Neural organization of the lamina neuropil of the larva of the tiger beetle (Cicindela chinensis)

Six neural elements, viz., retinular axons, a giant monopolar axon, straight descending processes (type I), lamina monopolar axons (type II), processes containing clusters of dense-core vesicles (type III), and processes coursing in various directions with varicosities (type IV), have been identified at the ultrastructural level in the lamina neuropil of the larval tiger beetle Cicindela chinensis. Retinular axons make presynaptic contact with all other types of processes. Type I and II processes possess many pre-and postsynaptic loci. Type II processes presumably constitute retinotopic afferent pathways. It remains uncertain whether type I processes are lamina monopolar axons or long retinular axons extending to the medullar neuropil. Type III processes may be efferent neurons or branches of afferent neurons contributing to local circuits. A giant monopolar axon extends many branches throughout the lamina neuropil; these branches are postsynaptic to retinular axons, and may be nonretinotopic and afferent. Type IV processes course obliquely in the neuropil, being postsynaptic to retinular axons, and presynaptic to type I processes.     

Behavioral analysis of two distinct visual responses in the larva of the tiger beetle (Cicindela chinensis)

The tiger beetle larva shows two distinct visual responses, a predatory jump and an evasive withdrawal into the burrow (escape). In the present study the visual stimuli controlling these two responses have been behaviorally analyzed in the larva of Cicindela chinensis. The threshold size needed for a target to elicit both responses is a visual angle of 5–7°. The velocities of moving targets needed to elicit the responses are 0.4–33° s⁻¹ for the jump and 0.76–90° s⁻¹ for the escape. Choice between the two responses appears to be controlled by the actual target size rather than by the angular size. It also appears to be controlled by the target height. As the height of the target increases, the probability for the jump decreases, whereas the probability for the escape increases. Response properties of the larva with only a single functional stemma, the other stemmata being occluded, are different from those of the intact larva, which suggests cooperation of at least two stemmata for the release of different visual responses. Visual responses of the one-stemma larva still vary, however, with target size and target height, which suggests the visual responses are partially controlled even by a single stemma. Although our data do not resolve these conflicting results, more than one stemma is necessary for a firm choice between the two responses. Accepted: 13 May 1997     

Optic lobes of the larval and imaginal scorpionfly Panorpa vulgaris (Mecoptera,Panorpidae): A neuroanatomical study of neuropil organization,retinula axons,and lamina monopolar cells

Panorpa larvae possess stemmata (lateral ocelli), which have the structure of compound eyes, and stemma lamina and stemma medulla neuropils. A distinct lobula neuropil is lacking. The stemma neuropils have a columnar organization. They contain lamina monopolar cells, and both short and long visual fibers. All the identified larval monopolar neurons have radially arranged dendrites along the entire depth of the lamina neuropil and a single terminal arborization within the medulla (L1/L2-type). The terminals of visual fibers have short spiny lateral projections. Long fibers possess en passant synapses within the lamina. The same principles of organization of first and second order visual neuropils are found in Panorpa imagines. In contrast to the larvae, a lobula neuropil is present. Adults have monopolar cells of the L1-type that are similar to the L1-neurons found in Diptera. The columnar organization, the presence of short and long visual fibers, and lamina monopolar neurons are thus features common to both visual systems, viz., the larval (stemmata) and the imaginal (compound eyes).     

