Star Nosed Mole

Question 1

Why is it important for the star-nosed moles to be fast hunters?

Answer 1

• they share their tunnels with other animals and must out compete for food

Question 2

In general what are the star-nosed moles interesting adaptations?

Answer 2

• special mechanosensory abilities to catch and eat prey in under 1/5 s
• swim well and smell underwater by blowing bubbles and breathing them back in

Question 3

How does the Eastern mole differ from the star-nosed moles?

Answer 3

• star-nosed mole has a pebbled, star-shaped nose with tentacles

Question 4

What is an eimer’s organ?

Answer 4

• domed epidermal sensory organ containing merkel cells, encapsulated corpuscles (similar but smaller than pacinians corpuscle), and circle of free nerve endings

Question 5

What animals have eimer’s organs?

Answer 5

• most species of talpids

- the ones that don’t live in dry habitats and were most likely degenerated due to harsh soil conditions

Question 6

What are the three types of sensory cell?

Answer 6

• primary sensory cells: cell bodies at surface, receive input and send it down a fiber
• secondary sensory cells: cell bodies at surface, transmit info to nerve cell
• sensory nerve cell: cell body below surface, send dendrites to the surface

Question 7

What type of sensory cell are somatosensory cells?

Answer 7

• sensory nerve cells

- cell body below surface and send dendrites up

Question 8

What characteristics does processing of somatosensory take into account?

Answer 8

• threshold and distribution

- stimulus strength (measured by firing rate)

Question 9

What sensations are merkel cells good at detecting?

Answer 9

• steady pressure and intensity
• slow adapting
• small defined receptive field
• numerous/high density
• firing increases for a smaller object
• good for determining fine spatial detail, localization and texture

Question 10

What sensations are pacinian corpuscles good at detecting?

Answer 10

• vibration and acceleration
• rapidly adapting (fire at start and end of stimulus)
• large receptive fields

Question 11

What experiments have been conducted to examine threshold and distribution of mechanosensory cells?

Answer 11

• von fray hair: poke skin with hair just until it bends
• stimulation with an electric rod
• indentation depths to measure threshold

Question 12

What experiment has been conducted to examine stimulus strength?

Answer 12

• pushed rod into hairless part of cats foot

- for stronger stimulus, more firing occured

Question 13

What is the difference between hairless and hairy skin?

Answer 13

• merkel cells are closer to the surface for hairy skin

Question 14

What are free nerve endings useful for detecting?

Answer 14

• determine texture and differentiate between a smooth pebble and segmented worm based on the deflection of cell columns and which nerve terminals are maximally stimulated
• lateral free nerve endings: nociceptors to determine if mole has entered environment with abrasives

Question 15

If a star nosed mole thinks it has encountered food, what is it sure to do?

Answer 15

• make contact with its 11th appendage

Question 16

How does the family Talpidae have similarities?

Answer 16

• all have poor eyesight but mechanosensory specializations

- gather tactile information by probing environment with tip of snout (rhinarium)

Question 17

How do the eimer’s organs for star nosed moles compare to the rest of the family?

Answer 17

• rounder, smaller and more organized

Question 18

What does the star-nosed moleunculus look like?

Answer 18

• large nose and tentacles and large front paws

- large amount of somatosensory cortex is devoted to processing this info

Question 19

For rats, what kind of mapping occurs in the cortex where sensations from the whiskers are processed?

Answer 19

• topographic arrangement of barrels/whisker fields in cortex that correspond to the spatial arrangement of the whiskers

Question 20

How are the star-nosed moles noses mapped in the cortex?

Answer 20

• tentacles of nose are mapped in a ray-like pattern that matches the location of the actual tentacles in regards to each other
• mapped three times in primary sensory, secondary sensory, and caudal-lateral cortex

Question 21

What can be determined by looking at mole fetuses?

Answer 21

• the sensitive upper and lower appendages have a head start in development
• gestation takes 30 days and the star nose develops in the third and fourth week
• in development they look similar to coast moles before the appendages peel forward and open up