The Stylet Apparatus of Monostiliferous Hoplonemerteans

This paper compares the ultrastructure, development, and functionalmorphology of the stylet apparatus in monostiliferous hoplonemerteans(Phylum Nemertea: Class Enopla). The apparatus occurs in themiddle region of the worm's eversible proboscis and consistsof two main components: 1) a central stylet that is attachedto an anchoring device called the basis; and 2) reserve styletsacs that contain nail-like reserve stylets. The knob-shapedproximal piece of the central stylet is embedded in the anteriorend of the basis, and the tapered shaft of the stylet is directedanteriorly. When the proboscis is fully everted, the centralstylet is used to stab such prey as polychaete worms and smallcrustaceans. Wounds inflicted by the stylet allow the introductionof paralytic neurotoxins that are produced by glandular cellsin the epithelial lining of the proboscis. Reservestylets formintracellularly within the reserve stylet sacs and serve toreplace the central stylet when it becomes lost or damaged.Fully developed stylets typically measure 50 to 250 µmin length and comprise an organic core surrounded by an inorganiccortex that contains calcium phosphate. In juvenile worms thatare four days to several weeks old, reserve stylets are assembledbefore other components of the stylet apparatus are fully differentiated.Subsequently, a reserve stylet is transferred to the centralregion of the proboscis and placed on the basis. Stages in theprocess of stylet attachment are described, and the probablesequence by which the stylet apparatus co-evolved with toxin-producingcells is discussed.     

Ultrastructure of the copulatory stylet and accessory spines in Haplopharynx quadristimulus (Turbellaria)

The copulatory organ of Haplopharynx quadristimulus Ax, 1971 (Carolina form, Rieger, 1977) consists of a proximal prostatic vesicle and a distal stylet apparatus comprising a central tubular stylet and four to five peripheral accessory spines. By electron microscopy it could be seen that the stylet and spines were intracellular specializations. The copulatory organ can be interpreted as a specialization of an epithelial canal extending from the testes to the body wall. In the complex stylet apparatus, the epithelium was differentiated into six cell types. The stylet, which was formed in a matrix syncytium next to the prostatic vesicle, extended into the lumen of the stylet canal. The interior of the stylet apparatus contained one group of cells that had thick ciliary rootlets and another that had rootlet-like ribbons.The cells that contain the rootlets enveloped bundles of longitudinally arranged muscles. The accessory spines were formed in cells which lay peripheral to the muscle bundles. The spines, stylet, rootlet-like ribbons, and rootlets had similar patterns of periodic cross striations. The similarity in striation patterns suggests that the accessory spines and stylet are composed of modified ciliary rootlets.     

The stylet apparatus of the nemertean Paranemertes Peregrina: Its ultrastructure and role in prey capture

Summary The nemertean Paranemertes peregrina captures prey by using an eversible proboscis that is armed with a stylet apparatus. The apparatus consists of several reserve stylet sacs and a central stylet that is attached to a granular mass, called the basis. When the proboscis is everted, the central stylet is used to stab prey such as nereid polychaetes, and paralytic neurotoxins, produced in the proboscis, are inserted in the stylet-induced wounds. The central stylet averages 85 m in length and has helically-arranged grooves along its shaft. The proximal piece of the central stylet is anchored to the basis, apparently by adhesive granules in the anterior end of the basis. A basis sheath surrounds the basis and is continuous posteriorly with a duct, called the ductus ejaculatorius. Secretions in the ductus ejaculatorius may contain some of the toxin that is used to immobilize the prey. The contents of the duct are probably injected into the prey by way of the grooves on the central stylet. In the region anterior to the central stylet, there are numerous glandular cells and anchor cells that are believed to attach the stylet apparatus to the prey during attack. Each reserve stylet sac is lined by a simple epithelium. One of the epithelial cells, called the styletocyte, is greatly enlarged and fills the lumen of the sac. Several reserve stylets are assembled in a styletocyte. Each reserve stylet is formed within a membrane-bound vacuole associated with the Golgi apparatus and is composed of an inner organic core surrounded by an inorganic cortex. A duct connects each reserve stylet sac with the area around the central stylet and provides a pathway for the transfer of reserve stylets during replacement of the central stylet.     

