Coral Reefs (1983)1:243-247 Coral Reefs 9 Springer-Verlag 1983 Oriented Translocation of Energy in Grafted Reef Corals B. Rinkevich and Y. Loya Department of Zoology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel Received 20 April 1982; accepted 12 September 1982 Abstract. Colonies of the Red Sea reef coral Stylophora pistillata were grafted with alien branches (allografts), which had been labelled by NaH14CO3 in the light. The "cold" host-colonies translocated the 14C-containing photosynthetic metabolites in an oriented pathway from the grafted branches into their own tissues. The highest ac- cumulations of 14C products were detected in specific branch-tips of the host, away from the contact zones. The "recipient" colonies utilize these energy-rich materials for their metabolic requirements. The 14CO 2 produced through respiration is consequently detected in the skeletal-carbonate of the tips as Caa4CO3 . The purple morph of S.pistilIata is found to be superior to the yellow morph. Introduction In many cases of naturally growing hermatypic corals, branches of different colonies of the same species, which settle beside one another, are subsequently fused (Lang 1973) and form lumps a few feet across (Gardiner 1931). Furthermore, it is well known that after heavy storm-ac- tivities (such as hurricanes), broken branches of different colonies are spread all over the reef zones and frequently are found lying in piles (Shinn 1976; Highsmith et al. 1980; Tunnicliffe 1981). Regeneration, fusion and growth of broken fragments often follow (Gilmore and Hall 1976; Tunnicliffe 1981). The phenomenon of formation of new reefs by broken branches has been also described for Plei- stocene reefs at Barbados, as well as Holocene reefs at Curacao and Bonaire (Mesolella 1967; Focke 1978). The surprisingly fast recovery of corals and reefs (Shinn 1976; Highsmith et al. 1980) stimulates many questions on the mechanisms by which pieces of coral branches reestablish new colonies. Similar to other branching corals in other localities (Shinn 1976; Gilmore and Hall 1976; Highsmith et al. 1980; Tunnicliffe 1981; Woodley et al. 1981), branches of the shallow water population of Stylophorapistillata at Ei- lat are scattered over the reef during severe southern winter storms. Consequently detached fragments of this species are often found "settled" within alien colonies of the same species. S. pistillata served as the experimental species in the present work, since it is one of the most abundant corals in the Gulf of Eilat (Loya 1972). We describe here a newly discovered phenomenon of oriented translocation of photosynthetically fixed prod- ucts betweengrafted branches of alien corals and host colo- nies, which suggests a competitive mechanism occurring in colonies brought into physical contact. Materials and Methods Branches of different colonies of S.pistillata were incubated in situ with 14C-bicarbonate for 24 h. All incubations were carried out in front of the Marine BiologicalLaboratory in Eilat, Gulf of Eilat, Red Sea. The bran- ches were attached to concrete plates before incubation. After an accli- mation period of at least 24 h, they were enclosed within transparent plastic bags and NaHa4CO3 was injected into the bags (final concentra- tion of 0.05 gCi/ml). After incubation the bags were removed and the la- belled branches were tied to host colonies by plastic filaments. The graft- ing procedure was simple and quick causing minimal damage to bran- ches. Two types of segments were sampled: Tips (dome-likein shape) and fragments below the tips (cylinder-like). The branch samples were brought to the lab where surface areas of the segments (S) were calcu- iated, using the formula S = 2 ~zrh for the cylinder samples, where r = (1 + w)/4 (1 = length, w = width and h = height of the segment), and for branch tips using s=~(h 2 +(1+w)2/16). All measurements were made with a caliper with accuracy of 0.1 mm. Coral branches were put into plastic vials and 0.5 ml of hydrogen peroxide (30%) was slowly added. After complete digestion of the tissue, the skeleton was removed and 0.1 ml of 5 N HCI was added to remove all unincorporated 14C bicarbonate. Two replicates (0.2 ml each) were placed in separate minivials and 1 ml of distilled water followed by 2 ml of Instagel (Packard) scintillation cocktail were added. Activity of I~C was determined by liquid scintilla- tion spectrometer (Packard). Acidification of the coral skeleton produces a4CO2and the only 14C remaining is that of the skeletal matrix. Separation of a4C found in these compartments was done by a special apparatus made of two plastic mini- vials connected by a polypropylene duct (Rinkevieh 1982). Acidification was done by adding 0.5 ml of H3PO 4 (25%) drop by drop. The I4CO2 produced was collected by 1.5 ml of Carbosorb solution (Packard). Two aliquant replicates (0.2 mI each) were taken from the acidified skeletal- solution and 1 ml of distilled water followed by 2 mI of Instagel were added to each replicant.