Morphological and physiological identification of medulla interneurons in the visual system of the tiger beetle larva

The morphology of visual interneurons in the tiger beetle larva was identified after recording their responses. Stained neurons were designated as either medulla or protocerebral neurons according to the location of their cell bodies. Medulla neurons were further subdivided into three groups. Afferent medulla neurons extended processes distally in the medulla neuropil and a single axon to the brain through the optic nerve. They received their main input from stemmata on the ipsilateral side. Two distance-sensitive neurons, near-by sensitive and far-sensitive neurons, were also identified. Atypical medulla neurons extended their neurites distally in the medulla and proximally to the brain, as afferent medulla neurons, but their input patterns and the shapes of their spikes differed from afferent neurons. Protocerebral neurons sent a single axon to the medulla neuropil. They spread collateral branches in the posterior region of the protocerebrum on its way to the medulla neuropil. They received main input from stemmata on the contralateral side. Medulla intrinsic neurons did not extend an axon to the brain, and received either bilateral or contralateral stemmata input only. The input patterns and discharge patterns of medulla neurons are discussed with reference to their morphology.     

Histamine-like immunoreactivity in the visual system and brain of Drosophila melanogaster

Summary In this study, immunohistochemistry on cryostat sections is used to demonstrate anti-histamine immunoreactivity in the Drosophila brain. The results support earlier findings that histamine is probably a transmitter of insect photoreceptors. It is further shown that, in Drosophila, all imaginal photoreceptors including receptor type R7 are anti-histamine immunoreactive, whereas the larval photoreceptors do not seem to contain histamine. In addition to the photoreceptors, fibres in the antennal nerve and approximately 12 neurons in each brain hemisphere show strong histamine-like immunoreactivity. These cells arborize extensively in large parts of the central brain.     

Spatial density-dependent survival and development at different larval stages of the tiger beetle <Emphasis Type="Italic">Cicindela japonica</Emphasis> (Thunberg)

Conspecific competition is an important component of the ecological processes of many species. In the case of sessile consumers, high population densities lead to competition within conspecific populations that, in turn, affect the survival, growth, and reproduction of the individuals involved. This study quantified neighborhood crowding and evaluated the extent of density effects on a tiger beetle (Cicindela japonica Thunberg) population by monitoring individually identified larvae at regular intervals. As an index of conspecific competition, the neighborhood density (the number of other larvae within a given radius for each larva) of each individual was measured. The radius size representing the highest mean coefficient of variation of density was determined as a suitable scale for detecting the density effects. Multiple logistic regression analysis was carried out to evaluate the effects of three factors (neighborhood density, prey abundance, and environmental influences) on larval survival and development. The analysis revealed that the neighborhood density significantly influenced the survival and development of larvae through every larval stage from the first to the third-instars. Moreover, the neighborhood density had a stronger influence on larvae of the same instar as compared to that on those of different instars. Our results suggest that density-dependent mortality affects the tiger beetle larvae due to the lifestyle pattern of these sedentary, ambushing predators that exhibit an aggregated spatial distribution.     

Histological,histochemical and electron microscopical studies on the nervous apparatus of the pineal organ in the tiger salamander,Ambystoma tigrinum

Summary 150–190 photoreceptor cells form a basic structural component of the pineal organ of Ambystoma tigrinum. Most of the outer and inner segments of these cells project into the lumen horizontally. Only 10 percent of the total number of photoreceptor cells are located within the pineal roof which is composed of a single cell layer. The photoreceptor cells are connected with nerve cells by synapses displaying characteristic ribbons. Different types of synaptic contacts, i.e. simple, tangential, dyad, triad and invaginated, are found. They are embedded in extended neuropil zones. A particular type of synapse indicates the presence of interneurons. The basal processes of some photoreceptor cells leave the pineal organ and make synaptic contacts with nervous elements located within the area of the subcommissural organ. Employing the method of Karnovsky and Roots (1964) for histochemical demonstration of acetylcholinesterase (AChE) approximately 70 neurons (intrapineal neurons) can be discerned in the pineal organ of Ambystoma tigrinum. In analogy to the distribution of photoreceptor cells only few nerve cells are observed in the roof portion of the pineal organ. Evidently, two different types of AChE-positive intrapineal neurons are present. About 40–50 AChE-positive neurons (extrapineal neurons) are scattered in the area of the subcommissural organ. In this area two types of nerve cells can be distinguished: 1) neurons which send pinealofugal (afferent) axons toward the posterior commissure and 2) neurons which emit pinealopetal (efferent) axons into or toward the pineal organ.The nervous pathways connecting the pineal organ with the diencephalomesencephalic border area are represented by a distinct pineal pedicle and several accessory pineal tracts.Granular nerve fibers run within the posterior commissure and establish synaptic contacts in the commissural region adjacent to the pineal organ. Some of these granular elements enter the pineal organ.The morphology of the nervous apparatus of the pineal organ of Ambystoma tigrinum is discussed in context with evidence from physiological experiments.In partial fulfillment of the requirements for the degree of Dr. med., Faculty of Medicine, Justus Liebig University, GiessenThe author is indebted to Professors A. Oksche and M. Ueck for their interest in this study. Thanks are due to Professor Ch. Baumann, Giessen, and Professor H. Langer, Bochum, for stimulating discussions. The technical assistance of Miss R. Liesner is gratefully acknowledgedDedicated to Professor Berta Scharrer on the occasion of her 70th birthday. Supported by grants from the Deutsche Forschungsgemeinschaft to A.O. and M.U.     

