Anatomy of synganglia, including their neurosecretory regions, in unfed, virgin female Ixodes scapularis say (Acari: Ixodidae).

The central nervous system of Ixodes scapularis is fused into a single compact synganglion. The esophagus runs through the synganglion and divides it into supraesophageal and subesophageal parts. The supraesophageal portion contains a single protocerebrum with four pairs of glomeruli, paired optic lobes and cheliceral ganglia, and a single stomodeal bridge. The subesophageal portion contains a centrally located network of commissures and connectives, a pair of palpal ganglia, paired olfactory lobes of the first pedal ganglia, four pairs of pedal ganglia, and a single opisthosomal ganglion. A retrocerebral organ complex (ROC) in close vicinity of the digestive tract, as described in some other tick species, apparently is lacking. Perhaps the function of the ROC is performed by the paired, large, ganglion-like bodies that lie anterolaterad to the cheliceral ganglia. The rind, which is formed from the neuronal somata and glial cells, surrounds the central fibrous core or neuropile. Neurosecretory cells (NSC) are distinct among rind cells due to their large size and concentration of cytoplasmic neurosecretions. NSC are present throughout the synganglion, although the subesophageal portion contains larger groups of these cells. Histological serial sections, stained with Meola's (Trans Am Microsc Soc 89:66-71, '70) paraldehyde fuchsin (PAF) procedure revealed 24 PAF-stained, putative neurosecretory regions in the synganglion of virgin, unfed females. All of these regions appear to be connected and associated with the nearest ganglion and are correspondingly named. Eighteen PAF-positive regions occur in the synganglion. In addition, PAF-negative (green-stained) cells occupy 6 distinct regions in the synganglion of unfed, unmated females.     

Localization of insulin-like immunoreactivity in the synganglion of nymphal and adult Dermacentor variabilis (Acari: Ixodidae)

Immunocytochemical staining based on a peroxidase-antiperoxidase method showed neurosecretory cells (NSC) reactive to bovine insulin in five of 18 paraldehyde fuchsin-positive neurosecretory regions (NSR) in the synganglion of unfed adult Dermacentor variabilis. This is the first report of a neuropeptide in an ixodid tick. The insulin-specific immunoreactive cells included the posterior medial group of the protocerebral center, posterior group of dorsal opisthosomal center, anterior lateral group of the dorso-lateral cheliceral center, dorsal group of the frontal stomodeal center, and anterior group of the ventral palpal center. After feeding and mating, females no longer had immunoreactive cells in three of five NSR found in virgin, unfed females. However, two cells of the posterior group in dorsal opisthosomal center and anterior lateral group of the dorso-lateral cheliceral center remained immunoreactive throughout feeding. Fed, mated males continued to display immunoreactive cells in four of five NSR found in the virgin, unfed males. All developmental stages of nymphs examined had insulin-specitic immunoreactive cells in two of the five NSR found in unfed adults, including two positively stained cells of the posterior group in dorsal opisthosomal center and anterior group of ventral palpal neurosecretory center.     

Role of synganglion in oogenesis of the tick Ornithodoros parkeri (Acari: Argasidae).

The role of the synganglion in oocyte development in Ornithodoros parkeri was investigated by ligation and transplantation experiments. Ligation between legs 2 and 3 to isolate the synganglion from the ovary and ligation between legs 1 and 2 to keep both the synganglion and the ovary in the posterior ends were performed on mated females on different days after feeding. Results show that vitellogenesis was inhibited significantly if the synganglion was separated from the ovary within the first few days after feeding. However, transplantation of synganglia from 3 kinds of donors (unfed virgin, fed virgin, and fed mated females) into the synganglionless posterior portions induced vitellogenesis and oocyte development to final maturation. The supra- and subesophageal parts of the synganglion showed a similar gonadotropic activity after each was transplanted separately into the ligated synganglionless posterior portions. These results indicate that the synganglion produces an egg development stimulation factor (EDSF) that possibly is present in a storage form in unfed and/or fed virgin females in which vitellogenesis has not progressed and is released in females after feeding and mating. However, the characterization of EDSF and precise sites of production and storage await further investigation.     

Effect of 20-hydroxyecdysone on neurosecretory cell activity in femaleHyalomma dromedarii synganglion (Acari: Ixodidae)

Twentyg of 20-hydroxyecdysone (20-he) were applied topically to nymphalHyalomma dromedarii Koch on the day of detachment. In emerging adult females, some neurosecretory cells (nsc) in certain synganglion centers exhibited changes in size and/or neurosecretory material (nsm) shape, distribution and/or quantity. These changes were compared with those normally occurring in untreated unfed, semifed virgin and mated, and engorged females. 20-he effects included (a) accelerating the changes induced by mating and/or feeding in certainnsc, (b) reducing, to various extents,nsc response to mating and feeding, and (c) inducing changes in somensc which do not normally exhibit any changes in untreated females. The results suggest that (a) most femalensc respond more or less similarly to indigenous 20-he, (b) 20-he may have a role as a positive feedback regulator fornsm synthesis and/or release by certainnsc, (c) the response to 20-he may be primarily a function ofnsc location in the synganglion, and/or (d)nsc considered to be of one type may actually belong to different cell types.     

