A miniaturized nigrostriatal-like circuit regulating locomotor performance in a protochordate

To gain insight into the evolution of motor control systems at the origin of vertebrates, we have investigated higher-order motor circuitry in the protochordate Oikopleura dioica. We have identified a highly miniaturized circuit in Oikopleura with a projection from a single pair of dopaminergic neurons to a small set of synaptically coupled GABAergic neurons, which in turn exert a disinhibitory descending projection onto the locomotor central pattern generator. The circuit is reminiscent of the nigrostriatopallidal system in the vertebrate basal ganglia, in which disinhibitory circuits release specific movements under the modulatory control of dopamine. We demonstrate further that dopamine is required to optimize locomotor performance in Oikopleura, mirroring its role in vertebrates. A dopamine-regulated disinhibitory locomotor control circuit reminiscent of the vertebrate nigrostriatopallidal system was thus already present at the origin of ancestral chordates and has been maintained in the face of extreme nervous system miniaturization in the urochordate lineage.publishedVersio

Five New Species of Guimaraesiella (Phthiraptera: Ischnocera) from Broadbills (Aves: Passeriformes: Calyptomenidae: Eurylaimidae)

Under embargo until: 2020-11-15Five new species of Guimaraesiella Eichler, 1949 are described and illustrated from hosts in the Eurylaimidae and Calyptomenidae. They are Guimaraesiella corydoni n. sp. from Corydon sumatranus laoensisMeyer de Schauensee, 1929; Guimaraesiella latirostris n. sp. from Eurylaimus ochromalusRaffles, 1822; Guimaraesiella cyanophoba n. sp. from Cymbirhynchus macrorhynchus malaccensisSalvadori, 1874 and C. m. siamensisMeyer de Schauensee and Ripley, 1940; Guimaraesiella altunai n. sp. from Calyptomena viridis caudacutaSwainson, 1838; and Guimaraesiella forcipata n. sp. from Eurylaimus steerii steeriiSharpe, 1876. These represent the first species of Guimaraesiella described from the Calyptomenidae and Eurylaimidae, as well as the first species of this genus described from the Old World suboscines.acceptedVersio

Transcriptional adaptation in caenorhabditis elegans

Transcriptional adaptation is a recently described phenomenon by which a mutation in one gene leads to the transcriptional modulation of related genes, termed adapting genes. At the molecular level, it has been proposed that the mutant mRNA, rather than the loss of protein function, activates this response. While several examples of transcriptional adaptation have been reported in zebrafish embryos and in mouse cell lines, it is not known whether this phenomenon is observed across metazoans. Here we report transcriptional adaptation in C. elegans, and find that this process requires factors involved in mutant mRNA decay, as in zebrafish and mouse. We further uncover a requirement for Argonaute proteins and Dicer, factors involved in small RNA maturation and transport into the nucleus. Altogether, these results provide evidence for transcriptional adaptation in C. elegans, a powerful model to further investigate underlying molecular mechanisms.publishedVersio

Gap junction-dependent coordination of intercellular calcium signalling in the developing appendicularian tunicate Oikopleura dioica

We characterized spontaneous Ca2+ signals in Oikopleura dioica embryos from pre-fertilization to gastrula stages following injection of GCaMP6 mRNA into unfertilized eggs. The unfertilized egg exhibited regular, transient elevations in intracellular Ca2+ concentration with an average duration of 4–6 s and an average frequency of about 1 every 2.5 min. Fertilization was accompanied by a longer Ca2+ transient that lasted several minutes. Thereafter, regular Ca2+ transients were reinstated that spread within seconds among blastomeres and gradually increased in duration (by about 50%) and decreased in frequency (by about 20%) by gastrulation. Peak amplitudes also exhibited a dynamic, with a transitory drop occurring at about the 4-cell stage and a subsequent rise. Each peak was preceded by about 15 s by a smaller and shorter Ca2+ increase (about 5% of the main peak amplitude, average duration 3 s), which we term the “minipeak”. By gastrulation, Ca2+ transients exhibited a stereotyped initiation site on either side of the 32-64-cell embryo, likely in the nascent muscle precursor cells, and spread thereafter symmetrically in a stereotyped spatial pattern that engaged blastomeres giving rise to all the major tissue lineages. The rapid spread of the transients relative to the intertransient interval created a coordinated wave that, on a coarse time scale, could be considered an approximate synchronization. Treatment with the divalent cations Ni2+ or Cd2+ gradually diminished peak amplitudes, had only moderate effects on wave frequency, but markedly disrupted wave synchronization and normal development. The T-type Ca2+ channel blocker mibefradil similarly disrupted normal development, and eliminated the minipeaks, but did not affect wave synchronization. To assess the role of gap junctions in calcium wave spread and coordination, we first characterized the expression of two Oikopleura connexins, Od-CxA and Od-CxB, both of which are expressed during pre-gastrulation and gastrula stages, and then co-injected double-stranded inhibitory RNAs together with CGaMP6 to suppress connexin expression. Connexin mRNA knockdown led to a gradual increase in Ca2+ transient peak width, a decrease of interpeak interval and a marked disruption of wave synchronization. As seen with divalent cations and mibefradil, this desynchronization was accompanied by a disruption of normal development

Gap junction-dependent coordination of intercellular calcium signalling in the developing appendicularian tunicate Oikopleura dioica

We characterized spontaneous Ca2+ signals in Oikopleura dioica embryos from pre-fertilization to gastrula stages following injection of GCaMP6 mRNA into unfertilized eggs. The unfertilized egg exhibited regular, transient elevations in intracellular Ca2+ concentration with an average duration of 4–6 s and an average frequency of about 1 every 2.5 min. Fertilization was accompanied by a longer Ca2+ transient that lasted several minutes. Thereafter, regular Ca2+ transients were reinstated that spread within seconds among blastomeres and gradually increased in duration (by about 50%) and decreased in frequency (by about 20%) by gastrulation. Peak amplitudes also exhibited a dynamic, with a transitory drop occurring at about the 4-cell stage and a subsequent rise. Each peak was preceded by about 15 s by a smaller and shorter Ca2+ increase (about 5% of the main peak amplitude, average duration 3 s), which we term the “minipeak”. By gastrulation, Ca2+ transients exhibited a stereotyped initiation site on either side of the 32-64-cell embryo, likely in the nascent muscle precursor cells, and spread thereafter symmetrically in a stereotyped spatial pattern that engaged blastomeres giving rise to all the major tissue lineages. The rapid spread of the transients relative to the intertransient interval created a coordinated wave that, on a coarse time scale, could be considered an approximate synchronization. Treatment with the divalent cations Ni2+ or Cd2+ gradually diminished peak amplitudes, had only moderate effects on wave frequency, but markedly disrupted wave synchronization and normal development. The T-type Ca2+ channel blocker mibefradil similarly disrupted normal development, and eliminated the minipeaks, but did not affect wave synchronization. To assess the role of gap junctions in calcium wave spread and coordination, we first characterized the expression of two Oikopleura connexins, Od-CxA and Od-CxB, both of which are expressed during pre-gastrulation and gastrula stages, and then co-injected double-stranded inhibitory RNAs together with CGaMP6 to suppress connexin expression. Connexin mRNA knockdown led to a gradual increase in Ca2+ transient peak width, a decrease of interpeak interval and a marked disruption of wave synchronization. As seen with divalent cations and mibefradil, this desynchronization was accompanied by a disruption of normal development

Neuronal gene expression in two generations of the marine parasitic worm, Cryptocotyle lingua

Abstract Trematodes, or flukes, undergo intricate anatomical and behavioral transformations during their life cycle, yet the functional changes in their nervous system remain poorly understood. We investigated the molecular basis of nervous system function in Cryptocotyle lingua, a species of relevance for fisheries. Transcriptomic analysis revealed a streamlined molecular toolkit with the absence of key signaling pathways and ion channels. Notably, we observed the loss of nitric oxide synthase across the Platyhelminthes. Furthermore, we identified upregulated neuronal genes in dispersal larvae, including those involved in aminergic pathways, synaptic vesicle trafficking, TRPA channels, and surprisingly nitric oxide receptors. Using neuronal markers and in situ hybridization, we hypothesized their functional relevance to larval adaptations and host-finding strategies. Additionally, employing a behavior quantification toolkit, we assessed cercaria motility, facilitating further investigations into the behavior and physiology of parasitic flatworms. This study enhances our understanding of trematode neurobiology and provides insights for targeted antiparasitic strategies

Five New Species of Guimaraesiella (Phthiraptera: Ischnocera) from Broadbills (Aves: Passeriformes: Calyptomenidae: Eurylaimidae)

Five new species of Guimaraesiella Eichler, 1949 are described and illustrated from hosts in the Eurylaimidae and Calyptomenidae. They are Guimaraesiella corydoni n. sp. from Corydon sumatranus laoensisMeyer de Schauensee, 1929; Guimaraesiella latirostris n. sp. from Eurylaimus ochromalusRaffles, 1822; Guimaraesiella cyanophoba n. sp. from Cymbirhynchus macrorhynchus malaccensisSalvadori, 1874 and C. m. siamensisMeyer de Schauensee and Ripley, 1940; Guimaraesiella altunai n. sp. from Calyptomena viridis caudacutaSwainson, 1838; and Guimaraesiella forcipata n. sp. from Eurylaimus steerii steeriiSharpe, 1876. These represent the first species of Guimaraesiella described from the Calyptomenidae and Eurylaimidae, as well as the first species of this genus described from the Old World suboscines

