Cittarium Pica

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A STUDY OF THE GROWTH AND OTHER

ASPECTS OF THE BIOLOGY OF THE WEST

INDIAN TOPSHELL, CITT ARIUM PICA

(LINNAEUS)I

HELEN A. RANDALLInstitute of Marine Biology, University of Puerto Rico, Mayagiiez, P.R.

ABSTRACT

Various aspects of the biology of Cittariurn pica (Linnaeus, 1758) arediscussed, including habitat, feeding habits, growth, movements, reproduc-tion, predators, and commensals. Marking and tagging experiments todetermine growth rate are described.

INTRODUCTION

The West Indian topshell, Cittarium pica (Linnaeus, 1758) (=Livonapica), sometimes known as the magpie shell, is a well known littoral

gastropod which attains a size of four inches. It is widely used as food and

is probably second in economic importance only to the queen conch,Strombus gigas Linnaeus, among the gastropods of the Caribbean region.

The shell is turbiniform and moderately heavy. It is strikingly colored

with irregular markings of black and white (Fig. 1). There is considerablevariation in color pattern, some individuals being primarily black with

few white markings while others are predominantly white. White seems

to be the ground color of the young (Fig. 2). The white of the shell is

often greenish or yellowish, probably from staining by the blue-green algaPlectonema terebrans Bornet & Flahault (identified by H. J. Humm)which penetrates the upper calcareous layers. There is no periostracum,

and in larger individuals the first few whorls are usually eroded. The older

parts of many shells are overgrown with algae, particularly the calcareous

red, Goniolithon brgesenii Foslie. The interior of the aperature is pearly

and the round chitinous operculum, which fits snugly, is translucent olive

(drying to brown) with the spirals showing clearly. The shell makes an

attractive curio either when polished to the nacreous layer or with its outer

black and white coloration intact. It is used by adults of the land hermit

crab Coenobita clypeatus (Herbst) more than any other West Indian shell.

Topshells inhabited by this crab were found near the 1277-foot summit

of Bordeaux Mountain, the highest point on St. John, more than one

mile from the sea.In contrast to the related genus Trochus of the Indo-Pacific, almost

IContribution No. 558 from The Marine Laboratory, Institute of Marine Science, Universityof Miami. Contribution from the Institute of Marine Biology, University of Puerto Rico.The research reported herein was supported in part by grant G5941 from the NationalScience Foundation.


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1964] H. Randall: Biology of Cittarium 425

nothing is known of the natural history of the monotypic Cittarium. Aware

of this and appreciative of its high gastronomic quality, a study of someaspects of its biology was undertaken as part of a nearly three-year marine

biological survey of St. John, Virgin Islands, which commenced in late1958. This survey was begun while the author was a member of theInstitute of Marine Science of the University of Miami and completedwhile associated with the Institute of Marine Biology of the University

of Puerto Rico. Support of the research in the Virgin Islands was providedby Federal Aid in Fish Restoration (Dingell-Johnson Project F-2-R of

the Virgin Islands), the National Science Foundation (G-5941) and the

National Park Service. The assistance of Herman E. Kumpf, James R.Chess, and John E. Randall in field work is gratefully acknowledged.

Thanks are also due Luis R. Almodovar and Harold J. Humm fordeterminations of the algae from Cittarium stomachs and to Peter W.Glynn and Germaine L. Warmke for reviewing the manuscript.

CLASSIFICATION AND DISTRIBUTION

The West Indian topshell was described as Turbo pica by Linnaeus in

1758. Gray (1842) in the 44th edition of his "Synopses of the contents ofthe British Museum" listed the generic name Livona with a brief descrip-

tion that was not diagnostic and which mentioned no species. In his 1843

edition of the "Synopses" Gray lists one species, aurea, under the genusLivona, describing it only as "peculiar for the light golden colour of the

pearl." In November 1847 he regarded pica as the type of the genus.

Cittarium Philippi (February, 1847) had already appeared with pica thesole species (literature reviewed by R. Tucker Abbott, by request);

therefore Livona would seem to be a synonym of Cittarium, as indicatedby Iredale (1913) who wrote, "A name that seems to need rejection is

FIGURE 1. Two views of an adult Cittarium pica from St. John, Virgin Islands.Length of shell 97 mm. Personal collection.


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426 Bulletin of Marine Science of the Gulf and Caribbean [14(3)

Livona. In 1840 it is a nomen nudum; in 1842 it is indeterminable; in

1843 it is associated with a shell which is certainly not the one selected as

the type in 1847." Rehder (1962), however, prefers to retain ivona.

