Cosmopolitan distribution of Endozoicomonas-like organisms and other intracellular microcolonies of bacteria causing infection in marine molluscs

Intracellular microcolonies of bacteria, in some cases developing large extracellular cysts, have been historically reported infecting a wide diversity of economically important mollusc species worldwide, sometimes associated with severe lesions and mass mortality events. As an effort to characterise those organisms, traditionally named as Rickettsia or Chlamydia -like organisms (RLO/CLO), via international collaboration, 98 samples comprising 20 mollusc species were collected over 10 countries and examined using histology and phylogenetic analysis. A 16S rRNA gene amplicon library-based sequencing showed the presence of different species of Endozoicomonas-like organisms (ELO) in all the mollusc species analysed, infecting primarily gill and digestive glands. Co-infections of ELOs with other intracellular bacteria were also observed. Subsequent phylogenetic analysis of Operational Taxonomic Units (OTU) revealed a novel microbial diversity associated with molluscan RLO/CLOs infection distributed along different taxa, including Spirochaetes phyla, Rickettsiales order, Simkaniaceae family, Mycoplasma and Francisella genera, and sulfur-oxidizing endosymbionts. Sequences like Francisella halioticida/philomiragia and Candidatus Brownia rhizoecola were also obtained. The presence of ELO sequences in the RLO/CLO infection was confirmed by standard PCR, Sanger sequencing, and by in situ hybridisation in a selection of samples. The phylogenetic analysis conducted in this study will allow for further characterization of the microbial community associated with Rickettsia and Chlamydia-like infection in marine molluscs and their correlation with severity of the lesions in order to reveal their role as endosymbionts, commensals or true pathogens.info:eu-repo/semantics/publishedVersio

Fotóforos subcutáneos en el calamar gigante "Dosidicus gigas" (d¿Orbigny, 1835) Cephalopoda: Ommastrephidae)

In Dosidicus gigas small pale yellow ovoid inclusion bodies corresponded to subcutaneous photophores, which were embedded in the mantle muscle, at differing depths. At the histological level the photophores were composed of a photogenic tissue, which stained bright orange with Mallory triple stain. Surrounding it was a vacuolated tissue with numerous blood vessels which also intruded into the lightemitting tissue. Viewed with transmission electron microscopy the photogenic tissue was electron dense and homogeneously finely granular, in close contact with capillaries of the intruding vacuolar connective tissue. Subcutaneous photophores were observed over the whole squid on tentacles, arms, head, mantle and the fins, both dorsally and ventrally. On arms and tentacles the photophores were sparsely located along the axial nerve, and along the outer edge, with the exception of the fourth pair of arms, where the photophores, having the same location, were very numerous, forming an almost continuous row. A yellowgreenish luminescence could be observed on fresh or frozenthawed muscle in a dark room. The subcutaneous light organs of D. gigas have a very similar structure to those described for Sthenoteuthis pteropus. The only difference with S. pteropus is that this latter species has an additional connective tissue capsule around the phototophore. The structure of the photophore of D. gigas is very basic, and is probably the simplest one of the subfamily Ommastrephinae.En Dosidicus gigas se observaron pequeñas inclusiones de color amarillo pálido embebidas a distintas profundidades en el músculo del manto, las que corresponden a fotóforos. A nivel histológico los fotóforos están formados por un tejido fotogenerador, que se tiñe de color naranja intenso con tinción tricrómica de Mallory y un tejido vacuolar, que lo rodea y penetra en éste, con numerosos vasos sanguíneos. Ultraestructuralmente, el tejido fotogenerador es denso a los electrones, homogéneo y finamente granular. Los fotóforos subcutáneos se observaron en todo el calamar, en cabeza, manto, aletas, brazos y tentáculos, por dorsal y ventral. En brazos y tentáculos se observaron escasos fotóforos ubicados a lo largo, tanto del nervio axial, como del borde externo, excepto en el cuarto par de brazos, en que los fotóforos, presentes en las mismas ubicaciones, son mucho más numerosos, formando una hilera casi continua. En trozos de manto fresco o congeladodescongelado se observó una luminiscencia amarillo-verdosa en un cuarto oscuro. Los fotóforos de D. gigas tienen una estructura muy similar a la de Sthenoteuthis pteropus. La única diferencia es que esta última especie tiene una cápsula de tejido conectivo alrededor del fotóforo, ausente en D. gigas. La estructura del fotóforo de D. gigas es muy básica, y probablemente sea la más simple dentro de la subfamilia Ommastrephinae

¿Qué tan sanos son los ostiones (Argopecten purpuratus) de cultivo en Chile? Un catastro histopatológico

Scallop (Argopecten purpuratus) cultivation is an important economic activity in the central-northern region of Chile, and diseases are a permanent concern for farmers and fishing authorities. A one year-long survey was undertaken to find out what parasites and putative pathogens are present in cultivated scallops from three locations: Caldera, Guanaqueros and Tongoy. Ninety adult scallops were sampled from each location, on each season of the year. The soft parts were fixed in Davidson´s fluid, and processed routinely for histology. The prevalence of infection for each parasite and pathologic condition were assessed. Larvae were sampled from three hatcheries and fixed for transmission electron microscopy. The same was done with digestive gland and gill tissues from the first 10 adults of each group sampled for histology. The same parasites and pathologic conditions were found in scallops from the three locations studied: inclusions of rickettsial-like organisms (RLOs) in epithelial digestive gland tubule cells of adults, and in the velar rim of one larva, haemocyte infiltration in gills and digestive gland, two types of granulomas of unknown aetiology in visceral and mantle connective tissues, mineral concretions in kidney, and the protozoan Trichodina sp., a ciliate ectoparasite, on the gills. However, the prevalences of all conditions varied greatly between the three sites and/or seasons. Based on the absence of significant mortalities among cultured scallops at the three sites during the reported survey year, it is concluded that the surveyed scallops were healthy, and that the pathological conditions reported here are generally benign.El cultivo del ostión del Norte (Argopecten purpuratus) es una importante actividad económica en la zona centro-norte de Chile, y las enfermedades son una constante preocupación para los cultivadores y la autoridad pesquera. Se realizó un catastro de un año para detectar qué parásitos o posibles patógenos se encuentran presentes en ostiones cultivados en tres localidades: Caldera, Guanaqueros y Tongoy. Se muestrearon 90 ostiones de cada localidad y estación del año. Se extrajeron las partes blandas y se fijaron en fluido de Davidson, procesándose según la técnica histológica de rutina. Se estableció la prevalencia de infección para cada parásito o cambio patológico encontrado. Se muestrearon larvas de tres centros de cultivo, y se procesaron para microscopía electrónica de transmisión. Lo mismo se hizo con glándula digestiva y branquias de los 10 primeros ostiones de cada grupo muestreado para histología. Se encontraron los mismos parásitos y cambios patológicos en ostiones de las tres localidades estudiadas: Inclusiones con organismos tipo rickettsial en epitelio de túbulos de glándula digestiva de adultos y en el velo de una larva, infiltraciones hemocíticas en glándula digestiva y branquias, dos tipos de granulomas de etiología desconocida, en tejido conectivo visceral y del manto, concreciones minerales en células epiteliales renales y el protozoo ciliado ectoparásito Trichodina sp. en branquias. Sin embargo, la prevalencia de todas las condiciones varió considerablemente entre los sitios y/o entre las estaciones del año. Dada la ausencia de mortalidades significativas de los ostiones de cultivo en los tres sitios durante el año de estudio, se concluye que los ostiones de cultivo se encuentran sanos y que las condiciones patológicas encontradas son en general benignas

Histological survey of four species of cultivated molluscs in Chile susceptible to OIE notifiable diseases

Shellfish cultured in Chile were analyzed to detect the presence of diseases notifiable to OIE (Office International des Epizooties: the World Organization for Animal Health). Tissue samples of the susceptible species, the abalones Haliotis discus hannai, H. rufescens, and oysters Crassostrea gigas, and Ostrea chilensis cultured in Chile were collected in winter and summer. Histological sections were performed of all species; furthermore, tissue from the Chilean oyster (O. chilensis) was processed for transmission electron microscopy (TEM) to describe the Bonamia-like protozoan detected in the haemocytes of some oysters. The only pathogen from the list of notifiable diseases of the OIE was Xenohaliotis californiensis in H. rufescens. This bacterium formed intracellular inclusions in digestive epithelia, mainly in the post-esophagus and digestive gland. The ultrastructural description of the Bonamia -like protozoan shows it is similar in some features and different in others from the species B. ostreae. and B. exitiosa included in the list of notifiable diseases of the OIE.Se examinaron moluscos cultivados en Chile para detectar la presencia de enfermedades de declaración obligada a la OIE (Office International des Epizooties: Organización Mundial de Sanidad Animal). Se tomaron muestras de tejidos, en invierno y en verano, de las especies susceptibles que se cultivan en el país, los abalones Haliotis discus hannai y H. rufescens, y las ostras Crassostrea gigas y Ostrea chilensis. Se realizaron cortes histológicos de todos los moluscos obtenidos y para el caso de ostra chilena, se procesó además tejido para observación en microscopio electrónico de transmisión (MET) para describir al protozoo tipo Bonamia presente en los hemocitos de algunas ostras. El único patógeno de declaración obligada a la OIE que se encontró fue Xenohaliotis californiensis en H. rufescens, bacteria que se encontró formando inclusiones intracelulares en epitelios digestivos, principalmente post-esófago y glándula digestiva. La descripción ultraestructural del protozoo tipo Bonamia sp. indica que se parece en algunos aspectos y difiere en otros, de las especies B. ostreae y B. exitiosa, pertenecientes al listado de enfermedades de moluscos de declaración obligada de la OIE

Morphofunctional characterization of the digestive system in the palm ruff larvae, Seriolella violacea under culture conditions

© 2018 Elsevier B.V. In the present study, the histological changes and digestive enzymatic activity patterns are described during the larval development of palm ruff, Seriolella violacea from hatching up to 50 days after hatching (DAH). At hatching, the digestive tract consisted of an undifferentiated straight tube dorsal to the yolk-sac, which presented alkaline protease activity (trypsin and chymotrypsin) as well as amylase and lipase activities with similar patterns during larval development. At 20 and 23 DAH, histology of the stomach revealed a sac-like shaped organ, with an epithelium that began to differentiate in a cardiac and a pyloric region. Typical histological structures of a stomach were visible at 33 DAH with a concomitant pepsin activity. Gastric glands were clearly visible at 35 DAH, increasing in numbers up to 37 DAH, suggesting a functional stomach at this age. A significant increase in the specific activity of all enzymes including pepsin (except amylase) was obser

Microbiota of the Digestive Gland of Red Abalone (Haliotis rufescens) Is Affected by Withering Syndrome

Withering syndrome (WS), an infectious disease caused by intracellular bacteria Candidatus Xenohaliotis californiensis, has provoked significant economic losses in abalone aquaculture. The pathogen infects gastroenteric epithelia, including digestive gland, disrupting the digestive system and causing a progressive wilting in abalone. Nonetheless, our knowledge about WS implications in digestive gland microbiota, and its role in diseases progress remains largely unknown. This study aims to determine whether digestive gland-associated microbiota differs between healthy red abalone (Haliotis rufescens) and red abalone affected with WS. Using high-throughput sequencing of the V4 region of the 16S rRNA gene, our results revealed differences in microbiota between groups. Bacterial genera, including Mycoplasma, Lactobacillus, Cocleimonas and Tateyamaria were significantly more abundant in healthy abalones, whilst Candidatus Xenohaliotis californiensis and Marinomonas were more abundant in WS-affected abalones. Whilst Mycoplasma was the dominant genus in the healthy group, Candidatus Xenohaliotis californiensis was dominant in the WS group. However, Candidatus Xenohaliotis californiensis was present in two healthy specimens, and thus the Mycoplasma/Candidatus Xenohaliotis californiensis ratio appears to be more determinant in specimens affected with WS. Further research to elucidate the role of digestive gland microbiota ecology in WS pathogenesis is required.Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 120052