Trophic Stage Research Articles

SreC-dependent adaption to host iron environments regulates the transition of trophic stages and developmental processes of Curvularia lunata.

Plant pathogens are challenged by host-derived iron starvation or excess during infection, but the mechanism of plant pathogens rapidly adapting to the dynamic host iron environments to assimilate iron for invasion and colonization remains largely unexplored. Here, we found that the GATA transcription factor SreC in Curvularia lunata is required for virulence and adaption to the host iron excess environment. SreC directly binds to the ATGWGATAW element in an iron-dependent manner to regulate the switch between different iron assimilation pathways, conferring adaption to host iron environments in different trophic stages of C. lunata. SreC also regulates the transition of trophic stages and developmental processes in C. lunata. SreC-dependent adaption to host iron environments is essential to the infectious growth and survival of C. lunata. We also demonstrate that CgSreA (a SreC orthologue) plays a similar role in Colletotrichum graminicola. We conclude that Sre mediates adaption to the host iron environment during infection, and the function is conserved in hemibiotrophic fungi.

Vegetative cell fusion and a new stage in the life cycle of the Aphelida (Opisthosporidia).

The aphelids, intracellular parasitoids of algae, represent a large cluster of species sister to Fungi in molecular phylogenetic trees. Sharing a common ancestor with Fungi, they are very important in terms of evolution of these groups of Holomycota. Aphelid life cycle being superficially similar to that of Chytridiomycetes is understudied. We have found in the aphelids a new stage-big multiflagellar and amoeboid cells, formed from a plasmodium that has two sorts of nuclei after trophic stage fusion. The families of protein-coding genes involved in the vegetative cell fusion in Opisthokonta were also discussed.

Life cycle and plasmodial axenic culture of Physarum galbeum.

Myxogastrea is a group of eukaryotic microorganisms included in Amoebozoa. Its life cycle includes two trophic stages: plasmodia and myxamoeflagellates. However, only about 102 species have their complete life cycle known in literature and only about 18 species have their plasmodial axenic culture accomplished in laboratory conditions. The research presented herein involved culturing of Physarum galbeum on the water agar medium. The events that transpired during its life cycle including spore germination, plasmodia formation, and sporocarp development were documented especially the subglobose or discoid sporotheca and the stalk formation. The spores germinated by the V-shape split method to release a single protoplasm. Yellow-green pigmented phaneroplasmodia developed into sporocarps by subhypothallic type. The present article gives details of the sporocarp development of P. galbeum and its plasmodial axenic culture on solid and liquid mediums.

Understanding protein import in diverse non-green plastids.

The spectacular diversity of plastids in non-green organs such as flowers, fruits, roots, tubers, and senescing leaves represents a Universe of metabolic processes in higher plants that remain to be completely characterized. The endosymbiosis of the plastid and the subsequent export of the ancestral cyanobacterial genome to the nuclear genome, and adaptation of the plants to all types of environments has resulted in the emergence of diverse and a highly orchestrated metabolism across the plant kingdom that is entirely reliant on a complex protein import and translocation system. The TOC and TIC translocons, critical for importing nuclear-encoded proteins into the plastid stroma, remain poorly resolved, especially in the case of TIC. From the stroma, three core pathways (cpTat, cpSec, and cpSRP) may localize imported proteins to the thylakoid. Non-canonical routes only utilizing TOC also exist for the insertion of many inner and outer membrane proteins, or in the case of some modified proteins, a vesicular import route. Understanding this complex protein import system is further compounded by the highly heterogeneous nature of transit peptides, and the varying transit peptide specificity of plastids depending on species and the developmental and trophic stage of the plant organs. Computational tools provide an increasingly sophisticated means of predicting protein import into highly diverse non-green plastids across higher plants, which need to be validated using proteomics and metabolic approaches. The myriad plastid functions enable higher plants to interact and respond to all kinds of environments. Unraveling the diversity of non-green plastid functions across the higher plants has the potential to provide knowledge that will help in developing climate resilient crops.

