The wax glands and wax secretion of Matsucoccus matsumurae at different development stages

In this paper, the wax secretions and wax glands of Matsucoccus matsumurae (Kuwana) at different instars were investigated using light microscopy, scanning electron microscopy and transmission electron microscopy. The first and second instar nymphs were found to secrete wax filaments via the wax glands located in the atrium of the abdominal spiracles, which have a center open and a series of outer ring pores. The wax gland of the abdominal spiracle possesses a large central wax reservoir and several wax-secreting cells. Third-instar male nymphs secreted long and translucent wax filaments from monolocular, biolocular, trilocular and quadrilocular pores to form twine into cocoons. The adult male secreted long and straight wax filaments in bundles from a group of 18–19 wax-secreting tubular ducts on the abdominal segment VII. Each tube duct contained five or six wax pores. The adult female has dorsal cicatrices distributed in rows, many biolocular tubular ducts and multilocular disc pores with 8–12 loculi secreting wax filaments that form the egg sac, and a rare type wax pores with 10 loculi secreting 10 straight, hollow wax filaments. The ultrastructure and cytological characteristics of the wax glands include wax-secreting cells with a large nucleus, multiple mitochondria and several rough endoplasmic reticulum. The functions of the wax glands and wax secretions are discussed.     

The positional sterile (ps) mutation affects cuticular transpiration and wax biosynthesis of tomato fruits

Cuticular waxes are known to play a pivotal role in limiting transpirational water loss across primary plant surfaces. The astomatous tomato fruit is an ideal model system that permits the functional characterization of intact cuticular membranes and therefore allows direct correlation of their permeance for water with their qualitative and quantitative composition. The recessive positional sterile (ps) mutation, which occurred spontaneously in tomato (Solanum lycopersicum L.), is characterized by floral organ fusion and positional sterility. Because of a striking phenotypical similarity with the lecer6 wax mutant of tomato, which is defective in very-long-chain fatty acid elongation, ps mutant fruits were analyzed for their cuticular wax and cutin composition. We also examined their cuticular permeance for water following the developmental course of fruit ripening. Wild type and ps mutant fruits showed considerable differences in their cuticular permeance for water, while exhibiting similar quantitative wax accumulation. The ps mutant fruits showed a five- to eightfold increase in water loss per unit time and surface area when compared to the corresponding wild type fruits. The cuticular waxes of ps mutant fruits were characterized by an almost complete absence of n-alkanes and aldehydes, with a concomitant increase in triterpenoids and sterol derivatives. We also noted the occurrence of alkyl esters not present in the wild type. Quantitative and qualitative cutin monomer composition remained largely unaffected. The significant differences in the cuticular wax composition of ps mutant fruits induced a distinct increase of cuticular water permeance. The fruit wax compositional phenotype indicates the ps mutation is responsible for effectively blocking the decarbonylation pathway of wax biosynthesis in epidermal cells of tomato fruits.     

<Emphasis Type="Italic">Empruthotrema longipenis</Emphasis> n. sp. (Monogenoidea: Monocotylidae: Merizocotylinae) from the olfactory sacs of the smooth butterfly ray <Emphasis Type="Italic">Gymnura micrura</Emphasis> (Bloch &amp; Schneider) (Myliobatiformes: Gymnuridae) in the Gulf of Mexico

A new species of Empruthotrema Johnston & Tiegs, 1922 is described based on specimens collected from the olfactory sacs of smooth butterfly rays Gymnura micrura (Bloch & Schneider) captured in Mobile Bay (northcentral Gulf of Mexico), Alabama, USA. Empruthotrema longipenis n. sp. is most similar to the type-species Empruthotrema raiae (MacCallum, 1916) Johnston & Tiegs, 1922 by having 12 marginal and two interhamular loculi with members of haptoral hook pair 1 located midway along the periphery of each interhamular loculus and those of hook pair 2 located at the marginal termini of the bilateral septa flanking the interhamular loculi. Empruthotrema longipenis n. sp. differs from E. raiae by having a much longer male copulatory organ and from its remaining congeners by the sinistral and extracecal ejaculatory bulb flanking the pharynx, the number of interhamular and marginal septa, and the distribution of hook pairs 1 and 2 along the haptoral margin. This is the first report of a monocotylid from the smooth butterfly ray and from Mobile Bay. The diversity of haptoral morphotypes among the currently accepted species of Empruthotrema is detailed and discussed in the context of monophyly of the genus.     

