Pacific Science (1989), vol. 43, no. 4 View metadata,© 1989 citationby University and similarof papersHawaii atPress. core.ac.ukAll rights reserved brought to you by CORE provided by ScholarSpace at University of Hawai'i at Manoa

Vertical Distribution of Mollusks on the Rocky Intertidal of Easter Island 1

CECILIA OSORIO AND VICTOR CANTUARIAS 2

ABSTRACT: Horizontal and vertical distribution ofmollusks was studied in the rocky intertidal of Easter Island (27°09' S,109°26' W) in January and again in September 1986. Organisms are zoned from the upper to the lower intertidal. In the upper horizon dominant species are Nodilittorina pyramidalis pascua, Rehde­ rella belyaevi, Nerita sp., and Planaxis akuana, together with crustaceans, deca­ pods and echinoderms. In the middle horizon dominant species are Plaxiphora mercatoris, Dendropoma sp., Antisabia sp., and Pilosabia sp. Mid-horizon pools support algae; the only relatively abundant coral, Porites lobata; numerous gastropods such as Stomatella and Euplica; crustaceans; and echinoderms. In the lowest horizon Cypraea caputdraconis and Echinometra insularis are dominant. The latter species is a rock borer that builds "pots" forming microhabitats shared with other organisms. Some specimens of Dendropoma, Pocillopora, and Echinostrephus were also found in this horizon. No great differences in distribu­ tion of organisms among the south, northeast, and northwest sectors of the island were distinguished in an index of similarity. Distribution patterns at Easter Island are comparable with those in other tropical areas where the same families and genera are found. At Easter Island the species are different because of the high degree ofendemism among the mollusks.

EASTER ISLAND, or Rapa Nui (lat. 27°09' S, temperatures fluctuate between 24°C in sum­ long. 109°26' W), a Chilean possession in the mer and 20°C in winter. The extreme tem­ southeast Pacific, is one of the most isolated peratures (maximum and minimum recorded islands in the Pacific Ocean. Its marine fauna temperatures) were 30.6°C (25 December 1964) is primarily derived from the Indo-West Pacific and 15.6°C (9 August 1979), according to rec­ (Rehder 1980, Ladd 1960, Ekman 1953), but ords kept from 1957 to 1978 by the Instituto because of its extreme isolation and other Hidrografico de la Armada de Chile (Chilean conditions typical of the area there is marked Navy Hydrographic Institute). Because of its endemism among the mollusks. Kohn and close relationship with the Pacific anticyclone Lloyd (1973) found that 67-88% ofthe corals, (Hauser 1986), the island has rains throughout crustaceans, gastropods, and fish at Easter Is­ the year. land are also present elsewhere in the Indo­ The human population of Easter Island is Pacific, and most of the remainder are en­ now about 2300. In prehistoric times the is­ demic. Rehder (1980) considers about 42% of land was overpopulated, reaching on average the mollusks endemic. Schilder (fide Rehder from 10,000 to 15,000 inhabitants. The shore­ 1980) recognized Easter Island as an indepen­ line perimeter of 57 km (Boonen 1897) is con­ dent zoogeographical province and designated tinuously searched by the islanders for food it the "Rapanuian" or Easter Island Province. and raw materials for handicrafts. Easter Island has a temperate to subtropi­ Most of the scientific literature concern­ cal climate. Monthly average ocean surface ing Easter Island deals with taxonomic and biogeographic problems of different animal groups, e.g., Fuentes (1914), Wells (1972), and 1 Manuscript accepted 12 December 1988. Cea and Di Salvo (1982)-corals; Garth 2 Departamento de Ciencias Ecol6gicas, Facu1tad de Ciencias, Universidad de Chile, Casilla 653, Santiago, (I973)-crabs; Kohn and Lloyd (1973)­ Chile. polychaetes; Kohn (l978a), Pinochet (1980), 302 Intertidal Distribution of Mollusks-OSORIO AND CANTUARIAS 303 and Rehder (1980)-mollusks; Fell (1974) and Akahanga, Hanga Nui, Vinapu, and Anakena, Codoceo (1974)-echinoderms; Randall and which are areas ofbasalt shoreline; and Vaihu McCosker (1975), and Randall (1976)-fishes. and Ovahe, which are beaches. Castilla and Rozbaczylo (1987) published a Mollusks were obtained in transects per­ bibliographic review of the littoral marine pendicular to the coastline at Hanga Roa and invertebrates. Santelices and Abbott (1988) Vaihu during low tides. Collections were made discussed algal zonation and biogeography. on exposed and protected rocks, in crevices, Relatively little work has been done on and under rocks and algae. Three biotic zones ecology and the distribution of organisms on were established parallel to the shoreline, each Easter Island. The aim ofthis work is to char­ delimited by numerically and macroscopically acterize the vertical and horizontal distribu­ dominant species used as biological indicators. tion of mollusks in the rocky intertidal, to Sorensen's (1948) index of similarity was compare species composition of intertidal used to compare mollusk populations in the mollusks on different sectors of the coastline, different sectors studied. Species collected and to compare the distribution and composi­ among rocks and shells found in the work area tion ofthe Easter Island intertidal fauna with were included in the calculations. that in temperate and tropical areas.