The fine structure of Gnathostomulid reproductive organs

Summary The male copulatory organs of five species of Gnathostomulida Scleroperalia have been studied by TEM techniques. These observations provide a more solid basis for classification in the light microscope: inLabidognathia longicollis (fam. Mesognathariidae) the stylet is composed of eight, and inSemaeognathia sterreri, Gnathostomula jenneri, Gnathostomula mediterranea andGnathostomula microstyla (Gnathostomulidae) of ten stylet rods. Each rod consists of a microtubule-filled inner rod, and of an outer rod, filled with crystallized inclusions. The inner rods are continuous with eight — or ten — rod formation cells which are located in the proximal stylet sack. Bipartition of rods occurs by a longitudinal invagination of the basement lamina, underlying the rod cells and the gland cells and continuous with that of the body wall epithelium. InLabidognathia, the outer rods are interlocked, in Gnathostomulidae, the stylet rods are surrounded by an extracellular (cuticular) tube-like stylet sheath of variable fine structure, which is believed to provide extra rigidity. In the species investigated, one single stylet gland, consisting of a monolayered epithelium showing different gland cell types, surrounds the stylet. In the apical gland cell portions, medially and distally membrane-bound secretory granules lie adjacent to the stylet sheath. In Gnathostomulidae, two anterior gland cells are seen in connection with the formation of the stylet sheath. In the muscular sheath the cross-striated fibers, basically derived from the longitudinal body wall musculature, show a tendency towards helical and circumferential arrangement. Musculature is especially prominent in the proximal stylet sack, which is rather a propulsive element than a sperm-storing vesicle, and lacks glands. InGnathostomula species, atrial cells underlie the distal tip of the stylet. The entrance into the male opening is lined with ciliary receptor cells and specialized gland cells.Stylet evolution in Scleroperalia is characterized by progressive differentiation of the muscular sheath, in particular of the proximal stylet sack, and of the stylet — the occurrence of a stylet sheath is seen in connection with increasing diversity of stylet shape.Abbreviations ac atrial cell(s) - ag anterior gland cell(s) - b bursa - bl basal lamina - c rod-crystal in outer rod - cj cuticle of jaw - d desmosome - di dictyosome - e body wall epithelium - ej pharyngeal epithelium - g stylet gland (cell) - gm median gland cell - i gut (cell) - ir inner rod - jc junctional complex - m muscular layer - mo male opening - mv microvillar protrusions - nu nucleus - o ovary - or outer rod - po proximal opening of the proximal stylet sack - ps proximal stylet sack - r stylet rod - rc rod cell - sg secretory granule - sj septate junction - sp sperm - ss stylet sheath - st stylet - te testes - v ventral - z centriole     

Feeding Position of Laccifer lucca on Dalbergia balansae and the Influence of Parasitism on Bark Structure

When Laccifer lacca fed in the bark of Dalbergia balansae, the penetration in the bark by a stylet was mainly intracellular, seldom intercellular. Finally, the stylet arrived at the funtional sieve element, and fed in it. The tip of tt,e stylet was at a distance of 0.48–0.78 mm from the surface of periderm. 70.3% of the stylets fed in the zone of newly-differentiated sieve elements. The fed sieve element had P-protein and callose, and exhibited no serious reaction of injury. The parenchyma cells that were pierced through by the stylet and the neighbouring cells Lad obvious reaction of injury, such as: thickened cytoplasm and plasmolysed; dark stained nuclei; smaller starch grains and intracellular deposition of concentrated golden material. The stylet that pierced through the bark was encircled by a stylet sheath consisted of proteins. The stylet sheath looked like a string of beads as a whole. Branching stylet sheath was observed. Some branches even reached far into the xylem, but the stylet finally reached the sieve element. At the same time, the stylet might penetrate through many sieve elements, finally reach newly-differentiated sieve elements. These results suggest that feeding of Laccifer lacca was a process of initiative choice. Two years after collecting shellac by means of skinning instead of cutting the branch, tb.e stylets and styler sheaths still remained in the bark. Several layers of ceils around them were dead and fully imbued with yellow-brown material. Stylers and styler sheaths in the outer cortex were surrounded by bending phellogen and separated from the living cells, forming many cyst-like structures in the periderm. Such bark should not be further used for feeding.     

