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On the position of Patina pellucida (L.) (Gastropoda) onthe frond of Laminaria hyperboreaOla Vahl aa Marine Biological Laboratory, DK-3000, Helsingør, DenmarkPublished online: 20 Feb 2012.

To cite this article: Ola Vahl (1972): On the position of Patina pellucida (L.) (Gastropoda) on the frond of Laminariahyperborea , Ophelia, 10:1, 1-9

To link to this article: http://dx.doi.org/10.1080/00785326.1972.10430096

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OPHELIA, 10: 1-9 (August 1972)

ON THE POSITION OF PATINA

PELLUCIDA (L.) (GASTROPODA) ON THE

FROND OF LAMINARIA HYPERBOREA

OLA VAHL

Marine Biological Laboratory, DK-3000 Helsingor, Denmark

ABSTRACT

It is shown that large and small Patina pellucida are differently distributed on the frond of Lami­naria hyperborea and that there is a seasonal change in the preferred place on the frond. Thelimpet orients its body to minimize the impact of water flow.

INTRODUCTION

Patina pellucida is an annual macroherbivorous limpet living principally on va­rious Laminariaceae. Graham & Fretter (1947) suggested a close relationshipbetween the life cycle of this species and those of Laminaria digitata (Hudson)and L. hyperborea (Gunnerus). According to these authors, L. hyperborea producesnew cells at the base of the lamina in winter, and the old frond, which is borneon the distal end of the new growth, is cast off in April-May. In the spring, Patinamigrates to the basal parts of the old frond of L.hyperborea, but most individualsare presumably cast off with it, although some move further down and enter theholdfast, where they excavate a hole by feeding, a behaviour not found in Norway(Kain & Svendsen, 1969). Patina dies after spawning, which takes place in thewinter or early spring (Graham & Fretter, 1947; Vahl, 1971). In the Lough Inerapids Ebling et al. (1948) found that Patina occurred in highest density at awater current of 1.0-1.5 m/sec.

Among the limpets an orientation of the body in relation to the flow of wateris often found (Abe, 1931; Abbot, 1956; Funke, 1968; Test, 1945). It has beensuggested that this minimizes the danger of being dislodged by water movement(Abbot, 1956; Test, 1945). Patina lives on the smooth surface of the 1aminarians,has a streamlined shell and is usually found in exposed localities. The literaturerecords no observations on orientation of this limpet.

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2 OLA VAHL

MATERIALS AND METHODS

The material was collected near Bergen, Norway, at the islets Lyroddane, anexposed locality close to the sea. Samples for the study of growth were takenfrom 16 January 1969 to 5 February 1970 (Vahl, 1971). Recordings of both dis­tribution and orientation on the fronds were taken from 13 March 1969 to 5February 1970.

Whole specimens of L. hyperborea were detached from the rock by looseningthe holdfasts with a paintscraper and transferring them to bags. After a bag wasfilled, it was immediately taken to the surface and the algae immersed in 2.0­2.5 %alcohol in sea water for a few minutes. This was found to prevent the lim­pets from moving, but not to detach them from the algae in any large numbers.Of the total number of Patina treated in this way, 89 %(589 individuals) remainedattached to the algae. In addition, 126 individuals were observed in situ duringdives. Three orientations of the limpets on the lamina were distinguished:

1. head pointing towards the basis; 2. head pointing towards "fingertip"; 3. headpointing to either side of the axis between the basis of the frond and the "finger­tip". Position 1 and 2 both occupy a sector of 90°,3 occupies 2 x 90° (see Fig. 3).If the limpets are randomly oriented they should occur twice as often in position3 as in each of the positions 1 and 2.

In order to compare the positions of limpets from fronds of different sizes,the distance from the base of the lamina to the limpet was related to the distancefrom the base of the lamina to the end of the "finger" on which the limpet wassitting. Thus the ratio s = distance basis to limpet/distance basis to "fingertip"gives the location of the limpet on the frond.

The frond of L. hyperborea was divided into three sections: proximal, middle,and distal parts, corresponding to "s" values 0.000-0.333; 0.334-0.667; 0.668-1.000.The following null hypothesis was tested by means of the chi-square test or the"Fisher exact probability test" (Siegel, 1956): The ratio of specimens larger than

TABLE 1. Probability for equal distribution of P.

pellucida with a shell length larger than 7.0 m andsmaller than 7.0 mm. Degrees of freedom = 1.

Date

13. iii. 69 - 12.vi.6924.vii.69 - 29.viii.6911.x.6921.xi.69 - 5.ii.70

x2

16.470.015.48

p

P> 0.05*0.001> P

P> 0.900.02> P> 0.01

* by use of "Fisher exact probability test" (Siegel, 1956).