Clench&

Abbott (1943) selected Linnaeus's reference to Gaultieri(1742: p1. 68, fig. B) as the type figure. They regarded the locality given

by Linnaeus, the Sea of Sardinia, as erroneous and designated Martinique

as the type locality (after Denys de Montfort, 1810).

Clench & Abbott have listed numerous Caribbean localities for the

species, and Warmke & Abbott (1961: map 7) have indicated a distri-

bution throughout the West Indies and the Central and South American

coast from upper Yucatan to Trinidad. Clench & Abbott have discussedthe occurrence of C. pica as a fossil in Florida and Bermuda (an attempt

to reintroduce it into Bermuda was not successful) and expressed theirbelief that the species died out from these two areas in comparatively

recent times.

HABITAT

Morris (1947) stated that Cittarium pica in the West Indies lives 0[1

weedy bottoms in moderately shallow water. If one interprets a weedy

bottom as seagrass or algae growing on a substratum of sand or other

sediment, then his concept of the habitat is erroneous. Cittarium pica lives

on rocky shores, and primarily those subjected to at least some wave action.

It occurs from slightly above the water level to several feet below, but is

usually within two feet of the surface. In general, the smaller shells are

found higher in the intertidal zone. Lewis (1960) cited the young as

occurring in the "pink zone" above mean low water at Barbados. Cittarium

does not occur in brackish areas, such as mangrove sloughs, but whether

this is related primarily to the difference in salinity, more turbid water or

lack of wave action is not known.

FIGURE 2. Juvenile Cittarium pica from Puerto Rico. Length of shell 5 mm.1MB 3179.


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Cittarium pica is one of the more abundant of mollusks in the WestIndies, and probably the most common large gastropod of the exposedrocky littoral region. As pointed out by Clench & Abbott (1943), however,

the larger topshells may be difficult to find in the vicinity of populousareas because of their heavy use as food.

The principal area of the present study was Europa Bay on the southern

shore of St. John (Randall, 1962: figs. 1 and 2). This is the westernmostof the three smaller embayments of Lameshur Bay. Unlike the other two,which have sandy beaches and little or no surf, the beach of Europa Bay

is entirely rocky (Fig. 3). Because it faces southeast it receives almostcontinuous small surf, usually less than 18 inches high. The bay supportsa large population of Cittarium pica, not only because of the suitable

habitat but also by being distant from the centers of population on theisland. Occasional fishermen collect "whelks" (as topshells are called in the

Virgin Islands) at even the remote sectOrs of St. John, therefore a largesign was posted indicating that a study of whelks was in progress andrequesting that none be removed from the bay.

FOOD HABITS

The stomach contents of 40 specimens of Cittarium pica from 25 to77 mm in length (measured from tip of spire to most distant edge of lip)

FIGURE 3. Europa Bay, St. John, Virgin Islands, the site of the growth study ofCittarium pica. View toward the southwest.


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TABLE 1

STOMACHCONTENTS OF Cittarium pica, BY VOLUME,FROM THE VIRGIN ISLANDSAND PUERTO RICO

Lameshur Europa Point Ram Head EuropaBay, Bay, Higuero Bay near Bay,

LOCALITY St. John, St. John, & R am ey R am H ead, St. John,V.1. V.I. Beach, St. John, V.1.

P.R. V.1.

NUM BE R OF SH ELLS 10 5 10 5 10-----

LENGTH OF SHELL (mm) 25-40 34-44 37-47 40-57 60-77

Blue-green algae 10% 17% 27% 50% 12%

Agmenellum quadruplicatum xA nacystis marina x x xCalothrix x xDichothrix xLyngbya majuscula x x x xMicrocoleus xOscil/atoria x x x XPhormidium xPlectonema nostocorum x X

Green algae 13% 14% 5% 9%

Cladophoropsis membranacea xUlvella lens (and other x x x x

coccoid greens)

Red algae 12% 19% 1% 1% 12%Amphiroa fragilissima xAsterocystis ramOsa xCeramium cruciatum xCoelothrix irregularis x x x xCorallina cubensis xGelidium corneum x x x x

Laurencia obtusa x x xPolysiphonia x x x

Brown algae 10% 12% 9% 12%Dictyota divaricata xPadina gymnospora x x xPocokiella variegata x