Correlation of stylet activities by the glassy-winged sharpshooter, Homalodisca coagulata (Say), with electrical penetration graph (EPG) waveforms

Glassy-winged sharpshooter, Homalodisca coagulata (Say), is an efficient vector of Xylella fastidiosa (Xf), the causal bacterium of Pierce's disease, and leaf scorch in almond and oleander. Acquisition and inoculation of Xf occur sometime during the process of stylet penetration into the plant. That process is most rigorously studied via electrical penetration graph (EPG) monitoring of insect feeding. This study provides part of the crucial biological meanings that define the waveforms of each new insect species recorded by EPG. By synchronizing AC EPG waveforms with high-magnification video of H. coagulata stylet penetration in artifical diet, we correlated stylet activities with three previously described EPG pathway waveforms, A1, B1 and B2, as well as one ingestion waveform, C. Waveform A1 occured at the beginning of stylet penetration. This waveform was correlated with salivary sheath trunk formation, repetitive stylet movements involving retraction of both maxillary stylets and one mandibular stylet, extension of the stylet fascicle, and the fluttering-like movements of the maxillary stylet tips. Waveform B1 was ubitquious, interspersed throughout the other waveforms. B1 sub-type B1w was correlated with salivation followed by maxillary tip fluttering. This tip fluttering also occurred before and during B1 sub-type B1s, but was not directly correlated with either the occurrence or frequency of this waveform. Waveform B2 was correlated with sawing-like maxillary stylet movements, which usually occurred during salivary sheath branching. Waveform C was correlated with ingestion. Fluid outflow was also observed as a mechanism to clear the maxillary tips from debris during waveform C. This detailed understanding of stylet penetration behaviors of H. coagulata is an important step toward identifying the instant of bacterial inoculation which, in turn, will be applied to studies of disease epidemiology and development of host plant resistance.     

Styletogenesis in nemertean worms: The ultrastructure of organelles involved in intracellular calcification

The ultrastructure of cellular organelles involved in stylet formation is examined in six species of nemertean worms by transmission electron microscopy (TEM). Stylets are nail-shaped structures containing calcium phosphate that are assembled intracellularly in large uninucleate cells, called styletocytes. Each stylet develops within a membrane-bound vacuole in the styletocyte cytoplasm. Well developed arrays of Golgi bodies are typically found in the vicinity of developing stylet vacuoles, and fully formed vacuoles are filled with PAS+ material that appears to be derived from the smooth endoplasmic reticulum. At the onset of styletogenesis, a conical sliver of organic material differentiates on the inner surface of the vacuolar membrane. This material displays a species-specific banding pattern in decalcified sections, and apparently acts as a template during calcification of the stylet shaft. After the organic core of the shaft is formed, mitochondria aggregate around the stylet vacuole and presumably help accumulate the calcium used in mineralization of the stylet. A knob-shaped proximal piece is subsequently assembled on the base of the shaft. The proximal piece contains a nonbanded matrix and has electron-dense material at its surface that may help in correctly orienting this region toward the basis during replacement of the central stylet.     

Assessing the validity of stylets as ageing tools in Octopus pallidus

A method to age octopus was determined through the quantification of growth increments within the stylet structure (highly reduced internal shells). To validate the periodicity of the increments, stylets were analysed from known-age laboratory-raised Octopus pallidus. The animals, which ranged from 3 to 8 months old, were exposed either to a simulated natural or to constant temperature regime. Transverse stylet sections were embedded in thermo-plastic cement and ground until a thin section was achieved. A pre-hatch region and first post-hatch increment was identified in the stylet microstructure. The number of increments, across all ages and temperature treatments, was in remarkably close agreement to age (number of days), clearly demonstrating that stylet increments are deposited daily throughout the lifecycle of O. pallidus. Morphometric analyses of the stylet indicated that increments were laid down regularly during stylet growth and that stylets grew in concert with body size, further supporting daily periodicity. This study successfully validates daily increments in stylets and thus demonstrate a method to age octopus, therefore, potentially having critical implications for future octopus research and the effective management of stocks worldwide.     

Stylet penetration and survival of three psyllid species on adult leaves and `waxy' and `de-waxed' juvenile leaves of Eucalyptus globulus

The stylet probing behavior and survival of Ctenarytaina eucalypti Maskell, C. spatulata Taylor and Glycaspis brimblecombei Moore (Homoptera, Psyllidae) on adult leaves and `waxy' (untreated) and `de-waxed' (rubbed) juvenile leaves of the heteroblastic plant Eucalyptus globulus Labillardiere were compared. Psyllids were confined within clip-on cages and after 15 days the leaf tissue under each cage was sectioned and stained to characterize and quantify stylet tracks. Across all leaf treatments and psyllid species 1438 stylet tracks were observed in 7239 leaf sections and 571 of these stylet tracks reached the vascular tissue. Survival and the number of stylet tracks of C. eucalypti on the different leaf types did not differ. In contrast, C. spatulata survived significantly longer and produced significantly more stylet tracks on adult leaves and `de-waxed' juvenile leaves than on `waxy' juvenile leaves. Although G. brimblecombei survived equally on all treatments, it produced more stylet tracks on adult leaves and `de-waxed' juvenile leaves than on `waxy' juvenile leaves. For all three psyllid species, there was a positive correlation between survival and number of stylet tracks reaching the vascular tissue. Stylet tracks of all species were generally intercellular from the leaf epidermis to the vascular tissue. Oil glands were avoided by all species, as indicated by the repeated branching and formation of stylet tracks at the periphery of the glands. In `de-waxed' juvenile leaves, C. spatulata and G. brimblecombei produced stylet tracks that entered the leaf at the adaxial surface and exited at the abaxial surface. This pattern was rarely observed on adult leaves, and never occurred with C. eucalypti in any leaf type. We conclude that (1) the epicuticular wax on juvenile leaves reduced stylet probing by C. spatulata and G. brimblecombei, (2) there were apparently no internal physical barriers in either juvenile or adult leaves to prevent the stylets of any of the psyllid species from reaching the vascular tissue, (3) the psyllids avoided oil glands in both leaf types, and (4) C. spatulata and G. brimblecombei may lack cues to orient their stylets towards the vascular tissue in the juvenile leaves.     

Comparative ultrastructure of copulatory organs having a stylet in the Proseriata (Turbellaria)

The ultrastructure of male copulatory organs having a stylet has been studied in some genera of the Proseriata.Within the Monocelididae there was a variety of stylet-like hard structures. The stylet in Monocelis fusca was a differentiation of the basement membrane of the epithelium lining a penis-like muscular papilla. The penis papilla in Ectocotyla consisted of circular muscles surrounded by a thickened basement membrane and an epithelium. Archilopsis sp. and Archilina sp. with a duplex copulatory bulb, had a stylet within a spiny cirrus. The stylet in Archilopsis sp. was a cylindrical muscular protrusion with a thickened basement lamina that lined the cirrus lumen. The stylet structure in Archilina sp. was composed of four long spines which were derivatives of the basement membrane. In Ectocotyla multitesticulata and Dupliminona corsicana, the accessory prostatoid organ was provided with a hook-shaped stylet that was differentiated in the basement membrane and of which the material was continuous with the fibrous matrix between the muscles of the prostatic bulb. The stylet and needles in the Archimonocelis species were intracellular differentiations. The copulatory organ in Carenscoilia biforamen consisted of a tubiform stylet and four needles, all of which were also intracellular specializations.I consider copulatory hard structures in the Turbellaria to be taxonomically significant in terms of structure, differentiation, and location (whether subcellular, in the basement membrane, or intracellular).     

