Molecular Insights into the Synergistic Effects of Putrescine and Ammonium on Dinoflagellates.

Ammonium and polyamines are essential nitrogen metabolites in all living organisms. Crosstalk between ammonium and polyamines through their metabolic pathways has been demonstrated in plants and animals, while no research has been directed to explore this relationship in algae or to investigate the underlying molecular mechanisms. Previous research demonstrated that high concentrations of ammonium and putrescine were among the active substances in bacteria-derived algicide targeting dinoflagellates, suggesting that the biochemical inter-connection and/or interaction of these nitrogen compounds play an essential role in controlling these ecologically important algal species. In this research, putrescine, ammonium, or a combination of putrescine and ammonium was added to cultures of three dinoflagellate species to explore their effects. The results demonstrated the dose-dependent and species-specific synergistic effects of putrescine and ammonium on these species. To further explore the molecular mechanisms behind the synergistic effects, transcriptome analysis was conducted on dinoflagellate Karlodinium veneficum treated with putrescine or ammonium vs. a combination of putrescine and ammonium. The results suggested that the synergistic effects of putrescine and ammonium disrupted polyamine homeostasis and reduced ammonium tolerance, which may have contributed to the cell death of K. veneficum. There was also transcriptomic evidence of damage to chloroplasts and impaired photosynthesis of K. veneficum. This research illustrates the molecular mechanisms underlying the synergistic effects of the major nitrogen metabolites, ammonium and putrescine, in dinoflagellates and provides direction for future studies on polyamine biology in algal species.

Development of alginate beads for precise environmental release applications: A design of experiment based approach and analysis.

Controlled release of active ingredients are important for drug delivery and more recently environmental applications including modulated dosing of chemical and biological controls. This study demonstrates the importance of investigating various material science factors that can influence the diffusion rates of alginate beads to improve and tune their performance for marine environmental applications. This investigation aimed to design a rational workflow to aid in leveraging alginate bead use as a carrier matrix for releasing a specific active agent into water. Experiments were conducted to focus on the narrow a large list of relevant material formulation parameters, which included chitosan molecular weight, chitosan concentration, calcium concentration, drop height, and bead size. Once the most relevant material preparation methods were screened, a more robust statistic Design of Experiments approach was performed and results determined the important (and unimportant) factors for increasing dye release kinetics in marine water. The process was further streamlined by narrowing the critical experimental factors to a three-level based on the prior analysis: chitosan MW, chitosan concentration, and bead size. Analysis of the collected data indicated that while chitosan MW had a negligible impact (Fstatistic = 0.22), bead size (Fstatistic = 60.33) significantly influenced the diffusion rates based on surface area. However, chitosan MW had minor effects where lower chitosan MW enabled higher product release rates. This case investigation was a novel application of the design of experiment approach towards environmental applications to understand differences in release rates to marine waters for the first time and the workflow provided also serve as the basis for researchers to optimize other environmental applications requiring optimization when it is unknown how a large number of formulation variables will impact performance in different environmental scenarios.

Publisher Correction: Genetic tool development in marine protists: emerging model organisms for experimental cell biology.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Genetic tool development in marine protists: emerging model organisms for experimental cell biology.

Diverse microbial ecosystems underpin life in the sea. Among these microbes are many unicellular eukaryotes that span the diversity of the eukaryotic tree of life. However, genetic tractability has been limited to a few species, which do not represent eukaryotic diversity or environmentally relevant taxa. Here, we report on the development of genetic tools in a range of protists primarily from marine environments. We present evidence for foreign DNA delivery and expression in 13 species never before transformed and for advancement of tools for eight other species, as well as potential reasons for why transformation of yet another 17 species tested was not achieved. Our resource in genetic manipulation will provide insights into the ancestral eukaryotic lifeforms, general eukaryote cell biology, protein diversification and the evolution of cellular pathways.

SSU-rRNA Gene Sequencing Survey of Benthic Microbial Eukaryotes from Guaymas Basin Hydrothermal Vent.

