Pathological changes by Eosinophilic Rickettsia-like organism in Japanese oyster, Crassostrea gigas.

Rickettsia infection in adult Japanese oysters (Crassostrea gigas) was observed in 2015 at San Ignacio Lagoon, Baja California Sur, Mexico and characterized using molecular tools. In the present study, the degree of infection by Eosinophilic Rickettsia-Like Organism (E-RLO), characterized by intracellular inclusions in gill, mantle, labial palps, digestive tract and gonadal ducts, was evaluated using histological methods and was associated with visible injuries on body surface, such as blisters, shell damage and necrosis. Most of the oysters (92.2%) had some type of observable symptoms; 90.2% of all oysters had blisters in the mantle, and all oysters presented with E-RLO in the epithelia of at least one of the analyzed tissues (gills, labial palps, mantle, gonadal ducts and digestive tract). The highest intensity of infection (percent of E-RLO coverage) was observed in the labial palps (18.6%) and the lowest in digestive tract (2.6% of the examined tissue). Oysters with external injuries had higher infection intensities than the oysters without external injuries. Considering the clinical signs (observable symptoms and histological findings), we propose three infective stages of E-RLO disease development, a scale that could be used for early detection.

First record of the nematode Echinocephalus pseudouncinatus (Gnathostomatidae, Spirurida) in an edible, commercial host, the pen shell Atrina maura (Bivalvia: Pinnidae).

We describe a nematode infestation of the Atrina maura, the most valuable pen shell fished in Mexico, for the first time. Observations by Mexican authorities indicated that parasites were found encysted in pen shell gonads. The aims of this study included: (i) to identify the parasite morphologically; (ii) to quantify the infestation in different tissues of the pen shell; and (iii) to establish the seasonal variation in gonadal development. During 2015, 10 to 40 pen shells were randomly collected each month from the same commercial bed, and gonads were preserved and processed histologically to establish the seasonal and monthly frequency of infested gonads. A subsample of 35 pen shells was used to identify the parasite and to characterize the infestation of the muscle, mantle, gonad, and digestive gland tissue components. All tissues were dissected, and parasites were collected, photographed, quantified, and adequately preserved for species identification using scanning electron microscopy. Prevalence, intensity of infestation, abundance and crowding data were analyzed by Quantitative Parasitology software and compared monthly and seasonally using a chi test and analysis of means. Results indicated that all parasites were juvenile (second stage) nematodes, Echinocephalus pseudouncinatus. Parasites were found only in muscle and gonad tissues in both male and female pen shells. Hyperpigmentation was observed in the muscle and atretic oocytes with phagocytosis in the gonads. The frequency of infested gonads was significantly higher during winter but was not related to shell size or sex (p > 0.05). A greater number of pen shells were observed to be infested during December and August and during pen shell spawning and development stages. The highest frequency of infested gonads (40%) occurred in December when the lowest temperature and chlorophyll a concentration were recorded. The effects of the biotic and abiotic parameters on this host-pathogen relationship need further research. This nematode species is related to species that are causal agents of gnathostomiasis, which may constitute a health hazard for raw muscle consumers and could affect the reproductive activity of pen shell.

Fecundidad de la medusa Stomolophus meleagris (Rhizostomeae: Stomolophidae) en el Golfo de California / Stomolophus meleagris fecundity (Rhizostomeae: Stomolophidae) in the Gulf of California

The cannonball jellyfish Stomolophus meleagris is regarded as a fishery resource with high commercial value, but with scarce biological information. With the aim to generate preliminary information on reproductive aspects, the present study analyzes its fecundity, based on the estimated number of vitellogenic oocytes in the gonad; in addition, we evaluated its relationship with the jellyfish body length, diameter and wet weight; and we established the relationship of the gonadosomatic index (IGS) with the jellyfish diameter and length. For this, a total of 30 specimens were collected, measured and weighed in a monthly basis, in Las Guásimas lagoon from January to May 2006. In order to estimate the gonad volume, 60 mature females were analyzed and their gonads were extracted and stained with hematoxylin-eosin. Gonad images from histological preparations were analyzed and the number of vitellogenic and previtellogenic oocytes obtained. We used catch data from The Guásimas for population recruitment analysis, that was estimated with FISAT II. Among results, we found that fecundity increased with jellyfish length, diameter and total wet weight. The lower fecundity rates occured on February and the highest during May (11 873 071 and 37 528 197 millions of vitellogenic oocytes per gonad, respectively). The IGS increased with length and diameter of the specimens, at its maximum value of 3.7% was observed in May. A continuous production of previtellogenic oocytes were observed during the full collection period. The maximum recruitment was observed in July and November (37.50% and 28.01% respectively). The high fecundity observed in S. meleagris, suggests a high population reproductive potential that may support the possibility of an important fishery consolidation on this jellyfish.

La medusa Stomolophus meleagris es considerada un recurso pesquero de alto valor comercial. Debido a la relevancia de conocer aspectos de importancia biológica actualmente desconocidos, el presente trabajo analiza la fecundidad con base en la estimación del número de ovocitos vitelogénicos en la gónada; su relación con la longitud, diámetro y peso húmedo; y la relación del índice gonadosomático (IGS) con su diámetro y longitud. De enero a mayo 2006 se recolectaron 30 ejemplares mensuales que fueron medidos y pesados, de los cuales se analizaron 60 hembras maduras para calcular el volumen de sus gónadas. Se extrajeron las gónadas, se tiñeron con hematoxilina-eosina y se seleccionaron las hembras con madurez gonadal. Mediante la digitalización de imágenes se estimó el número de ovocitos vitelogénicos y previtelogénicos. Se emplearon datos de captura en Las Guásimas para el análisis de reclutamiento poblacional, estimado con FISAT II. La fecundidad se incrementó con la longitud, el diámetro y el peso húmedo total. La menor fecundidad se observó en febrero y la mayor en mayo (11 873 071 y 37 528 197 millones de ovocitos vitelogénico por gónada, respectivamente). El IGS se incrementó con la longitud y diámetro de los ejemplares, con su máximo en mayo de 3.7%. Se observó una producción continua de ovocitos previtelogénicos en todo el periodo de recolecta. El máximo reclutamiento se observó en julio y noviembre (37.50% y 28.01% respectivamente). La alta fecundidad encontrada en S. meleagris sugiere un alto potencial reproductivo para la población y sustenta la posibilidad de la consolidación de una importante pesquería de esta medusa.

[Stomolophus meleagris fecundity (Rhizostomeae: Stomolophidae) in the Gulf of California]. / Fecundidad de la medusa Stomolophus meleagris (Rhizostomeae: Stomolophidae) en el Golfo de California.

The cannonball jellyfish Stomolophus meleagris is regarded as a fishery resource with high commercial value, but with scarce biological information. With the aim to generate preliminary information on reproductive aspects, the present study analyzes its fecundity, based on the estimated number of vitellogenic oocytes in the gonad; in addition, we evaluated its relationship with the jellyfish body length, diameter and wet weight; and we established the relationship of the gonadosomatic index (IGS) with the jellyfish diameter and length. For this, a total of 30 specimens were collected, measured and weighed in a monthly basis, in Las Guásimas lagoon from January to May 2006. In order to estimate the gonad volume, 60 mature females were analyzed and their gonads were extracted and stained with hematoxylin-eosin. Gonad images from histological preparations were analyzed and the number of vitellogenic and previtellogenic oocytes obtained. We used catch data from The Guásimas for population recruitment analysis, that was estimated with FISAT II. Among results, we found that fecundity increased with jellyfish length, diameter and total wet weight. The lower fecundity rates occured on February and the highest during May (11 873 071 and 37 528 197 millions of vitellogenic oocytes per gonad, respectively). The IGS increased with length and diameter of the specimens, at its maximum value of 3.7% was observed in May. A continuous production of previtellogenic oocytes were observed during the full collection period. The maximum recruitment was observed in July and November (37.50% and 28.01% respectively). The high fecundity observed in S meleagris, suggests a high population reproductive potential that may support the possibility of an important fishery consolidation on this jellyfish.

