Parasitic Dinoflagellate Research Articles

Dinoflagellate infections of Favella panamensis from two North American estuaries

Favella panamensis Kofoid and Campbell, 1929 is seasonally abundant in meso- to polyhaline waters of Chesapeake Bay and Indian River, Florida, USA, where it reaches densities of 103 cells l-1. During the summers of 1986–1992. F. panamensis populations of the two estuaries were commonly infected by the parasitic dinoflagellate Duboscquella aspida Cachon, 1964. The intracellular phase of the parasite reached maturity in ∼21 h (30 °C) and consumed ∼35% of the host's biomass. Infections were not typically lethal to F. panamensis, but sometimes forced the host from its lorica. Several D. aspida were found in the cytoplasm of many hosts, and the number of parasites infection-1 was directly related to infection level. Parasite prevalence averaged 24.0 and 11.5% with mean number of parasites infection-1 being 1.5 and 1.3 for Chesapeake Bay and Indian River samples, respectively. D. aspida was estimated to remove up to 68% of host standing stock d-1 with a mean of ∼10% for all samples. The average impact of parasitism on F. panamensis populations was somewhat less than would be expected from copepod grazing.

The parasitic dinoflagellates of marine crustaceans

Parasitic dinoflagellates have recently emerged as significant disease agents of commercially important crustaceans. For example, epizootics of Hematodinium have seriously affected certain crab and lobster fisheries. The parasitic dinoflagellates of crustaceans are, however, relatively unknown. Marine crustaceans are parasitized by two orders of dinoflagellates: the Blastodinida and the Syndinida. Crustaceans are also parasitized by the Paradinida and the Ellobiopsidae, taxa that have close historical ties and possible taxonomic affinities with the dinoflagellates. The taxonomy and life history patterns of the different parasitic species are largely dictated by their host-parasite relationships. For example, sporulation in the blastodinids occurs internally but is completed externally with the expulsion of spores via the anus of the host. The egg-parasitic chytriodinids sporulate externally after destroying their host egg. The tissue-dwelling syndinids have plasmodia that sporulate internally and generally kill their hosts upon the expulsion of the dinospores. Unfortunately, complete life cycles have not been elucidated for any of the parasitic forms, hence characteristics of the life cycles must be applied cautiously to the systematics of the taxa. For example, gamogony and the presence of resting cysts are only known from a few species; they probably occur in most species. Further work on the life cycles of the parasitic dinoflagellates of crustaceans should concentrate on establishing the life cycles of representative species from each order or family. Parasitic dinoflagellates infect copepods, amphipods, mysids, euphausiids, and decapods. Their pathogenicity varies with their invasiveness in the host. The gut-dwelling blastodinids are relatively benign, while the chytriodinids kill their host egg. Members of the pervasive Syndinida and Paradinida are overtly pathogenic and insidiously ramify throughout the hemal sinuses and organs of their hosts. Members of the Ellobiopsidae vary from the commensal Ellobiocystis to the overtly parasitic Thalassomyces. Host castration and feminization are common pathologic results of infection by these parasites. The severity of the castration is dependent upon the invasiveness of the parasitic species and the duration of the infection, while the degree of feminization is related to the stage at which the host acquires the infection. Most of the parasitic dinoflagellates occur in epizootics in their host populations. Recent epizootics of Hematodinium spp. have had severe effects on crustacean fisheries in Alaska, Virginia, and Scotland, and may potentially result in changes to the benthic communities of the hosts. The epizootics are often associated with host-parasite systems that occur in regions with unique hydrological features, such as fjords or poorly draining estuaries with shallow sills. These regions are ideal for the application of a “landscape” ecology approach that could lead to a better understanding of the epizootiology of parasitic dinoflagellates and other marine pathogens.

Hematodinium perezi infections in adult arid juvenile blue crabs Callinectes sapidus from coastal bays of Maryland and Virginia, USA

In coastal bays of Maryland and Virginia, USA, adult and juvenile blue crabs Callinectes sapidus were severely infected with the parasitic dinoflagellate I-lematodinium perezi. Dinoflagellates were observed in the hemocoel of all infected crabs; associated histopathological changes were evident in some tissues. Dinoflagellates could be observed with an inverted microscope through the 5th pleopod of heavily infected juvenile crabs (5 to 29 mm) without invasion. This note documents a high prevalence of H. perezj infections in juvenile blue crabs from coastal bays in Maryland and Virginia. The seasonal infection prevalence cycle reported by previous authors is consistent with observations made during this study.

