Effect of temporal thermal stress on Penaeus vannamei: Growth performance and physiological plasticity.

The present study evaluated the effect of temporal periods of hypothermia and hyperthermia, followed by an optimal temperature recovery phase on the growth, survival, and physiological response of Penaeus vannamei. Post-larvae were exposed to stress periods for 7 and 14 days at 22 °C and 32 °C each, followed by a recovery phase at 28 °C to complete seven experimental weeks, and were compared with a control group maintained at 28 °C. Weight gain, specific growth rate, feed intake, feed conversion ratio, and survival were weekly determined. Muscle, hepatopancreas, and hemolymph were sampled on the 14th day of the recovery phase for biochemical composition, and antioxidant and digestive enzyme activities determination. The shrimp presented a higher growth rate during short-term hyperthermia in contrast to shrimp under hypothermia that presented compensatory growth after thermal stress when the temperature was restored at 28 °C. Hyperthermia increased 12-13% the feed intake while this was diminished 21-29% by the hypothermia periods. Shrimp undergo metabolic adjustments following thermal stress, with short hypothermia increasing the lipase activity and lipid storage in the hepatopancreas, while short hyperthermia also enhances chymotrypsin activity and leads to higher protein and lipid accumulation. Conversely, prolonged hyperthermia induces greater energy consumption, depleting lipid and glycogen stores, while hypothermia causes scarce mobilization of energy reserves during recovery phase. Antioxidant enzyme activities were not affected by short-thermal stress (7d), while prolonged thermal stress (14d) significantly affected SOD, CAT, and GPx activities. The present study provides important insights into the physiological plasticity of P. vannamei during recovery from thermal stress.

Transcriptome profile in heat resilient Pacific oyster Crassostrea gigas families under thermal challenge.

Since the introduction of the Pacific oyster Crassostrea gigas in Baja California Sur, Mexico, its culture has faced environmental challenges, specifically increasing temperatures that result in high mortalities. The inter-tidal zone seawater temperature during a year at the Baja California Peninsula broadly ranges from 7 °C to 39 °C. Therefore, to understand how oysters respond to heat stress during daily temperature oscillations, heat-resistant (RR, father, and mother resistant) and heat-susceptible (SS, both parents susceptible) phenotypes families from a C. gigas breeding program were exposed to a thermal challenge. Based on a laboratory-simulated daily oscillatory thermal challenge (26 to 34 °C) for 30 days, RR phenotype presented differences compared to SS phenotype since the beginning (day 0) of the thermal challenge. Gene expression analyses revealed 1822 differentially expressed up-regulated transcripts in RR, related to functions of metabolic processes, biological regulation, and response to stimulus and signaling. At the end of the experiment (day 30), 2660 differentially expressed up-regulated transcripts were identified in RR. Functional analysis of the genes expressed indicates responses of regulation of biological processes and response to a stimulus. Additionally, 340 genes were differentially expressed among RR vs. SS from the beginning to the end of the thermal challenge, where 170 genes were up-regulated, and 170 were down-regulated. These transcriptomic profiles represent the first report to identify gene expression markers associated with RR phenotypes for the Pacific oyster to the future broodstock selection.

Transcriptome-based metabolic profiling of flavonoids in Agave lechuguilla waste biomass.

Agave lechuguilla is one of the most abundant species in arid and semiarid regions of Mexico, and is used to extract fiber. However, 85 % of the harvested plant material is discarded. Previous bioprospecting studies of the waste biomass suggest the presence of bioactive compounds, although the extraction process limited metabolite characterization. This work achieved flavonoid profiling of A. lechuguilla in both processed and non-processed leaf tissues using transcriptomic analysis. Functional annotation of the first de novo transcriptome of A. lechuguilla (255.7 Mbp) allowed identifying genes coding for 33 enzymes and 8 transcription factors involved in flavonoid biosynthesis. The flavonoid metabolic pathway was mostly elucidated by HPLC-MS/MS screening of alcoholic extracts. Key genes of flavonoid synthesis were higher expressed in processed leaf tissues than in non-processed leaves, suggesting a high content of flavonoids and glycoside derivatives in the waste biomass. Targeted HPLC-UV-MS analyses confirmed the concentration of isorhamnetin (1251.96 µg), flavanone (291.51 µg), hesperidin (34.23 µg), delphinidin (24.23 µg), quercetin (15.57 µg), kaempferol (13.71 µg), cyanidin (12.32 µg), apigenin (9.70 µg) and catechin (7.91 µg) per gram of dry residue. Transcriptomic and biochemical profiling concur in the potential of lechuguilla by-products with a wide range of applications in agriculture, feed, food, cosmetics, and pharmaceutical industries.