A new technique for studying the stylet tracks of homopteran insects in hand-sectioned plant tissue using light or epifluorescence microscopy

Homopteran insects, such as aphids, psyllids and scales, inject a proteinaceous salivary sheath into their host plant tissue during feeding. This sheath, also referred to as a stylet track, remains in the tissue after the stylets are withdrawn, and is useful for studying plant resistance to insects and plant virus transmission. We describe a new method for studying stylet tracks. Hand microtome sectioned plant material was fixed and cleared in ethanol. The stylet tracks were stained with acid fuchsin and counterstained with aniline blue or fast green. The acid fuchsin stained stylet tracks were pink to red under light microscopy, and orange under TRITC epifluorescence. Stylet tracks in unstained sections autofluoresced under DAPI epifluorescence. This new technique is significantly faster and less complex than previous techniques, and permitted visualization of stylet tracks with light or epifluorescence microscopy within 1 hr of collecting fresh plant material. The technique was also applicable to a broad range of homopterans and plant taxa and provided excellent photomicrographs.     

A new technique for studying the stylet tracks of homopteran insects in hand-sectioned plant tissue using light or epifluorescence microscopy

Homopteran insects, such as aphids, psyllids and scales, inject a proteinaceous salivary sheath into their host plant tissue during feeding. This sheath, also referred to as a stylet track, remains in the tissue after the stylets are withdrawn, and is useful for studying plant resistance to insects and plant virus transmission. We describe a new method for studying stylet tracks. Hand microtome sectioned plant material was fixed and cleared in ethanol. The stylet tracks were stained with acid fuchsin and counterstained with aniline blue or fast green. The acid fuchsin stained stylet tracks were pink to red under light microscopy, and orange under TRITC epifluorescence. Stylet tracks in unstained sections autofluoresced under DAPI epifluorescence. This new technique is significantly faster and less complex than previous techniques, and permitted visualization of stylet tracks with light or epifluorescence microscopy within 1 hr of collecting fresh plant material. The technique was also applicable to a broad range of homopterans and plant taxa and provided excellent photomicrographs.     

Fine structure of aphid stylet pathways and its use in host plant resistance studies

Conclusion Although there have been reports, based on light microscope observations, of damage to mesophyll tissue as a result of stylet penetration, we saw no evidence of this in our wax sections. However, the use of the electron microscope revealed that such damage does occur, and has also shown that both inter- and intracellular penetration routes exist, often within the same track, whereas we had formerly believed the stylet pathways of these aphids to be almost entirely intercellular. The intramural-extracellular route of penetration, characterised by the presence of stylets and or saliva between the cell wall and plasmalemma, requires the greater resolution of electron microscopy and cannot be distinguished in light microscope preparations.Our results suggest that an accurate indication of the stylet pathway cannot be obtained from the use of light microscopy alone, and raise serious doubts about the value of previous studies describing the route of stylet penetration. Light microscopy shows the track only at the tissue level and not at the cellular level. We advocate that all future studies of aphid stylet penetration should utilise both light and electron microscope studies because only the higher resolution of the latter technique will indicate the true stylet pathway and the end points of the tracks. Only then can the feeding site be determined with any precision.     

Some observations on the role of ATP in sieve tube translocation

Summary Using the aphid stylet technique ¹⁴C ATP was shown to be readily taken up into the sieve elements of willow. At the same time this compound was found to be metabolised during uptake resulting in labelled ADP and AMP appearing in the stylet exudate. Longitudinal movement of labelled ATP was also found to occur.Measurement of the levels of ATP and ADP in stylet exudate showed that both were present in high concentrations. The ratio ATP/ADP varied between 2.0 and 5.3.The effect of certain inhibitors of oxidative phosphorylation (oligomycin and DNP) and glycolysis (fluoride) on the rate of stylet exudation was studied. All three inhibitors caused a cessation of exudation but this did not occur until several hours after inhibitor application. Oligomycin and DNP had no effect on the concentration of ATP in the sap. Fluoride however, appeared in some cases to reduce the ATP concentration to a low level an hour or more before exudation finally stopped.Incorporation of ³²Pi into organic phosphate esters present in stylet exudate was found to occur within 15 minutes of the application of the tracer to a bark strip. Labelling of organic phosphates also took place, at a slower rate, when ³²P inorganic phosphate was incubated with stylet exudate.     