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POSITION OF PATINA ON LAMINARIA 3

60

40

20

o

distal 3 rd of frond

4

middle 3 rd of frond

D>7.0mm;

~ <7.0mm;

observednumber

relativenumber

(/)cQl

E()

~ 40(/)

'f-

0....Ql 20.DE::JC

0

40

38

proxi mal 3 rd of frond

36

5

20

o13.111.-

12.V1.6924VII. - 11.X.69

29.V1I1.6921.X1.69 2.1.70 5.11.70 date

FIG. 1. Numbers of P.pellucida larger than 7.0 mm and relative numbers of limpets smaller than7.0 mm shell length, on the proximal, middle, and distal thirds of the frond of L. hyperborea.Observed numbers indicated. The relative number of small limpets on each section was com­puted as number of small limpets on each section of the algae X total number of large limpets/total

number of small limpets.

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4

S

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

OLA VAHL

~2~. .~(25) (301 ~

(1~~.(19)

13.111.69 18.IV.69 8'v.69 12,V1.69 24VI1.69 dateFIG .. 2. Mean of "s" (see text) from 13.iii.69-24.vii.69. Total number for each collection indicated.

7 mm to the number of specimens smaller than 7 mm is the same, within thelimits of sampling error, in the group with "s" values 0.000-0.333 as in the groupwith "s" values 0.668-1.000.

If there is a gradual change in the relative number of small and large limpetsfrom the base to the end of the frond, as was the case in most of my collections,the numbers from the middle third of the frond would be intermediate betweenthose from the proximal and distal thirds. The values from the middle third ofthe frond were, therefore, disregarded in order to strengthen the chi-square test,which is not sensitive to order when the number of degrees of freedom is largerthan one.

My thanks are due to Dr. W. Nicolaisen, Helsing0r, for help with the statistics.

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POSITION OF PATINA ON LAMINARIA

RESULTS

5

The statistical analysis shows that the limpets are not equally distributed on thefrond (Table 1, Fig. 1). The deviations from an equal distribution of the two sizegroups on the frond indicate that the large limpets have a seasonal change in thepreferred place on the lamina (Table 1, Fig. 1). After the main spawning in winterthe limpets that have not yet spawned (Vahl, 1971) migrated down to the lowerparts of the lamina (Fig. 2) where some of them survived till October (Table 2).On colonizing the algae in August-September (Vahl, 1971) the juvenile Patinamoved to the distal parts of the fronds, but as the year progressed, they domin­ated more and more of the proximal part (Table 2).

The difference from a random orientation of Patina on the frond is generallyhighly significant (Table 3). There is, however, no significant difference betweenthe numbers of limpets pointing their head towards the base of the frond andthose pointing it towards the "fingertips" (Table 4), indicating that Patina prefersto have the long axis of the body parallel to the axis between the basis of the frondand the "fingertip".

TABLE 2. The distribution of large (> 7.0 mm) and small « 7.0 mm) P. pellucida

on L. hyperborea during the cause of year.

Patina: size group with largestrelative number (from Fig. 1)

Life cycle of Life cycle ofDate proximal middle distal Laminaria Patina pe11ucida

third of third of third of hyperborea

frond frond frond

24.vii. - frond large, colonizing of29.viii.69 large small small medium dry matter Laminaria

11.x.69 large small small maximum dry maximum densitymatter

21.xi.69 small large large fruiting started most individualsmature size

2.i.70 small small large growth of new main spawningfrond started

5.ii.70 small small large low dry matter main spawningnearly ended

13.iii. - large large small period of rapid spat not on12.vi.69 growth, old Laminaria

frond cast off

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6 OLA VAHL

TABLE 3. Probability for random orientation of P.

pellucida on the frond of L. hyperborea. Degrees offreedom = 3.

Proximal third of frondMiddle third of frondDistal third of frond

x2

12.0010.1747.38

p

0.01 > P> 0.0010.02 > P > 0.010.001 » P

On 21 November 1969, the limpets were sufficiently large and occurred insuch a high density that their orientation could be noted in situ. It appeared thatthose limpets sitting on the inner third of the lamina had oriented themselves withtheir heads towards the fingertips and those on the outer third towards the baseof the frond (Fig. 3).

DISCUSSION

Laminaria hyperborea has a stiff stipe which yields but slightly to the waves;only the frond is carried to and fro by the water.

During moderate wave action, such as experienced on the days of collection,the distal parts of the fronds will mostly be exposed to a current running towardsthe tips, whereas nearer the stipe the direction will change with the incoming andoutgoing waves. Patina has a streamlined shell which must give the lowest resist­ance against the flowing water when the head of the limpet is pointing towardsthe current (Yahl, 1971). It should, therefore, be expected that limpets sitting onthe distal lamina pointed their head in the direction of the stipe, and this wasconfirmed by the in situ observation (Fig. 3). On the algae harvested the same

TABLE 4. Probability for randomness between orientations I and 2. Degrees offreedom = 2.

