LAND SNAIL (Archachatina marginata) - The Federal University of ...

ESTIMATION OF SURFACE AREA OF THE GIANT AFRICAN
LAND SNAIL (Archachatina marginata) AND RELATIONSHIP
TO
INTERNAL SHELL VOLUME
BY
BANJOKO, OLUWASEUN AYOWALE
(MATRIC NO: 03/0527)
A PROJECT REPORT SUBMITTED TO THE
COLLEGE OF ANIMAL SCIENCE AND LIVESTOCK PRODUCTION
UNIVERSnv OF AGRICULTURE, ABEOKUTA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE AWARD OF
BACHELOR OF AGRICULTURE
(B. AGRIC)
OF THE UNIVERSITY OF AGRICULTURE,
ABEOKUTA, NIGERIA
MARCH, 2010

I express my unreserved appreciation to my Supervisor, Professor O.A. Osinowo, for his
understanding, guidance, suggestions, encouragement and constructive criticisms throughout
the course of this prQject. I acknowledge the immense contributions, invaluable assistance
and constructive criticisms of Dr. T.J. Williams, Dr. I.J. James, Dr. O.F. Smith and the Snail
ResearchUnit Manager, Brother Ibrahim.
I am also grateful to Mr. and Mrs. Bamidele, my brothers Ayorinde, Olusegun, Bolarinwa,
and Opeyemi for their constant encouragement. Finally, to my ever loyal friends, Lizzy
Olusanya, Yewande Okunlola, Hansome Macaulay, Tolu Laniran, Ejiro Layeni, Deji Abatan,
Femi Akilapa and Debola Adefemi, I am deeply appreciative.

Twenty shells and eighty-two Archachatina marginata weighing between 88 and 485 g were
sourced from Delta State, Edo State, Enugu State, Imo State and Abeokuta in Ogun State.
The snails were measured for their shell parameters such as length, width, width of whorls,
weight, surface area and internal shell volume to ascertain the degree of relationships
between the said shell parameters. The weight of the snail was determined directly on a
sensitive scale, shell height measured along its axis and shell width measured across it were
also measured directly using a vernier caliper. The shell volume was obtained by filling the
shellto the brim with water and subsequently measuring the water in a calibrated cylinder.
The shell surface area was obtained using the grid svstem involvinl! Dlasterinl! of l!TaDhof
known area on the shell surface. The data obtained from the measurement of the
;Archachatina marginata
shells were subjected to Pearson correlation matrix to determine the
degree of association between the shell parameters. It was discovered that length and width
were highly correlated (P

Title page
Certification
Dedication
Acknowledeement
Abstract
Table of contents
List of tables
List of fieures
CHAPTERONE
1.0 INTRODUCTION
1.1 Broad objective
1.2 Specific objectives
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 Anatomy of snail
2.2 Morphology of snail shell
2.3 Description of Archachatina marginata
2.4 Relationship between surface area and internal shell volume
2.5 Importance of snail surface area to volume ratio
2.6 Composition of snail shell
2.7 Development of a shell
2.8 Shell colour formation
2.9 Importance of snail shell

COlluueroial uses for snail shells
Feed
Feeding methods
Sanitation and hygiene
MATERIALS AND METHODS
Experimental area
Experimental animals and management
Experimental materials
Methodoloav
Data collection
Statistical analysis
4.0 RESULTS AND DISCUSSION 15
4.1 Correlation matrix of shell parameters 15
4.1.1 Relationship between shell length and shell surface area 16
4.1.2 Relationship between shell width and shell surface area 17
4.1.3 Relationship between shell length and shell internal volume 18
4.1.4 Relationship between shell width and shell internal volume 19
4.1.5 Relationship between shell surface area and shell internal volume 20
4.2 Regression of shell length, shell width and whorl width on ~hell surface area 21
4.3 Regression of shell length, shell width and whorl width on internal shell volume 23
4.4 Validation of predictive equation using independent data 24

CHAPTER FIVE
5.0 CONCLUSIONS AND RECOMMENDATIONS
APPENDIX
A: Shell parameters of dead Archachatina marginata
8: Shell parameters of live Archachatina marginata

Correlation matrix of shell volume and surface area with linear
values of shell parameters of Archachatina marginata
Regression equations of surface area with linear values of shell
Parameters
Regression equations of shell volume with linear values of
shell parameters
Summary of analysis of variance between the actual width and
the predicted width

Figure 1 Relationship between shell length and surface area 16
Figure 2 Relationship between shell width and surface area 17
Figure 3 Relationship between shell length internal shell volume 18
Figure 4 Relationship between width and internal shell volume 19
Figure 5 Relationship between shell surface area and internal shell volume 20
Figure 6 Comparison of actual and predicted shell width 25

