Observations on the life history and feeding ecology of a specialized nudibranch predator (Phyllodesmium poindimiei), with implications for biocontrol of an invasive octocoral (Carijoa riisei) in Hawaii Daniel Wagner a, ⁎, Samuel E. Kahng b , Robert J. Toonen c a University of Hawaii at Manoa, Department of Oceanography, Honolulu, HI 96822, USA b Hawaii Pacific University, Kaneohe, Hawaii 96744, USA c University of Hawaii at Manoa, Hawaii Institute of Marine Biology, Kaneohe, HI 96744, USA abstract article info Article history: Received 23 April 2008 Received in revised form 5 February 2009 Accepted 5 February 2009 Keywords: Aeolidoidae Alcyonaria Invasive species Opistobranch Predator–prey The azooxanthellate octocoral, Carijoa riisei (Duchassaing and Michelotti, 1860) has spread throughout the Main Hawaiian Islands over the last 40 years proliferating in abundance. Given the rapid proliferation and ecological impact of the octocoral in Hawaii, there is interest in using the aeolid nudibranch Phyllodesmium poindimiei [Risbec, J., 1928. Contribution á l'étude des nudibranches Néo-Calédoniens. Faune des Colonies Francaises 2: 1–328], a specialized predator of Carijoa sp. in southern Australia, as a potential biocontrol agent. Using the nudibranch for biocontrol of C. riisei warrants examination of its life history and effectiveness at controlling its prey. The specialized nature of P. poindimiei predation is confirmed and some of its life history characteristics are described. The aeolid exhibits an approximately annual life cycle, has planktotrophic development and spawns continuously throughout the year, with no evidence of lunar patterns. However, the nudibranch was not successful at controlling C. riisei populations in any experimental feeding trial. Even under high nudibranch densities in aquaria, predation is incomplete, because portions of C. riisei are left unharmed. Additionally, sponge overgrowth suppresses nudibranch predation on the octocoral, and the portunid crab Thalamita integra is identified as a predator of P. poindimiei. Together these factors indicate that biocontrol of C. riisei using P. poindimiei should not be pursued. Published by Elsevier B.V. 1. Introduction With approximately 3000 species, the Nudibranchia is the largest order within the Opistobranchia (Thompson, 1976; Todd, 1981; Wägele and Klussmann-Kolb, 2005). Nudibranchs are all carnivorous, feeding on an array of sessile, benthic animals, such as sponges, tunicates, bryozoans, hydroids, anemones or corals, which are not exploited heavily by other invertebrate taxa (Thompson, 1976; Todd, 1981, 1983; Bertsch and Johnson,1981; Wägele and Klussmann-Kolb, 2005). The genus Phyllodesmium Ehrenberg, 1831 (Suborder Aeoli- doidae, Family Facelinidae) includes 19 currently described species (see Baba, 1949, 1991a,b; Rudman, 1981, 1991; Avila et al., 1998, Ortiz and Gosliner, 2003; Burghardt and Wägele, 2004; Burghardt and Gosliner, 2006)(Table 1). The different species of Phyllodesmium are similar in that they 1) prey exclusively on alcyonarian corals, 2) exclusively occur in the Indo-Pacific, 3) lack oral glands, 4) possess salivary glands, 5) have cerata that autotomize readily when disturbed, 6) lack defensive nematocysts in their cnidosacs, 7) have sparse epidermal ceratal glands, 8) possess nearly identical repro- ductive systems, and 9) possess an unique tooth shape among aeolids (Rudman, 1981, 1991; Avila et al., 1998; Burghardt and Wägele, 2004; Burghardt and Gosliner, 2006). This genus is also quite unique in that most of its member species house symbiotic zooxanthellae within their digestive gland cells (Rudman, 1981, 1991)(Table 1). Addition- ally, most Phyllodesmium species are relatively stenophagus, relying on one or a few species of alcyonarians as their food source (Rudman, 1981, 1991; Wägele, 2004). Stenophagy is common among the Nudibranchia (Todd, 1981, 1983), however, alcyonarian prey is unusual among aeolid nudibranchs which commonly feed on hydroids or sea anemones (Edmunds, 1975; Rudman, 1981). The individual species of Phyllodesmium are distinguished based on differences in the external color pattern, shape and arrangement of the cerata, digestive gland branching pattern, radular morphology and anal position (Rudman, 1981, 1991; Burghardt and Gosliner, 2006). Most of the published literature on the genus Phyllodesmium has centered on taxonomic descriptions, with scarce information available on the ecology and life history of these animals. As specialized pred- ators, Phyllodesmium species have intimate ecological relationships with their alcyonarian prey (Rudman, 1981, 1991); however, such relationships have thus far not been heavily investigated. We became interested in this question after finding Phyllodesmium poindimiei (Risbec, 1928) apparently feeding on Carijoa riisei (Duchassaing and Journal of Experimental Marine Biology and Ecology 372 (2009) 64–74 ⁎ Corresponding author. Tel.: +1808 256 5014; fax: +1 808 236 7443. E-mail address: wagnerda@hawaii.edu (D. Wagner). 0022-0981/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.jembe.2009.02.007 Contents lists available at ScienceDirect Journal of Experimental Marine Biology and Ecology journal homepage: www.elsevier.com/locate/jembe