Download Littorina littorea Falmouth, Massachusetts Kate Buckman, Annette Hynes, and Elizabeth Orchard

Movement of the common periwinkle (Littorina littorea) at Woodneck Beach,
Falmouth, Massachusetts
Kate Buckman, Annette Hynes, and Elizabeth Orchard
(for Marine Invertebrates of Cape Cod, Topics Course, Fall Semester 2005)
Abstract
The intertidal community is an interesting ecosystem to study because of its clear zonation of plants and
animals attributed to such factors as physical and competitive pressures. While sessile organisms are
forced to maintain a specific location, motile species are capable of changing their position, and therefore
are able to maintain a preferred tidal height. This ability is particularly striking with the snail Littorina
littorea, whose trails can cover a beach at low tide. In these experiments we studied periwinkle movement
with respect to tidal cycle. We also observed winkles on the move to determine velocity and direction of
motion of both submerged and above water individuals. We determined that, while periwinkles are capable
of “large-scale” movements, they tend to remain stationary during the course of a tidal cycle.
Introduction
The intertidal zone has long been the setting for classic ecological studies. While
the observation of sessile species is straightforward, the distribution of intertidal species
along physical gradients is less concrete for mobile species. Adult migration influences
patterns of biodiversity and community structure and is significant in determining species
ranges, extinction rates and coexistence (Davidson et al., 2004). Invasive species also
add complexity to intertidal environments. They affect the ecology and evolution of
native species through competition, predation, hybridization, disease, and structural
engineering (Grosholz, 2002). For both its motility and invasive history, the periwinkle
Littorina littorea is important in shaping the biodiversity of New England intertidal and
subtidal habitats.
L. littorea (Fig. 1) is known as the common periwinkle, the edible periwinkle, and
the wrinkle winkle. Its range extends from the British Isles and northwest Europe to the
North American Atlantic coast from Labrador to New Jersey. L. littorea became
abundant in New England only after European settlement in America and the first live
specimen was collected in 1840 (DFO report, 1998). It has displaced the periwinkle L.
palliata and the mud snail Ilyanassa obsoleta in some areas (DFO report, 1998;
Brenchley & Carlton, 1983).
The average winkle lives three years and grows to a shell height of 20 mm, but
the largest recorded winkle grew to 52 mm (Jackson, 2005). Winkles eat microalgae
such as benthic diatoms and dinoflagellates as well as macroalgae such as Ulva lactuca
and ephemeral and juvenile green, red and brown algae (Jackson, 2005). Winkles
aggregate and inhabit the understory of rockweed such as Fucus vesiculosis and
Aschophyllum nodosum but can also be found on rocks, in crevices, and on sand (DFO
report, 1998). There are about twelve species of the genus Littorina, the most common
in New England being L. littorea, L. obtusata, and L. saxatilis. L. littorea can be
identified by its striped tentacles and its spire that is neither as sharp as that of L. saxatilis
nor as smooth as that of L. obtusata (Crowe, www). These three littorinids also have
very different modes of reproduction; L. littorea releases eggs to the sea, hatching into
planktotrophic larvae while L. obtusata eggs hatch into crawling juveniles and L. saxatilis
has direct development (Crowe, www).
Motile intertidal animals need to be able to maintain their position on the shore
and to orient themselves if they are dislocated or if the preferred habitat changes
(Gendron, 1977). L. littorea moves in the direction of the preferred tidal height when it is
dislocated (Gendron, 1977; Petraitis, 1982). On Gansett Point, Woods Hole, MA, the
greatest winkle densities are at and below mean low water (MLW) with larger winkles
preferring lower depths and having a larger range (Gendron, 1977). Winkles at the upper
levels migrate downward in winter. Some investigations have shown that winkles use
phototactic and geotactic responses to orient themselves (Petraitis, 1982), but others have
shown the primary directional cue to be wave motion (Gendron, 1977).
As winkles move, they mark or track mucus trails. Mucus trails are energetically
costly, so the winkles must gain some benefit from making them. Mucus trails bind
microalgal cells on which the tracker winkles can graze (Davies and Beckwith, 1999).
Trail-following may also aid in winkle aggregation for food, shelter or reproduction. The
complexity of winkle motion is less than chaotic, as in Brownian motion, so motion is
non-random and directional (Erlandsson & Kostylev, 1995). Winkles follow conspecific
trails more often than trails of other species, but reports differ on whether the winkles
follow conspecific trails or their own trails more often (Davies and Beckwith, 1999;
Erlandsson & Kostylev, 1995). Male winkles mount whatever snail they encounter on a
trail; however, males may identify females and even trematode-infected females, which
can become sterile, by their trails (Erlandsson & Kostylev, 1995). L. littorea engage in
fewer male-male copulations than L. saxatilis, indicating a difference in trail-following
behavior in these two species (Erlandsson & Kostylev, 1995).
