Budding and Fusion in the Scleractinian Coral <I>Scolymia Cubensis</I>

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BULLETIN OF MARINE SCIENCE, 42(1): 145-149, 1988

BUDDING AND FUSION IN THE SCLERACTINIAN CORAL SCOLYMIA CUBENSIS (MILNE EDWARDS AND HAIME) FROM BERMUDA

Alan Logan

The scleractinan coral genus Scolymia Haime, which ranges from the Miocene to the Recent, is presently represented in the Indo-Pacific faunal province by two species (Veron and Pichon, 1980) and in the Caribbean faunal province (and its outposts in Bermuda and Brazil) by three species, one of which is the smooth disk coral S. cubensis (Milne Edwards and Haime). The taxonomy of the genus has been discussed by Wells (1964) and Veron and Pichon (1980), and the taxonomy and ethology of S. cubensis and its closely-related congener S. lacera (Pallas) by Wells (1971) and Lang (1971). Zlatarski (1982) has considered all three previously-described Caribbean-Atlantic species of Scolymia (including S. wellsii Laborel from Brazil) to be sub-species orforma of S. lacera, based on examination oflarge numbers of specimens from Cuba. Other authors, such as Cairns (1982), still follow Wells and Lang (op. cit.) in distinguishing S. lacera from S. cubensis, mainly on the basis of ethology, septal development and dentition, as well as polyp size and color. On the basis of these criteria, all specimens of Scolymia so far found in Bermuda appear to belong to S. cubensis. S. cubensis is relatively common on steeply-inclined surfaces in shaded habitats on rim, main terrace and fore-reef slope reefs around the Bermuda platform from depths of 6-62 m (Fricke and Meischner, 1985). The species is zooxanthellate but non-constructional and ahermatypic (sensu Schuhmacher and Zibrowius, 1985). It is usually solitary, with a patellate, turbinate or, more rarely, a cylindrical corallum, thus exhibiting the monostomadaeal condition with a solitary monocentric corallite (Fig. IA). However, it is not uncommon to find di- or even tricentric corallites, developing by intratentacular budding, with lamellar linkage, sometimes from a very early age (Fig. IB). Less common are examples of apparent extratentacular budding at the periphery oflarge corallites (Fig. 1C-D). Both types of asexual reproduction, with both lamellar and trabecular linkages, were observed in S. cf. vitiensis Bruggeman from the Great Barrier Reef by Veron and Pichon (1980), prompting them to synonymize Parascolymia Wells with Scolymia. In a pioneer ethological study of S. lacera and S. cubensis from Jamaican reefs, Lang (1971, p. 957) noted that: "Sometimes a larval S. cubensis settles beside another S. cubensis. When this happens, the adjacent polypal tissues of the two corals fuse, and their skeletons become joined by a common calcarous deposit." Assuming that Lang had indeed observed fusion rather than budding, then the possibility of tissue and skeletal conjunction of two sexually-reproducing (and therefore presumably genetically-distinct) individuals was in conflict with later studies by Hildemann and his co-workers (summarized in Logan, 1985). Their basic hypothesis was that fusion of tissue and skeleton should occur only in isografts between genetically-identical (isogeneic) individuals, while rejection should

145 146 BULLETIN OF MARINE SCIENCE, VOL. 42, NO. I, 1988 result from natural or experimental allograft pairings of genetically-distinct (allogeneic) individuals. This "allograft rejection rule" has become widely accepted (Jokiel et aI., 1983) until very recently, when exceptions began to be noticed in colonial species (Resing and Ayre, 1985; Heyward and Stoddart, 1985; Willis and Ayre, 1985) and in experimental pairings of the solitary S. cubensis from widely- separated localities in Bermuda by Logan (1985). In the latter case, however, the nagging doubt remained that the 40-day test period was too short, and that initial fusion might eventually give way to rejection, especially in such clearly allogeneic individuals. To test this possibility field experiments were initiated in August 1985 to span a 12-month period of contact between individuals of S. cubensis.

METHODS

Mature specimens of S. cubensis were collected from rim reefs at a depth of 8 m near the prominent navigational beacon at Kitchen Shoals (32°26'N, 64°37'W) and North-East Breakers (32°29'N, 64°41'W) at the edge of the Bermuda platform and separated by a distance of about 8 km. Six replicate pairs from the same immediate area at Kitchen Shoals and six replicate pairs from both localities were size- matched and then cemented, in contact, to limestone blocks at the test site at Kitchen Shoals, by the method described in Logan (1985), and left from 19 August 1985 until II August 1986. All specimens were retrieved for laboratory study at the end of this period and preserved in Bouin's solution.

OBSERVATIONS Although there was 50% mortality from unknown causes, enough specimens survived to indicate that rejection of tissue never occurred in any pairing. Only three pairs from the same area survived; one showing tissue and para theca fusion (Fig. 1K), the other two compatibility (i.e., absence of tissue damage but no fusion). Similarly the three surviving pairs from both localities showed a single case of tissue and para theca fusion (Fig. 1L) and two examples of compatibility without fusion, in spite of the fact that each member of the pair was originally collected from localities 8 km apart.

