Grafting surgery, a key step in pearl culture process, can trigger physiological, antioxidant, and immune responses in the host mollusk. Adult red abalone (Haliotis rufescens) were subjected to four experimental treatments: (1) anesthesia only (AN); (2) anesthesia plus a surgical incision (IN) in the abdominal wall without mantle grafting; (3) anesthesia, incision, and placement of an autograft (AT); and (4) anesthesia, incision, and placement of an allograft (AL). The control group (CT) consisted of unmanipulated abalone. Hemolymph samples were collected during the recovery phase at 2, 4, 24, and 48 h post-grafting. In both the cell-free hemolymph fraction (CFH) and lysed hemocytes (LH), total protein (TP) content, superoxide dismutase (SOD), catalase (CAT), and myeloperoxidase (MPO) activities, as well as nitric oxide (NO) production and total hemocyte count (THC), were quantified. SOD activity increased across all treatments at 48 h, whereas CAT activity was elevated only in the AL group at 2 and 4 h and in the AT group at 24 and 48 h. THC increased rapidly in the AL group (2 h), followed by increases in the IN and AT groups (4 h), with gradual declines observed by 48 h. Immunological parameters (MPO and NO) were detected primarily in the AL group at nearly all time points. The results of this study demonstrate marked modulation of antioxidant and immunological parameters at both humoral and cellular levels in response to grafting, particularly in the AL and AT groups. Importantly, the immunological activation observed in the AL group was confined to the early post-operative period (48 h) and did not compromise survival, as no mortality was recorded in any experimental treatment. These findings support the feasibility of allografting as part of pearl culture protocols in H. rufescens.

This study reports the survival, hemocyte count and physiological response indicators of pearl oysters Pteria sterna and Pinctada mazatlanica seeded with allografts and xenografts for pearl culture. Two treatments of oysters receiving an allograft (both donor and host were Pt. sterna) or a xenograft (donor was Pt. sterna and host was P. mazatlanica) were compared against two control groups of unseeded oysters (allografts and xenografts) at 0, 0.5, 2, 24, and 72 h. While survival was not affected by any particular treatment, the number of circulating hemocytes was inversely proportional in both species; it did not vary in Pt. sterna after allografting from t0 to 2 h, but then gradually increased and reached a 4-fold peak at 72 h that differed significantly from its control group and t0. In P. mazatlanica, the hemocyte count increased significantly (3-fold) at 0.5 h after xenografting, but then gradually decreased to equal the value of its control group and t0 at 72 h. In Pt. sterna, glycogen and mucopolysaccharide indices decreased >50 % at 2 h and gradually returned to the initial value at 72 h. In contrast, neither index varied significantly in P. mazatlanica, indicating almost no use of energy stores to compensate for the effects of xenografting, as well as little mucus production due to tissue irritation, compared to allografting in Pt. sterna. The lipofuscin index followed a relatively stable pattern over time in treatments A and X and changes with respect to their control groups CA and CX were not significant up to 72 h. Our results indicate that P. mazatlanica responded significantly faster to xenografting and wound healing than Pt. sterna to allografting, and may be a viable host to receive Pt. sterna xenografts. This could contribute to improve pearl yield and quality in Pt. sterna.

Abalone pearl farming is an aquaculture activity with great potential for future growth and diversification of the global pearl sector, which has been dominated for decades by pearls of marine pearl oysters of the genus Pinctada. Despite this potential, there is a significant lack of knowledge regarding methods for nucleus (bead) seeding and the process of pearl formation in abalone, compared to the well-studied pearl oyster model. To address this problem, this review first compares the main anatomical differences and similarities between both groups of mollusks, particularly those associated with the structure and role of mantle tissue on the synthesis of CaCO3 compounds that integrate the inner nacreous layer. The iridescence (orient) and color properties of nacre in a cultured pearl is particularly related to the microstructure of aragonite crystals during biomineralization in each mollusk group. We then analyze the advantages and disadvantages of the adoption in abalone of methods originally developed for pearl oysters to produce bead-seeded pearls and half-pearls (or mabé pearls). For the red abalone Haliotis rufescens in particular, updated information on commercial production of both bead-seeded and mabé pearls is provided as a case of success for Latin America (Chile). Finally, the current status and future prospects for abalone pearl farming are discussed, assessing technology gaps and challenges to be addressed for the pearl sector to achieve its full potential, particularly for Latin America.