Esters and other constituents of the foliar cuticular wax of a soybean variety

The constituents of the foliar cuticular wax of the variety ‘MG/BR 46 Conquista’ were isolated and chemically characterized. N-Alkanes, esters and triterpenoids are major constituents of the cuticular wax. Esters, taraxerol and steroids seem to be valuable cuticular wax constituents for characterization and distinction among soybean varieties.     

Ultrastructural and phylogenetic assessment of wax glands in pit scales (Homoptera : Coccoidea)

TEM/SEM and computerized images of 5 wax glands for 3 type species of Coccoidea (Homoptera): Asterodiaspis variolosa (Asterolecaniidae), Cerococcus quercus (Cerococcidae) and Lecanodiaspis sardoa (Lecanodiaspididae) were studied. Their cuticular structures were compared with 142, 56, and 61 species in their respective families to determine relationships among pit scale taxa. Significant differences include: the morphology of the outer and inner ductule of the tubular duct gland, structure of the pores (8-shaped, multilocular and quinquelocular), and the absence or presence of cribriform plates and their structural variations. Three distinctive tubular duct shapes (asterform, ceroform and lecanoform) are common in pit scale species. Apomorphic characteristics of the asterform tubular ducts include an absence of the inner ductule and the progressive reduction of the outer ductule's diameter from the pore to its inner end. These characters easily separate asterolecaniids from the cerococcid-lecanodiaspidid lineage. The constricted lecanoform tubular ducts and the curved teeth on the rim at the inner end of the outer ductule in the ceroform tubular ducts are regarded as autapomorphic. The presence of 8-shaped pores is considered a plesiomorphic condition. Specific cuticular variations of the 8-shaped pores, characterizing familial taxa, include pores even with the surface in asterolecaniids, pores with raised walls in cerococcids, and bent pores in lecanodiaspidids. The dominant 8-shaped pore patterns in pit scales are those arranged in a marginal band in lecanodiaspidids, in a swirl-like pore pattern in the cerococcids, and in a marginal row in asterolecaniids. A divergent evolutionary trend is noted for the structure of the cribriform plate; they are with micro-orifices in cerococcids, but without micro-orifices in lecanodiaspidids. The former state is considered apomorphic. Cribriform plates arranged in clusters characterize the cerococcids, while plates in longitudinal rows characterize the lecanodiaspidids. These data confirm the concept that the pit scales constitute a paraphyletic group and the Asterolecaniidae, Cerococcidae and Lecanodiaspididae are monophyletic.     

Waxes and lipids associated with the external waxy structures of nymphs and pupae of the giant whitefly, Aleurodicus dugesii

The nymphs and pupae of the giant whitefly, Aleurodicus dugesii, produce large quantities of external lipids, both as waxy particles and as waxy filaments. The nymphs and pupae extrude filaments from two dorsal rows of five pores each. Filaments can attain lengths of 5-8 cm. The external lipids of nymphs and pupae consist largely of long-chain aldehydes, alcohols, acetate esters and wax esters. Hydrocarbons are minor components. Soon after hatching, the nymph produced an unidentified waxy fringe extruded laterally from its margin. After molting to the second instar, long, hollow, waxy filaments were produced by the immature stages. The major lipid class associated with the filaments was saturated wax esters (89%), mainly C44, C46 and C60. Associated with formation of the filaments were waxy particles in the shape of curls, which peeled off of the extruding filaments. Similar but more tubular-shaped curls were also produced by numerous lateral pores so that, eventually, the curls completely camouflaged the nymph. The major lipid class of the curls was wax esters (50%), mainly C44 and C46. The cuticular surface lipids of the nymphs were mainly long-chain aldehydes (43%) and wax esters (27%). Unsaturated fatty acid moieties constituted 2 and 19% of the wax esters of curls and nymph cuticular surface lipids, respectively. The major lipid classes of pupae and of their palisade were long-chain aldehydes and alcohols. No unsaturated wax esters were detected in the filaments, but 30% of pupal and 21% of palisade surface wax esters were unsaturated in their fatty acid moieties, 16:1, 18:1 and 20:1.     

