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Protozoan parasites of the genus Perkinsus are considered important pathogens responsible for mass mortalities in several mollusk species worldwide. In the present study we describe for the first time a parasite of the genus Perkinsus infecting the mangrove oyster Crassostrea rhizophorae from the Brazilian coast. Prevalence of this parasite was low in the Pacoti River estuary (Ceará, northeast Brazil) and absent in oysters from southern Brazil. Oyster gill and rectum tissues incubated in Ray's fluid thioglycollate medium (RFTM) revealed the presence of spherical hypnospores (5 to 55 µm diam.). Histological analysis showed the occurrence of typical signet-ring trophozoites and schizonts (3 to 6 µm diam.) infecting connective tissues of several organs and digestive epithelia. PCR assays specific to the genus Perkinsus, followed by cloning and sequencing of the internal transcribed spacer (ITS) region of the ribosomal ribonucleic acid (rRNA) gene complex, confirmed a close phylogenetic relationship between Brazilian Perkinsus sp. and P. beihaiensis infecting Chinese oysters. KEY WORDS: Crassostrea rhizophorae · Mangrove oyster · Perkinsus sp. · Protozoan parasite · PCR-RFLP · rRNA · RFTM · Sporulation Resale or republication not permitted without written consent of the publisherDis Aquat Org 88: [13][14][15][16][17][18][19][20][21][22][23] 2009 eases affecting edible and cultured bivalve species from 2 Brazilian regions. The project was designed to survey parasites among wild and cultivated populations of oysters Crassostrea rhizophorae and C. gigas from Santa Catarina Island and the Pacoti River estuary (Fortaleza, in the state of Ceará, northeast Brazil). The results provide data on distributions of pathogens and on host susceptibilities to pathogens, which will qualify further monitoring programs, help avoid disease transfers from infected populations, and inform efforts to keep unaffected areas parasite-free.The first described parasite of the genus Perkinsus was P. marinus (Mackin et al. 1950), which was identified as being responsible for mortality outbreaks among Crassostrea virginica oyster stocks from Louisiana, USA. It was first described as Dermocystidium marinum, based partly on characteristics of hypertrophic hypnospores and zoosporangia that enlarge among infected oyster tissues when they are incubated in a high-salt formulation of Ray's fluid thioglycollate medium (RFTM) (Ray 1952). Since that time, diverse Perkinsus spp. have been reported to infect many important commercially cultured mollusk species worldwide.Perkinsus olseni was first described as a pathogen of Australian abalone Haliotis ruber (Lester & Davis 1981). Azevedo (1989) described the species P. atlanticus infecting the carpet shell clam Ruditapes decussatus in Portugal. P. olseni, which is currently synonymous with P. atlanticus, has wide geographic and host ranges. It has subsequently been reported in other bivalve species, such as Pitar rostrata from Uruguay (Cremonte et al. 2005) and R. philippinarum, Venerupis pullast...

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The mangrove oyster, Crassostrea rhizophorae (Bivalvia, Ostreidae) is commonly collected by fisherwomen in the estuaries of the Ceará State (CE), Northeastern Brazil. Despite the socioeconomic importance of this natural resource, there are few studies on the health of the oysters in this region. This study aimed to survey pathological changes in the mangrove oyster C. rhizophorae in the estuary of the Pacoti River, CE. Adult oysters were collected in August 2008 (N=450) and December 2009 (N=450) at three sites of the Pacoti estuary and in 2010 (N=600) samplings were done quarterly at one site which has showed the higher prevalence de Perkinsus. Macroscopical and histological analyses were used to evaluate pathological changes, Ray's Fluid Thioglycollate Medium (RFTM) to detect Perkinsus spp. and polymerase chain reactions (PCR) and DNA sequencing to identify Perkinsus species. In 2009, RFTM assay detected Perkinsus sp. infecting the tissues of C. rhizophorae with low prevalences of 1.3%, 6.7% e 7.3% in sites 1, 2 and 3, respectively, and in 2010, in site 3, prevalence was 2% (12 of 600 oysters). PCR did not confirm any positive case in 2009 and only 5 in 2010. The phylogenetic analyses strongly indicate that the Perkinsus species infecting oysters C. rhizophorae of this study belongs to Perkinsus beihaiensis. The histology confirmed 11 cases of Perkinsus sp. infecting the C. rhizophorae in 2009, and only two cases in 2010. Nematopsis sp. was the protozoan observed with greater prevalence (up 96.7%). Other found protozoa were: Trichodina, Sphenophrya, Ancistrocoma - like and an unknown ovarian parasite. The metazoa found were the polychaete Polydora with high prevalences, a turbellarian, possibly of the genus Urastoma, an unidentified digenean metacercariae and larvae of cestode Tylocephalum. A continuous monitoring of diseases in bivalves from this natural population is recommended, since the phylogenetic analyses indicate the occurrence of P. beihaiensis infecting oysters C. rhizophorae whose pathogenic potential is unknown.

Mangrove oysters Crassostrea rhizophorae were sampled monthly in the estuary of Jaguaribe River, on the east coast of Ceará State, Brazil, between August, 2000 and December, 2001, making up 170 individuals. The water temperature varied from 26 to 30 °C and salinity from 21 to 42‰. The animals' size ranged from 3.4 to 7.2 cm height. Macroscopical and histopathological analyses were carried out in the oysters' tissues. The histological exams showed protozoans and metazoans of genera Nematopsis and Tylocephalum, respectively. Nematopsis prevalence varied from 60 to 100% and it was higher in the gills and mantle. The oocysts presented a mean size of 11.5 µm (±1.32) length and 9.1 µm (±1.06) width (n = 30), up to 3 oocysts/phagocyte having been observed. Several animals presented focal hemocitical reaction.

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