Scanning electron microscope study of dinospores of Amyloodinium of. ocellatum, a pathogenic dinoflagellate parasite of marine fish, and comments on its relationship to the Peridiniales

Scanning electron microscope study of dinospores of Amyloodinium of. ocellatum, a pathogenic dinoflagellate parasite of marine fish, and comments on its relationship to the Peridiniales

Experimental pond grow-out of red drum, Sciaenops ocellatus, in South Carolina

This study assessed the production potential of red drum, Sciaenops ocellatus, in intensive pond culture. Six 0.1-ha saltwater ponds at the Waddell Mariculture Center were stocked in April 1986 with juvenile red drum (1.7 – 4.3 g) produced from captive South Carolina brood stock. Stocking densities of 7500, 15 000 and 22 500 fingerlings/ha were compared in duplicate ponds. The fish were fed a 38% protein commercial trout diet (Zeigler Bros.). Salinity averaged 28±3 ppt, and mean water exchange rates were 16.4%, 17.5% and 27.4% per day for the 7500, 15 000 and 22 500 fish/ha densities, respectively, during the 18-month study. A 0.75-hp fountain-type aerator was utilized in the two high density ponds during warm weather in year 1 (1986), and 1-hp paddlewheel aerators were used on a near continuous basis in all ponds during year 2 (1987). An infestation of the parasitic dinoflagellate, Amyloodinium, caused complete mortality of fish reared in one of the highest density ponds on day 146, and a dissolved oxygen depletion resulted in an estimated 35% loss in one medium density pond on day 432. At harvest (28 September–5 October 1987), mean fish weights were 1.3, 1.0, and 1.2 kg, respectively, at the three densities. Harvested biomass averaged 8997.5 kg/ha at the 7500 fish/ha density, with a mean survival of 88.7%. Survival, mean fish weight and crop size at harvest for the medium density (15 000 fish/ha) pond affected by low dissolved oxygen levels were 54.7%, 0.9 kg, and 7251.3 kg/ha, respectively. In contrast, fish in the other medium density pond exhibited 94.9% survival, 1.1 kg mean fish weight and 15 011.3 kg/ha at harvest. The single remaining high density (22 500 fish/ha) pond produced 24 082.5 kg/ha of 1.2 kg fish with 90.6% survival. Food conversion averaged 2.43 (range 2.15 – 2.60). The fish were sold whole at pond bank to commercial dealers for $1.65 – 2.75/kg.

Development of an enzyme-linked immunosorbent assay (ELISA) for the detection of antibody to the parasitic dinoflagellate Amyloodinium ocellatum in Oreochromis aureus

An enzyme-linked immunosorbent assay (ELISA) using antibody to affinity-purified Oreochromis aureus immunoglobulin and antigens from the parasitic dinoflagellate Amyloodinium ocellatum was developed. The ELISA was then used to evaluate the immune response of the tilapine fish to immunization with the parasite. Fish immunized with antigens of the dinospore stage, either live or sonicated, produced a specific immune response that was detectable by this ELISA. Combinations of serial dilutions of A. ocellatum antigen and fish anti- A. ocellatum serum were examined to determine which dilutions provided optimal differentiation of seropositive from seronegative fish. Fresh and heat-inactivated serum from both seropositive and seronegative fish produced similar results.