NumbersI

Expected numberPosition 1 2 position 1 X2

~-

Proximal third of frond 43 39 221 39 = 43.99 0.022196 x

Middle third of frond 66 66 221 66 = 74.45 0.959196 X

Distal third of frond 112 91 221 91 102.65 0.852196 x

Total 221 196 221.00 1.833

0.50> P> 0.30

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POSITION OF PATINA ON LAMINARIA 7

proximal 3rd

n=38

middle 3rd

n =41

distal 3rd

n=47FIG, 3, Orientation of P. pellucida on the frond of L. hyperborea, Noted in situ, 1. head towardsbasis of frond, 2. head towards "fingertip", 3. head of either side of the axis between the basis

of the frond and the "fingertip".

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8 OLA VAHL

day, however, Patina showed the same tendency as the material as a whole, i.e.,only a preference for orienting the long axis of the body parallel to the current(Tables 3-4). This discrepancy might arise from the handling of the material. Inthat case, however, one should expect a random orientation, which was not thecase.

A detailed study of the currents around the frond of L. hyperborea is lacking,but the movement of the alga must give rise to a current gradient along the frond.The current is least at the distal parts, which are carried passively along most ofthe time, giving little movement relative to the water. If the shell of Patina hasdeveloped more favourable hydrodynamic characteristics in the larger limpets(Vahl, 1971, fig. 8), then the larger ones are less likely to fall off in strong current.As the limpet is influenced by water movement to such a degree that it orients itsbody relative to the prevailing current, it should be expected that the distributionon the lamina would reflect the influence of the water current. This seems to bethe case. In the Lough Ine rapids Ebling et al. (1948) found a marked maximumin the density of Patina at a current speed of 1.0-1.5 m/sec Purchon (1968, p. 381)discussed this preference for medium water movement and argued that althoughthe current may operate through dependent factors at low velocities, resulting ina low density, a current above 1.5 m/sec probably makes it difficult for the lim­pet to move on the frond, both for the newly settled individuals and for the adults.The newly settled limpets are not affected because they do not occur on the algae(Vahl, 1971). As the juveniles seem to have less favourable hydrodynamic charac­teristics than the larger ones, they preferably sit on the outer parts of the frond,where the current is least (Table 2). At a size of about 8 mm (Vahl, 1971) Patinastarts spawning, and later the spent and weakened individuals fall off.

Graham & Fretter (1947) found that on L. digitata the limpets migrated to­wards the base of the frond. The migration took place mainly before November.They suggested that this behaviour saved the breeding stock from losses due tofragmentation of the distal parts of the frond. On L. hyperborea the limpets tendto migrate down the frond in spring and summer (Fig. 2). This may save some ofthe limpets from being cast off with the old lamina in April-May, as suggestedby Graham & Fretter (1947). It will not, however, have any effect on the breedingstock as the limpets that take part in the main spawning colonize the algae afterthe migration has ended (Vahl, 1971).

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POSITION OF PATINA ON LA MINA RIA

REFERENCES

9

ABE, N. 1931. Ecological observations on Acmaea dorsuosa Gould. Sci. Rep. Tohoku Univ. BioI.,7: 403-427.

ABBOT, D. P. 1956. Water circulation in the mantle cavity of the owl limpet, Lottia giganteaGray. Nautilus, 69(3): 79-87.

EBLING, F. J., J. A. KITCHING, R. D. PURCHON & R. BASSINDALE. 1948. The ecology of theLough Ine rapids with special reference to water currents. 2. The fauna of the Saccorhizacanopy. J.Anim.EcoI., 17: 223-244.

FUNKE, W. 1968. Heimfindevermbgen und Ortstreue bei Patella L. Oeco1ogia (BerI.), 2: 19-142.GRAHAM, A. & V. FRETTER. 1947. The life history of Patina pellucida (L.). J. mar. bioI. Ass. U. K.,

26: 590-601.KAIN, J. M. & P. SVENDSEN. 1969. A note on the behaviour of Patina pellucida in Britain and

Norway. Sarsia, 38: 25-30.PURCHON, R. D. 1968. The biology of the Mollusca. Pergamon Press, Oxford. 560 pp.SIEGEL, S. 1956. Nonparametric statistics for the behavioral sciences. McGraw-Hill, New York.

312 pp.TEST, A. R. 1945. Ecology of California Acmaea. Ecology, 26: 395-405.VAHL, O. 1971. Growth and density of Patina pellucida (L.) (Gastropoda: Prosobranchia) on

Laminaria hyperborea (Gunnerus) from western Norway. Ophelia, 9: 31-50.

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