The new chytridiomycete Paradinomyces triforaminorum gen. et sp. nov. co-occurs with other parasitoids during a Kryptoperidinium foliaceum (Dinophyceae) bloom in the Baltic Sea

Special issue Marine Benthic Harmful Algal Blooms.-- 11 pages, 5 figures, supplementary materials https://doi.org/10.1016/j.hal.2022.102352.-- Data availability: Data will be made available on requestA new chytrid genus and species was isolated and cultured from samples obtained in the Baltic Sea during a dinoflagellate bloom event. This species is characterized by having a spherical sporangium without papillae and zoospores of 2–3 µm in diameter that are released through 3 discharge pores. Molecular phylogeny based on ribosomal operon showed its sister position to the Dinomyces cluster in Rhizophydiales. Zoospores lack fenestrated cisternae but contain a paracrystalline inclusion, found in a Rhizophydiales representative for the first time. Additionally, the kinetid features are uncommon for Rhizophydiales and only observed in Dinomyces representatives so far. These morphological features and its phylogenetic relationships justify the description of the new genus and speciesParadinomyces triforaminorum gen. nov. sp. nov. belonging to the family Dinomycetaceae. The chytrid was detected during a high-biomass bloom of the dinoflagellate Kryptoperidinium foliaceum. Laboratory experiments suggest this species is highly specific and demonstrate the impact it can have on HAB development. The chytrid co-occurred with three other parasites belonging to Chytridiomycota (Fungi) and Perkinsea (Alveolata), highlighting that parasitic interactions are common during HABs in brackish and marine systems, and these multiple parasites compete for similar hostsAR and EG were funded by the Spanish MICINN Project SMART PID2020-112978GB-I00. This work was partly supported by the Russian Science Foundation grant no. 21–74–20089 (writing, microscopy analysis), the infrastructure of SAK's laboratory was supported by ZIN RAS program 1021051402849–1, and the C7 strain was incorporated in CCPP ZIN RAS collection supported by a grant 075–15–2021–1069 of the Ministry of Science and Higher Education of the Russian Federation. AK was supported by the Academy of Finland, grant 310,449. MK was supported by JSPS KAKENHI 19H05667. EA was supported by The Royal Society (UK) under the Newton International Fellowship (grant number NF170346, call 2017)With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe