In these experiments a trained, blindfolded seal followed a remote controlled submarine. The seal was able to track the trail if either it started at the same place as the submarine, or if the seal intercepted the submarines trail. Harbor seals are particularly sensitive to hydrodynamic vibrations because of their undulated whisker shape. They are able to detect between differences in vibrations depending on the size, shape, direction, and movement of their sources.  They use this type of sensing to feed, follow their young, and to center in air holes in iced regions (Figure 3).

Figure 4: Pinniped Global Range (yellow shaded areas). Source: https://commons.wikimedia.org/wiki/File:Pinniped_range.jpg#/media/File:Pinniped_range.jpg

Figure 4: Pinniped Global Range (yellow shaded areas). Source: wikipedia

A hot feature about the F-CS is that they generate abundant heat so ambient temperatures do not influence sensation, i.e. when the water temperature is very cold, the whiskers sensitivity does not change.  This is important for seals living in cold water because it enables them to hunt just as well as seals in warmer waters.  Pinnipeds with undulated whiskers (like some true seals) tend to live in low visibility temperate and arctic waters (because they are able to hunt in low visibilty), and pinnipeds with smooth whiskers are either benthic feeders or live in clear subtropical/tropical waters (Figure 4).   It is noted that in bottom feeding pinnipeds, like bearded seals and walrus, tend to have a greater number of whiskers over all, an observation attributed to the need for enhanced touch sensation.

All in all you may get the feeling that whiskers are important to pinniped survival.  They are used to feel out their surrounding and to hunt.  Future research on the neurological response to whisker sensitivity will help scientists understand pinniped behavior.

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 3 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 4 months ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 5 months ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 6 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 9 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 9 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 10 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 10 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 11 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 11 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 12 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 1 year ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
WP2Social Auto Publish Powered By : XYZScripts.com