Objective. To detect the presence of presumptive hypnospores of the protozoan Perkinsus sp. in a wild population of the Mexican chocolata clam Megapitaria squalida in the southeastern Gulf of ...California, using Ray´s fluid thioglycollate medium (RFTM). Material and methods. Thirty specimens with size between 56.17 and 69.04 mm were captured each month, during an annual cycle. Infection prevalence and intensity and water parameters were recorded monthly from September 2012 to September 2013. Results. Perkinsus sp. was detected in tissue samples from the Mexican chocolate clam using the RFTM test by the presence of dark round corpuscles that represent parasite´s hypnospores. Monthly samplings revealed a prevalence of 0-43.33% and an infection intensity ranging from 1 to 4 (no infection = 0 hypnospores/entire preparation, to moderate = 34 hypnospores/entire preparation). Conclusions. Perkinsus sp. is reported for the first time in a wild population of M. squalida in the southesternmost Gulf of California. The results indicate that this protozoan is dispersed intraspecifically and would now, potentially, parasiting a new host in the region.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The aim of this study was to evaluate the growth performance and survival of the Pacific white shrimp (Litopenaeus vannamei) with red tilapia hybrid (Red Florida: Red Yumbo) and spotted rose snapper ...(Lutjanus guttatus), stocked at different densities in intensive brackish water mix-culture systems compared with monoculture of shrimp. The experiment, conducted in twenty-one plastic tanks (750 L) was set up to evaluate water quality, growth; production and survival of shrimp, tilapia, and snapper, for 60 days. Three replicates were assigned to seven treatments: After 30 day, initial densities were unfolded (shrimp = 50 ind m-3, tilapia = 16 ind m-3 and red snapper = 8 ind m-3). Feeding rate was adjusted at 5 and 10% of body weight d-1 for shrimp and fish, respectively. The shrimp-tilapia mix cultures produced the higher nitrogen and phosphorus in water concentrations. Significant lower survival values were obtained for shrimp (60.0 ± 0.6%) cultured with snapper and for tilapia (79.0 ± 3.1%) reared with shrimp. Mean final biomass for shrimp, tilapia and snapper were higher for the mix-cultures (2.04, 7.7 and 2.9 fold increase, respectively) with respect to their initial biomass. The mix culture system allowed an increase in total production with lower feed conversion ratios, thus contributing with the system sustainability.
Background: For its flesh and flavor, the Pacific oyster Crassostrea gigas is cultivated worldwide, but as filter feeders, this bivalve bioaccumulates heavy metals from different pollution sources, ...rendering them unsafe for human consumption. Goals: We carried out this study to assess the heavy metal concentrations in cultivated oysters from a farm located on the southeastern coast of the Gulf of California during 2011. Methods: Oyster samples were analyzed monthly (March-December 2011) for cooper (Cu), cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), arsenic (As), and mercury (Hg). Results: The mean values (µg g-1, dry weight) for each metal were Cu = 51.42 ± 25.92, Cr = 24.97 ± 32.38, Cd = 13.84 ± 4.22, Ni = 10.26 ± 12.18, Pb = 2.18 ± 1.28, As = 0.37 ± 0.08, Zn = 267.42 ± 92.29, and Hg = 0.02 ± 0.01. Conclusions: The results suggest that metal burdens could be influenced by anthropogenic activities such as agriculture and aquaculture surrounding the culture zone. Cu, Cr, Cd, and Pb levels (µg g-1, fresh weight) were above the maximum permissible values and thus pose a threat to human health. Metal concentrations must be monitored periodically.
