Anterior sense organs in Sabellaria alveolata (Annelida, Sedentaria, Spionida) with special reference to ultrastructure of photoreceptor elements presumably involved in shadow reflex

Meyer, Christian; Faroni-Perez, Larisse; Purschke, Günter

doi:10.1007/s00435-018-0422-y

Cited by 4 publications

(20 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Beyond the sabellids and serpulids, a number of other polychaetes display a shadow response, including sabellariids, which employ a similar tube-dwelling lifestyle, as well as the semierrant Platynereis dumerilii. Interestingly, all of these shadowresponse systems seem to be mediated by different photoreceptor systems: C-opsins in ciliary photoreceptors in sabellids and serpulids (Bok et al, 2017a,b), rhabdomeric photoreceptors with unknown opsins in sabellariids (Meyer et al, 2019;Helm et al, 2018), and a tetraopsin in unknown cirral photoreceptors of P. dumerilii (Ayers et al, 2018). Did all of these shadow responses evolve independently, and do they all feed into a similar giant axon startle response pathway?…”

Section: The Evolution and Development Of The Radiolar Eye Visual Systemmentioning

confidence: 99%

Photoresponses in the radiolar eyes of the fan worm, Acromegalomma vesiculosum (Montagu)

Bok

Nilsson

Garm

2019

Journal of Experimental Biology

View full text Add to dashboard Cite

Fan worms (Annelida: Sabellidae) possess compound eyes and other photoreceptors on their radiolar feeding tentacles. These eyes putatively serve as an alarm system that alerts the worm to encroaching threats, eliciting a rapid defensive retraction into their protective tube. The structure and independent evolutionary derivation of these radiolar eyes make them a fascinating target for exploring the emergence of new sensory systems and visually guided behaviours. However, little is known about their physiology and how this impacts their function. Here, we present electroretinogram recordings from the radiolar eyes of the fan worm Acromegalomma vesiculosum. We examine their spectral sensitivity along with their dynamic range and temporal resolution. Our results show that they possess one class of photoreceptors with a single visual pigment peaking in the blue-green part of the spectrum around 510 nm, which matches the dominant wavelengths in their shallow coastal habitats. We found the eyes to have a rather high temporal resolution with a critical flicker fusion frequency around 35 Hz. The high temporal resolution of this response is ideally suited for detecting rapidly moving predators but also necessitates downstream signal processing to filter out caustic wave flicker. This study provides a fundamental understanding of how these eyes function. Furthermore, these findings emphasise a set of dynamic physiological principles that are well suited for governing a multi-eyed startle response in coastal aquatic habitats.

show abstract

Section: The Evolution and Development Of The Radiolar Eye Visual Systemmentioning

confidence: 99%

Photoresponses in the radiolar eyes of the fan worm, Acromegalomma vesiculosum (Montagu)

Bok

Nilsson

Garm

2019

Journal of Experimental Biology

View full text Add to dashboard Cite

show abstract

“…The animals exhibit heteronomous segmentation, and their highly modi ed anterior end forms the operculum representing a multifunctional structure [3][4][5]. Their body may be subdivided into operculum, thorax, parathorax, abdomen and caudal region [2][3][4]6]. Sometimes the thorax is included in the operculum proper.…”

Section: Introductionmentioning

confidence: 99%

“…This part of the operculum bears eyes in addition to the cerebral eyes in many species [2,5,9]. Very likely, these eyes are essential for the escape or shadow re ex when the animals withdraw into their tubes [6].Although the external morphology of the group is well known, to date, Sabellariidae have seldom been studied by transmission electron microscopy (TEM). These previous investigations include general observations on larvae and metamorphosis [10,11], oogenesis and spermatogenesis [12,13] as well as some more preliminary data on the tentacular laments [14].…”

mentioning

confidence: 99%

“…These previous investigations include general observations on larvae and metamorphosis [10,11], oogenesis and spermatogenesis [12,13] as well as some more preliminary data on the tentacular laments [14]. Among their sensory structures, only the palps (termed tentacles) have been studied thus far in late larvae of Phragmatopoma californica [15,16].Recent investigations on the sensory organs in Sabellaraiidae focused on the thus far underestimated importance of the median organ, neglecting, however, the possible sensory role of the other appendages [2,5,6,9].In Sabellariidae, data on the branchiae are only available on the light microscopic level [17][18][19]. However, ultrastructural observations exist for several polychaete species [20][21].…”

mentioning

confidence: 99%

“…Recent investigations on the sensory organs in Sabellaraiidae focused on the thus far underestimated importance of the median organ, neglecting, however, the possible sensory role of the other appendages [2,5,6,9].…”

mentioning

confidence: 99%

See 2 more Smart Citations

Ultrastructure and functional morphology of the appendages in the reef-building sedentary polychaete Sabellaria alveolata (Annelida, Sedentaria, Sabellida)

