Larval Development of the Megabalanine Balanomorph Megabalanus rosa (Pilsbry) (Cirripedia, Balanidae) K. H. Choi, D. t. Anderson and C. H. Kim Choi, K. H., Anderson, D. T., & Kim, C. H. Larval development of the megabala-nine balanomorph Megabalanus rosa (Pilsbry) (Cirripedia, Balanidae). Proc. Linn. Soc. N.S.W. 113 (3), 1992: 175-184. The larvae of Megabalanus rosa were reared in the laboratory. Naupliar develop-ment is planktotrophic, reaching the cyprid stage in 14-16 days at 20°C. Diagnostic features of the stages, including limb setation, are described. The relatively large nauplii, with a smooth, globular dorsal shield, resemble those of M. tintinnabulum, but differ from the spinose larvae of Austromegabalanus nigrescens. Larval evidence is used to discuss interrelationships of three megabalanine genera. K. H. Choi, C. H. Kim, Department of Biology, Pusan National University, Pusan 609-735, South Korea, and D. T. Anderson, School of Biological Sciences, University of Sydney, Sydney, Australia 2006; manuscript received 11 June 1991, accepted for publication 21 August 1991. Introduction Megabalanus rosa (Pilsbry, 1916) has a relatively limited geographical range in the northwest Pacific, being found in the inshore waters of Korea, Japan and Taiwan, with a depth range from the lower littoral to 300 m (Newman and Ross, 1976; Kim, 1985). The species is prominent among the lower littoral fauna of the Korea Strait and East China Sea. Fouling has led to the sporadic spread of M. rosa to port waters in other localities such as eastern and western Australia (Jones et al. , 1990). The larval development of M. rosa has not been described. Among the mega-balanine Balanidae, larval development is known for only one species of the warm water genus Megabalanus, M. tintinnabulum, and two austral species, Notomegabalanus agricola and Austromegabalanus nigrescens (Sandison, 1954; Daniel, 1958; Egan and Anderson, 1987). On the basis of this limited evidence, each genus has a distinctive pattern of larval development (Egan and Anderson, 1987), but the account by Daniel (1958) for M. tintinnabulum indicates that development in this widespread species is specialized in a number of ways (e.g. very rapid succession of non-feeding naupliar stages; unusually large cyprid) and may not be typical of other species of Megabalanus. The present work provides an opportunity to test this question and to extend the comparison of larval development in the megabalanines. Materials and Methods Megabalanus rosa was collected from rocks and bivalve shells (Mytilus coruscus) of the lower littoral of Kadbck Island, Kybngsangnam-do, South Korea. Adults were main-tained in the laboratory at 20°C in filtered sea water and fed on Artemia nauplii. Release of larvae was observed in February, 1988. Adults were then opened to obtain egg lamellae containing late stage embryos. When transferred to filtered sea water, these lamellae provided a source of newly hatched larvae (Egan and Anderson, 1985). Some larvae were fixed immediately after hatching. Others were transferred to bowls of filtered sea water at 20°C and fed on Nitzschia closterium. Development through six naupliar stages to the cyprid took 14-16 days. Exuviae and specimens of each developmental stage were fixed in 5% neutral formalin. PROC. LINN. SOC. N.S.W., 113 (3), 1992
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