Meloidogyne trifoliophila n. sp. (Nemata: Meloidogynidae), a Parasite of Clover from Tennessee

Meloidogyne trifoliophila n. sp. is described from white clover collected at Ames Plantation, Fayette County, Tennessee. The perineal pattern is rounded, with long, smooth striae and rounded arch, and without distinct lateral lines or perivulval striae. The female stylet is 12.6-15.5 μm long, the excretory pore is level with or up to one stylet length posterior to the stylet knobs, and the vulva is subterminal. The posterior terminus is weakly protuberant. The male lateral field is composed of approximately eight repeatedly broken or forked incisures. The male stylet is 17.0-18.9 μm long, the stylet knobs are rounded and sloping, gradually merging with the shaft, and the head region consists of one large annule. Second-stage juveniles are 357-400 μm long, with a stylet length of 11.9-13.6 μm and one head annule. The tail tapers to a slender tip. This new species is similar to M. graminicola and M. triticoryzae but differs from them in perineal pattern and lateral field morphology, and numerous morphometric characters.     

Stylet formation in Anisus vortex (Linnaeus, 1758) (Gastropoda: Planorbidae)

Soldatenko, E.V., Shatrov A.B. and Shumeev, A.N. (2010). Stylet formation in Anisus vortex (Linnaeus, 1758) (Gastropoda: Planorbidae). —Acta Zoologica (Stockholm) 92 : 377–382. The detailed stylet morphology and stylet formation during postembryonic development in the pulmonate mollusk Anisus vortex (Linnaeus, 1758) are described using scanning electron microscopy (SEM) and histological methods. The stylet begins to develop in the lumen of the copulatory apparatus and then assumes its final position inside the penial sac. The developing stylet lying between two epithelial layers is undergoing chitinization mediated by secretion of the secretory epithelium of the penial sac that completes on the 80–120th day after hatching of mollusks from the egg masses. The stability of the characters of stylet morphology and their significance for the systematics of Planorbidae are discussed.     

Description of the Blueberry Root-knot Nematode,Meloidogyne carolinensis n. sp.

Meloidogyne carolinensis n. sp. is described from cultivated highbush blueberry (cultivars derived from hybrids of Vaccinium corymbosum L. and V. lamarckii Camp) in North Carolina. The perineal pattern of the female has a large cuticular ridge that surrounds the perivulval area, and the excretory pore is near the level of the base of the stylet. The stylet is 15.9 μm long and the knobs gradually merge with the shaft. The head shape and stylet morphology of the male are quite variable. The typical head and four variants, as well as the typical stylet and two variants, are described. The labial disc, medial lips, and lateral lips of second-stage juveniles are fused and in the same contour. The head region is not annulated. Mean juvenile length is 463.7 μm, stylet length is 11.9 μm, and tail length is 42.5 μm.     

Ultrastructure of the copulatory organ of Haplopharynx quadristimulus and its phylogenetic significance (Plathelminthes,Haplopharyngida)