RESULTS MATERIALS AND METHODS Distribution Collections were made on Easter Island from 9 to 16 January and from 11 to 18 Sep­ Sixty-four mollusk species were identified tember 1986. Average tidal heights during (Table 1). Fourteen (22%) ofthe species were the study periods were 0.82 m and 0.27 m in common to five to seven of the seven sectors January and 0.59 and 0.13 m in September. sampled; 23 (36%) were found in a single area. Seven sections of the rocky intertidal were Thus, 14 species were restricted to Anakena, selected for transects (Figure 1): Hanga Roa, four to Hanga Roa, three to Hanga Nui, and

La Perouse '"

Hanga• NUl

-+- 27°tO'5 Og" 2<5wo

FIGURE 1. Easter Island, showing study areas. 304 PACIFIC SCIENCE, Volume 43, October 1989

TABLE I

MOLLUSK SPECIES RECORDED IN THE ROCKY INTERTIDAL OF EASTER ISLAND"

SPECIES VI AN HN OV HR VA AH

Plaxiphora mercatoris Lelaup* x x x x Emarginula velascoi Rehder x x Diadora granifera Pease x x x x x Euchelus alarconi Rehder* x x x x x Stomatella esperanzae Rehder* x x x Nerita lirellata Rehder* x x x x x morio (Sowerby) x x x x x x x Nodilittorina pyramidalis pascua Rosewater x x x x x x x Rissoina turricula englerti Rehder x x x x x Merelina crassula Rehder x x x Zebina tridentata crassilabrum (Garrett)* x x x Assiminea vulgaris (Webster) x x x Heliacus codoceoae Rehder* x Dendropoma sp. x x x x x Caecum sp. x Cerithidium actinium Rehder x Triphora sp. x Planaxis akuana Rehder* x x x x x x x fasciatus Pease x x Melanella cumingi (A. Adams) x x Balcis aciculata (Pease) x x Vitreolina wareni Rehder* x Epitonium pyramis Tinker x Hemiliostraca bahamondei Rehder* x Antisabia foliacea (Quay and Gaimard) x x x x x imbricata (Gould) x x x x x Pilosabia trigona (Gmelin) x x x Fossarus cumingii A. Adams x x x Strombus maculatus Sawerby x x Trivirostra pellucidula (Reeve) x Intertidal Distribution of Mollusks-OSORio AND CANTUARIAS 305

TABLE I (continued)

