Nestmate Recognition and Cuticular Hydrocarbon Profiles in the Ant Formica argentea

Nestmate recognition, the ability to recognize a nestmate from a non-nestmate, is critical to the ecological success of eusocial insects. Although cuticular hydrocarbons are thought to serve as cues in nestmate recognition, little is known about how specific hydrocarbons vary between colonies and which ones are responsible for evoking nestmate recognition behaviors. The aim of my study was, using the ant Formica argentea, to investigate cuticular hydrocarbons in great detail by addressing the following questions: (1) What cuticular hydrocarbons are present? (2) Can any one group of compounds statistically classify workers by nest? (3) Which structural classes of hydrocarbons evoke a nestmate recognition response? (4) Do increased differences in cuticular hydrocarbon profiles predict aggression? (5) How do different structural classes of hydrocarbons change with time? After chemical analyses I found that the cuticular hydrocarbon profile of F. argentea workers contain a mixture of n-alkanes, alkenes, and methylalkanes which stay fairly constant within a nest but vary in relative proportion between nests. Additionally, using the only the C29 methyl-alkanes in a hierarchical cluster analysis was enough to correctly classify workers by nest. Behavioral experiments demonstrated that both methylalkanes and alkenes increased aggression in workers while n-alkanes did not. Differences in cuticular hydrocarbon profiles between pairs were a good predictor of aggression with differences between particular methyl-alkanes weighing more heavily on the statistical analysis. When kept in a uniform environment the average relative proportions n-alkanes, alkenes, and methyl-alkanes, varied with time, while the relative proportion of the C29 methyl-alkanes remained constant. These finding indicate that all structural classes of cuticular hydrocarbons should not be grouped together or treated equally in nestmate recognition analyses. This study improves our understanding of nestmate recognition and cuticular hydrocarbon profiles in eusocial insects

Vector competence of Aedes aegypti, Culex tarsalis, and Culex quinquefasciatus from California for Zika virus.

Zika virus (ZIKV) has emerged since 2013 as a significant global human health threat following outbreaks in the Pacific Islands and rapid spread throughout South and Central America. Severe congenital and neurological sequelae have been linked to ZIKV infections. Assessing the ability of common mosquito species to transmit ZIKV and characterizing variation in mosquito transmission of different ZIKV strains is important for estimating regional outbreak potential and for prioritizing local mosquito control strategies for Aedes and Culex species. In this study, we evaluated the laboratory vector competence of Aedes aegypti, Culex quinquefasciatus, and Culex tarsalis that originated in areas of California where ZIKV cases in travelers since 2015 were frequent. We compared infection, dissemination, and transmission rates by measuring ZIKV RNA levels in cohorts of mosquitoes that ingested blood meals from type I interferon-deficient mice infected with either a Puerto Rican ZIKV strain from 2015 (PR15), a Brazilian ZIKV strain from 2015 (BR15), or an ancestral Asian-lineage Malaysian ZIKV strain from 1966 (MA66). With PR15, Cx. quinquefasciatus was refractory to infection (0%, N = 42) and Cx. tarsalis was infected at 4% (N = 46). No ZIKV RNA was detected in saliva from either Culex species 14 or 21 days post feeding (dpf). In contrast, Ae. aegypti developed infection rates of 85% (PR15; N = 46), 90% (BR15; N = 20), and 81% (MA66; N = 85) 14 or 15 dpf. Although MA66-infected Ae. aegypti showed higher levels of ZIKV RNA in mosquito bodies and legs, transmission rates were not significantly different across virus strains (P = 0.13, Fisher's exact test). To confirm infectivity and measure the transmitted ZIKV dose, we enumerated infectious ZIKV in Ae. aegypti saliva using Vero cell plaque assays. The expectorated plaque forming units PFU varied by viral strain: MA66-infected expectorated 13±4 PFU (mean±SE, N = 13) compared to 29±6 PFU for PR15-infected (N = 13) and 35±8 PFU for BR15-infected (N = 6; ANOVA, df = 2, F = 3.8, P = 0.035). These laboratory vector competence results support an emerging consensus that Cx. tarsalis and Cx. quinquefasciatus are not vectors of ZIKV. These results also indicate that Ae. aegypti from California are efficient laboratory vectors of ancestral and contemporary Asian lineage ZIKV