Isolation of the sex-determining gene Sex-lethal (Sxl) in Penaeus (Litopenaeus) vannamei (Boone, 1931) and characterization of its embryogenic, gametogenic, and tissue-specific expression.

The Pacific white shrimp Penaeus vannamei is the most cultured shrimp species around the world. Because females grow larger than males, the culture of 'only females' is of great interest, but knowledge on sex determination and differentiation is required for producing only females. In an effort to obtain information associated with reproduction in P. vannamei, transcriptomic data from female gonads was generated, and partial sequences of a transcript were identified as Sex-lethal (Sxl). Its characterization indicated that, differently from other penaeids in which this gene has been isolated, there are six isoforms of the Sxl transcript in P. vannamei (PvanSxl 1-6). These isoforms result from alternative splicing at three splice sites (SS1, SS2, SS3). The first splice-site is unique to P. vannamei, as it has not been reported for other Arthropod species; the second splice-site (SS2) is common among crustaceans, and the third splice-site (SS3) is also unique to P. vannamei and when spliced-out, it is always together with SS2. All isoforms are expressed during embryogenesis as well as gametogenesis of both genders. The two shorter isoforms, PvanSxl-5 and PvanSxl-6, which result from the splicing of SS2 and SS3, were found mostly expressed in adult testis, but PvanSxl-6 was also expressed in oocytes during gametogenesis. During oogenesis, the second largest isoform, PvanSxl-2, which splices-out only SS1, and PvanSxl-4 that splices-out SS1 and SS2 were highly expressed. These two isoforms were also highly expressed during embryonic development. In situ hybridization allowed pinpointing more specifically the cells where the PvanSxl transcripts were expressed. During embryogenesis, hybridization was observed from the one-cell stage embryo to late gastrula. In the female gonad in previtellogenesis, hybridization occurred in the nucleus of oocytes, whereas in secondary vitellogenesis the transcript also hybridized cytoplasmic granules and cortical crypts. Finally, in situ hybridization corroborated the expression of PvanSxl also in the male gonad during spermatogenesis, mostly occurring in the cytoplasm from spermatogonia and spermatocytes.

Use of seaweed Ulva lactuca for water bioremediation and as feed additive for white shrimp Litopenaeus vannamei.

Two experimental feeding trials were conducted during four weeks to evaluate the use of Ulva lactuca in shrimp culture: (1) for wastewater bioremediation, and (2) using different inclusion levels of U. lactuca meal in shrimp feed. In feeding trial 1, shrimp reared under seaweed U. lactuca water exchange in a re-circulation system (SWE) resulted in similar growth and feed utilization as shrimp reared with clean water exchange (CWE). Shrimp under no water exchange (NWE) resulted in significant lower growth and higher feed conversion rate (FCR) compared to the other treatments (p < 0.05). Nitrogen compounds and phosphate in water from SWE and CWE treatments did not present significant differences during the experimental trial (p > 0.05). In feeding trial 2, U. lactuca biomass produced by wastewater bioremediation in SWE treatment were dried and ground to formulate diets containing 0, 1, 2, and 3% U. lactuca meal (0UL, 1UL, 2UL, and 3UL). Shrimp fed the 3 UL diet resulted in a significant (p < 0.05) improvement of growth and FCR, and enhanced whole shrimp lipid and carotenoid content by 30 and 60%, respectively, compared to control diet. Seaweed U. lactuca is suggested as a desirable species for wastewater bioremediation in integrated aquaculture systems, and its meal as a good feed additive for farmed shrimp.

Sex determination and differentiation genes in a functional hermaphrodite scallop, Nodipecten subnodosus.

