In vitro Acaricidal Activity of Serratia Ureilytica Against the Dust Mite Tyrophagus Putrescentiae and Identification of Genes Related to Biocontrol.

The present study evaluated the acaricidal activity of three Serratia strains isolated from Mimosa pudica nodules in the Lancandon zone Chiapas, Mexico. The analysis of the genomes based on the Average Nucleotide Identity, the phylogenetic relationships allows the isolates to be placed in the Serria ureilytica clade. The size of the genomes of the three strains is 5.4 Mb, with a GC content of 59%. The Serratia UTS2 strain presented the highest mortality with 61.41% against Tyrophagus putrescentiae followed by the Serratia UTS4 strain with 52.66% and Serratia UTS3 with 47.69% at 72 h at a concentration of 1X109 cell/mL. In the bioinformatic analysis of the genomes, genes related to the synthesis of chitinases, proteases and cellulases were identified, which have been reported for the biocontrol of mites. It is the first report of S. ureilytica with acaricidal activity, which may be an alternative for the biocontrol of stored products with high fat and protein content.

Experimental Study of White Light Interferometry in Mach-Zehnder Interferometers Based on Standard Single Mode Fiber.

In this work, we experimentally analyzed and demonstrated the performance of an in-line Mach-Zehnder interferometer in the visible region, with an LED light source. The different waist diameter taper and asymmetric core-offset interferometers proposed used a single-mode fiber (SMF). The visibility achieved was V = 0.14 with an FSR of 23 nm for the taper MZI structure and visibilities of V = 0.3, V = 0.27, and V = 0.34 with FSRs of 23 nm, 17 nm, and 8 nm and separation lengths L of 2.5 cm, 4.0 cm, and 5.0 cm between the core-offset structure, respectively. The experimental investigation of the response to the temperature sensor yielded values from 50 °C to 300 °C; the sensitivity obtained was 3.53 a.u./°C, with R2 of 0.99769 and 1% every 1 °C in the transmission. For a range of 50 °C to 150 °C, 20.3 pm/°C with a R2 of 0.96604 was obtained.

A Mouse Systems Genetics Approach Reveals Common and Uncommon Genetic Modifiers of Hepatic Lysosomal Enzyme Activities and Glycosphingolipids.

Identification of genetic modulators of lysosomal enzyme activities and glycosphingolipids (GSLs) may facilitate the development of therapeutics for diseases in which they participate, including Lysosomal Storage Disorders (LSDs). To this end, we used a systems genetics approach: we measured 11 hepatic lysosomal enzymes and many of their natural substrates (GSLs), followed by modifier gene mapping by GWAS and transcriptomics associations in a panel of inbred strains. Unexpectedly, most GSLs showed no association between their levels and the enzyme activity that catabolizes them. Genomic mapping identified 30 shared predicted modifier genes between the enzymes and GSLs, which are clustered in three pathways and are associated with other diseases. Surprisingly, they are regulated by ten common transcription factors, and their majority by miRNA-340p. In conclusion, we have identified novel regulators of GSL metabolism, which may serve as therapeutic targets for LSDs and may suggest the involvement of GSL metabolism in other pathologies.

Variation in phytoplankton diversity during phycoremediation in a polluted Colombian Caribbean swamp.

Phytoplankton composition and abundance are considered among the bioindicators of variations in water quality, due to its sensitivity and rapid responses to changes in environmental parameters. The selection and scaling of the Microalgal Predominant Microbial Consortium (MPMC) were based on live samples collected from the Santiago Apóstol Swamp (SAS) and the Arroyo Grande de Corozal (AGC). The inoculum was scaled in a phycoculture plant, and the inoculation process was performed in the AGC that flows into the SAS. The phytoplankton community monitoring was performed from May 2019 to September 2021. In the process, a total of 1,652,258 gallons were inoculated. Precisely, 103 and 124 species were found in the AGC and SAS, respectively. By evaluating the physical, chemical, and microbiological variables in SAS in a multitemporal way based on the inoculation of the MPMC, it is possible to identify the variables that presented the greatest reduction. The density of SAS presented associations with dissolved oxygen, thermotolerant coliforms, Enterococci, pH, phosphorus, nitrates, speed, and Secchi. The AGC and SAS presented high trophic levels (eutrophication). This contamination by organic matter is probably due to the discharges of the domestic tributaries. The diversity of microalgae and cyanobacteria found in this study allows us to know the anthropogenic impact. The density of microalgae showed the positive impact of the treatment with MCPM, where there was a decrease in the species that denote organic contamination. The phytoremediation treatment was effective in terms of the changes observed in the physicochemical variables, and these changes were directly due to the efficiency of the treatment and not the natural behavior of the water sources in the region.

