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Phago-mixotrophy, the combination of photoautotrophy and phagotrophy in mixoplankton, organisms that can combine both trophic strategies, have gained increasing attention over the past decade. It is now recognized that a substantial number of protistan plankton species engage in phago-mixotrophy to obtain nutrients for growth and reproduction under a range of environmental conditions. Unfortunately, our current understanding of mixoplankton in aquatic systems significantly lags behind our understanding of zooplankton and phytoplankton, limiting our ability to fully comprehend the role of mixoplankton (and phago-mixotrophy) in the plankton food web and biogeochemical cycling. Here, we put forward five research directions that we believe will lead to major advancement in the field: (i) evolution: understanding mixotrophy in the context of the evolutionary transition from phagotrophy to photoautotrophy; (ii) traits and trade-offs: identifying the key traits and trade-offs constraining mixotrophic metabolisms; (iii) biogeography: large-scale patterns of mixoplankton distribution; (iv) biogeochemistry and trophic transfer: understanding mixoplankton as conduits of nutrients and energy; and (v) in situ methods: improving the identification of in situ mixoplankton and their phago-mixotrophic activity.

Electrically evoked compound action potentials (ECAPs) generated in the subthalamic nucleus (STN) contain features that may be useful for titrating deep brain stimulation (DBS) therapy for Parkinson’s disease. Delivering a strong therapeutic effect with DBS therapies, however, relies on selectively targeting neural pathways to avoid inducing side effects. In this study, we investigated the spatiotemporal features of ECAPs in and around the STN across parameter sweeps of stimulation current amplitude, pulse width, and electrode configuration, and used a linear classifier of ECAP responses to predict electrode location. Four non-human primates were implanted unilaterally with either a directional (n = 3) or non-directional (n = 1) DBS lead targeting the sensorimotor STN. ECAP responses were characterized by primary features (within 1.6 ms after a stimulus pulse) and secondary features (between 1.6 and 7.4 ms after a stimulus pulse). Using these features, a linear classifier was able to accurately differentiate electrodes within the STN versus dorsal to the STN in all four subjects. ECAP responses varied systematically with recording and stimulating electrode locations, which provides a subject-specific neuroanatomical basis for selecting electrode configurations in the treatment of Parkinson’s disease with DBS therapy.

Mixotrophic oligotrich ciliates use plastids sequestered from algal prey to acquire energy and metabolic products from photosynthesis. We isolated mixotrophic oligotrichs from coastal waters off Massachusetts (MA) and California (CA), as well as from two freshwater ponds in MA, and identified associated plastid 23S rRNA genes. Ciliates were identified using a combination of microscopy and 18S rRNA phylogeny, and includedLaboea strobilaand variousPseudotontonia,Spirotontonia, andStrombidiumspecies from marine waters, andLimnostrombidium viridefrom freshwater. Overall, nearly half of all plastid sequences recovered from ciliates were haptophytes, followed by 15–20% for stramenopiles and chlorophytes, and < 10% originating from cryptophyte algae. No plastid sequences were from dinoflagellates. Cells ofStrombidium ‘biarmatum’collected from coastal MA in spring and fall possessed mostlyMicromonasplastids, but during spring also possessed cryptophyte sequences. During spring,L. strobilawere found to have a mix of chlorophyte, cryptophyte, haptophyte, and stramenopile sequences, while a co‐occurringStrombidiumsp. had mostly chlorophyte and haptophyte sequences. MixotrophicPseudotontoniaandSpirotontoniaspp. were sampled during summer from coastal MA and in Monterey Bay, CA, and cells from both populations were dominated (> 70%) by haptophyte plastids of similar phylogenetic origin.L. viridewere also evaluated from two freshwater ponds and possessed mostlyChrysochromulinasp. (haptophyte) and synurid (stramenopile) sequences. These results are the first survey of the genetic diversity of plastids associated with pelagic mixotrophic oligotrich ciliates and suggest that some species may selectively retain plastids from certain algal groups, while others appear to be generalists.