Two new genera and three new species of leeches (Hirudinida:Piscicolidae) from New Zealand marine fishes

The marine leech fauna of New Zealand is poorly known and based primarily on studies by Richardson in the 1950s. Three new species have recently been discovered. Dollfusobdella kaikourae n. gen.. n. sp. is described from Kaikoura, New Zealand parasitising pectoral fins of Scorpaena cardinalis, and thornfish, Bovichtus variegatus. It is characterised by a cylindrical body widest at the posterior portion Of the urosome and tapering, gradually to the oral sucker: the total length is not known to exceed 10 mm. The urosome segments are 3-annulate. each with large tubercles dorsally and smaller tubercles ventrally, but lacking Pulsatile vesicles. The reproductive system has five pairs of testisacs and a small bursa. Leporinabdella digglesi n. gen.. n. sp. is described from Manukau Harbour. Auckland, from the body and Mouth of yellowbelly flounder, Rhombosolea leporina. It is characterised by a wide. flat body not known to exceed 10 mm total length and a large caudal sucker. urosome segments are 3-annulate with lateral conical tubercles on each annulus, but lacking Pulsatile vesicles. The reproductive system has five pairs of testisacs and a large bursa. Pontobdella novaezaelandiae n. sp. is described from a single specimen collected near Wellington. It is characterised by a large oral sucker without a fringe and lacking papillae, a moderate-size caudal sucker. and four annuli per segment with large tubercles on the first three annuli

Differential Diagnosis Of Mixed Haplosporidium Costale And Haplosporidium Nelsoni Infections In The Eastern Oyster, Crassostrea Virginica, Using Dna Probes

Haplosporidium costale and Haplosporidium nelsoni are morphologically similar pathogens of the eastern oyster Crassostrea virginica. In the absence of the spore stage, infections of the two species are extremely difficult, if not impossible, to distinguish using traditional light microscopy of stained tissue sections. Species-specific molecular diagnostics were developed for H. costale from the small subunit ribosomal DNA (SSU rDNA) sequence. The polymerase chain reaction (PCR) primers amplified a 557 base pair (bp) region of the H. costale SSU rDNA, but did not amplify DNA from oyster (C. virginica) or from six other haplosporidans (H. nelsoni, H. louisiana, H. lusitanicum, Minchinia teredinis, M. chitonis, or M. tapetis). The DNA probe was used with in sim hybridizations of oyster tissue sections to visualize H. costale plasmodia and prespore stages; it did not hybridize with oyster (C. virginica) or other haplosporidans (H. nelsoni, H. louisiana, or Minchinia teredinis). DNA-based diagnostics for H. costale, in conjunction with molecular tools previously developed for H. nelsoni, have overcome limitations of histological examination. From in situ hybridizations using both probes, some Virginia oysters previously diagnosed with H. costale were found to have mixed infections consisting of approximately 80 to 90% H. costale plasmodia and 10 to 20% H. nelsoni plasmodia, Plasmodia of H. costale were not found in epithelial tissue, only in connective tissue. In addition, use of the DNA probe confirmed the presence of H. costale plasmodia in Virginia oysters collected in the fall, an unprecedented seasonality for an advanced H. costale infection

Development And Verification Of A Model For The Population Dynamics Of The Protistan Parasite, Perkinsus Marinus, Within Its Host, The Eastern Oyster, Crassostrea Virginica, In Chesapeake Bay

A simulation model was developed to investigate the population dynamics of the protistan parasite, Perkinsus marinus, within its host, the eastern oyster, Crassostrea virginica. The main objective was to evaluate the relationship between P. marinus population dynamics and environmental conditions in order to predict the onset and termination of P. marinus epizootics in Chesapeake Bay oyster populations. Information derived from laboratory experiments and from direct field observations of P. marinus dynamics in the James River for the years 1990 to 1993 was utilized for model development. The individual-based model, which is driven by temperature and salinity, tracks the average within-host parasite density at a daily time step. The model was verified against monthly field observations of parasite abundance for the years 1994 to 1999 at three oyster bars located along a 0-20-ppt salinity gradient in the James River, Virginia. Simulated populations exhibited a distinct seasonal periodicity with annual density maximums and minimums occurring in October and May, respectively. Parasite abundance decreased in an upriver direction with decreasing salinity along the salinity gradient. Predicted parasite densities significantly correlated with actual observed densities at all three locations; however, the strength of the association decreased from bar to bar in an upriver direction. Predicted parasite abundance exhibited a dynamic steady state for all three oyster bars during the 6-year time series. Simulations run without the input of a midsummer transmission event resulted in a destabilization and extinction of the parasite from the oyster population located farthest upriver. but the parasite remained enzootic during the six year simulation at the two lower river stations. This suggests that a single transmission event may be sufficient for P. marinus to become enzootic in specific year classes of oyster populations located in moderate to high salinity areas, while periodic transmission events are required for the parasite to persist in low salinity areas. Simulation results suggest that fairly accurate quantitative predictions of P. marinus abundance can be made using in situ temperature and salinity data and a relatively simple model