Ralfsia expansa x x xSphacelaria furcigera x

Diatoms 8% 10% 3% 12%

Organic detritus 10% 15% 20% 15% 18%

Sand, spicules and calcareous 37% 13% 49% 20% 25%d eb ris (pieces o f shell andfragments of calcareous algasuch as Halimeda)


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19641 H. Randaii: BlOlogy of Cittarium 429

were exammeo l Table 1). The data strongly suggest that this gastropod isherbivorous, although it does ingest some detrital material. Some calcareousfragments in topshells less than 40 mm in length have been as large as

6 mm. Cittarium pica does not seem to be particularly discriminating in itschoice of algal food. It feeds mainly on a variety of filamentous algae, often

blue-greens (Cyanophyta), and algae of relatively soft thalli. Coarse typesof algae such as Turbinaria and Sargassum, which are commonly founa in

its environment, were not detected in the stomachs. The physical limitations

imposed by the size of the snail and its radular structure (radular teeth

figured by Troschel, 1879: pI. 21, fig. 10) probably preclude its ingestionof algae which are both large and firm in texture.

The abundance of the West Indian topshell may be related in part to

having few competitors of large size for the algal food along the shore.The flora of the intertidal region on exposed rocky coasts is usually more

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TIME (1959-19601

FIGURE4. Growth of Cittarium pica in Europa Bay, St. John. First vertical linerepresents the range (3.0 to 9.9 mm) and the dot in the line the mean (5.8 mm)of 223 topshells which were notched, painted red, and released on March 10,1959. Additional'lines represent collections of the marked shells to July24, 1960.


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luxuriant than that found on hard substratum in deeper zones. Randall

(1961) has explained the paucity of algae on available surfaces in thedeeper zones by the presence of a variety of large herbivorous animals,

particularly fishes, which do not venture into the intertidal region or doso infrequently (the tidal fluctuation in the West Indies is not great).Observations at night revealed Cittarium pica more active than by day,

and more feeding seems to take place at night and early morning hours.More food material was found in the stomachs of specimens collected

early in the morning than later in the day.

GROWTH

On March 10, 1959, a collection of 223 juveniles from 3.0 to 9.9 mOl

in length (mean 5.8 mOl) was made in the middle of Europa Bay alongthe rocks shown in Figure 3. The little topshells were painted with brightred acetone-base paint, the lip of each notched with a file, and all releasedat the series of three large rocks in left center of the foreground of theillustration. Fourteen attempts were made to recover marked topshells at

intervals of one month or more, the last on July 24, 1960, when 12 shells

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TIME (1960)FIGURE 5. Growth of a group of small individuals of Cittarium pica. The firstvertical line represents 200 topshells ranging from 0.5 to 2.5 mm in length(mean 1.5 mm) which were painted red and released in Europa Bay, 51. Johnon January 15, 1960.


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averaging 35.7 mm were found (Fig. 4). Each time the topshells wererecovered, they were measured, repainted (usually more than half of thered paint was missing after a period of one month), notched again, and

re-released. The average growth rate of this group during the 161

h monthperiod is 1.81 mm per month.

Growth studies were initiated for three other groups in the same area

so that data could be obtained for a broader range of size. On January 15,1960, 200 small juveniles ranging from 0.5 to 2.5 mm in length and

averaging 1.5 mm were marked with red paint. Only 14 were found

during the first attempt at recovery on February 17, and mere traces ofthe red paint remained on these. Probably many marked shells were

overlooked because the paint had disappeared entirely. One hundred

eight-six more of the same size range and average were added to the14 recovered ones, and all were released together. Thereafter, at twoweek intervals, the little topshells were collected and painted, but they

were measured only at approximately monthly intervals up to the lastcollection on July 25 when 79 were found (Fig. 5). At this time theyhad attained an average length of 8.2 mm. Their average growth rate

during the 6 1/3 month period was 1.06 mm per month.

The growth of topshells of the same size group from progression ofmodes (see Fig. 1'0) approximates that of the marked juveniles.

The lower growth rate of the small topshells may be related to theirfeeding less frequently than larger individuals. The author noted that the

little shells were usually clustered in groups in narrow cracks high in theintertidal zone and did not appear to be feeding during the day. Glynn

A

FIGURE6. Marked topshells from Europa Bay, St. John. Released on August 4,1959, and recovered on January 17, 1960. Arrows show location of notches. A.Shell marked with a single sharp notch (see Fig. 7). Size at recovery 39.1 mm.B. Shell marked with two obtuse notches (see Fig. 8). Size at recovery 43.7 mm.


