In marine ectotherms, reproduction is an energetically expensive process that affects their thermal window tolerance. For most species, the impacts of hyperthermia during gametogenesis have still not ...been addressed. Our aim was to assess the metabolic response of adult Nodipecten subnodosus scallops to thermal challenges at early development (spring) and advanced gonad maturation (summer). Scallops collected in both seasons were exposed to acute hyperthermia (26 and 30 °C, 24 h), maintaining a group of scallops at acclimation temperature (22 °C) as a control condition. During the summer, relatively low activity of hexokinase (HK), as well as low levels of ATP and GTP were found in the adductor muscle, suggesting a shift in energy investment for reproduction, although arginine phosphate (ArgP) levels were higher in summer scallops. Hyperthermia (30 °C) induced an increased energy expenditure reflected by a transitory enhanced oxygen consumption (VO
) and relatively high activities of HK and arginine kinase (AK). Moreover, a slight decrease in adenylic energy charge (AEC) was partially compensated by a decrease in ArgP. An increase in nucleotide by-products inosine monophosphate (IMP) and hypoxanthine (HX) indicated a thermal stress at 30 °C. Some of the responses to acute hyperthermia were more pronounced at advanced maturation stages (summer scallops), indicating a possible lack of energy balance, with possible implications in animals challenged to global warming scenario.
Abstract
Photonic integrated circuits currently use platform intrinsic thermo-optic and electro-optic effects to implement dynamic functions such as switching, modulation and other processing. ...Currently, there is a drive to implement field programmable photonic circuits, a need which is only magnified by new neuromorphic and quantum computing applications. The most promising non-volatile photonic components employ phase change materials such as GST and GSST, which had their origin in electronic memory. However, in the optical domain, these compounds introduce significant losses potentially preventing a large number of applications. Here, we evaluate the use of two newly introduced low loss phase change materials, Sb
2
S
3
and Sb
2
Se
3
, on a silicon nitride photonic platform for future implementation in neuromorphic computing. We focus the study on Mach–Zehnder interferometers that operate at the O and C bands to demonstrate the performance of the system. Our measurements show an insertion loss below 0.04 dB μm
−1
for Sb
2
S
3
and lower than 0.09 dB μm
−1
for Sb
2
Se
3
cladded devices for both amorphous and crystalline phases. The effective refractive index contrast for Sb
2
S
3
on SiNx was measured to be 0.05 at 1310 nm and 0.02 at 1550 nm, whereas for Sb
2
Se
3
, it was 0.03 at 1310 nm and 0.05 at 1550 nm highlighting the performance of the integrated device.
The crustacean hyperglycemic hormone (CHH) family is an important group of neuropeptides involved in controlling growth, reproduction, and stress response in decapod species. In this study, a new ...gene containing 4 exons-3 introns flanked by canonical 5′-GT-AG-3′ intron splice-site junctions was isolated from Litopenaeus vannamei. Two full length transcripts of this CHH were isolated from eyestalk and pericardial tissue of males and females using rapid amplification of cDNA ends (RACE). Transcripts sequences were 1578bp in length in males pericardial tissues and in males and females eyestalk with 100% identity, but the transcript isolated from females pericardial tissues was shorter (974bp). The differences in transcripts length is a result of two polyadenylation sites present in the 3'UTR resulting in two transcription termination signals. Transcript sequences encoded one unique protein that can be classified as type I CHH subfamily because of the 4 exons and 3 introns structure, although the CPRP region is not-well conserved and there is no amidation in the C-terminal of the deduced amino acid sequence. Furthermore, there is a glycine inserted in the mature peptide not at position 12 as in type II CHHs but after amino acid 31 and the phylogenetic analysis did not group the peptide within type I, but closer to type II CHHs. We demonstrated by endpoint-PCR, qPCR, and in situ hybridization (ISH), that this gene is expressed in neuroendocrine organs known to express CHHs in penaeid shrimp, including X-organ and optic nerve in eyestalk, supraesophageal ganglion (SoG), but it is also expressed in other organs as gill, gut, pericardial cavity, as well as in terminal ampoule or spermatophore and vas deferens of males.
•We isolated a novel CHH gene from the Pacific White shrimp.•Phylogenetic analysis indicated it is not a strict type I or type II CHH.•Expressed in eyestalk, brain, heart, gills, gut, and males ductus deferens and spermatophore•It might function in osmoregulation, ion exchange and water uptake
Understanding the nature and origins of food sources supporting coastal lagoon-inhabiting organisms is necessary to evaluate the ecological status of such ecosystems. The trophic ecology of a bivalve ...species Spondylus crassisquama was studied in the Ojo de Liebre lagoon (Baja California, Mexico), combining stable isotope (SI), fatty acid (FA) and sterol analyses along a transect under oceanic influences. The second objective of the study was to investigate if sterol compositions give complementary information to those obtained from FA and SI. Temporal and spatial patterns of the three biomarkers in bivalve tissues suggest oceanic inputs at the mouth of the lagoon, while the inner station was characterized by a contribution of local sources including an important role of micro heterotrophs. This study revealed that the association of lipid biomarkers provide higher taxonomic resolution of the spatiotemporal heterogeneity in nutrient sources influencing the trophic functioning of a large coastal lagoon.
•Stable isotopes fatty acids and sterols were used to characterize the diet of bivalves.•A transect was sampled in a coastal lagoon with increasing distance from the mouth.•Bivalves at the entrance of the lagoon relied on oceanic phytoplankton inputs.•Bivalves in the inner lagoon relied on local microbial food web.•Lipid biomarkers and SI were complementary to distinguish the food sources origins.
