1. Is Bigger Better: Algal capture rates in the marine invader, Crepidula fornicata.

2. 1
Introduction
Increased global connectedness through trade, travel, and tourism has resulted in the
introduction of nonnative species, which have not only contributed to a decline in biodiversity,
but have become an environmental threat (Munyaradzi and Mohamed-Katerere, 2003). The
introduction of nonnative species into new biological communities impacts native species, such
as posing increased competition for food and space (Vallet et al., 2001; Thieltges, 2005; Viard et
al., 2006; Decottignies et al., 2007; Blanchard et al., 2008). Once nonnative species accumulate
outside of their native range, they can both become a threat to the ecosystems they invade and
impose high financial costs (Frésard and Boncoeur, 2006). For instance, the introduction of
Lates niloticus (Nile perch) into Eastern Africa has resulted in immense economic value in
introduced areas, however it has been catastrophic to the ecosystem and resulted in the loss of
endemic species (Munyaradzi and Mohamed-Katerere, 2003). The introduction of the water
hyacinth in seven African countries has resulted in the infestation of most dams and lakes,
causing serious economic losses to remove it. Costs have been estimated to be between US $20-
50 million every year for the control and eradication of the nonnative species that have been
introduced to not only the US but globally as well.
Crepidula fornicata, the Atlantic slipper snail, is native to eastern North America, but has
been introduced elsewhere, especially in Europe (Hessland, 1952; Minchin, McGrath, et al.,
1995). In Europe Crepidula fornicata has become a particularly important invader in England,
France, and the Netherlands, posing a threat to the oyster and mussel populations that were once
abundant in European bodies of water (Blanchard, 1997), and are now important sources of
aquaculture. The first known occurrence of Crepidula fornicata in Europe was in 1872 in
Liverpool Bay, but populations in this area have since died out. Along with oysters from North
America that were being transported into Europe to restore the oyster industry, many native C.

3. fornicata were accidentally picked up causing them to travel to Europe on marketing ships.
Many times, this species was carried attached to the hulls of shipping vessels as it attaches to
hard surfaces. Crepidula fornicata is known to have been introduced to Essex England between
1887 and 1890 from North America. Rather than natural spread, due to oyster farming (Rayment,
2007) there appears to have been separate introductions from the French Atlantic coast to the French
Mediterranean lagoons and from unknown origin to the Italian and Maltese sites. Thus, the
introduction of C. fornicata in active oyster fishing sites has impacted one of the most important
economic industries in Europe (Blanchard, 2009).
Because C. fornicata is a suspension feeder, consuming algae in the plankton, research has
shown the potential for C. fornicata to impact native and aquaculture species where it has been
introduced and its ability to impact water quality in its native habitat (Johnson, 1972; Beninger,
Decottignies, et al. 2007; Blanchard, 2009). However, very little is known on how C. fornicata
is able to function in the presence of different algal concentrations, or the ability of animals of
different sizes to impact algae in the water. Both the factors of impacting native species and
impacting water quality depend on the snail’s efficiency of particle removal from the plankton
because they are suspension feeders (Newell and Kofoed, 1977; Marty et al., 2003; Barillé,
Cognie, et al., 2006). In this study we tested whether the efficiency of particle capture changes
as a function of snail size and particle density. For size, the ability to capture particles could be a
simple relationship between snail size (shell length) or more complex, especially if the gill
(ctenidium - their feeding structure) scales other than linearly with shell size, or if their feeding is
affected by more than simply the area of their gill. In other words, a larger snail size should have
the ability to filter more algal particles per hour. If there is a direct relationship between the snail
size and filtration rate, then the correlation between ctenidium area and snail size should also be

4. 3
the same. If snail size, particle removal rate, and ctenidium area all have a linear relationship,
then it would mean that gill function is simple and responsible for filtration. The function of
filtering particle through the gill could also be affected by particle density - either the capacity of
the food collection mechanism is greater than the cell density (they could collect more if more
were there) or at some density, the system is operating maximally, such that if operating at high
cell densities it clogs, making feeding reduced (Orton, 1912; Coughlan, 1969; Riisgård, 2001).
Thus C. fornicata impacts will be affected not only by the density of animals, but their
population size structure, and how much plankton there is in the water.
Study system background
Crepidula fornicata, commonly known as the Atlantic slipper snail, is
a serial hermaphroditic, gastropod mollusc (Henry, Collin, et al., 2010).
Small individuals begin as a male and then develop into a female as they
get larger, or if another snail settles on top of them (Coe, 1936; Richard,
2006).
Crepidula fornicata are usually found stacked one on top of
another, with as many as 15 or more animals per stack. When stacked,
the snails on the bottom tend to be females and those towards the top
males, with males mating with all females below them in the stack (Coe, 1936; Collin, 1995;
Collin, 2000; Richard, 2006).
This species mostly resides in shallow subtidal areas such as bays (Henry, Collin, et al.,
2010), and it is native to the Western Atlantic Ocean, especially the Eastern coast of North
America from the Gulf of St. Lawrence to the Caribbean (Korringa, 1942). Crepidula fornicata
Figure 1. Crepidula
fornicata, a nonnative
species found in Europe.
(Photo: the authors)