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432 Bulletin of Marine SciEnce of the Gulf and Caribbean [14(3)

(MS) has reported a similar slow initial growth for the intertidal gastropodsLittorina scutula and Tegula funebralis in Monterey Bay, California.

Two groups of larger topshells were collected on the southwest side of

Europa Bay where the rocks are larger and the habitat therefore moresuitable for the larger sheIls. They were marked and released on August4, 1959. The first group of 234 individuals, ranging from 30.0 to 39.6 mm

(mean 34.3 mm) were painted red, and a sharp V-shaped notch was filed

in the lip of each (the notch is visible in A of Fig. 6, a marked specimenwhich was collected 51/2 months after release). One hundred forty-four

topshells from 40.0 to 49.8 mm in length (mean 45.1 mm) constitutedthe second group. These were released in the same area after painting them

blue and grinding two broad notches with a grinding wheel in the lip of

each (B of Fig. 6). Subsequent attempts to recover the marked shells ofthese two groups were made at about six-month intervals. Additionaltopshells were painted, filed, and released with the recovered marked

individuals at each date of collection. These were carefully selected to fitwithin the range of those recovered and not alter the mean length. The

last collection of the 30-40 mm group was made on January 19, 1961,

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TIME (1959-1961)

FIGURE7. Growth of medium-sized Cittarium pica. The first vertical linerepresents 234 topshells ranging from 30.0 to 39.6 mm in length (mean 34.3mm) which were notched (Fig. 6 A), painted red, and released in EuropaBay, 81. John on August 4, 1959.


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H. Randall: Biology of Cittarium

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FIGURE8. Growth of Cittarium pica from one-half full size to more than three-fourths full size. The first vertical line represents 144 topshells ranging from40.0 to 49.8 mm in length (mean 45.1 mm) which were double-notched (Fig.6 B), painted blue, and released in Europa Bay, 81. John on August 4, 1959.


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when the topshells averaged 60.1 mm; the last recoveries of the 40-50 mmgroup were made on August 17, 1961, when the shells averaged 8'0 mm.

The growth rates of both groups over the 11/2 and 2 year periods were

nearly the same, 1.47 mm per month for the smaller group (Fig. 7) and1.43 mm per month for the larger (Fig. 8).

In order that growth of individual topshells might be determined,

experimental tagging of two groups of shells was carried out on January

18, 1960. The shells of each group were chosen to fall within the rangeof the two series of larger-sized marked topshells discussed above. Each

shell was tagged by placing a loop of vinyl plastic tubing (reinforced with60-pound test nylon in the center) through two holes drilled near theedge of the lip. The free ends of the tubing were clamped with a monel

band bearing a stamped number. Only one dead shell of the smaller groupwas seen again. Three were recovered from the larger group, two aftersix months and one after 19 months. The first two grew at a rate only

slightly more than half that of the untagged but marked shells. The largertagged one grew 1.25 mm per month, still noticeably less than that of the

size group to which it belonged. The tags seem to have had a deterring

effect on growth. It was noted shortly after the topshells were released that

the operculum tended to catch on the section of plastic tubing that passed

into the aperture. No further tagging was attempted.

If the growth rate remained constant at about 1.45 mm per month tothe maximum length of about 100 mm (as it very nearly did from a lengthof 34 to 80 mm), then it may be estimated that about 51/2 years would be

required for a topshell to grow from a juvenile of about 1 mm to the

large adult size.

On April 4, 1964, Europa Bay, St. John was briefly revisited, and ten

large topshells were collected from the area where marked shells had been

released. Upon cleaning these shells, a 93 mm one showed clearly two

broad notches, thus demonstrating it to be one of the 45.1 mm group re-leased on August 4, 1959. This shell (IMB 3384) is heavily eroded. The

black and white pattern is nearly obliterated over the entire shell which is

indicative of no recent growth. Assuming two years were required for it

to attain the 45 mm size at marking, this topshell is slightly more than 61/2

years old.

The length-weight relationship of Cittarium pica is given in Figure S I,

thus making possible a conversion of length data to approximate weight.

In some growth studies of gastropods, the lip growth is determined

instead of increase in shell length. In order to relate growth of the presentstudy to lip growth, 86 topshells in 13 size groups from 4 to 66 mm were

marked by filing one to three notches in the lip and released. After four

months 34 were recovered, and two measurements were taken of each, the

growth of the lip along the inner edge of the whorl and the length of the


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No

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FIGURE 9. Length-weight relationship of Cittarium pica. All specimens fromEuropa Bay, St. John, Virgin Islands.


