Star-Nose Mole and Desman

They are weird, but cute is something different

In this blog I want to introduce two rather extraordinary species of mammals, of which I had the luck to observe at least one: the Pyrenean desman (Galemys pyrenaicus). In 1981 when I was working in the CNRS Laboratoire souterrain de Moulis in France, I inquired what that long aquarium which I saw in one of the rooms was used for. And I was told of the research on the rare aquatic mole-relative, known as the desman, by a former priest, who had earlier been on a mission in India, fallen in love with a nun, left the priesthood, married her and had returned to France, where he was now carrying out observations on the biology of the enigmatic “desman des Pyrénées”. I met Monsieur Richard, was invited to his home to meet his wife and assisted him in his work on the desman on one evening.

What a strange animal, was my initial thought, when I saw this hyperactive mammal of less than fist-size for the first time! It was bobbing up and down on the water surface like a cork, stuffing a little worm it was holding in its short front paws into its tiny mouth, only to frantically diving about 30 cm to the gravelled bottom of the aquarium again to stick its long and incredibly mobile and prehensile nose between stones and pebbles to detect prey, e.g. insect larvae or small worms that it could then grab and take to the surface to eat or to climb (with the aid of some sharp claws) onto a small stone platform to rest or to scratch and dry its wet fur. I stopped the time the peculiar animal stayed under water and marvelled at (for its body size) huge webbed hind feet. The animal had small eyes, but exceedingly long whiskers (called vibrissae) around its nose and a very long and thin, scale-covered tail, reminiscent of that of a rat (to which the desman is not at all related as the rat is a rodent and the desman belongs to the moles and thus insectivores). It seemed to have a buoyancy problem and easily floated to the surface, which made its dives seem very laborious, requiring a lot of energy; something that must also have been a problem with the very cold mountain streams it preferred as its habitat. Already not exactly common 40 years ago, it has apparently become much rarer still today.

If this aquatic mole-relative wasn’t weird enough, then lets look at another species of mole, one I’ve never seen and know only from reading about its incredible sensory adaptations: the star-nosed mole (Condylura cristata), sometimes also referred to as ‘star-muzzled mole’. This species, like the more common Talpa europaea is virtually blind and spends all its life undergroud in an environment of moist soil in the northeastern region of North America. What makes this species so unique are the grotesque 22 fleshy appendages around the nose, which contain sense organs that respond to the minutest vibrations and serve as what has been termed a “tactile eye”.  In spite of its location on the nose, the appendages do not contain olfactory receptors and do not function like tentacles to grab prey, for there are no muscle fibres in them. Arranged in two groups of 11 on either side, the fleshy appendages, each with its own directional sensitivity, represent specialized mechanoreceptors that contain superfast conducting myelinated axons. Neuronal responses to the faintest stimulation occur with a latency of an average of 11.6 milliseconds. To decide if something is edible requires 25 msec for this mole, but in humans, by comparison, the process has been reported to take 600 msec.

According to Vanderbilt University’s Drs. K. Catania and J.H. Kaas, a little more than half of the brain of the star-nosed mole is dedicated to analyse signals that arrive from the star-like appendages. Each hemisphere of the cerebral cortex possesses clearly visible 11 stripes representing the 11 appendages of the nose-star’s opposite (contralateral) side. Now do these strange two mole species that this blog has been about have something in common? Yes, they do, for the star-nosed mole also loves water and swims well and, as Kenneth Catania in the year 2000 has written  “Mechanosensory organs of moles, shrew-moles, and desmans: a survey of the family Talpidae with comments on the function and evolution of Eimer’s organ”, they also share the organ responsible for the amazing tactile sensitivity: named after Swiss born Theodor Eimer, who first described the organ in 1871.

© Dr V.B. Meyer-Rochow and, 2021. Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and with appropriate and specific direction to the original content.

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