Mario Monteforte

Effect of temperature on oxygen consumption and ammonia excretion in the Calafia mother-of-pearl oyster, Pinctada mazatlanica (Hanley, 1856)

Abstract The effect of temperature on oxygen consumption and ammonia excretion in the pearl oyster Pinctada mazatlanica was studied as a strategy to define the optimum thermal range for experiments on reproductive conditioning of broodstock of this species. Oysters were taken to the laboratory, acclimated for 2 weeks at four temperatures (18, 23, 28, and 33 °C), and transferred to respiration chambers for individual measurements of oxygen consumption and ammonia excretion at the same temperatures. Respiration and excretion rates, as well as routine respiratory/excreted energy and Q 10 coefficients were calculated. One-way ANOVA was applied to determine differences in these parameters as a function of temperature. All physiological parameters yielded highly significant differences with increasing temperature, suggesting that an adequate metabolic temperature range for the species may lie between 23 and 28 °C. Within this range, a combination of active respiration and low ammonia excretion, together with Q 10 coefficients near 2, suggest the existence of compensatory mechanisms that allow the species to perform seasonal regulation during moderately warm temperature changes. In contrast, 18 and 33 °C represented marginal temperature conditions close to the tolerance limits of the species. In particular, 33 °C was a stressful temperature for P. mazatlanica because of high ammonia excretion. More studies under conditions of satiation and hypoxia, as well as experiments testing lower and higher lethal temperatures are needed to understand the energy budget of the species.

Spat collection studies on pearl oysters Pinctada mazatlanica and Pteria sterna (Bivalvia, Pteriidae) in Bahia de La Paz, South Baja California, Mexico

The present work deals with the temporal and bathymetrical variations of the epifaunal community associated with two species of pearl oysters (Pinctada mazatlanica and Pteria sterna) during a seed collecting season from June to November 1989. A total of 63 items (species, genera and/or families) were recorded; their variations in presence and abundance were followed during three periods (June–July, August–September and October–November). The collectors were examined for different immersion times (2, 4, 6 and 8 weeks) for each period. Community structure was compared through the Brillouin Index, the Morisita Index and the Importance Value.We define the chronology of spatfall for both species of pearl oysters and their bathymetrical distribution. Relationships between these species and the epifaunal community present into the collectors were analysed, searching for possible noxious effects on the survival of juvenile pearl oysters, and identifying index species related with their spatfall. A strategy for starting massive seed collection of both species is established, particularly for P. mazatlanica.

FACTORS INFLUENCING RECRUITMENT OF HATCHERY REARED PEARL OYSTER (PINCTADA MAZATLANICA; HANLEY 1856) SPAT

Abstract We evaluated experimental collection of Pinctada mazatlanica spat on substrates of different textures and colors placed at different depths within settlement tanks. When larvae reached the pediveliger stage (day 25), black-colored spat collectors (“envelope” type) composed of the following materials were offered as settlement substrates: onion bag, mosquito net, fishing net, and 63% shade-cloth. Spat collectors measured 30 × 30 cm and were composed of an outer bag and inner substrate made of the same material. The influence of the color of spat collector material on recruitment was investigated using a second type of spat collector composed of onion bags as the outer bag and inner substrate (“bag” type). Bags were prepared in 3 different outer/inner (O/I) color combinations of green/green, green/black, and red/black (O/I). Both types of collectors were deployed at different depths within settlement tanks. Approximately 2.7% of the initial larval population survived, resulting in 35,583 spat. Of these, 71.3% recruited to bag type collectors, 21.9% to envelope type collectors, and 6.8% to the surfaces of the culture tanks. Spat recruitment was significantly affected by collector material (P < 0.01), with fishing net and shade-cloth yielding highest and lowest density of spat, respectively. Similarly, spat collector color combination significantly influenced spat collection (P < 0.01), with higher recruitment to red and green substrates. For both spat collector types, there was significantly greater (P < 0.01) recruitment of spat to collectors in the middle of the water column (60–90-cm depth). This study showed that both the type and color of material used for spat collectors, as well as depth of deployment, influenced recruitment of P. mazatlanica spat. These results will help fine-tune current hatchery techniques for this species.

