THREE MAJOR EDIBLE SNAIL SPECIES OF AFRICAN ORIGIN

by

Chigbogu, Nnachetam


The two most popular edible snails in West Africa are the giant snail,
Achatina achatina, and the big black, Archachatina marginata.
Most studies on snails in West Africa have concentrated on these two species and on the garden snail, Achatina fulica. In Ghana Achatina achatina is considered the most prized species for eating, followed by Archachatina marginata and then Achatina fulica. Other edible species exist, but they are of minor, local importance.

Achatina achatina
Common name: giant snail, tiger snail (Ghana)\
Description: Achatina achatina can be considered a good candidate for snail farming in most areas of West Africa, although it requires higher humidity than the other two species and needs a longer growing time to reach sexual maturity. They are reputedly the largest land snails in the world. Although usually much smaller, they can grow up to 30 cm in body length and 25 cm in shell height. Average adult shell length is 18cm, with an average diameter of 9 cm. The conically shaped, fairly pointed shell is brownish with a characteristic stripe pattern (hence the name tiger snail).
Growing conditions: The species prefers warm conditions, 25-30 °C and a relative humidity of 80-95%. A. achatina is said not to be the easiest species to farm because of the very steady conditions it is used to in the wild: a practically constant 12/12 photoperiod, only extending to 13/11 for about 3 months, and a temperature difference between night and day of only 2-4 °C. Even in the most humid areas of West Africa the snail, in its natural habitat, buries itself for aestivation during the drier months.
Life history
Reproduction: Achatina achatina reproduces by self-fertilisation. Unlike in many other species, reproduction is not preceded by coupling, although it is not unusual to find two snails in close proximity. Studies indicate that the species breeds in the main rainy season (April-July in Ghana).
Laying: Laying usually takes place in the late evening and night. Eggs are laid in clutches of 30-300 eggs. They are broadly oval, dirty yellowish, 8-9 mm long and 6-7 mm wide. Eggs are deposited in dug-out holes about 4 cm deep. When small clutches of eggs are laid, a second laying is indicated, and sometimes a third.
Hatching: Usually, the eggs hatch 2-3 weeks after laying, with a range of 10-31 days, depending on temperature. A. achatina has a high hatching rate of 90+%; even 100% hatchability is not uncommon.
Hatchlings: The baby snail has a thin shell membrane which calcifies progressively. Although this period is characterised by rapid growth, the snails are able to survive the first few days (5-10 days) after hatching without food.
Juveniles: The juvenile phase covers the period from 1 or 2 months to the stage of sexual maturity (14-20 months). During this period, the snail accepts a much wider range of food. At the end of the period, the shell is well formed and the snail weighs between 100 and 450 g. Differences in growth rates of the various ecotypes are very evident during this period.
Adults: The adult phase starts when the snail reaches sexual maturity.
Not all adult snails lay eggs each season. An average life expectancy is 5 to 6 years, although there are reports of snails surviving up to 9 or 10 years.


Achatina fulica
Common name: garden snail, foolish snail (sometimes also called the giant African snail)
Description: Achatina fulica is a large snail, reaching 20 cm in length or occasionally more, with a shell length up to 20 cm and a maximum diameter of 12 cm. The conical, spiralled shell is predominantly brown with weak, darker banded markings across the spiral. Colouration is highly variable, depending on diet. A mature snail averages 250 g in weight.
Growing conditions: The species is highly adaptable to a wide range of environments, modifying its life cycle to suit local conditions.

Life history
Reproduction: Without delays because of aestivation or hibernation, snails will reach sexual maturity in less than a year (even as early as 5 months under laboratory conditions). Reciprocal copulation (6-8 hours) must occur to produce viable eggs.
Laying: The small (4 mm in diameter) yellowish-white eggs are laid in clutches of 10-400 eggs within 8-20 days of copulation, usually in nests excavated in the soil. Repeated laying may result from one copulation, as sperm is stored in each snail.
Egg laying frequency depends on climate, particularly on frequency and duration of the rainy seasons: up to 500 eggs per year in Sri Lanka, 300 per year in Hong Kong, and 1000 per year in Calcutta.
Hatching and hatchlings: Upon hatching, the hatchlings consume their eggshells (and unhatched siblings), remaining underground for 5-15 days and feeding on organic detritus. Eventually they feed primarily on plants at night, returning to roost before dawn.
Juveniles: Animals with shell lengths of 5-30 mm apparently cause the most damage to plants.
Adults: The snails may reach sexual maturity in less than a year. Larger snails continue to feed on plant materials, but feed increasingly on detritus as they age. Normally, they live for 3-5 years.

Archachatina marginata
Common name: big black snail, giant African land snail
Description: Archachatina marginata is a large snail, generally growing to about 20 cm and a live weight of 500g. The shell is much less pointed than the Achatina species, the roundness being especially obvious in young animals. Striation on the shell may give the appearance of a 'woven' texture. The head of the snail is dark-grey; its foot is a lighter shade. This species has been the object of a series of stocking and feeding experiments in Nigeria
Growing conditions: In the Nigerian experiments, juvenile growth was found to be inversely proportional to temperature, falling sharply at temperatures > 30 °C, and directly proportional to rainfall and humidity. Body weight gain slows down significantly during the dry season (December to March in Southern Nigeria, where the breeding trials took place).
Life history
Reproduction: The species reaches sexual maturity at an age of around one year, when the individuals reach a live weight of 100-125 g. Reciprocal copulation must occur to produce viable eggs.
Laying: The eggs are comparatively large at 17 × 12 mm, with an average weight of 4.8 g in a Nigerian stocking trial. For that reason the number of eggs per clutch is low, 4-18 eggs. Eggs are laid in the soil at a depth of about 10 cm.
Hatching and hatchlings: The incubation period, from egg to hatchling, is around 4 weeks. Hatchlings have a thin, transparent shell; they generally remain in the soil for 5 to 7 days before emerging, but sometimes wait even longer. Because of the relatively high weight of the eggs the number of hatchlings from a clutch is low compared to the other two species. During the first weeks after emerging, hatchlings repeatedly burrow into the soil.
Juveniles: In laboratory trials shell length of the juvenile snails increased by an average of 0.33 mm/day for the first 8 months (c. 8 cm), slowing down to 0.2 mm/day at 15 months. Shell length hardly increases after that time.

Adults: The snails reach sexual maturity at around 10-12 months.

Nnachet Farms: Creation of Food and Employments for Ourselves and Others

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