SURVEY OF THE SIPUNCULA OF THE CORAL AND BEACH- ROCK COMMUNITIES OF THE CARIBBEAN SEA MARY E. RICE Department of Invertebrate Zoology National Museum of Natural History Smithsonian Institution Washington, D. C. ABSTRACT Sipunculans inhabiting beachrock and coralline limestone have been collected from 36 stations in the Caribbean Sea and Straits of Florida. Eleven species have been identified; they belong to the genera Aspidosiphon, Lichacrosiplion, Paraspidosiphon, Phascolosoma and Themiste. The habitats are described, the species listed, and relative abundance and distri- bution of each species reviewed. Some general observations are reported on the biology of the most common species, including feeding patterns and possible mechanisms for formation of the burrows. INTRODUCTION While gathering material for a systematic and developmental study of the Sipuncula of the Caribbean Sea, I have collected numerous sipunculans from bur- rows in coralline limestone and beachrock at stations situated throughout the Carib- bean Sea and Straits of Florida. In the course of these collections, observations have been made on various aspects of the biologj' of the rock-boring species, including their relative abundance, distribution, tj'pes of substrata inhabited (Rice 1969), structure of burrows, and in a few instances, feeding behavior. Eleven species, con- stituting 97 percent of those collected from calcareous substrata, will be considered here. They are, in order of abundance in the collection, as follows: Phascolosoma perhicens Baird, 1868; Phascolosoma antillarum Grube and Oersted 1859, Litha- crosiphon gurjanovae Murina 1967, Aspidosiphon brockt Augener 1903, Paraspido- siphon steenstrupi (Diesing 1859), Paraspidosiphon fischeri (Ten Broeke 1925), Para- ? spidosiphon spinososcutatus (Fischer 1922a), Themiste alutacea (Grube 1859), Para- S spidosiphon speciosus (Gerould 1913), Phascolosoma varians Keferstein 1865, and ^ Paraspidosiphon klunzingeri (Selenka and B?low 1883). All of these species, with the '" exception of Phascolosoma varians, were always found in burrows in calcareous ?= rock. Phascolosoma varians occurred in burrows only when the rock was soft and ^ friable; otherwise it was found in gravel, under rocks, or in crevices. Of these 11 ^ species, only Paraspidosiphon klunzingeri has not been reported previously in the 2 35 ? 36 MARY F,. RICE Caribbean Sea. The remaining three percent of the specimens are unidentified species of Paraspidosiphon, Phascolosoma and Golfingia. In tlie past, three notable studies have been concerned specifically with the Sipuncula of the Caribbean, They are those of Fischer (1922a) on collections from Barbados and St. Thomas, Ten Broeke (1925) on collections from Cura?ao, and Murina (1967) on collections from Cuba. Other records of specimens from this area are encountered in various reports on collections of museums or expeditions (see Keferstein 1867, Gerould 1913, Fischer 1922?). This report, covering a broader area of the Caribbean than previous accounts, provides additional information on the distribution patterns of the 11 rock-dwelling species mentioned above and also reviews the available information on several aspects of their biology, including their rock-boring activities. Taxonomic problems, mentioned briefly here, will be treated in detail in a later treatise on systematics. MATERIALS AND METHODS Sipunculans were collected at 36 stations in the Straits of Florida and Carib- bean Sea. The distribution and number of stations were as follows: Florida, 7; Bi- mini, 2; Jamaica, 2; Puerto Rico, 9; Barbados, 5; Venezuela, 8; Cura?ao, 3. Loca- tions of the stations are indicated on the map (Figure 1) and in Table 1. The total number of recorded specimens was 3,423. All specimens were taken from calcareous rock, usually in the intertidal or shallow subtidal waters. At six stations samples were tallen at greater depths (8 to 75 feet) by dredging or diving. Habitats at the