Metagenomic insight into taxonomic composition, environmental filtering and functional redundancy for shaping worldwide modern non-lithifying microbial mats.

Modern microbial mats are relictual communities mostly found in extreme environments worldwide. Despite their significance as representatives of the ancestral Earth and their important roles in biogeochemical cycling, research on microbial mats has largely been localized, focusing on site-specific descriptions and environmental change experiments. Here, we present a global comparative analysis of non-lithifying microbial mats, integrating environmental measurements with metagenomic data from 62 samples across eight sites, including two new samples from the recently discovered Archaean Domes from Cuatro Ciénegas, Mexico. Our results revealed a notable influence of environmental filtering on both taxonomic and functional compositions of microbial mats. Functional redundancy appears to confer resilience to mats, with essential metabolic pathways conserved across diverse and highly contrasting habitats. We identified six highly correlated clusters of taxa performing similar ecological functions, suggesting niche partitioning and functional specialization as key mechanisms shaping community structure. Our findings provide insights into the ecological principles governing microbial mats, and lay the foundation for future research elucidating the intricate interplay between environmental factors and microbial community dynamics.

Extraction methods and nutritional characterization of protein concentrates obtained from bean, chickpea, and corn discard grains.

Protein concentrates obtained from discarded grain flours of white chickpea Sinaloa (Cicer arietinum) (CC), "Azufrazin" bean (Phaseolus vulgaris) (BC), and white corn (Zea mays) (MC), were characterized biochemically through bromatological analyses (protein, lipid, fiber, moisture, ashes, and nitrogen free extract), HPLC techniques (amino acids content), and spectrophotometry (anti-nutrients: phytic acid, trypsin inhibitors, and saponins). The percentage of protein obtained from CC, BC, and MC was 71.23, 81.10, and 55.69%, respectively. Most peptides in the BC and CC flours had a molecular weight of <1.35 kDa, meanwhile, MC peptides were heavier (1.35 to 17 kDa). The amino acids (AA) profile of flours and protein concentrates were similar; however, all the protein concentrates showed an increased AA accumulation (300 to -400%) compared with their flours. The protein concentrates from BC registered the highest AA accumulation (77.4 g of AA/100 g of protein concentrates). Except for the phytic acid in CC and trypsin inhibitor in CC and MC, respectively, the rest of the protein concentrates exhibited higher amounts of the anti-nutrients compared with their flours; however, these levels do not exceed the reported toxicity for some animals, mainly when used in combination with other ingredients for feed formulations. It is concluded that CC and BC protein concentrates showed better nutritional characteristics than MC (level of protein, size of peptides, and AA profile). After biochemical characterization, protein concentrates derived from by-products have nutritional potential for the animal feed industry.

Mercury and selenium in oysters Saccostrea palmula and Crassostrea corteziensis from coastal lagoons of the southeastern Gulf of California: molar ratio and risk assessment on human health.

Total mercury (Hg) and selenium (Se) contents were determined in oysters Saccostrea palmula and Crassostrea corteziensis soft tissues from four coastal lagoons of the southeastern Gulf of California. The annual Hg mean concentrations for S. palmula (0.09 ± 0.04 µg g- 1, wet weight) and C. corteziensis (0.08 ± 0.04 µg g- 1) were similar (p ˃ 0.05) among the lagoons and did not exceed the limit established by the Norma Oficial Mexicana and World Health Organization (< 1.0 µg g- 1 Hg). On the other hand, the annual mean concentrations of Se for S. palmula (3.34 ± 0.96 µg g- 1) and C. corteziensis (2.79 ± 0.89 µg g- 1) were higher (p < 0.05) in El Colorado lagoon. The Se/Hg molar ratios were above 1; the positive selenium health benefit value index suggested that Se load in oysters could reduce the Hg potential toxic effect. The hazard quotient for Hg in both species was below 1. Therefore, the consumption of oysters does not represent a risk due to Hg ingestion.