Reduced RECK levels accelerate skeletal muscle differentiation, improve muscle regeneration, and decrease fibrosis.

The muscle regeneration process requires a properly assembled extracellular matrix (ECM). Its homeostasis depends on the activity of different matrix-metalloproteinases (MMPs). The reversion-inducing-cysteine-rich protein with kazal motifs (RECK) is a membrane-anchored protein that negatively regulates the activity of different MMPs. However, the role of RECK in the process of skeletal muscle differentiation, regeneration, and fibrosis has not been elucidated. Here, we show that during skeletal muscle differentiation of C2C12 myoblasts and in satellite cells on isolated muscle fibers, RECK is transiently up regulated. C2C12 myoblasts with reduced RECK levels are more prone to enter the differentiation program, showing an accelerated differentiation process. Notch-1 signaling was reduced, while p38 and AKT signaling were augmented in myoblasts with decreased RECK levels. Overexpression of RECK restores the normal differentiation process but diminished the ability to form myotubes. Transient up-regulation of RECK occurs during skeletal muscle regeneration, which was accelerated in RECK-deficient mice (Reck±). RECK, MMPs and ECM proteins augmented in chronically damaged WT muscle, a model of muscle fibrosis. In this model, RECK ± mice showed diminished fibrosis compared to WT. These results strongly suggest that RECK is acting as a potential myogenic repressor during muscle formation and regeneration, emerging as a new player in these processes, and as a potential target to treat individuals with the muscle-wasting disease.

Finding a needle in a haystack: larval stages of Didymozoidae (Trematoda: Digenea) parasitizing marine zooplankton.

Larval didymozoids (Trematoda: Digenea) were discovered parasitizing the hemocoel of the heteropod Firoloida desmarestia (redia mean intensity = 13) and the chaetognaths Flaccisagitta enflata and Flaccisagitta hexaptera (metacercaria mean intensity = 1) during a 2014-2016 systematic study of parasites of zooplankton collected in the central and southern regions of the Gulf of California, Mexico. Didymozoid infection route during the early life cycle was inferred combining morphological (light microscopy) and molecular (mitochondrial cytochrome c oxidase subunit I gene, cox1) evidence. Didymozoid rediae parasitizing F. desmarestia were observed, just after field collection of the host, containing hundredths of completely developed cystophorous cercariae, releasing them though the birth pore at approximately one cercaria every 12 s. Cercariae lost their tails developing into a 'young metacercaria' in 1 d at 22 °C without need of an intermediate host. Molecular analysis of cox1 showed that rediae found in F. desmarestia belong to two distinct didymozoid species (Didymozoidae sp. 1 and sp. 2). Metacercariae parasitizing chaetognaths were morphologically identified as Didymozoidae type Monilicaecum and cox1 sequences showed that metacercariae of chaetognaths matched with these two Didymozoidae sp. 1, and sp. 2 species found parasitizing F. desmarestia, plus a third distinct Didymozoidae sp. 3. These are the first DNA sequences of cox1 gene from didymozoid larvae for any zooplankton taxonomic group in the world. We concluded that F. desmarestia is the first intermediate host of rediae and cercariae, and the chaetognaths are the second intermediate hosts where non-encysted metacercariae were found. The definitive host is still unknown because cox1 sequences of present study did not genetically match with any available cox1 sequence of adult didymozoid. Our results demonstrate a potential overlap in the distribution of two carnivorous zooplankton taxonomic groups that are intermediate hosts of didymozoids in the pelagic habitat. The didymozoid specimens were not identified to species level because any of the cox1 sequences generated here matched with the sequences of adult didymozoids currently available in GenBank and Bold System databases. This study provides baseline information for the future morphological and molecular understanding of the Didymozoidae larvae that has been previously based on the recognition of the 12 known morphotypes.

Bioremediation of a Sewage-Contaminated Tropical Swamp Through Bioaugmentation with a Microalgae-Predominant Microbial Consortium.

