Milk snails (Otala Schumacher 1817)

 
   
 
   

Milk snail (Otala lactea). From top to bottom: Apertural view,
apical view (view on the shell tip), columellar tooth (means of
distinction from Otala punctata). [RN]
 
 
Spanish snail (Otala punctata). Source: Wikipedia.

Milk snails (Genus Otala Schumacher 1817) as relatives of Roman snails and banded snails are placed in the Helicidae family. We know two species from the Western Mediterranean, both resembling each other very much, which makes identification rather hard.  In comparison to the globular shells of banded snails (Cepaea) and Roman snails (Helix), Otala shells look rather depressed and non-globular. As in a banded snail's shell, the navel (umbilicus) of an Otala shell is invisible, because it is covered by the rim of the apertural lip.

In adult specimens, the aperture is extended to form a distinct apertural lip, that may be strongly coloured. The shell itself shows a very diverse pattern of dots and stripes, but is usually described as very variable.

Milk snails are herbivores that, in their native habitats, are only active at night and spend the hot time of the day in aestivation. During this time they close their shell aperture with a membrane from dried mucus, the so-called diaphragm and they also reduce their breathing rate to a fraction of the active value.

Otala lactea (O.F. Müller, 1774)

Otala lactea (O.F. Müller, 1774) usually referred to as milk snail, can be recognized by its strongly extended apertural rim resembling a spatula. Inside and at the lip the milk snail's aperture is strongly coloured, dark chocolate brown until almost black, the colour border sharply to be seen. The columellar part of the rim is broadened and appears to show a columellar tooth. This columellar tooth separates Otala lactea from its relative, Otala punctata.

Dimensions: see following species.

 
   
 
Spanish snail (Otala punctata). Above: Apical view; below:
Apertural view. A columellar tooth, as in Otala lactea is mis-
sing! [RN]

Habitat and Distribution: In nature, the milk snail lives in rocky, bushy heath lands and steppes, from Southern Spain and Southern Portugal over the Balearic Islands, until Morocco.

Spanish Snail, Otala punctata (O.F. Müller, 1774)

The Spanish snail (for lack of a better vernacular name), Otala punctata (O. F. Müller, 1774), is very similar to the formerly described species. Often it can only be discerned from it by the missing columellar tooth, as the shell pattern is so variable in both species. In contrary to Otala lactea, Otala punctata's shell mouth usually is less strongly coloured (more like light brown and chocolate colour) and the colour borders are not as sharp.

Dimensions: W: 33 - 39 mm; H: 20 - 24 mm. (Abbreviations).

Habitat and Distribution: The Spanish snail is often found in agricultural areas in the coastal plains. That explains, why it is also often found in the remainder of Europe, where it is sent with food transports from the Western Mediterranean. The species' distribution area extends further to the West than that of the formerly described species: In Northern Africa, Otala punctata occurs as far west as Northwest Algeria, it also does on the Balearic Islands. On the North Western coast of the Mediterranean, the species occurs in Eastern Spain, as far South as the Costa Blanca, in the North until the French Roussillon.

Economical Value to Man

There is archaeological evidence from Morocco, that in Roman times Otala snails were consumed as food. Even today they are consumed in their original distribution area in Southern Spain and France, but also in Italian kitchen. By food transports from the Western Mediterranean, Otala snails not only sometimes appear in Central Europe, but also have been introduced as far away as America and Australia, as have banded snails (Cepaea) and brown garden snails (Cornu aspersum).

Literature:

Further Information: