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Nicholas J. Strausfeld - One of the best experts on this subject based on the ideXlab platform.
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A precocious adult visual center in the larva defines the unique optic lobe of the split-eyed Whirligig Beetle Dineutus sublineatus
Frontiers in Zoology, 2013Co-Authors: Chan Lin, Nicholas J. StrausfeldAbstract:Introduction Whirligig Beetles (Coleoptera: Gyrinidae) are aquatic insects living on the water surface. They are equipped with four compound eyes, an upper pair viewing above the water surface and a lower submerged pair viewing beneath the water surface, but little is known about how their visual brain centers (optic lobes) are organized to serve such unusual eyes. We show here, for the first time, the peculiar optic lobe organization of the larval and adult Whirligig Beetle Dineutus sublineatus . Results The divided compound eyes of adult Whirligig Beetles supply optic lobes that are split into two halves, an upper half and lower half, comprising an upper and lower lamina, an upper and lower medulla and a bilobed partially split lobula. However, the lobula plate, a neuropil that in flies is known to be involved in mediating stabilized flight, exists only in conjunction with the lower lobe of the lobula. We show that, as in another group of predatory Beetle larvae, in the Whirligig Beetle the aquatic larva precociously develops a lobula plate equipped with wide-field neurons. It is supplied by three larval laminas serving the three dorsal larval stemmata, which are adjacent to the developing upper compound eye. Conclusions In adult Whirligig Beetles, dual optic neuropils serve the upper aerial eyes and the lower subaquatic eyes. The exception is the lobula plate. A lobula plate develops precociously in the larva where it is supplied by inputs from three larval stemmata that have a frontal-upper field of view, in which contrasting objects such as prey items trigger a body lunge and mandibular grasp. This precocious lobula plate is lost during pupal metamorphosis, whereas another lobula plate develops normally during metamorphosis and in the adult is associated with the lower eye. The different roles of the upper and lower lobula plates in supporting, respectively, larval predation and adult optokinetic balance are discussed. Precocious development of the upper lobula plate represents convergent evolution of an ambush hunting lifestyle, as exemplified by the terrestrial larvae of tiger Beetles (Cicindelinae), in which activation of neurons in their precocious lobula plates, each serving two large larval stemmata, releases reflex body extension and mandibular grasp.
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a precocious adult visual center in the larva defines the unique optic lobe of the split eyed Whirligig Beetle dineutus sublineatus
Frontiers in Zoology, 2013Co-Authors: Nicholas J. StrausfeldAbstract:Introduction Whirligig Beetles (Coleoptera: Gyrinidae) are aquatic insects living on the water surface. They are equipped with four compound eyes, an upper pair viewing above the water surface and a lower submerged pair viewing beneath the water surface, but little is known about how their visual brain centers (optic lobes) are organized to serve such unusual eyes. We show here, for the first time, the peculiar optic lobe organization of the larval and adult Whirligig Beetle Dineutus sublineatus.
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Visual inputs to the mushroom body calyces of the Whirligig Beetle Dineutus sublineatus: Modality switching in an insect
The Journal of comparative neurology, 2012Co-Authors: Chan Lin, Nicholas J. StrausfeldAbstract:The mushroom bodies are prominent lobed centers in the forebrain, or protocerebrum, of most insects. Previous studies on mushroom bodies have focused on higher olfactory processing, including olfactory-based learning and memory. Anatomical studies provide strong support that in terrestrial insects with mushroom bodies, the primary input region, or calyces, are predominantly supplied by olfactory projection neurons from the antennal lobe glomeruli. In aquatic species that generally lack antennal lobes, the calyces are vestigial or absent. Here we report an exception to this in the Whirligig Beetle Dineutus sublineatus (Coleoptera: Gyrinidae). This aquatic species lives on water and is equipped with two separate pairs of compound eyes, one pair viewing above and one viewing below the water surface. As in other aquatic insects, the Whirligig Beetle lacks antennal lobes, but unlike other aquatic insects its mushroom bodies possess robust calyces. Golgi impregnations and fluorescent tracer injections revealed that the calyces are exclusively supplied by visual neurons from the medulla of the dorsal eye optic lobes. No other sensory inputs reach the calyces, thereby showing a complete switch of calyx modality from olfaction to vision. Potential functions of the mushroom bodies of D. sublineatus are discussed in the context of the behavioral ecology of Whirligig Beetles.
