07 January 2009

The mantle cavity of Rumina saharica

In gastropods, the mantle cavity houses some of the vital organs, including the heart, the kidney and the gills. In pulmonates, the lungs replace the gills and the arrangements and the morphologies of the organs of the mantle cavity gain significance in the understanding of the evolutionary relationships between the different groups. Below is the mantle removed from a specimen of the land snail Rumina saharica.

The mantle cavity of Rumina saharica flipped over and turned inside out; the organs along the left-hand side in this photograph would be along the right-hand side of a live snail. Abbreviations: P, the outside opening of the pneumostome (breathing hole); MC, mantle collar (the front edge of the mantle that is fused to the top of the head in a live snail); K, kidney, V, ventricle; A, auricle (the ventricle and the auricle together make up the heart); R, rectum (its opening is within the pneumostome); L, lung. The blue dots mark the ureter, while the red dots the principle pulmonary vein.

Compare this with the mantle cavity of Rumina decollata below.

The mantle cavity of Rumina decollata from Pilsbry (Fig. 81 in LMNA, II:1, 1946). The kidney and the ureter are in blue, while the heart and the principle pulmonary vein are in green.

Note how in both species the ureter, instead of running directly towards the mantle collar, first goes down, turns around and then goes up towards the pneumostome, near which it drains to the outside. The snails with this peculiar anatomy belong to the group Sigmurethra.

I am primarily interested in the venation of the lungs of pulmonate land snails. Below is a closer shot of the lung of Rumina saharica showing some of the secondary veins covering the roof the mantle cavity.

The colorized drawing of the mantle cavity of

There will be more posts on this subject in the future. Incidentally, this was the 1st dissection I did this year.

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