The factors influencing half‐pearl (mabe) production in the red abalone Haliotis rufescens were investigated, as a strategy to optimize the technology for the development of a pearling industry in ...Chile. The effects of abalone size (small, large), implant position (dorsal, central, ventral and their combinations), and number of nuclei (one, two, three) were analysed on the quantity, thickness of the nacre layer and quality (shape, colour, lustre, defects) of the mabe produced. The size of abalone did not exert a clear influence on the quantity and quality of mabe, but the position on the shell (firstly) and number of nuclei (secondly) did. More mabe, with thicker nacre, brighter lustre and fewer defects occurred in small or large abalone implanted with only one nucleus on dorsal position. In contrast, small and large abalone implanted in the ventral position formed less mabe, with thinner nacre, poor lustre and more defects. This likely occurs because mantle tissue folds at the ventral position and does not always cover the nucleus, leaving it partially or totally exposed. Most of the pearls were categories AA in small abalone and A in large abalone; only three AAA gems were produced in large abalone with one nucleus on dorsal position or with three nuclei (DCV). Based on these results, we recommend implanting abalone at 60–100 mm shell length, with only one nucleus on the dorsal position.
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.
The reproductive strategy of lion’s paw scallop Nodipecten subnodosus was evaluated in a culturing system in Bahía Tortugas, Baja California Sur, Mexico during an annual cycle, comparing its response ...with data previously reported at other localities. High frequencies of ripe gonads throughout the year indicate that reproduction was continuous, with two main ripening/spawning events: July-September and December-March. A continuous breeding is also reported for the species in Bahía Magdalena, Bahía Juncalito, and Bahía de Los Angeles. These eutrophic areas are Biological Active Centers where gametogenesis appears to be regulated by the energy taken from recently ingested food following an opportunistic strategy. However, the digestive gland index decreased and the muscle indices increased during one of the breeding peaks, suggesting that some stored reserves are also used to sustain gametogenesis (conservative strategy) partially. High incidences of atretic oocytes are likely associated with atypical daily variations in water temperature from May through September (12 to 33°C), or with stressful conditions in the culturing system in summer. Despite this, the culturing system set in Bahía Tortugas appears beneficial for a continuous reproduction of N. subnodosus.
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 reproductive and larval performance of Pteria sterna associated with anomalous environmental factors was evaluated, testing the hypothesis that the transition from La Niña to El Niño 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 induction 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 °C; 31 mg·L-1 total seston; +0.50 °C SST). Positive SST anomalies (+0.50 to +1.10 °C) from August to December 2008 resulted in longer summer conditions that affected spawning in February 2009. In June 2009 (22.50 °C; 29.50 mg·L-1 total seston; +0.40 °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.
Relaxation as a sedative therapy before nucleus seeding is assumed to be stressful to some marine animals during its initial phase, before acting at the cellular level. The antioxidant activity and ...possible oxidative damage to soft tissues was evaluated in the winged pearl oyster Pteria sterna exposed to four relaxants, at two concentrations each. The relaxants were: propylene phenoxetol (1.5 and 2.5 mL L−1), benzocaine (0.15 and 0.25 g L−1), magnesium chloride (15 and 30 g L−1), and eugenol (0.25 and 0.5 mL L−1). The enzymatic activity (superoxide dismutase, catalase, glutathione peroxidase) and oxidative damage (TBARS, lipofuscins) were measured at 30, 60, and 120 min after immersion in each relaxant, and at 65 h representing the recovery period (filtered seawater with no relaxant). Propylene phenoxetol (2.5 mL L−1) and benzocaine (0.25 g L−1) induced >80% relaxation within the first 45 min. Variations in the activity of superoxide dismutase activity were not significant between treatments in mantle and gills, but increased in muscle at 65 h in oysters exposed to 1.5 mL L−1 propylene phenoxetol and 15 and 30 g L−1 magnesium chloride. Control oysters significantly increased catalase activity in adductor muscle and gills (30–60 min), but the activity of glutathione peroxidase did not significant vary in muscle and mantle, and only decreased in gills at 65 h exposure to 2.5 mL L−1 propylene phenoxetol. Higher TBARS concentrations, as indicative of oxidative damage, only occurred at 30 min in muscle and gills in oysters exposed to 30 g L−1 magnesium chloride and 0.25 g L−1 benzocaine. Relaxing with benzocaine caused a significant accumulation of lipofuscins in gills at 120 min, again as possible indicator of oxidative stress; lowest lipofuscins values occurred with 1.5 mL L−1 propylene phenoxetol. These results confirm that propylene phenoxetol causes minimal interaction with antioxidant enzymes and provoke little oxidative damage to soft tissues in P. sterna.
•Relaxation is a stressor that alters homeostasis before acting at a cellular level.•SOD activity did not vary between treatments in mantle and gills, only in muscle.•The accumulation of lipofuscins in gills with benzocaine reflected oxidative stress.•Magnesium chloride and benzocaine increased TBARS levels, indicating oxidative damage.•Propylene phenoxetol caused minimal interaction with antioxidant enzymes and little oxidative damage to soft tissues.
