Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Microbiota, the microorganisms that colonize living organisms. Oysters rely exclusively on an innate immune system. This study characterized the cultivable gastrointestinal tract microbiota (GTM) of the oyster Crassostrea gasar and evaluated their influence on immune responses. Antibiotics were used to reduce or alter the microbiota during in vitro and in vivo assays. Haemocyte viability, concentration, and phagocytic capacity, as well as the production of reactive oxygen species (ROS), were evaluated in antibiotic-treated and control oysters. Microbiological analysis of the gastrointestinal tract was also performed; bacteria were selected using culture media and were identified by 16S ribosomal DNA. The results showed that the antibiotics eliminated bacteria in vitro but increased their concentrations in vivo. The GTM was composed of 26% amylolytic bacteria, 21% lipolytic bacteria, 18% proteolytic bacteria, 18% cellulolytic bacteria and 17% lactic acid bacteria; there were no differences in the amounts of these bacterial types between the control and treated oysters. Three major bacterial phyla, Proteobacteria, Firmicutes and Actinobacteria, and seven genera, Labrenzia, Pseudomonas, Halomonas, Shewanella, Vibrio, Bacillus, and Micrococcus, were detected. The concentration, viability, and phagocytic capacity of hemocytes and the production of ROS were not significantly altered by antibiotic treatment. In conclusion, the antibiotics altered the number of heterotrophic bacteria without changing hemocyte function, suggesting that this assay could be useful for verifying the influence of microbiota in host-parasite interactions.

Aspects of distribution and population dynamics were assessed in two rock shrimp species of the genus Sicyonia. Samples were obtained by sea bottom trawling in depths from 50 to 460 m during two research cruises on board the B/I BIP XII in the Gulf of California, Mexico. Taxonomic identification of specimens was performed; measurements of individual length and weight data were taken to obtain biometric relationships and length frequencies. Growth parameter estimations were performed adjusting the von Bertalanffy growth model (VBGM), and the recruitment pattern was obtained by the ELEFAN II method. Longevity was estimated with the Taylor equation, natural mortality with six different models, and length at first maturity by the logistic model. A total of 67 fishing trawls were monitored, and 1,330 specimens were caught (65% S. ingentis; 35% S. penicillata) in the depth range from 124 to 338 m. Sex ratio (F:M) was 1.0:1.6 for both species; weight and length relationships (both sexes) showed an isometric growth for S. ingentis and positive allometric growth for S. penicillata. Growth parameters and longevity values were moderate (1.71 and 1.81 years) with age at first maturity around six months for both species. The recruitment pattern showed continuous periods all year long, with a notable peak from November to May. Average natural mortality was 2.47 for S. ingentis and 2.35 for S. penicillata. Distribution and population dynamics information reported in this study for these two shrimp species should be considered as base knowledge in subsequent studies on fisheries management in the Gulf of California.

Although Lithodes santolla is a resource with high commercial importance that has aroused interest in controlled reproduction in captivity, currently, little knowledge is available about basic reproductive aspects of this species. This research study describes detailed oogenesis stages at the histological level in adult females of the southern king crab of the Magellan and Chilean Antarctic Region. Oogenesis was quantitatively analyzed from the proliferation of 10-24 μm oogonia and during oocyte growth. Five stages of ovary development were identified: multiplication (0), previtellogenesis (I), vitellogenesis (II), maturity (III) and spawning (IV). Furthermore, 11 oocyte substages were distinguished: oogonia, chromatin nucleolus, early perinucleolus, late perinucleolus, oil globule, early vitellin globule, late vitellin globule, postvitelogenic, germinal vesicle migration and germinal vesicle breakdown. Primary vitellogenesis occurred in oocytes 180-185 μm, containing acidophilic globules and surrounded by a layer of thick follicle cells (20-40 μm). Secondary vitellogenesis was evident in oocytes at 315-321 μm with numerous acidophilic granules in the cytoplasm and surrounded by thin follicle cells; then, cortical crypts appeared, indicating the prematuration stage and preparation for ovulation. This study allows establishing gonadic changes that occur during a reproductive cycle of female L. santolla and help to strengthen aquaculture initiatives and management in the Magellan and Chilean Antarctic Region.

