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randyimmanuel randyimmanuel
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9 years ago
Hi, guys.

Here I go. These days, im observing a brown leatherleaf slug in my garden. I checked it up with google and find out so many things according to it but its respiratory system. All i can found is they "cousins" have breathing pore or we can call it pneumostome that I cant find in this slug. I've allready search for breathing system in the internet, and cant find any in any books yet. I should search for more. Hehe. Hope u guys can help me too with this one. Thanks before, guys!

Regards,

Randy
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wrote...
Staff Member
9 years ago
Basically all molluscs breathe by gills that are called ctenidia (comb-gills) because of their comb-like shape. In terrestrial molluscs this respiration organ is reduced, but still respiration takes place in the pallial cavity. That is why it is also called the snail's respiratory cavity.

Externally the mantle cavity is recognised by its large entrance opening, the respiratory opening or pneumostome. It can be seen on the right side of the mantle in the shell aperture, opening and closing periodically. When the snail is not breathing, it closes its pneumostome with a circular muscle, to avoid losing to much water by evaporation.

To inhale, the snail widens the respiratory cavity by lowering the cavity floor. Due to the resulting low pressure, air rich in oxygen flows into the cavity (see illustration on the right).

Gas exchange takes place at the cavity's roof. There the tissue is particularly thin, so oxygen (O2) diffuses into the blood fluid circulating there. In the opposite direction carbon dioxide (CO2) diffuses from the blood into the air, following the gradient of gas contained in air and blood respectively. To assist this gas exchange, the snail closes the pneumostome and raises the cavity floor, thus increasing pressure inside the pallial cavity and the rate of oxygen diffusion into the blood.

To exhale the depleted air, the snail finally opens the pneumostome and raises the cavity floor to press out the air. So the respiratory cavity floor performs the same task as does the human diaphragm in respiration.

This described respiratory organ of the Roman snail, or alike, is called its lung, in analogy to the human lung, though it resembles a single alveole, more than the whole organ of a vertebrate's lung. Because it breathes oxygen from dry air with such a snail lung, is placed systematically in the group of lung snails or pulmonate snails (Pulmonata). Those not only live on dry land, but also in fresh water. There they are optimally adapted to the sometimes changeful environmental conditions.


- Master of Science in Biology
- Bachelor of Science
randyimmanuel Author
wrote...
9 years ago
Thank you, Duddy. Very Helpfull.
Now I know that actually all molusk breathe with gills. Thats why they have gills and lung in the same time in some of it species.
I was observing apple snail before. Even if they live submerge the water, they still finding air if the water dont have adequate oxygen. But here in this slug I can't find his pneumostome. As long as i know, it only have 3 holes which its mouth, anus (that always cover by its tail), and its genital pore. From what i saw in Apple snail, its respiration hole come from up inside its shell, follow with the siphon. I'm still observing do this slug respiration hole come from up inside of its mantle or even it dont have any. I try another method to find the lungs by illuminate the slug with light. I can barely see anything but his liver, heart, radula movement, and still have no clue about how he breathe. Still observing until now, and i have try another method by submerge it in water. If he have some air in its body, maybe if I drop it to the water it will slowly go down with the "lung section" always on its top - if you know what I mean. It still cant give me any clue. So maybe it just breathe through its skin.

I have attach my slug pic. Check it out



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wrote...
Staff Member
9 years ago
I think eventually all land slugs drown after several hours of being submerged into water.

- Master of Science in Biology
- Bachelor of Science
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