CHAP'fERONE
INTRODUCTION
The snail coupled with other small livestock species such as grasscutter, giant rat constitute
"micro-livestock", a new but rapidly expanding area of animal production and research. The
snail gained increased attention in recent years as a result of augmenting family income. The
snail forms a common component of food in the diet of people, rich in protein (88.37%) thus
compares well with conventional animal protein sources; beef (92.75%), broiler (92.21%),
chevon (86.63%), mutton (86.34%), pork (82.42%) and fishes (91.99% and 90.81%)
(Imevbore and Akinnusi, 1988). The snail also possess curative properties (Cobbinah, 1990
and Akinnusi, 1998), an area which require further investigation so as to gain wide scale
application.
Snails are bilaterally symmetrical invertebrates with soft unsegmented body enclosed by an
exoskeleton in the form of calcareous shell. They belong to the phylum Mollusca, of class
Gastroooda. subclass Pulmonata. order StvlommatoDhora and familv Achatinidae. which is
the Giant African Land Snail. Snail meat feature in the diets of urban and rural dwellers in the
southern part of Nigeria, usually served as delicacies, and occasionally for health
consideration. Akinnusi (1996) stated the main source of supply to the numerous consumers
is from people who gather wild snails from nearby bushes and sell along the roadsides and in
the local markets. Hodasi (1979), Akinnusi (1998) and Orisawayi (1989) put the age at sexual
maturity at six (6) months when they are reared from day-old but in the wild it is between
nine (9) to ten (10) months.
A snail's body is characterized by a division into a soft body and a hard shell. The shell is
secreted by a part of the molluscan body known as the mantle. The snail shell is an external

skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection
from predators and from mechanical damage. In land snails, the shell is an essential
protection against the sun, and against drying out.
In land snails, shells often provide relevant morphometric
data used in taxonomy and
phylogenetic inference as well as in population biology. Shell morphology (which preserves
the ontogenic record of growth) is the principal su~ject of theoretical morphology. This has
led to studies on the formal and historical determinants of shell forms, as well as functional
interpretations of their observed distributions (Raup, 1966; Stone, 1996, 1999; McGhee Jr.,
1999; Samadi et al., 2000). Body size can be estimated as shell volume which is a more
reliable measurement of land snail size than liveweight because this depends on the state of
hydration and is consequently highly variable in land snails (Baur and Baur, 1998).
The most frequently used measurements of the snail shell are: the height of the shell, width of
the shell, height of the aperture, and width of the aperture. The number of whorls is also often
used. Relative aperture area tends to be smaller under drier conditions, probably because of
selection for smaller whorl cross-sectional area to reduce water loss. Larger snails tend to
have higher whorl expansion rates (Goodfriend, 1984). The largest height (also known as
length) of any shell is found in marine snail species (Wells et al., 2003).
There is at present a lack of information in the literature on estimation of surface area of the
giant African land snail and relationship to internal shell volume.
1.1 Broadobjective
• To determine the relationship between surface area and internal shell volume of the
Giant African Land Snail (Archachatina marginata).

1.1 SpecificObjectives
• To detennine the relationship between length and surface area of A. marginata..
• To detennine the relationship between width and surface area of A. marginata.
• To detennine the relationship between length and internal shell volume of A.
marginata.
• To detennine the relationship between width and internal shell volume of A.
marginata.
• To detennine the relationship between width of each whorl, shell surface area and
internal shell volume of A. marginata.

CHAPTER TWO
LITERATURE
REVIEW
%.1 Anatomy of the snail
Snails are soft-bodied animals consisting of two parts. the body and the shell.
The body is divided into three parts. The head, the foot and the visceral mass which are all
encapsulated by the shell. the wall of the shell is lined by the fleshy mantle. The head is in the
front part of the body. and it is easily noticeable. It is consisted of the mouth and four
tentacles of which the upper pair is longer. The head bears two tentacles that can be retracted.
The upper pair is longer than the lower pair (Roberts, 2000). Each pair of the tentacles has a
tiny eye at the tip. The eye is used to distinguish light and darkness. The two shorter tentacles
are knobbed at the tips and are the organs of smell and touch. The mouth is located at the
centre of the head. The mouth opens directly into the a muscular cavity lined with a horny
jaw and a radula flexible file-like rasping organ with numerous row of muscular teeth for
shredding food (Akinnusi. 1998). The foot, protruding from the shell. allows movement and
sticking of the snail to the ground. The bottom part of the foot contains many glands that
secrete slime thus creating visible silvery trace. Thanks to that the snail can slide over a
rnzor's edge without hurting itself. Its movements are slow but strong. The lower part of the
foot is made of strong muscles. The visceral mass, which is the softest part, is confined within
the upper whorls of the shell. It is humped shaped and generally holds the bulk of the
digestive. reproductive. excretory and respiratory system. The skink of the visceral hump
secretes a large calcareous shell.
The typical snail has a calcareous shell coiled in a spiral pattern around has a central axis or
columella. The shell in secreted by the fleshy living of the wall of the shell known as the
mantle. The secretion of the shell in by outward additions to the shell hip and then by
secretion of inner thickening layers. The outer layer of the shell in a mixture of proteins