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shell. The measurements were averaged for the different groups. Lip

growth was found to be 3.4 to 4 times greater than the overall growth of

the length of the shell. No obvious increase or decrease of this ratio was

evident from the smaller sizes to the larger.The average monthly sea temperatures in Lameshur Bay, St. John,during the period of the growth study ranged from 26.7 to 29.9C(Randall, 1961; Table 2).

MOVEMENTS

The marked individuals of Cittarium pica tended to remain in the area

of release. Had this not been the case, many more individuals would haveto be tagged to obtain so many recoveries. As would be expected, the

larger individuals made the more extensive movements.The 78 marked topshells which averaged 5.8 mm when released on

March 10, 1959, and which had an average of 9.5 mm when recovered

on May 31 (Fig. 4) were nearly all found in the immediate vicinity of thethree rocks of Europa Bay where originally released. Three, however, were

from 15 to 20 feet away. On October 20 one of this group was found 30

feet from the point of release. On April 13, 1960, half of the 30 which

were recovered were found on or beneath the three rocks; all of the rest

were within 15 feet of the rocks. On May 18 one was found 20 feet to

one side of the rocks and another 45 feet to the other side. On June 12,all that were recovered were within 20 feet of the point of release.

In anticipation of the greater movements of the larger marked shells,

the shore area was searched for several hundred feet to either side of the

point of release; however the longest movement was that of one double-notched, blue-painted individual which was found 150 feet in the westerly

direction between August 2, 1960, when it was released and its recovery

(at a length of 60 mm) on January 18, 1960. Two others of this group

had moved 80 feet from the area of release.

REPRODUCTION

The sexes of mature individuals of Cittarium pica are readily distinguish-

ed by the color of the gonads. The ovary is unmistakably green and the

testis creamy white. The smallest mature female detected among the many

samples examined measured 33.7 mm in length and the smallest male

32.4 m m .Some insight into the spawning activity of Cittarium pica was obtained

by sampling the young throughout the year (Fig. 10), beginning August 8,1959. For the period of one hour the author collected as many small

topshells under 10 mm in length as possible in Europa Bay. Because

conditions of surf and other possible factors could not be kept constant,

these small samples are not intended to be an accurate measure of relative


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abundance from month to month, but they do represent approximations.In addition to giving the sample size for each collection, the length of thcsmallest topshell is listed.

There was a large influx of young in January, indicated by the January16 sample of Figure 10. This pronounced mode may be followed from

month to month to the June sample. It suggests a brief and intensivespawning period for adults some weeks earlier; however, with theexception of November (July, a month with no sample), topshells smallerthan 4 mm were found in all months of the year. If we assume a growth

of only 1 mm per month, the 3.2 mm one collected on October 20 musthave come to the intertidal. as a new arrival from the plankton at a lengthof about 1 mm only two to three months earlier. Perhaps there is low-level

spawning over a large part of the year with a peak to account for the bigJanuary influx of young; or larval stages may have drifted in from otherareas where spawning is out of phase with that of St. John (although it isdifficult to designate such an area in view of the normal westerly set of

the current).

Although no further samples were taken beyond June 13, 1960, anabundance of small juveniles was again noticed the following January,

thus suggesting that the occurrence of a large number of young in January1960 was probably not unusual.

PREDATORS

The following few observations on the predators of Cittarium pica weremade. Much remains to be learned about these and other enemies of thetopshell.

On August 2, 1960, a 35-mm Purpura patula was found eating a 37-mmtopshell in Europa Bay, St. John. The Purpura was feeding on fresh tissue

between the operculum of the topshell and the rest of the foot, and theoperculum was nearly detached. The topshell was not drilled.

A number of shells of Cittarium pica were found, which had beendrilled, either empty or inhabited by hermit crabs, but no observations

were made in the field of the gastropod responsible for the drilling.

Possibly it is a species of Thais.

While searching for the large-sized marked topshells, one was found

in the arms of a small octopus whose body was inside its hole in the rocks.

The diameter of the topshell was so great that the octopus was unable tobring it into its hole (which it seemed to be trying to do). The topshell

was ultimately removed from the grasp of the octopus; it was still alive.The octopus was not captured. Gregory Bateson of the Communication

Research Institute at St. Thomas, Virgin Islands, reports (personalcommunication) that he uses live topshells to feed octopuses (Octopus

vulgaris and O. filosus) in aquaria. The method by which these octopuses


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FIGURE 10. One-hour collections of juvenile Cittarium pica less than 10 mm inlength from Europa Bay, St. John from August 8, 1959, to June 13, 1960.Space between abscissas of samples proportional to the number of days betweensamples.