Este es el primer estudio que caracteriza la ultraestructura de la espermatogénesis en la almeja mano de león Nodipecten subnodosus, discutiendo algunas implicaciones de la morfología y función celular en la sistemática de la familia Pectinidae. Se recolectaron muestras de gónadas mensualmente durante un ciclo anual y se procesaron utilizando técnicas MET convencionales. Se determinó el número y el área de células en desarrollo que se presentaron durante la espermatocitogénesis, la meiosis y la espermiogénesis. En general, la disposición de las células en desarrollo fue concéntrica y la mayoría de los cambios celulares que comprenden la transición de espermatogonias a espermátidas coincidieron con el patrón general de los bivalvos marinos sometidos a fertilización externa. Las características principales incluían un espermatozoide con cola de tipo primitivo con cuatro mitocondrias esféricas ubicadas en la pieza intermedia y la típica disposición de microtúbulos 9+2 que rodean el centríolo. Durante la espermatogénesis, los cambios clave en la morfología celular ocurrieron hasta la etapa de espermatozoide, incluida la aparición de un núcleo en forma de bala, un acrosoma cónico, una pequeña vesícula proacrosomal de forma ovalada y dos fibras satélite laterales unidas al centríolo. El flagelo también se formó hasta la etapa de esperma. Taxonómicamente, estas características parecen ser específicas de una familia o de una especie y sugieren que N. subodosus puede estar estrechamente relacionado con las vieiras hermafroditas Patinopecten yessoensis, Chlamys farreri farreri, C. swiftii y Argopecten irradians dentro de la familia Pectinidae

To evaluate the antioxidant activity and oxidative damage by relaxing, wounding, and seeding of a saibo of different origin on Pteria sterna hosts, five oyster treatments were included: (1) relaxed (REL) but neither wounded nor seeded; (2) relaxed and wounded (WOU) but not seeded; (3) relaxed, wounded, and seeded with an allograft (ALL); (4) relaxed, wounded, and seeded with an autograft (AUT); and (5) unrelaxed, unwounded, and unseeded as control (CTR). Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and thiobarbituric acid (TBARS) activity were quantified between 3 and 24 h post-seeding. Compared to the CTR oysters, which did not suffer oxidative stress, SOD activity significantly decreased in the gonad and digestive gland in all treatments and decreased in mantle tissue in AUT oysters; this indicates that the entire process of preparing oysters for pearl culture (relaxing, wounding, and seeding) generates oxidative stress in the host. CAT was not a sensitive enzyme for measuring the short-term response of oysters to the wounding–seeding processes but rather a more prolonged or chronic stress. Similar to SOD, the lowest GPx and TBARS activity in seeded oysters evidenced their susceptibility to oxidative stress and damage, particularly in the WOU treatment. Evidence from this study indicates that SOD is a more sensitive enzyme for measuring the short-term response of the host oyster to the wounding and seeding of a saibo. It is also clear that the host undergoes stress at all stages of the pearl culture process, mostly during gonad wounding and regardless of the origin of saibo.

The structure and composition of mantle tissue from red abalone Haliotis rufescens were studied in relation to pearl farming. Histological (hematoxylin-eosin) and histochemical (PAS Alcian Blue, Sudan Black, Dahl's) tools were used to determine variations in the glycogen index, lipid index, and calcium coverage index of mantle tissue as a function of seasonality (cold and warm period) and body region (dorsal, central, ventral). Anatomically, only two well-developed and functional mantle folds (inner and outer) were observed across the marginal zone, together with a poorly developed, and presumably, rudimentary fold with the same cellular morphology as the inner fold. The inner mantle epithelium stored significantly higher concentrations of glycogen and mucins, triglycerides, and calcium than the outer epithelium. This pattern occurred significantly more during the cold season than during the warm season. Mucins from mantle tissue not only regulate crystal nucleation and orientation during biomineralization, but also give the inner nacreous layer its luster and color. High concentrations of lipids in mantle tissue could help compensate for the energy loss caused by the wound-healing processes associated with mantle tissue removal and seeding, which are stressful and energetically costly. The absorption of calcium ions from the environment to integrate a microlaminate of calcareous compounds gives the shell its structural properties of hardness and strength. An approach with molecular-ultrastructural tools is recommended to broaden the understanding of mantle tissue regionalization and its relationship to pearl sac formation, which may help increase pearl yield and quality in H. rufescens.