known as conchin. Inner layers of the shell is made up of calcium carbonate join with a
network of conchin and are impregnably with variety of mineral salt Cobbinah (1990)
submitted that 98% of the shell is in the form of calcium carbonate.
Snail shells are important for use in systematic, that is deciding who is more closely to whom.
The conical, planospiral and spire are the three shell shaPes, all of which have different
structural strengths. Most snails have a roughly conical or oval shell protecting their bodies.
These shells are twisted into spiral levels known as whorls. The whorls are largest at the base
and each one gets progressively smaller as we approach the tip, known as the apex. Notice
that there is a large opening in the newest whorl of the snail. This is called an aperture. The
inside edge is called the inner lip and the outside edge is the outer lip. These aperture lips are
where new shell material is added. Also, the newest whorl containing the aperture is called
the body whorl. The whorl is a complete turn of the shell. All the older whorls above this one
are collectively called the spire.
The whorls form as shell material is laid down by the mantle, which is a sheet-like organ that
lies against the inside of the largest bottom whorl. The rod shaped structure that runs down
the centre of the shell is called columella. One additional feature of some snail shells is that
tubular structure at the very end. This is called the aperture canal and is used to house and
protect the animal's siphon, which is like a nose that is used to search for food. Obviously the
primary use of the shell is to protect the soft body inside. But since the animal must be able to
extend part of its body from the shell in order to move around and eat, the aperture represents
a pretty large chink in the snail's armor. To protect this opening there is a structure attached
to the foot called an operculum. This trap-door structure seals the opening shut when the foot
is retracted back into the shell. This not only prevents predators' access, but for intertidal
5

species it protects them from drying out during low tide. The moon snail (top) has a hole in
the boUom. This is called an umbilicus and is where the mantle inserts calcium to form the
central columella. The suture is an indentation seperating the whorls.
2~ D~riptionorA.nmrgbmm
According to Ogunlakin (1999) quoting Hodasi (1984) and Imevbore (1990), the A.
marginata have a wide, bulbous or dome shaped apex of shell. They produce few and
relatively large eggs. They have short and tubular vagina. The spermatheca duct is very long
and slender. The pedal sole is relatively narrow and the shell colouration is irregular and has
no definite pattern. Adult shell height is usually 140-170 mm. Shell pattern and colour varies,
but is usually dark brown with varying amounts of lighter brown and yellow stripes. Flesh
colour varies from light brown to almost black. There are many white and pale-fleshed
specimens in captivity too. The flesh feels quite coarse to the touch. They make very good
pets, but do prefer damper conditions. The species is native to central western Africa (around
Cameroon).
2.4 Relationship between surface area and internal shell volume
Surface area is the area of a given surface. Roughly speaking, it is the "amount"
of surface
i.e, it is proportional to the amount of sheets needed to cover it (Fjelstad and Ginsher, 2003).
The volume of A. marginata measures the space that it's body mass occupies.
The' snail shell surface area and volume do not necessarily increase or decrease proportionally
to increases or decreases in length, width, and weight. For example, the greater the diameter
of a single-celled organism, the less surface area it has relative to its volume. The snail
surface area to volume ratio is a way of expressing the relationship between these parameters
as the snail size changes.

Organisms exhibit a variety of modifications, both physiological and anatomical, to
compensate for changes in the surface area to volume ratio associated with size differences.
One example of this is the higher metabolic rates found in smaller (homeothermic) animals.
Because of their large surface area relative to volume, small animals lose heat at much higher
rates than large animals, and therefore must produce more heat to offset the effects of thermal
conductance. Another example is the variety of internal transport systems that have developed
in plants and animals for actively moving materials throughout the organism, thus enabling
them to circumvent the limits imposed by passive diffusion. Many organisms have developed
structures that actually increase their surface area: the leaves on trees, the microvilli on the
lining of the small intestine, root hairs and capillaries (Vogel, 1988).
2.5 Importance of snail surface area to volume ratio
Changes in the snail's surface area to volume ratio have important implications for limits or
constraints on the snail's size, and help explain some of the modifications seen in largerbodied
organisms (Schmid-Nielson, 1984).
The inside of the shell is crystallized calcium carbonate mixed with protein. The calcium is
absorbed from the snail's food and from the surrounding water. Basically, the shell consist of
calcuim cabonate crystal organise within a matrix prottein.calcuim cabonate crystalizes in two
principal forms aragonite and calcite, but calcite as also been found in repaired areas of shell
(Saleuddin and Wilbur 1969). Snails living in environments wit!t high amount of calcium will
grow thicker shells than those that do not. When there only small amount of calcium available
in water, the snail has to spend much more energy to build its shell, so it only makes the

