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The nature of the pigments in octocorals has been investigated by Raman spectroscopy, where laser excitation at 632.8 and 1064 nm were used to characterize the colored components present in the skeleton of the exotic pink-yellow soft coral Chromonephthea braziliensis, the reddish purple sea fan Leptogorgia punicea and the endemic deep violet red Leptogorgia violacea from the southeastern coast of Brazil. The observed positions of two major Raman bands at ca 1500 cm −1 [ν(C C)] and 1130 [ν(C-C)] for all specimens strongly suggest the presence of a mixtureof conjugated polyenes belonging to a class of compounds named parrodienes. The hemiketal steroidal feeding deterrent, 23-keto-cladiellin-A, isolated from C. braziliensis was identified in the crude extracts by the Raman analysis using 1064 nm excitation. The observation of the most important vibrational bands of this compound can be useful in future investigations to monitor its presence in crude extracts of C. braziliensis and or other species.

To determine how benthic, tropical, rocky shore communities were affected by the invasive coral species Tubastraea coccinea and T. tagusensis, 8 sites were studied during 2 yr on rocky shores in the southwest Atlantic Ocean (Brazil) by using both fixed and random sampling techniques. Overall, mean cover of T. tagusensis was 0.7% and T. coccinea was 0.4%, (the eleventh and sixteenth most abundant taxa, respectively, throughout the sites). Forty-two major space occupying taxa were registered. In fixed quadrats there was a 76.6% increase per year in density of Tubastraea spp. over the study period. For percent cover no significant difference in cover over time was detected for T. coccinea, but for T. tagusensis and overall (both species) cover increased significantly. The random quadrats data showed subtle differences from the fixed quadrats. There was an increase in density of Tubastraea spp. through time (67.8% per year over the study period). In random samples the density of T. coccinea increased during the study but that of T. tagusensis did not. The cover of both corals also increased over time. The sites where Tubastraea spp. were most abundant possessed higher diversity, evenness and richness of species. Sites where Tubastraea was present tended to group in ordination. The presence of Tubastraea in the communities caused a mean dissimilarity of 4.8% in the invaded communities. A strong positive relationship between invader cover and change in community structure was found, which suggested complete (100%) community dissimilarity at an invader cover of 45%. The negative effects are sufficient to disturb the native benthic communities throughout the tropical Atlantic Ocean.

Recent studies show that chemical defenses in the exotic soft coral Chromonephthea braziliensis Ofwegen (Nephtheidae, Alcyonacea) can be one of the reasons for the success of this introduced species. We report for the first time the detailed composition of the monohydroxylated sterol fraction and a new hemiketal steroid, 23-keto-cladiellin-A, isolated from the unpalatable hexane extract from C. braziliensis. Bioassay-guided fractionation of this extract revealed that this hemiketal steroid exhibits potent feeding deterrent properties against a natural assemblage of fishes at the natural concentration. The major sterol fraction, containing the monohydroxylated sterols, was inactive in the bioassay. The results suggest that this active molecule may be driving the observed success of the invasion of this soft coral along the Brazilian Atlantic coast.