The use of anesthetic agents as pre-operatory treatment to pearl seeding surgery can be stressful to organisms and activate various physiological response mechanisms. This study evaluated some parameters of the systemic antioxidant and immune responses in red abalone (Haliotis rufescens) exposed to 0.25 mL L-1 eugenol (EUB), 3.0 mL L-1 phenoxyethanol (PEB) and CO2 at saturation, as well as in a control (CT) without anesthetic. Abalone were anesthetized for 45 min and, during the recovery stage, hemolymph samples were collected at 0.5, 1, 2 and 24 h. Total protein content (TP), superoxide dismutase (SOD), catalase (CAT) and myeloperoxidase (MPO) activity, as well as nitric oxide (NO) production, were evaluated in hemolymph cell-free fraction (HCF) and hemocytes lysate (HL). In addition, total hemocyte count (THC) was determined. In HCF, TP was significantly higher in abalone exposed to PEB than in the other treatments and CT at 0.5, 1 and 24 h. SOD activity in HCF was significantly higher in all treatments compared to the CT (1 h), while CAT and MPO activity was only significantly higher in abalone exposed to EUB compared to PEB at 1, 2 and 24 h. In the HL fraction, the percentage of SOD inhibition was significantly higher only in abalone anesthetized with EUB compared to the CT (0.5 h). These results suggest that the antioxidant activity of the species during the recovery phase from anesthesia was transient and restored after 24 h. Similarly, the immune response of H. rufescens at the systemic level was not altered by the anesthetics, suggesting that the species adequately tolerated the anesthesia process. This research provides evidence of the effects of anesthesia at the systemic level in red abalone for the proper selection of anesthetics for pearl culture.

In pearl culture, the proper selection of anesthetic agents may be a key step to reduce stress and facilitate handling of the organisms, either bivalves (pearl oysters) or gastropods (abalone). This study evaluated the visual (rate of relaxation and recovery, selection of organisms suitable for bead-nucleation) and physiological (glycogen and mucopolysaccharide indices) responses in the red abalone Haliotis rufescens exposed to different types and concentrations of anesthetics. The treatments were: Eugenol at 0.15 mL L-1 (EUA) and 0.25 mL L-1(EUB); Phenoxyethanol at 1.5 mL L-1 (PEA) and 3.0 mL L-1(PEB); Benzocaine at 0.15 g L-1 (BZA) and 0.30 g L-1(BZB); and CO2 to saturation. A different treatment with abalone maintained in fresh seawater without anesthetics was included as the control group. EUB, PEB and CO2 promoted higher proportions of anesthetized abalone (>80%) and abalone suitable for seeding surgery. Mortalities only occurred with the use of Eugenol at both concentra-tions. With CO2 in particular, 90% of the abalone were suitable for seeding, fully recovered in 168 min, and showed no side effects. The greatest significant decrease in the glycogen index occurred in the abalone treated with EUB, compared to the control group and the rest of treatments. The same trend occurred with the muco-polysaccharide index, where a maximum increase occurred in those abalone anesthetized with EUB, whereas PEB and CO2 showed similar values to the control. Based on these results, the therapy with CO2 is recommended to anesthetize H. rufescens prior to pearl culture; conversely, we suggest avoiding Eugenol as anesthetic due to its various side effects.