A multibeam sonar combined with an Acoustic Doppler Current Profiler (ADCP) were used at the Veracruz Reef System (VRS), Gulf of Mexico, during the spawning period of August 2016 in order to elucidate plankton trajectories within the study area. The new high-resolution bathymetry provided the location of 50 coral reefs, 27 more reefs than known at the VRS. Most of those reefs are submerged reefs located at depths greater than 40 m. The total coral reef area of the VRS was calculated in 70.1557 km2. Only ~10% of the total area corresponds to submerged reefs. Forty-eight species were identified, seven more than known species at the VRS, 45 of the order of Escleractinia and 3 of the order of Anthoathecatae. Acropora prolifera, a hybrid, was also identified in most reefs. All species were observed in the emerged and submerged reefs. The distance at which the three local river discharges (Jamapa, La Antigua, and Actopan) brought sediments to the VRS was calculated. Those are inappropriate areas for coral settlement or development due to sediment transport and temperature and salinity fluctuation. Finally, light penetration was measured at 19 m depth near one reef structure during August 2016 suggesting that even during cloud coverage and rain periods there was a light bioavailability at the sampling point.

This paper is the first report with morphometric measurements in the Eastern Tropical Pacific of a deceased 5.48 m juvenile whale shark Rhincodon typus, from a rare stranding in La Paz Bay in the Gulf of California, Mexico. Biological measurements and age estimation are provided by the analysis of photographs and growth in rings from vertebrae.

The optical properties of the water column have a significant influence on phytoplankton growth. In this work, we report selected optical property values of the waters of two regions in the southern Gulf of Mexico. Measurements of natural fluorescence and photosynthetically available radiation (PAR) were made during a multidisciplinary research cruise, enabling the subsequent calculation of the light extinction coefficient (k), compensation depth (Zc), critical depth (Zc), and compensation light intensity (Ec). The results revealed an interesting contrast between the two areas but also indicated the presence of optimal conditions for phytoplankton community growth and net primary production. These data, as reported here, could set the stage for the development of bio-optical models of light penetration, ocean color and primary productivity in the region, as well as for future analyses of organic carbon energy flow. However, many more studies are required to establish the possible seasonal variations in these parameters, which could be linked to the wide variability of the region.

Supplementing high levels of dietary crude protein in the absence of amino acid balance and enough energy in fish diets may results in reduced growth, improper feed intake and poor protein utilization efficiency coupled with unviable feed costs and adverse environmental effects due to high nitrogen excretion. It is necessary to improve the dietary protein quality to avoid unnecessary nitrogen excretion, and the use of protein as an energy source by fish, quality and determine proper dietary protein to energy (DP:DE) ratios in order to maximize protein utilization efficiency. It will help the aquaculture sector to obtain better growth response at a low-cost and without any adverse environmental effects. In the present article, we have deliberated in detail the previous and ongoing researches about protein research in fish nutrition. Besides, we have made a comparison between two so far commonly used methods in protein research, i.e., the graded supplementation and diet-dilution technique. According to the data presented here, is focusing on the formulation of balanced diets, the diet-dilution technique seems to be more accurate than the graded supplementation method. Thus, future studies should be focused on the use of diet-dilution technique along with proper dietary protein to energy ratios in order to formulate well-balanced diets. These attempts will significantly improve the protein and energy research in aquaculture nutrition. Moreover, feed industries will become able to formulate biologically balanced and environment-friendly diets at a low cost. 