Beate Nürnberger - One of the best experts on this subject based on the ideXlab platform.
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Local dynamics and dispersal in a structured population of the Whirligig Beetle Deneutus assimilis
Oecologia, 1996Co-Authors: Beate NürnbergerAbstract:The study illustrates the ecological determinants and evolutionary consequences of dispersal in the pond-living water Beetle Dineutus assimilis (Coleoptera: Gyrinidae). Over 2 years, local populatiopn dynamics were studied in 51 ponds within a 60-km^2 study area. In most of the 31 occupied ponds, and even in large populations, abundances changed dramatically from one year to the next. Nine extinction and nine colonisation events were observed. These temporal patterns show no sign of spatial autocorrelation. Such a habitat distribution should favour high dispersal rates. Indeed, D. assimilis was found to be a very effective coloniser of newly available sites (mean propagule size: 23). A mark-recapture study showed that most dispersal occurred after diapause and over distances ranging from 100 m to at least 20 km. Yet despite frequent movement, the local variability in environmental conditions maintiins a large variance in average reproductive success per pond. Furthermore, immigration rates vary widely within a season. The apparent lack of correlation between these two sources of variation should greatly strengthen the role of drift in this system. A companion paper (Nürnberger and Harrison 1995) documents a non-random distribution of mitochondrial haplotypes due to recent population bottlenecks.
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SPATIAL POPULATION STRUCTURE IN THE Whirligig Beetle
1995Co-Authors: Beate Nürnberger, Richard G. HarrisonAbstract:The spatial population structure of the pond-living water Beetle Dineutus assimilis (Coleoptera: Gyrinidae) was investigated through a field study of population dynamics and dispersal, with a concurrent assessment of the spatial distribution of mitochondrial DNA (mtDNA) restriction-fragment-length polymorphism (RFLP). A compre- hensive 2-yr survey within a 60-km2 study area revealed pronounced fluctuations in local abundances, including extinctions and colonizations. The recapture of marked individuals showed that dispersal among ponds is frequent in both males and females and connects populations on a large geographic scale (maximum observed flight distance: 20 km). The population structure of D. assimilis is thus characterized by both pronounced genetic drift and frequent gene flow. Together, these two forces generate a pattern of very local and transient genetic differentiation. Mitochondrial DNA samples collected within a few kilometers indicate highly significant spatial structure, if newly founded demes or those that experienced recent bottlenecks are included. These results based on four demes within the study area were placed into a regional context by further samples collected at distances of 100 km and 200 km. Ft estimates computed on increasing spatial scales were variable but showed no increasing trend. Thus, gene flow exerts a strong homogenizing force over a wide geographic range but is counteracted locally by genetic drift. These findings highlight the need to supplement estimates of Ft with additional data to arrive at valid interpretations of the genetic information. More generally, this study raises questions about how to capture the relevant features of dynamic, subdivided pop- ulations to understand their evolutionary dynamics.
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SPATIAL POPULATION STRUCTURE IN THE Whirligig Beetle DINEUTUS ASSIMILIS : EVOLUTIONARY INFERENCES BASED ON MITOCHONDRIAL DNA AND FIELD DATA
Evolution; international journal of organic evolution, 1995Co-Authors: Beate Nürnberger, Richard G. HarrisonAbstract:The spatial population structure of the pond-living water Beetle Dineutus assimilis (Coleoptera: Gyrinidae) was investigated through a field study of population dynamics and dispersal, with a concurrent assessment of the spatial distribution of mitochondrial DNA (mtDNA) restriction-fragment-length polymorphism (RFLP). A comprehensive 2-yr survey within a 60-km2 study area revealed pronounced fluctuations in local abundances, including extinctions and colonizations. The recapture of marked individuals showed that dispersal among ponds is frequent in both males and females and connects populations on a large geographic scale (maximum observed flight distance: 20 km). The population structure of D. assimilis is thus characterized by both pronounced genetic drift and frequent gene flow. Together, these two forces generate a pattern of very local and transient genetic differentiation. Mitochondrial DNA samples collected within a few kilometers indicate highly significant spatial structure, if newly founded demes or those that experienced recent bottlenecks are included. These results based on four demes within the study area were placed into a regional context by further samples collected at distances of 100 km and 200 km. Fst estimates computed on increasing spatial scales were variable but showed no increasing trend. Thus, gene flow exerts a strong homogenizing force over a wide geographic range but is counteracted locally by genetic drift. These findings highlight the need to supplement estimates of Fst with additional data to arrive at valid interpretations of the genetic information. More generally, this study raises questions about how to capture the relevant features of dynamic, subdivided populations to understand their evolutionary dynamics.