SPECIES VI AN HN OV HR VA AH

Cypraea caputdraconis Melvi11* x x x x x eng/erti Summers and Burgess* x Moru/a praecipua Rehder* x Neothais nesiotes Iredale x x x x x x x Pascu/a citrica (DaB)* x x Zafrona pusi//a Pease* x x Eup/ica /oisae Rehder x x x x Seminella ornata (Pease)* x x Nodochi/a pascua (Hertlein)* x x x x Caducifer decapitata eng/erti Hertlein* x x x x x Mitra flavocingu/ata Lamy* x x Granu/a pascuana Rehder* x Lienardia exi/irata Rehder* x x x Conus mi/iaris pascuensis Rehder* x x x x x x Acuminia venosa (Hinds) x Egente/aria sty/ata (Hinds) x Retusa pusi//a (pease) x Smaragdinella ca/ycu/ata (Broderip and Sowerby) x Siphonaria pascua Rehder* x x x x x Wi//iamia radiata Rehder x Me/ampus pascus Odhner* x x x x x x Trimuscu/us odhneri (Hubendick) x Rangitotoa sp.* x Ap/ysia sp. x x x Nudibranchia sp. x Modio/us matris Pilsbry x Septifer bryanae (Pilsbry) x Barbatia nuttingi (DaB) x x Codakia bella (Conrad) x x x x Ch/amys pasca DaB* x 306 PACIFIC SCIENCE, Volume 43, October 1989

TABLE I (continued)

SPECIES VI AN HN OV HR VA AH

Lasaea hawaiensis Dall x x x Semele australis (Sowerby) x x x Tellina mauiaDall x Mactridae sp. x

"Abbreviations of sectors selected for transects: VI, Vinapu; AN, Anakena; HN, Hanga Nui; OV, Ovahe; HR, Hanga Roa; VA, Vaihu; AH, Akahanga. • Indicates endemic species.

OJ. N • 5500 position, littoral pools, and patches of coral, 30 are the most similar of the areas sampled.

40 Zonation 50 From the high-tide line to the low-tide line,

60 organisms are arranged in horizons or zones .--C parallel to the coastline. These horizons are 70 characterized by certain macrospecies that are dominant in number in each of the horizons, 80 but that actually form a biological continuum

90 from the high-tide line to the low-tide line. Three typical horizons are described. 100 The dominant species in the upper horizon :s Cl q \1 q were the gastropod Nodilittorina pyramidalis " '" q ~ ~ ~ ir q pascua and the barnacle Rehderella belyaevi " "~ ::!'" '"~ "~ ~" "~ q q " "s: 0 Zevina and Kurshakova. Nodilittorina (mean length, 11.9 mm) reached an abundance of FIGURE 2. Dendrograph showing indices of similarity for the molluscan fauna of the seven sampled sectors on 304 specimens per square meter in certain sites. Easter Island. The other dominant component, the balanid Rehderella, covered an average of26% of the two to Vaihu. Eighteen species representing rock surface. At the lower reaches ofthe upper other phyla were found with the mollusks. horizon, the nerites Nerita morio and N. lirelata The Sorensen similarity index shows that increased in abundance both on and under five sectors exhibited more than 50% simi­ rocks. As many as 52 specimens per square larity (Figure 2). Greatest similarity was be­ meter were counted. In the lower part of the tween Hanga Nui and Vaihu (67%), and upper horizon, under rocks, small specimens Hanga Nui, Vaihu and Hanga Roa, and Aka­ (mean length, 5.9 mm) of Planaxis akuana hanga (62-63%). In contrast, Vinapu and (724 specimens per square meter) were found, Ovahe showed less similarity with the above together with Nerita, the crab Cyclograpsus areas (34%) and both showed a low index longipes Stimpson, and the brittle star (35%). Ophiocoma dentata Muller and Troschel. An The results obtained from the transects of average of 84 specimens of varying sizes of vertical distribution of the mollusks of the Ophiocoma were counted per square meter. rocky intertidal are shown in Figure 3. Hanga The brittle star preys on the gastropod Roa and Vaihu, both areas with gradual Planaxis. slopes, basaltic volcanic rock of similar com- In the middle horizon the dominant orga- .... (t= a-. 0. e:. t:1 00' 5". g- ::t, o

