The stabilization of locust cuticle

Cuticle from the metathoracic femur of adult locusts (Locusta migratoria) is characterized with respect to changes in water content and in protein extractability during maturation. The swelling behaviour and extractability of fully-sclerotized cuticle are compared to those of chemically-modified, unsclerotized cuticle.It is concluded that although dehydration may contribute to the stabilization of cuticle, it cannot account for the observed differences. The properties of mature cuticle can best be explained by the assumption that covalent cross-links are present between protein molecules.     

New trace fossil evidence for eurypterid swimming behaviour

We describe a recently discovered trace fossil from a eurypterid Konservat‐Lagerstätte in the upper Silurian Tonoloway Formation of Pennsylvania, and formally describe contemporaneous traces from the Williamsville Formation Lagerstätte of Ontario. The traces from both localities are assigned here to Arcuites bertiensis igen. et isp. nov. Based on comparisons with previously described eurypterid trackways, neoichnological experiments, and the co‐occurrence with eurypterid remains, Arcuites is interpreted as having been made by the swimming leg (sixth prosomal appendage) of swimming juvenile to adult eurypteroid eurypterids, and represents the first unambiguous trace fossil evidence for eurypterid swimming behaviour. The morphology of Arcuites indicates that eurypteroid eurypterids swam using drag‐based rowing, whereby the animal propelled itself forward by moving its oar blade‐like swimming paddles in an in‐phase backstroke. Arcuites morphology also indicates that the eurypteroid swimming appendage had a greater degree of movement than was previously suggested, and a revised rowing model is proposed. Differences in the abundance of A. bertiensis in the Tonoloway and Williamsville formations suggest a bathymetric control on eurypterid swimming behaviour and trace production. The association of Arcuites with eurypterid body fossils in both units indicates that these Lagerstätten were autochthonous assemblages and provides additional evidence for eurypterid inhabitation of shallow subtidal marine environments in the late Silurian.     

The pupal cuticle of Drosophila: differential ultrastructural immunolocalization of cuticle proteins

Precise ultrastructural localization of Drosophila melanogaster pupal cuticle proteins (PCPs) was achieved by the immunogold labeling of frozen thin sections. PCPs were found in lamellate cuticle and intracellular vesicles but, curiously, were absent from the assembly zone of the cuticle. Antibodies that distinguish between the two classes of PCPs--low molecular weight (L-PCPs) and high molecular weight (H-PCPs)--revealed that the morphologically distinct outer lamellae contained L-PCPs and the inner lamellae contained H-PCPs. The sharp boundary between these two antigenic domains coincides with the transition from the outer to the inner lamellae, which in turn is correlated with the cessation of L-PCP synthesis and the initiation of H-PCP synthesis in response to 20-hydroxyecdysone (Doctor, J., D. Fristrom, and J.W. Fristrom, 1985, J. Cell Biol. 101:189-200). Hence, differences in protein composition are associated with differences in lamellar morphology.     

The ultrastructure of the cuticle of Nematoda

 The ultrastructure of the body cuticle in species of six of seven representative genera of Stilbonematinae (Eubostrichus, Catanema, Laxus, Robbea, Leptonemella, and Stilbonema) was investigated using SEM and TEM techniques. Additionally, one species of Spirinia (Spiriniinae) and one of Desmodora (Desmodorinae) were studied for outgroup comparison. The body cuticle of all investigated stilbonematids shows a consistent pattern composed of specific elements in a characteristic arrangement to each other. This pattern does not occur in Stilbonematinae alone, but also in Desmodorinae and Spiriniinae. Furthermore, a comparison within the Desmodorida reveals that this cuticular pattern apparently is present in the cuticle of representatives of Monoposthiidae, Epsilonematidae, and Draconematidae. The present results lead to the following conclusions: (1) the cuticle of Stilbonematinae contains no autapomorphic characters for this taxon, (2) there is a common cuticular pattern within the Desmodorida, and (3) this pattern is an autapomorphic character for the order Desmodorida. Accepted: 4 February 1996     

The constituent cutin acids of cranbury cuticle

Purified cutin from cranberry (Vaccinium macrocarpon, var. Howes) skin was selectively degraded, and the cutin acids, as methyl esters, separated by TLC into seven classes including monobasic acids, dibasic acids, monohydroxy monobasic acids, monohydroxy epoxymonobasic acids, vic-dihydroxy dibasic acids, dihydroxy monobasic acids and trihydroxy monobasic acids. Of the 41 components identified in cranberry cutin by GLC and MS analysis, 18-hydroxyoctadec-cis-9-enoic acid (9·4%), 18-hydroxy-cis-9,10-epoxyoctadecanoic acid (7·5%), 10,16-dihydroxyhexadecanoic acid (16·7%) and threo-9,10,18-trihydroxyoctadecanoic acid (43·7%) were shown to be the major constituents.     