various stations included calcified mangrove reefs, fossil coral reefs (Fig. 2), recent coralline limestone, calcarenite boulders, beachrock (Fig. 3), coral rubble and dead portions of living coral colonies (Table 1). Texture of the substrata varied from the relatively soft and friable calcified mangrove reef to the hard and dense coral rock. Composition and characteristics of the substrata at several of these stations have been described in a previous paper (Rice 1969). Animals were extracted from their burrows by fracture of the rock with geo- logy pick and chisel and careful exposure of the burrows. Some specimens were maintained alive for developmental studies whereas others were preserved in 70 percent alcohol or in 10 percent neutral formalin or in a combination of the two. Prior to preservation, animals were relaxed in 10 percent alcohol in sea water. During the process of extraction from the rock many of the animals were unavoidably in- jured and those damaged beyond recognition were discarded. Table 1 lists the station localities, station numbers used in these collections, habitat characteristics, and the number of each species collected at each station. In a few instances (indicated by +) the presence of a species was recorded but areous re Figure 1. Map of the Caribbean Sea and adjacent waters showing locations of stations at which sipunculans were collected from calcar spheres (1). (The 5 stations at Cubagua, Venezuela are marked by a single sphere, due to limited space.) In the enlarged insets the more prcci signaled by the station number (see Table 1). I SURVEY OF THE SIPUNCULA OF THE CARIBBEAN SEA 37 specimens were not saved and exact numbers were not available. The figures listed are interpreted only as an indication of relative abundance. Species density was determined at only one station, Cabo Rojo, Puerto Rico (see Results). RESULTS Phascolosoma perlucens (Fig. 4) (formerly known as Phascolosoma dentigerum, see Rice and Stephen 1970) was the most abundant species in the calcareous rock, constituting at least 46 percent of the specimens collected. Widely distributed, it occurred in Florida, Bimini, Jamaica, Puerto Rico, Barbados, Venezuela and Cu- ra?ao (Table 1). It was found at 94 percent of the stations in all types of rock from the exceedingly friable calcified mangrove reef and highly eroded limestone boul- ders to the hard, compact recent and fossil coral rock. Although most abundant in intertidal habitats, it was also present at depths of 75 feet. Usually Phascolosoma perlucens appeared in the same rock with one or more other species of sipunculans and commonly it was the dominant species. Reflecting the shape and presumably the activity of the animals, the burrows of this species were found to be long, narrow and frequently winding with a single opening to the surface of the rock. With its anterior end always directed toward the opening the animal was tightly ensconsed within the walls of the burrow and when exposed or removed from the rock the body expanded to exceed considerably the diameter of the burrow. Animals maintained within rocks in the laboratory were observed to extend introvert frequently to the exterior, then retract it. When spe- cimens were placed in artificially constructed burrows covered by glass slides, peri- staltic movements of the body were noted (Rice 1969). In the laboratory, once re- moved from their burrows, the sipunculans crawled into cavities or crevices of va- rious calcareous substrata provided for them, but they were never observed to form new burrows. Observations on animals in intact burrows in the laboratory have shown that feeding is accomplished by extending the introvert at great distances from the mouth of the burrow over the surface of the rock, while accumulating small particles of detritus on the tentacles and hooks. The particles are engulfed when the introvert is retracted. Examination of gut contents of a few specimens immediately after