Pedro Enrique Saucedo

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.

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.

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.

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 (mabé) 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 mabé 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.

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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.