Euzetia occultum n. g., n. sp. (Euzetiinae n. subf.), a monocotylid monogenean from the gills of Rhinoptera neglecta (Rhinopteridae) from Moreton Bay,Queensland, Australia

Euzetia occultum n. g., n. sp. (Monogenea: Monocotylidae) is described from the gills of the Australian cownose ray Rhinoptera neglecta Ogilby collected in Moreton Bay, Queensland, Australia. Euzetia has one central and ten peripheral loculi, which is similar to species in Decacotyle Young, 1967. However Euzetia is distinguished from other genera in the family by the presence of an additional loculus on either side of the central loculus. Because Euzetia does not fit into any of the six existing subfamilies in the Monocotylidae Taschenberg, 1879, as currently recognised, we propose the Euzetiinae n. subf. to accommodate the new genus. Euzetia occultum is described and illustrated fully. This is the first published record of a monocotylid from a species of Rhinoptera Cuvier.     

Cuticular waxes from potato (Solanum tuberosum) leaves

The qualitative and quantitative compositions of leaf cuticular waxes from potato (Solanum tuberosum) varieties were studied. The principal components of the waxes were very long chain n-alkanes, 2-methylalkanes and 3-methylalkanes (3.1-4.6 microg cm(-2)), primary alcohols (0.3-0.7 microg cm(-2)), fatty acids (0.3-0.6 microg cm(-2)), and wax esters (0.1-0.4 microg cm(-2)). Methyl ketones, sterols, beta-amyrin, benzoic acid esters and fatty acid methyl, ethyl, isopropyl and phenylethyl esters were found for the first time in potato waxes. The qualitative composition of the waxes was quite similar but there were quantitative differences between the varieties studied. A new group of cuticular wax constituents consisting of free 2-alkanols with odd and even numbers of carbon atoms ranging from C25 to C30 was identified.     

Cuticular waxes in alpine meadow plants: climate effect inferred from latitude gradient in Qinghai‐Tibetan Plateau

Alpine meadow ecosystems are susceptible to climate changes. Still, climate impact on cuticular wax in alpine meadow plants is poorly understood. Assessing the variations of cuticular wax in alpine meadow plants across different latitudes might be useful for predicting how they may respond to climate change. We studied nine alpine meadows in a climate gradient in the east side of Qinghai‐Tibetan Plateau, with mean annual temperature ranging from −7.7 to 3.2°C. In total, 42 plant species were analyzed for cuticular wax, averaged 16 plant species in each meadow. Only four plant species could be observed in all sampling meadows, including Kobresia humilis,Potentilla nivea,Anaphalis lacteal, and Leontopodium nanum. The amounts of wax compositions and total cuticular wax in the four plant species varied among sampling meadows, but no significant correlation could be observed between them and temperature, precipitation, and aridity index based on plant species level. To analyze the variations of cuticular wax on community level, we averaged the amounts of n‐alkanes, aliphatic acids, primary alcohols, and total cuticular wax across all investigated plant species in each sampling site. The mean annual temperature, mean temperature in July, and aridity index were significantly correlated with the averaged amounts of wax compositions and total cuticular wax. The average chain length of n‐alkanes in both plant and soil linearly increased with increased temperature, whereas reduced with increased aridity index. No significant correlation could be observed between mean annual precipitation and mean precipitation from June to August and the cuticular wax amounts and average chain length. Our results suggest that the survival of some alpine plants in specific environments might be depended on their abilities in adjusting wax deposition on plant leaves, and the alpine meadow plants as a whole respond to climate change, benefiting the stability of alpine meadow ecosystem.     

Relationship Between Cuticular Waxes and Storage Quality Parameters of Korla Pear Under Different Storage Methods

Cuticular wax is an important factor that affects storage quality of fruits and vegetables. Previous studies have shown that cuticular wax of pears changes significantly during storage, whereas there are few studies on the effects of different storage methods on the wax changes and the relationship with storage quality. Cuticular wax of Korla pear stored using different methods, was measured to analyze its total wax content, chemical compositions and their relationship with storage quality. At the end of storage, the highest cuticular wax content was observed in controlled atmosphere (CA) storage and the lowest in room temperature storage. The substances of the primary components with higher contents were nonacosane, (E, E)-ɑ-farnesene, dodecan-1-ol, 1,1-dimethoxynonane, nonanal, palmitic acid, and oleic acid. Total wax content, olefins and fatty acids were most significantly with the storage quality, followed by alkanes and esters. Moreover, total wax content, wax composition and weight loss were closely related to postharvest senescence. Overall, an understanding of variations in the cuticular wax under different storage methods could provide theoretical basis for further study on the storage and preservation technology of pears.