Gonadic conditioning of the calafia mother-of-pearl oyster, Pinctada mazatlanica (Hanley, 1856), under two temperature regimes.

Abstract Gonadic conditioning of pearl oyster Pinctada mazatlanica was studied under two water temperature regimes using cultured specimens. Before starting conditioning, specimens were induced to spawn with thermal shock. Two different regimes were evaluated, controlled temperatures (CT) and gradually increasing temperatures (IT). In both trials, specimens were fed daily with Isochrysis galbana and Chaetoceros gracilis in a proportion of 7:3. Gonad and muscle samples were excised from the oysters every 15 days and processed for histological analysis. Condition Index and Muscle Condition Index were calculated. Similarly, oocyte frequency and oocyte diameter measurements were made. ANOVA analyses were used to test significant differences in the frequency and diameter of postvitellogenic oocytes, and values of both condition indexes between temperature regimes, and over time. The IT showed more suitable conditions for gonad conditioning than CT, although the time needed for reaching maturity was higher in the former regime. For CT, a temperature of 24°C was the best for conditioning, since there were no traces of atretic oocytes, partially spawned specimens, and there were less previtellogenic oocytes and more postvitellogenic oocytes filling the follicles. At 20°C, no positive results were noticed. Condition indexes appear to be reliable indicators of gonad activity during conditioning in both trials. The ANOVA analysis detected significant differences in almost all the statistical treatments run for oocyte frequency, oocyte diameter and condition indexes according to temperature regime and over time.

On the first record of a potentially harmful fish, Sparus aurata in the Gulf of California

The record of free and healthy Mediterranean gilt-head seabream Sparus aurata Linnaeus, 1758 in waters of the Gulf of California, México is documented for the first time. Consequences of this introduction are briefly outlined.

Differential gonadal development of grafted and ungrafted specimens of the Calafia mother-of-pearl oyster, Pinctada mazatlanica (Bivalvia: Pteriidae)

Summary The present work deals with the existence of differential gonadal development between grafted and ungrafted specimens of the pearl oyster, Pinctada mazatlanica. Oysters were collected as spat and extensively cultured until they were suitable for pearl formation. A mantle allograft was placed within the gonadal tissue and the treated oysters were maintained under the same culture conditions as untreated oysters. After a year of Keshi pearl formation, samples of gonadal tissue, digestive gland, and muscle were excised from each oyster and used for histological and biochemical analyses. The histological examination of gonads was supported with measurements of the oocyte frequency and diameter and the use gonadic and muscle performance indices. For biochemical analyses, the concentration of carbohydrates, proteins, lipids, and triacylglycerides was studied. A two-way ANOVA was applied for differences in the oocyte diameter, index values, and biochemical composition of specimens over time and experimental treatments. All histological and biochemical results showed that grafted oysters achieved greater gonadal performance and were in better reproductive condition than the controls. They presented higher gonadic index values and lower muscle performance index values than untreated specimens. In addition, grafted oysters showed higher concentrations of lipids and triacylglycerides in the gonadal tissue and digestive gland and lower concentrations of proteins in the muscle than ungrafted oysters. Apparently the mantle allograft stimulates redirection of energy flows to reproduction and gonadal development. The muscle and digestive gland (particularly the former) are the main sources for this energy-requiring process. A neuroendocrine control involving the formation of a complex relationship between both mantle and gonadal tissues is suggested. More studies of the histological, histochemical, biochemical, and endocrine composition of mantle of pearl oysters are required to confirm these findings.

Condiciones para el desarrollo de granjas perleras y producción de perlas: estado del arte, potencial y perspectivas

Pearl farms with pearl oysters, abalones, freshwater pearl mussels, and some snails andbivalves having attractive shell, stand out for their general feasibil...