Summary The male reproductive system in Haplopharynx quadristimulus consists of paired testes, sperm ducts, seminal vesicles, seminal ducts, a copulatory organ containing prostatic vesicle and stylet apparatus, and the male canal. By electron microscopy all components appeared to be regional specializations of a canal extending from the testes to the body wall and lined by a multiciliated epithelium. The epithelium of the stylet apparatus contained six different cell types. One cell type (matrix syncytium) formed the stylet and the other five were located distal to the stylet/prostatic-vesicle junction along the male system epithelium. Each cell type was attached to the supporting intercellular matrix at a different level along the stylet apparatus. All cell types extended to the distal end of the stylet apparatus regardless of where they originated along its length. The cells in the apparatus lacked cilia, but one of the cell types contained rootlets. Modified rootlets or rootlet derivatives were possibly present in another cell type in the form of rootlet-like ribbons. The findings support the monophyly of the Macrostomida Haplopharyngida (by common occurrence of a matrix syncytium) and at the same time suggest their separation as two distinct taxa (by differences in the structure of the prostatic vesicle and other parts of the stylet apparatus).Abbreviations a accessory spine - c circular muscle - ce centriole - ci cilium - di dictyosome - e epithelial cell - ed ejaculatory duct - ep epidermal cell - f rootlet-like ribbon - g prostatic gland cell neck - g1 type I gland cell granules - g2 type II gland cell granules - g3 type III gland cell granules - h hemidesmosome - i intercellular matrix - im internal muscle - j septate junction - l stylet apparatus lumen - le spine lateral extension - lm longitudinal muscle - m matrix syncytium - mc male-canal epithelial cell - me male canal - mp male pore - mt microtubules - mv microvilli - n nucleus - nc nerve cell body - np nerve process - om oblique muscle - p prostatic vesicle epithelial cell - pv prostatic vesicle - r rootlet - s stylet - sa stylet apparatus - sc sensory receptor - sd sperm duct - se seminal duct - sl stylet lumen - sp spot desmosome - sr sperm - sv seminal vesicle - t terminal web - te testis - u ultrarhabdite - z zonula adhaerens - 2 cell type 2 - 3 cell type 3 - 4 cell type 4 - 6 cell type 6     

Ultrastructure of the Head Region of Molting Second-Stage Juveniles of Heterodera glycines with Emphasis on Stylet Formation

The morphology and alterations of infective juvenile (J2) body components with emphasis on the body wall, stomatal wall, stylet, and sensilla of Heterodera glycines were observed. During the molt of J2 to J3, the J2 hypodermis separates from the J2 cuticle and forms an extracellular space, continuous with an invagination of the anterior, center of the J3. The space between the J2 cuticle and the enlarged J3 hypodermal cells is filled with electron-dense material resembling a fluid observed in insects during molt. Regeneration of the J2 during molt was traced in a series of ultrathin sections. The site of stylet regeneration is in the hypodermal and myoepithelial tissues of the invaginated anterior, center of the J3. Four arcade-like cells are related to specific components of the stomatal wall, the stylet cone, and the stylet shaft of the J3. The first and second arcade-like cells are primarily related to stomatal wall development, whereas the third and fourth arcade-like cells are related to stylet cone and shaft development. Spherical, electron-translucent vacuoles that occur in myoepithelial cells just posterior to the arcade-like cells appear to be progenitors of the stylet knobs. Early stages of protractor muscle attachment to the vacuolar membrane were observed.     

Meloidogyne lusitanica n. sp. (Nematoda: Meloidogynidae), a Root-knot Nematode Parasitizing Olive Tree (Olea europaea L.)

A root-knot nematode from Portugal, Meloidogyne lusitanica n. sp., is described and illustrated from specimens obtained from olive trees (Olea europaea L.). Females of the new species have a characteristic perineal pattern with medium to high trapezoidal dorsal arch with distinct punctuations in the tail terminus area. The excretory pore is located posterior to the stylet, about 1.5-2.5 stylet lengths from the anterior end. The stylet is 17.1 μm long with pear-shaped knobs. Males have a rounded, posteriorly sloping head cap and head region not annulated. The robust stylet, 24.5 μ long, has large, elongate knobs. Mean length of the second-stage juveniles is 449.5 μm, stylet length 14.2 μm, and tail length 44.1 μm. Scanning electron microscope observations provide further details of perineal patterns and head and stylet morphology of females, males, and second-stage juveniles. Meloidogyne lusitanica n. sp. did not reproduce on any of the differential hosts used to separate the four most common Meloidogyne species. The common name "olive root-knot nematode" is proposed for M. lusitanica n. sp.