Histopathological alterations in the gonads of wild white clams Dosinia ponderosa inhabiting a former copper mine locality in the Gulf of California.

OBJECTIVE: Prolonged exposure to heavy metals, such as Pb, Hg, or Cu, has multiple adverse effects on marine organisms at the cellular, physiological, and population levels. Bivalves' histopathology provides a sensitive biomarker of pollutant-induced stress and environmental health. Gonad tissue deterioration is of particular concern, as it affects the reproductive success of a species. This study aimed to examine the histopathological alterations caused by metal exposure in the gonad of the white clam Dosinia ponderosa. METHODS: Organisms were sampled from three locations in the Gulf of California: Santa Rosalia (SR), a former Cu mining town; San Lucas beach (SL), a nearby site influenced by pollution; and Escondida beach (EB), which served as a control site. Histological and histochemical stains were used, and the prevalence and intensity level of each alteration were calculated. RESULT: The prevalence of alterations was higher in the ovaries of SR clams (92% compared to 60% in SL clams and 32.7% in EB clams), during spawning (91.4% compared to 20% in SL clams and 4.7% in EB clams), and in winter (93.5% compared to 30% in SL clams and 17.4% in EB clams). CONCLUSION: These findings suggest a significant deterioration in the gonads of white clams from SR, probably linked to the chronic exposure to high concentrations of Cu and possibly other heavy metals; hence, the reproductive health of the clams is likely compromised.

Biomonitoring of potentially toxic elements through oysters (Saccostrea palmula and Crassostrea corteziensis) from coastal lagoons of Southeast Gulf of California, Mexico: health risk assessment.

The coastal lagoons of the Gulf of California support important traditional fisheries and mollusc cultures (generally oysters) and receive important volumes of agricultural, industrial and urban effluents, consumption of the oysters could pose risk to human health. The concentrations of arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), and zinc (Zn) in the oysters Saccostrea palmula and Crassostrea corteziensis, from four coastal lagoons (Altata, AL; Macapule, ML; Navachiste, NL; El Colorado, ECL) in the Southeast Gulf of California, were seasonally evaluated (summer 2019-spring 2020). The order of magnitude of potentially toxic elements concentrations in the soft tissue in both oyster species and at all sites was Zn > Fe > Cu > As > Cd > Pb. Cadmium, Cu, Pb, and Zn exceeded the maximum permissible limits in more than one sampling site. The highest concentrations (mg kg-1, wet weight) of As (4.2 ± 1.1, spring) and Cd (3.3 ± 0.7, autumn) were registered in S. palmula et al. and NL sampling sites, respectively. Crassostrea corteziensis presented higher levels of Cu (40.5 ± 6.7, spring), Pb (2.0 ± 0.4, spring), and Zn (96.9 ± 20.4, spring) in ECL and Fe (62.2 ± 25.4, autumn) in ML. The hazard quotient (HQ) values exceeded the safe level of 1 for Cd in S. palmula and C. corteziensis in NL for children (~ 16 kg weight). In addition, in children, the hazard index (HI) values in both species of oysters ranged from 0.7 to 2.1 and 0.6 to 1.9, respectively. On the other hand, the intake of the studied elements through the consumption of oysters would not induce adverse effects to human health (men and women weighing 70 and 60 kg, respectively); HQ and HI values were < 1.

Recent Differentiation of Aquatic Bacterial Communities in a Hydrological System in the Cuatro Ciénegas Basin, After a Natural Perturbation.