collec- tion from the field have revealed fragments of rock, unidentified fine particulate matter, algal strands, diatoms, foraminifera and a few small crustacean molts. Previously this species has been recorded from onl}' three localities in the Caribbean Sea: Jamaica (Baird 1868), Barbados (Fischer 1922?), and St, Barth?l?my (Fischer \922h). Ten Broeke (1925) described a similar but smaller species from Caracas Bay, Cura?ao which she named Phascolosoma microdenngerum. Specimens 38 MARY E. RICE Localities and habitats of rock-dwelling sipunculans in collections from the Caribbean Sea and surrounding tvaters. o JO m c Locality Habitat 4 FLORIDA Key Biscaync (NE shore) calcified mangrove reef, intertida! 5 Soldier Key fossil coralline limestone, intertidal 54 Bache Shoal recent coralline limestone boulders, 8 feet 55 Triumph Reef Acropora rubble, 25?30 feet 45 Key Largo (SE shore, 5 miles N of Tavernier) fossil coralline limestone, intertidal 3 Key Largo (SE shore, Harry Harris Park) fossil coralline limestone, intertidal 51 Pigeon Key fossil coralline limestone, intertidal and subtidal 32 BIMINI North Bimini (NW shore) calcarenite platform, intertida! 33 North Bimini (NE lagoon) calcarenite boulders, subtidal 30 JAMAICA Drunkenmfln's Cay (near Port Royal) coralline limestone boulders, intertidal and subtidal 31 Southeast Cay coralline limestone boulders, intertidal and subtidal 13 PUERTO RICO Punta de Cerro Gordo (N coast, near San Juan) calcarenite outcrop on exposed sandy beach, intertidal 15 Aquadilla (W coast) sandstone conglomerate along exposed shore (between layers), intertidal 17 Boquer?n Bay (W coast) pitted coralline limestone boulders, subtidal 21 Cabo Rojo (SW coast) pitted calcarenite boulders, intertidal 8 Arrecife Enrique (SW coast) recent coralline limestone intertidal and subtidal U Mangrove Island (near La Parguero) Porites rubble, intertidal 14 Cayo Turrumote (SW coast) recent coralline limestone boulders, intertida! and subtidal 18 Outer deep reef (6 miles S La Parguera) highly pitted coralline limestone boulders, 75 feet SURVEY OF THE SIPUNCULA OF THE CARIBBEAN SEA 39 TABLE I It 1 a s II 1 Is >3 ofl 1 S'a 1 is. t! 1 II II ?il 1 1 a, Is <5s- i II Il S s ??~ Ci. Je -1 H. a . si 1 Q a ?S v. 8g !i 171 23 2 1 ___i 3 1 1 5 ! 1 202 26 1 1 27 (+) 2 1 1 2 1 1 3 1 9 2 3 '! 9 2 26' "^Y\ 4 6 79 3 1 1 112 (++) 1 2 12 2 3 1 1 Ts 12 1 ( + ) 2 9 1 2 30 4 22 1 28 5 3 9 3 8 ( + ) 3 3 34 6 56 3 2 3 70 18 50 1 69 ! 13 9 (+) 18 16 3 I 1 3 51 1 67 276 1 1 8 1 353 36 < 2 1 35 2 4 1 81 1 1 6 ' ' 1 1 2 10 5 ^ 5 19 1 5 2j 2 41 1 ' -- ? 6 4 1 i ' j 12 40 MARY E. RICE 11 a B Locality Habitat 19 Arrecife Margarita (near La Parguera) highly pitted coralline limestone boulders, 75 feet 27 BARBADOS Six Aden's Bay (W shore) beachrock, coarse-grained biocalcarenite, intertidal 47 Speightstown (W shore) beachrock, coarse-grained biocalcarenite, intertidal 29 St. Lawrence Gap (S shore) calcarenite boulders, intertidal 28 Bath (E shore) highly pitted coralline limestone boulders, subtidal 48 Holetown (W coast, 1/2 mile from shore) pitted coralline limestone boulders, 50?75 feet 40 VENEZUELA Isla Margarita, Boca Chica (SW shore) calcarenite rock along exposed shore, intertidal 41 Isla Margarita, Playa Caribe (NE shore) Porites rubble, subtidal 42 Isla Cubagua, Punta el Medio coralline limestone boulders, 12 feet 35 Isla Cubagua, Pimta Charagato calcarenite rock along shore, intertidal 38 Isla Cubagua, Ens. de Charagato calcarenite rock along shore, intertidal 43 Isla Cubagua, Punta el Ecuador calcarenite boulders, intertidal and subtidal 44 Isla Cubagua, Punta Brazil calcarenite boulders, intertidal and subtidal 34 Los Totumos (near Higuerote) calcarenite boulders 22 CURA?AO Piscadera Baai (S shore near mouth of bay) coralline limestone boulders, intertidal 25 South shore, near Lagoen Jan Tiel coralline limestone platform, intertidal 24 Spaansche Water (S shore) Porites rubble, intertidal Total Number of Recorded Specimens Percent of Total Recorded Specimens Subtidal refers to shallow subtidal from depths of 1 to 3 feet. ( + ) indicates that the presence of the species was recorded but specimens were not preserved; exact rvumbers are not available. Presence of the species was noted as either a few ( + ) or many (++) specimens. SURVEY OF THE SIPUNCULA OF THE CARIBBEAN SEA 41 Ph as co lo so ma pe rlu ce m Ph as co lo so ma a m iU ar um il 3? 