[Lipid variation in oocytes of the jellyfish Stomolophus meleagris (Scyphozoa: Rhizostomeae) from Las Guasimas Lagoon, Mexico, during gonadal development]. / Variación lipídica en los ovocitos de la medusa Stomolophus meleagris (Scyphozoa: Rhizostomeae), durante el desarrollo gonádico, en la laguna Las Guásimas, Sonora, México.

The jellyfish Stomolophus meleagris has potential for commercial exploitation but there is little information on their reproductive biology. This paper seeks to evaluate some biochemical and demographic characteristics of the species. Samples were taken monthly during 2005 and 2006. Jellyfish collected in 2005 were used to describe the characteristics and quantity of oocyte triglycerides and phospholipids with the Sudan black technique, and to ascertain the degree of gonadal development and sex ratio by the hematoxylin-eosin technique. The 2006 jellyfish were used to determine the size at first maturity and protein and total lipids contents. Four stages of development in both sexes were determined, with a continuous gamete development. The highest percentage of mature organisms was recorded in April. The proportion of sexes was 0.7:1.3. We found higher concentrations of triglycerides than phospholipids in the cytoplasm. There was a positive correlation between triglycerides and the diameter of the oocyte. The size at first maturity for both sexes was 105 mm. The highest protein and lipids contents were obtained in April and March respectively.

Variación lipídica en los ovocitos de la medusa Stomolophus meleagris (Scyphozoa: Rhizostomeae), durante el desarrollo gonádico, en la laguna Las Guásimas, Sonora, México

Lipid variation in oocytes of the jellyfish Stomolophus meleagris (Scyphozoa: Rhizostomeae) from Las Guasimas Lagoon, Mexico, during gonadal development. The jellyfish Stomolophus meleagris has potential for commercial exploitation but there is little information on their reproductive biology. This paper seeks to evaluate some biochemical and demographic characteristics of the species. Samples were taken monthly during 2005 and 2006. Jellyfish collected in 2005 were used to describe the characteristics and quantity of oocyte triglycerides and phospholipids with the Sudan black technique, and to ascertain the degree of gonadal development and sex ratio by the hematoxylin-eosin technique. The 2006 jellyfish were used to determine the size at first maturity and protein and total lipids contents. Four stages of development in both sexes were determined, with a continuous gamete development. The highest percentage of mature organisms was recorded in April. The proportion of sexes was 0.7:1.3. We found higher concentrations of triglycerides than phospholipids in the cytoplasm. There was a positive correlation between triglycerides and the diameter of the oocyte. The size at first maturity for both sexes was 105mm. The highest protein and lipids contents were obtained in April and March respectively. Rev. Biol. Trop. 58 (1): 119-130. Epub 2010 March 01.

La medusa S. meleagris, ha mostrado potencial de explotación pero hay escasa información sobre su biología reproductiva. El presente trabajo pretende conocer el contenido de los triglicéridos y fosfolípidos en los ovocitos durante el desarrollo gonadal, así como la proporción de sexos, talla de primera madurez y la concentración de proteínas y lípidos totales en la medusa. Se realizaron muestreos mensuales durante 2005 y 2006. A las medusas recolectadas en 2005, se les aplicó la técnica del sudán negro, para describir las características del ovocito y la cantidad triglicéridos y fosfolípidos y la técnica de hematoxilina-eosina para conocer el grado de desarrollo gonádico y la proporción de sexos. Las medusas del 2006 se emplearon para determinar la talla de primera madurez y el contenido de proteínas y lípidos totales. Se observaron cuatro fases de desarrollo en ambos sexos, con un desarrollo gamético continúo. El mayor porcentaje de organismos maduros se registró en abril. La proporción de sexos fue de 0.7:1.3. Se encontró mayor concentración de triglicéridos que de fosfolípidos en el citoplasma. Se obtuvo una correlación positiva entre triglicéridos y el diámetro del ovocito. La talla de primera madurez para ambos sexos fue de 105 mm. El mayor contenido de proteínas se obtuvo en abril y para lípidos en marzo.