Ultrastructure and central projections of extraocular photoreceptors in caddiesflies (Insecta: Trichoptera)

Summary Retained larval eyes (stemmata) were studied in the imagines of three species of Trichoptera: Phrygania grandis, Agrypnia varia, and Trichostegia minor. At the light-microscopic level the stemmata of all three species appeared to represent different stages of reduction with respect to size, shape and number of lenses. However, in all three species electron-microscopic studies showed units with monolayered rhabdoms, each formed by four retinula cells. By use of immunocytochemistry the presence of S-antigen was demonstrated in the retinula cells and their axons. This method also revealed the central projections of the axons of the retinula cells, which were found (i) to terminate either in the lamina accessoria or (ii) to penetrate this area to join the fibers of the outer chiasma of the optic lobes and then terminate in the medulla accessoria. The lamina accessoria and the medulla accessoria are the assumed remnants of the larval optic lobes. It is suggested that the imaginal stemmata might still be functioning photoreceptors.     

Structure and development of the larval central complex in a holometabolous insect,the beetle Tenebrio molitor

Summary The neuroarchitecture of the central complex, a prominent neuropil in the midbrain of the holometabolan, Tenebrio molitor, is described throughout larval development. The analysis is based on classical silver impregnations and on fate-mapping of identified neurons using antisera against serotonin and FMRF-amide. In T. molitor, the central body is present in the first larval instar, and is formed by side branches of contralaterally projecting neurons. Glial cells surround eight neuropil compartments in the first larval instar. These subdivisions in the organization of the fan-shaped body are maintained throughout development. Intrinsic interneurons are found from the 5th larval instar onwards. In the last larval stage, the central complex consists of the fan-shaped body, the protocerebral bridge, and the anlage of the ellipsoid body. The cellular architecture of the fan-shaped body of the last larval instar resembles the basic structural characteristics of the adult. Serotonin-immunoreactive neurons and FMRF-amide immunoreactive neurons in the midbrain of the first larval instar show the basic structural features of the respective imaginal cells. The structural organizations of larval and adult midbrain are compared.Abbreviations a Anterior - AGT antenno-glomerular tract - aL -lobus - AL antennal lobe - AP anterior protocerebrum - bL -lobe - BSN bilateral symmetrical - FMRF amide-immunopositive neurons - CA calyx - CL1-CL4 serotonin-immunopositive neurons cluster 1–4 - d dorsal - DAB diaminobenzidine tetrahydrochloride - DC dorsal commissure - DCFB dorsal commissure of the fan-shaped body - DHT dorsal horizontal tract - DLTR dorsal lateral triangle - DMLP dorsal medial lateral protocerebrum - DN serotonin-immunopositive deuterocerebral neuron - EB ellipsoid body - en1, en2 extrinsic neurons connecting two FB-subcompartments - esn extrinsic subcompartmental neuron - l lateral - FB fan-shaped body - FN serotonin-immunopositive fan-shaped neuron - fs1, fs2 fanshaped neurons of type 1 and 2 - GC great commissure - HF horizontal fibres - in intrinsic neuron connecting two FB-subcompartments - isn intrinsic subcompartmental neuron - IT isthmus tract - LF large-field neurons - LFASC lateral fascicle - LMFASC lateral median fascicle - MB median bundles - MLP medial lateral protocerebrum - p posterior - P pedunculus - PB protocerebral bridge - pb-fb protocerebral bridge-fan-shaped body connection - PBS phosphate-buffered saline - PDC posterio-dorsal commissure - PTX phosphate-buffered saline containing Triton X-100 - SU suboesophageal ganglion - SVT small ventral triangles - TN 1,2 tritocerebral serotonin-immunoreactive neuron 1,2 - v ventral - VB ventral body - VBC ventral body commissure - VCBC ventral central body commissure - VCFB ventral commissure of the fan-shaped body     