The effects of a diet supplemented with 5% marine fish oil, 5% refined palm oil, 5% soybean oil, and a combination of the three on reproductive parameters of females Rhamdia quelen was investigated. Spawning was artificially induced to evaluate rates of fertilization, hatching and larvae normality. Fatty acid profiles of the diets, ovaries and oocytes were determined. A higher spawning rate (%) was observed for diets containing fish oil (78.65 ± 3.60) and palm oil (77.15 ± 3.97), followed by oil mix (65.46 ± 4.57). The diet containing soybean oil was associated with significantly lower fertilization (60.14 ± 5.66; P < 0.05) than the palm and fish oil diets. Lower fertilization may be explained by a high level of n-6 fatty acids in the diet, which possibly accelerate the oocyte maturation. Satisfactory fecundity (P > 0.05) were observed for all tested diets, whit 289.77 ± 23.90 (palm oil) until 323.31 ± 38.45 oocytes g-1 body weight (fish oil). The treatments were not shown to influence oocyte size, larval size or rate of larva deformity. Oocyte fatty acid composition was like that of gonads. Docosahexaenoic (DHA; C22:6 n-3) fatty acid was preferentially deposited in ovaries and oocytes. Ratios of n3/n6, DHA/EPA, EPA/ARA, did not affect the reproductive performance of females. Therefore, regarding female reproductive performance, the vegetable lipid sources tested are suitable for being used in R. quelen diet, and palm oil, in particular, is considered an excellent alternative to fish oil.

This study compared survival, growth, feed conversion rate (FCR) and harvested biomass of two commercial strains of tilapia (Oreochromis niloticus) cultivated in Mexico: Spring Genetic-Benchmark Holding® originated from the Genetically Improved Farmed Tilapia GIFT (Genebank: GIFT GU477624.1) and strain B from different line-breeding (Genebank: Philippines GU477626.1, Guangdong GU477627.1, and America GU477628.1). The study was performed in six geomembrane ponds (2,520 m3; 30×40×1.5 m) with supplementary aeration, in Los Pozos farm, El Rosario, Sinaloa, Mexico. In July 2016, 26,762 ± 170 fries of each strain (2.9 ± 0.1 g and 5.4 ± 0.2 cm) were cultivated in the nursery under similar conditions in triplicate at 11 ind m-3 for 34 days; then, they were transferred to the grow-out ponds and fed with 30% crude protein balanced feed (Purina®) at a rate of 12% live weight day-1 in three rations (07:00, 12:00 and 17:00 h) for 123 days. The results showed that Spring had a lower variation coefficient (VC) and higher survival, growth rate in weight, initial and final size, and harvested biomass. Survival was 30.7% greater in Spring and doubled harvested biomass (Spring 10 ± 0.8 t ha-1 vs. B strain 5 ± 4.7 t ha-1). Sixty percent of the Spring population reached a commercial weight of 500 g in day 123th of cultivation compared with 20% of B population in the same period. Except for FCR, VC was lower in the Spring strain. Differences in productive parameters were probably due to the genetic selection programs at which both strains were subjected.

Tropical gar (Atractosteus tropicus) aquaculture is a potential economic activity in southeast Mexico. This study analyzed the economic profitability of tropical gar grow-out using two commercial feeds (Silver Cup® and Super®). The last one was designed based on the digestive physiology of the species. The experiment was conducted in six concrete ponds of 4 m3 (two treatments with three replicates) for 210 days; in each experimental unit 40 juveniles were stocked with an initial average weight and a total length of 104 ± 10 g and 27.7 ± 0.88 cm, respectively. At the end of the grow-out, there were statistics differences (P < 0.05) among treatments, where fish fed with Silver Cup® obtained the highest final average weight and total length (450.29 ± 5.36 g and 41.7 ± 1.81 cm, respectively), compared with fish fed Super®, which obtained a final average weight and total length of 415.05 ± 5.38 g and 41.4 ± 1.57 cm. Proximal analysis indicated a better protein content and fewer lipids in fish fed with Super®. The profitability analysis showed that fish fed with Silver Cup® diet had the highest values, with a Net Present Value (NPV) = US$55,332.63, Cost/Benefit (C/B) = US$1.5 and Internal Return Rate (IRR) = 48.38%, while for fish fed with Super® diet was NPV = US$50,852.28, C/B = US$1.49 and IRR = 47.03%. In conclusion, it is considered that both grow-out foods are profitable, although better nutritional value and less production cost are using Super® diet.