Pozas Rojas is a hydrological system comprising nine isolated shallow ponds and a deep lagoon, which were temporally merged in 2010 by increased rainfall due to a tropical cyclone. In this work, we assess which components, biotic interactions, or environment filtering effects, drive the assembly of microbial communities after a natural perturbation. Arsenic, pH, and temperature are among the most significant environmental variables between each pond, clustering the samples in two main groups, whereas microbial composition is diverse and unique to each site, with no core at the operational taxonomic unit level and only 150 core genera when studied at the genus level. Los Hundidos lagoon has the most differentiated community, which is highly similar to the epipelagic Mediterranean Sea communities. On the other hand, the shallow ponds at the Pozas Rojas system resemble more to epicontinental hydrological systems, such as some cold rivers of the world and the phreatic mantle from Iowa. Overall, despite being a sole of water body 2 years prior to the sampling, interspecific interactions, rather than environmental selection, seem to play a more important role in Pozas Rojas, bolstered by founder effects on each poza and subsequent isolation of each water body.

Gonadal development and sexuality of Larkinia grandis (Arcida: Arcidae) inhabiting southeastern Gulf of California

Larkinia grandis (Broderip & G.B. Sowerby I, 1829), an important fishing resource for Mexican communities, is an Arcidae clam. It is also considered a species with aquaculture potential. In this work we investigated the gonadal phases and sexuality in a population of L. grandis in the Gulf of California. Our findings support the hypothesis that there is one male per female in the population studied. It also documents that the shape, position and color of the gonads of L. grandis are consistent with observations in other Arcidae species. Additionally, five gonadal phases are differentiated and described in males and females (development, mature, spawning, post-spawning and resting), with a noticeable presence of brown cells during post-spawning and the onset of the resting phase, suggesting that those cells are involved in the reabsorption of remnants. Additionally, asynchronous gametogenesis in males, synchronic gametogenesis in females and batch spawning are defined. The results of this contribution can be used in the efforts to protect this bivalve.

Gonadal development and sexuality of Larkinia grandis (Arcida: Arcidae) inhabiting southeastern Gulf of California

ABSTRACT Larkinia grandis (Broderip & G.B. Sowerby I, 1829), an important fishing resource for Mexican communities, is an Arcidae clam. It is also considered a species with aquaculture potential. In this work we investigated the gonadal phases and sexuality in a population of L. grandis in the Gulf of California. Our findings support the hypothesis that there is one male per female in the population studied. It also documents that the shape, position and color of the gonads of L. grandis are consistent with observations in other Arcidae species. Additionally, five gonadal phases are differentiated and described in males and females (development, mature, spawning, post-spawning and resting), with a noticeable presence of brown cells during post-spawning and the onset of the resting phase, suggesting that those cells are involved in the reabsorption of remnants. Additionally, asynchronous gametogenesis in males, synchronic gametogenesis in females and batch spawning are defined. The results of this contribution can be used in the efforts to protect this bivalve.

Gonadal development and sexuality of Larkinia grandis (Arcida: Arcidae) inhabiting southeastern Gulf of California

Larkinia grandis (Broderip & G.B. Sowerby I, 1829), an important fishing resource for Mexican communities, is an Arcidae clam. It is also considered a species with aquaculture potential. In this work we investigated the gonadal phases and sexuality in a population of L. grandis in the Gulf of California. Our findings support the hypothesis that there is one male per female in the population studied. It also documents that the shape, position and color of the gonads of L. grandis are consistent with observations in other Arcidae species. Additionally, five gonadal phases are differentiated and described in males and females (development, mature, spawning, post-spawning and resting), with a noticeable presence of brown cells during post-spawning and the onset of the resting phase, suggesting that those cells are involved in the reabsorption of remnants. Additionally, asynchronous gametogenesis in males, synchronic gametogenesis in females and batch spawning are defined. The results of this contribution can be used in the efforts to protect this bivalve.(AU)

Reporte de presuntas hipnosporas de Perkinsus sp, en Megapitaria squalida del Golfo de California con la técnica de tinción con tioglicolato / Report of presumptive Perkinsus sp hypnospores in Megapitaria squalida of the Gulf of California with the thioglycollate staining technique