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kill Cittarium is at present not known. It is clear that they do not drill

through the operculum as O. bimaculatus does in killing Tegula spp. on the

Pacific coast. George Hunt, who collects octopuses for the Communication

Research Institute, reports that empty shells of Cittarium pica are mostfrequently encountered in front of the dens of Octopus vulgaris in shallow

water. In deeper water, bivalves predominate. On several occasions

octopuses have been found carrying live topshells or holding live snails

in their dens.

Three fishes were found in St. John with the remains of Cittarium pica

in their stomachs. One, a porcupinefish (Diodon hystrix) 394 mm in

standard length, contained two topshells (the opercula measured 17 and

18 mm in greatest diameter) among the crushed gastropods, crabs, and

echinoids in its stomach. A 285-mm puddingwife (Halichoeres radiata)had eaten three Cittarium; the opercula ranged from 2.3 to 3.3 mm in

diameter. This wrasse probably crushed the small topshells with its

pharyngeal teeth. A rock hind (Epinephelus adscensionis), 375 mm in

standard length, contained the opercula of two topshells in its stomach.

The opercula measured 19 and 25 mm in d iameter, and there were no

pieces of shell or soft tissue with them. This grouper has no known

mechanism to crush a large Cittarium. Possibly it stole a meal from some

other fish, such as Diodon.

Warmke and Erdman (1963) have reported one shell of Cittarium pica

among the stomach contents of 56 bonefish (Albula vulpes) from Puerto

Rico. Since the bone fish does not normally enter the topshell's habitat, the

one fish may have ingested either an empty shell or a shell occupied by a

hermit crab.

Intact shells of Cittarium which still contained soft tissue, were

occasionally found at the shore, often well above the high tide line. Some

animal such as a crab or a b ird with a pointed feeding structure was

presumed to be responsible for these partially eaten topshells. Afterdiscussion with local people on St. John, the oystercatcher (Haemotopus

ostralegus) (nomenclature after Bond, 1956) became the chief suspect.

Permission was obtained from the National Park Service to conect this

bird. Two were shot from the intertidal area by Robert E. Schroeder. One

weighing 1V:zpounds contained the remains of seven Cittarium pica which,

judging from the diameter of the opercula, had been about 35 to 45 mm

in shell length. Only one small topshell fragment was present. The bird's

stomach also contained two small clams and one A straea americana imbri-

cata. The second bird, which weighed 1 pound 7 ounces, had eaten 11Cittarium pica (opercula from 5.5 to 11 mm in diameter), one 8-mm

Nodilittorina tuberculata, four 7- to 8-mm individuals of Littorina ziczac.

and one A straea americana with a 6-mm operculum. The shells of the

Nodilittorina and Littorina were entire.


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Several of the natives of St. John stated that they had witnessed theoystercatcher flying well above the rocks with Cittarium, dropping them

so they would break, and then flying down to eat the exposed soft parts.

This behavior was not observed by the author. It is well known for gulls.For example, the herring and ring-billed gulls were reported by Magalhaes

(1948) feeding upon Busycon, Area and Noetia in this manner in North

Carolina. This method is not mentioned by Dewar (1908, 1913) in hisarticles on the mode of feeding of the oystercatcher. He described moredirect methods whereby the bill was variously employed in thrusting,hammering, twisting and exerting leverage to capture and open the shellsof various pelecypods and gastropods.

COMMENSALS

Two organisms were found living in close aSSOCiatlonwith Cittarium

pica. The relationship for both appears to be one of commensalism. Thesmall limpet Acmaea leucopleura is often found on the underside of the

shell, and the crab Pinnotheres barbatus lives in the mantle cavity. Eighteen

of the crabs were found in a total of 203 adult topshells collected from

southern St. John from January to August, 1960. One of the shells contain-

ed two of the crabs; the other crabs were found singly in the shells.

SUMMARY

The West Indian topshell, Cittarium pica (Livona pica of many authors),

is widely used as food in the Caribbean region. The preferred habitat is

a rocky shore with some surf action. The juveniles live high in the inter-tidal zone and the large adults (up to 100 mm) may be found from a few

inches to two to three feet or more below low water.