Microbial eukaryotes have important roles in marine food webs, but their diversity and activities in hydrothermal vent ecosystems are poorly characterized. In this study, we analyzed microbial eukaryotic communities associated with bacterial (Beggiatoa) mats in the 2,000 m deep-sea Guaymas Basin hydrothermal vent system using 18S rRNA gene high-throughput sequencing of the V4 region. We detected 6,954 distinct Operational Taxonomic Units (OTUs) across various mat systems. Of the sequences that aligned with known protistan phylotypes, most were affiliated with alveolates (especially dinoflagellates and ciliates) and cercozoans. OTU richness and community structure differed among sediment habitats (e.g. different mat types and cold sediments away from mats). Additionally, full-length 18S rRNA genes amplified and cloned from single cells revealed the identities of some of the most commonly encountered, active ciliates in this hydrothermal vent ecosystem. Observations and experiments were also conducted to demonstrate that ciliates were trophically active and ingesting fluorescent bacteria or Beggiatoa trichomes. Our work suggests that the active and diverse protistan community at the Guaymas Basin hydrothermal vent ecosystem likely consumes substantial amounts of bacterial biomass, and that the different habitats, often defined by distances of just a few 10s of cm, select for particular assemblages and levels of diversity.

Small Polar Molecules: A Challenge in Marine Chemical Ecology.

Due to increasing evidence of key chemically mediated interactions in marine ecosystems, a real interest in the characterization of the metabolites involved in such intra and interspecific interactions has emerged over the past decade. Nevertheless, only a small number of studies have succeeded in identifying the chemical structure of compounds of interest. One reason for this low success rate is the small size and extremely polar features of many of these chemical compounds. Indeed, a major challenge in the search for active metabolites is the extraction of small polar compounds from seawater. Yet, a full characterization of those metabolites is necessary to understand the interactions they mediate. In this context, the study presented here aims to provide a methodology for the characterization of highly polar, low molecular weight compounds in a seawater matrix that could provide guidance for marine ecologists in their efforts to identify active metabolites. This methodology was applied to the investigation of the chemical structure of an algicidal compound secreted by the bacteria Shewanella sp. IRI-160 that was previously shown to induce programmed cell death in dinoflagellates. The results suggest that the algicidal effects may be attributed to synergistic effects of small amines (ammonium, 4-aminobutanal) derived from the catabolization of putrescine produced in large quantities (0.05⁻6.5 fmol/cell) by Shewanella sp. IRI- 160.

Minimally Invasive Myomectomy.

Uterine fibroids can significantly impact a woman's health, fertility, and quality of life. When medical therapy fails, surgery is recommended; the gold standard in uterine-sparing surgery is myomectomy. The evidence-based benefits of minimally invasive myomectomy are detailed in this manuscript. Minimally invasive myomectomy techniques are reviewed, including laparoscopic, robotic-assisted, and laparoscopic or robotic-assisted with mini-laparotomy. Criteria for minimally invasive myomectomy are outlined and preoperative planning is discussed. Both institutional data and data from systematic reviews are included to compare outcomes. Each myomectomy case should take into account clinical characteristics of the myomas, patient preference, and surgeon skill and experience.

Community-Level and Species-Specific Associations between Phytoplankton and Particle-Associated Vibrio Species in Delaware's Inland Bays.

Vibrio species are an abundant and diverse group of bacteria that form associations with phytoplankton. Correlations between Vibrio and phytoplankton abundance have been noted, suggesting that growth is enhanced during algal blooms or that association with phytoplankton provides a refuge from predation. Here, we investigated relationships between particle-associated Vibrio spp. and phytoplankton in Delaware's inland bays (DIB). The relative abundances of particle-associated Vibrio spp. and algal classes that form blooms in DIB (dinoflagellates, diatoms, and raphidophytes) were determined using quantitative PCR. The results demonstrated a significant correlation between particle-associated Vibrio abundance and phytoplankton, with higher correlations to diatoms and raphidophytes than to dinoflagellates. Species-specific associations were examined during a mixed bloom of Heterosigma akashiwo and Fibrocapsa japonica (Raphidophyceae) and indicated a significant positive correlation for particle-associated Vibrio abundance with H. akashiwo but a negative correlation with F. japonica. Changes in Vibrio assemblages during the bloom were evaluated using automated ribosomal intergenic spacer analysis (ARISA), which revealed significant differences between each size fraction but no significant change in Vibrio assemblages over the course of the bloom. Microzooplankton grazing experiments showed that losses of particle-associated Vibrio spp. may be offset by increased growth in the Vibrio population. Moreover, analysis of Vibrio assemblages by ARISA also indicated an increase in the relative abundance for specific members of the Vibrio community despite higher grazing pressure on the particle-associated population as a whole. The results of this investigation demonstrate links between phytoplankton and Vibrio that may lead to predictions of potential health risks and inform future management practices in this region.