In this study, we examined the site fidelity, distance, and velocity of motion of
Littorina littorea at Woodneck Beach, Falmouth, MA.
Materials and Methods
The three experiments performed are listed in Table 1. All periwinkles
participating in the study were marked at low tide, using nail polish (Revlon ‘raven red’,
‘twinkled pink’; Nailslicks ‘electric blue’, neon green). If the shells were wet, it was
necessary to dry them with a cloth. On 25 Sept 2005 we marked 100 periwinkles at each
of three sites at Woodneck Beach. The sites (Fig. 2) consisted of the seaward face of a
large rock located near the low tide line in the middle of the beach (‘raven red’ winkles),
three small rocks in a channel connecting the ocean to the marsh behind the beach (green
winkles), and a “winkle mat” consisting of numerous periwinkles aggregated on algae
near the marsh (‘twinkled pink’ winkles). We placed rocks on the winkle mat to facilitate
finding the same location again. The following day at low tide we returned to each site,
counted the number of painted winkles that were visible, and measured the approximate
distance of winkle movement. Winkles were located by finding the original site of
marking and walking systematically in increasingly larger circles around the site.
Distance of winkle movement was measured from a central point in the original marking
area to the winkle, as it was impossible to determine exactly where the winkle started
from.
On 02 Oct 2005 we returned to Woodneck and conducted winkle velocity
measurements. As winkle trails were only readily visible in sandy areas, all velocity
measurements were made on sand both exposed to air, and submerged beneath the water.
Three snails were observed on the exposed sand, two were on a mucous trail (Fig. 3a),
and one was not following a previously made trail. The snails were observed for 10
minutes and the distance moved during that interval measured. Eight snails were placed
in a line a few centimeters above the water level and observed for 10 minutes while being
covered by the incoming tide (Fig. 3b). Concurrently, two fully submerged snails were
observed and their distance traveled measured.
On 12 Oct 2005 100 snails were again marked at low tide at three locations on the
beach: an area of cobbles, the same large rock as experiment one, and the same winkle
mat as experiment one (Fig. 4). The channel was not used in this experiment due to the
difficulty relocating snails as a result of shifting sand in previous experiments. All
winkles were marked with the same color nail polish (Nailslicks ‘electric blue’) to
eliminate potential effects of selective predation based on winkle color. The cobble and
the winkle mat site were marked with stakes. We returned to each site at two hour
intervals until high tide, and again looked for marked snails and measured their distance
from a central starting point.
Table 1
Date
Time
25/Sep/05 0630-0800
Tide
level
1.0
26/Sep/05 0730-0900
1.2
02/Oct/05 1230-1430
0.3
12/Oct/05 0930
1200
1400
1600
0.7
Habitat(s)
Objective
Rock, channel, algal mat near
marsh
Rock, channel, algal mat near
marsh
Mark and
release
Recapture,
measure
distance
Velocity
experiments
Mark, release,
recapture
Sand bar parallel to cobble
beach
Cobble beach, Rock, algal mat
near marsh
4.5
Results
Results for the first set of winkle deployments are summarized in Table 2. The
greatest recovery after one full tidal cycle was achieved on the large rock, with 58
winkles recovered in the marking area and 8 winkles either on different rock faces or on
the seafloor surrounding the rock. The greatest distance moved was 254 cm, though we
were unable to determine whether the winkle had moved itself there independently of
wave action or currents. 24 winkles were recovered in the channel, 10 no longer
associated with the rocks, with a greatest distance moved of 284.5cm. Recovery in the
channel was difficult as the deployment rocks were partially obscured by sand shifting
with the current. Currents were strong at the winkle mat as well, as indicated by our
marker rocks having been washed away. The mat itself appeared to be in the same
position, but only 5 winkles were recovered, even after disturbing the mat to search for
winkles that had moved vertically within the mat as opposed to horizontally along the
substrate.
Table 2
Habitat
Rock
Channel
Mat
# Recovered
58 + 8
24
5
Distances (cm)
68.6, 71.1, 78.7, 81.3, 101.6, 254
12.7, 40.6, 76.2, 81.3, 119.4, 142.2, 226.1, 284.5
Uncertain
The winkle velocity experiments showed a wide variety of movement velocities
(Table 3). In general, winkles on previously established mucous trails moved faster than
those not on trails, but sample size was not large enough to determine if there is a
significant difference. Winkles that were disturbed and placed in a line did not move at
all, and those submerged did not move faster than those on exposed sand. Winkle travel
was not constant; the winkles would often stop for a while for no apparent reason before
resuming movement. There did not appear to be any relationship between winkle size
and distance traveled within the confines of our experimental design.