     

角蜡蚧和日本龟蜡蚧蜡泌物的超微结构及化学成分分析

采用扫描电镜和气相色谱/质谱联用技术研究了角蜡Ceroplastes ceriferus (Fabricius) 和日本龟蜡蚧C. japonicus Green蜡泌物的超微结构及化学成分。结果表明,这2种蜡蚧分泌蜡质和形成蜡壳的过程基本相似。在1、2龄期分泌的蜡质为“干蜡”,蜡壳为星芒状,虫体周缘的蜡芒均为2大节,与其2个龄期发育相对应,每一个大节又分为若干小节。同时,虫体背面中央蜡质堆积成帽状,也分为均匀的多层。由此说明泌蜡过程具有节律性。虫体周缘与蜡芒对应的突起区上分布着密集的刻点状腺孔,每一个腺孔分泌1根蜡丝,这在以往玻片标本中是观察不到的。雌性第3龄幼虫和成虫期,虫体分泌“湿蜡”,形成龟背状蜡壳,泌蜡腺孔主要为三格腺和四格腺。在肛突区发现了密集的泌蜡腺孔,排列为纵条纹状。从角蜡蚧蜡泌物甲酯化处理样品中检测到14个组分,从直接测试 (未经甲酯化处理) 样品中检测到14个组分;而从日本龟蜡蚧则分别检测到10个组分和25个组分。它们的主要成分是一系列高级的长链饱和与不饱和的烃、脂肪酸、脂肪醇、酯类、醛类以及杂环、多环或大环状化合物。对它们可能的生物生态学功能进行了讨论。     

Fine mapping of BrWax1, a gene controlling cuticular wax biosynthesis in Chinese cabbage (Brassica rapa L. ssp. pekinensis)

The surface of plants is covered with a cuticular wax, which contains a mixture of very-long-chain fatty acid derivatives. This wax layer provides a hydrophobic barrier which reduces non-stomatal water loss and prevents pathogen attack. The biosynthesis pathway of cuticular wax in Arabidopsis is well studied; however, little is known about the synthesis of cuticular wax in Brassica rapa. Genetic analyses indicated that the waxy characteristic is controlled by a single dominant gene. In the present study, preliminary mapping results from an F2 population consisting of 308 recessive individuals showed that the BrWax1 (Brassica Wax) gene is located on linkage group A01. We developed a set of new markers closely linked to the target gene, and used another population of 1,020 recessive F2 individuals to fine-map the BrWax1 gene to a genomic DNA fragment of approximately 86.4 kb. Fifteen genes were identified in this target region. Based on gene annotation, the Bra013809 gene was the candidate for the BrWax1 gene. Quantitative real-time PCR analysis and expression pattern of the two parents showed that the expression level of Bra013809 was much higher in the waxy phenotype than in the glossy phenotype. This result should provide not only important information for functional studies of the BrWax1 gene, but also the starting point for studying the pathway of cuticular wax biosynthesis in Brassica rapa.     

Water loss in three species of tiger beetles (Cicindela): Correlations with epicuticular hydrocarbons

Water loss rates in dry air at 30°C and cuticular lipid/hydrocarbon composition were determined for three species (eight populations) of tiger beetles (Cicindela oregona, C. tranquebarica and C. obsoleta). The highest water loss rates were found in C. oregona (0.049 to 0.052 mg cm⁻²h⁻¹ mmHg⁻¹), a species active in spring and fall along water courses in Arizona, while the lowest rates were exhibited by C. obsoleta (0.022 to 0.028 mg cm⁻²h⁻¹ mmHg⁻¹), a summer-active species that inhabits dry grasslands. Water loss rates for C. tranquebarica were closer to those of C. obsoleta even though C. tranquebarica often coexists with C. oregona. Hydrocarbons were an important constituent of the cuticular lipids of all three species; smaller quantities of wax and cholesterol esters, triacylglycerols, free fatty acids, alcohols, and cholesterol were also detected. C. obsoleta contained the greatest amount of hydrocarbon per surface area. All of its hydrocarbon molecules were saturated, with branched components accounting for about 60% of the total fraction. Saturated (primarily n-alkanes) and unsaturated (n-alkenes) molecules were present in both C. oregona, which contained the lowest hydrocarbon surface density, and C. tranquebarica. The hydrocarbon composition of the three species is discussed in terms of its contribution to the epicuticular waterproofing barrier and its potential use as a chemotaxonomic tool.     

