Occurrence of Perkinsus olseni (Protozoa: Apicomplexa) and other parasites in the venerid commercial clam Pitar rostrata from Uruguay, southwestern Atlantic coast (original) (raw)
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Aquaculture, 1992
Navas, I.[., Castillo. MC.. Vera, P. and Ruiz-Rico, M., 1992. Principal parasites observed in clams, Rudirapesdecussarus (L. ). Rudirapes philippinorum (Adams et Reeve), Venerupispulla~a (Montag") and Venenrpisaureus (Gmelin). from the Huelva coast (SW. Spain ). Aquaculture, 107: 193-199. The most imponant natural beds and cultured zones of clams (Ruditapes dmmarus. R. philippinmm. Venempis pulkwra and K aweus) on the coast of Huelva (S.W. Spain) were sampled in March 1989. The distributions and prevalences of the different observed parasites are presented. Perkinsus arlanricus and Minchinia tapnis were the most worrying parasites detected. P. adanlicuc was the agent observed with the highest distribution and prevalence, showing a special incidence in R.
Journal of Shellfish Research
In Nov 1987, an abnormally high mortality was observed in a depuration plant at Meira, Spain, in clams Ruditapes decussatus, imported from Portugal. Trying to clarify the causes of this mortality, samples were taken from the depuration plant and from several natural beds in different months of the year. A Perkinsus-like organism and haplosporidian plasmodia were detected. The Perkinsus-like organism had the aspect of round "ring" cells with a diameter varying between 3 and 15 mu m. The parasite was present on all the different organs of the clam. The haplosporidian plasmodia were found in the epithelia of the stomach, intestine and, primary and secondary digestive ducts of different clams. The observed plasmodia were mostly spherical to elongated in shape (some of them ameboid), with the longest axis varying between 5.5 and 16 mu m and containing 3 to 16 nuclei.
Journal of Eukaryotic Microbiology, 2002
ABSTRACT Perkinsus atlanticus cultures were established either with trophozoites isolated from fresh gills, with hypnospores isolated from tissues incubated in fluid thioglycollate medium, or directly from infected hemocytes of carpet shell clams Tapes decussatus from Algarve (Southern Portugal), using a culture medium and conditions optimized for Perkinsus marinus. Perkinsus atlanticus isolates were cloned by limiting dilution, and their identity unequivocally established by PCR-based species-specific diagnostic assays, and by sequencing the complete rRNA gene cluster. The rRNA gene cluster is 7.5-kb in length including 5S, IGS, SSU, ITS1, 5.8S, IS2, LSU, and an inter-cluster spacer. rDNA sequences of the P. atlanticus clone were between 98.3–100% identical to P. atlanticus sequences previously obtained from clam tissue (non-clonal) isolates. Based on the IGS sequences available from Perkinsus species, a set of primers was designed to amplify P. atlanticus and the two clonally cultured Perkinsus species (P. marinus and P. andrewsi) currently available from a recognized repository. This Perkinsus“genus-specific” PCR-based assay complements the species-specific assays developed earlier and strengthen the detection of Perkinsus species for which specific detection assays are not yet available.
Aquaculture, 1999
The protozoan parasite Perkinsus atlanticus Azevedo, 1989 causes severe losses among cultured clams, Ruditapes decussatus. This parasite is routinely diagnosed by means of histology or incubation of gills in fluid thioglycollate medium. However, in order to develop models of experimental reproduction of the disease, a procedure for infection intensity evaluation was required. Thus, a diagnostic method has been developed, based on the culture of all clam tissues in fluid thioglycollate medium, followed by sodium hydroxide lysis, and iodine staining of the parasites on cellulose filters. This method was compared with histology. Results suggest that histology is not sensitive enough to detect low levels of infection. The whole-clam culture technique allows detection of low levels or early infection of clams by P. atlanticus. Moreover, this method provides a quantification of infection intensity as number of parasites per gramme wet weight tissue.
Journal of Invertebrate Pathology, 2013
The present work aimed to study the infection by Perkinsus sp. in the mangrove oysters Crassostrea rhizophorae from the estuary of the Paraíba River (Paraíba State, Brazil). Perkinsosis was detected by incubation of oyster gill pieces in Ray's fluid thioglycollate medium. The monthly prevalence values were all above 70%, thus infection was not likely to be a transient event. Perkinsus sp. parasites isolated from eight oysters were propagated in vitro. PCR-RFLP analysis of in vitro cultured cells as well as the sequences of the rDNA ITS region allowed the identification of the in vitro propagated parasites as Perkinsus marinus. Phylogenetic analyses using rDNA ITS region sequences strongly supported the Perkinsus sp. from Paraíba in a monophyletic group with P. marinus. Thus, the results confirmed the species affiliation of Paraíba Perkinsus sp. as P. marinus. This is the first report of P. marinus in Brazil and South America and the first report of P. marinus naturally infecting C. rhizophorae.
A Novel Hard Clam Parasite : Making Sense of a New Finding
2008
During a routine histopathological examination of 180 juvenile hard clams, Mercenaria mercenaria, from a site in Virginia, USA in 2007, we discovered a single individual heavily infected with what appeared to be a haplosporidian parasite. The Haplosporidia include species causing lethal oyster diseases. SEM of spores indicated that the parasite belonged to the genus Minchinia. Sequencing of the SSU rRNA gene confirmed that it is a previously unknown Minchinia species closely related to M. tapetis, a parasite of the European clam, Ruditapes decussatus. Further sampling of clams near the area of the first discovery found prevalences up to 100% using PCR. No detectable parasites were found in routine screening of the same individuals using tissue-section histology with H&E staining. No unusual mortalities have occurred among the sampled groups. PCR analysis of juvenile clams from Florida in 2007, and Massachusetts, New Jersey and North Carolina in early 2008 failed to detect the parasi...
Journal of invertebrate …, 2010
Symbionts and abnormal conditions of razor clam Ensis arcuatus were surveyed in three commercially important natural beds of Galician estuaries (NW Spain). Samples of 15-20 E. arcuatus were collected every 2 months from January 2003 until July 2004 and processed for histological examination. Prokaryote-like colonies, renal coccidians, gregarines, Trichodina sp. ciliates, haplosporidian-like plasmodia, turbelaria, trematode metacercariae, cestode-like larvae and basophilic inclusion bodies were observed in razor clam tissues without causing host damage. Bucephalid digenean sporocysts and germinoma were seen in some samples causing moderate or severe damage to the host depending on the intensity of infection and both could be a cause for concern if prevalence reached epizootic levels in Galician E. arcuatus populations. None of the parasites detected is OIE notifiable and, in general, the commercially exploited beds studied seem to be devoid of serious pathogens.
Diseases of Aquatic Organisms, 2014
The name 'microcells' is frequently used to refer to small-sized unicellular stages of molluscan parasites of the genera Bonamia (Rhizaria, Haplosporidia) and Mikrocytos (Rhizaria). Histological examination of Manila clams Ruditapes philippinarum revealed microcells in the connective tissue of adductor muscle, foot, mantle, gills, siphon and visceral mass. The clams had been collected from 4 beds on the coast of Galicia, Spain. The prevalence of these microcells ranged from 73 to 93% in surface clams and from 3 to 33% in buried clams. However, the detection of brown ring disease signs in clams from every bed prevented us from making the assumption that the microcells alone were responsible for clam mortality. PCR assays using primer pairs designed to detect Bonamia spp. and haplosporidians gave negative results, whereas positive results were obtained with primers for the genus Mikrocytos. A consensus sequence of 1670 bp of the ribosomal gene complex of the microcells was obtained. It contained a section of the 18S region, the whole first internal transcribed spacer, the 5.8S region, the second internal transcribed spacer and a section of the 28S region. Comparison of this sequence with those of M. mackini infecting Crassostrea gigas and Mikrocytos sp. infecting Ostrea edulis showed that the microcells of Galician clams were the most divergent among the compared parasites. This is the first report of a Mikrocytos-like parasite infecting Manila clams. Care must be taken to avoid the spread of this parasite through Manila clam transfers.