minimum thickness required to survive. The shells of many aquatic as well as land snaill are
ooverd on the outside by a hard skin-like layer of protein that is called the periostracum. The
periostracum of marine snails, sometimes growing quite thick, helps protect the underlining
shell from dissolving, especially in cold water in which the solubility of calcuim carbonate
increses (Vermeij, 1993).
The shell grows gradually over the lifetime of the snail by the addition of calcium carbonate
to the leading edge or opening, and thus the shell gradually becomes longer and wider, in an
increasing spiral shape, to better accommodate the growing animal inside. The animal also
thickens the shell as it grows, so that the shell stays proportionately strong for its size. A
snails shell is formed, repaired and maintained by a part of the anatomy called the mantle.
Any injuries to or abnormal conditions of the mantle are usually reflected in the shape and
form and even color of the shell. When the animal encounters harsh conditions which limit its
food supply, or otherwise cause it to become dormant for a while, the mantle often ceases to
produce the shell substance. When conditions improve again and the mantle resumes its task.
a "growth line" which extends the entire length of the shell is produced, and the pattern and
even the colors on the shell after these dormant periods are sometimes quite different from
previous colors and pattern.
The outer edge of a mollusc's mantle contains glands that secrete color pigments during shell
formation. These pigments control the colors on the outside of the shell. The iridescence on
the inside of the shell is caused by alternating layers of calcite and and aragonite refracting
different wavelengths of light by different amounts depending on the viewing angle. Colour

offers a seamless installation. and there is no limit to the sheet size. Mother of pearl sheets
may used on interior floors, exterior and interior walls, countertops, doors and ceilings.
Insertion into architectural elements, such as columns or furniture is easily accomplished.
2.11 Feeds
The Achatinidae are herbivorous and feed on a wide variety of plants. The feed of snails vary.
Snails have remarkable ability for converting dead and decaying plant into highly nutritious
flesh. Nutrition plays a major role in snail growth. They achieve the highest growth and
reproductive rates with food sources of approximately 50% green leafy materials and 50%
carbohydrate / animal protein supplemented with brewer's yeast and 3-4% calcium
(Alexander, 1997). Adult snails eat tender flower and vegetable plants, decomposing plant
parts and some fruits. Snails of all ages can eat plants such as lettuce, cauliflower, cabbage.
egg plant, taro, banana, pineapple, and pawpaw (Akinnusi, 1998). Oyedokun, (2002) reported
that snails fed with compound rations of 0.2% salt inclusion had higher feed conversion
ratios, early attainment of sexual maturity and reduction in the length of time required to
attain market size. Sufficient calcium for shell formation is a particular problem in snail
transparent- Lack of calcium can also lead to stunting and infertility. Ground oyster shell or
agricultural line makes excellent calcium sources. Other sources of calcium include bone
meal, chalk and egg shell (Alexander, 1997).
2.12 Feeding methods
Snails are nocturnal animals because they are more active at night. Thus, the tendency has
always been to restrict feeding and other maintenance activities till the evening and early
hours of the night. Snails can feed at any time of the day especially when fed their specially
preferred feeds such as unripe pawpaw fruits and wet chaff from fermented milled maize

(Aklftftusi, 1995). Alexander (1997) stated that exposure of the snails to continuous light at
night increased their activity and rate of food consumption, thus promoting their rapid
growth. Though snails are nocturna~ they do not feed continuously throughout the night.
Their feeding is sporadic, interspersed with exploratory movements or rest periods. Thus, less
food would be consumed at normal darkness hours, which make snails reared under perpetual
darkness to grow less than those reared under perpetual light (Hodasi, 1982).
2.13 Sanitation and hygiene
According to Alexander (1997), all decaying food should be removed promptly and the cage
should be completely cleaned at least once a week. Slime and faeces should be wiped off the
cage with a wet material. If high stocking density rates are used, the soil will become
saturated with faecal matter and slime. The soil should therefore be renewed once in a month.
To provide the optimum humidity and temperature for breeding snails, a three layered
substrate is recommended- a bottom layer of gravel and water, a second layer of moist soil
and a third layer of dry leaflitter. Small earthworm can be introduced to help turn the soil and
keep the soil aerated. Care should be taken when handling snails. Gloves should be worn
during feeding and gathering (Alexander, 1997).

3.1 Experimental area
The research was carried out at the Physiology Laboratory, College of Animal Science and
Livestock Production (COLANIM) and Snail Research unit, University of Agriculture~
Abeokuta, Ogun State. The location lies within the rainforest belt of Western Nigerian,
latitude T'lO'N, longitude 3 0 2'E and altitude 76 0 mash. The climate is humid with a mean
annual rainfall of 1,037 mm, mean temperature of 34.7 C, and a mean relative humidity of
82% (Google Earth, 2003).
3.2 Experimental animals and management
Twenty (20) shells and eighty-two (82) Archachatina marginata weighing between 88 g to
485 g were used for the experiment. The snails were purchased from Delta State (88-289 g).
Edo State (245-359 g), Imo State (131-279 g), Abeokuta, Ogun State (159-320 g) and Enugu
State (213-485 g). The snails were housed in twelve (12) wooden cages filled with sun-dried
top-humus to a depth of 5 cm, with Snails sourced from similar location being placed together
in the same cage. The snails were provided with feed and drinking water both supplied ad
libitum. The feed was a mixture oflayers mash and dried pawpaw leaves (1:1, w/w). Feed and
water troughs were washed daily, while the soil in each cage was changed bi-weekly.
Collection of data through measurement of various shell parts for shell parameters was
carried out on the snails.
3.3 Experimental materials
The materials used during the duration of the experiment include: sensitive scale, vernier
caliper, measuring cylinder (250 ml), board pins, ruler, thread, washing bowl, detergent, plane
sheets, snail (dam), snail shells, damp cloth and water.

