Land snails

Land Snails

Achatinidae | Streptaxidae | Bibliography | Links to other landsnail web pages

Achatinidae

The Achatinidae have medium to very large shells, acuminate ovate in shape and often decorated with coloured vertical streaks or flames. About 200 species of Achatinidae occur in Sub-Saharan Africa. The genera include Achatina, Metachatina, Archachatina, Lissachatina and Cochlitoma. More than 30 species are found in South Africa.

1. Achatina immaculata – Lamarck, 1822 (Syn. Achatina panthera – Ferussac, 1822)

This variable species has a large, solid shell with a colouration that depends on age. Younger shells (< 80 mm) and most specimens from the coastal plain have the typical achatinid flammate patterning of light and dark brown. However, this is lost in mature specimens of the Limpopo valley. In these specimens the flames become so closely spaced that the shell seems uniformly brown. In addition, many mature specimens have shells that have lost the periostracum due to weathering, and have become a uniform white or cream. It always has a pink columella which is truncated at the base. The shell varies from obese to slender. The only other local Achatinid with a pink or purple columella is Burtoa nilotica, found in Zimbabwe and Zambia. This species does not have a basal truncation to the columella, is very obese and has a white exterior.

The animal has a brownish foot. A darker brown longitudinal stripe runs from between the tentacles back into the shell. On either side of the stripe are two light yellow or brown bands.

The body colouration and shells of the snails below is very dark and can be paler.

Achatina immaculata is a very special and cultural important shell in Africa.

The people who lived in the Iron Age already used A. immaculata. The shell had been utilised for different purposes.

Achatina species have been utilized as food, as it still is in certain African communities.

The shells also deserved a place as tool. The women used the shells to dig clay for their clay pots. A freshwater bivalve species (Spathopsis wahlbergi) was used to burnish the clay pots.

o Beads were made from the shell.

o On the farm Greenswald in the Northern Province at the Mapungubwe archaeological site, A. immaculata, other cultural objects and animal remains have been found buried with human remains. The shells, animals and other objects were probably used as offerings, and that mean that the shells were of big importance to the people. The Mapungubwe people lived about 1100 a.d.

o Later uses that have been recorded are utilization as containers for example snuff, with the aperture (opening) sealed with moss or something similar.

The big shells also served as a cup, and when the apex was removed; even an infant could drink from it when the mother was unable to nurse the baby. With the open apex the shell is also used to administer medication to the ear.

o Even whole shells were strung, but with a complete different purpose. The rope was fitted to a tree or something similar and rattled to chase away hippos from cultivated fields.

2. Achatina smithi – Craven, 1881

A medium sized shells with seven or seven and a half whorls when adult. Shell buff with reddish-brown streaks and flames. Aperture elongate. The shell is thinner than those of A. immaculata.

3. Metachatina kraussi – Pheiffer, 1846

Adult shells have a dark-brown and thickened apertural lip that extends around the whole aperture. The apertural lip of mature specimens merges smoothly into the columella without truncation. This is unusual in the Achatinidae with trucation of the columella being the rule. However, juvenile Metachatina show the normal truncation expected for the family. Adult shells are normally creammy-white or light grey with the umbilicus closed by a callus formed by the reflexion of the columellar margin. There are seven to nine whorls with fine reticulate sculpture on all but the lower half of the body whorl. Shell size – 96 to 159 mm. The smaller shells are plump, while some tend to be very slender. A dark, thin, loosely adherent periostracum may be present. Juvenile shells differ in colour. They show reddish-brown streaks, blotches and flames on a pale buff background. The shell of the specimen below is extremely elongated and is longer than 170 mm.

4. Achatina vestita - Pfeiffer, 1855

A very distictive member of the genus because of its furry periostracum that follows the growth striae. The shell beneath the periostracum is pale buff or white, sometimes with reddish-brown flames. This species has sometimes been found several metres up on trees. Size 70-77 mm x32-35 mm.

Streptaxidae

The family consists of several genera that are active predatores or scavengers. The absence of a jaw and the radula, with its strong, sharply pointed teeth, is characteristic. The shells are small to minute, cylindrical or ovate, characterized by apertural processes variable in number; the number, shape, size and position of which are diagnostic features for each species.

1. Gulella infans - (Craven, 1880)

A common species with seven or eight whorls, first two smooth, remaining sculptured with close, regular, straight, vertical costulae. Aperture with three processes, a strong, short angular lamella, a short, blunt denticle in mid-labral position and an oblique shelf-like columella process.

The foot of the animal is yellowish-orange with the upper part bright orange. Tentacles orange.

They are carnivores and in my ‘molluscarium’ readily eat any other snails similar in size to their own. I haven’t observed them eating any snails larger that twice their size.

Bibliography

1. The Achatinid landsnails of South Africa (M.B Cortie & D. Aiken) – Special Publication no. 7 of the Conchological Society of Southern Africa.

2. The Streptaxidae of South Africa (D.W. Aiken) – Special Publication no. 6 of the Conchological Society of Southern Africa.

The above-mentioned publications can be ordered from the Conchological Society of Southern Africa. Contact the editor.

3. Mapungubwe An Archeozoological Interpretation of an Iron Age Community (Voigt, Elizabeth A. 1983) Transvaal Museum

Links to other landsnail pages

1. http://www.manandmollusc.net/ - One of my favorite sites – lots of information for adults and children.

2. http://www.kiddyhouse.com/snails - A lovely informative page for teachers and children. Contains information about snail biology, arts & craft projects for children, stories and snail care.

3. http://www.geocities.com/heartland/valley/6210/ - Annette Goodman - The Giant African Land Snail Site. Join the Cybersnail group from here.

4. http://www.landsnails.4mg.com/ - Lukes Giant African Landsnails

5. http://www.irms.freeserve.co.uk/landsnail.html - Iona & Leigh’s Homepage

6. http://members.tripod.com/snailsonline/ - General Giant African Landsnail page