Cleptobiosis in Social Insects

In this review of cleptobiosis, we not only focus on social insects, but also consider broader issues and concepts relating to the theft of food among animals. Cleptobiosis occurs when members of a species steal food, or sometimes nesting materials or other items of value, either from members of the same or a different species. This simple definition is not universally used, and there is some terminological confusion among cleptobiosis, cleptoparasitism, brood parasitism, and inquilinism. We first discuss the definitions of these terms and the confusion that arises from varying usage of the words. We consider that cleptobiosis usually is derived evolutionarily from established foraging behaviors. Cleptobionts can succeed by deception or by force, and we review the literature on cleptobiosis by deception or force in social insects. We focus on the best known examples of cleptobiosis, the ectatommine ant Ectatomma ruidum, the harvester ant Messor capitatus, and the stingless bee Lestrimellita limão. Cleptobiosis is facilitated either by deception or physical force, and we discuss both mechanisms. Part of this discussion is an analysis of the ecological implications (competition by interference) and the evolutionary effects of cleptobiosis. We conclude with a comment on how cleptobiosis can increase the risk of disease or parasite spread among colonies of social insects

Exposure to Deepwater Horizon Oil and Corexit 9500 at Low Concentrations Induces Transcriptional Changes and Alters Immune Transcriptional Pathways In Sheepshead Minnows

The 2010 Deepwater Horizon (DWH) oil spill caused the release of 4.9 million barrels of crude oil into the Gulf of Mexico, followed by the application of 2.9 million L of the dispersant, Corexit™ to mitigate the spread of oil. The spill resulted in substantial shoreline oiling, potentially exposing coastal organisms to polyaromatic hydrocarbon (PAH) and dispersant contaminants. To investigate molecular effects in fish following exposure to environmentally relevant concentrations of DWH oil and dispersants, we exposed adult sheepshead minnows (Cyprinodon variegatus) to two concentrations of high-energy water-accommodated fraction (HEWAF), chemically enhanced water-accommodated fraction (CEWAF) or Corexit 9500™ for 7 and 14 days. Resulting changes in hepatic gene expression were measured using 8 × 15 K microarrays. Analytical chemistry confirmed PAH concentrations in HEWAF and CEWAF treatments were low (ranging from 0.26 to 5.98 μg/L), and likely representative of post-spill environmental concentrations. We observed significant changes to gene expression in all treatments (relative to controls), with Corexit and CEWAF having a greater effect on expression patterns in the liver than HEWAF treatments. Sub-network enrichment analysis of biological pathways revealed that the greatest number of altered pathways in high dose HEWAF and CEWAF treatments occurred following a 7-day exposure. Pathways related to immunity comprised the majority of pathways affected in each treatment, followed by pathways related to blood and circulation processes. Our results indicate that oil composition, concentration, and exposure duration all affect molecular responses in exposed fish, and suggest that low-concentration exposures may result in sub-lethal adverse effects

Responses of Juvenile Southern Flounder Exposed to Deepwater Horizon Oil-Contaminated Sediments

The Deepwater Horizon oil spill released millions of barrels of crude oil into the northern Gulf of Mexico, much of which remains associated with sediments and can have continuing impacts on biota. Juvenile southern flounder (Paralichthys lethostigma) were exposed for 28 d in the laboratory under controlled conditions to reference and Deepwater Horizon oil-contaminated sediments collected from coastal Louisiana to assess the impacts on an ecologically and commercially important benthic fish. The measured polycyclic aromatic hydrocarbon (PAH) concentrations in the sediments ranged from 0.25 mg/kg to 3940 mg/kg suite of 50 PAH analytes (tPAH50). Mortality increased with both concentration and duration of exposure. Exposed flounder length and weight was lower compared to controls after 28 d of exposure to the sediments with the highest PAH concentration, but condition factor was significantly higher in these fish compared with all other treatments. Histopathological analyses showed increased occurrence of gill abnormalities, including telangiectasis, epithelial proliferation, and fused lamellae in flounder exposed to sediments with the highest tPAH50 concentrations. In addition, hepatic vascular congestion and macrovesicular vacuolation were observed in flounder exposed to the more contaminated sediments. These data suggest that chronic exposure to field collected oil-contaminated sediments results in a variety of sublethal impacts to a benthic fish, with implications for long-term recovery from oil spills. Environ Toxicol Chem 2017;36:1067–1076. © 2016 SETA

A Multiple Endpoint Analysis of the Effects of Chronic Exposure to Sediment Contaminated with Deepwater Horizon Oil On Juvenile Southern Flounder and Their Associated Microbiomes