1 ?S- 1 t! 1 li S S is ?i i II 1 -S II 1 If a,? 1 1 id ?. a es S- T3 ? la f2& 1 2 4 1 1 8 686 18 32 1 8 7 751 24 3 1 ? 27 ! 21 28 5 7 1 1 63 12 8 6 12 9 1 2 50 16 4 19 6 3 1 49 12 12 5 37 2 18 3 65 1 2 3 305 1 77 6 2 391 38 (+) 3 5 46 6 4 8 18 (+) 15 1 16 (+) (++) 1 (+) 1 17 1 3 4 25 18 37 1 1 57 7 15 412 30 90 45 6 5 55 1 666 1568 45.8 531 15.5 498 14.6 253 7.4 161 4.7 160 4.7 51 1.5 50 1.5 19 0.6 17 0.5 6 0.2 69 2.0 27 0.8 13 0.4 3,423 42 MARY 11. RICL; in my collections from Spaansche Water, Cura?ao, in close proximity to the type locality of P. microdentigerum, could not be distinguished from P. perlucens found at other localities throughout the Caribbean region. Phascolosoma perlucens is widely distributed in tropical waters. On the Pacific Coast of North America it has been found in the Gulf of California and in the Bay of Panama (Fisher 1952). It has been reported most often in the Indo-Pacific (see Selenl), St. Barth?l?my (Fischer 1922^), Barbados (Fischer 1922a, Selenka, de Man and B?low 1883, Gerould 1913), Jamaica (Baird 1868), Cuba, Colombia, Venezuela and Key West, Florida (Gerould 1913). In the Atlantic it has been found at Surinam and Brazil and in the Pacific at Baja California, Costa Rica, Panama and Chile, Hawaii and the Riukiu Islands (see Fischer 1952 for review of distribution). Phascolosoma antinaru7n is absent in the Indian Ocean and the Eastern Atlantic. Lithacrosiphon gurjanovae (Fig. 6) was co?ecxe? i\t st??ons in Bimini, Puerto Rico, Barbados, Jamaica, Cura?ao and in the offshore coral reef of South Florida. It was absent from stations along the coast of Venezuela, including the islands of Margarita and Cubagua as well as the intertidal waters of the Florida Keys. Although the third most abundant species in the collections, comprising nearly 15 percent of the specimens collected, it was usually found in only small numbers. Its relative abundance in the total collections is explained by its great density at one station, Spaansche Water in Cura?ao. Here in an intertidal bed oiPorites it was the dominant species in the coral rubble and dead basal portions of living coral colonies. Other species of sipunculans occurring in the same habitat were, in order of abundance, Paraspidosiphon steenstrupi, Paraspidosiphon fischen, Aspidosiphcn brocki, Phascolo- soma antillarum, Phascolosoma perlucens, Paraspidosiphon spinososcutatus and Para- spidosiphon speciosus. There were, in addition, many unidentified Paraspidosiphon (Table 1). The burrows of Lithacrosiphon were short, straight and rounded posteriorly ; even when exceedingly numerous as in the Parit?s rubble, ?\ey did not intersect (Fig. 7). The anterior shield, a cone-shaped structure with cuticular covering, was always directed toward the mouth of the burrow, apparently serving as an oper- culum. Frequently anterior cones were overgrown with coralline algae or, in some instances, with filamentous algae. Lithacrosiphon gurjanovae occurred in intertidal waters down to depths of 75 feet. It inhabited not only Poritcs rubble, as at Cura?ao, but also, at other stations, it was found in recent coralline limestone boulders, pitted and eroded coralline limestone, and beachrock. The following four species of Lithacrosiphon have been reported by other authors from the Caribbean; L. alticonum Ten Broeke 1925, L. kukenthali Fischer 1932a, L. odherni Fischer 1922?, L. poritides Ten Broeke 1925. All of the specimens noted in this paper have been interpreted to be one species, corresponding most closely to Murina's description (Murina 