DISCUSSION The results of these experiments support earlier studies (Lang, 1971; Logan, 1985) on S. cubensis and suggest that, at least in this species, the self-recognition mechanism is much less sensitive than in some of the Indo-Pacific corals studied by Hildemann and his co-workers and cannot be viewed as a precise indicator of genetic identity. This premise is based on the assumption that this species, like other solitary coral species studied (Fadlallah and Pearse, 1982a; 1982b) repro- duces sexually, either by planulation or broadcast spawning, although at least one colonial coral species (Pocillopora damicornis) has recently been shown to be capable of brooding asexually- as well as sexually-produced planulae (Stoddart, 1983). Abnormal genetic uniformity in the species might be another possible

Figure I. Scolymia cubensis. All specimens from rim reefs, Bermuda (see text). A. Monocentric form. R Tricentric form (intratentacular budding), C-D. Dicentric form (extratentacular budding?), calical and basal views. E-F. Two coralla resulting from separate larval settlement, side and calical views. G-H. Mature corallum fused to two juveniles at periphery, resulting from separate larval settlement, shown by individual bases, calical and basal views. I-J. Septal and parathecal fusion of two originally separate coralla, as shown by individual bases, calical and side views. K. Enlargement of zone offused tissue between experimental specimens, Kitchen Shoals. L. Fusion of tissue between experimental specimens, Kitchen Shoals (left) and North-East Breakers (right), NOTES 147 148 BULLETIN OF MARINE SCIENCE, VOL. 42, NO. I, 1988 explanation for this compatibility, stressing the need for electrophoretic and re- productive ecology studies on S. cubensis. Naturally-occurring examples where two individuals of S. cubensis with quite separate bases have settled close to one another (Fig. lE-F), as Lang described from Jamaica, and have fused along their common boundary (Fig. 1G-J) are not uncommon. Similar conjunctions have been described in both solitary and colonial corals and usually ascribed to aggregating behavior in larvae (von Koch, 1892; 1914; Lacaze-Duthiers, 1899; Duerden, 1902; Boschma, 1953; Best, 1970; Zibrowius, 1980). While a functional histocompatibility system resulting in allogeneic rejection may be lacking in newly-settled larvae of many coral species (Hidaka, 1985), it is clear that species such as S. cubensis do not develop a sophisticated intraspecific immuno-recognition system even in adult stages (Lo- gan, 1985; this study). Whatever the reason for this compatibility, such fused examples of separate monostomadaea1 coralla simulate di- or even tristomadaeal coralla. This phe- nomenon, if it occurs in fossil forms, may lead to truly solitary species being erroneously regarded as partly colonial, an important consideration when growth form is being used as a taxonomic character (Duerden, 1902).

ACKNOWLEDGMENTS

This study was supported by Operating Grant A4331 from the Natural Sciences and Engineering Research Council of Canada to the author. I thank N. Logan and B. Collington for diving assistance. This paper is contribution number 1117 of the Bermuda Biological Station for Research, which provided logistical support.

LITERATURE CITED

Best, M. B. 1970. Etude systematique et ecologique des Madreporaires de la region de Banyuls-sur- Mer (Pyrenees orientales). Vie et Milieu, 20(2A): 296-326. Boschma, H. 1953. On specimens of the coral genus Tubastraea, with notes on phenomena of fission. Stud. Fauna Curacao, IV(18): 109-119. Cairns, S. D. 1982. Stony corals (Cnidaria: Hydrozoa, Scleractinia) of Carrie Bow Cay, Belize. Pages 271-302 in K. Riitz]er and I. G. Macintyre, eds. The Atlantic barrier reef ecosystem at Carrie Bow Cay, Belize. 1. Structure and Communities. Smithsonian Contributions to the Marine Sci- ences 12. Duerden, J. E. ]902. Aggregated colonies in madreporarian corals. Amer. Nat. 36: 461-471. Fadlallah, Y. H. and J. S. Pearse. 1982a. Sexual reproduction in solitary corals: overlapping oogenic and brooding cycles, and benthic planu]as in Balanophyllia elegans. Mar. BioI. 71: 223-231. -- and --. ]982b. Sexual reproduction in solitary corals: synchronous gametogenesis and broadcast spawning in Paracyathus stearnsii. Mar. BioI. 71: 233-239. Fricke, H. and D. Mieschner. 1985. Depth limits of Bermudian scleractinian corals: a submersible survey. Mar. BioI. 88: 175-187. Heyward, A. J. and J. A. Stoddart. 1985. Genetic structure of two species of Montipora on a patch reef: conflicting results from electrophoresis and histocompatibility. Mar. BioI. 75: 117-121. Hidaka, M. 1985. Tissue compatability between colonies and between newly settled larvae of Po- cillopora damicornia. Coral Reefs 4: 111-116. Jokiel, P. L., W. H. Hildemann and C. H. Bigger. 1983. Clonal population structure of two sympatric species of the reef coral Montipora. Bull. Mar. Sci. 33: 181-187. Koch, G. von. 1892. K.1einere Mittheilungen iiber Anthozoen. 8. Aggregirte Ko]onien von Bala- nophyllia verrucaria Aut. Morph. Jahrb. 18: 376-382. --. 1914. K.1einere Mittheilungen iiber Korallen. 12. Aggregierte Kolonien von Caryophyllia cyathus (Lamarck). Morph. Jahrb. 48: 149-155. Lacaze-Duthiers, H. de. 1899. Les Caryophyllies de Port-Vendres. Arch. Zool. Exp. Gen. 7: 529- 562. Lang, J. C. 1971. Interspecific aggression by scleractinian corals. 1. The rediscovery of Scolymia cubensis (Milne Edwards and Haime). Bull. Mar. Sci. 21: 952-959. Logan, A. 1985. Intraspecific immunological responses in five species of corals from Bermuda. Pages 63-68 in Proc. Fifth Inter. Coral Reef Congress, Tahiti, 6. NOTES 149