The embryonic development of the Drosophila visual system

We have used electron-microscopic studies, bromodeoxyuridine (BrdU) incorporation and antibody labeling to characterize the development of the Drosophila larval photoreceptor (or Bolwig's) organ and the optic lobe, and have investigated the role of Notch in the development of both. The optic lobe and Bolwig's organ develop by invagination from the posterior procephalic region. After cells in this region undergo four postblastoderm divisions, a total of approximately 85 cells invaginate. The optic lobe invagination loses contact with the outer surface of the embryo and forms an epithelial vesicle attached to the brain. Bolwig's organ arises from the ventralmost portion of the optic lobe invagination, but does not become incorporated in the optic lobe; instead, its 12 cells remain in the head epidermis until late in embryogenesis when they move in conjunction with head involution to reach their final position alongside the pharynx. Early, before head involution, the cells of Bolwig's organ form a superficial group of 7 cells arranged in a rosette pattern and a deep group of 5 cells. Later, all neurons move out of the surface epithelium. Unlike adult photoreceptors, they do not form rhabdomeres; instead, they produce multiple, branched processes, which presumably carry the photopigment. Notch is essential for two aspects of the early development of the visual system. First, it delimits the number of cells incorporated into Bolwig's organ. Second, it is required for the maintenance of the epithelial character of the optic lobe cells during and after its invagination.     

Specialized ommatidia for polarization vision in the compound eye of cockchafers,Melolontha melolontha (Coleoptera,Scarabaeidae)

Summary The superposition eye of the cockchafer, Melolontha melolontha, exhibits the typical features of many nocturnal and crepuscular scarabaeid beetles: the dioptric apparatus of each ommatidium consists of a thick corneal lens with a strong inner convexity attached to a crystalline cone, that is surrounded by two primary and 9–11 secondary pigment cells. The clear zone contains the unpigmented extensions of the secondary pigment cells, which surround the cell bodies of seven retinula (receptor) cells per ommatidium and a retinular tract formed by them. The seven-lobed fused rhabdoms are composed by the rhabdomeres of the receptor cells 1–7. The rhabdoms are optically separated from each other by a tracheal sheath around the retinulae. The orientation of the microvilli diverges in a fan-like fashion within each rhabdomere. The proximally situated retinula cell 8 does not form a rhabdomere. This standard form of ommatidium stands in contrast to another type of ommatidium found in the dorsal rim area of the eye. The dorsal rim ommatidia are characterized by the following anatomical specializations: (1) The corneal lenses are not clear but contain light-scattering, bubble-like inclusions. (2) The rhabdom length is increased approximately by a factor of two. (3) The rhabdoms have unlobed shapes. (4) Within each rhabdomere the microvilli are parallel to each other. The microvilli of receptor 1 are oriented 90° to those of receptors 2–7. (5) The tracheal sheaths around the retinulae are missing. These findings indicate that the photoreceptors of the dorsal rim area are strongly polarization sensitive and have large visual fields. In the dorsal rim ommatidia of other insects, functionally similar anatomical specializations have been found. In these species, the dorsal rim area of the eye was demonstrated to be the eye region that is responsible for the detection of polarized light. We suggest that the dorsal rim area of the cockchafer eye subserves the same function and that the beetles use the polarization pattern of the sky for orientation during their migrations.     