1967a) of L. gurjanovae. This species has been reported previously only from Cuba and is presumably endemic to the Ca- ribbean. Specimens of Lithacrosiphon in my collections from Spaansche Water, Cu - ra?ao differed from Ten Brooke's descriptions of L. alticonum and L. poritides from 44 MARY E. RICE Caracas Bay, Cura?ao, although the two localities are adjacent to one another. The hooks of the introvert of L. alticonmn were described by Ten Broeke as one- -pointed on the anterior introvert and two-pointed posteriorly whereas in L. port- tides all of the hooks were described as one-pointed. In specimens from Spaansche Water I found the anterior hooks to be two-pointed and the posterior hooks one- -pointed. These discrepancies point to the necessity for a review of the genus Litha- crosiphon and a re-examination of Ten Broeke's tj'pe specimens. Aspidosiphon brockt and Paraspidosiphon fischeri (Fig. 8) are both small species of approximately the same size, attaining a length of about 10 mm. Found at 25 percent of the stations, A. brockt comprised seven percent of the specimens collected and P. fischeri, occurring at 33 percent of the stations, comprised nearly five percent of the total specimens. Although there was some overlap in distribution, A. brocki occurred with greatest frequency in the northern Caribbean and Straits of Florida, whereas P. fischeri was found most often and in greatest numbers in the southern Caribbean in islands off the coast of Venezuela. Both species were present in Cu- ra?ao, but only P. fischeri was found at Cubagua, Venezuela and Barbados, and only A. brocki in Puerto Rico, Jamaica and the littoral waters of the Florida Keys. Aspi- dosiphon brocki occurred only in substrata of dense, compact coralline limestone or coral rubble, whereas P. fischeri, while found in similar substrates, also occurred in the coarse-grained biocalcarenite (beachrock) at Barbados and in the coarse conglo- merate rock at Cubagua, Venezuela. The burrows of these small species were always located near the surface of the rock. Aspidosiphon brocki was first described by Augener in 1903 from Indonesia (Amboina, Polo Edam) and not recorded again until Murina reported it from Cuba in 1967. Paraspidosiphon fischeri, first described from Cura?ao in 1925 by Ten Broeke, is endemic to the Caribbean. Murina (1967a, 6) described a subspecies, Paraspi- dosiphon fischeri cubanus, from Cuba. Paraspidosiphon steenstrupi (Fig. 9) was present at stations in Bimini, Puerto Rico, Barbados, Jamaica, Cubagua (Venezuela) and Cura?ao. It was notably absent only in the littoral waters of the Florida Keys. Rarely occurring in great numbers, it constituted only five percent of the total specimens collected. This species inha- bited rocks of varying texture from the coarse-grained biocalcarenite of the beach- rock of Barbados to the dense coralline limestone found at many stations throughout the Caribbean (Table I). The characteristic anterior shield of P. steenstrupi, sur- rounded by a thickened rim, was often covered by calcareous deposits and occasion- ally with filamentous algal growth. Because of its position at the mouth of the burrow, the anterior shield has been assumed to serve as an opercular device. The posterior shield of this species was found to vary in shape from flattened to rounded to pointed, depending on the state of contraction at the time of preservation. Other records of P. steenstrupi in the Caribbean are from Barbados (Fischer 1922a), St. Barth?l?my, St. Thomas (Fischer 1922i!