The stomach contents of 40 topshells measuring 25 to 77 mm, from the

Virgin Islands and Puerto Rico, revealed the species to be herbivorous.Filamentous algae is the principal food. Twenty-four genera of algae

(discounting diatoms), were identified from the stomachs of which nine

are blue-greens. Large amounts of sand, calcareous debris and other

detritus are usually present.

The growth of Cittarium was determined by marking shells in four

different size groups at St. John, Virgin Islands. The smallest (an average

of 1.5 mm when marked) grew at a rate of slightly more than 1 mm per

month for a period of six months. A group which averaged 5.8 mm when

marked grew an average of 1.81 mm per month over a period of 161/2

months. The third group (initial mean length 34.3 mm) increased the

shell length at a rate of 1.47 mm per month for P/2 years, and the fourth

(mean length 45.1 mm) grew 1.43 mm per month over a two-year period.

One of the latter was recovered 4 years and 7 months after release. It


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H. Randall: Biology of Ciuarium 441

and was heavily eroded to the lip, thus indicating nomeasured 93 mm

recent growth.

The marked topshells showed little tendency to make extensive move-

ments. The greatest movement recorded for any shell less than 35 mm inlength was 45 feet. The longest migration of larger shells was that of a

60-mm individual which moved 150 feet from the point of release.A large influx of juvenile topshells of about 0.5 to 1 mm was observed

in St. John in January, 1960. No other obvious influx of young appearedduring the year, although topshells smaller than 4 mm were found innearly all months.

Purpura patula was found feeding upon a freshly dead Cittarium. Anoctopus was observed trying to pull a moderately large topshell into its

hole. The remains of Cittarium were found in the stomachs of three fishesand the oystercatcher (Haemotopus ostralegus).

The limpet Acmaea leucopleura is often seen adhering to the undersideof the shell of Cittarium, and the crab Pinnotheres barbatus is occasionallyfound in the mantle cavity.

1964]

SUMARIO

ESTUDIO DEL CRECTMIENTO Y OTROS ASPECTOS DE LA

BIOLOGIA DEL BURGAO, Cittarium pica (LINNAEUS)

El burgao (Cittarium pica-muchos autores aun usan Livona pica) se

utiliza como alimento en muchos lugares de la regi6n del Caribe. EIhabitat preferido par este molusco es el de ormas rocosas donde batenlas olas. Los ejemplares juveniles viven alto en la zona cotidal mientras que

los adultos (hasta de 100 mm) se encuentran desde algunas pulgadashasta dos, tres 0mas pies bajo el nivel de bajamar.

EI contenido estomacal de 40 burgaos obtenidos en las Islas Vfrgenesy Puerto Rico y cuyos tamanos oscilaban entre los 25 y 77 mm revela

que la especie es herbfvora, y que el alimento principal consiste de algasfiJamentosas. Sin contar las diatomeas, se identificaron 24 generos dealgas de las cuales nueve son azules. Generalmente se encuentran pre-

sentes grandes cantidades de partfculas ca1careas y detritos.EI crecimiento de Cittarium se determin6 marcando las conchas de cua-

tro grupos distintos seleccionados en cuanto a tamano y obtenidos enSt. John, Islas Vfrgenes. El grupo de los mas pequenos (con un prome-

dio de 1.5 mm al marcarse) creci6 a raz6n de poco mas de 1 mm por

mes durante un tiempo de seis meses. Otro grupo que inc1ufa ejempla-

res de un tamano medio de 5.8 mm al marcarse creci6 un promedio de1.81 mm por mes por un tiempo de 16th meses. El tercer grupo (largo

inicial medio de 34.3 mm) aument6 el tamano de la concha a raz6n de

1.47 mm por mes por un pedodo de Ith afios y el cuarto grupo (largo

inicial medio de 45.1 mm) crecio 1.43 mm por mes por un perfodo de


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mas de dos aiios. Uno de los ultimos fue recuperado 4 aiios y 7 meses

despues de su desprendimiento. Media 93 mm y estaba grandemente car-

comido hasta el labio, indicando asi que no habia crecimiento reciente.

Los burgaos que fueron marcados demostraron poca tendcncia a mo-verse de un sitio para otro. La mayor distancia recorrida que se pudo

observar para una concha menor de 35 mm de tamaiio fue 45 pies. El

recorrido mas largo efectuado por animales de conchas de mayor tamaiio

fue el de uno de 60 mm de largo de concha que se e ncontr6 a 150 pies

del punta don de se solt6.

