Gast Rebecca J.

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Gast
First Name
Rebecca J.
ORCID
0000-0003-3875-3975

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Author: Gómez, Fernando ×

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  • Preprint
    Molecular phylogeny of the parasitic dinoflagellate Syltodinium listii (Gymnodiniales, Dinophyceae) and generic transfer of Syltodinium undulans comb. nov. (=Gyrodinium undulans)
    (Elsevier, 2019-09-17) Gómez, Fernando ; Artigas, Luis Felipe ; Gast, Rebecca J.
    The parasitic dinoflagellate Syltodinium listii was investigated from the open waters of the English Channel and the NW Mediterranean Sea. Syltodinium listii has been unreported since its original description in the North Sea. Cells of S. listii were able to immediately infect copepod eggs of different species, and even nauplii, and after each infection to form up to 32 cells embedded in a mucous envelope. Infection of the same host by more than one dinoflagellate was frequent; although overall, the progeny were reduced in number. Molecular phylogeny based on the small subunit ribosomal RNA (SSU rRNA) gene revealed that S. listii clusters with a group of environmental sequences from the cold North Atlantic region as a sister group of Gymnodinium aureolum. The large subunit ribosomal RNA (LSU rRNA) gene sequences of S. listii from the English Channel and cf. Gyrodinium undulans from the Mediterranean Sea were identical. Thus, we propose Syltodinium undulans comb. nov. for Gyrodinium undulans. The first internal transcribed spacer (ITS) and complete SSU rRNA gene sequences of Dissodinium pseudolunula are provided. The parasitic species of Chytriodinium, Dissodinium and Syltodinium cluster together within the family Chytriodiniaceae, including the free-living species Gymnodinium aureolum, G. corollarium and G. plasticum.
  • Preprint
    Dinoflagellates Amyloodinium and Ichthyodinium (Dinophyceae), parasites of marine fishes in the South Atlantic Ocean
    ( 2018-10) Gómez, Fernando ; Gast, Rebecca J.
    The morphology and molecular phylogeny of the parasitic dinoflagellates Ichthyodinium chabelardi and Amyloodinium ocellatum was investigated off Brazil (South Atlantic Ocean). This is the first record of Ichthyodinium and the first molecular data of both parasites from the southern hemisphere. Ichthyodinium chabelardi infected the yolk of eggs of feral populations of Argentine anchovy (Engraulis anchoita; Engraulidae) and Brazilian sardinella (Sardinella brasiliensis; Clupeidae) in different seasons. The SSU rRNA and ITS gene sequences were identical and confirmed Ichthyodinium as a host generalist. The new sequences clustered with the type species I. chabelardi from the North Atlantic and environmental sequences from the Pacific Ocean. A second species from the western Pacific remains undescribed. Amyloodinium ocellatum was isolated from the gills of a cultured cobia fish (Rachycentron canadum) after causing mortality. The SSU rRNA gene sequence of the Brazilian isolate was almost identical to those from the northern hemisphere. This suggests a single species with a widespread distribution, although it is uncertain whether the species has a natural pantropical distribution or is the result of artificial distribution due to the humaninduced fish transport.
  • Article
    Phylogeny and synonymy of Gyrodinium heterostriatum comb. nov. (Dinophyceae), a common unarmored dinoflagellate in the world oceans
    (Jagiellonian University Press, 2020-07-08) Gómez, Fernando ; Artigas, Luis Felipe ; Gast, Rebecca J.
    The North Sea and the English Channel are regions with a long tradition of plankton studies, where the colony-forming haptophyte Phaeocystis globosa dominates the spring phytoplankton blooms. Among its predators, we investigated an abundant unarmored dinoflagellate (~3000 cells per liter) in the North Sea in May 2019. It has been reported in the literature as Gymnodinium heterostriatum or G. striatissimum, and often identified as Gyrodinium spirale. Phylogenetic analyses using the small-, large subunit- and Internal Transcriber Spacers of the ribosomal RNA (SSU-, LSU-, ITS rRNA) gene sequences indicate that our isolates clustered within the Gyrodinium clade. The new sequences formed a sister group with sequences of the freshwater taxon Gyrodinium helveticum, being one of the infrequent marine-freshwater transitions in the microbial world. This isolate is the first characterized member of a clade of numerous environmental sequences widely distributed from cold to tropical seas. This common and abundant taxon has received several names due to its morphological plasticity (changes of size and shape, often deformed after engulfing prey) and the difficulty in discerning surface striation. We conclude that the priority is for the species name Gymnodinium heterostriatum Kofoid & Swezy 1921, a new name that was proposed for Gymnodinium spirale var. obtusum sensu Dogiel 1906. The species Gyrodinium striatissimum (Hulburt 1957) Gert Hansen & Moestrup 2000 and Gymnodinium lucidum D. Ballantine in Parke & Dixon 1964 (=G. hyalinum M. Lebour 1925) are posterior synonyms. We propose Gyrodinium heterostriatum comb. nov. for Gymnodinium heterostriatum.
  • Preprint
    Molecular phylogeny and synonymy of Balechina gracilis comb. nov. (=Gymnodinium gracile), a widespread polymorphic unarmored dinoflagellate (Dinophyceae)
    (Wiley, 2021-01-25) Gómez, Fernando ; Artigas, Luis Felipe ; Gast, Rebecca J.
    Gymnodinium gracile, described from the coasts of Denmark in 1881, is one of the first described unarmored dinoflagellates. Individuals which morphologically fit with the original description were isolated from the English Channel (North‐East Atlantic). The SSU rRNA gene sequences were identical to the sequences identified as Balechina pachydermata and Gymnodinium amphora from the Mediterranean Sea and Brazil. We propose the transfer of Gymnodinium gracile into the genus Balechina as B. gracilis comb. nov. These sequences constitute an independent lineage, clustering with numerous environmental sequences from polar to tropical waters. The widespread distribution, the high plasticity in size, shape and coloration and the difficulties in discerning the fine longitudinal striae have contributed to the description of numerous synonyms: Amphidinium vasculum, Balechina pachydermata (=Gymnodinium pachydermatum), Gymnodinium achromaticum, G. abbreviatum, G. amphora, G. dogielii, G. lohmannii (=G. roseum sensu Lohmann 1908), G. situla and Gyrodinium cuneatum (=G. gracile sensu Pouchet 1885).