Niche of harmful alga Aureococcus anophagefferens revealed through ecogenomics.

Harmful algal blooms (HABs) cause significant economic and ecological damage worldwide. Despite considerable efforts, a comprehensive understanding of the factors that promote these blooms has been lacking, because the biochemical pathways that facilitate their dominance relative to other phytoplankton within specific environments have not been identified. Here, biogeochemical measurements showed that the harmful alga Aureococcus anophagefferens outcompeted co-occurring phytoplankton in estuaries with elevated levels of dissolved organic matter and turbidity and low levels of dissolved inorganic nitrogen. We subsequently sequenced the genome of A. anophagefferens and compared its gene complement with those of six competing phytoplankton species identified through metaproteomics. Using an ecogenomic approach, we specifically focused on gene sets that may facilitate dominance within the environmental conditions present during blooms. A. anophagefferens possesses a larger genome (56 Mbp) and has more genes involved in light harvesting, organic carbon and nitrogen use, and encoding selenium- and metal-requiring enzymes than competing phytoplankton. Genes for the synthesis of microbial deterrents likely permit the proliferation of this species, with reduced mortality losses during blooms. Collectively, these findings suggest that anthropogenic activities resulting in elevated levels of turbidity, organic matter, and metals have opened a niche within coastal ecosystems that ideally suits the unique genetic capacity of A. anophagefferens and thus, has facilitated the proliferation of this and potentially other HABs.

Risk of hysterectomy at the time of myomectomy: an underestimated surgical risk.

OBJECTIVE: To evaluate the risk of hysterectomy at the time of myomectomy and the associated 30-day postoperative morbidity. DESIGN: Cohort study. PATIENTS: Patients who underwent myomectomies identified from the American College of Surgeons' National Surgical Quality Improvement Program from 2010 to 2021. INTERVENTION: Unplanned hysterectomy at the time of a myomectomy procedure. MAIN OUTCOME MEASURES: The Current Procedural Terminology codes were used to identify myomectomies performed with or without concurrent hysterectomy. Preoperative characteristics and morbidity outcomes were obtained. The univariate analysis was performed using the chi-square and Fisher exact tests, as appropriate. Multivariate logistic regression reported risk factors for individuals who underwent hysterectomy at the time of myomectomy. P values of <.05 were considered statistically significant. RESULTS: A total of 13,213 individuals underwent myomectomy, and 399 (3.0%) had a hysterectomy performed during myomectomy. Concurrent hysterectomy was most frequently performed with the laparoscopic approach (7.1%), followed by the abdominal (3.2%) and hysteroscopic (1.9%) approaches. Age ≥43 years, obesity class II and higher, American Society of Anesthesiologists (ASA) class greater than II, tobacco use, longer operative time (>85 minutes), and laparoscopic approach were associated with a significantly increased risk of hysterectomy. When adjusting for age, body mass index, race, ASA class, case type, surgical approach, operative time, preoperative transfusion, preoperative hematocrit, and high fibroid burden, an increased odds of hysterectomy was noted for white race, longer operative time, ASA class III or higher, obesity, laparoscopic approach, and low fibroid burden. Patients who underwent concurrent hysterectomy had a longer median length of hospital stay (2 vs. 1 day), longer median operative time (161 vs. 126 minutes), increased intraoperative/postoperative blood transfusions (14.5% vs. 9.0%), and higher rates of organ/space surgical site infections (1.5% vs. 0.5%) and return to surgery (2.0% vs. 0.7%) than those who did not (P<.05). The risk of a major complication within 30 days of myomectomy increased in patients who underwent concurrent hysterectomy after adjusting for relevant confounders (adjusted odds ratio, 2.4; 95% confidence interval, 1.8-3.2). CONCLUSION: The risk of hysterectomy during a myomectomy is higher than previously reported. The patient age of ≥43 years, obesity, white race, ASA class III or higher, longer operative time, and laparoscopic approach were associated with higher odds of hysterectomy. Identification of patients with these risk factors can aid in patient counseling and surgical planning, which may help reduce the unexpectedly high rates of hysterectomy at planned myomectomy.

Diversity and distributional patterns of ciliates in Guaymas Basin hydrothermal vent sediments.