Resing, J. M. and D. J. Ayre. 1985. The usefulness of the tissue grafting bioassay as an indicator of clonal identity in scleractinian corals. Pages 75-81 in Proc. Fifth Inter. Coral Reef Congress, Tahiti, 6. Schuhmacher, H. and H. Zibrowius. 1985. What is hermatypic? A redefinition of ecological groups in corals and other organisms. Coral Reefs 4: 1-9. Stoddart, 1. A. 1983. Asexual production of planulae in the coral Pocillopora damicornis. Mar. BioI. 76: 279-284. Veron, J. E. N. and M. Pichon. 1980. Scleractinia of Eastern Australia. Pt. III. Aust. Inst. Mar. Sci. Monogr. Ser. 4. 422 pp., 857 figs. Wells, 1. W. 1964. The Recent solitary mussid scleractinian corals. Zool. Meded. Leiden 39; 375- 384. --. 1971. Note on the scleractinian corals Scolymia lacera and S. cubensis in Jamaica. Bull. Mar. Sci. 21; 960-963. Willis, B. and D. J. Ayre. 1985. Asexual reproduction and genetic determination of growth in the coral Pavona cactus; biochemical, genetic and immunogenic evidence. Oecologia, Berlin 65: 516- 525. Zibrowius, H. 1980. Les Scleractinaires de la Mectiterranee et de I'Atlantique nord-oriental. Mem. Inst. Oceanogr. Monaco II: 1-284. Zlatarski, V. N. 1982. Description systematique. Pages 25-343 in V. N. Ziatarski and N. M. Estalella, eds. Les Scleractiniaires de Cuba avec des donnees sur les organismes associes. Editions Acad. Bulgar. Sciences, Sofia, Bulgaria. 472 pp., 161 pis.

DATEACCEPTED: April 14, 1987.

ADDRESS: Division of Sciences, University of New Brunswick, Tucker Park, Saint John, New Brunswick E2L 4L5, Canada.

BULLETINOFMARINESCIENCE,42(1):149-153,1988

CO-SYMBIOSIS IN THE ASCIDIACEA

David L. Parry and Patricia Katt

The prokaryotic green algae of the genus Prochloron Lewin, 1977 (Division Prochlorophyta) has been reported in obligate symbiosis with species of the family Didemnidae (Sub-order Aplousobranchia, Class Ascidiacea) (Kott, 1980; 1982) and in non-obligate symbioses with a wide range of ascidian species (Kott et al., 1984). A similar obligate symbiosis has been reported between red cyanophytes and didemnid ascidians (Lafargue and Duclaux, 1979; Symbesma et a1., 1981; 1 Parry, 1984; Cox et al., 1985; Parry, 1987 ). The presence of more than one species of symbiont in a particular ascidian species has been reported. Trididem- num miniatum KoH, 1977 has both Prochloron and a red filamentous cyanophyte Oscillatoria sp. (Parry, 1984; Larkum et a1., 1987) embedded in the test; Tridi- demnum clinides Kott, 1977 has Prochloron, a red unicellular cyanophyte and a chlorophyte species (KoH, 1982; 1984; Parry, 1984). Trididemnum cerebriforme Hartmeyer, 1913 has a non-obligate association with Proch loran and a red cyanophyte (Kott et al., 1984). The red color of the cyanophytes is due to a dominant

• P3rry.D.L. 1987.Ascidi3n-3lg31symbioses.I. Isol3Jionandchaf3cteriS3tionofphycobiliproteinsfromsymbioticcyanophytesin Dscidians. Symbiosis. Accepted.

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