Plonoltl$ = HIGH TIDE---__ LOW TIDE ....,o Nodlf,"or",oNOtj,/,"ormo PIOltiphOraPla.'pharo S,phonor,o £UpIiCOEupliea ~ 4 @ 2­ Loso.o o e-en N.ri,o Conus :>;" (m) (\ t N_OiloN~.". en 1.0 Q ~ CypraeaCypro.o I ~ £uc"'u' 'J. Stoma,.flo o/~ ,, EEC~/ro " •- t' /~ io 0.5 , e r_ »z r •I o

O.OL----.f----7'<-:-----,~-_T_+-_t_--+-<' / I 0,0 L " 7 _, ,.~ )(I.I• {;.,/ l .:r. Holothurio .•.. i1JJ. Ftlfurk/tM . !' . Comllmoceoe Lobophoro ~ ~'" ~~ C\~'C~ -'. - ':~'; POCi/ioporaPoCilfoporo '" ~~:,....

~"~-I-' ~.'.,~.'." StypopodiUftlStypopoeJiUftl ~ 'i7/ff''~ '-' 11 Sorgosum L.p'ogropsus HllJim.do Adil'lorio OphiocomoOpltiocomo 3""'i-.,

FIGURE 3. Vertical distribution of mollusks and associated organisms in the rocky intertidal of Easter Island.

w o -..I 308 PACIFIC SCIENCE, Volume 43, October 1989 nisms were the chiton Plaxiphora and the coral DISCUSSION AND CONCLUSIONS Porites, and mollusks were less conspicuous than the algae Ulva lactuca, Cladophora sp., The distribution ofthe 64 identified species and Gelidium sp. The only live-collected bi­ of gastropods in the intertidal of Easter Is­ valve, Lasaea, was found on fronds of land, and especially those of Nodilittorina, Gelidium. The gastropod Dendropoma sp. Cypraea, Plaxiphora, and Planaxis, support was found cemented to the substrate. Plaxi­ Rehder's (1980) conclusions on distribution. phora was relatively abundant in crevices, Thirty-nine percent of the intertidal mollusks and a maximum number of 24 specimens per recorded are endemic, a figure close to that of square meter was recorded. The errant poly­ Rehder's (1980) 42% for overall mollusk en­ chaete Eurythoe complanata (pallas) and crabs demism. The high proportion ofmollusks en­ such as Petrolisthes coccineus (Owen) and demic to the intertidal on Easter Island also xanthids were found under the rocks. supports Vermeij's (1972) hypothesis that high The most conspicuous component of the intertidal organisms are specifically adapted pools in this zone was the coral Porites to the morphological and physiological re­ lobata. Small fish and eels (Moringuidae and quirements of the physical regime in which Muraenidae) were seen under the coral heads. they live. Neritids and littorinids, for example, There was also a great abundance of algae are particularly adapted to high temperature such as Sargassum skottsbergii, Lobophora and stresses ofdesiccation. . variegata, and Halimeda opuntia in the pools. Generally speaking, the pattern ofdistribu­ Specimens ofthe gastropods Conus, Euchelus, tion of the mollusks sampled is relatively Euplica, Neothais, Nodochila, Stomatella, and homogeneous on the south, northeast, and Strombus, and, occasionally, individuals of northwest sectors ofthe island. The relatively Aplysia sp. (up to 800 g) were found among low similarity index (35%) for two sectors of the algae. Another important biological com­ the island, Ovahe and Vinapu, compared with ponent ofthis horizon was the sea cucumbers an average index of 63% for the other five Holothuria difficilis and H. cinerascens, which areas, may be influenced by the topographic were found on the bottom of the pools at characteristics of the sites, or can perhaps be 2 mean densities of 701m • Other organisms explained in terms of habitat (Kay 1979). attached to the substrate included Actinaria Ovahe is a beach where rocks alternate with and the hipponicid gastropods Antisabia and sandy areas, and the water in the intertidal has Pilosabia. a high sediment content that may hinder set­ At the lowest horizon, the most typical tlement on rocks. Vinapu is a narrow beach macrocomponent was the sea urchin Echino­ with smooth, rounded edges. The physical metra insularis Clark. This echinoid is a rock characteristics of both sectors are such that borer and builds marine "pots." Mean den­ only a limited number of organisms can sur­ sities of 17 specimens per square meter were vive in these areas, where, as suggested by recorded. Fifty-four percent of the "pots" Eleftheriou and Nicholson (1975), physical contained other organisms such as pagurid disturbance and severe hydrodynamic condi­ crabs, nerites, polychaetes, turbellarians, small tions provoke sediment instability. specimens ofPlaxiphora, and Neothais. In the The rocky intertidal is well known for zona­ remaining 46% of the cavities, only Echino­ tion, the arrangement ofcommunities parallel metra was found. The gastropod Cypraea to the coastline (Menge and Lubchenko 1981). caputdraconis was collected in cavities. Crus­ Easter Island is no exception, although zona­ tose algae were found on rocks in neigh­ tion is less obvious in some sectors of the boring areas. When density ofechinoids is low island than in others, as has been reported for 2 (less than 101m ), algal cover increases. A few Taboguilla, Panama (Lubchenko et al. 1984). specimens of Dendropoma, Pocillopora, and The occurrence of some mollusks can be Echinostrephus sp., another rock borer, were explained by the occurrence ofcertain types of also recorded in this horizon. habitat such as substrate or the occurrence of Intertidal Distribution of Mollusks-OsORIO AND CANTUARIAS 309

