Ministry of Supply: Chemical Defence Research

doi:10.1038/179399c0

Toxins and Other Bioactive Metabolites in Deep Chlorophyll Layers Containing the Cyanobacteria Planktothrix cf. isothrix in Two Georgian Bay Embayments, Lake Huron

Toxins ◽

10.3390/toxins13070445 ◽

2021 ◽

Vol 13 (7) ◽

pp. 445

Author(s):

Arthur Zastepa ◽

Todd R. Miller ◽

L. Cynthia Watson ◽

Hedy Kling ◽

Susan B. Watson

Keyword(s):

Thermal Stratification ◽

Chemical Defence ◽

Euphotic Zone ◽

Lake Huron ◽

Metabolic Inhibitors ◽

Bioactive Metabolites ◽

Total Biomass ◽

Key Factors ◽

Georgian Bay ◽

And Function

The understanding of deep chlorophyll layers (DCLs) in the Great Lakes—largely reported as a mix of picoplankton and mixotrophic nanoflagellates—is predominantly based on studies of deep (>30 m), offshore locations. Here, we document and characterize nearshore DCLs from two meso-oligotrophic embayments, Twelve Mile Bay (TMB) and South Bay (SB), along eastern Georgian Bay, Lake Huron (Ontario, Canada) in 2014, 2015, and 2018. Both embayments showed the annual formation of DCLs, present as dense, thin, metalimnetic plates dominated by the large, potentially toxic, and bloom-forming cyanobacteria Planktothrix cf. isothrix. The contribution of P. cf. isothrix to the deep-living total biomass (TB) increased as thermal stratification progressed over the ice-free season, reaching 40% in TMB (0.6 mg/L at 9.5 m) and 65% in South Bay (3.5 mg/L at 7.5 m) in 2015. The euphotic zone in each embayment extended down past the mixed layer, into the nutrient-enriched hypoxic hypolimnia, consistent with other studies of similar systems with DCLs. The co-occurrence of the metal-oxidizing bacteria Leptothrix spp. and bactivorous flagellates within the metalimnetic DCLs suggests that the microbial loop plays an important role in recycling nutrients within these layers, particularly phosphate (PO4) and iron (Fe). Samples taken through the water column in both embayments showed measurable concentrations of the cyanobacterial toxins microcystins (max. 0.4 µg/L) and the other bioactive metabolites anabaenopeptins (max. ~7 µg/L) and cyanopeptolins (max. 1 ng/L), along with the corresponding genes (max. in 2018). These oligopeptides are known to act as metabolic inhibitors (e.g., in chemical defence against grazers, parasites) and allow a competitive advantage. In TMB, the 2018 peaks in these oligopeptides and genes coincided with the P. cf. isothrix DCLs, suggesting this species as the main source. Our data indicate that intersecting physicochemical gradients of light and nutrient-enriched hypoxic hypolimnia are key factors in supporting DCLs in TMB and SB. Microbial activity and allelopathy may also influence DCL community structure and function, and require further investigation, particularly related to the dominance of potentially toxigenic species such as P. cf. isothrix.

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The Swedish Defence Research Establishment (FOA) and the influence of historical knowledge on Swedish civil resistance policy

Scandinavian Journal of History ◽

10.1080/03468755.2021.1880474 ◽

2021 ◽

pp. 1-20

Author(s):

Fredrik Bertilsson

Keyword(s):

Historical Knowledge ◽

Civil Resistance ◽

Defence Research

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Growing up aspen: ontogeny and trade-offs shape growth, defence and reproduction in a foundation species

Annals of Botany ◽

10.1093/aob/mcaa070 ◽

2020 ◽

Author(s):

Christopher T Cole ◽

Clay J Morrow ◽

Hilary L Barker ◽

Kennedy F Rubert-Nason ◽

Jennifer F L Riehl ◽

...

Keyword(s):

Intraspecific Variation ◽

Genotypic Variation ◽

Chemical Defence ◽

Extrafloral Nectaries ◽

Foundation Species ◽

Community Genetics ◽

Indirect Defence ◽

Juvenile Period ◽

Trade Offs ◽

Sex Marker

Abstract Background and Aims Intraspecific variation in foundation species of forest ecosystems can shape community and ecosystem properties, particularly when that variation has a genetic basis. Traits mediating interactions with other species are predicted by simple allocation models to follow ontogenetic patterns that are rarely studied in trees. The aim of this research was to identify the roles of genotype, ontogeny and genotypic trade-offs shaping growth, defence and reproduction in aspen. Methods We established a common garden replicating >500 aspen genets in Wisconsin, USA. Trees were measured through the juvenile period into the onset of reproduction, for growth, defence chemistry (phenolic glycosides and condensed tannins), nitrogen, extrafloral nectaries, leaf morphology (specific leaf area), flower production and foliar herbivory and disease. We also assayed the TOZ19 sex marker and heterozygosity at ten microsatellite loci. Key Results We found high levels of genotypic variation for all traits, and high heritabilities for both the traits and their ontogenetic trajectories. Ontogeny strongly shaped intraspecific variation, and trade-offs among growth, defence and reproduction supported some predictions while contradicting others. Both direct resistance (chemical defence) and indirect defence (extrafloral nectaries) declined during the juvenile stage, prior to the onset of reproduction. Reproduction was higher in trees that were larger, male and had higher individual heterozygosity. Growth was diminished by genotypic allocation to both direct and indirect defence as well as to reproduction, but we found no evidence of trade-offs between defence and reproduction. Conclusions Key traits affecting the ecological communities of aspen have high levels of genotypic variation and heritability, strong patterns of ontogeny and clear trade-offs among growth, defence and reproduction. The architecture of aspen’s community genetics – its ontogeny, trade-offs and especially its great variability – is shaped by both its broad range and the diverse community of associates, and in turn further fosters that diversity.

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Brightly coloured tissues in limid bivalves chemically deter predators

Royal Society Open Science ◽

10.1098/rsos.191298 ◽

2019 ◽

Vol 6 (10) ◽

pp. 191298

Author(s):

Lindsey F. Dougherty ◽

Alexandria K. Niebergall ◽

Corey D. Broeckling ◽

Kevin L. Schauer ◽

Jingchun Li

Keyword(s):

Mass Spectrometry ◽

Chemical Defence ◽

Chemical Compositions ◽

Marine Bivalve ◽

Metabolomic Analysis ◽

Defence Mechanism ◽

Defensive Compounds ◽

Mantis Shrimp ◽

Metabolite Profiles ◽

Bivalve Tissues

Members of the marine bivalve family Limidae are known for their bright appearance. In this study, their colourful tissues were examined as a defence mechanism towards predators. We showed that when attacked by the peacock mantis shrimp ( Odontodactylus scyllarus ), the ‘disco’ clam, Ctenoides ales , opened wide to expose brightly coloured tissues to the predator. The predator also significantly preferred to consume the internal, non-colourful clam tissues than the external, colourful tissues. Mass spectrometry-based metabolomic analysis confirmed that colourful tissues had significantly different chemical compositions than the non-colourful ones. The internal, non-colourful tissues had metabolite profiles more similar to an outgroup bivalve than to the species' own colourful external tissues. A number of the compounds that differentiated the colourful tissues from the non-colourful tissues appeared to be peptide-like, which potentially serve as the underlying defensive compounds. This is the first study demonstrating that colourful bivalve tissues are used for chemical defence.

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