Post by apple on Dec 28, 2005 19:16:34 GMT
The colours of snails and their shells
In Achatinidae, as in other gastropods, the colour and pattern of the shell provides
information of taxonomic value. The body colour of the snail, occasionally referred to, has a
lesser significance. Yet, in both out African and home-bred snails colour change occurs in the
shell and the body.
(i) Colour changes in the shell. With cultured animals there is a trend to a darker shell,
particularly noticeable in A. a. monochromatica (which is 'fulvous yellow' during growth and
becomes chestnut-brown with age: this change was also noted for some African shells by
Bequaert, 1950). Similarly, the shell of A. panthera also darkens to a chestnut-brown. With
African Achatina achatina and Archachatina there is frequently a more abrupt change. The
normal colour pattern ceases on their arrival in this country, further growth of the shell
showing uniform pale yellow coloration. This does not appear to be due to temperature
changes during their transport, since home-bred animals have suffered such changes without
effect. Nor does it appear to be caused by diet as such: home-grown animals show normal
shell colours. What may be significant is the change of diet and possibly soil flora suffered by
imported animals.
(ii) Colour changes in the body. There is a general trend towards a paler body colour in our
cultured snails, except in A. panthera which has a naturally pale body. These changes appear
to be environmental in origin since they are not noticeable in imported animals.
In Archachatina, however, there has arisen a sudden change to a uniformly pale body
coloration that appears to genetic in origin. This apparent mutation is reported in Dr
Plummer's paper. Even in these animals, however, the pale cream body becomes tinged with
brown as they age.
« The life of Achatinidae in London»- by R. H. Nisbet
In Achatinidae, as in other gastropods, the colour and pattern of the shell provides
information of taxonomic value. The body colour of the snail, occasionally referred to, has a
lesser significance. Yet, in both out African and home-bred snails colour change occurs in the
shell and the body.
(i) Colour changes in the shell. With cultured animals there is a trend to a darker shell,
particularly noticeable in A. a. monochromatica (which is 'fulvous yellow' during growth and
becomes chestnut-brown with age: this change was also noted for some African shells by
Bequaert, 1950). Similarly, the shell of A. panthera also darkens to a chestnut-brown. With
African Achatina achatina and Archachatina there is frequently a more abrupt change. The
normal colour pattern ceases on their arrival in this country, further growth of the shell
showing uniform pale yellow coloration. This does not appear to be due to temperature
changes during their transport, since home-bred animals have suffered such changes without
effect. Nor does it appear to be caused by diet as such: home-grown animals show normal
shell colours. What may be significant is the change of diet and possibly soil flora suffered by
imported animals.
(ii) Colour changes in the body. There is a general trend towards a paler body colour in our
cultured snails, except in A. panthera which has a naturally pale body. These changes appear
to be environmental in origin since they are not noticeable in imported animals.
In Archachatina, however, there has arisen a sudden change to a uniformly pale body
coloration that appears to genetic in origin. This apparent mutation is reported in Dr
Plummer's paper. Even in these animals, however, the pale cream body becomes tinged with
brown as they age.
« The life of Achatinidae in London»- by R. H. Nisbet