algae. Some organisms are found only on ba­ trast to an average of20 in the tropical Ameri­ salt shores ('fermeij 1971). Others are found can intertidal areas and an average oDO in the only where algae are abundant, as is Aplysia, intertidal areas of the Hawaiian Islands and the stomach contents of which include inter­ the northern Marianas. This finding is con­ tidal algae such as Hypnea, Laurencia, and sistent with that of Santelices and Abbott Sphacelaria (M. E. Ramirez, pers. comm.). (1988), who recorded relatively few species of The occurrence ofcorals in the intertidal is algae in the intertidal. It is also noteworthy remarkable. Scarce and isolated, corals do not that members of the family Mytilidae do not form reefs around the island, probably be­ form conspicuous mats as they do in Hawaii cause seawater temperatures are below the and Pernambuco (Kay 1979, Vermeij and minimum tolerated by reef-building corals Porter 1971). (Wells 1972), and perhaps also because of the Although the population ofEaster lsland is isolation ofthe islands, the limited number of relatively small, the island has a long history habitats (Randall and McCosker 1975), and of human habitation, and the effects of that the rugged tectonic features and problematic history are apparent. Cowries, for example, oceanographic climate (Di Salvo 1985). are virtually limited to the lowest horizon of Several food webs have been identified in the intertidal, but the occurrence oftwo speci­ the rocky intertidal at Easter Island. Poly­ mens in the middle horizon suggests that the chaete, sipunculid, and gastropod food webs distribution of Cypraea caputdraconis is, or were recorded by Kohn (1978b), who identi­ has been, wider than it is today. fied Mitra flavocingulata preying on sipun­ culids; Neothais nesiotes feeding on Rehderella ACKNOWLEDGMENTS belyaevi, Antisabia imbricata, and Dendropoma sp.; and Pisania decapitata englerti preying on We thank professors N. Bahamonde, D. polychaetes. Planaxis, with abundances typi­ Soto, and E. Valenzuela for valuable sugges­ cal of those reported by Houbrick (1987), is tions and help with revision ofthe manuscript; preyed on by large numbers of Ophiocoma. It L. Di Salvo for references; M. E. Ramirez, N. is worth noting that Conus miliaris at Easter Rozbaczyl0, and M. Codoceo for identifying Island (Kohn 1978a) has a microhabitat dis­ algae, polychaetes, and holothurians, respec­ tribution in the intertidal ofthe western Indo­ tively; L. Gonzalez, E. Villouta, A. San Mar­ Pacific similar to that at Easter Island, reach­ tin, T. Pakarati, and A. Rirorroco for help in ing the same depths. Most specimens are found the field; C. Fernadez for diagrams; M. Bustos associated with algae, although Conus feeds for technical assistance; and M. Cariceo for on polychaetes. typing. This work was supported financially Comparison of the organisms present at by the Departamento Tecnico de Investiga­ Easter Island and those of rocky intertidal cion, Universidad de Chile. areas in the tropical Pacific and on the coasts of the Americas is shown in Table 2. As has LITERATURE CITED been pointed out by Vermeij (1971, 1973), Vermeij et al. (1983), and Kay (1979), the BOONEN, J. 1897. Isla de RapaNui 0 de Pascua. same families and genera of mollusks, bar­ Ensayo sobre Geografia Militar de Chile. nacles, echinoids, and corals occur in tropical Torno II. Imprenta Cervantes. waters around the world, but the species are CASTILLA, J. c., and N. ROZBACZYLO. 1987. different. At Easter Island, the species are Invertebrados marinos de Isla de Pascua y noticeably different because of the high per­ Sala y Gomez. Pages 191-215 in J. C. Cas­ centage of endemism among the mollusks. tilla, ed. Islas Oce{micas Chilenas. Ed. The fauna of Easter Island also differs in that Univ. Catolica de Chile. fewer species of mollusks occur in intertidal CEA, E. A., and L. H. DI SALVO. 1982. Mass than are recorded elsewhere: 14 molluscan expulsion of Zooxanthellae by Easter Is­ species were recorded at Easter Island in con- land corals. Pac. Sci. 36: 61-63. w o TABLE 2 -

MOLLUSCAN SPECIES COMPOSITION OF TIlETHE INTERTIDAL OF EASTER ISLAND AND SOME TROPICAL AMERICAN AREAS AND PACIFIC ISLANDS GROUPS

MARGARITA ISLAND, TABOGUILLA ISLAND, FLORIDA KEYS VENEZUELA PANAMA NORTIlERNNORTHERN MARIANA (Stephenson and (Rodriguez 1959, (Lubchenko et al. HAWHAWAIIANAllAN ISLANDS ISLANDS EASTER ISLAND Stephenson 1950) 1967) 1984) (Kay 1977, 1979) (Vermeij(Verrneij et al. 1983)

Upper Horizon Nodilittorina Nodilittorina Nodilittorina pyramidalis pascua hawaiensis pyramidalis millegrana Littorina Littorina Littorina Littorina ziczac ziczac aspera pintado modesta Nerita Nerita Nerita Nerita Nerita Nerita lirellata peloronta peloronta funiculata picea albicilla morio versicolor versicolor scabricosta guamensis insculpta maxima plicata Theodoxus 'i:l'"C neglectus >(J Tectarius Tectarius .... "l:j tuberculatus muricatus .... Planaxis Planaxis Planaxis Planaxis (J niger t:fl akuana lineatus labiosa niger (J zonatus .... trI Echininus Z nodulosus (J Acanthina .trI brevidentata -< 0 Melampus a' flavus coffeus ~ .j::o. Detracia .w bulloides 0 ('") Rehderella Tetraclita ..... 0 belyaevi sp. (j(j' (I)(p Onchidium ..,.... verraculatum -\0 00- \0 TABLE 2 (continued) ...... ,S. MARGARITA ISLAND, TABOGUILLA ISLAND, '" 5: FLORIDA KEYS VENEZUELA PANAMA NORTHERN MARIANA e:. (Stephenson and (Rodriguez 1959, (Lubchenko et al. HAWAllAN ISLANDS ISLANDS EASTER ISLAND Stephenson 1950) 1967) 1984) (Kay 1977, 1979) (Vermeij et al. 1983) ~ OJ>.... :::!. 0" Middle Horizon c:: Diodora g. listeri ::3 Fissurella Fissurella 0....., nimbosa virescens ~ Raliotis 2- varia a- OJ> Cellana Cellana ~ exarata toreuma OJ> Patella I 0on flexuosa 0 Notacmaea sp. 5 > Stomatella Z planulata 0 () Nerita > tessellata Z ""l versicolor c::: Dendropoma ~ spp. on> Serpulorbis variabilis Antisabia Antisabia Joliacea Joliacea imbricata imbricata Pilosabia Pilosabia trigona pilosus Neothais Neothais nesiotes harpa Thais Thais Thais Thais rusticus melones intermedia armigera intermedia Purpura Purpura aperta persica Morula Morula granulata biconica w uva granulata uva - w.... TABLE 2 (continued) -Ntv