En enero de 1960 se observ6 en S1. John una gran afluencia de burgaos

j6venes de tamaiios entre 0.5 mm y 1 mm. No se observ6 igual abundan-

cia de estados juveniles durante el aiio aunque siempre se conseguian

ejemplares mas pequeiios de 4 mm.EI gaster6podo Purpura patula fue encontrado alimentandosc de un

Cittarium recientemente muerto. Tambien se pudo observar a un pulpo

tratando de halar a un burgao de tamaiio moderado hasta su escondite.

Los restos de Cittarium fueron encontrados en el contenido estomacal

de tres pescados y del caracolero (Haemotopus ostralegus).

EI gaster6podo ("limpet") Acmaea leucopleura se observa a menudo

pegado a la parte de abajo de la concha de Cittarium; el cangrejo Pin no-

theres barbatus se encuentra ocasionalmente en la cavidad palia],

LITERA TURE CITED

BOND, J.1956. Check-list of birds of the West Indies. Fourth Edition. The Academy

of Natural Sciences, Philadelphia, Pennsylvania, ix + 214 pp., withsupplements.

CLENCH, W. J. AND R. T. ABBOTT1943. The genera Gaza and Livona In the western Atlantic. Johnsonia.

no. 12: 1-12,4 pIs.

DEWAR, J. M.1908. Notes on the oystercatcher (Haemotopus ostralegus). with reference

to its habit of feeding upon the mussel (Mytilus edulis). Zoologist.(4) 12: 201-212.

1913. Further observations on the feeding habits of the oystercatcher(Haemotopus ostralegus). Zoologist, (4) 17: 41-56.

GAUL TIERI, N.

1742. Index testarum conchyliorum quae in ejusdem museO adservantur etmethod ice distributa exhibentur. Caientani Albizzini, Florence. xxiv

+ 110 pIs.GLYNN, P. W.

MS. Community composItIon, structure, and interrelationships in themarine intertidal Endoc/adia muricata-Balanus glandula associationin Monterey Bay, California. (Submitted for publication to Beau-fortia. )


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GRAY, 1. E.1842. Synopses of the contents of the British Museum. 44th Edition.

G. Woodfall and Son, London, iv + 308 pp.1847. A list of the genera of recent MoIlusca, their synonym a and types.

Proc. zool. Soc. London, Pt. 15: 129-219.IREDALE, T.

1913. The collation of the moIluscan parts of the synopses of the contentsof the British Museum, 1838-1845. Proc. malac. Soc. London, 10(4): 294-309.

LEWIS, J. B.1960. The fauna of rocky shores of Barbados, West Indies. Canad. J. Zool.,

38: 391-435, 20 figs.

MAGALHAES, H.

1948. An ecological study of snails of the genus Busycon at Beaufort,North Carolina. Eco!' Monogr., 18 (3): 379-409, 61 figs.

MONTFORT, D. DE1810. Conchyliologie systematique, et classification mHhodique des CoquiIles.

Vol. 2. Coquilles univalves, non-c1oisonnees, ou uniloculaires. F.SchoeIl, Paris, 676 pp., 161 pis.

MORRIS, P. A.1947. A field guide to the sheIls. Houghton Mifflin Company, Boston, xvii

+ 190 pp., 40 pis.PHILIPPI, R. A.

1847. Versuch einer systematischen Eintheilung des Gesehlechtes Trochus.Zeitschr. fur Malakozoologie, 4 Jahrg.: 17-24.

RANDALL, J. E.1961. Overgrazing of algae by herbivorous marine fishes. Ecology, 42 (4):

812.1962. Tagging reef fishes in the Virgin Islands. Proc. Gulf and Carib. Fish.

Inst. (14th Annual Session): 201-241, 8 figs.

REHDER, H. A.1962. Contribuci6n al conocimiento de los moluscos marinos del Archi-

pielago de los Roques y la Orchila. Mem. Soc. Cienc. nat. La Salle,

22 (62): 116-138, 6 figs.TROSCHEL, F. H.

1879. Das Gebiss der Schneken. Vol. 2. Nicolaische Verlags-Buchhandlung.Berlin, vii + 409 pp., 32 pIs.

WARMKE, G. L. AND R. T. ABBOTT1961. Caribbean seashells. Livingston Publishing Company, Narberth,

Penna., x + 346 pp., 34 text-figs, 44 pis., 19 maps.WARMKE, G. L. AND D. S. ERDMAN

1963. Records of marine rnoIlusks eaten by bonefish in Puerto Rican waters.The Nautilus, 76 (4): 115-120, 2 figs.
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