Substrate assemblages of Myxomycetes (Myxogastria) on the bark of living trees and aerial litter in Vietnamese forests

Myxomycete (Myxogastria) are amoeboid protists, usually associated with soil or nearby substrates, as their trophic stages require moist conditions and sufficient number of microorganisms to feed on. However, they are able to inhabit places that have no direct connection with soil. In this paper myxomycete assemblages encountered on bark and aerial liter, a unique substrate of tropical forest, were studied. The material was collected in different years in various vegetation types of 3 national parks, Phia Oac-Phia Den, Bidoup-Nui Ba and Cat Tien, located in distant parts of Vietnam during the last 10 years. Taxonomic diversity was revealed via the experiment using moist chamber cultures. A total of 1009 cultures resulted in 747 records, assigned to 87 morphospecies from 5 orders, 9 families, and 23 genera. Seventy-three species were recorded on the bark of living plants and 45 were found on aerial litter, and the study for each substrate was completed for 74.5 and 72.7 per cent respectively. More than a half of the total number of species was presented by singletons and doubletons. The analysis of indicator species was performed, which confirmed the dominance of specialist species on bark (Cribraria confusa, C. minutissima, and Licea operculata) and aerial litter (Perichaena depressa, P. dictyonema, and P. pedata). Some species, such as Perichaena chrysosperma, demonstrated no specific substrate preference. A typical lignicolous species in temperate regions, Stemonitis fusca, appeared to be abundant on aerial litter, showing a change in substrate preferences, which is common for several myxomycete species in tropics. High-quality photographs, including those obtained with SEM, of 10 indicator morphospecies are provided.

Double trouble: could Ichthyophthirius multifiliis be a vehicle for the bacterium associated with red mark syndrome in rainbow trout, Oncorhynchus mykiss?

Red mark syndrome (RMS) is a disease of farmed rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), one of the most widespread freshwater farmed species in Europe. The disease emerges at water temperatures below 16 °C and consists of one or more bright red skin lesions on the fish body. Mortality due to RMS is reportedly rare, but the disease leads to downgrading of the product and subsequent economic losses. Despite the disease impact, the causative agent for RMS is still formally undetermined although increasing evidence points to a bacterium ascribed to the Midichloriaceae family (order Rickettsiales), hereafter referred to as RMS-Midichloria like organism (RMS-MLO).Intriguingly, recently deposited sequences revealed the presence of RMS-MLO-like bacteria associated with Ichthyophthirius multifiliis, a common protozoan skin parasite of freshwater fish frequently harboring bacterial endosymbionts. Therefore, we hypothesized that I. multifiliis could be a vehicle for RMS-MLO. This was tested by infecting RMS-diseased rainbow trout with I. multifiliis theronts, and subsequently investigating the presence of RMS-MLO in tomonts detached from the fish.Real time PCR analyses showed clearly that I. multifiliis previously exposed to RMS-affected fish become positive to RMS-MLO suggesting that this bacterium can be at least transiently acquired and carried by the protozoan. Moreover, statistical analyses suggested a possible level of vertical transmission in I. multifiliis from one trophic stage to the next one. Further studies will be necessary to prove whether I. multifiliis has a role in the horizontal transfer of RMS-MLO bacteria from diseased RMS fish to healthy ones.

Haplosporosomes, sporoplasmosomes and their putative taxonomic relationships in rhizarians and myxozoans.

This paper reviews current knowledge of the structure, genesis, cytochemistry and putative functions of the haplosporosomes of haplosporidians (Urosporidium, Haplosporidium, Bonamia, Minchinia) and paramyxids (Paramyxa, Paramyxoides, Marteilia, Marteilioides, Paramarteilia), and the sporoplasmosomes of myxozoans (Myxozoa - Malacosporea, Myxosporea). In all 3 groups, these bodies occur in plasmodial trophic stages, disappear at the onset of sporogony, and reappear in the spore. Some haplosporidian haplosporosomes lack the internal membrane regarded as characteristic of these bodies and that phylum. Haplosporidian haplosporogenesis is through the Golgi (spherulosome in the spore), either to form haplosporosomes at the trans-Golgi network, or for the Golgi to produce formative bodies from which membranous vesicles bud, thus acquiring the external membrane. The former method also forms sporoplasmosomes in malacosporeans, while the latter is the common method of haplosporogenesis in paramyxids. Sporoplasmogenesis in myxosporeans is largely unknown. The haplosporosomes of Haplosporidium nelsoni and sporoplasmosomes of malacosporeans are similar in arraying themselves beneath the plasmodial plasma membrane with their internal membranes pointing to the exterior, possibly to secrete their contents to lyse host cells or repel haemocytes. It is concluded that these bodies are probably multifunctional within and between groups, their internal membranes separating different functional compartments, and their origin may be from common ancestors in the Neoproterozoic.

Vaccuuming method as a successful strategy in the diagnosis of active infestation by Pediculus humanus capitis.

