Biology of Snails
Snails belong to a group of invertebrate animals known as molluscs. Most molluscs carry a shell. Other members of this group include slugs, mussels, squid and cuttlefish.
This Agrodok concentrates on the farming potential of the giant African land snails (GALS), more specifically the species Achatina achatina, Achatina fulica and Archachatina marginata. These belong to the family Achatinidae, a diverse group of large pulmonate land snails, originally from western, eastern, and southern Africa, with long slen-der shells. Their size ranges from 3 cm to 25 cm.
The 14 genera are:
Achatina, Archachatina, Atopochochlis, Bequeartina, Burtoa, Columna, Callistpepla, Lignus, Limicollaria, Limicolariopsis, Lissachatina, Metachatina, Periderriopsis and Pseudachati. They mostly live in jungles in tropical countries, but some may live in grassland. They primarily feed on fruits and leaves.
They are easy to find and not difficult to rear. They lay several batches of eggs each year. Generally, they are quite easy to care for, being able to put up with a range of conditions.
Essentially, a snail consists of two parts, the body and the shell. The body is divided into three parts – the head, the foot and the visceral mass. The head is not well demarcated and carries two pairs of retract-able tentacles.
One pair of tentacles is far longer than the other and contains the eyes in the knobbed end. The long, muscular foot occupies almost the entire ventral surface and, like the head, is not clearly demarcated from the rest of the body.
A shallow longitudinal groove runs along the center of the foot. The hump-shaped visceral mass is housed in the shell above the foot. It contains the digestive, reproductive, and respiratory organs.
The skin over the visceral hump secretes a large calcareous shell (98% of the shell is made up of calcium carbonate). In most species the shell accounts for about a third of the body weight. It is the snail’s protective casing. Whenever danger threatens, the snail withdraws its body into the shell.
As at today there are about 11 breeds of snails which are being cultures for the purpose of meat, reproduction, sells etc. but for the sake of our today’s topic, we will be discussing about the three (3) major and popular breeds of snails below:
(1) Archachatina Marginata (African Giant Snail)
Description of Archachatina Marginata (African Giant Snail)
Common Names: Giant African snail, Banana rasp snail, West African snail.
Native Range: West Africa
The giant West African snail or banana rasp snail is a species of air-breathing tropical land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinidae. They can grow up to 20 cm long, and live up to 10 years.
Archachatina marginata is the largest of the Archachatina snails and is found in West Africa. It appears to be a mainly terrestrial snail. In Cameroon it can be found aestivating under ground during the drier months, having a closed aperture, sealed with a solid, calcareous, white epiphragm.
It is to be noted that when a crawling snail is disturbed it produces a peculiar screaming noise, caused by the expulsion of air as the shell is rapidly retracting by the powerful columella muscle.
Natively, this species does not cause any appreciable damage to native crops and is actually considered an economic asset among many native peoples who include it in their diet.
This species has the potential to get up to 210 mm in length and 130 mm in diameter, with 6-7 whorls. The shell has a brownish yellow background with fairly uniformly arranged bands and zigzag lines or spots that are dark-brown or reddish brown in color.
The columella, outer lip and inside the aperture (mouth) are white or pale blue. The apex of the shell is slightly flattened, bulbous and pale or pinkish in color. The body color of the animal is variable (albino or tan to ash grey).
An albino-bodied form can be found and is actually becoming more common. This is because natives prefer to eat the dark-skinned ones, based on the belief that they are tastier and that there is something undesirable or freakish about the white-skinned ones.
It must be noted that in captivity, it is known that captive snails tend to be lighter than their wild counterparts and this is not the same thing.
The shells of Archachatina marginata are used for domestic purposes by locals for salt holders and cups etc.