5. is a suspension feeder, which means that it removes suspended particles (phytoplankton) for
feeding. These snails use their gill, referred to as the ctenidium, for moving water. Although it
was hypothesized that the ctenidium produces two mucus nets, one which filters large particles
from entering the mantle cavity and the other that captures food particles (Declerck, 1995;
Jørgensen et al., 1984), it is not yet known exactly how these animals capture plankton for
feeding.
As a result of being transported along with American oysters, Crassostrea virginica, and
being transported on the hulls of ships, large populations of C. fornicata have been introduced to
Europe (Minchin et al., 2013), and now reside in northwest Europe and areas along the French
coast. The reason this species has been able to thrive so efficiently can be credited to its unusual
mode of reproduction (Coe, 1938; Coe, 1953; Dupont, L., Bernas, et al., 2007) and its lack of
predators in the areas where it has settled (Richard et al., 2006).
Environmental and financial impacts
The spread of C. fornicata to foreign locations raises concerns over the sustainability of
native aquatic populations, as it competes with other suspension-feeding invertebrates for food
and space (Decottignies, Beninger, et al., 2007). Due to its ability to live at high densities in
shallow bodies of water and its high fecundity, it is difficult to eradicate this species (Vallet, et
al., 2006). Also in waters of high concentrations of suspended material, research has shown that
this species encourages deposition of mud owing to the accumulation of feces and pseudofeces
(Barnes et al., 1973). Crepidula fornicata is considered a pest to commercial oyster beds as it
competes for food and space and deposits mud on them causing reduced growth and movement
of oysters (Blanchard, 1997). Crepidula fornicata is competing with oysters in areas like Essex

6. 5
in England (Orton, 1912), and if this continues, the spread of the slipper snail will have negative
effects on the commercial interests of oyster marketing causing people to lose jobs and hurt the
economy.
Crepidula fornicata also poses a threat to marine biodiversity where it has been introduced
(Thieltges, 2005). To understand if C. fornicata has an advantage over native European
molluscs in its ability to filter more particulate matter, we tested if there was a relationship
between snail size and the filtration rate by the gill. In order to test the particle capture
efficiency of Crepidula fornicata, it was tested across a range of sizes, from newly
metamorphosed individuals to large adults. Different algal concentrations were tested in order to
understand how algal removal rates for C. fornicata change as the density of algae changes and
the potential for this species to impact others where it has been introduced, and impact water
quality in its native range.
Materials and Methods
Sample collection and collection location
Crepidula fornicata was collected from two different locations on the North Shore of Long
Island, New York. Snails were collected from low intertidal, shallow subtidal areas accessible
from the shore at low tide. The first location for snail collection was Crab Meadow Beach (40°
55' 42.3660'' N, 73° 19' 29.3268'' W). The second
location for snail collection was Poquott Beach
(40° 57' 28.9728'' N, 73° 4' 0.9696'' W).
Laboratory stock conditions
Once collected, C. fornicata was maintained
Figure 2. Crepidula fornicate were kept in a
controlled temperature and salinity tank.
(Photo: the authors)