ABSTRACTMost human epidemiological and clinical studies use visual inspection of the hair and scalp to diagnose Pediculus humanus capitis , however this method has low sensitivity to diagnose active infestations (presence of nymphs and adult lice). Vacuuming the hair and scalp has been used as a diagnostic method, but there are no previous data comparing its effectiveness with visual inspection. The aim of this study was to determine the prevalence of overall infestation (nits and trophic stages), of active infestation by Pediculus humanus capitis , and to evaluate the effectiveness of vacuuming in comparison with the visual inspection. Visual inspection was performed by three examiners and vacuuming of the scalp by one investigator, with an adapted vacuum cleaner. A total of 166 children aged 4 to 10 years old were randomly selected from public schools in Southern Brazil. Considering the positive results obtained by both methods, the prevalence of overall infestation was 63.3%, whereas active infestation was 18.7%. The visual inspection was more effective on diagnosing overall infestation, however, its effectiveness to detect active infestation was lower, ranging from 0.6% (RR=3%, p<0.001) to 6.6% (RR=35%, p=0.001), depending on the number of examiners. The effectiveness of vacuuming to diagnose active infestation was higher than the one of visual inspection, with a prevalence rate of 16.3% (RR=87%, p=0.332). As presented in our study, the vacuuming method was 2.74 to 7.87 times most likely to detect active infestation, thus it could be adopted as a more accurate method to diagnose active pediculosis.

Non-pollen palynomorphs notes: 3. Phototrophic loricate euglenoids in paleoecology and the effect of acetolysis on Trachelomonas loricae

Algal palynomorphs are useful indicators of freshwater environments in the past and present, allowing reconstruction of such environmental characteristics as former pH, trophic stage, temperature and salinity. However, the using of algal palynomorphs in paleoecology is restricted by their resistance to natural degradation and acetolysis treatment. In this study, we evaluate the usefulness of the loricate euglenophyte genera Trachelomonas and Strombomonas as paleoecological indicators. In order to evaluate their resistance to degradation, loricae morphology of four Trachelomonas species from the Culture Collection of Algae at Göttingen University (SAG) were studied with and without acetolysis treatment. The experiment demonstrates a strong dissolution under acetolysis of the three species T. hispida, T. lefévrei, T. zorensis and a reduction in the loricae length by T. similis. In the Holocene records, Trachelomonas can be found in non-acetolyzed samples, occurring together with other eutrophication indicators such as cyanobacteria and ciliate Codonella cratera. A review of recent algological literature supports Trachelomonas being a good indicator of organic pollution.

Effects of medium composition on the growth and lipid production of microplasmodia of Physarum polycephalum.

Physarum polycephalum is a plasmodial slime mold. One of the trophic stages in the life cycle of this organism is a plasmodium. In submerged culture, plasmodia are fragmented into microplasmodia. The latter both lack cell walls and are capable of rapid growth. There has been limited information on the effects of medium composition on the growth and lipid accumulation of microplasmodia. In this study, optimization of medium components by response surface methodology showed that tryptone and yeast extract concentrations had the most significant effects on lipid and biomass production; significant synergistic interactions between glucose and tryptone concentration on these responses were also recorded. The optimal medium was composed of 20 g/L of glucose, 6.59 g/L of tryptone, and 3.0 g/L of yeast extract. This medium yielded 13.86 g/L of dry biomass and 1.97 g/L of lipids. These amounts are threefold higher than those of the American Type Culture Collection (ATCC) medium. In addition, biomass and lipid production reached maximal values between only 4 and 5 days. Fatty acid compositions analysis by gas chromatography-mass spectrometer (GC-MS) revealed that P. polycephalum lipids consisted mainly of oleic acid (40.5%), linoleic acid (10%), and octadecynoic (15.8%). This is the first report on the fatty acid composition of P. polycephalum microplasmodia. These results suggest that the biomass of microplasmodia could be used as a source of material for direct conversion into biodiesel because of the absence of cell walls or it could also be used as a supplemental source of beneficial fatty acids for humans, albeit with some further evaluation needed.