New tardigrade records for the Baltic states with a description of Minibiotus formosus sp. n. (Eutardigrada,Macrobiotidae)

In sixteen moss, lichen and mixed (moss/lichen) samples, collected from Estonia, Latvia and Lithuania, 291 specimens, 48 simplexes, including one exuvium with 6 eggs, and 8 free-laid eggs of eutardigrades were found. In total, 17 species, together with one new to science, were identified (all are new records for the Baltic states): Astatumen bartosi, Diphascon (Adropion) prorsirostre, D. (Diphascon) bullatum, D. (D.) pingue pingue, D. (D.) recamieri, D. (D.) rugosum, Hypsibius convergens, H. dujardini, H. cf. scabropygus, Isohypsibius ronsisvallei, I. sattleri, Macrobiotus harmsworthi harmsworthi, M. hufelandi hufelandi, Milnesium asiaticum, Milnesium tardigradum tardigradum, Minibiotus formosus sp. n. and Paramacrobiotus richtersi. The new species is most similar to Minibiotus gumersindoi, but differs from it mainly by the presence of two types of cuticular pores, the absence of a triangular or pentagonal arrangement of pores above a single large pore on legs, the presence of granulation on all legs and a different macroplacoid length sequence. In this paper we also provide photographs and morphometrics of H. cf. scabropygus.     

植物角质层蜡质的化学组成研究综述

角质层是植物与外界的第一接触面,而角质层蜡质则是由位于角质层外的外层蜡质和深嵌在角质层中的内层蜡质两部分构成。植物角质层蜡质成分极其复杂,具有重要的生理功能。综述了有关植物角质层蜡质的化学组成信息,探讨了目前植物角质层蜡质化学成分研究中存在的一些问题,展望了角质层蜡质成分的研究前景。     

The effects of Kloeckera apiculata on the cuticular waxes of navel orange fruit

Kloeckera apiculata 34-9 was selected from the rhizosphere soil for its high efficacy in controlling citrus green and blue mold. In this study, the effect of the antagonistic yeast K. apiculata on citrus cuticular wax was investigated in ripening Newhall navel orange (Citrus sinensis L. Osbeck). Our results show that K. apiculata triggers the production of cuticular waxes and surface wax morphology changes in the fruit surface. 15 K. apiculata-responsive differentially expressed genes (DEGs) were identified for wax metabolism by using the Affymetrix citrus genome GeneChip. Using GC–MS, 46 wax compounds were found in the Newhall fruit surface. On one hand, esters including docosanoic acid, 1,2,3-propanetriyl ester and 9-hexadecenoic acid, 9-octadecenyl ester were up-regulated approximately twofold in the treatment condition compared with the control; and on the other hand, the fatty acids and fatty alcohols decreased by 74.4% and 72.3%, respectively, in the treatment condition. The new wax production and increased hydrophobicity of the Newhall surface resulting from the treatment may influence spore adhesion and germination. Furthermore, the response of the fruit waxes to the K. apiculata stimulus is likely to be regulated by intra-cellular H₂O₂ signaling. This study demonstrated the response fruit waxes to K. apiculata in Newhall navel oranges, thus providing new clues that aid our understanding of the mechanisms of action of antagonistic yeasts in postharvest fruits.     

Will the climate of plant origins influence the chemical profiles of cuticular waxes on leaves of Leymus chinensis in a common garden experiment?

