Metagenome-assembled genome of withering syndrome causative agent, "Candidatus Xenohaliotis californiensis," from endangered white abalone (Haliotis sorenseni).

The genome of "Candidatus Xenohaliotis californiensis" was assembled from shotgun metagenomic sequencing of experimentally infected white abalone. Ninety-one percent genome completeness was achieved with low contamination. Sequencing this genome provides the opportunity to track pathogen evolution over time, conduct gene expression experiments, and study dynamics between this pathogen and its phage.

Abalone under moderate heat stress have elevated metabolic rates and changes to digestive enzyme activities.

Abalone around the world are subject to increasing frequency of marine heatwaves, yet we have a limited understanding of how acute high temperature events impact the physiology of these commercially and ecologically important species. This study examines the impact of a 5 °C temperature increase over ambient conditions for six weeks on the metabolic rates, digestive enzyme activities in the digestive gland, and digestive efficiency of Red Abalone (Haliotis rufescens) and Paua (H. iris) on their natural diets. We test the hypothesis that abalone digestive function can keep pace with this increased metabolic demand in two separate experiments, one for each species. H. iris had higher food intake in the heat treatment. Both species had higher metabolic rates in the heat treatment with Q10 = 1.73 and Q10 = 2.46 for H. rufescens and H. iris, respectively. Apparent organic matter digestibility, protein digestibility, and carbohydrate digestibility did not differ between the heat treatment and the ambient (control) treatment in either experiment. H. rufescens exhibited higher maltase, alanine-aminopeptidase, and leucine-aminopeptidase activities in the heat treatment. Amylase, ß-glucosidase, trypsin, and alkaline phosphatase activities in the digestive gland tissue did not differ between temperature treatments. H. iris exhibited lower amylase and ß-glucosidase activities in the heat treatment, while maltase, trypsin, leucine-aminopeptidase, and alkaline phosphatase activities did not differ between treatments. We conclude that over six weeks of moderate heat stress both abalone species were able to maintain digestive function, but achieved this maintenance in species-specific ways.

Withering syndrome induced gene expression changes and a de-novo transcriptome for the Pinto abalone, Haliotis kamtschatkana.

In the abalone and Candidatus Xenohaliotis californiensis (Ca. Xc) system, the Ca. Xc bacterium infects abalone digestive tissues and leads to extreme starvation and a characteristic "withering" of the gastropod foot. First identified in black abalone in California after an El Niño event, withering syndrome (WS) has caused large declines in wild black and captive white abalone on the northeastern Pacific coast, but disease resistance levels are species-, and possibly population-specific. This study compared gene expression patterns in the digestive gland of Ca. Xc-exposed and unexposed (control) Pinto abalone (Haliotis kamtschatkana), a particularly susceptible species. Lab-induced Ca. Xc infections were followed over 7 months and RNAseq was used to identify differential gene expression. Exposed Pinto abalone showed distinct changes in expression of 68 genes at 3 and 7 months post-infection relative to those in control animals. Upregulation of an orexin-like receptor (which is involved in feeding signaling) and a zinc peptidase-like region (many amino peptidases are zinc peptidases) in animals infected for 7 months indicates that animals with Ca. Xc infection may be starving and upregulating processes associated with feeding and digestion. Other groups of differentially expressed genes (DEGs) were upregulated or downregulated across control and exposed individuals over the 7-month experiment, including DEG groups that likely correspond to early disease state and to general stress response of being held in captivity. No patterns emerged in genes known to be involved in molluscan immune response, despite this being an expectation during a 7-month infection; digestion-related genes and unannotated DEGs were identified as targets for future research on potential immune response to WS in abalone.

The beach-spawning California grunion Leuresthes tenuis eats and digests conspecific eggs.

