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1. Virus‐induced spore formation as a defense mechanism in marine diatoms

   https://doi.org/10.1111/nph.16951  

   Pelusi, Angela; De Luca, Pasquale; Manfellotto, Francesco; Thamatrakoln, Kimberlee; Bidle, Kay D.; Montresor, Marina (October 2020, New Phytologist)

   Summary Algal viruses are important contributors to carbon cycling, recycling nutrients and organic material through host lysis. Although viral infection has been described as a primary mechanism of phytoplankton mortality, little is known about host defense responses.We show that viral infection of the bloom‐forming, planktonic diatomChaetoceros socialisinduces the mass formation of resting spores, a heavily silicified life cycle stage associated with carbon export due to rapid sinking.Although viral RNA was detected within spores, mature virions were not observed. ‘Infected’ spores were capable of germinating, but did not propagate or transmit infectious viruses.These results demonstrate that diatom spore formation is an effective defense strategy against viral‐mediated mortality. They provide a possible mechanistic link between viral infection, bloom termination, and mass carbon export events and highlight an unappreciated role of viruses in regulating diatom life cycle transitions and ecological success. 

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2. Bacterial spores respond to humidity similarly to hydrogels

   https://doi.org/10.1073/pnas.2320763121  

   Gor, Gennady Y; Scherer, George W; Stone, Howard A (March 2024, Proceedings of the National Academy of Sciences)

   Bacterial spores have outstanding properties from the materials science perspective, which allow them to survive extreme environmental conditions. Recent work by [S. G. Harrellsonet al.,Nature619, 500–505 (2023)] studied the mechanical properties ofBacillus subtilisspores and the evolution of these properties with the change of humidity. The experimental measurements were interpreted assuming that the spores behave as water-filled porous solids, subjected to hydration forces. Here, we revisit their experimental data using literature data on vapor sorption on spores and ideas from polymer physics. We demonstrate that upon the change of humidity, the spores behave like rubber with respect to their swelling, elasticity, and relaxation times. This picture is consistent with the knowledge of the materials comprising the bacterial cell walls—cross-linked peptidoglycan. Our results provide an interpretation of the mechanics of bacterial spores and can help in developing synthetic materials mimicking the mechanical properties of the spores. 

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3. LATE TRIASSIC CONODONTS FROM NEW YORK CANYON, NEVADA, AND THEIR RELEVANCE TO THE POSITION OF THE NORIAN-RHAETIAN BOUNDARY

   https://doi.org/10.1130/abs/2023AM-393565  

   Golding, Martyn; Rigo, Manuel; Tackett, Lydia Schiavo; Clement, Annaka; Lei, Jerry ZX; Caruthers, Andrew H; Them, Theodore; Gill, Benjamin; Marroquin, Selva M; McCabe, Kayla (January 2023, Geological Society of America Abstracts with Programs)

   Sections of the Gabbs Formation exposed near New York Canyon, Nevada, have long been recognized as important sites for Late Triassic and Early Jurassic stratigraphy, and the Norian-Rhaetian parts of these sections continue to be important for defining this boundary (NRB). The two candidate sections for the base of the Rhaetian are in Tethys; both sections utilize the first occurrence of the conodont species Misikella posthernsteini as a proxy for the boundary. Although not a candidate section, data from New York Canyon will help to determine the most suitable position for the NRB, especially in Panthalassa. Previous reports of conodonts from New York Canyon recognized a fauna with Mockina englandi, Mo. bidentata and morphotypes of Mo. mosheri in the Nun Mine Member, below isolated occurrences of Zieglericonus rhaeticum and Mi. posthernsteini in the Mount Hyatt and Muller Canyon members. The first occurrence of Mi. posthernsteini in the section occurs well above the first occurrence of Rhaetian ammonoids (Paracochloceras amoenum) and together with late Rhaetian radiolarians. It is also above excursions in Sr- and C-isotopes, both of which correlate with Tethyan NRB excursions. Therefore, the NRB has previously been placed much lower in North America than Tethys, at the first occurrences of the radiolarian Proparvicingula moniliformis and the conodont Mo. mosheri morphotype C. To help reconcile the biochronological and geochemical data from New York Canyon, new conodont samples have been collected from the Nun Mine and Mt Hyatt members at the New York Canyon Road and Luning Draw sections. These samples contain: Mo. englandi, Mo. bidentata, and Mo. mosheri morphotypes B and C, all previously reported from New York Canyon, although this is the first record of Mo. mosheri morphotype C from the Nun Mine Member; Parvigondolella spp. B and C, from much lower in the Nun Mine Member than previously reported; and Pa. andrusovi, which has not previously been recorded from North America. Overall, this fauna represents the Mo. bidentata and Mo. mosheri zones of North America, equivalent to the Sevatian Mo. bidentata and Pa. andrusovi zones of Tethys. This would be consistent with a higher placement of the NRB at New York Canyon; however, if the NRB is to be recognized at the first occurrence of Mo. mosheri morphotype C, then the boundary must be lower than previously thought, within the Nun Mine Member. 