7. in the lab and placed in a recirculating and temperature regulated tank. All tanks were kept at
27-30 PSU and a temperature of 15°C. Snails were fed 5 mL of a concentrated shellfish diet (10
billion cells/mL) into a 75 gallon tank. The concentrated algae was diluted with 1,000 mL of sea
water and dispensed with an enteral feeding bag to ensure that feeding was conducted at a slow
rate over a long interval of time. Juvenile snails (1 - 10 mm), were produced by rearing larvae to
metamorphosis and were then isolated in glass dishes with filtered sea water that was changed
weekly. All snails were kept at a temperature of 18°C, and were fed a diet of 20,000 cells/mL of
the alga Isochrysis galbana, Strain T-Iso.
Size class
Crepidula fornicata in both their juvenile and adult stages were used in this study. For large
snails, shell dimensions (N = 145) were measured using digital calipers, and all measurements
were recorded in mm, ± 0.1 mm. Snails less than 7 mm were measured with a computer assisted
image analysis system (Image Pro). We used snails ranging from 1.0 mm to 36.0 mm.
Quantifying size-specific algal removal rates
To test the clearance rate of C. fornicata, the alga Isochrysis glabana, Strain T-Iso was
grown in the lab. The T-Iso (20,000 cells/mL) was grown in a 2000 mL flask with sterilized
seawater with f/2 growth medium and aeration to provide constant circulation to prevent the
settlement of any cells and reduce self shading. New algal cultures were started on a regular
basis to insure that we had healthy algae for each of our experimental tests. To keep
contamination to a minimal level, T-Iso was grown in a laboratory chamber that was kept at
18°C. Algal density was determined daily using a hemocytometer. To determine average cell
density each day, 10 mL of highly concentrated algae was mixed thoroughly by consecutively

8. 7
pipetting the alga in order to prevent cells from settling to the bottom of the beaker. We then
pipetted two drops of dense algae onto a hemocytometer. The hemocytometer was then viewed
under a compound microscope at 100x magnification. The visible cells viewed on the 5x5 grid
lines were counted and recorded in order to derive the average cell count. The grid has a
uniform depth, allowing the cell density to be calculated.
Target algal concentrations used for the experiment were 20,000 cells/mL, 40,000 cells/mL,
60,000 cells/mL, and 80,000 cells/mL. Specific test densities were derived using the
mathematical formula C1xV1=C2 xV2. C1 represented the initial concentration from
hemocytometer counts, V1 represented the algae volume needed to reach the target
concentration, C2 represented the target concentration, and V2 represented the volume of the
volumetric flask. After determining the volume of algae needed to make the target
concentration, the algae was then pipetted into a volumetric flask followed by fresh, 0.2 µm
filtered seawater. The solution was then poured out of the volumetric flask into a beaker such
that constant pipetting of the solution would result in a homogenous solution that would be
acceptable for accurate cell density counts with a Palmer Counting cell.
Determining cell density with a Palmer counting cell
After creating a known concentration of T-Iso, a sample of the target solution (specific test
densities of 20,000 cells/mL, 40,000 cells/L, 60,000 cells/mL, and 80,000 cells/mL) was placed
on the 0.01 mL Palmer Cell (17.71 mm x 0.4 mm deep). The Palmer Cell was set up such that a
cover slip was placed on it in which the concentration was then pipetted into the Palmer cell at an
angle to avoid any formation of air bubbles between the Palmer cell and the glass cover slip.
Next, the Palmer cell was placed under the compound microscope under the magnification of 10

9. x to examine moving cells in view. Cells were identified according to their structure and
movement, and then the number of cells in each view was counted (area of view = 2.58 mm2).
The total number of views to be counted depended on how many views it took to reach about a
100 cell count in total. The equation shown below was used to determine cell density.
(area of whole Palmer cell/area of one view at 100x) x (number views counted) x (number
cells counted) = (cells/0.1mL) x (10) = cells/mL.
Use of chambers for determining clearance rates
When assessing clearance rates of
Crepidula fornicata, we isolated
each snail into different chambers
designed for respirometry (30 mL,
4 mL, and 1 mL depending on
snail size) because they held a
known volume and could be constantly
stirred with a magnetic stir bar, making
sure the algal solution was constantly
available to the snails. Snails were placed on a stage (created according to respirometry chamber
size) to avoid damage to snail from the spinning stir bar, and then the chamber was placed on the
stir plate. The respirometry chamber was capped with a cover so that floating particles in the air
would not enter the chambers, and the chambers were covered so the algae were in the dark and
would not grow. The chambers were left spinning for duration of the trial, which depended on
the concentration of the algae and the size of the snail. After checking the concentrations in the
Figure 3. 4 different sized respirometry chambers (a. shows the
30mL chambers, b. shows 500 mL, 4 mL and 1 mL not
included in picture) were used to stir T. Iso concetrations to
prevent particles from settling and hold to the C. fornicata in
place to filter particles. (Photo by authors)
a. b.