RESUMEN Objetivo. Detectar la presencia de presuntas hipnosporas del protozoario Perkinsus sp. en una población silvestre de la almeja chocolata mexicana (Megapitaria squalida) del sureste del Golfo de California, usando el medio fluido de tioglicolato de Ray (RFTM). Materiales y métodos. Cada mes durante un ciclo anual, se capturaron 30 especímenes con una longitud entre 56.17 y 69.04 mm. La prevalencia e intensidad de la infección y los parámetros del agua se registraron mensualmente desde septiembre 2012 a septiembre 2013. Resultados. Se detectó la presencia de presuntas hipnosporas de Perkinsus sp. en muestras de tejido de la almeja chocolata mexicana usando la prueba RFTM, por la presencia de corpúsculos redondos y oscuros que representan hipnosporas del parásito. Los muestreos mensuales revelaron un rango de prevalencia e intensidad de la infección de 0-43.33% y 1-4 (infección negativa = 0 hipnosporas/preparación, a moderada = 34 hipnosporas/ preparación), respectivamente. Conclusiones. Perkinsus sp. es reportado por primera vez en una población silvestre de M. squalida en la parte más al sureste del Golfo de California. Los resultados indican que el parásito está disperso intraespecíficamente y, potencialmente, parasitaría un nuevo huésped en la región.

ABSTRACT 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.

Evolutionary Rescue of an Environmental Pseudomonas otitidis in Response to Anthropogenic Perturbation.

Anthropogenic perturbations introduce novel selective pressures to natural environments, impacting the genomic variability of organisms and thus altering the evolutionary trajectory of populations. Water overexploitation for agricultural purposes and defective policies in Cuatro Cienegas, Coahuila, Mexico, have strongly impacted its water reservoir, pushing entire hydrological systems to the brink of extinction along with their native populations. Here, we studied the effects of continuous water overexploitation on an environmental aquatic lineage of Pseudomonas otitidis over a 13-year period which encompasses three desiccation events. By comparing the genomes of a population sample from 2003 (original state) and 2015 (perturbed state), we analyzed the demographic history and evolutionary response to perturbation of this lineage. Through coalescent simulations, we obtained a demographic model of contraction-expansion-contraction which points to the occurrence of an evolutionary rescue event. Loss of genomic and nucleotide variation alongside an increment in mean and variance of Tajima's D, characteristic of sudden population expansions, support this observation. In addition, a significant increase in recombination rate (R/θ) was observed, pointing to horizontal gene transfer playing a role in population recovery. Furthermore, the gain of phosphorylation, DNA recombination, small-molecule metabolism and transport and loss of biosynthetic and regulatory genes suggest a functional shift in response to the environmental perturbation. Despite subsequent sampling events in the studied site, no pseudomonad was found until the lagoon completely dried in 2017. We speculate about the causes of P. otitidis final decline or possible extinction. Overall our results are evidence of adaptive responses at the genomic level of bacterial populations in a heavily exploited aquifer.

Desove y desarrollo intracapsular del caracol marino Hexaplexnigritus (Neogastropoda: Muricidae) en laboratorio / Spawning and intracapsular development of the marine snail Hexaplex nigritus (Neograstropoda: Muricidae) in the laboratory

Introducción: El caracol marino Hexaplex nigritus es un murícido fuertemente explotado en el Golfo de California para consumo y artesanías. Cuando se reproducen, los adultos se agregan en forma de arrecifes artificiales facilitando su identificación y extracción, lo cual, ha mermado su población en dicha zona. Objetivo: Investigar el desove y desarrollo intracapsular y larvario de esta especie como herramientas para su producción en cautiverio con fines de repoblamiento. Métodos: Se recolectaron 18 progenitores que fueron mantenidos en un sistema cerrado con parámetros y alimentación controladas durante abril 2017 hasta septiembre 2018. Se registró: crecimiento de progenitores, desove de masas ovígeras, cantidad de cápsulas y número de embriones y larvas dentro de las cápsulas. La temperatura de incubación fue de 28.2 ± 1.5 °C. Las principales estructuras morfológicas de embriones y larvas fueron documentadas conforme su desarrollo. Resultados: El desarrollo embrionario intracapsular y de la larva velígera hasta su asentamiento tuvieron una duración de 14-15 y 31-32 días, respectivamente. Cada hembra de 80-88 mm de longitud produjo alrededor de 4 masas ovígeras, 627 cápsulas y 663 993 larvas velígeras extracapsulares por año. Conclusiones: La fácil adaptación y el potencial reproductivo mostrado por H. nigritus en laboratorio se presentan como estrategias promisorias para su repoblación y conservación.