ABSTRACT The objective of the present work was to identify and validate single nucleotide variations located in candidate genes to growth traits in tilapia (Oreochromis niloticus). Two transitions ...were identified in the promoter region of the growth hormone gene (GH); eight nucleotide changes were identified in introns and promoter region of the IGF-I gene; and a transition (T/C) was identified in the Myogenin gene (MyoG). The highest genotypic frequency (0.8) for GHpA1 and MyoG was found in the GG and TT homozygous individuals, while the highest frequency (0.9) for GHpB1 was observed in the CT heterozygous fish. There was no genotypic frequency in the CC homozygous tilapia for the GHpB1 and MyoG markers. Based on their allelic frequencies, validation as novel single nucleotide polymorphisms (SNP) of those variations located at O. niloticus GH and MyoG genes was possible. These new markers will allow their association with growth traits in tilapia to be exploited in order to determine their potential use as assisted-selection markers.
The protozoan Perkinsus marinus has been associated with high mortality episodes of the eastern oyster Crassostrea virginica in the USA. The presence of P. marinus on the pleasure oyster Crassostrea ...corteziensis cultivated in two estuaries on the southeast coast of the Gulf of California was evaluated. Oysters were collected monthly (September 2016 to September 2017) and analyzed using Ray's fluid thioglycollate medium (RFTM) and polymerase chain reaction (PCR). Water parameters and oyster biometrics were also recorded. Pathogen prevalence increased over time from 0 to 100% in oysters from La Pitahaya, and from 0 to 83.33% in those from Bacorehuis. At both oyster farms, infection intensity was light (<1*10.sup.4 parasites g.sup.-1 wet tissue), pathogen prevalence and infection intensity were correlated with oyster size and weight, and there was a strong correlation between P. marinus prevalence and intensity (La Pitahaya r = 0.91; Bacorehuis r = 0.82). The oysters that resulted positive for P. marinus by RFTM also were assayed using PCR. P. marinus presence was confirmed in 98.27% (114/116) of the oysters from La Pitahaya, and 95.83% (46/48) of those from Bacorehuis. The detection of P. marinus confirms that this pathogen is well established in the area with high expression during the warmer season. Despite the light infection intensity of this parasite at both sites, health surveillance of this bivalve in the region is highly advisable.
ABSTRACT The pen shell (Atrina maura) is a filter-feeder bivalve that may accumulate metals in its body. The objective of this study was to determine seasonal concentrations of copper (Cu), chromium ...(Cr), cadmium (Cd), nickel (Ni), lead (Pb), arsenic (As), zinc (Zn), and mercury (Hg) in soft tissue and muscle of A. maura cultivated in a farm located in the southeastern coast of the Gulf of California from summer 2011 to summer 2012. Except for Cu, the higher metal concentrations were found during the dry season (winter 2011-spring 2012). The mean values in soft tissue fluctuated from 0.064 ± 0.01 µg/g (dry weight dw) for Hg to 485.66 ± 71.12 µg/g (dw) for Zn, while for muscle they varied from 0.058 ± 0.03 µg/g (dw) for Hg to 64.83 ± 4.90 µg/g (dw) for Zn. Concentrations of cadmium (18.15 µg/g in soft tissue and 1.82 µg/g in muscle, wet weight ww) and lead (2.31 µg/g in soft tissue, ww) exceeded the permissible limits (36.3, 3.64, and 2.31 times, respectively) recommended by the sanitary regulations of the official mexican standards. The results suggest that variation of metal levels in cultivated pen shell could be influenced by seasonality and anthropogenic activities such as agriculture and aquaculture developed around the culture zone. Continual monitoring of metals in farmed pen shell is recommended.
Our objective was to assess the quality of eggs and juvenile of Nile tilapia (Oreochromis niloticus) from broodstock of three commercial hatcheries (Hl, H2, and H3). Larval weight was significantly ...higher for H2 and H3 hatcheries (P < 0.05). After 45-day growth, weight of juveniles of H2 was higher, while specific growth rate was significantly higher for H1 and H2 (P < 0.05). After the ammonia stress test, no significant differences in mortality were found among larvae from the three hatcheries, although a positive relationship between carbohydrate content in eggs and juvenile mortality was observed (P < 0.05). After the salinity stress test, the lowest and highest mortality (P < 0.05) occurred respectively in tilapia larvae from the H1 (24.2%) and H3 (57.8%) hatcheries. We concluded that egg quality was not affected by tilapia broodstock from the three hatcheries studied, but differences were obtained for growth performance, carbohydrate content, and survival of juveniles when exposed to the salinity stress test. These three indexes should be considered as potential juvenile quality criteria for tilapia.