Synonyms According to Research
- Buccinum parvum integrum (Gualtieri, 1742) [Described as synonym by Bequaert and Clench, 1936. Since shown to be Achatina achatina (Linné)]
- Achatina marginata (Swainson, 1821)
- Helix (Cochlitoma) amphora (Férussac, 1821)
- Cochlitoma marginata (G. B. Sowerby, 1825)
- Helix (Cochlitoma) marginata (Rang, 1831)
- Achatina (Achatina) marginata (Beck, 1837)
- Achatina amphora (Catlow and Reeve, 1845)
- Oncaea marginata (Gistel, 1848)
- Achatina (Archachatina) marginata (Albers, 1850)
- Achatina (Achatinus) marginata (Pfeiffer, 1856)
- Achatina paivana (Vignon, 1888)
- Archachatina marginata (Pilsbry, 1904)
- Archachatina marginata var. amphora (Pilsbry, 1904)
- Achatina schweinfurthi var. foureaui (Germain, 1905)
- Achatina (Archachatina) marginata var. foureaui (Germain, 1908)
- Achatina intuslalescens “Paiva” (Nobre, 1909)
- Archachatina (Megachatina) marginata var. foureaui (“Germain” Dautzenberg, 1921)
- Archachatina (Megachatinops) gaboonensis var. aequatorialis (Bequaert and Clench, 1936)
- Archachatina (Megachatina) marginata (Bequaert and Clench, 1936)
- Archachatina aequatorialis (Dartevelle, 1939)
- Archachatina (Calachatina) marginata (C. R. Boettger,
(2) Achatina Achatina (African Origin)
Description of Achatina Achatina
Common Names: Giant African snail, Giant Ghana snail, Giant tiger land snail, Escargot geant, Achatine.
Native Range: Northern section of West Africa
Achatina achatina, commonly known as the Giant Ghana African snail, also known as the Giant African snail, giant tiger land snail, and gigantocochlea, is a species of large, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinidae.
Similar to the other species in the genus, Achatina achatina’s shell can attain a length of 200 mm and a maximum diameter of 100 mm. They may possess between 7-8 whorls and the shell is often broadly ovate. The body of the animal is silver-brown in color although albino morphs may exist.
Read Also: Ways to make more Money as a Snail Farmer
(3) Achatina Fulica
Description of Achatina Fulica
Achatina fulica is a species of large land snail that belongs in the family Achatinidae. It is also known as the Giant African land snail. It shares the common name “giant African snail” with other species of snails such as Achatina achatina and Archachatina marginata.
The Giant African Land Snail is one of the largest terrestrial gastropods. They have a light to dark brown shells with vertical stripes of a darker shade of brown on them.
They have an average lifespan of about 5-7 years. When they have enough food, and the weather is satisfactory, they tend to live much longer. Some of them have been known to live up to 10 years.
The “Achatina fulica” is one of the most invasive species in the world and the United States Department of Agriculture consider it as one of the most damaging species for the agriculture and crops in the country. It is known to eat at least 500 different species of plants.
This species is on the list of the 100 most harmful invasive alien species in the world, but Achatina fulica does not seem to surrender. This snail that stands out for its large size has easily adapted to life in regions outside its natural habitat and is considered one of the biggest land snails.
Achatina fulica originated in the coastal areas and islands of East Africa, where it presumably got the nickname, “Giant African Snail.” The snail inhabits countries ranging from Mozambique in the south, to Kenya and Somalia in the north.
The Giant African Snail eats leaves, flowers, fruits, stems, barks, wood, seeds, grains, nuts, seaweed and even lichens, fungi and other snails. Economically valuable crops for humans such as cauliflower, cocoa, papaya, peanut, cassava, banana and many other vegetables often become food for the giant African snail.
Other Breeds of Snails include:
• Helix.aspersa (Spain , France ,Italy)
• H .pomatia (Rome , France , Britain)
• H .lacteal (Spain)
• H .nemoralis (Spain)
• H . hortensis (Central and northern Europe)
• H . aperta.
• lucorum (Crimea to turkey)
• adanensis (turkey)