Bioaugmentation has many applications as a bioremediation technique. It is usually performed by bacteria but microalgal consortia also have great potential for bioremediation. This study evaluated the ability of a microbial consortium with predominance of microalgae (MCPM) to decontaminate the water of the Mallorquín tropical swamp. The Mallorquín Swamp is a natural water reservoir, essential for the ecological and hydric balance of the region, as well as for the fishermen, but has received sewage for more than 20 years. Microalgae for bioremediation purposes were isolated from the swamp, selected, cultured in bioreactors, and poured back into the Mallorquín waters. After bioaugmentation, there was a significant reduction in the BOD5 (98%), nitrates (58%), enterococci (92%), and total coliforms (100%). Notably, despite the MCPM bioaugmentation, the original richness and abundance of phytoplankton in the Mallorquín swamp was not disrupted. These results confirm the benefits of phycoremediation as an effective tool for on-site bioremediation of natural water bodies and show an effective phycoremediation at a large scale without altering the autochthonous microalgae community. This constitutes the first report of a successful MCPM intervention performed at this scale in a natural swamp in Colombia. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-021-00990-y.

Veronia nyctiphanis gen. nov., sp. nov., Isolated from the Stomach of the Euphausiid Nyctiphanes simplex (Hansen, 1911) in the Gulf of California, and Reclassification of Enterovibrio pacificus as Veronia pacifica comb. nov.

The bacterial strain 42Xb2 T was isolated from a female adult krill Nyctiphanes simplex infected with the apostome parasitoid ciliate Pseudocollinia brintoni in January 2007 in the Gulf of California. The strain has the morphological, phenotypic, and molecular characteristics of the bacteria of the family Vibrionaceae. The 16S rRNA gene sequence has a similarity of 97.7% with Enterovibrio pacificus SW014 T and 96.1% similarity with Enterovibrio norvegicus LMG 19839 T. A phylogenomic and a multilocus sequence analyses placed this strain close to the genera Enterovibrio, Grimontia, and Salinivibrio, but clearly forming a separate branch from these bacterial genera. Genomic analyses presented further support this result. A novel genus Veronia gen. nov. and a species Veronia nyctiphanis sp. nov. is here described with CAIM 600 T (= DSM 24592 T = CECT 7578 T) as the type strain. Morphological, physiological, and genetic evidence presented here support the unification of Enterovibrio pacificus and Veronia nyctiphanis in the new genus Veronia. Enterovibrio pacificus is reclassified as Veronia pacifica. V. pacifica is assigned as the type species of the new genus Veronia.Genome Sequencing Data The GenBank/EMBL/DDBJ accession numbers for the genome sequence of Veronia nyctiphanis CAIM 600 T is PEIB01 and of Enterovibrio pacificus CAIM 1920 T is LYBM01. The 16S rRNA gene sequence of V. nyctiphanis CAIM 600 T is JX129353.

Optimizing an LED array for an infrared illumination source using the near field for venous pattern detection.

Accuracy in vein detection is important for intravenous applications such as venipuncture and other medical procedures. The near-infrared (NIR) imaging technique is used to visualize veins based on the difference of absorption of the infrared light by the oxyhemoglobin present in the blood and surrounding tissue. A problem commonly found during the visualization of veins is attributed to the source of light, saturation, low contrast, and dispersion, which are causes of inhomogeneous illumination. In this work, the design and implementation of a light source with LEDs in the range of 750-860 nm are presented. To obtain the design, a numerical simulation was made using the near-field diffraction theory to obtain homogeneous illumination at 40 cm of the sample, with a radial arrangement of three concentric LED rings. With the developed light source, an experimental scheme for the acquisition of vein patterns was implemented. Using a basic algorithm for the identification of intravenous patterns, a prototype was obtained that we believe can be used in intravenous applications and other medical procedures.

Building a Culture of Health at the Neighborhood Level Through Governance Councils.

To explore facilitators and barriers to developing and sustaining collaboration among New York City Department of Health and Mental Hygiene's Neighborhood Health Action Centers and co-located partners, who share information and decision-making through a Governance Council structure of representative members. Semi-structured interviews were conducted in 2018 with 43 Governance Council members across the three Action Centers of East Harlem (13), Tremont (15), and Brownsville (15), New York City. Governance Council members identified collaboration through information- and resource-sharing, consistent meetings and continuous communication as valuable for fostering a culture of health in their communities. Immediate benefits included building relationships, increased access to resources, and increased reach and access to community members. Challenges included difficulty building community trust, insufficient advertisement of services, and navigation of government bureaucracy. The Governance Councils forged collaborative relationships among local government, community-based organizations and clinical providers to improve health and well-being in their neighborhoods. Sharing space, resources and information is feasible with a movement towards shared leadership and decision-making. This may result in community-driven and tailored solutions to historical inequities. In shared leadership models, some internal reform by Government partners may be required.

The Neighborhood as a Unit of Change for Health: Early Findings from the East Harlem Neighborhood Health Action Center.

Place-based approaches have been promoted as one way to reduce health inequities by addressing community-level factors that shape health, such as housing quality, healthcare systems, the built environment, and social capital. In 2016-2017, the NYC Health Department's Center for Health Equity launched three Neighborhood Health Action Centers (Action Centers), which use a place-based approach to improve health in neighborhoods with disproportionate burdens of premature mortality. We describe this approach and the genesis of the Action Centers. We then describe the East Harlem Action Center, which was the first to open, and share findings from qualitative interviews with the East Harlem Action Center's Governance Council, a group comprised of Action Center staff and co-located partners and programs which supports Action Center coordination. Interviewees felt that collaboration, being responsive to community needs, and being community based were essential elements of the Action Center. Interviewees recognized the complex dynamic of a large city agency serving as the host for the Action Center while simultaneously aiming to establish more equitable relationships with partners. Governance Council members' expectations and hopes for the East Harlem Action Center were consistent with the overall vision and model for the Action Centers, which may facilitate implementation.

Krill Nyctiphanes simplex gonad affection associated with acute-intensity phyllobothriid plerocercoid infection.

This is the first acute-intensity record of helminths parasitizing the subtropical krill Nyctiphanes simplex Hansen, 1911. We briefly describe the pathology of infection of Phyllobothriidae gen. sp. plerocercoids parasitizing N. simplex in the Gulf of California. Infection occurred with a very low prevalence (P = 0.06%, n = 1563 specimens), although acute-intensity exceeded several hundred plerocercoids crowding the hemocoel in one female host. Nyctiphanes simplex showed inflammatory response of hemocyte-based infiltration, nodule formation, and presumptive melanization. Remarkably, cestodes invade and supplant the gonad, causing atretic oocytes and severe tissue destruction in the gonad likely leading to castration and cell death in connective tissue of the infected organs suggesting that acute-intensity infection exceeds the krill's reaction capacity. Thus, Phyllobothriidae gen. sp. negatively affects the host by depleting its fitness, leading to total castration to prevent/block host reproduction.

Changes in parasite-chaetognath species assemblages in the Mexican Central Pacific before and during El Niño 1997-1998.

We investigated the seasonal and interannual changes in diversity, abundance, and prevalence of chaetognaths and their parasites collected monthly during 1996-1998 in the Mexican Central Pacific. We tested the hypothesis of a positive relationship between abundance and species richness of chaetognaths and their parasites, and investigated the influence of the 1997-1998 El Niño event on this host-parasite interaction. Of the 9 chaetognath species collected in the present study, only 7 were found to be parasitized. Of 78154 chaetognath specimens collected, 790 were parasitized (1% prevalence) with at least 1 type of epibiont (cysts, perhaps protists) and 6 types of endoparasites: protists (apicomplexans, dinoflagellates, and ciliates), digeneans, cestodes, acanthocephalans, nematodes, and other unidentified endoparasites. Cysts, digeneans, and cestodes were the most abundant parasites. Mean intensity ranged from 1-4 endoparasites and from 1-21 epibionts host-1. Zonosagitta bedoti and Flaccisagitta enflata were the most abundant chaetognath species and had the highest parasite diversity. Mesosagitta minima and Parasagitta euneritica had the highest parasite prevalence (>2%). A 2-way cluster analysis defined sampling month groups as before, during, and after the 1997-1998 El Niño. The highest abundances of chaetognaths and parasites were associated with a high thermal stratification index, salinity, and mixed layer depth. We conclude that there is a positive, non-linear correlation between the abundance of chaetognaths and their parasites. Although El Niño decreased the abundance and diversity of chaetognaths throughout the time series, the abundance and diversity of their parasites were not significantly different among hydro-climatic periods, suggesting that host abundance must decrease orders of magnitude to influence host availability for parasites.

Tetrahydrobiopterin Role in human umbilical vein endothelial dysfunction in maternal supraphysiological hypercholesterolemia.

Maternal physiological hypercholesterolemia (MPH) allows a proper foetal development; however, maternal supraphysiological hypercholesterolemia (MSPH) associates with foetal endothelial dysfunction and early development of atherosclerosis. MSPH courses with reduced endothelium-dependent dilation of the human umbilical vein due to reduced endothelial nitric oxide synthase activity compared with MPH. Whether MSPH modifies the availability of the nitric oxide synthase cofactor tetrahydrobiopterin is unknown. We investigated whether MSPH-associated lower umbilical vein vascular reactivity results from reduced bioavailability of tetrahydrobiopterin. Total cholesterol <7.2mmol/L was considered as maternal physiological hypercholesterolemia (n=72 women) and ≥7.2mmol/L as MSPH (n=35 women). Umbilical veins rings were used for vascular reactivity assays (wire myography), and primary cultures of human umbilical vein endothelial cells (HUVECs) to measure nitric oxide synthase, GTP cyclohydrolase 1, and dihydrofolate reductase expression and activity, as well as tetrahydrobiopterin content. MSPH reduced the umbilical vein rings relaxation caused by calcitonine gene-related peptide, a phenomenon partially improved by incubation with sepiapterin. HUVECs from MSPH showed lower nitric oxide synthase activity (l-citrulline synthesis from l-arginine) without changes in its protein abundance, as well as reduced tetrahydrobiopterin level compared with MPH, a phenomenon reversed by incubation with sepiapterin. Expression and activity of GTP cyclohydrolase 1 was lower in MSPH, without changes in dihydrofolate reductase expression. MSPH is a pathophysiological condition reducing human umbilical vein reactivity due to lower bioavailability of tetrahydrobiopterin leading to lower NOS activity in the human umbilical vein endothelium.

Sodium/proton exchanger isoform 1 regulates intracellular pH and cell proliferation in human ovarian cancer.

Cancer cells generate protons (H+) that are extruded to the extracellular medium mainly via the Na+/H+ exchanger 1 (NHE1), which regulates intracellular pH (pHi) and cell proliferation. In primary cultures of human ascites-derived ovarian cancer cells (haOC) we assayed whether NHE1 was required for pHi modulation and cell proliferation. Human ovary expresses NHE1, which is higher in haOC and A2780 (ovarian cancer cells) compared with HOSE cells (normal ovarian cells). Basal pHi and pHi recovery (following a NH4Cl pulse) was higher in haOC and A2780, compared with HOSE cells. Zoniporide (NHE1 inhibitor) caused intracellular acidification and pHi recovery was independent of intracellular buffer capacity, but reduced in NHE1 knockdown A2780 cells. Zoniporide reduced the maximal proliferation capacity, cell number, thymidine incorporation, and ki67 (marker of proliferation) fluorescence in haOC cells. SLC9A1 (for NHE1) amplification associated with lower overall patient survival. In conclusion, NHE1 is expressed in human ovarian cancer where it has a pro-proliferative role. Increased NHE1 expression and activity constitute an unfavourable prognostic factor in these patients.

Seasonal variation in chaetognath and parasite species assemblages along the northeastern coast of the Yucatan Peninsula.

Chaetognaths are abundant carnivores with broad distributions that are intermediate hosts of trophically transmitted parasites. Monthly variations in chaetognath and parasite species distributions, abundance, prevalence, and intensity related to seasonal environmental changes were recorded in 2004 and 2005 in Laguna Nichupté, a coral reef, and the adjoining continental shelf of Quintana Roo, Mexico. Of 12 chaetognath species plus Sagitta spp., only 5 (Ferosagitta hispida, Flaccisagitta enflata, Sagitta spp., Serratosagitta serratodentata, and Pterosagitta draco) were parasitized. These species were parasitized with 33 types of flatworms and unidentified cysts (likely protozoan ciliates), having an overall mean prevalence of 6%. Digenean metacercaria larvae numerically dominated the parasite assemblages. Cluster analysis defined 2 chaetognath species assemblages. One included 7 species inside Laguna Nichupté, where F. hispida was numerically dominant (98.9%); the other contained 13 chaetognath species in the continental shelf-coral reef region, where F. enflata was abundant (53%). Canonical correspondence analysis showed that Laguna Nichupté had highly variable and hostile conditions (relatively low salinity and high temperature) for chaetognath species except for F. hispida. The higher density of F. hispida promoted greater parasite diversity (23 types), dominated by Brachyphallus sp. metacercariae. F. enflata prevailed in the continental shelf-coral reef area, which had stable high salinity and relatively low temperature. Monilicaecum and unidentified digenean 'type g' infected 5 chaetognath species on the continental shelf. Distinct primary hosts (mollusks and copepods) and contrasting environmental conditions (salinity, dissolved oxygen concentration, and temperature) between Laguna Nichupté and the continental shelf promoted distinct chaetognath species assemblages, resulting in distinct parasite diversity and prevalence patterns.

Nitric oxide and pH modulation in gynaecological cancer.