Evaluation of the sensitivity to chlorhexidine, voriconazole and itraconazole of T4 genotype Acanthamoeba isolated from Mexico

Free-living amoebae of the genus Acanthamoeba are the etiological agents of cutaneous lesions, granulomatous amoebic encephalitis (GAE) and amoebic keratitis (AK), which are chronic infections with poor prognosis if not diagnosed promptly. Currently, there is no optimal therapeutic scheme to eradicate the pathologies these protozoa cause. In this study we report the morphological and molecular identification of three species of the genus Acanthamoeba, belonging to T4 group; A. polyphaga isolated from the corneal ulcer of a patient sample of AK case; A. castellanii isolated from the contact lens of an AK patient and A. palestinensis obtained from a soil sample. The in vitro activity of chlorhexidine, itraconazole and voriconazole drugs against trophic stage was also evaluated through a colorimetric assay based on the oxidation-reduction of alamar blue. The strains in the study were sensitive to the evaluated drugs; although when determining the 50% inhibitory concentration (IC50) statistically significant differences were observed. A. castellanii showed to be highly sensitive to voriconazole (0.66 ± 0.13 μM) but the least sensitive to chlorhexidine and itraconazole (8.61 ± 1.63 and 20.14 ± 4.93 μM, respectively), A. palestinensis showed the highest sensitivity to itraconazole (0.502 ± 0.11 μM) and A. polyphaga expressed moderate sensitivity to chlorhexidine and itraconazole and lower sensitivity to voriconazole (10.10 ± 2.21 μM). These results showed that species of the genus Acanthamoeba express different sensitivity to the tested drugs, which could explain the problems surrounding the establishment of a treatment of choice in the infections caused by these amoebae. We consider that although chlorhexidine and itraconazole show good activity on these amoebae and have been used in cases of AK in Mexico with acceptable results, voriconazole should be considered as the first therapeutic option of future Acanthamoeba infections that will be diagnosed in our country.

Life Cycle, Ultrastructure, and Phylogeny of New Diplonemids and Their Endosymbiotic Bacteria.

ABSTRACTDiplonemids represent a hyperdiverse and abundant yet poorly studied group of marine protists. Here we describe two new members of the genus Diplonema (Diplonemea, Euglenozoa), Diplonema japonicum sp. nov. and Diplonema aggregatum sp. nov., based on life cycle, morphology, and 18S rRNA gene sequences. Along with euglenozoan apomorphies, they contain several unique features. Their life cycle is complex, consisting of a trophic stage that is, following the depletion of nutrients, transformed into a sessile stage and subsequently into a swimming stage. The latter two stages are characterized by the presence of tubular extrusomes and the emergence of a paraflagellar rod, the supportive structure of the flagellum, which is prominently lacking in the trophic stage. These two stages also differ dramatically in motility and flagellar size. Both diplonemid species host endosymbiotic bacteria that are closely related to each other and constitute a novel branch within Holosporales, for which a new genus, “Candidatus Cytomitobacter” gen. nov., has been established. Remarkably, the number of endosymbionts in the cytoplasm varies significantly, as does their localization within the cell, where they seem to penetrate the mitochondrion, a rare occurrence.

Phylogeny and Morphology of New Diplonemids from Japan

Diplonemids were recently found to be the most species-rich group of marine planktonic protists. Based on phylogenetic analysis of 18S rRNA gene sequences and morphological observations, we report the description of new members of the genus Rhynchopus - R. humris sp. n. and R. serpens sp. n., and the establishment of two new genera - Lacrimia gen. n. and Sulcionema gen. n., represented by L. lanifica sp. n. and S. specki sp. n., respectively. In addition, we describe the organism formerly designated as Diplonema sp. 2 (ATCC 50224) as Flectonema neradi gen. n., sp. n. The newly described diplonemids share a common set of traits. Cells are sac-like but variable in shape and size, highly metabolic, and surrounded by a naked cell membrane, which is supported by a tightly packed corset of microtubules. They carry a single highly reticulated peripheral mitochondrion containing a large amount of mitochondrial DNA, with lamellar cristae. The cytopharyngeal complex and flagellar pocket are contiguous and have separate openings. Two parallel flagella are inserted sub-apically into a pronounced flagellar pocket. Rhynchopus species have their flagella concealed in trophic stages and fully developed in swimming stages, while they permanently protrude in all other known diplonemid species.

Single-cell genomics of multiple uncultured stramenopiles reveals underestimated functional diversity across oceans

Single-celled eukaryotes (protists) are critical players in global biogeochemical cycling of nutrients and energy in the oceans. While their roles as primary producers and grazers are well appreciated, other aspects of their life histories remain obscure due to challenges in culturing and sequencing their natural diversity. Here, we exploit single-cell genomics and metagenomics data from the circumglobal Tara Oceans expedition to analyze the genome content and apparent oceanic distribution of seven prevalent lineages of uncultured heterotrophic stramenopiles. Based on the available data, each sequenced genome or genotype appears to have a specific oceanic distribution, principally correlated with water temperature and depth. The genome content provides hypotheses for specialization in terms of cell motility, food spectra, and trophic stages, including the potential impact on their lifestyles of horizontal gene transfer from prokaryotes. Our results support the idea that prominent heterotrophic marine protists perform diverse functions in ocean ecology.

