Snails'R'us+I


 * __Introduction __**

Jocelyn Tandoh Vijayarani Narayanan* Carla Sena Egle Maksimovaite

The species subject of investigation is the snail Nemoralis from the genus Cepaea or more commonly known as the Grove snail. Experiments on snails rather than humans are preferred since they are easy to handle, readily available and the shell is polymorphic. We would have to travel much greater distances to sample for humans. This would make it costly and time consuming. Cepaea Nemoralis is highly polymorphic for the number of bands they have on their shell and the shell colour. The shell colour come in a variety of different colours such as brown, pink and yellow and the banding patterns vary from no bands to six bands. The results obtained can be used in the study of other species. <range type="comment" id="382900448_5">The habitat of Cepaea Nemoralis is Western Europe and it can be distinguished from its sibling species C.hortensis by the colour of their lip.</range id="382900448_5">

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">The polymorphism studied among Cepaea snails is believed to have arisen from a series of natural forces such as mutations, genetic drift, gene flow and selection. The former is responsible for introducing new alleles into a population. However, a crucial event in this process is the survival of these alleles in order to be passed on to upcoming generations. Once present in the population, they can spread out or become lost by means of selection and genetic drift; Selection will favour those individuals that carry advantageous traits for the environment they live in whereas drift <range type="comment" id="382900448_6">will act upon individuals</range id="382900448_6"> carrying traits that are not necessarily advantageous.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;"><range type="comment" id="382900448_7">Our sampling will be on the basis of utility, in order to collect a consistent sample from each habitat. It will still be representative of the population but not bias. By using a random sample we may not get a large enough sample.</range id="382900448_7">

<span style="font-family: Times New Roman,Times,serif;"> The sampling design method involves placing two vertical transects going from top to the bottom of the field to sample for altitude-climate differences. The advantage of using a vertical transect <range type="comment" id="382900448_8">is that it allows us to control a variable (altitude) a</range id="382900448_8">nd measure distribution. The transects will go through two habitats; bushes and woodland. Samples of C. Nemoralis will be taken at both habitats along the transects. The snails shell colour, whether they have a lip, number of bands and altitude will be recorded. The samples will be <range type="comment" id="382900448_9">placed 20 metres apart to make sure they are independent and to exclude the effects of gene flow.</range id="382900448_9">

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;"><range type="comment" id="382900448_10">Dispersal of the snails can be effected by predators </range id="382900448_10">such as the Song Thrush and also by seasonal and environmental changes. This could affect our samples.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">The null hypothesis for this study is Frequency of polymorphism of snails Cepaea Nemoralis <range type="comment" id="382900448_11">will not be high in certain habitats which suggest gene flow. </range id="382900448_11">There will be no selection. Variation will not be down to gene flow and genetic drift. <range type="comment" id="382900448_12">To test the hypothesis we will be using the chi squared test, using the significance of the p-value. We will need to find the same type of snail in abundance at the different habitats.</range id="382900448_12">