Little is known about protists at deep-sea hydrothermal vents. The vent sites at Guaymas Basin in the Gulf of California are characterized by dense mats of filamentous pigmented or nonpigmented Beggiatoa that serve as markers of subsurface thermochemical gradients. We constructed 18S rRNA libraries to investigate ciliate assemblages in Beggiatoa mats and from bare sediments at the Guaymas vent site. Results indicated a high diversity of ciliates, with 156 operational taxonomic units identified in 548 sequences. Comparison between mat environments demonstrated that ciliate and bacterial assemblages from pigmented mats, nonpigmented mats, and bare sediments were significantly different and highly correlated with bacterial assemblages. Neither bacterial nor ciliate assemblages were correlated with environmental factors. The most abundant ciliates at Guaymas were more likely to be represented in clone libraries from other hydrothermal, deep-sea, and/or anoxic or microaerophilic environments, supporting the hypothesis that these ciliate species are broadly distributed. The orange mat environment included a higher proportion of ciliate sequences that were more similar to those from other environmental studies than to cultured ciliate species, whereas clone libraries from bare sediments included sequences that were the most highly divergent from all other sequences and may represent species that are endemic to Guaymas.

Nitrate reductase enzymes in alga Chattonella subsalsa are regulated by environmental cues at the translational and post-translational levels.

Nitrate reductase (NR) catalyzes the rate-limiting step in nitrate assimilation. Plant and algal NRs have a highly conserved domain architecture but differ in regulation. In plants, NR activity is regulated by reversible phosphorylation and subsequent binding of 14-3-3 proteins at a conserved serine residue. Algal NRs typically lack 14-3-3 binding motifs, which have only recently been identified in a few algal species. Previous research indicates that the alga, Chattonella subsalsa, possesses a novel NR, NR2-2/2HbN (NR2), which incorporates a 2/2 hemoglobin domain. A second NR (NR3) in C. subsalsa lacks the cytochrome b5 (heme-Fe) domain but includes a putative binding motif for 14-3-3 proteins. The expression of NR2 and NR3 genes indicates that NR2 transcript abundance was regulated by light, nitrogen source, and temperature, while NR3 transcript levels were only regulated by light. Here, we measured total NR activity in C. subsalsa and the potential for regulation of NR activity by putative 14-3-3 binding proteins. Results indicate that NR activity in C. subsalsa was regulated by light, nitrogen source, and temperature at the translational level. NR activity was also regulated by endogenous rhythm and temperature at the post-translational level, supporting the hypothesis that NR3 is regulated by 14-3-3 binding proteins. Together with a previous report describing the regulation of NR gene expression in C. subsalsa, results suggest that C. subsalsa responds to environmental conditions by differential regulation of NRs at transcriptional, translational, and post-translational levels. This flexibility may provide a competitive advantage for this species in the environment. To date, this is the first report which provides evidence for the potential post-translational regulation of NR by 14-3-3 proteins in algal species and suggests that regulatory mechanisms for NR activity may be shared between plants and some algal species.

Effects of nitrate and ammonium on assimilation of nitric oxide by Heterosigma akashiwo.

The harmful alga Heterosigma akashiwo possesses a hybrid nitrate reductase (NR) enzyme, NR2-2/2HbN, which has the potential to convert NO to nitrate for assimilation into biomass. In previous research, NR transcription in H. akashiwo was induced by nitrate while NR activity was inhibited by ammonium. Here, the capacity of H. akashiwo to use NO in the presence of nitrate and/or ammonium was investigated to understand the regulation of NO assimilation. Continuous cultures of H. akashiwo were acclimated to growth on nitrate, ammonium, or a mixture of both. Aliquots from these cultures were spiked with 15N-labeled NO. The expression of genes involved in nitrogen assimilation was evaluated, as well as nitrate reductase activity and assimilation of 15N-labeled nitrogen into algal biomass. Results showed that NO induced expression and activity of NR, and upregulated expression of GOGAT regardless of the presence of other inorganic nitrogen sources, while GS expression decreased over time. Furthermore, 15NO uptake and assimilation was significantly higher in cultures acclimated for growth on ammonium compared to cultures acclimated for growth on nitrate alone. Assimilation of NO may provide H. akashiwo with a competitive advantage in N-poor environments or areas with elevated NO.

Racial disparities in telehealth use during the coronavirus disease 2019 pandemic.

