Biology subjects

Arendt, D.

Publications and source records attributed to Arendt, D..

4 recordsLinked to original sources

bioRxiv2018

Whole-head recording of chemosensory activity in the marine annelid Platynereis dumerilii

Chemical detection is key to various behaviours in both marine and terrestrial animals. Marine species, though highly diverse, have been underrepresented so far in studies on chemosensory systems, and our knowledge mostly concerns the detection of airborne cues. A broader comparative approach is therefore desirable. Marine annelid worms with their rich behavioural repertoire represent attractive models for chemosensory studies. Here, we study the marine worm Platynereis dumerilii to provide the first comprehensive study of head chemosensory organ physiology in an annelid. By combining microfluidics and calcium imaging, we record neuronal activity in the entire head of early juveniles upon chemical stimulation. We find that Platynereis uses four types of organs to detect stimuli such as alcohols, esters, amino acids and sugars. Antennae, but not nuchal organs or palps as generally hypothesised in annelids, are the main chemosensory organs. We report chemically-evoked activity in possible downstream brain regions including the mushroom bodies, which are anatomically and molecularly similar to insect mushroom bodies. We conclude that chemosensation is a major sensory modality for marine annelids, and propose early Platynereis juveniles as a model to study annelid chemosensory systems.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=184 HEIGHT=200 SRC=\"FIGDIR/small/391920_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (74K):\norg.highwire.dtl.DTLVardef@4384corg.highwire.dtl.DTLVardef@10c2563org.highwire.dtl.DTLVardef@6a8a32org.highwire.dtl.DTLVardef@96f06c_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2018

Patterning of a telencephalon-like region in the adult brain of amphioxus

The evolutionary origin of the vertebrate telencephalon remains unsolved. A major challenge has been the identification of homologous brain parts in invertebrate chordates. Here we report evidence for a telencephalic region in the brain of amphioxus, the most basally branching invertebrate chordate. This region is characterised, like its vertebrate counterpart, by the combined expression of the telencephalic markers FoxG1, Emx and Lhx2/9. It is located at the anterior neural border and dorsal-ventrally patterned, as in vertebrates, by the antagonistic expression of Pax4/6 and Nkx2.1, and a ventral Hh signal. This part of the brain develops only after metamorphosis via sustained proliferation of neuronal progenitors at the ventricular zone. This is concomitant with a massive expansion of late differentiating neuronal types as revealed by neuropeptide and neurotransmitter profiling. Overall, our results suggest that the adult amphioxus brain shows remarkable similarities to the vertebrate embryonic brain, thus providing a key missing link in understanding the invertebrate-to-vertebrate transition in chordate brain evolution.

evolutionary biology↗

bioRxiv2018

From spiral cleavage to bilateral symmetry: The developmental cell lineage of the annelid brain

The spiral cleavage pattern is characteristic for Spiralia (Lophotrochozoa), a large assembly of marine invertebrates. In most cases, spiral cleavage produces freely swimming, trochophora-type larvae with a simple nervous system that controls ciliary locomotion. These larvae acquire bilateral symmetry, as manifested for example in the larval brain. The transition from the rotational symmetry of spiral cleavage into the bilateral adult body has not yet been understood. Here, we present the developmental cell lineage of the brain of the annelid Platynereis dumerilii from the zygote until the mid-trochophore stage (~30 hpf), in combination with a gene expression atlas for several embryonic and larval stages. Comparison of multiple embryos reveals a highly stereotypical development and an invariant cell lineage of the differentiated cell types. In addition, we observe a fundamental subdivision of the larval brain into a highly proliferative dorsolateral region and an early differentiating ventromedial region that gives rise to the apical nervous system. The transition from rotational to bilateral symmetry progresses gradually from the lateral to the central regions. Strikingly, the spiral-to-bilateral transition does not involve extensive cell migration. Rather, corresponding cells in different spiral quadrants acquire highly divergent identities in line with their bilateral position.

developmental biology↗

bioRxiv2017

Whole-body single-cell sequencing of the Platynereis larva reveals a subdivision into apical versus non-apical tissues

Animal bodies comprise a diverse array of tissues and cells. To characterise cellular identities across an entire body, we have compared the transcriptomes of single cells randomly picked from dissociated whole larvae of the marine annelid Platynereis dumerilii1-4. We identify five transcriptionally distinct groups of differentiated cells that are spatially coherent, as revealed by spatial mapping5. Besides somatic musculature, ciliary bands and midgut, we find a group of cells located at the apical tip of the animal, comprising sensory-peptidergic neurons, and another group composed of non-apical neural and epidermal cells covering the rest of the body. These data establish a basic subdivision of the larval body surface into molecularly defined apical versus non-apical tissues, and support the evolutionary conservation of the apical nervous system as a distinct part of the bilaterian brain6.

evolutionary biology↗