>), Cura?ao (Ten Broeke 1925) Figure 2, Fossil coralline limestone, intertidal. Key Largo, Florida (Station 3). Figure 3. licachrock, coarse-grained biocalcarenite. Six Men's Bay, Barbados (Station 27). Figure 4. Phascolosoma perlucens. Figure 5. Phascolosoma anlillarum. Figure 6. Lithacrosiphon gurjanovae Figure 7. Burrows (indicated by arrows) of Lithacrosiphon gurjanovae in Porites rubble from Spaansche Water, Cura?ao (Station 24). Rubble was broken open to expose burrows and animals removed Figure 8. Left, Paraspidosiphon fischeri. Right, Aspidosiphon brocki. Figure 9. Paraspidosiphon sleenslrupi. Figure 10. Paraspidosiphon spinososcuiaws. Figure II. Themiste ahnacea. Figure 12. Paraspidosiphon spcciosus. The scale equals 2 mm on all figures. ? SURVEY OF THE SIPUNCULA OF THE CARIBBEAN SEA 45 and Cuba (Murina 1967a). With the exception of the Eastern Pacific this species has been reported in tropical waters around the world and has been considered as one of the commonest sipunculans in the Indo-Pacific (Shipley 1903, Sato 1939). The remaining five species altogether make up less than five percent of the total specimens collected. Paraspidosiphon spinososcutatus (Fig. 10), accounting for 1.5 percent of the total, was found in both the southern and northern Caribbean, including stations at Cura?ao, southwestern Puerto Rico, southeastern Jamaica, and Bimini. The substrata inhabited by this species were coral rubble and dense coralline limestone boulders from intertidal or shallow subtidal waters. Paraspido- siphon spinososcutatus was fii'st described by Fischer (1922a) from Bai-bados and St. Thomas and later by Murina (1967a, b) from Cuba and the Gulf of Mexico. It is apparently endemic to the Caribbean Sea and nearby waters. Themiste alutacea (Fig. 11), never found in great ntunbers, comprised 1.5 percent of the specimens collected. Its habitats varied from the soft and friable calcified mangrove reef to the hard and compact coral rubble or coralline limestone. Other localities in the Caribbean from which T. alutacea has been reported in the past are St. Croix (Grube and Oersted 1859) and St. Barth?l?my (Fischer 1922&). In Florida it has been found at Cedar Keys, Key West and Dry Tortugas (Gerould 1913). The northernmost record in the Atlantic is Cape Hatteras (Gerould 1913) and the southernmost at Rio de Janeiro, Brazil (Selenka, de Man and B?low 1883). Paraspidosiphon speciosus (Fig. 12) and Paraspidosiphon klunzingeri together comprised 0.7 percent of the total specimens collected. Similar in gross external morphology, the two species are distinguished on dissection by the rectal caecum which is highly lobulated in P. klunzingeri, but simple in P. speciosus. There is also a striking difference in the shape of the hooks of the introvert. The hooks of P. klun- zingeri have a blunter terminal point, a relatively broader base and are not as strongly bent as those of P. speciosus. Paraspidosiphon speciosus was collected at offshore reefs of southern Florida and southwestern Puerto Rico and along the coasts of eastern Barbados and southern Cura?ao. Paraspidosiphon klunzingeri was found at the same stations in Puerto Rico and eastern Barbados and at two additional stations in western and southern Barbados. At Cura?ao P. speciosus occurred in intertidal Porites rubble in associa- tion with large numbers of other sipunculans (Table 1). At other stations the rocks in which these two species were found were highly pitted dead coral boulders with varying degrees of cementation and relatively low densities of sipunculan fauna. Paraspidosiphon speciosus was first described by Gerould (1913) from Key West Florida, Cuba and Brazil. Later Fischer (1922a) reported its occurrence at St. Thomas. The distribution of P. klunzingeri, on the other hand, is widespread, although centered in the Indo-Pacific. It has been reported from the Red Sea (Se- lenka, de Man and B?low 1883, Wesenberg-Lund 1957) to the Western Pacific (Shipley 1898) and the Great Barrier Reef, Australia (Edmonds 1956). In the At- 46 MARY E. RICE lantic it has been found at Liberia and the Cape Verde Islands (Wesenberg-Lund 1959). Phascolosoma varians constituted .0.4 percent of the total specimens collected. It was collected at stations in Florida, Puerto Rico and Jamaica. It occurred burrow- ed within the rock at only one station at Key Biscayne, Florida where- the rocky substratum consisted of