Introduction: The marine snail Hexaplex nigritus is a heavily exploited muricid in the Gulf of California for consumption and handcrafts. When they reproduce, adults aggregated in the form of artificial reefs facilitating their identification and extraction, situation that has reduced their population in that area. Objective: In order to investigate the spawning and intracapsular and larval development of this species as tools for its production in captivity for repopulation purposes. Methods: Eighteen brooders were collected and kept in a closed system with controlled parameters and feeding from April 2017 to September 2018. Growth of parents, spawning of ovigerous masses, number of capsules, and number of embryos and larvae within the capsules, were registered. The main morphological structures of embryos and larvae were documented according to their development. Results: Intracapsular embryonic development and veliger larva until its establishment lasted 14-15 and 31-32 days, respectively. Each 80-88 mm length female produced around 4 ovigerous masses, 627 capsules and 663 993 extracapsular veliger larvae per year. Conclusions: Easy adaptation and reproductive potential shown by H. nigritus in the laboratory are presented as promising strategies for its repopulation and conservation.

Sexual and reproductive traits of the pearl oyster shrimp Pontonia margarita (Decapoda: Palemonidae), symbiotically inhabiting the mantle cavity of the rugose pen shell Pinna rugosa (Bivalvia: Pinnidae)

Symbiosis between decapods and mollusks provides a unique opportunity to examine some of the evolutionary strategies employed by marine invertebrates. We describe the sexual and reproductive traits of the pearl oyster shrimp, Pontonia margarita Verril, 1869, found symbiotically inhabiting the mantle cavity of the rugose pen shell, Pinna rugosa Sowerby, 1835. Solitary males and females (ovigerous and non-ovigerous) and heterosexual pairs (with ovigerous and non-ovigerous females) were found in a total of 47 rugose pen shells collected from a sandy area with seagrass meadows on the southeastern coast of the Gulf of California, Mexico. The body length (BL) of female P. margarita was correlated with the shell volume of their rugose pen shell host. The sex ratio was female-biased (0.85M:1F). Female P. margarita were larger than their male counterparts in terms of BL, cephalothorax length (CL), and the maximum chelae length of the second pereopod (MCL). The CL and MCL were more strongly correlated for males (r = 0.70, p = 0.01). The number and volume of eggs per ovigerous female varied from 95 to 1,571 and from 5.46 ± 0.48 to 8.85 ± 0.97 mm3, respectively. Our results indicate polygamous behavior and social monogamy among P. margarita, and a short-term pairing system for their association with P. rugosa.(AU)

Two Pseudomonas aeruginosa clonal groups belonging to the PA14 clade are indigenous to the Churince system in Cuatro Ciénegas Coahuila, México.

Pseudomonas aeruginosa is a widely distributed environmental bacterium but is also an opportunistic pathogen that represents an important health hazard due to its high intrinsic antibiotic resistance and its production of virulence factors. The genetic structure of P. aeruginosa populations using whole genome sequences shows the existence of three clades, one of which (PA7 clade) has a higher genetic diversity. These three clades include clinical and environmental isolates that are very diverse in terms of geographical origins and isolation date. Here, we report the characterization of two distinct clonal P. aeruginosa groups that form a part of the PA14 clade (clade 2) sampled from the Churince system in Cuatro Ciénegas Basin (CCB). One of the clonal groups that we report here was isolated in 2011 (group 2A) and was displaced by the other clonal group (2B) in 2015. Both Churince groups are unable to produce pyoverdine but can produce other virulence-associated traits. The existence of these unique P. aeruginosa clonal groups in the Churince system is of ecological and evolutionary significance since the microbiota of this site is generally very distinct from other lineages, and this is the first time that a population of P. aeruginosa has been found in CCB.