Grey T. Gustafson - One of the best experts on this subject based on the ideXlab platform.
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Burmese amber reveals a new stem lineage of Whirligig Beetle (Coleoptera: Gyrinidae) based on the larval stage.
Zoological journal of the Linnean Society, 2020Co-Authors: Grey T. Gustafson, Mariano C. Michat, Michael BalkeAbstract:Burmese amber is well known for preserving unique extinct lineages of insects. Here, we describe a new fossil Beetle in its larval stage from Burmese amber. Bayesian and parsimony phylogenetic analysis of 50 morphological characters support this fossil as being sister to both the tribes Dineutini and Orectochilini, representing an extinct stem lineage in Gyrininae. It is described here as a new genus and species of Whirligig Beetle, Chimerogyrus gigagalea gen. & sp. nov., a taxon that preserves remarkable intermediate features between the Whirligig Beetle tribe Gyrinini and the crown Orectochilini and Dineutini. This new taxon preserves key features for studying the evolution of characters within the larval stage of the Gyrinidae and highlights the importance of Burmese amber for preserving both stem and crown lineages present during the mid-Cretaceous, before the end-Cretaceous mass extinction event.
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Larval description and chaetotaxic analysis of Dineutus sinuosipennis Laporte, 1840, with a key for the identification of larvae of the tribe Dineutini (Coleoptera, Gyrinidae).
ZooKeys, 2017Co-Authors: Mariano C. Michat, Grey T. Gustafson, Johannes BergstenAbstract:The larvae of the Malagasy Whirligig Beetle Dineutus sinuosipennis Laporte, 1840, identified using DNA sequence data, are described and illustrated for the first time, including detailed morphometric and chaetotaxic analyses of selected structures and a description of larval habitat. Larvae of the genus Dineutus Macleay, 1825 are diagnosed, and a key to identify the genera of the tribe Dineutini is presented. Larvae of Dineutus exhibit the characters traditionally recognized as autapomorphies of the Gyrinidae: body less sclerotized, egg bursters located on the parietal, one additional sensorial plate on the third antennomere, cardo and lacinia well developed, prementum completely divided, abdominal tracheal gills, and four terminal hooks on the pygopod. They also share with larvae of the other Dineutini genera these putative synapomorphies: numerous minute pore-like additional structures on the ultimate maxillary and labial palpomeres, coxal primary seta CO12 inserted submedially, and trochanteral primary seta TR2 absent. Larvae of Dineutus can be distinguished from those of other known genera of Dineutini by the posterior margin of the lacinia not dentate, tracheal gills plumose, parietal seta PA5 inserted relatively far from setae PA7-9, mandibular pores MNb and MNc inserted relatively far from each other, and tarsal seta TA1 inserted submedially.
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A North American Biodiversity Hotspot Gets Richer: A New Species of Whirligig Beetle (Coleoptera: Gyrinidae) From the Southeastern Coastal Plain of the United States
2017Co-Authors: Grey T. Gustafson, Robert W. SitesAbstract:A new species of Dineutus Macleay, 1825 is described from the Southeastern CoastalPlain of the United Sates. Habitus and aedeagus images as well as illustrations of elytralapices, protarsus, palps, and male mesopretarsal claws are provided for Dineutus shorti n.sp. and compared to those of D. discolor Aubé, 1838. The importance of theSoutheastern Coastal Plain as a biodiversity hotspot and the potential conservationconcern of D. shorti n. sp. also are discussed.
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Tip-dated phylogeny of Whirligig Beetles reveals ancient lineage surviving on Madagascar
Scientific Reports, 2017Co-Authors: Grey T. Gustafson, Rasa Bukontaite, Alexander A. Prokin, Johannes Bergsten, Kelly B. MillerAbstract:The temporal origin of Madagascar’s extraordinary endemic diversity is debated. A preference for Cenozoic dispersal origins has replaced the classical view of Mesozoic vicariance in the wake of molecular dating. However, evidence of ancient origins is mounting from arthropod groups. Using phylogenetic ‘tip-dating’ analysis with fossils, we show that a Whirligig Beetle species, Heterogyrus milloti , inhabiting forest streams in southeastern Madagascar is the last survivor of a once dominant and widespread Mesozoic group. With a Late Triassic to Early Jurassic origin (226–187 Ma) it is the hitherto oldest dated endemic lineage of animal or plant on Madagascar. Island biotas’ sensitivity to extinction is well known, but islands can also provide refuge from continental extinction. Heterogyrus milloti is an irreplaceable link to the freshwater biota of the Mesozoic and serves as a reminder of what may be lost without critical conservation efforts on Madagascar.