Nitric oxide plays several roles in cellular physiology, including control of the vascular tone and defence against pathogen infection. Neuronal, inducible and endothelial nitric oxide synthase (NOS) isoforms synthesize nitric oxide. Cells generate acid and base equivalents, whose physiological intracellular concentrations are kept due to membrane transport systems, including Na+ /H+ exchangers and Na+ /HCO3- transporters, thus maintaining a physiological pH at the intracellular (~7.0) and extracellular (~7.4) medium. In several pathologies, including cancer, cells are exposed to an extracellular acidic microenvironment, and the role for these membrane transport mechanisms in this phenomenon is likely. As altered NOS expression and activity is seen in cancer cells and because this gas promotes a glycolytic phenotype leading to extracellular acidosis in gynaecological cancer cells, a pro-inflammatory microenvironment increasing inducible NOS expression in this cell type is feasible. However, whether abnormal control of intracellular and extracellular pH by cancer cells regards with their ability to synthesize or respond to nitric oxide is unknown. We, here, discuss a potential link between pH alterations, pH controlling membrane transport systems and NOS function. We propose a potential association between inducible NOS induction and Na+ /H+ exchanger expression and activity in human ovary cancer. A potentiation between nitric oxide generation and the maintenance of a low extracellular pH (i.e. acidic) is proposed to establish a sequence of events in ovarian cancer cells, thus preserving a pro-proliferative acidic tumour extracellular microenvironment. We suggest that pharmacological therapeutic targeting of Na+ /H+ exchangers and inducible NOS may have benefits in human epithelial ovarian cancer.

Reducing CTGF/CCN2 slows down mdx muscle dystrophy and improves cell therapy.

In Duchenne muscular dystrophy (DMD) and the mdx mouse model, the absence of the cytoskeletal protein dystrophin causes defective anchoring of myofibres to the basal lamina. The resultant myofibre degeneration and necrosis lead to a progressive loss of muscle mass, increased fibrosis and ultimately fatal weakness. Connective tissue growth factor (CTGF/CCN-2) is critically involved in several chronic fibro-degenerative diseases. In DMD, the role of CTGF might extend well beyond replacement fibrosis secondary to loss of muscle fibres, since its overexpression in skeletal muscle could by itself induce a dystrophic phenotype. Using two independent approaches, we here show that mdx mice with reduced CTGF availability do indeed have less severe muscular dystrophy. Mdx mice with hemizygous CTGF deletion (mdx-Ctgf+/-), and mdx mice treated with a neutralizing anti-CTGF monoclonal antibody (FG-3019), performed better in an exercise endurance test, had better muscle strength in isolated muscles and reduced skeletal muscle impairment, apoptotic damage and fibrosis. Transforming growth factor type-ß (TGF-ß), pERK1/2 and p38 signalling remained unaffected during CTGF suppression. Moreover, both mdx-Ctgf+/- and FG-3019 treated mdx mice had improved grafting upon intramuscular injection of dystrophin-positive satellite cells. These findings reveal the potential of targeting CTGF to reduce disease progression and to improve cell therapy in DMD.

Larval trematodes Paronatrema mantae and Copiatestes sp. parasitize Gulf of California krill (Nyctiphanes simplex, Nematoscelis difficilis).

During 4 quantitative-systematic oceanographic cruises at 99 sampling stations in the Gulf of California (January and July 2007, August 2012, and June 2013), we found 2 trematode species (non-encysted mesocercaria stage) parasitizing the hemocoel of 2 krill species at near-shore locations. Copiatestes sp. parasitized Nematoscelis difficilis in January 2007, and Paronatrema mantae parasitized Nyctiphanes simplex in July 2007. Both trematode species had an intensity of 1 parasite per host. This is the first endoparasite known for N. difficilis, the first record of P. mantae infecting zooplankton, and the first confirmed trematode parasitizing krill species in the Gulf of California. We provide quantitative evidence that these 2 trematode species infect krill with considerably low station prevalence (0.03-0.16%) and low population abundances (<1.2 trematodes 1000 m(-3)). A review of trematodes parasitizing krill indicates that syncoeliid trematodes also have (with few exceptions) low population densities and prevalence and lower species diversity than previously thought (suggesting a broader zoogeographic distribution range of these parasites). Due to the low host specificity of syncoeliid trematodes that typically infect more than 1 secondary intermediate host species in their complex life cycle, we propose that N. simplex and N. difficilis are intermediate hosts (although non-conspicuous) for the transmission of syncoeliid trematodes in the Gulf of California.