Apparent egg cannibalism was investigated in the beach-spawning California grunion Leuresthes tenuis. Three hypotheses were tested to determine whether L. tenuis regularly consumes and efficiently digests conspecific eggs. First, examination of the gut contents of adults collected at four spawning sites over two seasons showed that the intestines of most fish from all the sites (57-87%, n ≥ 30, each site) contained L. tenuis eggs. The two other hypotheses focused on digestion of the eggs. First, the force required to crush cannibalized eggs was significantly less than that for uncannibalized eggs (fertilized or unfertilized), indicating that ingestion weakens the egg chorions. Second, conspecific eggs fed to fish held in the laboratory visibly degraded as they passed through the gut. The eggs lost c. half of their protein content and about two-thirds of their lipid content as they passed from proximal to distal regions of the gut, indicating that digestion occurred. Digestive enzyme activities of the gut further confirmed that L. tenuis can break down the contents of ingested eggs. Trypsin activity decreased and aminopeptidase activity increased posteriorly along the gut, whereas amylase and lipase activities exhibited less clear patterns by gut region. As far as is known, this study is the first to show that L. tenuis is an egg cannibal.

Individual differences in combat experiences and error-related brain activity in OEF/OIF/OND veterans.

Increased error-related negativity (ERN) has been implicated in the pathophysiology of multiple forms of psychopathology. Although there is increasing evidence that the ERN can be shaped by environment and experience, no studies to date have examined this question in a clinical sample. In the current study, we examined the influence of combat exposure on the ERN using electroencephalogram (EEG) in a sample of military veterans with a high prevalence of psychopathology. Participants included sixty-seven U.S. military veterans from Operations Enduring Freedom, Iraqi Freedom, and New Dawn (OEF/OIF/OND). The degree of combat exposure was assessed using the Deployment Risk and Resilience Inventory-2 (DRRI-2) and Combat Exposure Scale (CES). A well-validated flanker task was used to elicit the ERN during continuous EEG recording. Results revealed that veterans who reported experiencing greater combat exposure exhibited a more enhanced ERN, even when adjusting for broad anxiety and posttraumatic stress disorder (PTSD) symptoms. The association between combat exposure and ERN was not moderated by PTSD symptom severity. The current study demonstrates that greater combat exposure is associated with a more enhanced ERN among OEF/OIF/OND veterans. This enhanced ERN may be one mechanism that places veterans at greater risk for developing psychiatric disorders following exposure to combat. Future longitudinal studies are needed to directly test whether the ERN mediates the relation between level of combat exposure and the development of internalizing disorders.

Impact of posttraumatic stress symptom dimensions on amygdala reactivity to emotional faces.

Posttraumatic stress disorder (PTSD) is highly prevalent and associated with impairment, even at the subthreshold level. It is therefore important to identify biological processes that contribute to the pathophysiology of posttraumatic stress symptoms (PTSS). Although neuroimaging research has highlighted the importance of heightened amygdala reactivity to aversive stimuli in PTSS, not all studies have yielded evidence of this relationship. Given that PTSS is comprised of four, factor analytically distinct dimensions of symptoms - re-experiencing, avoidance, hyperarousal, and negative cognitions and mood - it is possible that heightened amygdala reactivity to aversive stimuli is specific to certain PTSS clusters. In a sample of 45 trauma-exposed individuals, the present study therefore examined how specific PTSS clusters relate to amygdala responding during functional magnetic resonance imaging (fMRI) to both negative and positive emotional faces during a well-validated social-emotional task, the Emotional Face Assessment Task (EFAT). Results indicated that hyperarousal symptoms were positively associated with left amygdala reactivity across all emotional face conditions. There was no interaction of hyperarousal by condition (i.e., fearful, sad, angry, or happy faces), and other PTSS clusters were not associated with amygdala reactivity. These results indicate that the hyperarousal cluster of PTSS may have a unique relationship with amygdala reactivity to socioemotional information. The results also corroborate a growing literature suggesting that trauma-exposed individuals characterized by high PTSS hyperarousal symptoms may display exaggerated psychophysiological reactivity to appetitive and aversive stimuli.