Flagellar waveforms of gametes in the brown alga Ectocarpus siliculosus

Brown algae are members of the Stramenopiles and their gametes generally have two heterogeneous flagella: a long anterior flagellum (AF) with mastigonemes and a short posterior flagellum (PF). In this study, swimming paths and flagellar waveforms in free-swimming and thigmotactic-swimming male and female gametes and in male gametes during chemotaxis, were quantitatively analysed in the model brown alga Ectocarpus siliculosus. This analysis was performed using a high-speed video camera. It was revealed that the AF plays a role in changing the locomotion of male and female gametes from free-swimming to thigmotactic-swimming and also in changing the swimming path of male gametes from linear to circular during chemotaxis. In the presence of a sex pheromone, male gametes changed their swimming path from linear (swimming path curvature, 0–0.02 µm^–1) to middle and small circular path (swimming path curvature, 0.04–0.20 µm^–1). The flagellar asymmetry and the deflection angle of the AF became larger, whereas the oscillation pattern of the AF was stable. However, there was no correlation between the flagellar asymmetry and the deflection angle of the AF and the path curvature when the male gametes showed middle to small circular paths. The PF irregularly changed the deflection angle and the oscillation pattern was unstable depending on the gradient of the sex pheromone concentration. AF waveforms were independent of PF locomotion during chemotaxis. This means that the AF has the ability to change the swimming path of male gametes – for example, from a highly linear path to a circular path – while changes in locomotion from a middle circle path to a small circle path is the result of beating of the PF.     

Sensory and Behavioral Components of Neocortical Signal Flow in Discrimination Tasks with Short-Term Memory

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Excitatory neuronal CHD8 in the regulation of neocortical development and sensory-motor behaviors

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The synganglion of the jumping spider Marpissa muscosa (Arachnida: Salticidae): Insights from histology,immunohistochemistry and microCT analysis

Jumping spiders are known for their extraordinary cognitive abilities. The underlying nervous system structures, however, are largely unknown. Here, we explore and describe the anatomy of the brain in the jumping spider Marpissa muscosa (Clerck, 1757) by means of paraffin histology, X-ray microCT analysis and immunohistochemistry as well as three-dimensional reconstruction. In the prosoma, the CNS is a clearly demarcated mass that surrounds the esophagus. The anteriormost neuromere, the protocerebrum, comprises nine bilaterally paired neuropils, including the mushroom bodies and one unpaired midline neuropil, the arcuate body. Further ventrally, the synganglion comprises the cheliceral (deutocerebrum) and pedipalpal neuropils (tritocerebrum). Synapsin-immunoreactivity in all neuropils is generally strong, while allatostatin-immunoreactivity is mostly present in association with the arcuate body and the stomodeal bridge. The most prominent neuropils in the spider brain, the mushroom bodies and the arcuate body, were suggested to be higher integrating centers of the arthropod brain. The mushroom body in M. muscosa is connected to first and second order visual neuropils of the lateral eyes, and the arcuate body to the second order neuropils of the anterior median eyes (primary eyes) through a visual tract. The connection of both, visual neuropils and eyes and arcuate body, as well as their large size corroborates the hypothesis that these neuropils play an important role in cognition and locomotion control of jumping spiders. In addition, we show that the architecture of the brain of M. muscosa and some previously investigated salticids differs significantly from that of the wandering spider Cupiennius salei, especially with regard to structure and arrangement of visual neuropils and mushroom body. Thus, we need to explore the anatomical conformities and specificities of the brains of different spider taxa in order to understand evolutionary transformations of the arthropod brain.     

Nervenfasern mit ultrastrukturell verschiedenen Elementargranula im Hypophysenhinterlappen des Rhesusaffen

Zusammenfassung Im Hypophysenhinterlappen des Affen lassen sich elektronenmikroskopisch zwei Arten markarmer, neurosekrethaltiger Nervenfasern beobachten. Sie unterscheiden sich voneinander durch den Typ der Elementargranula, die sie enthalten.In Nervenfasern des Typs I haben die Elementargranula einen Durchmesser von 1500 bis 3500 Å. Sie besitzen eine geringe Elektronendichte und enthalten oft kreisförmig angeordnete Proteinkörnchen. Vereinzelt sind kristallähnliche Formationen des Granulainhalts zu erkennen.Die Elementargranula in Nervenfasern des Typs II messen 1200–2200 Å im Durchmesser. Ihr Inhalt besitzt infolge eng aneinander gelagerter granulärer Teilchen eine weitaus größere Elektronendichte als die Granula des Typs I. Kristallähnliche Granulaeinschlüsse waren nicht zu sehen.Die ultrastrukturelle Differenzierung zweier Nervenfasergruppen im Hypophysenhinterlappen wirft die Frage auf, ob es sich bei dem einen Typ um vasopressin-bei dem anderen Typ um oxytocinhaltige hypothalamische Nervenfasern handelt.Die Pituizyten im Hypophysenhinterlappen des Rhesusaffen besitzen Granula (1500 bis 3000 Å) mit einer Innenstruktur ähnlich den Neurosekretgranula vom Typ II. Sie enthalten außerdem größere, fein granulierte osmiophile Grana.

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Neurosecretory nerve fibres containing ultrastructurally different elementary granules in the hypophysial posterior lobe of the rhesus monkey

Summary In the posterior lobe of the neurohypophysis of the rhesus monkey, two kinds of unmyelinated nerve fibres containing neurosecretory substance can be discerned with the electron microscope. They differ with respect to the type of elementary granules they contain.In type I nerve fibres the elementary granules have a diameter of 1,500–3,500 Å. They are of little electron-density and often contain circularly arranged protein grains. Crystal-like formations of the content of the granules are sometimes observed.In type II nerve fibres the elementary granules measure 1,200–2,200 Å in diameter. Due to close packing of their granular content they are much more electron-dense than type I granules. Crystal-like inclusions were not seen.The ultrastructural differentiation of two groups of nerve fibres in the posterior lobe raises the question of whether the one type consists of vasopressin-containing and the other of oxytocin-containing hypothalamic nerve fibres.The pituicytes in the hypophysial posterior lobe of the rhesus monkey contain granules (1,500–3,000 Å) with an inner structure similar to type II neurosecretory granules. In addition, they contain larger, finely granulated osmiophilic grains.

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