Use of molecular tools for mollusc disease diagnosis

Recently, an increasing number of research teams arc engaged in developing DNA-based diagnostic techniques for mollusc pathogens. These techniques are slowly moving from development in specialised laboratories for research purposes, to routine application and are expected to find an increasing use in routine disease monitoring programs in mollusc aquaculture and in efforts to prevent the spread of pathogens within and between nations. Considering the probable development and interest in these diagnostic techniques, the potential for wide applications in aquaculture and the inherent problems currently associated with their use, it appears necessary to address these issues

Characterization Of Overwintering Infections Of Perkinsus-Marinus (Apicomplexa) In Chesapeake Bay Oysters

To determine the nature and abundance of over-wintering P. marinus infections, infected oysters (Crassostrea virginica) collected from the upper James River, VA, were placed in a tray and suspended from a pier in the lower York River, VA in November 1991. Every six weeks through May 1992 oysters (n = 25) were removed from the tray, examined for P. marinus by hemolymph culture in fluid thioglycollate medium (FTM), gradually warmed in individual containers to 25-degrees-C and held for one month. After the incubation period, which permitted the development of very light and/or cryptic parasite stages to detectable levels, the oysters were reanalyzed for P. marinus by both hemolymph and tissue cultures in FTM. A second group of 25 oysters from the tray was sacrificed at the initiation of each incubation, diagnosed using FTM cultures of hemolymph and tissue, and examined for cryptic stages using immunoassays. On the basis of FTM assays, prevalence of P. marinus gradually declined from 100% in November 1991 to 32% in May 1992. Incubation of oysters at 25-degrees-C always resulted in an increase of P. marinus prevalence and intensity, suggesting that the parasite was more abundant than initial FTM cultures indicated. Immunoassay diagnosis revealed infections in many of the oysters diagnosed as negative by FTM cultures. Most infections detected by immunoassay were comprised of individual P. marinus meronts within hemocytes in the midgut epithelial lining. Previously unidentified cryptic stages were not observed. Perkinsus marinus appears to overwinter at very low intensities in a high proportion of oysters. Comparison of P. marinus prevalence and intensity in transplanted oysters maintained in the York River to that in oysters monitored at the original James River collection site suggests that salinity may greatly influence overwintering infections. Infection intensity and prevalence declined earlier and to a greater extent at the James River site (4-12 ppt) than at the York River location (19-23 ppt). It appears that the synergistic effect of low temperature and low salinity may be more important in regulating P. marinus epizootics than either factor acting alone

Detection Of Haplosporidium-nelsoni (Haplosporidia, Haplosporidiidae) In Oysters By PCR Amplification

Haplosporidium nelsoni is a protistan pathogen of the eastern oyster Crassostrea virginica, and has contributed to the decline of the oyster population in the Chesapeake Bay. From comparison of the sequence data of the 16S-like rDNA of H. nelsoni with those of Minchinia teredinis and other related organisms, 2 oligonucleotides which were specific to H. nelsoni and suitable for use as PCR primers were identified. These primers amplified a 564 base pair fragment of the small subunit (SSU) rRNA gene of H. nelsoni, but did not amplify genomic oyster DNA or the SSU rRNA genes of the haplosporidians Haplosporidium costale, Haplosporidium louisiana, or M. teredinis. The PCR primers were able to detect the H. nelsoni SSU rDNA from 50 ng of infected oyster genomic DNA or from 10 fg of cloned H. nelsoni SSU rDNA. The ability of the PCR primers to diagnose H. nelsoni-infected oysters was compared to the established techniques of hemolymph settlement analysis in Farley chambers and histological examination from a sample of 20 oysters. Hemolymph settlement analysis detected infection in 10 oysters and histology revealed infections in 11 oysters. PCR amplification of DNA from hemolymph initially detected infections in 15 oysters and reamplification of the PCR products detected an additional 4 infections. PCR amplification is a more sensitive diagnostic assay for H. nelsoni than traditional techniques

Prevalence and distribution of QPX, Quahog Parasite Unknown, in hard clams Mercenaria mercenaria in Virginia, USA