Cuticular wax covering the leaf surface plays important roles in protecting plants from biotic and abiotic stresses. Understanding the way in which plant leaf cuticles reflect their growing environment could give an insight into plant resilience to future climate change. Here, we analyzed the variations of cuticular waxes among 59 populations of Leymus chinensis in a common garden experiment, aiming to verify how environmental conditions influence the chemical profiles of cuticular waxes. In total, eight cuticular wax classes were identified, including fatty acids, aldehydes, primary alcohols, alkanes, secondary alcohols, ketones, β‐diketones, and alkylresorcinols, with β‐diketones the predominant compounds in all populations (averaged 67.36% across all populations). Great intraspecific trait variations (ITV) were observed for total wax coverage, wax compositions, and the relative abundance of homologues within each wax class. Cluster analysis based on wax characteristics could separate 59 populations into different clades. However, the populations could not be separated according to their original longitudes, latitudes, annual temperature, or annual precipitation. Redundancy analysis showed that latitude, arid index, and the precipitation from June to August were the most important parameters contributing to the variations of the amount of total wax coverage and wax composition and the relative abundance of wax classes. Pearson's correlation analysis further indicated that the relative abundance of wax classes, homologues in each wax class, and even isomers of certain compound differed in their responses to environmental factors. These results suggested that wax deposition patterns of L. chinensis populations formed during adaptations to their long‐term growing environments could inherit in their progenies and exhibit such inheritance even these progenies were exported to new environments.     

Crystal structures and chemical composition of leaf surface wax depositions on the desert moss Syntrichia caninervis

The structures and composition of cuticular waxes deposited on the leaves of a typical desert moss, Syntrichia caninervis, were investigated. The wax crystals deposited on leaves shifted with leaf aging. The results of chemical analysis showed the main chemical components of the moss wax were fatty acids, alcohols and alkanes. Leaf aging increased the content of cuticular wax and the percentage of very long chain components, from 1150 μg g⁻¹ DW and 13.6% in younger leaves to 2640 μg g⁻¹ DW and 37.2% in aged leaves, respectively. Dehydration/hydration also augmented the wax content by 35.17% in juvenile leaves and by 1900% in lab-cultivated leaves after three-cycle treatments. Synthesis of hexadecanoic acid and tetracosane were predicted to be the first step of wax accumulation. The responses of cuticular waxes in crystal structure and chemical composition were recommended as a biomonitor for assessing the shift of ecological and environmental quality.     

Fine mapping of <Emphasis Type="Italic">BoGL1</Emphasis>, a gene controlling the glossy green trait in cabbage (<Emphasis Type="Italic">Brassica oleracea</Emphasis> L. Var. <Emphasis Type="Italic">capitata</Emphasis>)

The cuticular wax covering epidermal cells causes the glaucous appearance in cabbage. As a protective barrier, cuticular wax plays various roles in protection against biotic and abiotic stresses. This is the first gene mapping report of a dominant glossy green cabbage mutant. In the present paper, scanning electron microscopy (SEM) demonstrated that the wax crystals were severely reduced in the mutant, which indicates that the glossy green phenotype is caused by cuticular wax reduction. Genetic analysis revealed that the glossy trait is controlled by a single dominant gene. Through primer screening and fine mapping, the mutant gene BoGL1 (Brassica oleracea glossy 1) was delimited to the end of chromosome C08 by the flanking marker SSRC08–76 at a genetic distance of 0.2 cM. Two genes homologous to CER1 (ECERIFERUM 1), a gene related to wax biosynthesis in Arabidopsis, were located in the mapped region. Expressional analysis revealed that the Bol018504 gene was severely suppressed but that no nucleotide variation was found by sequencing. These results lay the foundation for the functional analysis of BoGL1, and they will accelerate the research on wax metabolism in cabbage.     

Mechanism for range fractionation in chordotonal organs of Locusta migratoria (L) and Valanga sp. (Orthoptera : Acrididae)

The femoral chordotonal organ (FCO) of Locusta migratoria and Valanga sp. (Orthoptera : Acrididae) is a leg stretch receptor containing scolopophorous sensory neurones embedded in a ligament, which emerges distally from the body of the organ and connects to a distal apodeme. The ligament is pulled when the tibia is flexed. Thus the FCO bridges the femur-tibia joint. The ligament is divided into separate strands, each of which is composed of several or more, long attachment cells. These cells link individual scolopidia to the apodeme. An additional unloading strand connects the body of the FCO to a static point on the femoral integument. Because the strands are inserted along the apodeme in a sequential array, and because the unloading strand holds all the tension on the FCO when the ligament is relaxed (tibia extended), a mechanism for gradual, sequential uptake of tension by the ligament strands exists when the ligament is pulled (tibia flexed). This leads to a range fractionation of stretch-sensitive neurone responses during tibial flexion, and of relaxation-sensitive neurone responses during tibial extension. Observations on the ultrastructural distribution of desmosomes suggest that groups of attachment cells may be functionally connected and may collectively transmit force to specific groups of neurones.