Fatty acids play a fundamental role in the ecology and growth of many invertebrates, such as filter-feeder bivalve. To guarantee adequate nutrition during transfer from the nursery to the natural environment, we studied the survival, growth and fatty acid (FA) profile of Crassostrea rhizophorae oyster spat fed with seven microalgae combinations of Chaetoceros sp. Araya strain (Ch-A), Tisochrysis lutea (Tl) and Tetraselmis chuii (Tc). The diets included three monoalgal diets (Ch-A, Tl and Tc), three binary combinations (Tl+Ch-A, Tl+Tc and Ch-A+Tc) and one ternary mixture (Tc+Ch-A+Tl). Groups of triplicated carboys each containing 21 oyster spat were used to test the experimental diets, while an additional group was deployed directly in the environment as a control. After 36 days, total lipids, FA profiles and biometric parameters of the spat were analyzed.​ The spat were then transferred to the outdoor environment, and cultivated under suspension conditions for 30 additional days. At the end of this period, FA profiles and growth were again determined. Environmental variables were sampled weekly. Highest shell height growth and soft tissues mass were observed in the spat fed with Ch-A in any combination: the mono-algae Ch-A diet, the binary Ch-A+Tc and Ch-A+Tl diets, a tendency that persisted in the outdoor environment. Our results showed lower shell and soft tissues mass growth, and a drop in the levels of certain FAs of the spat after their transfer to the natural environment, such as 14:0, 16:1n-7, 18:1n-9, 18:4n-3 and 20:5n-3 FA. This effect probably reflected a compensation strategy for the scarce availability of food and higher temperatures observed in the natural environment.

The reproductive and larval performance of Pteria sterna associated with anomalous environmental factors was evaluated, testing the hypothesis that the transition from La Nina to El Nino in 2008-2009 affected the "normal" periods in which ripe broodstock are collected and larvae are reared in a hatchery. Seasonal sampling included 2 reproductive periods (February and April 2009), 1 pre-reproductive period (November 2008), and 1 post-reproductive period (June 2009). Of the 40 oysters collected in each period, 20 were used for induced spawning and larval culture, while 20 were used to evaluate indices of reproductive performance. Water temperature, salinity, and seston content were monitored in each period. Sea surface temperature (SST) data associated with anomalous environmental conditions were obtained from the Aqua-MODIS satellite. Variations in SST affected reproductive performance more than larval performance in Pteria sterna. Spawning induc-tion failed in November 2008 and succeeded in February, April, and June 2009, although only the larvae from April completed metamorphosis and settled, given the riper broodstock, larger oocytes, and favorable environmental conditions (21.80 degrees C; 31 mg center dot L-1 total seston; +0.50 degrees C SST). Positive SST anomalies (+0.50 to +1.10 degrees C) from August to December 2008 resulted in longer summer conditions that affected spawning in February 2009. In June 2009 (22.50 degrees C; 29.50 mg center dot L-1 total seston; +0.40 degrees C SST), when the percentages of ripe gonads and mature oocytes were small, the larvae were not viable, and few spat settled. In addition to collecting ripe broodstock in winter-spring for optimal larval and spat viability, we recommend including a brief conditioning period at the hatchery following the spawning peak and a second conditioning period in late autumn to promote nutrient recycling and natural gamete recovery.

Se evaluó el uso de las reservas energéticas de reproductores juveniles de Pteria sterna (50 mm de altura; 9 meses de edad) durante su primera madurez sexual en condiciones de laboratorio. Se empleó una dieta microalgal base (Dieta M) complementada con fécula de maíz rica en carbohidratos (dietas F1 y F2) y con microcápsulas ricas en lípidos (dietas L1 y L2), equivalente a una ración diaria del 1 y 2 % de la biomasa seca de tejidos blandos. Se hicieron muestreos a los días 0 (d0), 15 (d15) y 30 (d30) para recolectar tejidos y determinar las variaciones temporales en el índice de tejido gonadal (ITG, %), diámetro teórico de ovocitos (DT, µm) y composición bioquímica de carbohidratos, proteínas y lípidos en la gónada, glándula digestiva, músculo y manto (mg/g). Debido a la talla de los organismos y carácter protándrico de la especie, los machos dominaron sobre las hembras en todos muestreos. Al d30, los organismos maduraron en diferente proporción dependiendo del sexo y dieta, siendo el ITG significativamente mayor en machos y hembras que se alimentaron con la dieta L1, y el DT de ovocitos significativamente mayor en las hembras de la dieta L2. La concentración de carbohidratos del músculo aductor y gónada disminuyó significativamente en ambos muestreos (d15 y d30) y en casi todas las dietas (excepto F2); esto sugiere un proceso de lipogénesis a partir de este combustible en ambos tejidos, particularmente en el músculo, lo que a su vez explica el incremento en los niveles de lípidos en la gónada al d30 en las ostras de las dietas L1 y L2. El contenido de lípidos de la glándula digestiva disminuyó significativamente al d30 con casi todas las dietas (a excepción de L2), indicando que este tejido moviliza a la gónada lípidos previamente almacenados para asegurar la maduración de gametos. La dieta L2 parece la mejor alternativa, incluso combinada con la dieta F2, para la maduración sexual de P. sterna, con resultados que podrían estar asociados a su actividad gametogénica inicial protándrica.