In July 1996, the Virginia Institute of Marine Science initiated a sampling program to examine wild and cultured hard clams Mercenaria mercenaria for QPX, Quahog Parasite Unknown, a protistan parasite associated with severe mortalities of hard clams in localized areas in maritime Canada and Massachusetts, USA. The sampling program set out to seasonally monitor wild clams from one site, James River, Virginia, and cultured clams from 2 sites, Chincoteague Bay and Mattawoman Creek, Virginia. Histological examination of initial samples revealed 8% prevalence of the parasite in 1-2 yr old cultured clams in Chincoteague Bay. This is the first documentation of QPX in Virginia. To ascertain the distribution of the parasite in Virginia, the survey was expanded between August 1996 and July 1997 to include 16 additional sites. A total of 1305 wild and cultured clams was sampled from Chesapeake Bay tributaries and coastal areas where harvest and culture occur. QPX was not found in Chesapeake Bay, but was present in cultured clams from 3 coastal embayments-the original Chincoteague Bay site, Burton Bay and Quinby Inlet. The parasite was found in Chincoteague Bay at each sample period at prevalences ranging from 8 to 48 %. Infections were generally Light to moderate intensity and were most often observed in mantle and gill tissues. The maximum prevalence was observed in May 1997 and coincided with notable clam mortalities. QPX prevalences at the other sites were low, ranging from 4 to 15%. To date QPX has not had a significant impact on Virginia\u27s hard clam fishery and aquaculture industry; however, the presence of the pathogen in 3 of the state\u27s most productive hard clam growout areas warrants continued monitoring and research

Advanced Perkinsus Marinus Infections In Crassostrea Ariakensis Maintained Under Laboratory Conditions

The Suminoe oyster, Crassostrea ariakensis, has been under investigation since the early 1990s for potential use in restoring the commercial harvest or for aquaculture of oysters in the Chesapeake Bay, USA. Initial studies focusing on C. ariakensis documented a significant level of tolerance to the protozoan parasite Perkinsus marinus, a pathogen found in almost all reaches of the Bay and widely acknowledged as one of the main reasons for the decline in the eastern oyster, Crassostrea virginica, harvest since the late 1980s. Crassostrea ariakensis was demonstrated to acquire P. marinus. however infection intensities, as measured using Ray\u27s thioglycollate medium assay indices, generally were found to be light. As part of a series of experiments to study potential impacts on the Chesapeake Bay region of pathogens found in C. ariakensis in Asia, a challenge experiment was conducted to study the pathogenicity of Perkinsus olseni to C. ariakensis. During this study, we observed the acquisition of moderate and heavy infection intensities of P. marinus in triploid C. ariakensis oysters being maintained in the laboratory. Results suggest that there may be some risk of mortality from P. marinus if C. ariakensis is held under stressful conditions at least in hatchery or laboratory settings

An unidentified haplosporidian parasite of bay scallop Argopecten irradians cultured in the Shandong and Liaoning provinces of China

Since 1988 growers of bay scallop Argopecten irradians in China have been experiencing mortality in their cultured stocks. Although poorly documented, mortality apparently began near Qingdao and has since spread to other areas of Shandong and Liaoning provinces. Samples of cultured scallops were collected from several growing areas in these provinces and analyzed by histological methods for pathogens. An unidentified haplosporidian parasite was observed in a high proportion of scallops from two of the stocks examined. Most infections were of low intensity, but one heavy infection was also observed. Only plasmodia stages were observed; they occurred intercellularly in connective tissues throughout the scallops. Plasmodia were spherical to oval, varied from 4.0 to 17.0 mu m in diameter and contained from 2 to 18 nuclei. Absence of spores prevented generic assignment of the parasite. The source and pathogenicity of the haplosporidian could not be assessed without additional research. No other microbial parasites (i.e. rickettsia-like, chlamydia-like or kidney coccidia) were observed in any of the scallops examined

Perkinsus-marinus (Apicomplexa) As A Potential Source Of Oyster Crassostrea-virginica Mortality In Coastal Lagoons Of Tabasco, Mexico

Poorly documented, but apparently sporadic oyster Crassostrea virginica mortality in the coastal lagoons Carmen, Machona and Mecoacan at the southern extreme of the Gulf of Mexico in Tabasco, Mexico, has been attributed by local oystermen to pollution resulting from oil refinery operations. In September 1992 we sampled oysters in these lagoons to investigate the potential for disease-induced mortality from the oyster pathogen Perkinsus marinus. Prevalence of P. marinus was 100% at Lodazal, a high salinity (31 ppt) site in Carmen lagoon and 60% at Rio San Felipe, a low salinity (15 ppt) site. At Los Jimenez, a high salinity (32 ppt) site in Machona lagoon with previous high mortality, prevalence of P. marinus was 90% and weighted prevalence, a measure of intensity, was 3.1, a high value associated with heavy infections and mortality. Samples collected at the Buena Vista aquaculture facility in Mecoacan lagoon revealed 60 to 100% prevalence of P. marinus, although most infections were low intensity. P. marinus is a potential source of oyster mortality in these coastal lagoons; more intensive sampling is necessary to determine the mortality attributable to P. marinus