Exposure to oiled sediments can negatively impact the health of fish species. Here, we examine the effects of chronic exposure of juvenile southern flounder, Paralichthys lethostigma, to a sediment-oil mixture. Oil:sediment mixtures are persistent over time and can become bioavailable following sediment perturbation or resuspension. Juvenile flounder were exposed for 32 days under controlled laboratory conditions to five concentrations of naturally weathered Macondo MC252 oil mixed into uncontaminated, field-collected sediments. The percent composition of individual polycyclic aromatic hydrocarbons (PAHs) of the weathered oil did not change after mixing with the sediment. Spiked exposure sediments contained 0.04–395 mg/kg tPAH50 (sum of 50 individual PAH concentration measurements). Mortality increased with both exposure duration and concentration of sediment-associated PAHs, and flounder exposed to concentrations above 8 mg/kg tPAH50 showed significantly reduced growth over the course of the experiment. Evident histopathologic changes were observed in liver and gill tissues of fish exposed to more than 8 mg/kg tPAH50. All fish at these concentrations showed hepatic intravascular congestion, macrovesicular hepatic vacoulation, telangiectasia of secondary lamellae, and lamellar epithelial proliferation in gill tissues. Dose-dependent upregulation of Cyp1a expression in liver tissues was observed. Taxonomic analysis of gill and intestinal commensal bacterial assemblages showed that exposure to oiled sediments led to distinct shifts in commensal bacterial population structures. These data show that chronic exposure to environmentally-relevant concentrations of oiled sediments produces adverse effects in flounder at multiple biological levels

ZIKV infection, dissemination, and transmission rates in California <i>Aedes</i> and <i>Culex</i> mosquitoes 14 and 21 days post ingestion of blood from viremic mice.

<p>ZIKV infection, dissemination, and transmission rates in California <i>Aedes</i> and <i>Culex</i> mosquitoes 14 and 21 days post ingestion of blood from viremic mice.</p

Crude oil impairs immune function and increases susceptibility to pathogenic bacteria in southern flounder - Fig 1

<p><b>(A) Evidence of bloody lesions seen in flounder exposed to oil.</b> Red arrows indicate observed lesions. Fish were not tagged; therefore, lesions were not enumerated. <b>(B) Survival rates in exposure treatments on Day 2 post-exposure to pathogenic bacteria <i>Vibrio anguillarum</i></b>. Bars represent average survival for three tanks per treatment and error bars represent standard error.</p

Effect of oil exposure on bacterial diversity and function.

<p><b>(A)</b> Principal Coordinates Analysis (PCoA) plot of data at the Order level from fish collected on Day 1 post-pathogen exposure calculated with a Bray-Curtis dissimilarity in R (v. 3.0.2 [2013-09-25]–“Frisbee Sailing”). Water and sediment samples were collected on Day 0 of the experiment. Lower case letters indicate locations of various bacterial orders (a-<i>Vibrio</i>, b-<i>Alcanivorax</i> sp, c-<i>Vibrio</i>, d<i>Roseobacter</i>, e-<i>Thalassolitus</i>, f-<i>Oceanobacter kriegii</i>, g-<i>Alcanivorax</i> sp, h-<i>Halolactibacillus miurensis</i>, i-<i>Cytophaga fermentans</i>, j-<i>Oceanobacter kriegii</i>). Symbols represent different tissue types (● Intestine, ▲Lower Gill, ■ Upper Gill). Ellipses represent non-oil exposed vs. oilexposed each defined by treatment labels in their centers and indicate 95% Confidence Intervals, with orange ellipses representing both oiled treatments and gray ellipses representing both nonoiled treatments. <b>(B)</b> Predictive metagenomics analysis of the intestinal bacterial taxa in Oil/Pathogen Challenged fish (compared with control fish) indicated enrichment in degradation pathways. Pathway abundance was normalized via log₂ fold change.</p

Infecting (bodies), disseminating (legs+wings) and transmitted (saliva) ZIKV RNA levels 14 or 15 days after <i>Ae</i>. <i>aegypti</i> orally ingested one of three Asian lineage ZIKV strains.

<p>Each dot represents the mean log₁₀ ZIKV genome copies per tissue or saliva sample from an individual <i>Ae</i>. <i>aegypti</i>. <i>Ae</i>. <i>aegypti</i> from Los Angeles, California, USA, were fed on viremic mice infected with ZIKV from Malaysia 1966 (MA66), Puerto Rico 2015 (PR15) or Brazil 2015 (BR15). Mosquitoes exposed to BR15 were assayed 15 dpf, MA66 and PR15 cohorts were assayed 14 dpf. Each dot represents the mean of two or more RT-qPCR technical replicates. The dashed lines represent the limits of detection (LOD). Dots below dashed line represent tested samples with an undetectable Ct or a Ct value of >38. The LOD for saliva was lower than for tissues because RNA was extracted from a higher proportion of the saliva sample volume. Asterisks show significant differences in means across groups of the same tissue type, <i>P</i><0.01, ANOVA, Tukey post-hoc test. No asterisk indicates no significant difference across groups.</p