| 1. |
- Kristoffersen, Lina, et al.
(författare)
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Aglomerular hemipteran antennal lobes – Basic neuroanatomy of a small nose
- 2008
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Ingår i: Chemical Senses. - : Oxford University Press (OUP). - 1464-3553 .- 0379-864X. ; 33, s. 771-778
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Tidskriftsartikel (refereegranskat)abstract
- We have compared the basic organization of the primary olfactory centre, the antennal lobe (AL), in 4 hemipteran species representing the 2 major lineages in this order. The Homoptera were represented by the psyllid Trioza apicalis and its aphid relatives the grain aphid Sitobion avenae Fabricius and the rose-grain aphid Metopolophium dirhodum Walker, whereas the Heteroptera were represented by the pentatomid stink bug Euschistus heros Fabricius. The olfactory systems of psyllids and aphids are generally very small, with low numbers of afferents in comparison to other insect groups, and the smallest described so far belongs to T. apicalis, comprising less than 50 olfactory receptor neurons (ORNs). Originally, we tried to estimate numbers of olfactory glomeruli in the AL of T. apicalis, which in insects generally correspond closely to the number of different types of ORNs. Neither immunocytochemical staining nor anterograde staining of ORNs revealed any glomerular structures in the ALs of T. apicalis or the 2 aphids that were included for comparison. In contrast, the ALs of the pentatomid stink bug E. heros displayed numerous distinct and well-delineated glomeruli, showing that aglomerular ALs are not typical of all insects within the order Hemiptera. Glomeruli are hallmark features of olfactory lobes in many different phyla, and the absence of glomerular structures in psyllids and aphids appears to be unique in insects that depend on olfactory orientation.
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| 2. |
- Kristoffersen, Lina, et al.
(författare)
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Carrot psyllid (Trioza apicalis) winter habitats - insights in shelter plant preference and migratory capacity
- 2007
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Ingår i: Journal of Applied Entomology. - : Wiley. - 0931-2048 .- 1439-0418. ; 131:3, s. 174-178
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Tidskriftsartikel (refereegranskat)abstract
- The carrot psyllid (Trioza apicalis) is a serious pest in carrot-growing areas in northern and parts of central Europe. The psyllids overwinter as adults on conifers and during summer feed and lay eggs on carrot plants (Daucus carota ssp. sativus), thereby destroying the crop. To investigate the migratory capabilities and preferences for different shelter plant species of the carrot psyllid, we made an inventory study of its winter habitats in three carrot-growing regions in southern Sweden. Norway spruce (Picea abies) was the preferred conifer over Scots pine (Pinus sylvestris) and juniper (Juniperus communis). We found psyllids on trees up to 1 km from the carrot fields, which was the largest distance sampled. The regression of catch numbers over distance was non-significant, however all samples containing more than seven psyllids were collected within 250m distance from the fields. There was no obvious pattern between catch directions and the prevailing wind directions of the preceding migratory period. Our study did not show any differences between males and females with respect to migration or shelter species preferences.
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| 3. |
- Kristoffersen, Lina, et al.
(författare)
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Functional characteristics of a tiny but specialized olfactory system: Olfactory receptor neurons of carrot psyllids (Homoptera: Triozidae)
- 2008
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Ingår i: Chemical Senses. - : Oxford University Press (OUP). - 1464-3553 .- 0379-864X. ; 33, s. 759-769
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Tidskriftsartikel (refereegranskat)abstract
- With only approximately 50 olfactory receptor neurons (ORNs), the carrot psyllid Trioza apicalis (Homoptera: Psylloidea) may have the smallest olfactory system described in adult Neopteran insects. Using single sensillum recordings (SSR) and gas chromatograph-linked SSR, we characterized 4 olfactory sensilla forming a distinct morphological type, which together house approximately 25% of all ORNs. We recorded responses to extracts and single constituents from Daucus carota ssp. sativus, from the conifers Picea abies, Pinus sylvestris, and Juniperus communis, as well as from male and female T. apicalis. Receptor neurons were highly selective; only 9 compounds in total elicited repeatable responses, and each neuron responded to at most 3 individual compounds. Chemical profiles of carrot and conifers showed significant overlap, with 4 out of 9 electrophysiologically active compounds occurring in more than one type of extract, but a carrot-specific compound elicited the most repeated responses. We identified 4 tentative neuron classes and found a rather high degree of neuronal redundancy, with 1 neuron class present in 3 and another present in all 4 of the sensilla, respectively.
