Search the repository

A+ | A- | | SLO | ENG

Abstract: Symbiotic scyphozoan jellyfish are poorly understood in terms of their symbionts and traits, as well as the ecological significance of this association. Dinoflagellate symbionts of the medusae Cotylorhiza tuberculata, Phyllorhiza punctata, and Cassiopea xamachana collected in the Mediterranean Sea and Cabo Frio (Rio de Janeiro, Brazil) were phylogenetically identified based on 28S rDNA and ITS2 haplotypes. The studied medusae harbour only one phylotype of symbionts in a time, but scyphozoan jellyfishes can associate with several types of symbionts. This study confirmed that the main symbionts of investigated scyphozoans belong to the genera Symbiodinium, Philozoon, and Breviolum. The associations between dinoflagellate symbionts and Cotylorhiza tuberculata changed from year to year, hosting Philozoon one year and Breviolum another. Invasive species in the Mediterranean Sea Phyllorhiza punctata harboured dinoflagellate symbionts of genus Symbiodinium as in the native areal. Pigment analysis of two shallow-water symbiont species Breviolum sp. and Philozoon medusarum revealed characteristic profiles for each genus.
Keywords: symbiodiniaceae, scyphozoa, 28S rDNA, ITS2, cultivation, pigments, marine biology
Published in DiRROS: 16.07.2024; Views: 153; Downloads: 103
Full text (3,35 MB)
This document has many files! More...

Abstract: Pseudo-nitzschia H. Peragallo (1900) is a globally distributed genus of pennate diatoms that are important components of phytoplankton communities worldwide. Some members of the genus produce the neurotoxin domoic acid, so regular monitoring is in place. However, the identification of toxic members in routine samplings remains problematic. In this study, the diversity and seasonal occurrence of Pseudo-nitzschia species were investigated in the Gulf of Trieste, a shallow gulf in the northern Adriatic Sea. We used time series data from 2005 to 2018 to describe the seasonal and inter-annual occurrence of the genus in the area and its contribution to the phytoplankton community. On average, the genus accounted for about 15 % of total diatom abundance and peaked in spring and autumn, with occasional outbreaks during summer and large inter-annual fluctuations. Increased water temperature and decreased salinity positively affected the presence of some members of the genus, while strong effects could be masked by an unsuitable definition of the species complexes used for monitoring purposes. Therefore, combining morphological (TEM) and molecular analyses by sequencing the ITS, 28S and rbcL markers, eight species were identified from 83 isolated monoclonal strains: P. calliantha, P. fraudulenta, P. delicatissima, P. galaxiae, P. mannii, P. multistriata, P. pungens and P. subfraudulenta. A genetic comparison between the isolated strains and other strains in the Mediterranean was carried out and rbcL was inspected as a potential barcode marker in respect to our results. This is the first study in the Gulf of Trieste on Pseudo-nitzschia time series from a long-term ecological research (LTER) site coupled with molecular data. We show that meaningful ecological conclusions can be drawn by applying integrative methodology, as opposed to the approach that only considers species complexes. The results of this work will provide guidance for further monitoring efforts as well as research activities, including population genetics and genomics, associated with seasonal distribution and toxicity profiles.
Keywords: Pseudo-nitzschia, morphology, phylogeny, seasonality, time series, Adriatic Sea
Published in DiRROS: 18.03.2020; Views: 3020; Downloads: 1001
Full text (6,60 MB)
This document has many files! More...