Volume 57, Issue 1

Caulerpa spp. form a polymer wound plug that seals their giant cells after mechanical injury, in order to prevent fatal loss of cell material. Initial mass spectrometry and Raman spectroscopy investigations revealed the involvement of the secondary metabolite caulerpenyne in wound sealing polymer formation. In this work, we introduce a comparative Raman spectroscopic study of the wound plug formation in the invasive Caulerpa taxifolia (Valh) Agardh, 1817 and the non-invasive Caulerpa prolifera J.V. Lamour. In both species, the enzymatic transformation of the main secondary metabolite caulerpenyne plays a key role in wound plug formation. An accumulation of caulerpenyne is observed at the inner border of the wound plugs. Furthermore, caulerpenyne and products resulting from its enzymatic transformation and co-polymerization with proteins are found within the wound plug. However, there are significant differences in the chemistry of the wound plugs between the species. The Raman spectra reveal a zonation of the wound plug of C. taxifolia into four chemically distinguishable regions, while that of C. prolifera consists of only three regions with specific chemical composition. These results explain differences in the morphology of the wound plug in both species.

Short-term variations of mycosporine-like amino acids (MAAs) in Pyropia columbina (Montage) W.A. Nelson exposed to nitrate (NO 3 - ) enrichment under different outdoor light treatments during the spring ozone depletion of 2008 in Punta Arenas (Chile) were investigated. Segments of P. columbina thalli were cultivated under three treatments of solar radiation without or with NO 3 - supply (0.38 mmol l -1 ): PAR (P), PAR+UVA (PA), and PAR+UVA+UVB (PAB). Samples were taken at 8:00 h (initial value), 9:30, 12:30, 15:30, and 18:00 h on November 8 and at 9:00 h on November 9 (recovery period). A complex dynamic of MAAs affected by light quality and NO 3 - supply was observed. During the light period, the highest content of MAAs was reached under PAB and NO 3 - enrichment, whereas MAAs increased during the recovery period in P and PAB with no NO 3 - supply. Five MAAs were identified: porphyra-334, shinorine, asterina-330, palythine, and mycosporine-glycine. The hourly accumulation of each MAA varied mainly according to the time of exposure and NO 3 - supply. In general, the percentage of porphrya-334 increased, whereas the other MAAs decreased during the exposure period. These results suggest that MAA content in P. columbina varied in the short-term (hours) and the changes were related to the solar irradiance received and NO 3 - availability.

Seaweed invasions are recognized as one of the major threats to biological diversity and coastal resources. Nevertheless, the number of introduced macroalgae has been underestimated due to the increasing number of cryptic invasions. Polysiphonia morrowii is native to the North Pacific and several cryptic introductions of this species have been reported over the past decade. In this study, we recorded the presence of the invasive P. morrowii in the Southwestern Atlantic (Patagonia Argentina) using a morphological and molecular approach for the identification at species level. Polysiphonia morrowii specimens from Argentina showed no morphological differences from members of invasive populations in France. We found two different haplotypes, suggesting that P. morrowii was probably introduced into this area by multiple introduction events. The increasing number of shipping and aquaculture activities worldwide and the ability of this species to be a successful invader suggest that P. morrowii is likely to be a cosmopolitan invasive species and that further management planning is required for its early detection and control.

Species delineation in the calcified red algal genus Dichotomaria is difficult due to the high degree of morphological similarity observed in these algae; thus, species descriptions are based on a limited set of morphological characters. In this study, we conducted phylogenetic analyses of plastid rbc L and mitochondrial cox 1 sequences and detailed morphological observations on 28 specimens of Dichotomaria from the Indo-Pacific, Bermuda, the Galápagos Islands, and the Lesser Antilles. As a consequence, we propose the new combination Dichotomaria intermedia (R.C.Y. Chou) comb. nov. based on Galaxaura intermedia. This species has flattened branches, three to four cortical cell layers, four sterile branches issuing from the hypogynous cell, and a pericarp formed from the basal cell, as in the genus Dichotomaria . In the rbc L tree, D. intermedia formed a group with Dichotomaria tenera from South Africa. Our results confirmed the occurrence of 11 species and one variety: Dichotomaria apiculata , Dichotomaria australis , Dichotomaria diesingiana , Dichotomaria falcata , Dichotomaria hommersandii , Dichotomaria intermedia , Dichotomaria marginata , Dichotomaria obtusata , D. obtusata var. major , Dichotomaria papillata , Dichotomaria spathulata , and D. tenera. Further study is required to address unidentified genetic groups that cannot currently be assigned to known species groups.

This paper describes the morphology of two new species of Mastogloia identified during a survey of the marine benthic diatom flora of Guam. Mastogloia parlibellioides sp. nov., classified in the section Decussatae, is distinctive in the combination of its valve shape and stria pattern reminiscent of Parlibellus , as well as the presence of rudimentary division walls extending from the free margin to the middle of each partectum. Mastogloia lyra sp. nov., classified in the section Sulcatae, subgroup 2, has internal lyre-shaped lateral sterna and partecta that are displaced toward the midline of the valve by a siliceous flange, which shows oblique partectal ducts. The descriptions of these two new species increase the knowledge base of biodiversity in a Pacific Ocean Mastogloia hotspot.

Patterns in the recruitment, distribution, and persistence of three Ulva species, which can form green tides, were investigated in relation to surface roughness using artificial substrates on intertidal rocky shores of the southern coast of Korea. The vertical distributions of Ulva pertusa , Ulva linza , and Ulva compressa were well separated: U. compressa usually dominated in the upper zone and U. pertusa and U. linza in the lower zone. Ulva pertusa recruitment was observed during autumn, when inorganic nitrogen concentrations in the surface water column were highest. However, the recruitments of U. linza usually occurred during early winter and spring and that of U. compressa during summer–autumn. Ulva pertusa showed highest settlement on rough surfaces in both zones, whereas this pattern only appeared in the upper zone for U. linza and U. compressa . These results indicate that settlement patterns may be affected by desiccation in the upper zone and waves in the lower zone. Once blooms occurred, U. pertusa persisted for about twice as long as the other two Ulva species, suggesting that U. pertusa played an important role in community change. This is the first documentation of persistence periods related to recruitment in bloom-forming green macroalgae.

Phylogenetic analyses based on ITS1, ITS2 and tufA gene sequences confirmed the earlier described presence of three Caulerpa species, namely C. prolifera , C. mexicana and C. scalpelliformis , along the Israeli Mediterranean shores. These analyses also demonstrated that C. mexicana is indeed widespread in this area, and ruled out the presence of the morphologically almost similar and invasive C. taxifolia . In the past, this species has apparently been misidentified by local phycologists. A consistent genotypic variability present in the Israeli C. mexicana sequences creates a well-supported separate clade when compared to their Mediterranean Sea counterparts.