Bivalves reproductive cycle varies according to the particular environmental conditions where they are found, and these reproductive details represent basic information for their capture, management ...and conservation strategies. With this objective, the reproductive cycle of the clam Megapitaria squalida, inhabiting the Southeast of the Gulf of California (Altata Bay, Sinaloa, Mexico), was studied using histology and changes in the number and size of oocytes, from June 2013 to June 2014. Histological analysis of the gonads showed spawning activity throughout the year, with two peaks. The first was registered in October and it was accompanied by the highest decrease of weight; the second was in February with the highest percentage of spawning population; besides, a resting period was observed in December. The sex-ratio (female:male) of the clam population was 1.08:1 (χ2 = 5.72, d.f. = 1, P < 0.05). Mean oocyte size and number were different (P < 0.05) among all sampling months and fluctuated from 34.6 ± 5.8 µm in June 2014, to 41.9 ± 6.8 µm in February 2014, and from 443.8 ± 424.5 in February 2014, to 1 214.4 ± 267.6 counted in April, respectively. With these results we suggest a protection season from October to November, when the most intense release of gametes occur in this population.
The effect of three crude dietary lipid levels (4, 8, and 12%) on egg quality of the female redclaw crayfish, Cherax quadricarinatus, was evaluated. Three replicate groups of 40 crayfish (mean ...initial weight ± SD, 23.0 ± 3.0 g) per diet treatment were stocked in 15,000 -L tanks, at 28 C. After 75 d of culture, there were significant differences (P < 0.001) in egg area (3.52-3.90 mm²), volume (34.0-39.3 mm³), weight (4.81-5.36 mg), and diameter (2.15-2.27 mm) in response to dietary lipids in the diet. Using the quadratic equation, the maximum responses of these parameters corresponded to lipid levels from 8.60-8.84%. There were no significant differences (P > 0.05) in survival (82.1-86.9%), final weight (41.0-43.7 g), number of spawning females (18.12-27.38%), and fecundity (9.07-10.31 eggs/g female). Additionally, there were no significant differences (P > 0.05) in egg mean protein (2306.87 ± 440.08 μg/egg), lipid (441.95 ± 83.23 μg/egg) and carbohydrate (74.81 ± 10.12 μg/egg) contents, and energy (13.49 ± 2.25 kcal/egg). The optimum overall response was obtained for dietary lipid content of 8.7%, which we recommend to optimize egg quality of this freshwater crayfish.
The gonadal maturation of the pleasure oyster Crassostrea corteziensis during four cultivation cycles (November 2004-June 2005, N4J5; August 2014-February 2016, A14F16; September 2015-December 2016, ...S15D16; September 2016-August 2017, S16A17) was studied in the southeastern Gulf of California, Mexico. Although C. corteziensis exhibited the typical reproductive phases (undifferentiated or resting, initial gametogenesis, advanced gametogenesis, maturity, spawning and post-spawning), the intensity of reproduction and the timing of the onset of the different phases of gonadal development varied in each cultivation cycle. Reproductive peaks were observed in different months (N4J5 in May, A14F16 in July, S15D16 in May and S16A17 in June) during spring and summer. Spawning correlated with temperature in the N4J5 and A14F16 cultivation cycles but it showed no correlation with chlorophyll-a concentration in any of the cultivation cycles. C. corteziensis presented an opportunistic continuous reproductive strategy with spawning occurring during several months of the year. The modification of the species' reproduction pattern could contribute to the natural settlement of larvae, increasing the natural production of this native oyster resource in the southeast of the Gulf of California, where it has been fished intensively.
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