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| 4. |
- Kristoffersen, Lina
(författare)
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Getting to know Trioza apicalis (Homoptera: Psylloidea) – a Specialist Host-Alternating Insect with a Tiny Olfactory System
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis comprises ecological, morphological and physiological studies of the carrot psyllid Trioza apicalis (Homoptera: Psylloidea) with particular focus on olfaction. Data from inventories of winter habitats suggest that T. apicalis prefer Picea abies over Pinus sylvestris and Juniperus communis as winter hosts. Their migration range is at least I km, and we found no clear wind-borne patterns. No differences with regard to migratory capacity or preferences were noted between the sexes. We investigate behavioural phototaxis effects on host choice and settling behaviour. The results show that carrot psyllids are able to detect and react to minute differences in light intensity. We provide a thorough description of the antennal sensilla, using SEM and TEM, and describe five (possibly seven) plausible types of olfactory sensilla. Several sensillar types located in cuticular cavities are revealed. The total number of olfactory receptor neurons was estimated to be around 50, and the total neuron count including other modality axons was 70-80 at the base of the flagellum. Electrophysiological experiments revealed that the carrot psyllid can detect a variety of compounds present in extracts from both winter and summer host plants, as well as from extracts of male or female conspecifics. Only very minor differences between male and female response patterns were observed. Four active compounds were identified and tested in dose-response trials. One of them, nonanal, was found in the Trioza extracts, and is thereby the first suggested pheromone compound in a psylloid. A classification of the olfactory receptor neuron (ORN) types present in the sensilla investigated here revealed a significant redundancy, meaning the total number of ORN types in T. apicalis will be considerably fewer than 50. In a comparative study, we show that the antennal lobes (ALs) in T. apicalis and two aphid species lack morphologically distinct glomeruli. We propose that this is due to the exceptionally low number of afferent neurons. Nevertheless, the loosely aggregated organisation of axon terminals indicates targeting to discrete foci within the AL, which are supposedly equivalent to functional glomeruli.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Kristoffersen, Lina, et al.
(författare)
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Sparse sensillar array on Trioza apicalis (Homoptera, Triozidae) antennae—an adaptation to high stimulus levels?
- 2006
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Ingår i: Arthropod Structure & Development. - : Elsevier BV. - 1467-8039. ; 35:2, s. 85-92
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the morphological basis for olfactory reception in the carrot psyllid (Trioza apicalis) we used scanning and transmission electron microscopy. Our study reveals a very sparse sensillar setup. We identify and describe several different types of single-walled sensilla likely to have an olfactory function, as well as mechanosensory hairs and intracuticular sensilla. A T. apicalis antenna is about 0.6 mm long and has 10 segments. Apically on the flagellum there are two conspicuous multi-porous single-walled bristles. There are six cuticular cavities on the flagellum; two smaller on the apical flagellomere, and four larger located on the lateral side of the antenna on flagellomeres 2, 4, 6 and 7. Each cavity contains two sensilla and there are three varieties of cavity sensilla. Mechano- and chemosensory hairs appear in low numbers on all segments but the third. Carrot psyllids most likely use olfactory cues to locate their rather strongly smelling host plants, and we argue that the low number of olfactory sensilla found in this insect may accommodate high concentrations of odour stimuli. There is no sexual dimorphism in the sensillar setup. In concordance with this, no sex pheromones have been described in the Psylloidea so far.
