Jaime Montes

Determining culture strategies in populations of the European flat oyster, Ostrea edulis, affected by bonamiosis.

Abstract Bonamiosis affects the viability of oyster culture in Galicia (NW Spain). This study shows the effects of the disease on three oyster populations from hatcheries in different culture areas (Cambados and Bueu) and different origin: stock A [F1], stock B [F2], and stock C [F2]. These stocks were cultured between November 1998 and November 2000 in Cambados and Bueu. In the Cambados area, bonamiosis is considered to be endemic, while the disease does not generally affect Bueu area. Sampling was conducted at 3-month intervals to study prevalence of Bonamia, mortality and growth rates. In the Cambados area, bonamiosis was detected 12 months after beginning culture but in the Bueu area, it was not detected until 24 months after initiating cultures. Our results suggest that there is a relationship between presence of Bonamia ostreae and oyster mortalities, which were observed in the three stocks from Cambados. These mortalities were associated with the culture area (Cambados) and not with stock of oysters. Growth was satisfactory in both areas as oysters reached commercial size (60 mm) 15 months after beginning the cultures. In an area where Bonamia is present, such as Cambados, the oysters should be marketed promptly (after approximately 15–18 months of culture) but in areas where Bonamia is not present, such as Bueu, the oyster farmer can culture oysters over a long period of time, prior to harvest, if necessary.

A revised description of Haplosporidium armoricanum, parasite of Ostrea edulis L. from Galicia, northwestern Spain, with special reference to the spore-wall filaments

Abstract Haplosporidian spores from Ostrea edulis, previously described as Minchinia armoricana, were reexamined by light and electron microscopy. These spores were either free among host cells or enclosed in sporocysts. They contained two long epispore cytoplasm extensions (ECE), each possessing cytoskeletal structures corresponding to the filaments. After lysis and degradation of the ECE, these extensions disappeared and the spores became devoid of membrane-bound extensions. However, 2 long filaments (∼130 μm long) persisted that were closely attached, in opposition to the spore wall, by a bundle of 9–13 fibers each. Thus, we propose a revised description of M. armoricana (=H. armoricana) to confirm its placement in the genus Haplosporidium as H. armoricanum.

Bonamiasis in native flat oysters (Ostrea edulis L.) from two intertidal beds of the Ortigueira estuary (Galicia, N.W. Spain) with different histories of oyster culture

Abstract Suitability for intertidal oyster culture and effects of bonamiasis are considered in a comparison of two areas of the Ortigueira estuary. One of them, Fornelos, is traditionally used for intertidal culture of oysters and it is affected by Bonamia ostreae , whilst in the other, Macelos, oyster culture has never been carried out. Oysters from natural setting of each area were cultured in their respective locations. Bonamiasis was first detected in Fornelos during the 4th month from the beginning of the experiment, when oysters were 15 months old, and caused severe mortalities before oysters could reach the minimum marketable size. At Macelos, the first cases of infection appeared only after 11 months, and this fact allowed oysters to reach marketable size before the occurrence of mass mortalities. Either proximity to Fornelos or the occasional presence of infected oysters at Macelos could be the reason for transmission of bonamiasis to oysters from Macelos. Oysters are susceptible to infection before they are 15 months old. This susceptibility does not depend on the size of oysters of the same age. Infection negatively affects growth and condition of the oysters.

Données sur la parasitose de Bonamia ostreae chez l'huître plate de Galice, côte nord-ouest de l'Espagne

Abstract Two stocks of flat oyster, Ostrea edulis , suspended culture, from the same hatchery, were analysed, in two estuaries of Galicia (north-west Spain). Bonamia ostreae , a parasitic protozoan, was observed; the maximum range of frequency is registered in August (stock A) and in September (stock B); it is inversely proportional to the condition index. The cumulative mortality reaches 82.4% (stock A) and 78.5% (stock B).

Description of Haplosporidium edule n. sp. (Phylum Haplosporidia), a parasite of Cerastoderma edule (Mollusca, Bivalvia) with complex spore ornamentation

A new haplosporidian Haplosporidium edule sp. n. is described from the digestive gland tissue of the cockle Cerastoderma edule collected in Galicia (Northwestern Spain). The fine structure of the spores, mainly their surrounding ornaments attached to the spore wall, are described from light, scanning and transmission electron micrographs. Plasmodial development and sporoblast formation phases of the life cycle were observed. The spores were ovoid to ellipsoidal (3.20 × 2.20 μm) and the apical zone of the wall modified into a complex opercular system covering a circular orifice 0.5–0.8 μm in diameter. The spore wall (0.10–0.12 μm thick) was composed of inner (∼70 nm), middle (∼15 nm) and outer (∼30 nm) layers. The electron-dense material that forms the outer layer was extended into numerous surrounding folds and slender projections (up 38 in number were counted in SEM). The surrounding folds were arranged in parallel and perpendicular to the spore axis. The slender projections were about 1.2 μm (range 0.8–1.5 μm) (n = 50) long with a diameter of about 70–90 nm as measured in SEM and in ultrathin transverse sections. Each projection had a bifurcated tip, with branches about 0.25–0.30 μm in length. The projections emerged from the spore wall among the folds. The taxonomic affinities of the new species are discussed and morphological comparisons made, mainly with the spore ornamentation of other similar species of the same genus.

Comparison of diagnostic techniques to detect the clam pathogen Perkinsus olseni

Perkinsosis in clams in Galicia (NW Spain) is caused by the protozoan parasite Perkinsus olseni Lester & Davis, 1981. We used 5 clam species of commercial interest cultured in Galicia (Ruditapes decussatus, R. philippinarum, Venerupis pullastra, V. rhomboides, and Donax trunculus) to compare various P. olseni diagnostic techniques. Results of a nested PCR assay for the diagnosis of P. olseni were compared to those obtained using 2 classical methods of diagnosis proposed by the World Organisation for Animal Health (OIE), viz. histology and incubation in Rays fluid thioglycollate medium (RFTM). Moreover, the same samples were analyzed by 2 separate research groups. The results obtained by PCR showed high sensitivity and good correlation between research groups. In addition, this method is faster than histopathology and incubation on RFTM and less expensive than histopathology. Moreover, nested PCR requires less specialized training for technicians than histology. Histopathology also showed high specificity and a good correlation between research groups. Results from incubation on RFTM suggest that this method could give divergent results between research groups, particularly in the case of low levels of infection, but it is nevertheless useful for disease-monitoring purposes. PCR is appropriate for rapidly screening large numbers of clams.

Histological survey of Pacific oysters Crassostrea gigas (Thunberg) in Galicia (NW Spain).

In Galicia, there is an increasingly interest among representatives of the oyster industry in the development of Pacific oyster Crassostrea gigas culture. Nevertheless severe mortalities and emerging health problems in this species have been recently reported in European farming areas. A histological survey was performed from 2004 to 2009 to assess health status in both cultured and wild Galician oysters. Different symbiotic organisms and conditions were detected, including viral gametocytic hypertrophy (VGH) which is reported here for first time in Spanish coast. VGH, prokaryote-like colonies and ciliates were observed in oyster tissues without causing host damage. A haplosporidian infection, copepods inducing lesions and a cellular proliferative disorder were detected in some samples causing moderate host damage; their low prevalence suggests these parasites are not a threat for C. gigas in Galicia. None of the parasites detected is OIE (Office International des Epizooties: the World Organization for Animal Health) notifiable. Although the current study did not identify any pathogens or diseases of concern, it provides important prevalence baseline data for future health and epidemiological assessments needed to better understanding the existing and emerging health problems in this species.

Ultrastructural Developmental Cycle of Haplosporidium montforti (Phylum Haplosporidia) in its Farmed Abalone Host, Haliotis tuberculata (Gastropoda)

The sequential developmental cycle of Haplosporidium montforti, a recently described species from farmed abalone Haliotis tuberculata (Gastropoda), was studied. Ornamented and operculated mature spores were electron dense. The nucleus of the uninucleated free cell divided successively, giving rise to multinucleate plasmodia, containing up to 100–120 nuclei. Later, the plasmodia developed into sporonts inside sporocysts with irregular contours. Each of their nuclei gave rise to uninucleate sporoblasts. At the next phase of development, a very irregular membranous group of cisternae began to differentiate in the cytoplasm of each sporoblast, surrounding each nucleus and the adjacent cytoplasm. Each sporoblast differentiated into a spore. This process was characterized by the appearance of dense blisters of amorphous material at the periphery that gradually formed the prespore wall and pre-operculum. Simultaneously, in the endosporoplasm, the spherulosome and several haplosporosomes were formed. During the final phase of the maturation process, the spores became gradually denser, and the endosporoplasmic structures were barely visible.