Se estudió el desempeño reproductivo y larvario de Pteria sterna en relación a factores ambientales anómalos, hipotetizando que la transición entre los eventos de La Niña y El Niño 2008-2009 afectó los periodos “normales” para recolectar reproductores maduros y cultivar larvas en laboratorio. Se realizaron muestreos estacionales en 2 periodos reproductivos (febrero y abril 2009), 1 periodo pre-reproductivo (noviembre 2008) y 1 periodo post-reproductivo (junio 2009). De las 40 ostras recolectadas en cada periodo, 20 se utilizaron para evaluar el desove y cultivo larvario y 20 para determinar indicadores de condición reproductiva. La temperatura, salinidad y contenido de seston se monitorearon en cada periodo. Los datos de temperatura superficial del mar (TSM) asociados a condiciones ambientales anómalas se obtuvieron del satélite Aqua-MODIS. Las variaciones en la TSM afectaron más el desempeño reproductivo que el desempeño larvario de Pteria sterna. La inducción al desove falló en noviembre 2008 y fue exitosa en febrero, abril y junio 2009, aunque solo en abril las larvas completaron la metamorfosis y se fijaron, a partir de reproductores más maduros, ovocitos más grandes y condiciones ambientales favorables (21.80 °C; ~31 mg·L–1 seston total; +0.50 °C TSM). Las anomalías positivas de TSM (+0.50 a +1.10 °C) de agosto a diciembre 2008 favorecieron un verano más largo que afectó el desove de febrero 2009. En junio 2009 (22.50 °C, 29.5 mg·L–1 seston total, +0.40 °C TSM), cuando los porcentajes de gónadas y ovocitos maduros eran bajos, las larvas no fueron viables y pocas semillas se fijaron. Además de recolectar reproductores maduros en invierno-primavera para una viabilidad óptima de las larvas y semillas, recomendamos incluir un breve periodo de acondicionamiento en el laboratorio después del pico de desove y un segundo a finales del otoño para promover el reciclaje de nutrientes y la recuperación natural de gametos.

Globally, pearl culture is a profitable sector generating significant export incomes for producer countries, as well as livelihood opportunities for local communities. Latin America has a long history as a pearl producer from extensive fisheries that date back to the 15th century. The presence of pearl oyster beds on the Pacific and Caribbean coasts of many Latin American countries was a major incentive for colonisation of the region and subsequent social and economic development of areas in the Gulf of California and the Caribbean. This review presents the historic background of the pearl fishery in this region since the arrival of the Spanish in the 16th century, describes the current status of pearl culture in Latin America, and outlines future opportunities for sector development. Information on the current status of pearl culture in Latin American countries is divided between two major categories: commercial and pilot-scale. Commercial pearl production currently occurs only in Mexico and production updates are provided for bead-nucleated, half pearls (mabe) and non-nucleated (keshi) pearls from the two pearl farms operating in the Gulf of California. The second category comprises countries whose pearling activities were relevant in the past (Venezuela, Panama) and others that are emerging, but still maintain pilot-scale production of mabe pearls using Pteria sterna (Ecuador, Peru), Pinctada mazatlanica (Panama) and Pteria hirundo (Brazil). Finally, this review discusses future prospects for pearl culture in Latin America, analysing technology gaps and challenges to be addressed if the cultured pearl sector is to achieve its full potential in this region.