Structural organization of ovarian follicle cells in the cotton bug (Dysdercus intermedius) and the honeybee (Apis mellifera)

Summary The somatic epithelia of Dysdercus and Apis follicles were analyzed by electron microscopy, and the patterns of F-actin and microtubules were studied by fluorescence microscopy. The epithelia in both species differ considerably in shape and in the organization of the cytoskeleton. During previtellogenic stages, the epithelium consists of columnar-shaped cells with small (Dysdercus) or no (Apis) lateral intercellular spaces. During vitellogenesis, the follicle cells round up; the intercellular spaces increase in size in Dysdercus follicles, whereas in Apis follicles they remain small. Along the basal surface of the follicle cells, there are conspicuous parallel bundles of microfilaments perpendicular to the anteroposterior axis of the follicles. In the honeybee, these microfilament bundles are present in long filopodia, most of which are embedded in thickenings of the basement membrane and extend over the surfaces of neighbouring cells. In the cotton bug, the basal surface of the follicle cells is thrown into parallel folds. The microfilament bundles are located just underneath the cell membrane where the folds contact the basement membrane. In the polar regions of the Dysdercus follicle, the epithelial cells become flat and adhere to each other without forming intercellular spaces. The basement membrane is particularly thick in the polar areas; this has also been observed in Apis follicles around the intercellular bridge connecting oocyte and nurse cells.     

Direct connections between the R7/8 and R1–6 photoreceptor subsystems in the dipteran visual system

Summary Musca and related flies have three main photoreceptor subsystems. The R1–6 group has short axons that terminate in the cartridges of the first optic neuropile, the lamina. The cartridges are bypassed by the longer axons of R7 and R8, which run together to terminate at different levels in the underlying medulla neuropile. The present account describes a shallow, previously unidentified zone in the lamina within which R7/8 make glancing contact with R1–6. At the distal border of the cartridge over no more than 3–4 m depth, the tangentially directed short axon of R6 squeezes between the pair from R7 and R8, forming quite large areas of mutual contact (approximately 7 m²). Less frequently, R1 is contacted. At least some of these sites contain smaller membrane specialisations indistinguishable from the more numerous gap junctions found more proximally that interconnect the terminals of R1–6. The R7/8 junctions with R6 are of comparable size (0.15 m²) and likewise possess symmetrical membrane densities. They provide proposed pathways for direct electrical interaction to account for observed electrical input from R7/8 to the R1–6 subsystem. In two cases R7/8 was possibly postsynaptic to R1–6 at a multiple-contact synapse, but even if functional, these sites were so rare that they are unlikely to have much operational significance.     

Morphological specializations of dorsal rim ommatidia in the compound eye of dragonflies and damselfies (Odonata)

We have examined the fine structure of dorsal rim ommatidia in the compound eye of the three odonate species Sympetrum striolatum, Aeshna cyanea and Ischnura elegans. These ommatidia exhibit several specializations: (1) the rhabdoms are very short, (2) there is no rhabdomeric twist, and (3) the rhabdoms contain only two, orthogonally-arranged microvillar orientations. The dorsal rim ommatidia of several other insect species are known to be anatomically specialized in a similar way and to be responsible for polarization vision. We suggest that the dorsal rim area of the odonate compound eye plays a similar role in polarization vision. Since the Odonata are a primitive group of insects, the use of polarized skylight for navigation may have developed early in insect phylogeny.     