Structure and expression of a Manduca sexta larval cuticle gene homologous to Drosophila cuticle genes

A genomic clone was isolated from the tobacco hornworm, Manduca sexta, by virtue of its similarity to a Drosophila larval cuticle gene. RNA analysis shows that this clone, B311, is expressed at times appropriate for a larval cuticle gene. Hybrid-selection experiments using B311 DNA show that it encodes a 14 x 10(3) Mr protein, LCP-14, which is precipitated by an antiserum to Manduca larval cuticle. We have sequenced both genomic and cDNA clones for the LCP-14 gene. A conceptual translation of the cDNA sequence shows that the LCP-14 protein is similar not only to another Manduca cuticle protein, but also to Drosophila, Sarcophaga and Hyalophora cecropia cuticle proteins. Since these proteins are found in flexible cuticle and have similar sequences, we conclude they are encoded by homologous genes.     

The role of cuticle in fruit shelf-life

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The cuticle of the Buxbaumia viridis sporophyte

The sporophytes of Buxbaumia viridis are covered with a cuticle-like skin, which is peeling off when the capsules are ripe. Scanning electron microscopy (SEM) analysis showed that the supposed peeling of the cuticle of ripe capsules is not restricted to the cuticle, but to the complete epidermis. Additionally the SEM investigations showed that the capsule epidermis is covered by epicuticular wax crystals in different morphologies. Wax crystal morphologies indicate the presence of massive wax layers with small embedded and superimposed platelets and granules on top. For bryophytes such wax crystals were so far reported only from the Polytrichales, but they are common wax types of various groups of several phanerogams. Based on these micro-morphological markers the phylogenetic relationship between the cuticles of moss sporophytes and tracheophytes is discussed here.     

The ultrastructure of the cuticle of Nematoda. II. The cephalic cuticle of Stilbonematinae (Adenophorea,Desmodoridae)

Summary  The ultrastructure of the cephalic cuticle of 6 of 7 representative genera of Stilbonematinae (Eubostrichus, Catanema, Laxus, Robbea, Leptonemella, Stilbonema) is investigated using SEM and TEM techniques. Additionally, one species of Spirinia (Spiriniinae) and one of Desmodora (Desmodorinae) were studied for outgroup comparison. Most of the studied species show modifications of the cephalic cuticle. Furthermore, at least four different pathways have been developed to reinforce the head within Stilbonematinae. Species with a coarsely annulated somatic cuticle (Leptonemella sp., Stilbonema majum, and Desmodora ovigera) developed a rigid, non-annulated cephalic capsule by modifying the main constructing element of the median zone, the ’’ring body.’’ In faintly annulated Laxus oneistus, the annulated cephalic capsule results from a newly inserted ’’block layer’’ between the median and basal zone. The non-annulated cephalic capsule of Robbea sp. is formed by both the block layer and the ring body element. The annulated capsule of Catanema sp. stems from a doubled number of fiber layers within the basal zone. In Spirinia sp., only the amphidial region is strengthened in what could be termed an amphidial shield. All forms with cephalic capsules show mechanisms to keep the oral region pliable. Only Eubostrichus topiarius lacks a reinforcement of the cephalic cuticle. A comparison with the literature is made to elucidate corresponding structures within the cephalic capsules of representatives of Desmodorida. It is demonstrated that the presence of a cephalic cuticle is of no systematic value above the genus level. Accepted: 3 March 1996     

The surface morphology of locust hindgut cuticle*

The surface architecture of hindgut cuticle in Locusta migratoria is described. Infundibulate pores are present in the midrectal pads, the ileum and the posterior rectum. It is suggested that they lead to canals traversing the cuticle. Larger occluded crater-like pores are present on the posterior rectal pads and may be glandular. The cuticle of the ileum and colon is invested with numerous spikes pointing backwards, and the interpad region of the rectum with upright spikes pointing inwards. These spikes probably serve to direct the faeces backwards from the ileum and colon, and to impale the faecal pellet during dehydration in the rectum.     

The incorporation of precursors into Drosophila larval cuticle

Incorporation of tritiated leucine, tyrosine and glucosamine into the integument of larval Drosophila melanogaster was followed by electron-microscope autoradiography. Tritiated leucine, tyrosine, and glucosamine were incorporated into the endocuticle by apposition, giving rise to a distinct band of label in the endocuticle at a level which depended on the time between labelling and fixation. The labelled amino acids, but not glucosamine, were also detected in the epicuticle and both above and below the distinct labelled band in the endocuticle. The results indicate that the epicuticle grows within the third instar by intussusception of new materials which are transported from the epidermal cells through the endocuticle to the epicuticle. Breakdown of cuticle which was radioactively labelled by feeding larvae tritiated precursors was also followed by autoradiography. The results indicate that the breakdown products from the old cuticle may be reutilized in the synthesis of new cuticle.     

The development of the cuticle in Phormium tenax

Summary As seen in the scanning electron microscope the surface wax of leaves of Phormium tenax L. consists of vertical, plate-like crystals. These increase in size and number and undergo a change in form during development. The abaxial surface has a dense covering of wax crystals, but none are present on the ridges over vascular tissues. Numerous papillae are found between these ridges in later stages of development. On the adaxial surface both wax crystals and papillae are present only around infrequent stomata.When viewed in section normal to the leaf surface the cuticle is first apparent as a thin, lamellate layer. Another layer containing a reticulum of electrondense material increases in thickness beneath the lamellae during development. This layer eventually becomes the most extensive component of the cuticle. Both the adaxial and abaxial cuticles show a similar pattern of development.