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The Morphology and Behavior of the Endemic Malagasy Whirligig Beetle Heterogyrus milloti Legros, 1953 (Coleoptera: Gyrinidae: Heterogyrinae)
The Coleopterists Bulletin, 2017Co-Authors: Grey T. Gustafson, Johannes Bergsten, Tolotra Ranarilalatiana, Jacquelin Herisahala Randriamihaja, Kelly B. MillerAbstract:Abstract The Malagasy endemic Whirligig Beetle Heterogyrus milloti Legros, 1953 is redescribed. Jumping behavior of H. milloti is reported here for the first time with video recordings provided. Results of a behavioral experiment conducted in the field demonstrate H. milloti jumps in a targeted manner in a downstream direction. The unique habitat of H. milloti is described in detail with both image and video of the habitat included. Morphology of H. milloti is discussed in detail, revealing symplesiomorphies with Spanglerogyrus Folkerts, 1979, characters forming transitional series between Spanglerogyrus and the Gyrininae, and features unique to H. milloti. The potential adaptive significance of these peculiar morphological features in association with the habitat of H. milloti is discussed. Finally, an argument for the necessity of conservation of this species is made, and common names in English, French, Malagasy, and Swedish for H. milloti are proposed to aid conservation efforts.
Richard G. Harrison - One of the best experts on this subject based on the ideXlab platform.
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SPATIAL POPULATION STRUCTURE IN THE Whirligig Beetle
1995Co-Authors: Beate Nürnberger, Richard G. HarrisonAbstract:The spatial population structure of the pond-living water Beetle Dineutus assimilis (Coleoptera: Gyrinidae) was investigated through a field study of population dynamics and dispersal, with a concurrent assessment of the spatial distribution of mitochondrial DNA (mtDNA) restriction-fragment-length polymorphism (RFLP). A compre- hensive 2-yr survey within a 60-km2 study area revealed pronounced fluctuations in local abundances, including extinctions and colonizations. The recapture of marked individuals showed that dispersal among ponds is frequent in both males and females and connects populations on a large geographic scale (maximum observed flight distance: 20 km). The population structure of D. assimilis is thus characterized by both pronounced genetic drift and frequent gene flow. Together, these two forces generate a pattern of very local and transient genetic differentiation. Mitochondrial DNA samples collected within a few kilometers indicate highly significant spatial structure, if newly founded demes or those that experienced recent bottlenecks are included. These results based on four demes within the study area were placed into a regional context by further samples collected at distances of 100 km and 200 km. Ft estimates computed on increasing spatial scales were variable but showed no increasing trend. Thus, gene flow exerts a strong homogenizing force over a wide geographic range but is counteracted locally by genetic drift. These findings highlight the need to supplement estimates of Ft with additional data to arrive at valid interpretations of the genetic information. More generally, this study raises questions about how to capture the relevant features of dynamic, subdivided pop- ulations to understand their evolutionary dynamics.
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SPATIAL POPULATION STRUCTURE IN THE Whirligig Beetle DINEUTUS ASSIMILIS : EVOLUTIONARY INFERENCES BASED ON MITOCHONDRIAL DNA AND FIELD DATA
Evolution; international journal of organic evolution, 1995Co-Authors: Beate Nürnberger, Richard G. HarrisonAbstract:The spatial population structure of the pond-living water Beetle Dineutus assimilis (Coleoptera: Gyrinidae) was investigated through a field study of population dynamics and dispersal, with a concurrent assessment of the spatial distribution of mitochondrial DNA (mtDNA) restriction-fragment-length polymorphism (RFLP). A comprehensive 2-yr survey within a 60-km2 study area revealed pronounced fluctuations in local abundances, including extinctions and colonizations. The recapture of marked individuals showed that dispersal among ponds is frequent in both males and females and connects populations on a large geographic scale (maximum observed flight distance: 20 km). The population structure of D. assimilis is thus characterized by both pronounced genetic drift and frequent gene flow. Together, these two forces generate a pattern of very local and transient genetic differentiation. Mitochondrial DNA samples collected within a few kilometers indicate highly significant spatial structure, if newly founded demes or those that experienced recent bottlenecks are included. These results based on four demes within the study area were placed into a regional context by further samples collected at distances of 100 km and 200 km. Fst estimates computed on increasing spatial scales were variable but showed no increasing trend. Thus, gene flow exerts a strong homogenizing force over a wide geographic range but is counteracted locally by genetic drift. These findings highlight the need to supplement estimates of Fst with additional data to arrive at valid interpretations of the genetic information. More generally, this study raises questions about how to capture the relevant features of dynamic, subdivided populations to understand their evolutionary dynamics.