10. 9
chambers over intervals of time (such that there was no more than 20% of depression from the
initial concentration), a sample of the final concentration was drawn from the chambers and
placed on the Palmer cell to determine the concentration of the algae. Clearance rates
(cells/mL/hr.) were determined by subtracting the final concentration from the initial
concentration of algae (derived from the Palmer cell count) and then divided by the duration of
time in hours.
Dissecting C. fornicata to expose ctenidium
To perform dissections on C. fornicata and expose their ctenidium, snails (10 mm – 32 mm;
size limit was due to the fact that smaller size snails had a ctenidium that could not be
differentiated when dissected) that were tested for clearance rates, were put in a freezer over
night. The following day snails were removed from the freezing process and left out to thaw.
Once the snails had defrosted, they were taken out of their shell and placed on petri dishes such
that the organism’s foot was facing down on the dish, and the head was facing towards the
person performing the dissection. The dissections were performed under a dissection
microscope. Using fine forceps (7.0), an incision was made on the top tissue layer (mantle)
covering the ctenidium. The forceps were then used to gently tear apart the top layer, or mantle,
in order to expose the whole ctenidium without separating the filaments from the site of the
incision. The dissected snails were preserved in the refrigerator until photographed.
Photographs were measured with a computer assisted image analysis system (Image Pro). Small
animals have a transparent shell, thus the area of the ctenidium could be measured directly from

11. photographs of small snails with bright transmitted light.
Imaging and measuring ctenidium area
For imaging purposes, a Nikon D90 camera was used in order to take images of dissected
snails and successfully acquire ctenidium area. The camera was placed on a copy stand 39cm
away from the platform, facing downward. Individual dissected snails were placed on a dish and
under the view of the camera such that the ctenidium was completely exposed. In order to
identify the scale of the picture, a metric ruler was used in the setting of the picture. After taking
pictures of the ctenidium, we transferred the images from the SD card in the camera onto the
computer and uploaded the pictures onto the program Image Pro. Via the imaging software
measuring tools, we measured snail shell dimensions and the area of the ctenidium.
Statistical and graphical analysis
Graphical outputs were constructed by finding the OLS (ordinary least squares, Model I
regression) equation, and from there calculating the SMA (Standard Major Axis, Model II
regression) slope. We derived the SMA slope by taking OLS Slope and dividing it by the
correlation coefficient (r). From there we took the mean x and mean y for all 4 different
concentrations and using the equation Y = mX + B, where m = the slope and b = the intercept,
Figure 4. Snails were measured (a), froze in 6-well plates (b) and then dissected.Dissection of C.
fornicata, exposing the gill (ctenidium-feeding structure) is shown in figure 4c. (Photo by authors)
A. B. C.

12. 11
solved to discover the SMA intercepts, allowing us to plot the SMA regressions on our graphs.
SMA regressions are more appropriate for our data because there is variance in both measure for
the x-axis and the y-axis.
Results
We measured the particle collection rate of 140 snails from 1 mm – 32 mm, for four
different concentrations of microalgae. Clearance rates as a function of snail size were plotted
for the four different cell concentrations (Figure 5). For the 20,000 cells/mL concentration, cells
removed per hour increased (mean = 8,777.20 mL) as shell length increased (R2 = 0.739, P-
value < 0.05, Figure 5). For the 40, 000 cells/mL concentration, cells removed per hour
increased (mean =17,173.73 mL) as shell length increased (R2 = 0.802, P-value < 0.05, Figure
5). For the 60, 000 cell/mL concentration, cells removed per hour increased (mean= 33,153.09
mL) as shell length increased (R2 = 0.797, P-value < 0.05, Figure 5). For the 80,000 cells/mL
concentration, cells removed per hour remained slightly the same (mean= 32,844.38 mL) as shell
length increased (R2= 0.432, P-value < 0.05, Figure 5).

13. When all four cell concentrations were plotted together (Figure 6), the relationship between
shell length and cells removed per hour increased when snails were suspended in concentrations
of algae between 20,000 cells/mL and 60,000 cells/mL, yet remained the same when snails were
suspended in a concentration of algae of 80,000 cells/ml (R2 = 0.432).
When we graphed and compared all four cell concentrations, we found that there was no
significant difference when testing the difference among slopes between 60,000 cells/mL and
80,000 cells/mL (P-value > 0.054). The slopes of the collection rates when snails were feeding at
60,000 cells/mL and 40,000 cells/mL, were significantly different (P-value < 0.05). The same
was observed for snails feeding at 40,000 cells/mL and 20,000 cells/mL (P-value < 0.05). Thus,
the size specific particle collection rate increased with cell concentration up to a concentration of
60,000 cells/ml, but then saturated.
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
0 10 20 30 40
20,000
Snail Length (mm)
CellsRemovedperHour 20,000 Cells/mL Regression
R2=0.739
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
50000
0 10 20 30 40
40,000
Snail Length (mm)
CellsRemovedperHour
40,000 Cells/mL Regression
R2=0.802
-10000
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
0 10 20 30 40
60,000
Snail Length (mm)
CellsRemovedperHour
60,000 Cells/mL Regression
R2=0.797
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
0 10 20 30 40
80,000
Snail Length (mm)
CellsRemovedperHour
80,000 Cells/mL Regression
R2=0.432
BA
C D
Figure 5: Relationship between snail length (mm) and cells of microalgae removed per hour for four
different cell concentrations:A 20,000 cells/mL , B 40,000 cells/mL , C 60,000 cells/mL, and D 80,000
cells/mL.