OBJECTIVE: To investigate the impact of coronavirus disease 2019 on initial infertility consultations. DESIGN: Retrospective cohort. SETTING: Fertility practice in an academic medical center. PATIENTS: Patients presenting for initial infertility consultation between January 2019 and June 2021 were randomly selected for prepandemic (n = 500) and pandemic (n = 500) cohorts. EXPOSURE: Coronavirus disease 2019 pandemic. MAIN OUTCOME MEASURES: The primary outcome was a change in the proportion of African American patients using telehealth after pandemic onset compared with all other patients. Secondary outcomes included presentation to an appointment vs. no-show or cancellation. Exploratory outcomes included appointment length and in vitro fertilization initiation. RESULTS: The prepandemic cohort vs. the pandemic cohort had fewer patients with commercial insurance (64.4% vs. 72.80%) and more African American patients (33.0% vs. 27.0%), although the racial makeup did not differ significantly between the two cohorts. Rates of missed appointments did not differ between the cohorts, but the prepandemic cohort vs. the pandemic cohort was more likely to no-show (49.4% vs. 27.8%) and less likely to cancel (50.6% vs. 72.2%). African American patients, compared with all other patients, during the pandemic were less likely to use telehealth (57.0% vs. 66.8%). African American patients, compared with all other patients, were less likely to have commercial insurance (prepandemic: 41.2% vs. 75.8%; pandemic: 57.0% vs. 78.6%), present to their scheduled appointment (prepandemic: 52.7% vs. 73.7%; pandemic: 48.1% vs. 74.8%), and cancel vs. no-show (prepandemic: 30.8% vs. 68.2%, pandemic: 64.3% vs. 78.3%). On multivariable analysis, African American patients were less likely (odds ratio 0.37, 95% confidence interval 0.28-0.50) and telehealth users were more likely (odds ratio 1.54, 95% confidence interval 1.04-2.27) to present to their appointments vs. no-show or cancel when controlling for insurance type and timing relative to the onset of the pandemic. CONCLUSION: Telehealth implementation during the coronavirus disease 2019 pandemic decreased the overall no-show rate, but this shift did not apply to African American patients. This analysis highlights disparities in insurance coverage, telehealth utilization, and presentation for an initial consultation in the African American population during the pandemic.

Metabolomic Insights of the Effects of Bacterial Algicide IRI-160AA on Dinoflagellate Karlodinium veneficum.

Shewanella sp. IRI-160 is an algicidal bacterium that secretes an algicide, IRI-160AA. This algicide specifically targets dinoflagellates, while having no adverse effects on other algal species tested. Dinoflagellates exposed to IRI-160AA exhibited increased production of reactive oxygen species (ROS), DNA damage, and cell cycle arrest, implying a programmed pathway leading to cell death (PCD). Here, a metabolomic analysis was conducted on dinoflagellate Karlodinium veneficum and a control cryptophyte species Rhodomonas exposed to IRI-160AA to investigate the cellular mechanisms behind the physiological effects and the specificity of this algicide. Results of this research supported previous observations about physiological responses to the algicide. A suite of metabolites was identified that increased in the cell pellets of K. veneficum but not in Rhodomonas, including oxidative stress biomarkers, antioxidants, and compounds involved in DNA damage and PCD. Overall, the results of this study illustrated the metabolomic mechanisms underlying the algicidal effects of IRI-160AA on dinoflagellates. This research also provided insights and future directions for studies on the cellular response of dinoflagellates exposed to antagonistic bacteria in the environment.

Algicidal Bacteria: A Review of Current Knowledge and Applications to Control Harmful Algal Blooms.

Interactions between bacteria and phytoplankton in aqueous ecosystems are both complex and dynamic, with associations that range from mutualism to parasitism. This review focuses on algicidal interactions, in which bacteria are capable of controlling algal growth through physical association or the production of algicidal compounds. While there is some evidence for bacterial control of algal growth in the field, our understanding of these interactions is largely based on laboratory culture experiments. Here, the range of these algicidal interactions is discussed, including specificity of bacterial control, mechanisms for activity, and insights into the chemical and biochemical analysis of these interactions. The development of algicidal bacteria or compounds derived from bacteria for control of harmful algal blooms is reviewed with a focus on environmentally friendly or sustainable methods of application. Potential avenues for future research and further development and application of bacterial algicides for the control of algal blooms are presented.

The relationship between anti-Müllerian hormone, body mass index and weight loss: A review of the literature.