Captive individuals of endangered Philippine raptors maintain native feather mites (Acariformes: Pterolichoidea) species

Endangered species of hosts are coupled with endangered species of parasites, which share the risk of co-extinction. Conservation efforts sometimes include breeding of rare species in captivity. Data on parasites of captive populations of endangered species is scarce and the ability of small numbers of captive host individuals to support the biodiversity of native parasites is limited. Examination of ectosymbionts of the critically endangered Philippine eagles and the endangered Mindanao Hawk-Eagle kept at the Philippine Eagle Center, Philippines, revealed three feather mite species despite regular treatment with insecticide powder. No other ectosymbiont taxa were detected. Studies in morphology and molecular phylogeny of these feather mites based on mitochondrial and nuclear DNA markers indicate that species found were typical for Accipitridae. Three new pterolichoid feather mite species (Acari: Pterolichoidea) were described from two species of eagles (Accipitriformes: Accipitridae) endemic to the Philippines: Hieracolichus philippinensis sp. n. (Gabuciniidae) and Pseudalloptinus pithecophagae sp. n. (Pterolichidae) from the Great Philippine Eagle Pithecophaga jefferyi Ogilvie-Grant, 1896, and Pseudogabucinia nisaeti sp. n. (Kramerellidae) from the Mindanao Hawk-Eagle Nisaetus pinskeri Gould, 1863. The presence of H. philippinensis on P. jefferyi supports the recent finding that the Great Philippine Eagle belongs to the lineage of serpent eagles (Circaetinae) rather than to the Harpy and other eagles

Functionally asymmetric motor neurons contribute to coordinating locomotion of Caenorhabditis elegans

Locomotion circuits developed in simple animals, and circuit motifs further evolved in higher animals. To understand locomotion circuit motifs, they must be characterized in many models. The nematode Caenorhabditis elegans possesses one of the best-studied circuits for undulatory movement. Yet, for 1/6th of the cholinergic motor neurons (MNs), the AS MNs, functional information is unavailable. Ventral nerve cord (VNC) MNs coordinate undulations, in small circuits of complementary neurons innervating opposing muscles. AS MNs differ, as they innervate muscles and other MNs asymmetrically, without complementary partners. We characterized AS MNs by optogenetic, behavioral and imaging analyses. They generate asymmetric muscle activation, enabling navigation, and contribute to coordination of dorso-ventral undulation as well as anterio-posterior bending wave propagation. AS MN activity correlated with forward and backward locomotion, and they functionally connect to premotor interneurons (PINs) for both locomotion regimes. Electrical feedback from AS MNs via gap junctions may affect only backward PINs

Diversity and host associations of Myrsidea chewing lice (Phthiraptera: Menoponidae) in the tropical rainforest of Malaysian Borneo

The tropical rainforests of Sundaland are a global biodiversity hotspot increasingly threatened by human activities. While parasitic insects are an important component of the ecosystem, their diversity and parasite-host relations are poorly understood in the tropics. We investigated parasites of passerine birds, the chewing lice of the speciose genus Myrsidea Waterston, 1915 (Phthiraptera: Menoponidae) in a natural rainforest community of Malaysian Borneo. Based on morphology, we registered 10 species of lice from 14 bird species of six different host families. This indicated a high degree of host specificity and that the complexity of the system could be underestimated with the potential for cryptic lineages/species to be present. We tested the species boundaries by combining morphological, genetic and host speciation diversity. The phylogenetic relationships of lice were investigated by analyzing the partial mitochondrial cytochrome oxidase I (COI) and the nuclear elongation factor alpha (EF-1α) genes sequences of the species. This revealed a monophyletic group of Myrsidea lineages from seven hosts of the avian family Pycnonotidae, one host of Timaliidae and one host of Pellorneidae. However, species delimitation methods supported the species boundaries hypothesized by morphological studies and confirmed that four species of Myrsidea are not single host specific. Cophylogenetic analysis by both distance-based test ParaFit and event-based method Jane confirmed overall congruence between the phylogenies of Myrsidea and their hosts. In total we recorded three cospeciation events for 14 host-parasite associations. However only one host-parasite link (M. carmenae and their hosts Terpsiphone affinis and Hypothymis azurea) was significant after the multiple testing correction in ParaFit. Four new species are described: Myrsidea carmenae sp.n. ex Hypothymis azurea and Terpsiphone affinis, Myrsidea franciscae sp.n. ex Rhipidura javanica, Myrsidea ramoni sp.n. ex Copsychus malabaricus stricklandii, and Myrsidea victoriae sp.n. ex. Turdinus sepiarius