Coral Borers of the Eastern Pacific: Aspidosiphon (A.) elegans (Sipuncula: Aspidosiphonidae) and Pomatogehia rugosa (Crustacea: Upogebiidae)l

This is the first report of the sipunculan Aspidosiphon (Aspidosiphon) elegans (Chamisso & Eysenhardt, 1821) in the tropical eastern Pacific. With this species the number of coral borers rises to 18 for this region. The upogebiidid crustacean Pomatogebia rugosa (Lockington, 1878) was reported previously (as Upogebia rugosa) from coral colonies in the Gulf of California, Mexico, and from coral reefs of Golfo Dulce, Costa Rica; the latter represented a southward range extension of approximately 3500 km. Subsequently, P. rugosa was recorded from branches of Pocillopora corals in Colombia, extending the range farther southward. In our study, both species were extracted from colonies of the massive coral Porites lobata Dana from Golfo Dulce, southern Pacific coast of Costa Rica. Aspidosiphon (A.) elegans ranged in length from 1 to 20 rom and was present in a density as high as 300 individuals per 1000 cm3. Pomatogebia rugosa was present in 14% of the colonies examined and was responsible for 0.6 ± 0.35% of the CaC03 removed at one site in Golfo Dulce; at her-site-it-was_presenLin_3J.<%:'o_QLthfL~010nieL::!-n.<:LFas re~I'onsiQl~__[<:>£. _ 2.5 ± 2.22% of the CaC03 removed. P. rugosa was found living in pairs insi live coral colonies of Porites lobata, in branched tunnels about 2.5 rom in diameter and lined with mud. Bioerosion caused by these two species of borers in the eastern Pacific is minimal compared with that caused by sea urchins and boring bivalves. (Glynn et al. 1979, Glynn 1988, Eakin 1992, Guzman and Cortes 1992, Reaka-Kudla et al. 1996). In other localities such as Golfo Dulce and Cano Island in Costa Rica, internal bioerosion, caused primarily by Lithophaga spp., is more important (Scott et al. 1988, Guzman and Cortes 1989, Cortes 1991, 1992). Borers are responsible for internal bioerosion ranging from 8.3 to 9.5 kgjm2 per yr (Glynn 1988, Eakin 1992, 1996), but this rate is probably not constant over time and may vary between reefs in the same area, as demonstrated in other regions (Hutchings 1986). In this paper we report for the first time the presence of the sipunculan subgenus Aspidosiphon (Aspidosiphon) in the eastern Paeific~This -immmses the-number-of-known coral-borer species for this region to 18. We also confirm the southward range extension of the crustacean Pomatogebia rugosa (Lockington, 1878) in the eastern Pacific. 170 SIXTEEN CORAL-BORER SPECIES from three different phyla (Mollusca, Crustacea, and Porifera) have been reported from the eastern Pacific (Table 1). However, many sponges and polychaeta, and other organisms extracted from coral colonies, are still unidentified. In some eastern Pacific coral reefs (e.g., Panama, the Galapagos, and Cocos Island), external bioeroders (mainly sea urchins) are more important than borers 1 This study was made possible by the financial support of the Vicerrectoria de Investigaci6n, Universidad de Costa Rica and the Consejo Nacional de Investigaciones Cientificas y Tecnol6gicas (CONICIT). This is acontribution" of -the-Museo de -Zoologia,-Escuela deBiologia, and Centro de Investigaci6n en Ciencias del Mar y Limnologia (CIMAR), Universidad de Costa Rica. Manuscript accepted 4 October 1996. 2 CIMAR and Museo de Zoologia, Escuela de Biologia, Universidad de Costa Rica, San Pedro, Costa Rica.