Optimización del tratamiento térmico para la inducción al desove de Argopecten purpuratus (Mollusca: Bivalvia)

Based on methodologies currently used in commercial hatcheries, four thermic treatments were compared to induce the gametes expulsion of Argopecten purpuratus. The treatments evaluated included: 1) gradual increase in temperature, 2) gradual decrease, 3) 5 °C thermal-shock, 4) 10 °C thermal-shock and 5) control at constant temperature 16 °C. After induction, the number of fertilized oocytes in each treatment was estimated. The results show that a gradual increase in temperature between 16 and 26 °C causes a significantly higher proportion of fertilized oocytes compared to other treatments.

Efecto del biofilm de dos cepas bacterianas nativas sobre el asentamiento de larvas de Argopecten purpuratus

El objetivo de la presente investigación fue aislar, seleccionar y caracterizar genéticamente bacterias nativas de Argopecten purpuratus que, a través de un biofilm, estimulen su asentamiento larval. Conociendo que el asentamiento larval es el principal problema que afronta la reproducción en laboratorio de este molusco, se utilizó un biofilm bacteriano para mejorar porcentualmente la fijación larval. Se aislaron cepas bacterianas nativas del cultivo de A. purpuratus y se caracterizaron taxonómicamente a partir del análisis de las secuencias parciales del gen 16S rARN, amplificadas mediante PCR a cada una de las muestras de ADN extraídas de las cepas bacterianas aisladas. Al analizar las secuencias se identificó a nivel de género tres cepas bacterianas; Oceanobacillus, Bacillus y Pseudomonas. Además, se avaluó la eficiencia de fijación de larvas de A. purpuratus en los biofilms formados por las cepas Oceanobacillus y Bacillus logrando una fijación de 12 y 14%, en tanto que al estar asociadas fue de 37%. Se concluye que la fijación larvaria de A. purpuratus mejora con el biofilm bacteriano compuesto por Oceanobacillus y Bacillus, en comparación con el control, sin uso de bacterias.

Draft Genome Sequence of Streptomyces sp. Strain PAM3C, a Prospective Probiotic Agent Isolated from the Gut of the Bay Scallop, Argopecten purpuratus (Lamarck, 1819)

Several bacterial genera with antagonistic activity against pathogenic organisms have been isolated in pure culture from the gut of the Peruvian scallop, Argopecten purpuratus . One strain shows a broad inhibitory activity against aquaculture pathogenic bacterial strains. In this communication, we announce the draft genome sequence of Streptomyces sp. strain PAM3C.

Metabolic Cost of the Immune Response During Early Ontogeny of the Scallop Argopecten purpuratus

The scallop Argopecten purpuratus is an important resource for Chilean and Peruvian aquaculture. Seed availability from commercial hatcheries is critical due to recurrent massive mortalities associated with bacterial infections, especially during the veliger larval stage. The immune response plays a crucial role in counteracting the effects of such infections, but being energetically costly, it potentially competes with the physiological and morphological changes that occur during early development, which are equally expensive. Consequently, in this study, energy metabolism parameters at the individual and cellular levels, under routine-basal status and after the exposure to the pathogenic strain bacteria (Vibrio splendidus VPAP18), were evaluated during early ontogeny (trochophore, D-veliger, veliger, pediveliger, and early juveniles) of A. purpuratus. The parameters measured were as follows: (1) metabolic demand, determined as oxygen consumption rate and (2) ATP supplying capacity measured by key mitochondrial enzymes activities [citrate synthase (CS), electron transport system (ETS), and ETS/CS ratio, indicative of ATP supplying efficiency], mitochondrial membrane potential (ΔΨm), and mitochondrial density (ρm) using an in vivo image analysis. Data revealed that metabolic demand/capacity varies significantly throughout early development, with trochophores being the most efficient in terms of energy supplying capacity under basal conditions. ATP supplying efficiency decreased linearly with larval development, attaining its lowest level at the pediveliger stage, and increasing markedly in early juveniles. Veliger larvae at basal conditions were inefficient in terms of energy production vs. energy demand (with low ρm, ΔΨm, enzyme activities, and ETS:CS). Post-challenged results suggest that both trochophore and D-veliger would have the necessary energy to support the immune response. However, due to an immature immune system, the immunity of these stages would rely mainly on molecules of parental origin, as suggested by previous studies. On the other hand, post-challenged veliger maintained their metabolic demand but decreased their ATP supplying capacity, whereas pediveliger increased CS activity. Overall, results suggest that veliger larvae exhibit the lowest metabolic capacity to overcome a bacterial challenge, coinciding with previous works, showing a reduced capacity to express immune-related genes. This would result in a higher susceptibility to pathogen infection, potentially explaining the higher mortality rates occurring during A. purpuratus farming.

Eficacia de soluciones salinas modificadas para la supervivencia de plerocercoides Tetraphyllidea de concha de abanico (Argopecten purpuratus)

El objetivo de este estudio fue obtener una solución salina modificada que permita una supervivencia más prolongada para el estudio morfológico de plerocercoides Tetrafilideos de la concha de abanico Argopecten purpuratus. Se evaluaron dos temperaturas: T-1, temperatura ambiente y T-2, temperatura constante de 0.5 °C y cinco soluciones: A = SSF (solución salina fisiológica – SSF – al 0.85%), B = ¼ AM (agua de mar) + ¾ SSF, C = ½ AM+ ½ SSF, D = ¾ AM + ¼ SSF, E = AM. Se utilizaron 100 larvas vivas recién extraídas de gónadas de A. purpuratus (10 por grupo experimental) durante 13 días. La mayor supervivencia se observó en las soluciones B y C del T-1, donde permanecieron vivos cuatro plerocercoides hasta el día 10 y tres hasta el día 12, respectivamente. Con excepción de la solución A, las larvas mantuvieron su actividad y forma normal en el resto de las soluciones hasta el día 6. Este trabajo demuestra que las soluciones salinas usuales (0.75 a 0.9%) pueden no ser óptimas para mantener plerocercoides marinos vivos y que una salinidad que se aproxima al agua de mar es más apropiada.

First Report of Domoic Acid Production from Pseudo-nitzschia multistriata in Paracas Bay (Peru)

The Peruvian sea is one of the most productive ecosystems in the world. Phytoplankton production provides food for fish, mammals, mollusks and birds. This trophic network is affected by the presence of toxic phytoplankton species. In July 2017, samples of phytoplankton were obtained from Paracas Bay, an important zone for scallop (Argopecten purpuratus) aquaculture in Peru. Morphological analysis revealed the presence of the genus Pseudo-nitzschia, which was isolated and cultivated in laboratory conditions. Subsequently, the monoclonal cultures were observed by scanning electron microscopy (SEM), and identified as P. multistriata, based on both the morphological characteristics, and internal transcribed spacers region (ITS2) sequence phylogenetic analysis. Toxin analysis using liquid chromatography (LC) with high-resolution mass spectrometry (HRMS) revealed the presence of domoic acid (DA) with an estimated amount of 0.004 to 0.010 pg cell−1. This is the first report of DA from the coastal waters of Peru and its detection in P. multistriata indicates that it is a potential risk. Based on our results, routine monitoring of this genus should be considered in order to ensure public health.