3.4 )fethodology
The experiment was conducted in two phases:
Phase I:
The phase was concerned. with the measurement of the live snails for their shell
parameters. The snails were cleaned with a damp cloth to facilitate the removal of
dirt which may have glued to their shell and subsequently affect their weight. The
snails were placed on a sensitive scale one after the other to determine their
weights, after which they were measured directly with the vernier caliper to
determine their length and width. A thread was lined along the length of each
whorl found on the snails shell to determine their width. This was possible by
placing the thread along the length of a ruler.
Phase II:
It involved the collection of data from the shell of a dead snail (Adult) gathered
through the measurement of the shell parts. The shells were properly washed with
a detergent and rinsed with water to ensure that the shells were free of dirt and
micro~organisms. The shells were measured for their length, weight, width and
width of the whorls using the sensitive scale, vernier caliper, thread and a ruler.
The internal volume of the shell was also noted. This was done by filling the shell
to the brim with water after which the water contained in the shell was measure
with a calibrated cylinder (250 ml).
3.5 Data collection
Seven shell measurements were taken in order to describe qualitatively the effect of other
shell parameters on shell surface area and internal shell volume.
(1) The weight (g)
(2) The length (em)
(3) The width (em)
(4) The number of whorls on a snail
(5) The whorl width (em)
(6) The internal shell volume (mt)
(7) The surface area (cm:t.)
The weight was determined directly on a sensitive weighing scale. Shell height measured
along the axis, and shell width measured across it, were also measured using a vernier caliper.
The shell volume was obtained by filling the shells to the brim with water and subsequently

measuring the water contained within the shell in a calibrated cylinder. The shell surface area
was determined
using the grid system.
3.6 Statistical analysis
The data obtained were analyzed using Pearson correlation matrix to determine the degree of
association between shell parameters. Curvilinear regression and analysis of variance
(ANOVA).
The regression equation was expressed as Y =A+B(X),
where Y= Dependent
variable e.g. shell volume or surface area.
A=Constant
B=Regression
X=Independent
coefficient
variable e.g. length, weight or width.

Table 1: Correlation matrix of shell volume and surface area with linear values
of shell parameters of Archachatina marginata
Parameter Shell WT LTH WDT WW1 WW2 WW3 WW4 WW5 WW6
volume
Shell weight (WT) 0.777**
Shell length (LTH) 0.889- 0.734*
Shell width (WOT) 0.929*" 0.805" 0.819"
it! wharf (WW1) 0.521 0.451 0.530 0.525
2lld wholt (WW2) 0.661 0.569 0.679 0.587 0.574
3"' vmorl (WW3) 0.670 0.654 0.788** 0.722* 0.643 0.495
4th vmolt (WW4) 0.830- 0.761" 0.884- 0.819*** 0.544 0.659 0.756"
5th vmorl (WW5) 0.606 0.557 0.754" 0.533 0.583 0.595 0.624 0.762**
6'" vmorl (WW6) 0.853- 0.793" 0.835- 0.934- 0.473 0.419 0.616 0.706* 0.293
Shell surface area 0.960"* 0.793" 0.835- 0.934*" 0.473 0.528 0.711 0.781* 0.490 0.886"*
*P

whorl width six (WW6) having the highest correlation co-efficient (r) of 0.886 to the shell
250 J
18
...•
E 16
•••
to 200 14 E
GI 12
•••
..
150 ~
III
GI
-..
6
III
•••
::J
100
8
III
Qj 50 4
.c
-SURFACEAREA -LENGTH
II)
2
0 -~..,. , , ,-.-,--r 0
1 2 3 4 5 6 7 8 9 10 1112 13 1415 16 17 18 19 20
Snail shell tag number
10
•..
tlII
c
.!!
Qj
.c
II)

1 2 3 4 5 6 7 8 9 1011121314151617181920
Snail shell tag number

4.1.3 Relationship between shell length and shell internal volume
Figure 3 shows the relationship between shell length and shell internal volume to be a close
one with a correlation co-efficient r = 0.889 and thus highly significant at 0.1% significance
level.
18
16
14
12
N
Euai
160
E
::s
l
~
III
1100
~
.i
E
10 "l
.s::.
!'
~
8 Qi
.s::.
III
6
4
1 2 3 4 5 6 7 8 8 10 11 12 13 14 16 16 17 18 18 20
Snail shell tag number
Fig. 3. Relationship between length and internal shell volume

