Changes in the Gut Microbiome of the Sea Lamprey during Metamorphosis

Vertebrate metamorphosis is often marked by dramatic morphological and physiological changes of the alimentary tract, along with major shifts in diet following development from larva to adult. Little is known about how these developmental changes impact the gut microbiome of the host organism. The metamorphosis of the sea lamprey (Petromyzon marinus) from a sedentary filter-feeding larva to a free-swimming sanguivorous parasite is characterized by major physiological and morphological changes to all organ systems. The transformation of the alimentary canal includes closure of the larval esophagus and the physical isolation of the pharynx from the remainder of the gut, which results in a nonfeeding period that can last up to 8 months. To determine how the gut microbiome is affected by metamorphosis, the microbial communities of feeding and nonfeeding larval and parasitic sea lamprey were surveyed using both culture-dependent and -independent methods. Our results show that the gut of the filter-feeding larva contains a greater diversity of bacteria than that of the blood-feeding parasite, with the parasite gut being dominated by Aeromonas and, to a lesser extent, Citrobacter and Shewanella. Phylogenetic analysis of the culturable Aeromonas from both the larval and parasitic gut revealed that at least five distinct species were represented. Phenotypic characterization of these isolates revealed that over half were capable of sheep red blood cell hemolysis, but all were capable of trout red blood cell hemolysis. This suggests that the enrichment of Aeromonas that accompanies metamorphosis is likely related to the sanguivorous lifestyle of the parasitic sea lamprey.     

Susceptibility of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) adults to fungicides used to control apple diseases

This study evaluated the susceptibility under laboratory conditions of Trichogrammapretiosum Riley adults to fungicides recommended by the Integrated Production of Apple (IPA). The bioassays were carried out using the International Organization for Biological Control (IOBC), West Palearctic Regional Section (WPRS) standard protocols. Twelve selected fungicides were studied in the doses (g or ml active ingredient/100 L) captan 1 (0.115), captan 2 (0.120), kresoxim-methyl (0.010), sulphur 1 (AG) (0.480), sulphur 2 (0.480), folpet (0.105), mancozeb (0.160), pyraclostrobin (0.010), tebuconazole (0.010), tetraconazole (0.005), thiophanate-methyl (0.050) and triforine (0.024). Distilled water was used as the blank treatment and the insecticide triclorfon (0.150) as a positive control. The parasitoids were exposed to dry residues applied on glass plates. The reduction in the capacity of parasitism was used to measure the effect of the chemical in comparison to the blank treatment. Each treatment was replicated four times. The results allowed us to classify the fungicides tested in four categories: 1, harmless (< 30%); 2, slightly harmful (30-79%); 3, moderately harmful (80-99%); and 4, harmful (> 99%). 75% of the tested substances were classified as selective (classes 1 and 2) to the parasitoid. The fungicides captan 1, captan 2, kresoxim-methyl, folpet, pyraclostrobin, tebuconazole, thiophanate-methyl and triforine were harmless; mancozeb was slightly harmful; sulphur 1 (AG) and tetraconazole were moderately harmful and sulphur 2 was harmful. These findings should be taken into account when selecting fungicides to spray apple orchards against fungi diseases to preserve the egg parasitoid T. pretiosum.     

Analysis of lamprey and hagfish genes reveals a complex history of gene duplications during early vertebrate evolution

It has been proposed that two events of duplication of the entire genome occurred early in vertebrate history (2R hypothesis). Several phylogenetic studies with a few gene families (mostly Hox genes and proteins from the MHC) have tried to confirm these polyploidization events. However, data from a single locus cannot explain the evolutionary history of a complete genome. To study this 2R hypothesis, we have taken advantage of the phylogenetic position of the lamprey to study the history of gene duplications in vertebrates. We selected most gene families that contain several paralogous genes in vertebrates and for which lamprey genes and an out-group are known in databases. In addition, we isolated members of the nuclear receptor superfamily in lamprey. Hagfish genes were also analyzed and found to confirm the lamprey gene analysis. Consistent with the 2R hypothesis, the phylogenetic analysis of 33 selected gene families, dispersed through the whole genome, revealed that one period of gene duplication arose before the lamprey-gnathostome split and this was followed by a second period of gene duplication after the lamprey-gnathostome split. Nevertheless, our analysis suggests that numerous gene losses and other gene-genome duplications occurred during the evolution of the vertebrate genomes. Thus, the complexity of all the paralogy groups present in vertebrates should be explained by the contribution of genome duplications (2R hypothesis), extra gene duplications, and gene losses.     