Anti-actin immunoreactivity is retained in rhabdoms of Drosophila ninaC photoreceptors

Summary The Drosophila ninaC mutation produces small rhabdomeres with the axial filament of the microvillar cytoskeleton reduced or missing. Using post-embedding immunogold labelling of LR White-embedded eyes, we show that several alleles of this mutation retain positive anti-actin immunoreactivity in the rhabdomeres, comparable to that of wild-type flies.     

The distribution of pheromone-biosynthesis-activating neuropeptide (PBAN) immunoreactivity in the central nervous system of the corn earworm moth,Helicoverpa zea

Summary Production of sex pheromone in several species of moths has been shown to be under the control of a neuropeptide termed pheromone-biosynthesis-activating neuropeptide (PBAN). We have produced an antiserum to PBAN from Helicoverpa zea (Lepidoptera: Noctuidae) and used it to investigate the distribution of immunoreactive peptide in the brain-suboesophageal ganglion complex and its associated neurohemal structures, and the segmental ganglia of the ventral nerve cord. Immunocytochemical methods reveal three clusters of cells along the ventral midline in the suboesophageal ganglion (SOG), one cluster each in the presumptive mandibular (4 cells), maxillary (12–14 cells), and labial neuromeres (4 cells). The proximal neurites of these cells are similar in their dorsal and lateral patterns of projection, indicating a serial homology among the three clusters. Members of the mandibular and maxillary clusters have axons projecting into the maxillary nerve, while two additional pairs of axons from the maxillary cluster project into the ventral nerve cord. Members of the labial cluster project to the retrocerebral complex (corpora cardiaca and cephalic aorta) via the nervus corpus cardiaci III (NCC III). The axons projecting into the ventral nerve cord appear to arborize principally in the dorsolateral region of each segmental ganglion; the terminal abdominal ganglion is distinct in containing an additional ventromedial arborization in the posterior third of the ganglion. Quantification of the extractable immunoreactive peptide in the retrocerebral complex by ELISA indicates that PBAN is gradually depleted during the scotophase, then restored to maximal levels in the photophase. Taken together, our findings provide anatomical evidence for both neurohormonal release of PBAN as well as axonal transport via the ventral nerve cord to release sites within the segmental ganglia.Abbreviations A aorta - Br-SOG brain-suboesophageal ganglion complex - CC corpus cardiacum - PBS phosphate-buffered saline - PLI PBAN-like immunoreactivity - TAG terminal abdominal ganglion - VNC ventral nerve cord     

Pigment-dispersing hormone-immunoreactive neurons and their relation to serotonergic neurons in the blowfly and cockroach visual system

Summary The pigment-dispersing hormone (PDH) family of neuropeptides comprises a series of closely related octadecapeptides, isolated from different species of crustaceans and insects, which can be demonstrated immunocytochemically in neurons in the central nervous system and optic lobes of some representatives of these groups (Rao and Riehm 1989). In this investigation we have extended these immunocytochemical studies to include the blowfly Phormia terraenovae and the cockroach Leucophaea maderae. In the former species tissue extracts were also tested in a bioassay: extracts of blowfly brains exhibited PDH-like biological activity, causing melanophore pigment dispersion in destalked (eyestalkless) specimens of the fiddler crab Uca pugilator. Using standard immunocytochemical techniques, we could demonstrate a small number of pigment-dispersing hormone-immunoreactive (PDH-IR) neurons innervating optic lobe neuropil in the blowfly and the cockroach. In the blowfly the cell bodies of these neurons are located at the anterior base of the medulla. At least eight PDH-IR cell bodies of two size classes can be distinguished: 4 larger and 4 smaller. Branching immunoreactive fibers invade three layers in the medulla neuropil, and one stratum distal and one proximal to the lamina synaptic layer. A few fibers can also be seen invading the basal lobula and the lobula plate. The fibers distal to the lamina appear to be derived from two of the large PDH-IR cell bodies which also send processes into the medulla. These neurons share many features in their laminamedulla morphology with the serotonin immunoreactive neurons LBO-5HT described earlier (see Nässel 1988). It could be demonstrated by immunocytochemical double labeling that the serotonin and PDH immunoreactivities are located in two separate sets of neurons. In the cockroach optic lobe PDH-IR processes were found to invade the lamina synaptic region and form a diffuse distribution in the medulla. The numerous cell bodies of the lamina-medulla cells in the cockroach are located basal to the lamina in two clusters. Additional PDH-IR cell bodies could be found at the anterior base of the medulla. The distribution and morphology of serotonin-immunoreactive neurons in the cockroach lamina was found to be very similar to the PDH-IR ones. It is hence tempting to speculate that in both species the PDH-and serotonin-immunoreactive neurons are functionally coupled with common follower neurons. These neurons may be candidates for regulating large numbers of units in the visual system. In the flies photoreceptor properties may be regulated by action of the two set of neurons at sites peripheral to the lamina synaptic layer, possibly by paracrine release of messengers.     