Figure 4.1.5 Relationship between shell surface area and shell internal volume
Figure 5 shows the relationship between shell surface area and internal shell volume to be a
nearly perfect one. Table 1 expressed the correlation co-efficient r = 0.960. The correlation
was highly significant at 0.1% (P < 0.0001) significance level.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
-VOLUME
-SURFACE AREA

Table 2: Regression equations of surface area with linear values of shell parameters
X y A B r r
LTH SA -96.772 19.338 0.837 ***
WTH SA -160.630 48.339 0.934 ***
WWl SA 51.157 469.002 0.473 *
WW2 SA 15.871 320.905 0.528 *
WW3 SA -56.246 273.730 0.711 ***
WW4 SA 76.974 182.150 0.781 ***
WW5 SA 9.879 56.477 0.480 *
WW6 SA -44.745 29.856 0.886 ***
WWl-
WW6
SA
SA
Bl 29.052 0.922
B232.109
B345.507
B415.260
B511.934
8623.765

with 83.70%. The multiple regressions between surface area and width of whorl one to six
(WI-W6)
was a good estimator of shell surface area at 0.1% significant level with a
regression co-efficient of 92.22% but it is not as accurate or close an estimator when
compared to that of width which has a regression co-efficient of 93.40%.
Length (L): S = -96.77 + 19.34(L)
Width (W): S = -160.63 + 43.34(W)
Width of whorl six (W6): S = -44.75 + 29.86(W6)
WI-W6: S = -101.62 + B(WI-W6)

.u Regression of shell length, shell width and whorl width on intemal sheDvol•••
Table 3: Regression equations of shell volume with linear values of shell parameters
X y A B r P
LTH VOL -157.039 23.500 0.885 ***
WTH VOL -212.992 55.208 0.929 ***
WWl VOL 18.391 593.697 0.521 *
WW2 VOL -47.031 461.633 0.661 **
WW3 VOL -82.373 296.403 0.670 ***
WW4 VOL -134.241 222.395 0.830 ***
WW5 VOL -56.001 81.402 0.602 **
WW6 VOL -74.205 33.037 0.853 ***
WW1-
WW6 VOL -167.801 BI39.719 0.944 ***
B2135.258
B3 -40.861
B44.502
B540.737
B627.783
W6 WTH 2.659 0.574 0.882 •••
*P

(WW6) and width of whorl four (WW4) are also significant at 0.1% level of significance. The
multiple regression between shell volume (V) and width of whorl six (WW6) was the best
estimator of internal shell volume at 0.1% level of significance with a regression co-efficient
of 94.400,/0.It is more accurate an estimator than width (W) which has a regression coefficient
of 92.29%.
Length (L): V = -157.04 + 23.50(L)
Width (W): V = -212.99 + 55.21(W)
Source
(lfOOP
Error
df MS
f O.l34ns
162 0.484
Table 4 shows the summary of the analysis of variance between the actual and the predicted
width. The regression equation between width of whorl six (WW6) and the width was used to
generate the predicted width which was then related to the actual width of the eighty-two (82)
snails. The table shows that there is no significant difference between the actual and predicted
width.
Actual width (n=82): 5.911±O.077cm
Predicted width (n=82):5.968±O.077cm

The expression shows that the average widths (5.911 and 5.968) for the actual and
width are very close.
predicted
9 I
8 1
: :I
~ 4.~
ci 3
2·
1 :
o iTTTTili-rTT-r1"1---r-l---1'TTTTTT"T--r'r'ir-rliTTrrT'rrTT-Tl"l"T
~rl"T'Trl"T'TTTT--l'TT-rT'1-rT-T-r-T"T-1"-1-r-rrTTTTTTTTTTl

From this study, it can be concluded that length, width as well as the whorls width have
significant effect or are good estimators of the surface area of A. marginata with the most
significant of the whorl width been the whorl width six (6). It can also be concluded that a
positive and significant relationship exists between the surface area and the shell volume.
It is therefore recommended that the length, width and width of the whorls especially that of
whorl six (6) be used as estimators for surface area and internal shell volume of A. marginata
It is also recommended that the surface area be used as a parameter for selecting shell volume
for A. marginata and vice-versa.
The surface area and shell volume should be used as parameters for selecting body size in
land snails. This is because the body size can be estimated as s~eU volume which is a more
reliable measurement of land snail size than live-weight because this depends on the state of
hydration and is consequently highly variable in land snails (Baur and Baur, 1998).

