Sense organs in polychaetes (Annelida)

Purschke, Günter

doi:10.1007/s10750-004-4358-5

Cited by 97 publications

(157 citation statements)

References 95 publications

(179 reference statements)

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“…S5 and Movies S6 and S7). Both identified neurons have a sensory dendrite with a cilium and long apical microvillar extensions surrounding the central cilium, characteristic of annelid chemosensory neurons (44) (Fig. 3E).…”

Section: Mip Triggers Larval Settlement In Platynereismentioning

confidence: 94%

Conserved MIP receptor–ligand pair regulates Platynereis larval settlement

Conzelmann

Williams

Tunaru

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

133

216

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Life-cycle transitions connecting larval and juvenile stages in metazoans are orchestrated by neuroendocrine signals including neuropeptides and hormones. In marine invertebrate life cycles, which often consist of planktonic larval and benthic adult stages, settlement of the free-swimming larva to the sea floor in response to environmental cues is a key life cycle transition. Settlement is regulated by a specialized sensory-neurosecretory system, the larval apical organ. The neuroendocrine mechanisms through which the apical organ transduces environmental cues into behavioral responses during settlement are not yet understood. Here we show that myoinhibitory peptide (MIP)/allatostatin-B, a pleiotropic neuropeptide widespread among protostomes, regulates larval settlement in the marine annelid Platynereis dumerilii. MIP is expressed in chemosensory-neurosecretory cells in the annelid larval apical organ and signals to its receptor, an orthologue of the Drosophila sex peptide receptor, expressed in neighboring apical organ cells. We demonstrate by morpholino-mediated knockdown that MIP signals via this receptor to trigger settlement. These results reveal a role for a conserved MIP receptor-ligand pair in regulating marine annelid settlement.M etazoan life cycles show great diversity in larval, juvenile, and adult forms, as well as in the timing and ecological context of the transitions between these forms. In many animal species, neuroendocrine signals involving hormones and neuropeptides regulate life cycle transitions (1-3). Environmental cues are often important instructors of the timing of life cycle transitions (4), and can affect behavioral, physiological, or morphological change via neuroendocrine signaling (5).Marine invertebrate larval settlement is a prime example of the strong link between environmental cues and the timing of life-cycle transitions. Marine invertebrate life cycles often consist of a free-swimming (i.e., pelagic) larval stage that settles to the ocean floor and metamorphoses into a bottom-dwelling (i.e., benthic) juvenile (6-8). In many invertebrate larvae, a pelagicbenthic transition is induced by chemical cues from the environment (9, 10). Larval settlement commonly includes the cessation of swimming and the appearance of substrate exploratory behavior, including crawling on or attachment to the substrate (11-14). In diverse ciliated marine larvae (15), the apical organ, an anterior cluster of larval sensory neurons (16) with a strong neurosecretory character (17-20), has been implicated in the detection of cues for the initiation of larval settlement (21). Although molecular markers of the apical organ have been described (22-24), our knowledge of the neuroendocrine mechanisms with which apical organ cells transmit signals to initiate larval settlement behavior is incomplete.Here, we identify a conserved myoinhibitory peptide (MIP)/ allatostatin-B receptor-ligand pair as a regulator of larval settlement behavior in the marine polychaete annelid Platynereis dumerilii. MIPs are pleiotro...

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Section: Mip Triggers Larval Settlement In Platynereismentioning

confidence: 94%

Conserved MIP receptor–ligand pair regulates Platynereis larval settlement

Conzelmann

Williams

Tunaru

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

133

216

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“…However, it cannot be determined with certainty whether this cell type was mono-or multiciliated. An accessory cilium or vestiges thereof are rather common in PRCs, at least in annelids (Purschke 2005;. Such vestigial cilia occur in larval eyes, e.g.…”

Section: Evolution Of the First Photosensory-motor Axonal Circuitmentioning

confidence: 99%

“…In several species of the polychaete Saccocirrus, the SPC exhibits an apical extension with some rhabdom-like microvilli and vestigial cilia (figure 4a; Eakin et al 1977;Purschke 1992Purschke , 2005. In these species, both SPC and PRC are part of the epidermal layer and the eye cup opens to the exterior.…”

Section: Evolutionary Remnants Of Cellular Multi-functionalitymentioning

confidence: 99%

The ‘division of labour’ model of eye evolution

Arendt

Hausen

Purschke

2009

Phil. Trans. R. Soc. B

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The 'division of labour' model of eye evolution is elaborated here. We propose that the evolution of complex, multicellular animal eyes started from a single, multi-functional cell type that existed in metazoan ancestors. This ancient cell type had at least three functions: light detection via a photoreceptive organelle, light shading by means of pigment granules and steering through locomotor cilia. Located around the circumference of swimming ciliated zooplankton larvae, these ancient cells were able to mediate phototaxis in the absence of a nervous system. This precursor then diversified, by cell-type functional segregation, into sister cell types that specialized in different subfunctions, evolving into separate photoreceptor cells, shading pigment cells (SPCs) or ciliated locomotor cells. Photoreceptor sensory cells and ciliated locomotor cells remained interconnected by newly evolving axons, giving rise to an early axonal circuit. In some evolutionary lines, residual functions prevailed in the specialized cell types that mirror the ancient multi-functionality, for instance, SPCs expressing an opsin as well as possessing rhabdomer-like microvilli, vestigial cilia and an axon. Functional segregation of cell types in eye evolution also explains the emergence of more elaborate photosensory-motor axonal circuits, with interneurons relaying the visual information.

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“…Rouse and Pleijel (2001) proposed a possible homology of this structure with the lateral organs occurring in the same position in other taxa such as Opheliidae, Orbiniidae and Paraonidae within Scolecida and also in Canalipalpata (Spionidae and Pectinariidae) and Aciculata (Syllidae, Eunicidae and Amphinomidae) (Purschke 2005).…”

Section: Discussionmentioning

confidence: 87%

A revision of the deep-sea genus Axiokebuita Pocklington and Fournier, 1987 (Annelida: Scalibregmatidae)

Parapar

Gambi

Rouse

2011

Italian Journal of Zoology

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The deep-sea genus Axiokebuita (Annelida, Scalibregmatidae) has hitherto been considered to contain two species, Axiokebuita minuta (Hartman, 1967) and Axiokebuita millsi Pocklington and Fournier, 1987, each rarely recorded in the literature and both supposedly having bipolar distributions. From the study of some types, other museum collection material, plus newly collected specimens from the slope depths of the Bellingshausen Sea and off the Antarctic Peninsula (Antarctica), Iceland and Iberian Peninsula, as well as from hydrothermal vents of the southeastern Pacific Ocean, the taxonomic history of the genus is revisited. Based on the results of this study, the features traditionally used to distinguish between the two species are actually the same in both. Therefore, A. millsi is proposed to be synonymised with A. minuta, which is redescribed and considered the only valid species of the genus, leaving Axiokebuita monotypic. Two previously unnoticed body sensory structures, i.e. a ciliated neck organ and a prostomial depression, were observed under scanning electron microscopy.

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Sense organs in polychaetes (Annelida)

Cited by 97 publications

References 95 publications

Conserved MIP receptor–ligand pair regulates Platynereis larval settlement

Conserved MIP receptor–ligand pair regulates Platynereis larval settlement

The ‘division of labour’ model of eye evolution

A revision of the deep-sea genus Axiokebuita Pocklington and Fournier, 1987 (Annelida: Scalibregmatidae)

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