Biological activities and chemical compositions of slime tracks and crude exopolysaccharides isolated from plasmodia of Physarum polycephalum and Physarella oblonga

BackgroundThe myxomycetes derive their common name (slime molds) from the multinucleate trophic stage (plasmodium) in the life cycle, which typically produces a noticeable amount of slimy materials, some of which is normally left behind as a “slime track” as the plasmodium migrates over the surface of a particular substrate. The study reported herein apparently represents the first attempt to investigate the chemical composition and biological activities of slime tracks and the exopolysaccharides (EPS) which cover the surface of the plasmodia of Physarum polycephalum and Physarella oblonga.ResultsChemical analyses indicated that the slime tracks and samples of the EPS consist largely of carbohydrates, proteins and various sulphate groups. Galactose, glucose and rhamnose are the monomers of the cabohydrates present. The slime tracks of both species and the EPS of Phy. oblonga contained rhamnose, but the EPS of Ph. polycephalum had glucose as the major monomer. In term of biological activities, the slime tracks displayed no antimicrobial activity, low anticancer activity and only moderate antioxidant activity. However, EPSs from both species showed remarkable antimicrobial activities, especially toward Candida albicans (zone of inhibition ≥20 mm). Minimum inhibitory concentrations of this fungus were found to be 2560 μg/mL and 1280 μg/mL for EPS from Phy. oblonga and Ph. polycephalum, respectively. These EPS samples also showed moderate antioxidant activities. However, they both displayed cytotoxicity towards MCF-7 and HepG2 cancer cells. Notably, EPS isolated from the plasmodium of Phy. oblonga inhibited the cell growth of MCF-7 and HepG2 at the half inhibitory concentration (IC50) of 1.22 and 1.11 mg/mL, respectively.ConclusionsEPS from Ph. polycephalum plasmodium could be a potential source of antifungal compounds, and EPS from Phy. oblonga could be a potential source of anticancer compounds.

Variation in the SSUrDNA of the Genus Protostelium Leads to a New Phylogenetic Understanding of the Genus and of the Species Concept for Protostelium mycophaga (Protosteliida, Amoebozoa).

Members of the genus Protostelium (including P.mycophaga, P.nocturnum, and P.okumukumu) are protosteloid amoebae commonly found in terrestrial habitats on dead plant matter. They, along with the closely allied nominal genus Planoprotostelium, containing the single species Pl.aurantium, all have an amoeboid trophic stage with acutely pointed subpseudopodia and orange lipid droplets in the granuloplasm. These amoebae form stalked fruiting bodies topped with a single, usually deciduous spore. The species are identified based on their fruiting body morphologies except for Pl.aurantium which looks similar to P.mycophaga in fruiting morphology, but has amoebae that can make flagella in liquid medium. We built phylogenetic trees using nuclear small subunit ribosomal DNA sequences of 35 isolates from the genera Protostelium and Planoprotostelium and found that (1) the nonflagellated P.nocturnum and P.okumukumu branch basally in the genus Protostelium, (2) the flagellate, Pl.aurantium falls within the genus Protostelium in a monophyletic clade with the nominal variety, P.mycophaga var. crassipes, (3) the cultures initially identified as Protostelium mycophaga can be divided into at least three morphologically recognizable taxa, P.aurantium n. comb., P.apiculatum n. sp., and P.m.rodmani n. subsp., as well as a paraphyletic assemblage that includes the remainder of the P.mycophaga morphotype. These findings have implications for understanding the ecology, evolution, and diversity of these amoeboid organisms and for using these amoebae as models for other amoeboid groups.

The Trophic Life Cycle Stage of the Opportunistic Fungal Pathogen Pneumocystis murina Hinders the Ability of Dendritic Cells To Stimulate CD4+ T Cell Responses.