Modifying effects of a cobble substrate on thermal environments and implications for embryonic development in lake whitefish (Coregonus clupeaformis)

A laboratory flume was constructed to examine substrate effects on aquatic development. The flume was designed as a once-through system with a submerged cobble-filled corebox. Lake whitefish (Coregonus clupeaformis) embryos and temperature probes were deployed at multiple sites within the cobble and in the open water channel. Embryos were incubated in the flume for two different experimental periods: one to examine substrate impacts during natural lake cooling (37 days: 5 December 2016 to 10 January 2017) and the second to investigate substrate effects while administering a twice weekly 1 h heat shock (51 days: 11 January to 2 March 2017). During incubation, no significant difference was found in the average temperature between locations; however, temperatures were more stable within the cobble. Following both incubation periods, embryos retrieved from the cobble were significantly smaller in both dry mass and body length by up to 20%. These results demonstrate differences between embryos submerged in a cobble substrate and in the open water column, highlighting the need to consider the physical influences from the incubation environment when assessing development effects as part of any scientific study or environmental assessment.     

Glucose infusion partially attenuates glucose production and increases uptake during intense exercise

Glucose infusioncan prevent the increase in glucose production (R_a) andincrease glucose uptake (R_d) during exercise of moderate intensity. We postulated that 1)because in postabsorptive intense exercise (>80% maximalO₂ uptake) the eightfold increasein R_a may be mediated by catecholamines rather than byglucagon and insulin, exogenous glucose infusion would not prevent theR_a increment, and 2)such infusion would cause greater R_d. Fit young men were exercised at >85% maximal O₂uptake for 14 min in the postabsorptive state [controls (Con),n = 12] or atminute 210 of a 285-min glucose infusion. In seven subjects, the infusion was constant(CI; 4 mg · kg¹ · min¹),and in seven subjects it was varied (VI) to mimic the exercise R_a response in Con. Although glucose suppressedR_a to zero (with glycemia ~6 mM and insulin ~150 pM),an endogenous R_a response to exercise occurred, to peakincrements two-thirds those in Con, in both CI and VI. Glucagon wasunchanged, and very small increases in the glucagon-to-insulin ratiooccurred in all three groups. Catecholamine responses were similar inall three groups, and correlation coefficients of R_a withplasma norepinephrine and epinephrine were significant in all. In allCI and VI, R_d at rest was 2× Con, increased earlierin exercise, and was higher for the 1 h of recovery with glucoseinfusion. Thus the R_a response was only partly attenuated,and the catecholamines are likely to be the regulators. This suggeststhat an acute endogenous R_a rise is possible even in thepostprandial state. Furthermore, the fact that more circulating glucoseis used by muscle during exercise and early recovery suggests thatmuscle glycogen is spared.

     

Effect of alloxan and insulin immunoneutralization on circulating thyroid hormone levels in larval landlocked sea lampreys,petromyzon marinus

The effects of alloxan, an insulin (INS)-secreting cell toxin, and INS immunoneutralization on circulating levels of thyroid hormones (thyroxine, T(4); triiodothyronine, T(3)) were examined in larval landlocked sea lampreys, Petromyzon marinus. Animals were injected intraperitoneally with either (Experiment 1) saline (0.6%) or alloxan (20 or 200 microg/g body weight), or with (Experiment 2) normal rabbit serum or anti-lamprey INS. Alloxan (200 microg/g) decreased plasma T(3), but not T(4), in larvae by about 45-80%. Three, six, or nine hr after acute immunoneutralization of lamprey INS with anti-lamprey INS, plasma T(3) levels decreased by 13-30%, relative to controls. These data indicate that INS deficiency can regulate the thyroid system of larval lampreys. There is some suggestion that INS may mediate the metamorphic processes by modulating thyroid hormone concentrations.     

Glucoregulatory responses to intense exercise performed in the postprandial state

A seven- to eightfold increment in hepatic glucose production (endogenous R(a)) occurs in postabsorptive (PA) intense exercise (IE). A similar response is likely present in the postprandial (PP) state, when most such exercise is performed, because 1) little evidence for increased intestinal absorption of glucose during exercise exists, and 2) intravenous glucose does not prevent it. We investigated IE in 10 PA and 8 PP fit, lean, young males who had exercised for 15 min at >84% maximum O(2) uptake, starting 3 h after a 412-kcal mixed meal. The meal induced a small rise in glycemia with sustained insulin and glucagon increases. Preexercise glucose total R(a) and utilization (R(d)) were equal and approximately 130% of the PA level. Exercise hyperglycemia in PP was delayed and diminished and, in early recovery, was of shorter duration and lesser magnitude (P = 0.042). Peak catecholamine (12- to 16-fold increase) and R(a) (PP: 11.5 +/- 1.4, PA: 13.8 +/- 1.4 mg. kg(-1). min(-1)) responses did not differ, and their responses during exercise were significantly correlated. Exercise glucagon, insulin, and glucagon-to-insulin responses were small or not significant. R(d) reached the same peak (PP: 8.0 +/- 0.6, PA: 9.3 +/- 0.8 mg. kg(-1). min(-1)) but was greater at 20-120 min of recovery in PP (P = 0.001). Therefore, the total R(a) response to IE is preserved despite the possibility of prior PP suppression of endogenous R(a) and is consistent with catecholamine mediation. Post-IE hyperglycemia is reduced in the postprandial state.