The lion-paw, Nodipecten subnodosus is one of three scallop species commercially exploited on the west coast of the Peninsula of Baja California. Because nothing is known about sex determination and sexual differentiation in hermaphrodite scallops, in the present work, a global transcriptomic analysis was performed in two early developmental stages, settling eyed-larvae and spat, as well as in three tissues (undifferentiated gonad, digestive gland, and adductor muscle). Over 27 million Illumina paired-end reads were obtained through the MiSeq platform. After processing the reads a total of 243,774 transcripts were assembled with an N50 of 980 and an average length of 775nt. A total of 43,252 proteins were inferred and 36,103 transcripts had at least one homolog in the SwissProt database according to a blastx search. After differential expression analyses and GO annotations it was possible to identify several sex-related genes in the scallop, including one known to be involved in the sex determination pathway of the hermaphrodite model organism Caenorhabditis elegans, N. subnodosus-sex1 (Ns-sex1). Other interesting sex determination and differentiation genes were Ns-dmrta2, Ns-sox9, Ns-wnt4, Ns-doa, Ns-ovo, Ns-vir, among others. Most of these genes were mainly expressed in the testis region, suggesting their participation in male gonad region sex differentiation. These results represent the first available information on the genetics of sex determination and differentiation in a functional hermaphrodite scallop.

Transcriptomic information from Pacific white shrimp (Litopenaeus vannamei) ovary and eyestalk, and expression patterns for genes putatively involved in the reproductive process.

The increased use of massive sequencing technologies has enabled the identification of several genes known to be involved in different mechanisms associated with reproduction that so far have only been studied in vertebrates and other model invertebrate species. In order to further investigate the genes involved in Litopenaeus vannamei reproduction, cDNA and SSH libraries derived from female eyestalk and gonad were produced, allowing the identification of expressed sequences tags (ESTs) that potentially have a role in the regulation of gonadal maturation. In the present study, different transcripts involved in reproduction were identified and a number of them were characterized as full-length. These transcripts were evaluated in males and females in order to establish their tissue expression profiles during developmental stages (juvenile, subadult and adult), and in the case of females, their possible association with gonad maturation was assessed through expression analysis of vitellogenin. The results indicated that the expression of vitellogenin receptor (vtgr) and minichromosome maintenance (mcm) family members in the female gonad suggest an important role during previtellogenesis. Additionally, the expression profiles of genes such as famet, igfbp and gpcr in brain tissues suggest an interaction between the insulin/insulin-like growth factor signaling pathway (IIS) and methyl farnesoate (MF) biosynthesis for control of reproduction. Furthermore, the specific expression pattern of farnesoic acid O-methyltransferase suggests that final synthesis of MF is carried out in different target tissues, where it is regulated by esterase enzymes under a tissue-specific hormonal control. Finally, the presence of a vertebrate type steroid receptor in hepatopancreas and intestine besides being highly expressed in female gonads, suggest a role of that receptor during sexual maturation.

Detection of white spot syndrome virus (WSSV) in the Pacific oyster Crassostrea gigas.

Oysters Crassostrea gigas were placed at water supply canals of three shrimp farms in Guasave, Mexico where WSSV outbreaks occur. Animals were sampled through April-August and September-December to detect WSSV DNA. By using three different PCR protocols, only oysters from a farm undergoing a WSSV outbreak were found WSSV-positive in gills and digestive gland. Two WSSV amplicons were sequenced and they corresponded over 99% to WSSV genome segments. Results showed that oysters can capture WSSV particles suspended in water. Susceptibility of oysters to WSSV infection and their role as a carrier remain to be determined.

Assessment of metallothioneins in tissues of the clam Megapitaria squalida as biomarkers for environmental cadmium pollution from areas enriched in phosphorite.

The aim of this study was to evaluate the use of metallothionein (MT) concentrations in tissues of the clam Megapitaria squalida as biomarkers of environmental cadmium (Cd) pollution from phosphorite enrichments in the marine environment, which resulted from mining activities in La Paz Bay, Baja California Sur, Mexico. Cd and MT were quantified in gills, digestive gland, and kidney of clams exposed to 0.2 or 0.5 mg Cd l(-1) for 10, 20, or 30 days. In addition, clams from four strategically selected natural sites of La Paz Bay were collected for analysis. In tissues of bioassayed and untreated clams, the gradient of Cd concentrations was digestive gland>>gills>kidney, whereas that of MT was digestive gland>gills>kidney. Digestive gland of the clams exposed to 0.5 mg Cd l(-1) for 30 days showed the highest concentrations of Cd (16.3+/-3.9 microg Cd g(-1)). The highest statistically significant MT concentrations were found in digestive gland at 10 days of exposure to Cd. In the untreated clams, one of the highest Cd concentrations, but not MT levels, was found in digestive glands of the organisms collected from the area close to phosphorite mining activities. For environmental monitoring, MT levels in digestive gland can be used as a first approximation of the presence of high levels of divalent metals in the environment. However, in this study, MT levels did not correlate with high Cd levels in clams that had been collected from areas associated with phosphorite enrichment.