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SlJRFACE
AREA WGT LENGTH WIDTH WWl WW2 WW3 WW4 WW5 WW6
206 74.71 15.37 7.62 0.2 0.46 0.8 1.5 2.88 7.92
137 31.76 13.72 6.1 0.12 0.41 0.7 1.35 2.55 5.96
191 70.24 14.76 6.82 0.25 0.45 0.81 1.35 2.8 7.2
134 29.97 11.87 6.05 0.21 0.3 0.7 1.22 2.35 5.55
105 23.93 11.02 5.5 0.15 0.34 0.66 0.95 1.9 5.01
211 45.64 13.81 7.27 0.22 0.47 0.76 1.25 2.05 7.41
109 19.27 11.86 6.23 0.2 0.38 0.7 1.12 2.16 5.8
148 41.18 12.73 6.5 0.25 0.45 0.84 1.31 2.63 6.64
93 17.68 9.62 4.9 0.15 0.33 0.63 0.98 2 4.28
113 33.51 11.56 6.04 0.21 0.47 0.68 1.23 2.34 5.28
118 46.85 11.12 6.04 0.16 0.4 0.63 1.08 2.27 5.16
123 22.19 11.62 5.61 0.15 0.34 0.66 1.12 2 5.86
93 11.15 10.52 5.12 0.15 0.3 0.52 0.94 1.92 4.94
115 27.3 11.82 5.8 0.18 0.34 0.75 1 2.42 5.23
105 49.46 11.72 5.76 0.21 0.39 0.68 1.22 2.32 5.46
137 41.74 12.06 6.11 0.16 0.35 0.7 1.15 2.15 5.73
104 16.69 10.11 5.33 0.16 0.3 0.63 1.02 1.94 5.23
191 65 14.2 7.2 0.2 0.35 0.95 1.4 2.3 7.8
139 56.3 11.1 6.15 0.14 0.37 0.65 1.1 1.7 7.75
149 36.4 10.2 6.6 0.15 0.29 0.6 1.1 2 6.9

G WT lHT WDT WWl WW2 WW3 WW4 WW5 WW6 WW7
3 148.8 10.5 5.7 0.12 0.21 0.26 0.54 1.65 6.85
5 154.8 9.82 4.98 0.09 0.21 0.32 0.8 1.35 6.69
2 136.6 9.68 5.2 0.06 0.18 0.44 0.92 1.29 6.39
19 108.9 9.62 4.5 0.07 0.29 0.65 1.1 1.81 5.2
1 128 10.44 5.21 0.1 0.35 0.91 1.14 2.11 5.22
if18 115.4 9.92 4.67 0.06 0.18 0.62 0.82 1.92 5.23
if14 158.8 11.1 5.62 0.16 0.3 0.72 1.2 2.32 6.2
OT13 120.7 9.71 4.79 0.09 0.25 0.64 1.2 1.82 4.98
OT7 131 9.9 4.82 0.11 0.39 0.68 1.07 2.06 5.55
E01 272.1 12.84 6.3 0.1 0.31 0.72 1.26 2.66 6.42
E02 380 14.98 6.85 0.06 0.2 0.8 1.52 3.22 7.52
EOS 249.5 12.98 6.32 0.1 0.47 0.78 1.29 2.78 6.28
E04 286.1 12.6 6.66 0.05 0.32 0.88 1.25 2.88 5.89
013 202.3 12.5 5.98 0.12 0.42 0.78 1.32 2.87 6.36
012 171.6 11.11 5.8 0.15 0.49 0.72 1.32 2.55 5.57
OTt2 175.2 12.26 5.45 0.09 0.35 0.76 1.3 2.29 6.35
OT7 135.7 10.7 4.98 0.12 0.25 0.61 0.75 2.25 5.2
OTtO 114.5 10.37 4.98 0.12 0.25 0.61 0.75 2.25 5.2
OTtl 124.4 10.81 5.1 0.08 0.31 0.68 1.1 2.35 4.69
oT52 179.7 12.25 5.98 0.2 0.45 0.8 1.12 2.3 7.08
oT56 159.9 11.19 5.93 0.2 0.41 0.7 1.2 2.12 6.52
oT61 136.2 10.1 5.21 0.15 0.4 0.61 1.05 2.25 6.08
oT60 189.3 12.55 5.9 0.2 0.5 0.9 1.8 2.65 7
oT53 124.4 11.42 5.01 0.12 0.42 0.9 1.2 2.35 5.35
oT62 171.9 11.52 5.6 0.15 0.4 0.71 1.15 2.3 5.79
oT59 167.2 10.82 5.71 0.09 0.27 0.74 1.12 2.08 4.77
oT57 134.1 11.32 5.5 0.18 0.4 0.64 1.19 2.28 6.6
oT58 175.3 11.3 5.65 0.18 0.48 0.71 1.2 2.22 6.22
OT54 152.2 10.15 5.23 0.12 0.32 0.6 1.2 2.05 4.86
OT63 130.8 10.52 5.21 0.1 0.35 0.65 1.09 2.05 5.68
DT44 191.7 12.45 6.35 0.2 0.45 0.72 1.25 2.53 7.45
OT49 146.8 13.05 5.66 0.21 0.55 0.9 1.38 2.79 6.25
OT42 103.4 9.9 4.88 0.15 0.25 0.61 0.85 1.79 5.6
OT47 136.6 10.28 5.3 0.08 0.26 0.62 1.19 1.76 5.15
E06 244.9 12.55 6.58 0.18 0.42 0.74 1.15 2.05 6.04
ED5 262.3 13.5 6.75 0.22 0.5 0.88 1.5 2.68 6.48
ED7 359.4 14.15 7.2 0.18 0.57 0.82 1:44 2.96 6.95
ED8 294.1 13 6.45 0.2 0.56 0.77 1.32 0.25 6.2
ED10 359.3 14 7.08 0.2 0.49 0.86 1.45 3.3 6.98
ED9 268.8 13.45 6.88 0.16 0.44 0.85 1.34 2.5 7
DT15 214.5 12.35 6.3 0.21 0.4 0.8 1.3 2.42 7.2
31

