Picture By US National Parks Service - Wikimedia

It's been awhile since I have released my last "Animal Series" article. It has been a busy week, and I'm also have written few articles regarding photoreception and photosynthesis. If you haven't read them, you can visit my blog to check it out. Enough with this jibber jabber, now it's the time to rock on with our next animal.

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There are a few animals in the world which is weird in appearances which you wouldn't expect to see until you do. I mean you wouldn't have much chance to see a snake which shaped like a penis, frog resembles a glass, glow-in-the-dark turtles and a wolf with a fetish looking leg called the maned wolf. In this article, all of you (my dearest readers) would be introduced to an animal which has a star on its nose. Yeah, you read it right. A star! It doesn't mean it could grant your wish or anything of the sort. This creature can be found in the northernmost part of America. It's called Condylura cristata or the star-nosed mole. If we look at it closer, the start appears more like an octopus which in this case have 22 tentacles like structure attached to the mole's nose.

This animal is equipped with large sized feet and a thick tail which is an essential component that acts as a fats reserve. Its nose, which is notably the most distinct part which makes this animal undeniably standout is equipped with 22 fleshy, squishy and moving tentacles which are located at the edge of its snout. If you've read my last article about gharial/gavial crocodile, now you know that there is another animal which is much weirder in appearance equipped with a snout. If the structure which can be found on the mole's nose has a tentacle-like appendage then "star-nosed mole" would be a misnomer. It should be called a "tentacles-nose mole", but since "star-nose mole" is much better to hear, I will settle with the latter.

The Star Shaped Nose

The tentacles-equipped nose is quite imperative for a star-nosed mole, and it is a principal organ for the mole to function better, biologically speaking. It's equipped with 22 moving finger-like projection which is called tendrils that surrounds its nostrils. The overall size of the nose on an average size star-nosed mole is one centimetre which has the same diameter of an average human's fingertip. Otherwise, star-nosed mole has the largest nose among the other mole species. The most sensitive part of the nose located at the centre which gradually became insensitive as it moves towards the peripheral side. Oh wait, I didn't tell you what is the nose for, right? The nose of a star-nosed mole is equipped with thousands of small tactile receptors called the Eimer's organ.

Eimer's organs are sensory organs in which the epidermis is modified to form bulbous papillae. First isolated by Theodor Eimer from the European mole in 1871, these organs are present in many moles and are particularly prevalent in the star-nosed mole, which bears them on its unique tentacled snout.

This animal is functionally blind. "Well, I saw eyes on the creature, initially, it can see, right?" Yes, it can, but its sense of sight came from a structure which is called "touch fovea" which is located in the star organ. Their eyes are practically useless. While it wanders around the environment, searching for food sources, the fovea would be repositioned among the moving tentacles so that it will point to the area of interest; it acts like a highly organised photoreceptive system! This animal is the first mammal who smells underwater while looking for prey. While diving, it will blow into the water by using the start-shaped organs and re-inhale, sniffing for any nearby prey. It consumes worms, aquatic-based insects, molluscs, small amphibians and certain species of small fishes.

The star-shaped nose possessed by this animal has an incredible reaction speed which allows it to send a signal to the brain in 8 milliseconds. As this animal can't see with its eyes, it will use its nose to determine whether or not the nearby creature is edible or not. It's regarded as one of the fastest response to a stimulus which has been recorded in Guinness Book Of World Records. Now let's get back to the unique nose's structure.

Picture By Gordon Ramsay Submissions - Flickr

The tentacle-shaped appendages which can be found in the nose's structure are steered by a series of muscles which controlled tendons that are attached to the skull. This means the functional mechanism of those tentacles is purely mechanical. Eimer's organ which can be found in this unique nose structure is multiple projections of domes (papillae) which covered the whole epidermis of the nose. The domes which are approximately 50 μm in diameter (each) are the only organs which act as a receptor in the star-nosed mole.

There are about 25,000 receptors which are distributed among the 22 tentacle-like appendages. Fovea region, which is the part which is used for sight have the lowest concentration of Eimer's organ (900) while the less sensitive part in the most outer-region of the nose has 1500 domes. This is quite contradictory to the fact that, fovea region is an area of highest resolution which gives it the capabilities to act as a sophisticated vision system for a star-nosed mole to find a potential food source (the act of foraging). However, it's worth noting that, the amount of fibres per unit of domes is entirely different, depending on the area. The first 9 tentacles have 4 fibres innervated Eimer's organ per unit of domes while in the tenth and eleventh (the fovea region) have approximately 7 fibres per unit of domes which is denser than the first 9 tentacles.