High temperature increases energy demand in ectotherms, limiting their physiological capability to cope with hypoxic events. The present study aimed to assess the metabolic tolerance of juvenile ...Nodipecten subnodosus scallops to acute hyperthermia combined with moderate hypoxia. A previous study showed that juveniles exhibited a high upper temperature limit (32 °C), but the responses of juveniles to combined hyperthermia and low dissolved oxygen are unknown. Scallops were exposed to control conditions (treatment C: 22 °C, ∼7.1 mg O2 L−1 or PO2 156.9 mmHg), acute hyperthermia under normoxia (treatment T: 30 °C, ∼6.0 mg O2 L−1 or PO2 150.9 mmHg) or acute hyperthermia plus hypoxia (treatment TH: 30 °C, ∼2.5 mg O2 L−1 or PO2 62.5 mmHg) for 18 h. In T, juveniles exhibited an enhanced oxygen consumption, together with a decrease in adenylate energy charge (AEC) and arginine phosphate (ArgP), and with no changes in metabolic enzyme activity in the muscle. In TH, scallops maintained similar AEC and ArgP levels in muscle as those observed in T treatment. This response occurred along with the accumulation of inosine monophosphate and hypoxanthine. Besides, reduced citrate synthase and pyruvate kinase activities, enhanced hexokinase activity, and a higher octopine dehydrogenase/lactate dehydrogenase ratio in the mantle indicated the onset of anaerobiosis in TH. These responses indicate that juvenile scallops showed tissue-specific compensatory responses regarding their energy balance under moderate hypoxia at high temperatures. Our results give an insight into the tolerance limit of this species to combined hyperthermia and hypoxia in its northern limit of distribution.
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•Oxygen consumption increases at high temperatures, a response affected by hypoxia.•Adenylate energy charge decreases, buffered by phosphagen hydrolysis and adenylate kinase.•Tissue-specific responses of metabolic enzyme activity under hyperthermia and hypoxia.
Although Litopenaeus vannamei is a widely studied species, the information on how the organisms respond to natural daily variations of environmental conditions such as temperature and dissolved ...oxygen, and how such conditions alter the physiological responses, is scarce. In the present work, the strategies used by shrimps to cope with temperature and dissolved oxygen fluctuations during 24 days were investigated through the evaluation of oxygen consumption and heat shock proteins (HSP) gene expression. During daily fluctuations, no change in oxygen consumption in the short-term, but a significant increase in the long-term during hyperthermia conditions was registered, whereas a significant decrease during hypoxia was observed during all the bioassay. On the other hand, HSP70 and HSP90 gene expression increased in gills under thermal stress but was down-regulated under hypoxia, in both the short- and the long-term. This study highlights that to counteract environmental variations of temperature and dissolved oxygen, the shrimps use molecular compensatory mechanisms (HSP gene expression) that are different to those used under constant hypoxic conditions, suggesting that hypoxia can compromise physiological cytoprotection.
•Shrimp's oxygen consumption responses to cyclic hyperthermia and hypoxia are different between short and long-term exposure.•Under oscillating conditions, HSP gene expression in gills is compromised during hypoxia.•Oxygen consumption and HSP gene expression responses during cyclic conditions are different from those at constant hypoxia.
Many molecular and physiological responses to hypoxia are controlled by the transcription factor called hypoxia inducible factor 1 (HIF-1). Metabolic responses are particularly important for marine ...crustaceans that suffer hypoxia in their aquatic environment, including shrimp. HIF-1 is a heterodimer recently described in shrimp and composed by α and β subunits. In the present study, we investigated the effect of silencing HIF-1 using dsRNA in the response to hypoxia in the shrimp
Litopenaeus vannamei in vivo. Intramuscular injection of dsRNA for α and β separately, decreased the concentration of the corresponding transcripts in gills from shrimp maintained in normoxia, while no effect was detected in muscle. In contrasts, during hypoxia, silencing of HIF-1α or HIF-1β, did affect the corresponding transcripts. Moreover, silencing of the α and β subunits of HIF-1 affected the concentrations of glucose and lactate in hemolymph and gills from shrimp exposed to hypoxic conditions, giving insights of the action of HIF-1 in these responses.
We studied the effects of chronic exposure to metals on energy reserves and reproduction in the clam Megapitaria squalida in two nearby populations exposed to different levels of pollution from ...mining operations in the Gulf of California, Mexico. Female M. squalida from San Lucas beach had good reproductive health status, whereas Santa Rosalia specimens consistently showed low energy reserves, massive oocyte resorption throughout the year, high frequencies of undifferentiated individuals, low proportions of ripe and spawning organisms, smaller and fewer oocytes per follicle, and significantly lower follicular areas. Ovarian levels of Co, Cu, Pb, Mn, and Zn were consistently higher in clams from Santa Rosalia. The poor reproductive health of clams inhabiting this site may be attributed to their long-term exposure to high Co, Cu, and Pb concentrations, as these have been shown to cause toxicity and reproductive impairments in other marine organisms.
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•Female M. squalida from two nearby, metal-polluted sites showed contrasting reproductive health status.•Clams from San Lucas beach showed a good reproductive health status.•Clams from Santa Rosalia had lower energy reserves and impaired reproduction.•These negative effects may be attributed to long-term exposure to Co, Cu, and Pb.
Abstract
The thermal responses and tolerance of organisms can be influenced by synergistic interactions with other environmental stresses. Although the heat sensitivity of the whiteleg shrimp ...(Penaeus vannamei Boone, 1931 = Litopenaeus vannamei) has been extensively researched, little is known about how hypoxia impacts the thermal tolerance of the species. We assessed the thermotolerance of P. vannamei postlarvae under combined hyperthermia and hypoxia conditions. Simultaneous hypoxia significantly decreased the thermotolerance (LT50) of the postlarvae at temperatures close to the upper thermal limit of the species.
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