The performance of the winged pearl oyster Pteria colymbus juveniles under suspended culture conditions was evaluate, including five culture methods and two seasons: upwelling and non-upwelling. Culture methods comprised enclosures confining the oysters: BTBC, BBOand BTO; and two other unconfined-oyster: OFOB and FNS. The initial shell height of the oysters ranged between 31–35 mm in both seasons. The increase in shell size and dry mass of soft tissues showed significant differences between seasons. Greatest growth occurred with the OFOB and FNS unconfined methods. The ANOVA II analysis showed significant differences between the variables obtained in both stations and culture methods. Principal Component Analysis showed that the interactions between the variables: temperature (inverse relationship), and UI, chl-a and POM (direct relationship) explained 89 % of the variability of the growth of the oysters. Given the low survival rates, attributed to the presence of predators within the closed enclosures and the higher growth seen in the culture methods without confinement, we recommend using the FNS and OFOB methods, taking advantage of the byssus produced by P. colymbus.

In this study the enrichment dietary effect with different crude protein levels (CP) and feed additives on growth, survival, feed conversion ratio (FCR), feed consumption (FC) and total hemocyte count (THC) in juvenile white shrimp Litopenaeus vannamei were evaluated. The study covered two bioassays: in the first one, juveniles were daily fed for 45 days with four experimental diets containing: (1) Control, commercial feed (35% CP); (2) 29% CP; (3) 32% CP; (4) 35% CP. After the 29% CP diet was selected, juveniles in bioassay II were daily fed for 45 days with a single CP diet complemented with probiotics: (1) Control, commercial feed (35% CP); (2) 29% CP; (3) 29% CP + Bacillus mix at 1×106 CFUg–1 feed; and (4) 29% CP + yeast mix at 1×106 CFUg–1 feed. Juvenile shrimp fed with experimental diets gained significantly more weight and increased survival, FCR, FC and THC compared with control diet. However, differences among experimental diets were not significant. In bioassay II, juvenile shrimp fed with experimental diet + feed additives significantly increased survival, FCR, FC and THC compared with control diet. Growth of juveniles significantly increased with 29% CP and 29% CP + yeast mix diets, compared with control group. Complementing the diet with yeast mix showed higher survival and THC of juveniles compared with the other experimental treatments. Different CP levels in shrimp diet improved growth, survival and circulating hemocytes, and addition of mixed yeast as feed additive induced better survival and immune response in juvenile shrimp.

In the Caribbean Sea, the winged oyster Pteria colymbus represents a promising resource for food and pearl production. The goal of the present study was to determine the influence of environmental variables generated by the seasonal coastal upwelling on the fatty acid profile (FAP) of the winged oyster Pteria colymbus. Changes in fatty acid (FA) levels were determined by gas chromatography coupled to mass spectrometry. Chlorophyll a (Chl-a), temperature, seston (POM and TPM) and upwelling index (UI) were measured monthly and correlated with the FAPs. Statistical analysis (MDS-ANOSIM) revealed significant differences between FAPs of the soft tissues in the upwelling and non-upwelling seasons. The FAs that mainly explained the variance in the FAPs during the non-upwelling season were 14:0, 16:0, 18:0, 20:4n-6, 20:1n-11NMID, 20:5n-3 and 22:6n-3. During the upwelling season, the FAs that explained the variance were 18:3n-3, 18:4n-3 and 18:2n-6, in addition to those that varied during the non-upwelling season. PCA analysis between FAs and environmental variables in the upwelling season showed that UI presented a direct relationship with acids 16:0, 18:4n-3 and 14:0 and an inverse relationship with 22:6n-3 and temperature. In the second component, chlorophyll a and POM were directly correlated with 18:2n-6, 20:4n-6 and 20:5n-3, and inversely correlated with 18:0, 22:6n-3 and temperature. In the non-upwelling season, temperature showed a direct relationship with 22:6-3 and an inverse relationship with 20:5n-3 and 14:0. POM, Chl-a and UI showed a direct relationship with 16:0 FA and an inverse relationship with 22:6n.3, 20:1n-11NMID, 20:4n-6, 18:0 and temperature. This study shows how dominant oceanographic conditions in the upwelling and non-upwelling periods modulate FA levels in P. colymbus.

The authors declare no conflict of interest.