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| 9. |
- Nguyen, Thanh N, et al.
(författare)
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Global Impact of the COVID-19 Pandemic on Stroke Volumes and Cerebrovascular Events: A 1-Year Follow-up.
- 2023
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Ingår i: Neurology. - 1526-632X. ; 100:4
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Tidskriftsartikel (refereegranskat)abstract
- Declines in stroke admission, IV thrombolysis (IVT), and mechanical thrombectomy volumes were reported during the first wave of the COVID-19 pandemic. There is a paucity of data on the longer-term effect of the pandemic on stroke volumes over the course of a year and through the second wave of the pandemic. We sought to measure the effect of the COVID-19 pandemic on the volumes of stroke admissions, intracranial hemorrhage (ICH), IVT, and mechanical thrombectomy over a 1-year period at the onset of the pandemic (March 1, 2020, to February 28, 2021) compared with the immediately preceding year (March 1, 2019, to February 29, 2020).We conducted a longitudinal retrospective study across 6 continents, 56 countries, and 275 stroke centers. We collected volume data for COVID-19 admissions and 4 stroke metrics: ischemic stroke admissions, ICH admissions, IVT treatments, and mechanical thrombectomy procedures. Diagnoses were identified by their ICD-10 codes or classifications in stroke databases.There were 148,895 stroke admissions in the 1 year immediately before compared with 138,453 admissions during the 1-year pandemic, representing a 7% decline (95% CI [95% CI 7.1-6.9]; p < 0.0001). ICH volumes declined from 29,585 to 28,156 (4.8% [5.1-4.6]; p < 0.0001) and IVT volume from 24,584 to 23,077 (6.1% [6.4-5.8]; p < 0.0001). Larger declines were observed at high-volume compared with low-volume centers (all p < 0.0001). There was no significant change in mechanical thrombectomy volumes (0.7% [0.6-0.9]; p = 0.49). Stroke was diagnosed in 1.3% [1.31-1.38] of 406,792 COVID-19 hospitalizations. SARS-CoV-2 infection was present in 2.9% ([2.82-2.97], 5,656/195,539) of all stroke hospitalizations.There was a global decline and shift to lower-volume centers of stroke admission volumes, ICH volumes, and IVT volumes during the 1st year of the COVID-19 pandemic compared with the prior year. Mechanical thrombectomy volumes were preserved. These results suggest preservation in the stroke care of higher severity of disease through the first pandemic year.This study is registered under NCT04934020.
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| 10. |
- Nissinen, Anne, et al.
(författare)
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Physiological state of female and light intensity affect the host-plant selection of carrot psyllid, Trioza apicalis (Hemiptera : Triozidae)
- 2008
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Ingår i: European Journal of Entomology. - 1210-5759. ; 105:2, s. 227-232
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the effect of different light gradient regimes on host-plant selection of the carrot psyllid, Trioza apicalis Forster. In both a strong and a weak light gradient, carrot psyllids preferred a carrot leaf placed in higher light intensity. When the choice was between the host (carrot Daucus carota L.) and a non-host (barley Hordeum vulgare L.) virgin adults settled significantly more often on non-host in higher light intensity than on carrot in lower light intensity. In a weak light gradient, none of the gravid females settled on a non-host. In an experiment without light gradient, gravid females showed a preference for carrot, whereas virgin females settled approximately equally on Norway spruce Picea abies Karst. (winter shelter plant) and carrot. Our results show that virgin and gravid individuals have different host-plant selection behaviour, and that they are sensitive to small differences in light intensity. Both factors can create a source of variation in behavioural assays, and should be taken into consideration in future experiments with this and probably also related species. Our results suggest that carrot psyllids can utilize visual cues (light intensity or wavelength) in host-plant selection, and the role of visual cues should be more thoroughly studied.
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