Ca2+/Calmodulin-NOS/NO-TNFs Pathway Hallmarks the Inflammation Response of Oyster During Aerial Exposure

Aerial exposure (emersion) due to the periodical ebb and flow of tides is a major stressor for intertidal organisms and a key environmental factor in shaping their local communities. Oysters are among the most emersion-tolerant mollusk species and can survive for several days under aerial exposure. Noticeably, overwhelming inflammation responses could occur during the emersion stress. However, mechanisms beneath the activation and modulation of emersion-induced inflammation response have remained largely unknown. Ca2+ is an important intracellular second messenger that plays indispensable roles in inflammation response by cooperation with calmodulin (CaM) genes. Here, we showed that intracellular Ca2+ accumulates rapidly in oyster hemocytes during emersion stress along with the changes in the protein levels of three CaM genes, which function as intracellular sensors of Ca2+. As downstream effector of Ca2+/CaM complex, nitric oxide synthase (NOS) activity in hemocytes was enhanced during the emersion stress, facilitating a greater production of nitrite oxide (NO). Augmentation of NO concentration was associated with the increased mRNA expression levels of two oyster cytokines (CgTNFs) during aerial exposure. The robust accumulation of cytokines and severe injury of tissues in oysters have been regarded as potential cause and marker of their death in prolonged emersion stress. Here, both the expression levels of CgTNFs and the tissue injuries of oysters were attenuated when Ca2+/CaM complex or NOS activity were repressed in vivo during the emersion stress. These findings indicate that Ca2+/CaM-NOS/NO-CgTNFs pathway is critically involved in the emersion-induced inflammation response in oysters and plays a role in the resistance against long-term aerial exposure.

Southern king crab larval survival: from intra- and interfemale variations to a fishery-induced mortality

The southern king crab (Lithodes santolla) supports one of the most important fisheries in southern South America. Lecithotrophic larvae hatch over an extended period, in which brooding females can be fished, but must be discarded due to regulations. Larval mortality by female fishing was evaluated. Samples of newly hatched zoeae I were obtained the day before (control) and after female treatment (aerial exposure or aerial exposure + free fall). Independently of the mothers’ treatment, larvae survived less than those from the control, explained by the air-exposure effects. The intraclutch variability in larval survival and their variability in energetic reserves were studied. Females were maintained during the hatching period, and zoea I samples were taken during 3 successive days. We found high variation in larval survival within a single egg clutch and between different females, only ascribable to the initial larval glycogen content. The intraclutch variability in larval survival combined with extended hatching may be an adaptation that allows mothers to find an adequate substrate as larvae hatch and may constitute a diversified bet-hedging strategy.

Metabolomics analysis of annual killifish (Austrofundulus limnaeus) embryos during aerial dehydration stress

The annual killifish, Austrofundulus limnaeus, survives in ephemeral ponds in the coastal deserts of Venezuela. Persistence through the dry season is dependent on drought-resistant eggs embedded in the pond sediments during the rainy season. The ability of these embryos to enter drastic metabolic dormancy (diapause) during normal development enables A. limnaeus to survive conditions lethal to most other aquatic vertebrates; critical to the survival of the species is the ability of embryos to survive months and perhaps years without access to liquid water. Little is known about the molecular mechanisms that aid in survival of the dry season. This study aims to gain insight into the mechanisms facilitating survival of dehydration stress due to aerial exposure by examining metabolite profiles of dormant and developing embryos. There is strong evidence for unique metabolic profiles based on developmental stage and length of aerial exposure. Actively developing embryos exhibit more robust changes; however, dormant embryos respond in an active manner and significantly alter their metabolic profile. A number of metabolites accumulate in aerial-exposed embryos that may play an important role in survival, including the identification of known antioxidants and neuroprotectants. In addition, a number of unique metabolites not yet discussed in the dehydration literature are identified, such as lanthionine and 2-hydroxyglutarate. Despite high oxygen availability, embryos accumulate the anaerobic end product lactate. This paper offers an overview of the metabolic changes occurring that may support embryonic survival during dehydration stress due to aerial incubation, which can be functionally tested using genetic and pharmacological approaches.

Polyp bailout and reattachment of the abundant Caribbean octocoral Eunicea flexuosa

Anthozoans exhibit great plasticity in their responses to stressful conditions, including decreasing individual size, detaching from the substratum and relocating, and releasing endosymbiotic microalgae. Another response to stress used by some colonial anthozoans is polyp bailout, in which the coenenchyme breaks down and individual polyps detach from the colony. We observed polyp bailout in the common Caribbean gorgonian Eunicea flexuosa after eight hours of aerial exposure. After nine days, 28% of bailed-out polyps reattached, although none opened to resume feeding. Polyp bailout is a costly and high-risk escape response, but reattachment indicates that this can be a genet-saving behavior in cases where whole-colony mortality is likely. While it has been described in several species of scleractinians and two octocorals, we still do not know how widespread this behavior is in anthozoans.