Distribution and characterization of nitric oxide synthase in the nervous system of Triatoma infestans (Insecta: Heteroptera)

The biochemical characterization of nitric oxide synthase (NOS) and its distribution in the central nervous system (CNS) were studied in the heteropteran bug Triatoma infestans. NOS-like immunoreactivity was found in the brain, subesophageal ganglion, and thoracic ganglia by using immunocytochemistry. In the protocerebrum, NOS-immunoreactive (IR) somata were detected in the anterior, lateral, and posterior soma rinds. In the optic lobe, numerous immunostained somata were observed at the level of the first optic chiasma, around the lobula, and in the proximal optic lobe. In the deutocerebrum, NOS-IR perikarya were mainly observed in the lateral soma rind, surrounding the sensory glomeruli, and a few cell bodies were seen in association with the antennal mechanosensory and motor neuropil. No immunostaining could be detected in the antennal nerve. The subesophageal and prothoracic ganglia contained scattered immunostained cell bodies. NOS-IR somata were present in all the neuromeres of the posterior ganglion. Western blotting showed that a universal NOS antiserum recognized a band at 134 kDa, in agreement with the expected molecular weight of the protein. Analysis of the kinetics of nitric oxide production revealed a fully active enzyme in tissue samples of the CNS of T. infestans. This work was funded by the Facultad de Ciencias Biomédicas. Universidad Austral. A.J.N. is supported by the NIH-NIDCD (DC04292). Part of this work was performed at the Arizona Research Laboratories, Division of Neurobiology (Tucson, Arizon, USA) with the support of a Fulbright Research Award to B.P.S.     

Identification of sex in Simmondsia chinensis (Jojoba) using RAPD markers

Simmondsia chinensis (Link) Schneider, a multipurpose dioecious shrub of arid zones, has emerged as a cash crop. It is being cultivated for its seeds which store liquid wax whose properties are similar to spermaceti (Sperm whale oil), a substitute for petro products and precious high-priced lubricants. Jojoba is a slow-growing desert shrub having a male biased (5:1; male:female ratio) population. Since there is no method available to determine the sex at the seedling stage, current investigations have been carried out to generate a sex-specific random amplified polymorphic DNA (RAPD) marker in jojoba which is based on the PCR amplification of random locations in the genome of plant. Of the 72 primers tested, only one random decamer primer, OPG-5, produced a unique ∼1,400 base pairs fragment in male DNA. To validate this observation, this primer was re-tested with the individuals of male and female samples of four cultivars. The unique ∼1,400 bp fragment was present in male individuals of all the four cultivars and completely absent in respective female individuals tested. To the best of our knowledge, this is the first report to ascertain the sex of jojoba plants at an early stage of development of the taxon.