14. 13
Cells/mL OLS Regression
Equation
R2
OLS
Slope
r SMA Slope Avg. X Avg. Y SMA
intercept
20,000 Y=437.305(x)+
3120.8790
0.739 437.30 0.860 508.67 12.93 8777.20 2197.7881
40,000 Y=1103.447(x)+
7296.0074
0.802 1103.45 0.896 1232.2 8.95 17173.73 6143.3305
60,000 Y=2069.276(x)+
3169.4960
0.797 2069.28 0.893 2318.0 14.49 33153.09 -434.4473
80,000 Y=1512.155(x)+
8615.1137
0.432 1512.16 0.657 2300.6 16.02 32844.38 -4017.427
-10000
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
0 5 10 15 20 25 30 35 40
SMA Regression Lines
20,000
40,000
60,000
80,000
Shell Length(mm)
CellsRemovedperHour
Figure 6: The relationship
between shell length (mm)
and cells removed per hour
for snails under4 different
concentrations of T-Iso
algae. SMA regression lines
are color coded for the
different concentrations of
algae. Orange = 80,000,
Green = 60,000, Red =
40,000, and Blue = 20,000
cells / ml.
Table 1: Ordinary Least Slope Regressions (OLS) for shell length versus Cells removed per hour. The SMA
slope, intercept, and average x and y values were used to graph the SMA lines in Figure 6.

15. Figure 7: The relationship between shell length (mm2) and ctenidium area (mm2) along with the relationship
between shell area (mm2) and ctenidium area (mm2) for different sized snails. A SMA regression between
ctenidium area and shell area (y=0.1471(x) + 9.7843), B SMA regression between ctenidium area and shell
length (y=6.0829(x) -66.4590), C log-log graph of ctenidium area versus shell area, D log-log graph of
ctenidium area versus shell length.
The relationship between ctenidium area and shell length, had a strong linear correlation
(R2 = 0.801, Figure 7). The relationship between ctenidium area and shell area, had a strong
linear correlation (R2 = 0.805, Figure 7) as well. When log-log transformed data of shell area
and gill area are compared graphically to the log-log graph between shell length and gill area, an
exponential relationship was found for both (Figure 7).
1
51
101
151
201
251
50 550 1050
Shell Areavs.
Ctenidium Area
Shell Area (mm2)
CtenidiumArea(mm2)
Shell Area vs. Ctenidium Area
R2 = .805
0
50
100
150
200
250
300
0 20 40 60
ShellLength vs.
Ctenidium Area
CtenidiumArea(mm2)
Shell Length (mm2)
R2= .8012
Shell Length vs. Ctenidium Area
10
100
50 500
Snail Area vs. Ctenidium Area
Snail Areavs.
Ctenidium Area
Shell Area (mm2)
CtenidiumArea(mm2)
10
100
8 80
Shell Length vs. Ctenidium Area
ShellLength vs.
Ctenidium Area
CtenidiumArea(mm2)
Shell Length (mm2)
A B
C D