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4. Infectivity of the parasite Metschnikowia bicuspidata is decreased by time spent as a transmission spore, but exposure to phycotoxins in the water column has no effect

   https://doi.org/10.1111/fwb.14082  

   Sánchez, Kristel_F; Zhong, Baili; Agudelo, Jorge_A; Duffy, Meghan_A (April 2023, Freshwater Biology)

   Abstract Transmission from one host to another is a crucial component of parasite fitness. For some aquatic parasites, transmission occurs via a free‐living stage that spends time in the water, awaiting an encounter with a new host. These parasite transmission stages can be impacted by biotic and abiotic factors that influence the parasite's ability to successfully infect or grow in a new host.Here we tested whether time spent in the water column and/or exposure to common cyanobacterial toxins impacted parasite transmission stages. More specifically, we tested whether the infectivity, within host growth, and virulence of the fungal parasiteMetschnikowia bicuspidatachanged as a result of time spent in the water or from exposure to cyanotoxins in the water column. We exposed parasite transmission spores to different levels of one of two ecologically important cyanotoxins, microcystin‐LR and anatoxin‐a, and factorially manipulated the amount of time spores were incubated in water. We removed the toxins and used those same spores to infect one genotype of the common lake zooplanktonDaphnia dentifera.We found that cyanotoxins did not impact parasite fitness (infection prevalence and spore yield per infected host) or virulence (host lifetime reproduction and survivorship) at the tested concentrations (10 and 30 μg/L). However, we found that spending longer as a transmission spore decreased a spore's chances for successful infection: spores that were only incubated for 24 hr infected approximately 75% of exposed hosts, whereas spores incubated for 10 days infected less than 50% of exposed hosts.We also found a negative relationship between the final spore yield from infected hosts and the proportion of hosts that became infected. In treatments where spores spent longer in the water column prior to encountering a host, infection prevalence was lower (indicating lower per spore infectivity), but each infected host yielded more spores at the end of infection. We hypothesise that this pattern may result from intraspecific parasite competition within the host.Overall, these results suggest that transmission spores of this parasite are not strongly influenced by cyanotoxins in the water column, but that other aspects of spending time in the water strongly influence parasite fitness. 

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5. Tropical Kingbird at Staten Island, New York and a Northeastwards Surve of Vagrants to North America

   Veit, Richard R.; Manne, Lisa L.; Ciancimino, Anthony V. (March 2022, The Kingbird)

   Tropical Kingbird (Tyrannus melancholicus) is an abundant and widespread Neotropical species with an extended history of vagrancy to temperate North America (Pranty et al. 2016). One at Mount Loretto Unique Area, Staten Island, NY (40.503575, -74.218169) on 26 September 2021 was just the second for New York State, less than a year after the first, at Dobbs Ferry, Westchester County, 27-29 October 2020 (Tom Warren, Julien Ansellem, eBird). These New York records follow scores of records from Florida since 1982 and at least 25 from northeastern North America through 2020. Here we provide details for the Staten Island record, describe the broader recent increase in northward occurrence of vagrant Tropical Kingbirds, and address what could be responsible for this change. Specifically, we tested the hypothesis that the occurrence of Tropical Kingbirds in northeastern North America could be predicted by their occurrence in Florida and confirmed that this was so, supporting the notion that vagrancy to northeastern North America is the result of an ongoing process of population growth, exploratory behavior, and colonization. 

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