The life cycle of the opportunistic fungal pathogen Pneumocystis murina consists of a trophic stage and an ascus-like cystic stage. Infection with the cyst stage induces proinflammatory immune responses, while trophic forms suppress the cytokine response to multiple pathogen-associated molecular patterns (PAMPs), including β-glucan. A targeted gene expression assay was used to evaluate the dendritic cell response following stimulation with trophic forms alone, with a normal mixture of trophic forms and cysts, or with β-glucan. We demonstrate that stimulation with trophic forms downregulated the expression of multiple genes normally associated with the response to infection, including genes encoding transcription factors. Trophic forms also suppressed the expression of genes related to antigen processing and presentation, including the gene encoding the major histocompatibility complex (MHC) class II transactivator, CIITA. Stimulation of dendritic cells with trophic forms, but not a mixture of trophic forms and cysts, reduced the expression of MHC class II and the costimulatory molecule CD40 on the surface of the cells. These defects in the expression of MHC class II and costimulatory molecules corresponded with a reduced capacity for trophic form-loaded dendritic cells to stimulate CD4+ T cell proliferation and polarization. These data are consistent with the delayed innate and adaptive responses previously observed in immunocompetent mice inoculated with trophic forms compared to responses in mice inoculated with a mixture of trophic forms and cysts. We propose that trophic forms broadly inhibit the ability of dendritic cells to fulfill their role as antigen-presenting cells.

Water Quality and Self-purification Capacity Assessment of Snagov Lake

The aim of this paper is to identify the spatial and temporal distribution of chemical and physical parameters that characterize the water quality, the trophic state and the self-purification capacity assessment of Snagov Lake. The Snagov Lake is a natural lake located at 25-30 km North from Romania�s capital, Bucharest. The study was conducted during a five years period, from April 2010 until October 2014. The measurements used (temperature, pH, dissolved oxygen, transparency, chlorophyll-a, total phosphorus, TN/TP ratio) are presented in the form of spatial and temporal evolutions. For self-purification identification the aerobic mineralization degree, biological depuration factor and TN/TP ratio were used. The trophic stage of Snagov Lake in the range and in all the points of sampling is eutrophic�hipereutrophic for all the parameters used for assessment, excepting several short periods of time (fall of 2010, spring and fall of 2011) when the lake was in mesotrophic state.

The Life Cycle of Didymium laxifilum and Physarum album on Oat Agar Culture.

The plasmodial slime molds is the largest group in the phylum Amoebozoa. Its life cycle includes the plasmodial trophic stage and the spore-bearing fruiting bodies. However, only a few species have their complete life cycle known in details so far. This study is the first reporting the morphogenesis of Didymium laxifilum and Physarum album. Spores, from field-collected sporangia, were incubated into hanging drop cultures for viewing germination and axenic oat agar plates for viewing plasmodial development and sporulation. The spores of D.laxifilum and P.album germinated by method of V-shape split and minute pore, respectively. The amoeboflagellates, released from spores, were observed in water film. The phaneroplasmodia of two species developed into a number of sporangia by subhypothallic type on oat agar culture. The main interspecific difference of morphogenesis was also discussed.

Fiddler crabs (Uca spp.) as model hosts for laboratory infections of Hematodinium perezi

The parasitic dinoflagellate, Hematodinium perezi, negatively impacts the commercially important blue crab, Callinectes sapidus. The parasite is a host generalist, but it has not been reported from littoral fiddler crabs living within a few meters of habitat known to harbor infected blue crabs. In the first study, populations of three species of fiddler crab were screened for natural infections. The infection status of field-collected and lab-inoculated crabs was determined by screening fresh hemolymph with a 0.3% neutral red solution. Fiddler crabs were collected by hand in an area adjacent to where infected blue crabs were commonly collected. None of the 431 fiddlers had natural infections. In two separate studies, three species of fiddler crabs, Uca minax, U. pugnax, and U. pugilator, were evaluated for their susceptibility to H. perezi via inoculation of trophic stages. Uca minax inoculated with 10,000 cells of H. perezi were monitored for progression of the parasite. During hemolymph screenings of disease progression, filamentous trophonts, ameboid trophonts, and clump colonies were observed, indicative of active infections. In the second study, the minimum infective dose in U. minax was investigated. Fiddler crabs were inoculated with 0, 100, 1000, or 10,000 cells per crab. The minimum dose was determined to be approximately 1000 ameboid trophonts per crab. All three species of fiddler crab were susceptible to H. perezi via inoculation. The parasite was serially transferred from fiddler crabs to blue crabs without loss of infectivity. Survival studies indicated similar progression patterns to those observed in blue crabs. Based on our results fiddler crabs can serve as a laboratory model for investigating H. perezi infections and may be useful for comparative studies with blue crabs.