Meyer¹,

André²,

Purschke³

2021

BMC Zool

Self Cite

View full text Add to dashboard Cite

Background The sedentary polychaete Sabellaria alveolata, the sandcastle or honeycomb worm, possesses four different kinds of appendages besides the parapodia: opercular papillae, tentacular filaments, palps, and branchiae. It exhibits a highly specialized anterior end, the operculum, formed by the prostomium, peristomium, and two anterior segments. The operculum comprises opercular papillae, tentacular filaments, and palps. Paired branchiae are present from the second thoracic chaetiger onwards on the posteriorly following segments except for the last ones. Ultrastructural data on these appendages are either scanty, incomplete, or even lacking in Sabellariidae. In order to analyze their functional morphology, to bridge the data gap, and providing data for future phylogenetic and evolutionary analyses, we investigated the appendages of S. alveolata by applying light microscopy, confocal laser scanning microscopy, scanning, and transmission electron microscopy. Results In S. alveolata the entire body is covered by a thin cuticle characterized by the absence of layers of parallel collagen fibers with no differentiation between the various body regions including the branchiae. The opercular papillae bear numerous tufts of receptor cells and lack motile cilia. The tentacular filaments show a distinctive pattern of motile cilia. Their most conspicuous morphological feature is a cell-free cartilaginous endoskeletal structure enclosed by ECM. Besides musculature the filaments include a single coelomic cavity but blood vessels are absent. The palps are ciliated and possess two coelomic cavities and a single blind-ending internal blood vessel. Besides external ciliation and receptor cells, the coelomate branchiae are highly vascularized and equipped with numerous blood spaces extending deep between the epidermal cells resulting in low diffusion distances. Conclusions All appendages, including the branchiae, bear receptor cells and, as such, are sensory. The opercular papillae resemble typical parapodial cirri. In contrast, the tentacular filaments have a triple function: sensing, collecting and transporting particles. A similarity to branchiae can be excluded. The palps are typical grooved palps. A revised classification of polychaete branchiae is suggested; thereby, the branchiae of S. alveolata belong to the most common type comprising coelom, musculature, and blood vessels. The results indicate that diffusion distances between blood and environment have been underestimated in many cases.

show abstract

Sensory cells and the organization of the peripheral nervous system of the siboglinid Oligobrachia haakonmosbiensis Smirnov, 2000

Зайцева¹,

Смирнов²,

Starunova³

et al. 2022

BMC Zool

View full text Add to dashboard Cite

Background The nervous system of siboglinids has been studied mainly in Osedax and some Vestimentifera, while data in Frenulata – one of the four pogonophoran main branches – is still fragmentary. In most of the studies, the focus is almost always on the central nervous system, while the peripheral nervous system has traditionally received little attention. In contrast to other annelids, the structure and diversity of sensory structures in siboglinids are still quite undescribed. Meanwhile, the peripheral nervous system, as well as sensory elements, are extremely evolutionarily labile, and information about their organization is of high importance to understand lifestyles and behavior as well as main trends that lead siboglinids to their peculiar organization. Results The structure of the peripheric nervous system, sensory elements, and neuromuscular relationships of Oligobrachia haakonmosbiensis were studied using both scanning electron and confocal laser microscopy. A significant number of monociliary sensory cells, as well as sensory complexes located diffusely in the epithelium of the whole body were revealed. The latter include the cephalic tentacles, sensory cells accumulations along the dorsal furrow and ciliary band, areas of the openings of the tubiparous glands, and papillae. The oval ciliary spot located on the cephalic lobe at the base of the tentacles can also be regarded as a sensory organ. Most of the detected sensory cells show immunoreactivity to substance P and/or acetylated α-tubulin. FMRFamide- and serotonin-like immunoreactivity are manifested by neurons that mainly innervate tentacles, muscles, body wall epithelium, skin glands, tubiparous glands, and papillae. In the larva of O. haakonmosbiensis, monociliary sensory elements were revealed in the region of the apical organ, along the body, and on the pygidium. Conclusions The diversity of sensory structures in O. haakonmosbiensis comprises epidermal solitary sensory cells, sensory spots around tubiparous glands openings, and putative sensory organs such as cephalic tentacles, an oval ciliary spot on the cephalic lobe, the dorsal furrow, and papillae. Sensory structures associated with papillae and tubiparous glands play presumable mechanosensory functions and are associated with regulation of tube building as well as anchorage of the worm inside the tube. Sensory structures of the dorsal furrow are presumably engaged in the regulation of reproductive behavior. An overall low level of morphological differentiation of O. haakonmosbiensis peripheral nervous system is not typical even for annelids with the intraepithelial nervous system. This can be considered as a plesiomorphic feature of its peripheral plexus’s organization, or as evidence for the neotenic origin of Siboglinidae.

show abstract

Anterior sense organs in Sabellaria alveolata (Annelida, Sedentaria, Spionida) with special reference to ultrastructure of photoreceptor elements presumably involved in shadow reflex

Cited by 4 publications

References 45 publications

Photoresponses in the radiolar eyes of the fan worm, Acromegalomma vesiculosum (Montagu)

Photoresponses in the radiolar eyes of the fan worm, Acromegalomma vesiculosum (Montagu)

Ultrastructure and functional morphology of the appendages in the reef-building sedentary polychaete Sabellaria alveolata (Annelida, Sedentaria, Sabellida)

Sensory cells and the organization of the peripheral nervous system of the siboglinid Oligobrachia haakonmosbiensis Smirnov, 2000

Contact Info

Product

Resources

About