MARGARITA ISLAND, TABOGUILLATABOGIDLLA ISLAND, FLORIDA KEYS VENEZUELA PANAMA NORTHERN MARIANA (Stephenson and (Rodriguez 1959, (Lubchenko et al. HAWAllAN ISLANDS ISLANDS EASTER ISLAND Stephenson 1950) 1967) 1984) (Kay 1977, 1979) (Vermeij et al. 1983)

Drupa Drupa morum morum ricina ricina rubusidaeus Cantharus tinctus Onchidium floridianumfioridianum Smaragdinella Smaragdinella calyculataca/ycu/ata calyculataca/ycu/ata Siphonaria Siphonaria Siphonaria Siphonaria Siphonaria pascua alternataa/ternata gigas normalis sirius pectinata cf. guamensis MelampusMe/ampus pascua Mytilus Perna Brachidontes Brachidontes Mytilus Perna Brachidontes Brachidontes "'C"C exustus perna semilaevis crebristriatus (")>() ModiolaModio/a .... "rj"Ij capax -.... Isognomon Ostrea -(")() alalaa/ata spp. tIJtZl (")() chemnitziana Ceratozona ...... tTlt'I1 sp. Z PlaxiphoraP/axiphora AcanthopleuraAcanthop/eura Chiton Acanthochiton Acanthochiton (")() mercatoria granulatagranu/ata stokesi armata gemmata .tIl.t'I1 viridis -<<: ChthamalusChthama/us 0 2" stellatus [S Tetraclita (1)<11 ~ squamosa .w.w""'- Lower Horizon 0 Diodora Diodora Diodora Diodora Diodora 0... 0 granifera antillarum sp. granifera granifera cr" Fissurella Fissurella ..,(1)<11 .... nimbosa longifissa/ongifissa \0\0 -00 virescens \0 ...... ::s ....(l) TABLE 2 (continued) 5: e:. MARGARITA ISLAND, TABOGlnLLAISLAND, 0 ~. FLORIDA KEYS VENEZUELA PANAMA NORTHERN MARIANA ::!. (Stephenson and (Rodriguez 1959, (Lubchenko et ai. HAWAIIAN ISLANDS ISLANDS cr"c:: EASTER ISLAND Stephenson 1950) 1967) 1984) (Kay 1977, 1979) (Verrneij et ai. 1983) o. 0::s Cellana 0 sandwicensis ...., Tegula ~ 2- fasciata 2" Cypraea Strombus Cypraea Cypraea '";>;" caputdraconis gigas caputserpentis caputserpentis '" Petaloconchus I keenae 0 0 Thais Thais '"~ haemastoma melones 0 A canthina > brevidentata 8 Siphonaria (J > maura Z.., Arca Chama Chama C barbatia echinata iostoma > ~ umbonata Isognomon Isognomon > incisum incisum en Ischnochiton Chiton Tonicia limaciformis tuberculatus forbesi Porites Porites Porites lobata spp. sp. Poci/lopora Millepora Acropora Poci/lopora Poci/lopora Poci/lopora sp. sp. sp. damicornis meandrina meandrina Meandrina sp. Balanus inexpectatus Chthamalus sp. Echinometra Echinometra Echinometra Echinometra Echinometra Echinometra insularis lucunter lucunter vanbranti mathaei sp. w..... w 314 PACIFIC SCIENCE, Volume 43, October 1989

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