The Crustacean Integument

Dillaman, Richard M.; Roer, Robert D.; Shafer, Thomas H.

doi:10.1093/acprof:osobl/9780195398038.003.0005

Cited by 21 publications

(26 citation statements)

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“…It is a combination of a thin outer layer (exocuticle) and thick inner layer (endocuticle). The exo- and endocuticle have a lamellar structure: the exocuticle lamellae are always thinner than the endocuticle lamellae (Dillaman et al . 2013).…”

Section: Discussionmentioning

confidence: 99%

Cuticle and cuticular sensilla in Agnostina

Naimark

Chaika

2022

Preprint

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The microstructure of the cuticle of several Agnostina species is described. For the first time, it has been shown that their cuticle consists of three layers: thick outer and transitional layers and a thin inner layer. The layers are made up of stacks of laminae: the laminae in the outer layer are thicker than in the transitional and inner ones. The evolution of the agnostoid cuticle proceeded, apparently, in the direction of decreasing the thickness of the inner layer which in contrast to all other arthropods, is thinner than the outer layer. Apparently, the inner layer was mineralized to a lesser extent than the outer one. In the structure of the cuticle, Agnostina are close to horseshoe crabs and trilobites. On the outer and inner layers, a set of sensilla was revealed; they can be attributed to trichoid, campaniform, and digitiform sensilla (with mechanoreceptor function) and celoconic sensilla (with chemoreceptor function). Also, unique sensorial ensembles were found on cephalons and pygidia; the function of the former is probably mechanosensorial, and the purpose of the latter cannot be assumed on this material.

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Section: Discussionmentioning

confidence: 99%

Cuticle and cuticular sensilla in Agnostina

Naimark

Chaika

2022

Preprint

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“…Despite our use of the word "mold" above, we are not ready to propose that the "ghost" actually guides and determines the 4.2 | Composition and anatomical identity of the "ghost" SEM shows that the "ghost" in at least one large "species" of Facetotecta consists of a thin layer of matted or anastomosing fibers, the chemical composition of which remains unknown. It is not composed of typical arthropod cuticle, which consists of a matrix of fibrils of chitin and proteins in multiple, differently oriented parallel layers, not as a loose meshwork (Dillaman, Roer, Shafer, & Modla, 2013;Roer, Abehsera, & Sagi, 2015). If it is not a cuticle, it cannot be an endoskeleton, even though the anterior "struts" appear somewhat apodeme-like, being attached to what appear to be a pair of anteroventral invaginations of the trunk's outer cuticle.…”

Section: Functional Role Of the "Ghost"mentioning

confidence: 99%

“…Apoptosis is generally a "clean" process, in that the remnants of dead cells are ingested by phagocytes (e.g., Deming & Kornbluth, 2010), and should not leave a residue. A different process, common to arthropods in general, is the dissolution by enzymes of the inner layers of the old cuticle in order for their components to be resorbed and reused (Dillaman et al, 2013;Roer et al, 2015). If this dissolution process is incomplete, some residue might remain, lining the newly formed ecdysial space.…”

Section: Functional Role Of the "Ghost"mentioning

confidence: 99%

A new internal structure of nauplius larvae: A “ghostly” support sling for cypris y left within the exuviae of nauplius y after metamorphosis (Crustacea: Thecostraca: Facetotecta)

Grygier

Høeg

Dreyer

et al. 2019

Journal of Morphology

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Facetotecta, or crustacean “y‐larvae,” occur in all the world's oceans although the adult forms remain completely unknown. At the metamorphic molt from the last naupliar instar to the terminal cypris larval stage a free carapace, six pairs of natatory thoracopods, and a segmented thorax and abdomen all develop anew. Unlike in earlier molts, the cephalic shield and the so‐called “faciotruncal integument” usually remain together at this last naupliar molt, and the posterior “trunk” portion of the exuviae, while hollow, is not empty. In mounted preparations examined by phase contrast or differential interference contrast (DIC) microscopy, a ghost‐like image of part of the cypris thorax, particularly the thoracopods and even their setae, is commonly visible inside the naupliar exuviae, and may be universally present in the Facetotecta. To investigate this “ghost,” we used DIC and digital photographic stacking, and also scanning electron microscopy, on slide or stub‐mounted final naupliar exuviae of an assortment of undescribed species of Facetotecta that had been reared from planktonic lecithotropic nauplii to the cypris stage at Sesoko Island, Okinawa, Japan, and at Keelung and Green Island, Taiwan. These techniques showed that the “ghost” is a delicate, three‐dimensional, fibrous structure, essentially a sling‐like mold or matrix with struts attached to the outer cuticle and pairs of deep pockets that previously held the thoracopods of the developing cypris y. Whether it is endoskeletal in nature, the (partial) exuvia of an additional instar, remnants of apoptosis, or something else is currently unknown. Nothing similar has been reported in other thecostracans, or in other crustaceans that undergo a similarly abrupt metamorphosis at the last naupliar molt.

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“…3d). 37,38 In heavily mineralized crustaceans such as crab and lobster, such nanofibers have been described. 31,39 Nanofibers have been reported to be between 10–100 nm thick and 1–4 μm long.…”

Section: Introductionmentioning

confidence: 99%