Behaviour

Do you want to know how fast this mole can determine whether or not the "prey" that they "sniff" is edible? Ok, let's talk about the mechanism of this animal looking for a potential food source. As described above, this animal has a poorly developed eye, which is not used for vision. They locate their potential preys by using a sophisticated system of touch which will allow them to assess and understand their environment. The majority of the nerve fibres which are present in the star-nosed mole's nose is putative light touch fibres. This will allow it to make a swift contact with every single thing in the environment until it is in contact with the potential food source. After touching the potential prey, the tentacle-like structures on the nose would be shifted to allow the fovea to inspect the object of interest in great detail. The process is lightning fast. It can eat 8 preys in less than 3 seconds after which the receptor would be searching for the next target in as quick as 120 ms (average 227 ms).

The ability for this animal to smell underwater is something that is considered impossible, long time before the discovery of this fascinating animal. After blowing in the water, which would create 12 bubbles per second measuring about 0.1 mm in size, all of them would be inspired back into the nostrils to detect any odour molecules which could be recognized by olfactory receptors. It's act like an underwater hunting gun which is shot towards a target and re-breath to activate the olfactory signal thus recognising the potential prey.

Even though, the scientific community understood that the function provided by the tentacle-like structures on the star-nosed mole is purely tactile, in the past, it was presumed to detect electromagnetic field with the tentacle-like structures act like an electroreceptor. The validity of the hypothesis was tested through an experiment which utilises an artificial worm with a stimulated electrical component and the other without the electrical component. The star-nosed mole was shown to favour the worm with the electrical component which suggests that the nerve fibres in the tentacles act as electroreceptors which is used to detect a certain degree of electromagnetic fields to move around and hunt. However, this hypothesis was not accepted due to it is not being feasible than the "purely tactile" theory proposed by Kenneth Catania.

Reproduction

Picture By Hillbraith - Flickr

The reproduction process of this particular animal is not well known among biologist. This is because a star-nosed mole will spend most of its time, in an underground tunnel, dug by them which will act as a living area for them to sleep, breed and raise its successors. This animal is monogamous; it will only mate with one partner during the mating season in March and April. The gestation period will take around 45 days, and we can expect offsprings to be born around May and July. The mating process would occur continuously until the conception is successful. As long as the mating season is not ended, they will keep on shagging one another. each pregnancy will yield two to seven baby moles which are born blind, with no fur and nose folded up in a protective manner. After two weeks of life, the nose will be unfolded which will reveal the star. After a month, they will become independent. The female star-nosed mole will be able to breed after 10 months of life. They were speculated to live for four years, but this figure is just an estimate. The exact length is currently not known.

Summary

Ok, let's summarise some of the interesting features of this fascinating animal.

• They have the most sensitive touch organ - Their sense of touch can be activated with the slightest trigger which would allow them to quickly change the direction of their tentacle-like structure to find prey at a quicker pace. If this animal found what it was looking for, the tentacles would be shifted to make way for the incoming fovea region (the 11th ray) for a details inspection is a few milliseconds.
• Their sense of touch is the sense of sight - Fovea region has a higher if not the highest resolution for its to identify any potential prey object of interest. The position of the fovea region is kept on changing especially during the period of foraging.
• They can eat at a quicker rate compared to the other mammal - It will only need 8 milliseconds to identify whether the object of contact is edible or not. This signifies a quicker signal is transmitting action which will allow them to eat as much as possible prey in a matter of a minute (even second is possible).
• They can smell underwater - If you thought mammal couldn't smell in the water, this animal would change your perspective. This is crucial for a star-nosed mole to find prey underwater.

Thank you for your attention.

References and further reading materials

• Experimental Biology 2017. (2017, April 24). Totally bizarre facts about the star-nosed mole: Strange-looking creature yields surprising insights about nerves, brains and extreme adaptation. ScienceDaily. Retrieved March 12, 2018, from https://www.sciencedaily.com/releases/2017/04/170424084028.htm
• Erika Engelhaupt (2017, April 23). National Geographics. Inside the Bizarre Life of the Star-Nosed Mole, World's Fastest Eater. Retrieved March 12, 2018, from https://news.nationalgeographic.com/2017/04/star-nosed-mole-touch-pain-senses/
• Wikipedia. Star-nosed mole. Retrieved March 12, 2018, from https://en.wikipedia.org/wiki/Star-nosed_mole