16. 15
Discussion
Crepidula fornicata, better known as the Atlantic slipper snail, was introduced in parts of
Europe through the means of oyster farming (Rayment, 2007). Crepidula fornicata are well
known for their suspension feeding abilities in which they are able to filter the water effectively.
However, this impressive ability of C. fornicata to clear algal particles threatens the ability of
native suspension-feeders to obtain food space (Le Pape, Guérault, et al., 2004). In order to
understand the advantage Crepidula fornicata has over native species, we tested the impact
animal size has on particle filtration rate and whether or not ctenidium area influences gill
function.
The snail’s ability to clear algal cells has allowed them to both filter the water and sustain
their way of life. Our results showed that Crepidula fornicata demonstrated high clearance rates
as their shell lengths increased when exposed to 20,000 cells/mL, 40,000 cells/mL, and 60,000
cells/mL concentrations. However, when exposed to the 80,000 cells/mL concentration,
clearance rates for the snails decreased slightly as the snail’s shell lengths increased (Figure 5).
From this we we’re able to conclude that Crepidula fornicata does have a restriction on the
concentration of phytoplankton they can filter. The fact that snails were able to remove cells up
to a 60,000 cells/mL concentration but nothing past it shows that snails have a limit in the
amount of cells that they can filter. In which the alga cell concentration is higher than 60,000
cells/mL, snails will not be able to control algal concentrations.
Prior to experimentation we believed that Crepidula fornicata was able to clear algae
cells at an increasing rate with cell concentration, but not past a threshold of 60,000 cells/mL.
We also proposed that due to the size of their ctenidium (gill) area, snails would consume larger
amounts of algae. These are the issues addressed in part one of our essential questions “is the

17. snails shell size and ctenidium size a direct correlation with filtration rate?” When we observed
the relationship between ctenidium area and shell area, we noticed that there is a positive
correlation which means that as shell length and shell area increases so does ctenidium area.
Since ctenidium area increases with shell area and shell length, this suggests that gill area plays a
large role in filtering capabilities.
Beyond the realm of species mechanisms, this experiment is important when looking at the
introduction, spread, and impacts on foreign species in native habitats (Munyaradzi and
Mohamed-Katerere, 2003; Le Pape, Guérault, et al., 2004; Richard et al., 2006). Since there
have never been any studies that determine the effect that Crepidula fornicata has on marine
ecosystems, it is crucial to assess the way that this species functions so that we can know how to
save other organisms from displacement in a ecosystem as a result of C. fornicata invasion.
From our results we acknowledge that C. fornicata may not only be detrimental in some habitats,
but it may also play a vital role in marine cycling and water clarity as these animals are highly
effective filter feeders.
Conclusion and Future Works
This study illustrates that Crepidula fornicata possess a unique ability to function in the
presence of different algal concentrations. Crepidula fornicata has the potential to increase their
gill function when exposed to high concentrations of algae, however the maximum concentration
it displays increases in particle removal rate up to 60,000 cells/mL. It is relevant that an increase
in concentration (above the maximum range of concentration) inhibited C. fornicata to clear any
more particles due to the decrease in particle removal rate in 80,000 cells/mL when compared to
the 60,000 cells/mL.

18. 17
To further access the target range and extent of gill function of C. fornicata, ctenidium
dissections were performed to determine ctenidium area via the Image Pro software. Our work
illustrates that ctenidium area increased as snail size increased, which concludes that if in fact
filtration rates increased due to an increase in snail size, then gill function increases in the
presence of dense particle concentrations. While exactly how the ctenidium functions in a wide
range of concentrations remains unknown, our results indicate that the ctenidium has the ability
to select the amount of particle intake, decreasing once it hits its maximum concentration intake
level. Investigation of the ctenidium function in other algal species is currently in progress. We
aim to address how function will vary in the different algal species.
Our understanding of filtering in C. fornicata does not stop here. Our study was limited
to the use of Isochyrsis galbana, strain T-Iso. For a more comprehensive study we propose to
investigate feeding capabilities when the organism is exposed to various algal species.
Specifically we will question: How does ctenidium function across a range of algal sizes?
Knowing that the ctenidium is selective in removal of particles we propose to use large and small
algae Rhodomonas or Nanochlopsis respectively. A thorough understanding of these
characteristics may provide ecosystem managers with insights on how to control not only this
species, but perhaps adapt novel remediation methods if the species are to be removed. Maybe it
is better to be big, but if gills are clogged, then size does not matter.

19. References
Barnes, R. S. K., J. Coughlan, and N. J. Holmes. "A preliminary survey of the macroscopic
bottom fauna of the Solent, with particular reference to Crepidula fornicata and Ostrea
edulis." Proceedings of the Malacological Society. 40.4 (1973): 253-275. Print.
Barillé, L., B. Cognie , P. Beninger , P. Decottignies , and Y. Rincé . "Feeding responses ofthe
gastropod Crepidula fornicata to changes in seston concentration." Marine Ecology
Progress Series. 322. (2006): 169-178. Print.
Beninger, Peter G. , Priscilla Decottignies, Freddy Guiheneuf, Laurent Barillé, and Yves Rincé .
"Comparison of particle processing by two introduced suspension feeders: selection in
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