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This study quantified the spatial variation of endophyte infections in wild populations of commercially important Chondrus ocellatus in Korea. We examined the variation of infection across four locations, two tidal heights and life-history stage (gametophyte vs tetrasporophyte). One hundred and fifty fronds were collected from the upper and lower C. ocellatus zones and microscopic examinations were conducted to determine their infection symptoms. Our results showed that the percentage of C. ocellatus populations infected by endophytic algae were very high, ranging from 58 to 99%, in all populations examined. Endophyte infection severity of Hakampo and Manripo populations was significantly greater in the lower Chondrus zones but it was significantly higher in the upper zone of Jungdori population. Tetrasporophytic fronds were more susceptible to infection by endophytic algae than gametophytic fronds. Also, the infection symptoms were more severe in the middle and basal parts of the fronds than in the apical parts. The findings of this study are very informative data for the endophyte abundance in the field population of commercial C. ocellatus. [ABSTRACT FROM AUTHOR]

A brown filamentous endophyte, Mikrosyphar zosterae, occasionally appears as an epiendophyte of seagrass in Europe and North America. In the present study, M. zosterae was first isolated from wart-like spots of the red alga Chondrus ocellatus and identified by morphological features and molecular analysis. The production of wart-like spots M. zosterae on the host C. ocellatus fronds was confirmed using Koch's postulates and in mixed culture of the two species. Neither hypertrophic nor hyperplastic cells of host C. ocellatus were found in the wart-like spots which differed from gall composition in other species. Wart-like spot formation by brown filamentous M. zosterae on the red macroalgal fronds is reported for the first time. In the culture, three morphological types of M. zosterae were observed, which were heterotrichous, pseudoparenchymatous and monostromatic prostrate thalli. Phaeophycean hairs and reproductive organs (both unilocular and plurilocular sporangia) of M. zosterae were also observed in the culture. In conclusion, M. zosterae is a causative agent producing wart-like spots on Chondrus fronds, which is a new record in red seaweeds and was confirmed in the laboratory culture for the first time. [ABSTRACT FROM AUTHOR]

To examine the effects of two endophytic algae, Mikrosyphar zosterae (brown alga) and Ulvella ramosa (green alga), on the host Chondrus ocellatus (red alga), culture experiments were conducted. Four treatments were made: endophytefree (Chondrus only), endophyte-M (Chondrus + Mikrosyphar), endophyte-U (Chondrus + Ulvella), and endophytes-M·U (Chondrus + Mikrosyphar + Ulvella). After 3 weeks, the relative growth rates (RGRs) of frond lengths and the number of newly formed bladelets were examined. M. zosterae formed wart-like dots on C. ocellatus fronds, whereas U. ramosa made dark spots. The RGRs of frond lengths of C. ocellatus were significantly greater in the endophyte-free and endophyte-M treatment groups than in the endophyte-U and endophytes-M·U treatment groups, indicating that the growth of host C. ocellatus was inhibited more by the green endophyte U. ramosa than the brown endophyte M. zosterae. The number of newly produced bladelets was greater in the endophyte-U and endophytes-M·U groups than in the endophyte-free and endophyte-M treatment groups. These results indicate that the two endophytes inhibit growth of the host C. ocellatus. The negative effects of U. ramosa on C. ocellatus growth were more severe than those caused by M. zosterae. Furthermore, U. ramosa destroyed the apical meristems of C. ocellatus, whereas M. zosterae did not. On the other hand, C. ocellatus showed compensatory growth in the form of lateral branch production as U. ramosa attacked its apical meristems. [ABSTRACT FROM AUTHOR]

A major goal of phylogeographic analysis using molecular markers is to understand the ecological and historical variables that influence genetic diversity within a species. Here, we used sequences of the mitochondrial Cox1 gene and nuclear internal transcribed spacer to reconstruct its phylogeography and demographic history of the intertidal red seaweed Chondrus ocellatus over most of its geographical range in the Northwest Pacific. We found three deeply separated lineages A, B and C, which diverged from one another in the early Pliocene-late Miocene ( c. 4.5-7.7 Ma). The remarkably deep divergences, both within and between lineages, appear to have resulted from ancient isolations, accelerated by random drift and limited genetic exchange between regions. The disjunct distributions of lineages A and C along the coasts of Japan may reflect divergence during isolation in scattered refugia. The distribution of lineage B, from the South China Sea to the Korean Peninsula, appears to reflect postglacial recolonizations of coastal habitats. These three lineages do not coincide with the three documented morphological formae in C. ocellatus, suggesting that additional cryptic species may exist in this taxon. Our study illustrates the interaction of environmental variability and demographic processes in producing lineage diversification in an intertidal seaweed and highlights the importance of phylogeographic approaches for discovering cryptic marine biodiversity. [ABSTRACT FROM AUTHOR]

Monthly variations in gametophyte and tetrasporophyte biomass of Chondrus ocellatus Holmes, a commercial carragenophyte alga, were examined at wave-exposed and sheltered shore stations of Jungdori, Wando, Korea from September, 2013 to August, 2014. The frequency of infection of the fronds with a green filamentous endophyte was investigated and the endophyte was identified using tufA analysis. Biomass of C. ocellatus was significantly greater at the exposed shore (331.84 g wet wt. m) than at the sheltered shore (181 g wet wt. m); the average biomass was 259 g wet wt. m. Gametophyte biomass of C. ocellatus accounted for 64.25% of the total biomass (259 g wet wt. m); tetrasporophyte biomass was 93.05 g wet wt. m (35.93%). Biomass was minimal in winter and maximal in summer at both stations and similar patterns were found for gametophyte and tetrasporophyte biomass. Frond lengths and weights of C. ocellatus were slightly greater at the exposed shore than at the sheltered shore. Fronds of C. ocellatus were infected by a green endophytic species, which grew in between the cortical and medullar tissue and was identified as Ulvella ramosa by tufA analysis. We conclude that the optimal harvesting period of the C. ocellatus field population in terms of biomass might be autumn, after the rapid growth period. Additional in-depth research on the endophytes, such as infection mechanism and frequency, should be performed in order to maintain and manage the field populations of C. ocellatus. [ABSTRACT FROM AUTHOR]

Abstract: λ-Carrageenan from Chondrus ocellatus was degraded by microwave. The changes in intrinsic viscosity [η] during degradation were investigated. Based on the concept that the random scission of glycosidic linkage basically obeys first-order kinetics, [η] for each short-term microwave process could be obtained. The degradation rate coefficient (k n ) of kinetics equation describing the microwave degradation of λ-carrageenan on different conditions was determined. The results demonstrated that changes of external pressure play a most important role in degradation of λ-carrageenan for same short-term microwave process. The susceptibility to degradation is also related to molecular size and concentration of λ-carrageenan. But at higher stress, the relationship between k n and [η] n deviates first-order kinetics. [Copyright &y& Elsevier]