•Optimum temperature for growth of green mussel from Guayacan Venezuela is 26 °C.•Positive SFG were found from 22–30 °C and negative at 34 °C.•Positive allometry of shell length-total wet weight was ...found, which is higher than that from native populations.•Temperature-wise Gulf of Cariaco is a suitable site for P. viridis aquaculture.•A new reliable system for physiological SFG measurements is described.
Optimum temperature for growth of an invader population of green mussel Perna viridis (31.1 ± 1.9 mm SL; 0.8 ± 0.2 g DTW) from Guayacan Venezuela, was determined by means of scope for growth (SFG) at 22−34 °C with an open-flow system. The objective was to find the suitability of its cultivation in the Gulf of Cariaco Venezuela. Morphometric relationships of shell length vs. wet and dry weights were obtained to determine the condition index of experimental mussels. SFG was highest at 26 °C (64 ± 16 J g−1 h−1), was positive at 22–30 °C (35 ± 3 and 20 ± 1 J g−1 h−1 respectively) and negative at 34 °C (-39 ± 11 J g−1 h−1). Mussels employed were at good condition indicated by a positive allometry of shell length–total wet weight (b-value = 3.7394) (R2 = 0.397) which was higher than in native populations. Condition index (2.01–13.49) indicated that the mussels studied were not active in reproduction. Based on SFG results and temperature published data from the Gulf of Cariaco, it is concluded that temperature-wise this site (20.1–29.1 °C) is appropriate for aquaculture of the population of P. virids studied. Further studies on the combined effect of temperature and seston concentrations over SFG are needed since a combination of high temperature and seston depletion frequently occurs in this site from September to January. The advantages of the new open-flow sytem for ecophysiological studies in aquatic organisms are discussed.
Recent years have seen major developments in the culture and availability of tropical microalgae as a food source for tropical bivalve species. The nutritional value of seven small (<9 μm) tropical ...microalgae species: two diatoms (Chaetoceros muelleri and Chaetoceros sp.); three golden-brown flagellates (Isochrysis sp., Pavlova salina and Pavlova sp.) and two green-flagellates (Micromonas pusilla and an unidentified coccoid CS-126), were analysed for carbohydrate, lipid and protein contents as well as fatty acid composition. Each species of microalgae was fed singly to early (D-stage veliger) and later (umbo stage veliger) stage larvae of the black-lip pearl oyster, Pinctada margaritifera. Highest survival of D-stage larvae over the 10-day experiment was recorded for those fed Pavlova sp. (CS-50). Greatest shell growth was shown by D-stage larvae fed the golden-flagellates Pavlova sp. (CS-50) and Pav. salina. Based on growth of D-stage larvae, the microalgae could be divided into three groups: (1) larvae fed Pav. salina and Pavlova sp. showed significantly greater growth than those fed other microalgae; (2) those fed Isochrysis sp., C. muelleri and M. pusilla showed significantly greater growth than unfed larvae; and (3) larvae fed Chaetoceros sp. and CS-126 did not grow at a rate greater than unfed larvae. Growth of D-stage veliger larvae was significantly correlated with carbohydrate, lipid and protein content of microalgae and with levels of dietary polyunsaturated fatty acid, specifically DHA (r=0.829, P=0.021). In a second experiment survival of umbo-stage larvae (including the unfed control) did not differ significantly between treatments (P<0.05) after 8 days of culture. Larvae fed Pavlova sp. and Pav. salina showed the greatest incremental growth increases, but these were not significantly greater than those of larvae fed TISO and C. muelleri (P>0.05). Growth of umbo-stage larvae fed M. pusilla, Chaetoceros sp. and the Prasinophyta sp. (CS-126) did not differ significantly from that of unfed larvae (P<0.05). This study is the first comprehensive assessment of the nutritional value of tropical microalgae species for pearl oyster larvae. The results provide a basis for development of more effective larval culture techniques by identifying microalgae supporting good growth of P. margaritifera larvae of different ages.
Ensuring supplies of pearl oyster spat for commercial grafting operations in Mexico is an ongoing problem. This has refocused research toward improving hatchery propagation protocols. Since gender ...plays an important role in the physiology of bivalves, we studied the use of fatty acids in the gonad and digestive gland of male and female winged pearl oyster (Pteria sterna) over its natural breeding season. Sampling included two peaks of ripening (February and April 2009), a pre-reproductive period (November 2008), and a post-reproductive period (June 2009). We found a significant increase in storage of docosapolyenoic fatty acids during development and ripe stages only in the female gonad, which indicates that these fatty acids could be a limiting factor for successful development of high quality eggs. The content of total monounsaturated fatty acids in male gonads, especially the fatty acid 16:1 n7, was significantly higher than in female gonads at the development and ripe stages. We also found differences between males and females in the use of some fatty acids in the digestive gland, especially at the spawned stage. Our results have future application in developing protocols for rearing of this pearl oyster in hatcheries. Incorporating dietary supplements containing docosapolyenoic fatty acids into diets of pearl oyster broodstock could be a practical way to improve their performance, which is crucial for enhancing the viability of larvae and spat.
•We examined the use of fatty acids during reproduction in the winged pearl oyster.•Our results showed differences between male and female oysters.•Only female oysters accumulated 22 C fatty acids during gonad development.•Males accumulated more saturated and monounsaturated fatty acids than females.•We highlight an important strategy to improve hatchery propagation in Pteria sterna.
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