Sexual and reproductive traits of the pearl oyster shrimp Pontonia margarita (Decapoda: Palemonidae), symbiotically inhabiting the mantle cavity of the rugose pen shell Pinna rugosa (Bivalvia: Pinnidae)

Symbiosis between decapods and mollusks provides a unique opportunity to examine some of the evolutionary strategies employed by marine invertebrates. We describe the sexual and reproductive traits of the pearl oyster shrimp, Pontonia margarita Verril, 1869, found symbiotically inhabiting the mantle cavity of the rugose pen shell, Pinna rugosa Sowerby, 1835. Solitary males and females (ovigerous and non-ovigerous) and heterosexual pairs (with ovigerous and non-ovigerous females) were found in a total of 47 rugose pen shells collected from a sandy area with seagrass meadows on the southeastern coast of the Gulf of California, Mexico. The body length (BL) of female P. margarita was correlated with the shell volume of their rugose pen shell host. The sex ratio was female-biased (0.85M:1F). Female P. margarita were larger than their male counterparts in terms of BL, cephalothorax length (CL), and the maximum chelae length of the second pereopod (MCL). The CL and MCL were more strongly correlated for males (r = 0.70, p = 0.01). The number and volume of eggs per ovigerous female varied from 95 to 1,571 and from 5.46 ± 0.48 to 8.85 ± 0.97 mm3, respectively. Our results indicate polygamous behavior and social monogamy among P. margarita, and a short-term pairing system for their association with P. rugosa.

Use of a mixture of vegetal (Jatropha curcas) and animal (fish silage) byproducts as protein source in shrimp (Litopenaeus vannamei) diets

This study evaluated growth responses of white shrimp Litopenaeus vannamei by testing different combinations of Jatropha curcas kernel meal (JCK) and tilapia waste silage (FS) as dietary protein sources under laboratory and pond conditions. A reference diet (RD) based on fish meal was elaborated to contain 35% crude protein and 434 kcal/g; then, five isoproteic and isoenergetic experimental diets were formulated from RD with different FS/JCK proportions as follows: 75%FS/0%JCK; 56.25%FS/13.25%JCK; 26.5%FS/30.89%JCK; 18.75%FS/39.75%JCK; and 0%FS/53%JCK. For the laboratory trial, shrimp (2.90 g) were stocked at 10 m2 in an indoor recirculating system during 90 days. There were differences among the growth parameters of diets. Mean weight gain fluctuated from 6.71±0.61 g observed for the shrimp fed the 75%FS/ 0%JCK diet, to 9.70±0.61 g for the group fed the RD. The RD and 18.75%FS/39.75%JCK diet obtained the highest mean final weight (above 12 g), weight gain (above 9 g), and specific growth rate values (above 1.6%/day). Average final survival was 90.97%. The RD and 18.75%FS/39.75%JCK diets were used for the pond trial. Shrimp (0.49 g) were stocked at 10 m2 within 1-m3 cages into the pond for 35 days. Weight gain (3.47 g) and survival (93.33%) of shrimps were similar between the diets. Quadratic equations with the laboratory data indicated that the maximum responses for growth parameters correspond to FS and JKC inclusion levels in the range of 27.83 to 29.00%, and 32.25 to 33.64%, respectively. A combination of 18.75% FS/39.75%JCK meals as protein source is a potential alternative to effectively substitute FM in practical diets for L. vannamei at the studied ages under both laboratory and pond conditions.(AU)

Heavy metal concentrations in diploid and triploid oysters (Crassostrea gigas) from three farms on the north-central coast of Sinaloa, Mexico.