Chan Lin - One of the best experts on this subject based on the ideXlab platform.
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A precocious adult visual center in the larva defines the unique optic lobe of the split-eyed Whirligig Beetle Dineutus sublineatus
Frontiers in Zoology, 2013Co-Authors: Chan Lin, Nicholas J. StrausfeldAbstract:Introduction Whirligig Beetles (Coleoptera: Gyrinidae) are aquatic insects living on the water surface. They are equipped with four compound eyes, an upper pair viewing above the water surface and a lower submerged pair viewing beneath the water surface, but little is known about how their visual brain centers (optic lobes) are organized to serve such unusual eyes. We show here, for the first time, the peculiar optic lobe organization of the larval and adult Whirligig Beetle Dineutus sublineatus . Results The divided compound eyes of adult Whirligig Beetles supply optic lobes that are split into two halves, an upper half and lower half, comprising an upper and lower lamina, an upper and lower medulla and a bilobed partially split lobula. However, the lobula plate, a neuropil that in flies is known to be involved in mediating stabilized flight, exists only in conjunction with the lower lobe of the lobula. We show that, as in another group of predatory Beetle larvae, in the Whirligig Beetle the aquatic larva precociously develops a lobula plate equipped with wide-field neurons. It is supplied by three larval laminas serving the three dorsal larval stemmata, which are adjacent to the developing upper compound eye. Conclusions In adult Whirligig Beetles, dual optic neuropils serve the upper aerial eyes and the lower subaquatic eyes. The exception is the lobula plate. A lobula plate develops precociously in the larva where it is supplied by inputs from three larval stemmata that have a frontal-upper field of view, in which contrasting objects such as prey items trigger a body lunge and mandibular grasp. This precocious lobula plate is lost during pupal metamorphosis, whereas another lobula plate develops normally during metamorphosis and in the adult is associated with the lower eye. The different roles of the upper and lower lobula plates in supporting, respectively, larval predation and adult optokinetic balance are discussed. Precocious development of the upper lobula plate represents convergent evolution of an ambush hunting lifestyle, as exemplified by the terrestrial larvae of tiger Beetles (Cicindelinae), in which activation of neurons in their precocious lobula plates, each serving two large larval stemmata, releases reflex body extension and mandibular grasp.
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Visual inputs to the mushroom body calyces of the Whirligig Beetle Dineutus sublineatus: Modality switching in an insect
The Journal of comparative neurology, 2012Co-Authors: Chan Lin, Nicholas J. StrausfeldAbstract:The mushroom bodies are prominent lobed centers in the forebrain, or protocerebrum, of most insects. Previous studies on mushroom bodies have focused on higher olfactory processing, including olfactory-based learning and memory. Anatomical studies provide strong support that in terrestrial insects with mushroom bodies, the primary input region, or calyces, are predominantly supplied by olfactory projection neurons from the antennal lobe glomeruli. In aquatic species that generally lack antennal lobes, the calyces are vestigial or absent. Here we report an exception to this in the Whirligig Beetle Dineutus sublineatus (Coleoptera: Gyrinidae). This aquatic species lives on water and is equipped with two separate pairs of compound eyes, one pair viewing above and one viewing below the water surface. As in other aquatic insects, the Whirligig Beetle lacks antennal lobes, but unlike other aquatic insects its mushroom bodies possess robust calyces. Golgi impregnations and fluorescent tracer injections revealed that the calyces are exclusively supplied by visual neurons from the medulla of the dorsal eye optic lobes. No other sensory inputs reach the calyces, thereby showing a complete switch of calyx modality from olfaction to vision. Potential functions of the mushroom bodies of D. sublineatus are discussed in the context of the behavioral ecology of Whirligig Beetles.
