Fine Structure of the ‘Slit Organs’ of the Pycnogonid <i>Anoplodactylus petiolatus</i> (Anoplodactylidae)

Melzer, Roland R.; Heβ, Martin; Dunkel, Christine; Ludwig, Peter; Smola, Ulrich

doi:10.1111/j.1463-6395.1996.tb01261.x

Cited by 7 publications

(7 citation statements)

References 18 publications

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“…Slit‐like glands were found in many arthropods (Martens, ), including a single report from adult sea spiders Anoplodactylus petiolatus KRØYER, 1844 (Melzer, Heβ, Dunkel, Ludwig, & Smola, ). Our ultrastructural data agrees reasonably well with those reported by Melzer et al ().…”

Section: Discussionmentioning

confidence: 99%

Oligomeric larvae of the pycnogonids revisited

Alexeeva

Богомолова

Tamberg

et al. 2017

Journal of Morphology

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Organization and ultrastructure of the protonymphon larva were never adequately described, despite it being the common larval type of the enigmatic sea spiders and the only example of oligosegmented life stage among recent chelicerates. We have made a comprehensive examination of the newly hatched free-living protonymphons of Nymphon brevirostre using SEM, TEM, light, and confocal microscopy. Although fairly typical in their broad characters, protonymphon larvae have a number of unique and unexpected traits. Body cavity, already present at this stage, is lined with extracellular matrix and thus is conclusively identified as primary body cavity. Central nervous system includes four postocular neuromeres arranged in three ganglia: supraesophageal, subesophageal, and the first ganglion of the ventral nerve cord. Examination of the sensory organs revealed unusually organized eyes, mechanoreceptors, and chemoreceptors. We have uncovered a mixed sensory-secretory nature of chelar glands and proposed possible modalities of its receptory part. We gave first descriptions of the complex ultrastructure of three secretory organs (spinning glands, slit-like organs, proboscis glands) and hypothesized on their mode of functioning. Comparisons with another oligomeric larva, for example, nauplius, revealed discrepancies in the segmentation of these animals. Although both larvae are externally unsegmented and bear three pairs of homologous appendages, the protonymphon body includes a fourth segment of the prospective walking legs which is absent in nauplius.

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Section: Discussionmentioning

confidence: 99%

Oligomeric larvae of the pycnogonids revisited

Alexeeva

Богомолова

Tamberg

et al. 2017

Journal of Morphology

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“…Similarly, removing waxes gave inconclusive results. There was some evidence that waxes (or chemicals present in those waxes; see Fahrenbach, 1994, andMelzer et al, 1996) on pycnogonids prevent epibiont attachment ( Fig. 4; paired t-test), but our nonparametric analysis did not support this conclusion.…”

Section: Discussionmentioning

confidence: 70%

No Effects and No Control of Epibionts in Two Species of Temperate Pycnogonids

Shishido

Moran

Tobalske

et al. 2016

The Biological Bulletin

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Essentially all surfaces of marine plants and animals host epibionts. These organisms may harm their hosts in a number of ways, including impeding gas exchange or increasing the costs of locomotion. Epibionts can also be beneficial. For example, they may camouflage their hosts, and photosynthetic epibionts can produce oxygen. In general, however, the costs of epibionts appear to outweigh their benefits. Many organisms, therefore, shed epibionts by grooming, molting, or preventing them from initially attaching, using surface waxes and cuticular structures. In this study, we examined how epibionts affect local oxygen supply to temperate species of pycnogonids (sea spiders). We also tested the effectiveness of different methods that pycnogonids may use to control epibionts (grooming, cuticle wettability, and cuticular waxes). In two temperate species: Achelia chelata and Achelia gracilipes, epibionts consisted primarily of algae and diatoms, formed layers approximately 0.25-mm thick, and they colonized at least 75% of available surface area. We used microelectrodes to measure oxygen levels in and under the layers of epibionts. In bright light, these organisms produced high levels of oxygen; in the dark, they had no negative effect on local oxygen supply. We tested mechanisms of control of epibionts by pycnogonids in three ways: disabling their ovigers to prevent grooming, extracting wax layers from the cuticle, and measuring the wettability of the cuticle; however, none of these experiments affected epibiont coverage. These findings indicate that in temperate environments, epibionts are not costly to pycnogonids and, in some circumstances, they may be beneficial.

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“…Often they are found close to opening valves of cuticular glands (slit organs; see Fahrenbach (); Melzer et al. (); Thiry, Compère, Goffinet, and Bussers (); Tomaschko ()), but statistical significance has to be proved.…”

Section: The Ciliary or Sensillar Sense Organs—mechanoreception And Morementioning

confidence: 99%

“…On the dorsal surface of the body alone, one finds more than 250 setae of bifurcate shape. Often they are found close to opening valves of cuticular glands (slit organs; see Fahrenbach (1994); Melzer et al (1996);Thiry, Compère, Goffinet, and Bussers (1995); Tomaschko (1995)), but statistical significance has to be proved.…”

Section: "Gabelborsten"mentioning

confidence: 99%

“…In the present report, we have therefore not only summarized published knowledge, but also present original data from, for example, ultrathin sections we collected in the past two decades as by‐products of our studies on pycnogonid eyes (Heß et al., ; Lehmann et al., ; Lehmann, Heß, Wanner, et al. ) and glands (Melzer, Heβ, Dunkel, Ludwig, & Smola, ).…”

Section: Introductionmentioning

confidence: 99%

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Sense organs in Pycnogonida: A review

2017

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The Pycnogonida or sea spiders are exclusively marine invertebrates, numbering about 1,300 described species worldwide. Given their remarkable position in phylogeny as basal chelicerates or even basal euarthropods, the structure of their sense organs can reveal important characters, which—in a comparative framework—provide arguments to phylogenetic discussions and help to develop scenarios of evolutionary transformations. This review summarizes current knowledge and presents new original data on the sense organs in pycnogonids, that is, the eyes, the lateral sense organs and the ciliary or sensillar sense organs. Except for the eyes, there are not many detailed studies available. The ultrastructure of the R‐cells of the four eyes located on the ocular tubercle is described as “pseudoinverted”. The eyes are innervated to two visual neuropils located in the protocerebrum. The features of the lateral sense organ, also located on the ocular tubercle, are hitherto not conclusively resolved, a chemo‐ or thermoreceptive function is suggested. Finally, an overview of the various ciliary or sensillar sense organs distributed all over the body is given and the fine structure of branched setae is shown for the first time. The morphology of the sense organs of pycnogonids is compared with that of other arthropod taxa and assessed against the background of current theories of arthropod evolution.

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Fine Structure of the ‘Slit Organs’ of the Pycnogonid Anoplodactylus petiolatus (Anoplodactylidae)

Abstract: Melzer, R.R., Hep, M., Dunkel, C.

Cited by 7 publications

References 18 publications

Oligomeric larvae of the pycnogonids revisited

Oligomeric larvae of the pycnogonids revisited

No Effects and No Control of Epibionts in Two Species of Temperate Pycnogonids

Sense organs in Pycnogonida: A review

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