3. A slug's “noses”
Morsel:
Slugs
have no noses at all: they use two of their tentacles to smell and an
air hole to breathe called the 'pneumostome'.
Meal:
While journeying through the plains of the Internet, one may find the
statement that “slugs have four noses”. They do not have a “nose”
like a mammal; instead they have four tentacles, the lower of which
are used as sensory organs. The upper two larger tentacles are topped
with eyeballs.
They cannot breathe through these tentacles. For that, they have a
small opening on their mantle called the 'pneumostome' (Greek
'pneumo' lung/air + Greek 'stome' mouth), which intakes air into the
slug's single lung. The pneumostome opens and closes in a rhythm that
is equal to 0.5 closures when the slug is fully hydrated. This rate
increases the further the slug becomes dehydrated. Snails also have
this feature but it can be difficult to see due to their shell. In
the image below, you can see a large red slug with its pneumostome
wide open.
By © Hans Hillewaert, CC BY-SA 4.0, Link
Some species of gastropods are considered agriculture pests, but they
also have their uses to humans. Their bodies are eaten as starters,
called 'escargot' (French for 'snail'), in France, Spain, and
Portugal, and their eggs are used as gourmet caviar.
Their mucus also has various applications. Slugs and snails produce
mucus in order to move and adhere to surfaces. This mucus makes the
gastropod difficult to hold and is distasteful, traits which are
useful against predators. Some people use it as a beauty product to
delay aging and heal acne and scars. Their slime, and the gastropods
themselves, have been employed to ameliorate other ailments: for
stomach ulcers, skin lesions, ulcers, and asthma, to name a few. The
secretion of one particular slug, the Dusky Arion, also helped
inspire the creation of a glue for internal wounds.
One other appetising detail about something called 'apophallation'.
Slugs are hermaphrodites, meaning they have both male and female
organs. When two slugs coopulate, they usually mate pleasantly and
are then on their way. However, in some species of slugs, the penis
may become trapped (for reasons unclear) and the partners will have
to gnaw off the penis (or, on occasion, both of their penises) to
untangle their entwinement. The eunuch can still mate but it is now
limited to doing so as a female.
Recipe:
Dickinson,
PS, DJ Prior, and C. Avery. 1988. “The Pneumostome Rhythm in Slugs: A Response to Dehydration Controlled by Hemolymph Osmolality and Peptide Hormones.” Comp
Biochem Physiol A Comp Physiol
89(4):579–85.
ScienceDaily.
2017. “Wyss Institute for Biologically Inspired Engineering at Harvard. ‘Sticky When Wet: Strong Adhesive for Wound Healing: Slug-Inspired, Flexible Medical Bio-Glue Sticks to Wet Surfaces without Toxicity.’” ScienceDaily.
Retrieved August 20, 2017.
Denny,
MW. 1989. “Invertebrate Mucous Secretions: Functional Alternatives to Vertebrate Paradigms.” Symposia
of the Society for Experimental Biology
43:337–66.
Thomas,
Steve. 2013. “Medicinal Use of Terrestrial Molluscs (Slugs andSnails) with Particular Reference to Their Role in the Treatment ofWounds and Other Skin Lesions.” World
Wide Wounds. Retrieved
August 20, 2017.
Vogt,
Andrea. 2017. “Italy’s Snail Farmers Having the Slime of TheirLives as Niche Beauty Product Craze Sees Rise in Demand.” The
Telegraph, February 5.
Miller,
Brooke L. W. 2007. Sexual Conflict and Partner Manipulation in the Banana Slug, Ariolimax Dolichophallus. Santa
Cruz: University of California.
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