Preliminary results on the seasonality and life cycle of the parasitic dinoflagellate causing bitter crab disease in Alaskan Tanner crabs ( Chionoecetes bairdi)

Tanner crabs ( Chionoecetes bairdi) from the Sullivan Island area of southeast Alaska were sampled for 1 year to determine the prevalence and intensity of the parasitic dinoflagellate which causes bitter crab disease (BCD). The prevalence and intensity of infection were the greatest in the summer, declined in the fall and winter, and increased again in the spring. A possible relationship between softer, newer shells and higher levels of parasitism was also observed. In vivo transmission studies in the laboratory suggested there are several morphologically different forms of the vegetative cell of the BCD dinoflagellate which occur prior to sporulation of the parasite. In addition, it appears that both the two spore types produced by the parasite are infectious by injection and that there is no ploidy difference between the two spore types and the vegetative cell, suggesting that the two spore types may not represent separate sexes. kw] Hematodinium; Chionoecetes bairdi; parasitic dinoflagellate; bitter crab disease; Sullivan Island

Feeding of the carnivorous copepod Euchaeta antarcrica in Antarctic waters

Copepod Euchaeta antarctica stages V and V1 were caught during 24 h sampling programmes in h4arch 1989 at a coastal station in Gerlache S t r a~ t , Antarctic Peninsula, and in January 1990 at an oceanic s ta t~on in the north Weddell Sea. Gut content analyses showed that copepods made up 80 to 90 % of all food Items by number Metridia gerlachei, Calanoides acutus, Euchaeta spp , other large copepods, Oncaea spp , Olthona spp. and other small copepods were the main prey of E. antarctica (V, VI) Large copepods were probably more important as food (on a dry-weight b a s ~ s ) than small copepods. Mean number of prey per E. antarctica (V, VI) was 0.9 and 1.1 at the coastal and the oceanic station, respectively. Copepodids at stage V contamed more prey items (1 3) than adult females (0.5) at the coastal station In March A sample from South Georg~a showed that E antarctica feeds during winter E antarctica lnd~viduals were not eating continuously slnce, in all areas, over 30 O/O of them had empty guts. The parasitic dinoflagellate Blastodln~um sp. was found in the gut of 6 6 % of E. antarctica at the oceanic station. This infection d ~ d not affect the number of food items found in thelr guts.

High mortality in a copepod population caused by a parasitic dinoflagellate

Infection of copepods by parasitic dinoflagellates has been known for many years, but the ecological consequences of this parasitism have been largely neglected. We estimated mortality rates in the copepodParacalanus indicus Wolfenden due to parasitism by the dinoflagellateAtelodinium sp. by applying laboratory mortality rates to a field population of infected copepods in Port Phillip Bay, Australia, sampled in 1982–1985. Adult female copepods were most often infected, with an incidence of 0 to 28.5% (median 6.2%). Stage V female copepodites were less often infected, and males were never infected. The median mortality rate in females was about 7% d−1, or about one-third of total mortality, and the maximum was 41% d−1. The frequent occurrence of dinoflagellate parasitoids in some species of copepod implies an important, species-specific mechanism for the regulation of populations.

A novel association between an endemic stickleback and a parasitic dinoflagellate. 1. Seasonal cycle and host response

We report the first case of a dinoflagellate infection of stickleback (Gasterosteidae), discovered on an endemic population of Gasterosteus that inhabits an acidic bog lake on the Queen Charlotte Islands, western Canada. A major difference between this and other dinoflagellate infections is that the autotrophic vegetative cyst rather than the parasitic trophont is the predominant stage on the fish. During peak infection in July, 99% of the fish were infected, and cysts often covered the entire fish including the eyes. Density of cysts was highest on the dorsal surface of the fish (to 68/mm); this is possibly associated with the photosynthetic ability of the cysts. There were no consistent differences in the infection among sizes classes of fish or between the sexes. Salmonids (Oncorhynchus kisutch and Salvelinus malma), which are uncommon in the lake, also harboured cysts, but at very low densities. Host reponse to the initial infection included extensive epithelial hyperplasia, producing a layer of cells over the entire fish that enclosed the dinoflagellates. Subsequent infections were covered by additional layers of epithelium, resulting in a thick gelatinous coating. Even in cases of extreme infection, the fish exhibited no obvious behavioral indicators of pathological responses to the infection.