Table 3
Description
Exposed
Submerged
Mucus trail
No mucus
trail
Line race
Individual
Individual
Winkle
Size (cm)
1.3
0.8
1.0
Distance (cm)
Comments
13.7
15.9
8.3
range
1.3
0
14.0
took a break
crossed a trail
Found a trail but promptly
left it
No motion
Small snail beside him
much faster
Stopped on top of rock in
path
8.9
The third experiment was implemented to determine if the winkles moved while
submerged and returned to a particular position at low tide. Results of these observations
are summarized in Table 4. In the cobble area 40 winkles were recovered 2 hours after
low tide, with a maximum movement of 66cm. Following this time, the stake marking
the site washed away and we were unable to located any winkles despite running snorkel
transects through the area. At the rock, recovery was greatest 2 hours following
deployment with all of the winkles recovered being found on the same face of the rock as
they were deployed. At high tide, a similar number of winkles were recovered, but a
larger number (18) were found off of the deployment face of the rock than at the earlier
times. A number had crawled up the rock and were found at the air/water interface, while
others were on the seafloor surrounding the rock. Conditions were poor at the 1400 hour
observation time, making an accurate count of winkles difficult (noted with *). The same
is true for the winkle mat area. Highest recovery of any site was achieved at the winkle
mat 2 hours after deployment. No significant movement was noticed in the mat at
anytime.
Table 4
Habitat
Time
# Recovered
Cobbles
1200
1400
1600
1200
1400
1600
1200
1400
1600
40
lost
lost
57
20*
30 + 18
71
10*
37
Rock
Mat
Max Distance
(cm)
66.0
167
61
same area
Discussion
The winkles at Woodneck Beach demonstrated an ability to move fairly far
distances, but in general did not take advantage of this ability and showed fairly high and
stable site fidelity. These results support previous observations that periwinkles have a
preferred tidal height to inhabit where they maintain position, and will return to this
height if displaced (Gendron, 1977). There did not seem to be a difference in movement
whether the periwinkles were submerged or not, and most winkles maintained position
both within and over a tidal cycle. In other words, the winkles didn’t move out of place
when submerged, and then return to it for the next low tide or vice versa, they just stayed
in the same place the whole time. In fact, we were still able to find red periwinkles on
the large rock over 20 days after having marked them there. Though this study was able
to demonstrate that the periwinkles at Woodneck Beach do not tend to move from their
assumed preferred position over a tidal cycle, it also raised many questions. Future
studies would benefit from technical and methodical considerations such as finding a
faster drying marker than nail polish, and one that won’t wash off over time to allow for
longer time series, better winkle position markers to facilitate finding sites again, as well
as better methods of quantifying distances and direction of winkle movement. Other
factors to be taken into consideration would be the effect of marking winkles on
predation, the effect of season and weather on winkle motility, and the difference
between subtidal and intertidal winkle movements.
Figures:
Figure 1: Littorina littorea on a mucous trail.
a.
b.
c.
Figure 2: a. Large rock, site of red winkle deployment. b. sandy channel, site of green winkle
deployment. b. winkle mat, site of pink winkle deployment.
b.
a.
Figure 3: a. exposed winkles on trails. b. submerged winkles in line after 10 minutes of
observation.
a.
b.
c.
Figure 4: a. painted winkles on cobbles at low tide. b. large rock during winkle painting.
c. winkle mat during painting at low tide.
References
Brenchley, G. A. and Carlton, J. T. (1983). competitive displacement of native mud
snails by introduced periwinkles in the New England intertidal zone. Biological
Bulletin 165: 543-558.
Crowe, B. Seashore Identification Notes: WINKLES, Family Littorinidae.
http://staffweb.itsligo.ie/staff/bcrowe/bill/styles/frames/marbiol/sshorero/litrslon.h
tm
Davidson, I. C., A. C. Crook, and D. K. A. Barnes (2004). Macrobenthic migration and
its influence on the intertidal diversity dynamics of a meso-tidal system. Marine
Biology 145: 833-842.
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behavior and nutrition of the periwinkle Littorina littorea. Marine Ecology
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(Littorina littorea), DFO Science Stock Status Report C3-46.
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25/08/2005]. Available from:
http://www.marlin.ac.uk/species/Littorinalittorea.htm
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