0138 180.4 11.45 6.1 0.21 0.4 0.6 1.2 2.42 6.25
QX;l7 1145 11 5.3 0.2 0.4 0.6 1.1 2.15 5.9
...........
156.6 11.95 6.55 0.2 0.45 0.75 1.28 2.5 7.3
120 9.9 5.4 0.14 0.38 0.7 1 1.9 6.3
216.3 11.5 5.91 0.15 0.42 0.7 1.3 2.3 6.56
320.1 14.2 7.15 0.2 0.45 0.9 1.4 2.82 7.3
212.4 12.1 6.15 0.22 0.42 0.71 1.25 2.08 6.3
216 12.1 6.76 0.2 0.4 0.7 1.28 2.3 6.32
205.1 11.94 5.9 0.21 0.45 0.72 1.35 2.78 5.44
158.7 11.2 5.55 0.15 0.44 0.63 1.3 2.31 4.85
86 213.6 11.46 6.08 0.15 0.4 0.76 1.24 2.16 5.86
83 260.9 12.87 6.96 0.18 0.47 0.82 1.5 2.62 6.42
AB1 212.7 11.92 6.12 0.22 0.46 1.02 1.39 2.11 5.65
AB5 194.1 12.02 6.39 0.15 0.41 0.76 1.22 2.28 5.92
0130 124.5 9.36 4.86 0.15 0.36 0.68 1.07 1.97 4.65
0T27 209.3 12.2 5.96 0.24 0.43 0.72 1.22 2.22 6.64
0132 174.1 11.69 5.56 0.2 0.42 0.68 1.25 2.4 5.76
0T26 139.6 10.4 5.4 0.15 0.41 0.7 1.05 2.06 5.1
OT40 157.2 10.87 6.03 0.18 0.36 0.55 1.05 2.18 5.15
OT34 158.3 10.84 5.59 0.21 0.41 0.7 1.12 2.05 5.75
0T28 87.5 11.31 5.35 0.16 0.42 0.68 1.05 2.44 5.8
0133 127.4 10.36 5.21 0.17 0.4 0.68 1.05 2.44 5.8
OT31 154.2 11.64 5.15 0.18 0.31 0.72 1.02 2.26 5.72
OT63 178.7 11.56 5.8 0.25 0.35 0.7 1.08 2.63 4.95
OT64 261.5 13.05 6.62 0.25 0.45 0.8 1.25 2.46 6.24
·OT65 173.5 11.22 6.02 0.21 0.33 0.7 1.07 2.2 5.79
0T70 215.4 12.85 6.02 0.25 0.42 0.72 1.31 2.3 6.16
OT66 289.3 14.06 7.09 0.35 0.49 0.85 1.4 2.69 6.94
OT67 269.4 14 6.78 0.27 0.44 0.8 1.35 2.5 7
E1 351.5 15.15 7.06 0.18 0.5 0.86 1.45 3 6.5
E2 384.5 15.2 7.3 0.09 0.2 0.5 0.87 1.63 3.41
E3 297.3 13.4 6.6 0.22 0.43 0.73 1.41 2.25 6.35
E4 485.4 17.25 7.82 0.12 0.28 0.6 1 1.75 2.97
E5 212.5 12.55 6.16 0.13 0.32 0.73 1.06 2.64 5.81
E6 360.6 14.7 6.89 1 0.25 0.55 0.9 1.41 2.46 6.76
IMl 173.6 11.56 5.1 0.15 0.41 0.65 1.2 2.12 5.05
IM5 181.3 11.95 6 0.1 0.25 0.48 0.67 1.25 2.3 4.92
IM6 187.6 11.82 6 0.1 0.25 0.45 0.75 1.15 2 5.52
IM7 130.6 11.1 5.48 0.15 0.32 0.68 1.06 1.92 5.1
IM8 146.7 10.92 5.42 0.16 0.23 0.66 1.02 2.02 4.9
IM10 279.3 14 6.83 0.12 0.26 0.5 0.81 1.4 2.35 6.76