Spatial and temporal occurrence of the parasitic dinoflagellate Duboscquella cachoni and its tintinnine host Eutintinnus pectinis in Chesapeake Bay

Eutintinnus pectinis (Kofoid, 1905) Kofoid and Campbell is a seasonally important component of the Chesapeake Bay, USA, microzooplankton. During the summers of 1986 and 1987, E. pectinis populations commonly reached densities well above 103 cells l-1 and were often heavily infected by Duboscquella cachoni Coats, 1988, a lethal parasitic dinoflagellate. The temporal and spatial occurrence of D. cachoni suggests that this parasite has a significant impact on E. pectinis populations and may, under appropriate conditions, regulate host abundance. Infection levels above 10% were frequently encountered and epizootic events with 20 to 50% of host individuals parasitized by dinoflagellates were observed over broad areas. Epizootic infections were usually recorded in regions of the Bay that had high concentrations of E. pectinis, and data for vertical profiles, when integrated with depth, showed a significant positive correlation (p≪0.01) between host abundance and parasite prevalence. However, peak E. pectinis density and maximum levels of parasitism were often not vertically coincident at stations, and a clear relationship between host abundance and parasite prevalence was not evident for data from discrete samples. These vertical distributions and the absence of a correlation between host density and parasite prevalence for discrete samples may reflect death of E. pectinis as epizootics spread through the host population. Bay-wide infection levels averaged 10.4% (±1.73 SE) for eight cruises in 1986 and indicate that parasite-induced mortality removes 7 to 24% of the E. pectinis standing stock per day. Comparison of these values to ingestion rates for copepods on tintinnine ciliates reveals that parasite-induced mortality of E. pectinis is comparable to predation pressure by the dominant mesozooplankton grazers in Chesapeake Bay.

Duboscquella cachoni N. Sp., a Parasitic Dinoflagellate Lethal to Its Tintinnine Host Eutintinnus pectinis1

ABSTRACTThe parasitic dinoflagellate Duboscquella cachoni n. sp. is described from infestations of the tintinnine ciliate Eutintinnus pectinis collected from the Chesapeake Bay, a major North American estuary located on the east coast of the United States. Examination of parasite life history, morphology, and developmental processes reveals that D. cachoni differs from other members of the genus by the structure of the trophont, the pattern of sporogenesis, and spore morphology. Sporogenesis results in the production of either biflagellated macrospores, microspores with a single flagellum, or a cyst‐like stage. The number of spores formed per infestation and their survival outside the host vary with spore type. Infested ciliates are apparently unable to reproduce, and infestations are always fatal to E. pectinis. Aspects of parasite biology and observations of a natural host‐parasite assemblage suggest that D. cachoni may have a significant impact on its host's population dynamics.

Stability and deformation of diatom chloroplasts during food uptake of the parasitic dinoflagellate, Paulsenella (Dinophyta)

Chloroplasts of the diatom, Streptotheca thamesis, are considerably deformed when they pass the feeding tube of the parasitic dinoflagellate, Paulsenella sp. Nevertheless, chloroplasts resume their normal shape and structure inside the food vacuole. Even the chloroplast ER is partially preserved. The feeding tube channel of Paulsenella chaetoceratis is narrow (about 0.2 μm in diameter) and may be very long (generally 100 μm). The feeding tube invades a seta of Chaetoceros decipiens through the apical or a lateral aperture and elongates until reaching the cell body of the host. The host chloroplasts are ruptured when they pass the feeding tube. However, large stacks of thylakoids remain intact. Stability of diatom chloroplasts and thylakoid stacks may be important in plankton research, e.g. using chlorophyll determinations as a measure for biomass production.

Recent developments in pralytic shellfish poisoning research

The finding that Gonyaulax catenella, the organism that produces much of the paralytic shellfish poison (PSP) in the Pacific, undergoes diel vertical migration offers greater insight into the distribution of both the toxic organism and toxicity in shellfish. This insight points to useful avenues of research to develop a predictive model for PSP and suggests modifications of shellfish culturing practices which may improve monitoring for PSP or reduce losses due to PSP. The occurrence of a heavy infestation of G. catenella by a dinoflagellate parasite during the decline of a dense bloom of G. catenella suggests the parasite may play an important role in controlling G. catenella populations and might be useful as a biological control agent when cultured and introduced into certain confined bays.