Anti-Müllerian hormone (AMH) is commonly used as a proxy for ovarian reserve due to its secretion by antral follicles. It is considered a metric for prediction of ovarian response to certain assisted reproduction therapies. As obesity has a negative impact on fertility, it is important to establish whether obesity-induced hormonal changes influence AMH levels, if and how weight loss affects AMH, and if that influence represents altered reproductive function. The aim of this study was to review the existing literature on the effects of body mass index and weight loss on AMH levels. A PubMed literature keyword search with relevant terms was performed to identify studies that have reported on the AMH/BMI relationship in cohorts with or without polycystic ovarian syndrome (PCOS). A second search was performed to gather publications on weight loss and AMH. Both searches were filtered for all full-text, English-language, adult-female and human-only literature through 1 January 2022. The relationship between AMH and body mass index (BMI) in reproductive-aged women remains inconclusive, with studies in women with and without PCOS producing mixed results. Research in this area is currently limited by failure to analyse the full spectrum of obesity, hindering generalization to a global population increasingly affected by the condition. Some authors pointed to evidence of race/ethnicity as a confounding factor of the relationship, but results between studies are contradictory. Limited evidence on weight loss suggests it may decrease AMH levels despite improving fertility outcomes, particularly after bariatric surgery. The impact of BMI and weight loss on AMH levels has not been conclusively established. Future studies will require appropriate design and sample size calculations, consideration for additional potential confounding factors and inclusion of higher BMIs and a thorough analysis of the full range of obesity.

On the shoulders of giants: perspectives in minimally invasive reproductive surgery.

The purpose of this video is to illustrate the evolution of minimally invasive surgery from the perspectives of several pioneering surgeons in the field of reproductive surgery who, among others, were present during its nascence and exponential growth. Interviews were conducted with five reproductive surgeons who had foundational roles in the innovation of operative laparoscopy and hysteroscopy. Surgeons interviewed include Drs. Victor Gomel, Togas Tulandi, Stephen Corson, Jacques Donnez, and Camran Nezhat. The interviews were conducted using standardized questions and recorded, edited, and grouped both thematically and in sequence to develop an illustration of their perspectives. A diverse array of reproductive surgeons has been instrumental in establishing minimally invasive surgery as a safe and effective means of diagnosing and treating patients with infertility. The transition from laparotomy to laparoscopy consistently has had distinct challenges for each but ultimately led to significant advances in surgical management and improvement in outcomes for patients with infertility and chronic pelvic pain. Through structured interviews from some of our surgical pioneers, they not only recognize their predecessors and contemporaries but also teach us valuable lessons about our history, sparking innovation, and newer surgical applications of reproductive surgery in reproductive endocrinology and infertility practice.

Heterosigma akashiwo does not serve as prey and chloroplast donor for the toxic dinoflagellate, Dinophysis acuminata.

In laboratory culture, the toxic dinoflagellate Dinophysis acuminata acquires plastids from the ciliate, Mesodinium rubrum, which, in turn, acquires plastids from the cryptophyte, Teleaulax amphioxeia. Reports of D. acuminata from field samples found plastids of the raphidophyte, Heterosigma akashiwo within D. acuminata cells, suggesting a broader range of prey. Dinophysis blooms often co-occur with H. akashiwo in Delaware's inland bays. In the study presented here, predation on H. akashiwo by D. acuminata was investigated. Growth rates of D. acuminata were measured when cultured with H. akashiwo either alone or with its known prey, M. rubrum. M. rubrum was also cultured with H. akashiwo to examine predation by the ciliate as a vector for Heterosigma plastids. Ingestion rates by D. acuminata were measured when presented with H. akashiwo as prey, and retention of plastids from H. akashiwo was investigated by measuring chlorophyll a fluorescence intensities in D. acuminata cells presented with H. akashiwo as prey compared to M. rubrum. Additionally, a fluorescence-based method was developed to identify the presence of the accessory pigment fucoxanthin from H. akashiwo plastids in cells of D. acuminata. Results showed that the growth rate of D. acuminata was significantly lower when offered H. akashiwo as prey compared the growth rate when offered M. rubrum as prey. Likewise, no predation was observed when D. acuminata was offered H. akashiwo as prey. Intensity of chlorophyll a fluorescence was lower when H. akashiwo was offered as prey compared to M. rubrum, and fucoxanthin was not detected in any of the Dinophysis cells examined after incubation with H. akashiwo. Results of this investigation do not support the hypothesis that D. acuminata preys on H. akashiwo and highlight the need for further research on factors that stimulate the growth of Dinophysis in field populations.