We revise the historic context of freshwater pearl culture in Asia, updating the present situation and perspectives of this activity in Mexico, and, possibly, in some Latin American countries. The review is based on the results of ten years of research conducted in southeast Mexico (state of Tabasco) to firstly determine the demography of freshwater mussel stocks and, based on this information, identify a target species with a higher potential for pearl farming: the fatmucket mussel Psoronaias crocodilorum. The main advances relative to the seeding technique for keshi pearl production and composite technique for half-pearl (mabe) production are detailed and placed under perspective with China, as today's greatest producer of freshwater pearls. After ten years, several cohorts of keshi and mabe pearls have been produced, representing the first of their kind in Latin America. Although the yield and quality of these pearls has gradually been improved, some aspects of the keshi technique (preparation and seeding of the donor's mantle into the host's mantle) still require further optimisation. To promote social development, one of the goals of the project included the involvement of local communities in the manufacture and selling of handcrafts made from the shell. The other goal was to share the main outcomes derived from the keshi and mabe techniques with academics, producers, and government authorities through a series of training workshops aimed to create awareness in the local communities for the potential of freshwater pearl culture in Tabasco as an aquaculture-based, environmentally friendly and viable model for socioeconomic development.

This study generated baseline information relative to overall performance of the winged pearl oyster Pteria sterna implanted at two groups (small and large) for half-pearl (mabe) production. This is a suitable technology to optimize the pearl production in the tropical coasts of Ecuador. The yield and quality of mabe pearl produced, as well as oyster condition index, increase in oyster survival, shell size and mass of tissues, and environmental variables were examined in this study. From 120 oysters used, 65 were of small size (25 nucleated, 25 nonnucleated and 15 for the initial sample; initial average shell length of 64.7 +/- 5.3 mm; similar to 6 months old) and 55 were of large size (20 nucleated, 20 non-nucleated and 15 for the initial sample; 78.0 +/- 5.8 shell length cm; similar to 10 months old). Hemispherical plastic nuclei (12.5 mm base diameter, 7 mm height) were used. All groups of oysters were anesthetized with 1% Eugenol and cultivated for five months (May through October 2017). At the end of the trials, only one dead oyster occurred in the small size group. A high percentage (29.2%) of adductor muscle over-growth on the nuclei occurred in small oysters, probably caused by the relatively fast growth rate (>= 8 mm in 5 months). A lower percentage of muscle over-growth on the nuclei (5.6%), thicker nacre deposition, and higher occurrence of regular-shaped mabe pearls were observed in large oysters, compared to small oysters. This study suggests that large oysters (> 80 mm) should be preferably used for half-pearl production in P. sterna to ensure the highest quality standards for commercialization.

This study investigated the probiotic effects of one lactobacillus, one marine yeast, mix of three bacilli and mix of all probiotic strains on the growth, survival, antioxidant response (superoxide dismutase = SOD, catalase = CAT, gluthatione peroxidase = GPX) and immune response (lysozyme = LYZ, heat shock protein =HSP70) of hatchery-reared Catarina scallop Argopecten ventricosus early spat. The spat was exposed every three days for 28 days to a single dose of 1 × 106 CFU mL–1 of one of five treatments used in triplicate: (1) Lactobacillus plantarum (C3); (2) Candida cretensis (S10); (3) Mix of Bacillus cereus, Bacillus flexus, and Bacillus firmus (BMix); (4) Mix of 1 + 2+3 (LLBMix); (5) Group of spat without probiotics as control. Survival was 100 % in all probiotic treatments and the control group. The spat treated with the yeast (S10) and lactobacillus (C3) significantly increased absolute growth and growth rate compared to the control. The antioxidant activity and gene expression was significantly lower in all spat treated with probiotics than in the control group, particularly with the BMix, LLBMix (SOD), C3 (CAT, GPX), and BMix (CAT) strains. The immune activity and gene expression was also significantly lower in spat treated with probiotics, particularly BMix, LLBMix (LYZ), C3, BMix, and S10 (HSP70) strains, compared to the control group. The use of a single dose of probiotic or mix of different strains reduced activation of antioxidant and immune response and improved overall performance of hatchery-reared A. ventricosus spat.