Studies on Amyloodinium ocellatum (Dinoflagellata) in Mississippi Sound: Natural and Experimental Hosts

Four species of parasitic dinoflagellates have been found to occur naturally on the gills and fins of Mississippi Sound fishes: Amyloodinium ocellatum (Brown 1931) Brown and Hovasse 1946, Oodinium cyprinodontum Lawler 1967, and two undescribed species. Sixteen of 43 species of fishes examined had natural gill infections of A. ocellatum. Seventy-one of 79 species of fishes exposed to A. ocellatum dinospores were susceptible, and succumbed, to the dinoflagellate. Eight did not die even though exposed to numerous dinospores. The most common signs in an infested fish were spasmodic gasping and uncoordinated movements. Trophonts of A. ocellatum were found on the gills, skin, fins, eyes, pseudobranchs, membranes of the branchial cavity and around the teeth; and in the lateral line pits, nasal passages, esophagus, and intestine of experimentally infected fishes. The dinoflagellate causes extensive mortalities of fishes held under closed-system mariculture conditions.

Observations on the mitosis and on the chromosome evolution during the lifecycle of Oodinium, a parasitic dinoflagellate.

The life cycle of the dinoflagellate Oodinium alternates between an ectoparasitic trophic phase and a phase of multiplication as free-living flagellates. The nucleus of the young ectoparasite has rod-like chromosomes similar to those of free-living dinoflagellates. As growth of the trophout proceeds the nucleus becomes increasingly homogeneous. When Oodinium leaves its host, nuclear reorganization processes occur rapidly; they correspond to a peculiar prophase of the first sporogenetic division. The following division stages are similar. A conspicuous fusorial system appears between two archoplasmic areas which are responsible for daughter-chromosome segregation. The nuclear envelope remains intact while the fusorial microtubules are attached at distinct, kinetochore-like structures onto the nucleus. As the chromosomes become more condensed the kinetochore-like formations disappear.

A DESCRIPTION OF HAPLOZOON AXIOTHELLAE N. SP., AN ENDOSYMBIONT OF THE POLYCHAETE AXIOTHELLA RUBROCINCTA12

SUMMARYA new parasitic dinoflagellate, Haplozoon axiothellae sp. nov., is described from the intestine of the marine polychaete Axiothella rubrocincta. The parasites are 40–175 μm long with 2–26 cells arranged in single or double rows. Two cytoplasmic inclusions previously unknown in this genus are described. The first is globular and varies in size, while the second is approximately 2 μm long and peanut‐shaped. The function and composition of the inclusions are unknown. Nuclear structure and karyokinesis are apparently different from those of typical dinoflagellates.

The use of copper sulfate as a cure for fish diseases caused by parasitic dinoflagellates of the genus Oodinium

The use of copper sulfate as a cure for fish diseases caused by parasitic dinoflagellates of the genus Oodinium

A New Parasitic Dinoflagellate from Fresh-Water Fish

A New Parasitic Dinoflagellate from Fresh-Water Fish

Selenocystis foliata (Ray) from Scolelepis fuliginosa Clpde. and its identity with Haplozoon sp.

1. The so-called parasitic dinoflagellate occurring in the gut of the polychaete worm Scolelepis fuliginosa Clpde. is described and is shown to be the sexual phase of the gregarine “Selenidium foliatum” Ray.2. The gametocytes (often very unequal) associate by their posterior ends while in situ. One remains attached and its epimerite is transformed into a foot-like organ serving to attach the gametocyst to the host throughout the rest of development. The gametocyst is elongate and pyriform (26−226 × 9−34 μ) and its formation involves very little alteration in the shape of the gametocytes. Solitary encystment also occurs.3. The first gametocytic nuclear division is described. Forerunners of the gamete nuclei are formed within the nuclear area of the gametocyte. Flagellated isogametes are formed. There is no residuum.4. The spores are spherical, averaging 8·5μ in diameter, the number depending on the size of the cyst enveloping them. When ripe, they contain four or eight spindle-shaped sporozoites 9·4−14 × 2−3·75μ and, in vivo, a central, spherical, refrigent residuum.5. A new genus Selenocystis is proposed for this organism, with S. foliata (Ray) as the type species. Although I have not found its asexual phase, the probability is that it may still be classified among the schizogregarines.