a calcified mangrove reef of soft texture and loosely cement- ed structure. At stations near Poit Royal, Jamaica this species was found in the crevices of dead coral boulders ; at stations along the southwestern coast of Puerto Rico near- La Parguera, it occurred sometimes in rock crevices or buried in a sub- stratum of coarse sand and coral rubble or wedged between the branches of Po- rites rubble. Phascolosoma varians has been reported from the Bahamas (Shipley 1890) and from Florida at Key West, Cape Florida, Key Vacas, Tortugas, Bird Key (Keferstein 1867, Gerould 1913, Fischer 1922a), as well as from numerous other localities throughout the Caribbean: St. Thomas (Keferstein 1865, Fischer 1922a), St. Croix (Grube and Oersted 1859, Keferstein 1865), Barbados, Jamaica (Fischer 1922a), St. Barth?l?my, Haiti (Fischer 1922?), and Cura?ao (Ten Broeke 1925). Although centered in the West Indies, it has been found at Bermuda and the Ascen- sion Islands (Gerould 1913) and in the Pacific at Rotuma and Funafuti (Shipley 1898) and Formosa (Sato 1939). DISCUSSION Sipunculans are common inhabitants of the coral and beachrock communities throughout the Caribbean and nearby waters. Often occurring in great densities, they dwell in burrows, presumably of their own formation, within a variety of cal- careous substrata. The substrata varied widely in texture and hardness. Usually several species inhabited a single rock and dominance of a particular species showed no apparent association with type of substratum. Most species were found in both hard and soft calcareous substrata, but Aspidosiphon hrocki, Paraspidosiphon speciosus and Paraspidosiphon klunzingeri were collected only from dense coralline limestone and Phascolosoma varians was burrowed only within soft calcareous rocks. As demon- strated in an earlier paper (Rice 1969), Phascolosoma perlucens, Phascolosoma antil- larum, Lithacrosiphon gurjanovae and Paraspidosiphon steenstrupi all inhabit rocks of both friable and compact textures, containing calcite as well as aragonite. The greatest diversity of species in these collections was in the intertidal Pontes rubble and dead basal portions of living Porites colonies at Spaansche Water, Cura?ao (Table 1). Although the rock-boring sipunculans reported here were found at all depths at which collections were made (intertidal to 75 feet), they occurred with greatest SURVEY OV THE SIPUNCULA OF THE CARIBBEAN SEA 4? abundance and diversity in intertidal waters. There was no specific correlation with depth in the range studied and with two exceptions all species collected in deeper waters also occurred intertidally. Two species, Paraspidosiphon spinososcutatus and Phascolosoma varians, were found only in intertidal or shallow subtidal waters j however, these same species have been reported by previous authors from deeper waters: 40 and approximately 30 meters, respectively (Murina 19675, Fischer 19226). Of the 11 species of rock-dwelling sipunculans listed in this report, the fol- lowing three are endemic to the Caribbean and surrounding waters : Lithacrosiphon gurjanovae, Paraspidosiphon fischeri and Paraspidosiphon spinososcutatus. Two other species, Themiste alutacea and Paraspidosiphon speciosus, are restricted to the Carib- bean adjacent Atlantic coastline; both occur as far south as Brazil and the former has been recorded as far north as Cape Hatteras, North Carolina. The remaining six species have a wide distribution in tropical waters, all having been reported from the Pacific Ocean and some from the Indian Ocean as well. In looking at reproductive patterns for possible factors influencing distribu- tion, we find that Themiste abitacea, with a restricted distribution, has a short-lived lecithotrophic pelagic larval stage (Rice, elsewhere in this Symposium). On the other hand, the three species of Phascolosoma (P. perlucens, P. antillarum and P. va- rians), with relatively wide distributions, all have long-lived planl