The concentrations of Cu, Cd, Pb, Zn, and Hg in diploid and triploid oysters from three farms (Guasave, Ahome, and Navolato) on the north-central coast of Sinaloa, Mexico, were assessed based on samples recovered during a single culture cycle 2013-2014. Metal burdens were more strongly correlated (p < 0.05) with the location of the farm than with either the ploidy or the interaction of both variables. The metal concentration ranking for oysters of both ploidies from the three farms was Zn > Cu > Cd > Pb > Hg. For all three farms, the mean concentrations of Cd and Pb in Crassostrea gigas were high, ranging from 2.52 to 7.98 µg/g wet weight for Cd and from 0.91 to 2.83 µg/g wet weight for Pb. Diploid and triploid oysters from the Guasave farm contained high levels of Cu (76.41 and 68.97 µg/g wet weight, respectively). Cu, Cd, and Zn were highly correlated (p < 0.05), and their concentrations may be influenced by agrochemical inputs. The mean levels of Cu for the Guasave farm and of Cd and Pb for all three farms exceeded permissible limits and represented a threat to human health during the sampling period (July 2014 to July 2014).

Reproduction of Megapitaria squalida (Bivalvia: Veneridae) in the Southeast Gulf of California, Mexico / Reproducción de la almeja callista Megapitaria squalida (Bivalvia: Veneridae) en el sureste del Golfo de California, México

AbstractBivalves 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. Rev. Biol. Trop. 65 (3): 881-889. Epub 2017 September 01.

ResumenEl ciclo reproductivo de los bivalvos varía de acuerdo a las condiciones ambientales de cada lugar, y representa información importante para su conservación. Se estudió el ciclo reproductivo de la almeja Megapitaria squalida utilizando cortes histológicos de la gónada y cambios en el número y tamaño de los oocitos, en el sur del Golfo de California (Bahía Altata, Sinaloa, México), desde junio 2013 a junio 2014. El análisis histológico de las gónadas, mostró eventos de desove todo el año con dos picos: el primero fue registrado en octubre acompañado con un fuerte decremento en peso de los animales; el segundo en febrero caracterizado por un alto porcentaje de desove en la población. Se observó un periodo de reposo en diciembre. La proporción sexual (hembras:machos) de la población de almejas fue 1.08:1 (χ2 = 5.72, g.l. = 1, P < 0.05). El número y tamaño promedio de los oocitos mostró diferencias (P < 0.05) entre los muestreos mensuales, y fluctuaron de 34.6 ± 5.8 µm en junio 2014 a 41.9 ± 6.8 µm en febrero 2014, y de 443.8 ± 424.5 en febrero 2014, a 1 214.4 ± 267.6 en abril 2014. Se propone una temporada de veda desde octubre a noviembre, ya que en estos meses la liberación de gametos por la población fue más intensa.

Bioprocessing of common beans in diets for tilapia: in vivo digestibility and antinutritional factors.

BACKGROUND: Bioprocessing of ingredients by solid-state fermentation is a low-cost technique for preparing diets. It is performed by adding microorganisms such as Rhizopus oligosporus to bean grains, achieving minimal degradation of nutrients and a significant improvement in digestibility. In particular, fermentation induces favorable changes in beans by reducing enzyme inhibitors, such as phytates and tannins. RESULTS: Fermentation significantly (P < 0.05) increased the protein content and digestibility of dry matter and protein compared with whole bean grains, and decreased the content of lipids, ash and phytic acid. Hardening did not have a significant (P > 0.05) effect on the chemical content of beans and digestibility of diets. The dehulled bean meal significantly (P < 0.05) increased protein and lipid content and digestibility of dry matter and protein of beans, and decreased fiber, ash and tannin content. The chemical content of beans and digestibility of ingredients compare favorably with those reported by other authors, indicating the benefits of fermentation and dehulling. CONCLUSION: We concluded that bean meal obtained from fermentation or dehulling represents a low-cost alternative for diets for tilapia. © 2017 Society of Chemical Industry.