Structure and anatomical relationships of the synganglion in the American dog tick,Dermacentor variabilis (Acari: Ixodiadae)

The synganglion of Dermacentor variabilis Say is a single nerve mass, condensed around the esophagus and within the periganglionic sinus of the ciculatory system. Protocerebral, cheliceral (including stomodeal bridge), and pedipalpal ganglia lie in the pre-esophageal portion of the nerve mass and bear optic, cheliceral, and pedipalpal nerves respectively. The unpaired stomodeal and the recurrent nerve which forms the hyper-esophageal ganglion arise from the stomodeal bridge. Paired primary and accessory nerves to the retrocerebral organ complex have mixed protocerebral-cheliceral origins. Pedal ganglia (including ventral olfactory lobes of pedal ganglia I) and composite opisthosomal ganglion lie in the post-esophageal nerve mass and bear pedal nerve trunks and two pairs of opisthosomal nerves respectively. Internally, the synganglion consists of cellular rind and fibrous core. A welldefined neurilemma with a laminar matrix covers nerve mass and peripheral nerves. The rind contains the somata of ganglionic neurons and ensheathing glial cells and is restricted to the synganglion mass. It is limited by two specialized glial layers, the external perineurium and internal subperineurium. Discrete glomerular formations are present within the protocerebrum and olfactory lobes. Olfactory glomeruli located in pedal ganglia I are associated with a pair of globuli cell groups. Possible physiological relationships between anatomical specializations of the synganglion, extraneural sinuses and circulating hemocytes are considered. The evolutionary significances of condensation in the stomatogastric neuropile regions and throughout the synganglion, together with the simplification and loss of glomerular formations, are discussed.     

Neurosecretory system of the American dog tick,Dermacentor variabilis (Acari: Ixodidae). II. Distribution of secretory cell types,axonal pathways and putative neurohemal-neuroendocrine associations; comparative histological and anatomical implications

Histological observations using specialized techniques reveal neurosecretory cells in 18 centers throughout the rind (cortex) of the central nerve mass or synganglion of Dermacentor variabilis. Many cells contribute to complicated networks of neurosecretory pathways and tracts in pre- and post-esophageal portions of the synganglion. The four types of neurohemal-neuroendocrine associations found in Dermacentor resemble structures found in soft ticks (Argasidae) and in other Arachnida, but are more diverse than those described from any other single species. Neurosecretory terminals are distributed diffusely and in two concentrated associations within the perineurium of the synganglion and major peripheral nerves. Terminals are also distributed in the perineurial layers of lateral segmental organs which lie in the general hemocoel at the level of the pedal nerves. A retrocerebral organ complex surrounds the esophagus at its junction with the midgut. The complex includes dorsal and ventro-lateral lobes (containing neurosecretory terminals and intrinsic secretory cells) and the proventricular (neurohemal) plexus. This plexus seems to be a modified (concentrated) cardioglial association. Cardioglial associations are also formed by the neurosecretory innervation of vascular walls of the dorsal aorta and circulatory sinuses which envelope the synganglion and major peripheral nerves. Inferential considerations of neurosecretory and endocrine interactions in the Acari are based on these anatomical and histological data which also provide the basis for evolutionary considerations of anatomical relationships and specializations in the neurosecretory systems of other Arachnida.     

Ultrastructure of the lateral organs in larvalArgas (Persicargas) arboreus (Ixodoidea: Argasidae)

The ultrastructure of lateral organs (LO) in the larval tickArgas (Persicargas) arboreus is described before and after feeding and up to the 1st day of moulting. Three pairs of LO are associated with three pedal nerves arising from the synganglion. In unfed ticks, each LO is ensheathed by a neural lamella and consists of 6–7 neuronal cell bodies; their cytoplasm is mostly occupied by cisternae of rough endoplasmic reticulm (RER). In fully engorged ticks, the enlarged neuronal cells contain vacuolar cisternae of smooth endoplasmic reticulum (SER), coated vesicles and mitochondria. Golgi bodies are involved in the formation of neurosecretory granules which dominate, with the SER vacuoles, the cell cytoplasm before moulting. The vacuoles, coated vesicles and neurosecretory granules are similar to those found in the vertebrate steroid-secreting cells. Condensing vacuoles may fuse with lysosome-like bodies to form larger ones; these are possibly responsible for the cell breakdown when secretory products are no longer required. Ultrastructural observations of LO suggest that they are neuroendocrine glands and that, in engorged larvae, they may secrete a hormone involved in the control of moulting.     

Immunocytochemical localization of an insulin-like substance in the synganglion of the tickOrnithodoros parkeri (Acari: Argasidae)

Immunocytochemical staining based on the peroxidase-antiperoxidase method has shown that some neurosecretory cells (NSC) in the synganglion of the adult female tickOrnithodoros parkeri react with an antibody to bovine insulin. There are 18 regions of paraldehyde fuchsin-positive NSC of which three regions showed specific insulin-like immunoreactivity: anterolateral cheliceral, anteromedial stomodeal and posterior opisthosomal. Immunoreactivity can also be found in the extracellular surface of the neurilemma of the synganglion. This suggests a possible neurohemal site and release of neurohormone in a diffuse manner.     

Mating, cross-mating and related behaviours of Neoseiulus californicus and Neoseiulus fallacis (Acari: Phytoseiidae)

The pairings of Neoseiulus californicus (McGregor) and Neoseiulus fallacis (Garman) from western North America were monitored for tending by adult males, males in the mating position and oviposition and the activity of female deutonymphs and adults. The N. fallacis × N. californicus (♂ × ♀) tests had fewer males tending the deutonymphs but more in the mating position with new females than the reciprocal test. Afterwards, most of the females appeared gravid and approximately 20% produced an egg. Some eggs did not hatch but others became adult males, which mated with their mothers, but no eggs were produced. F1 males tended and mated with new N. fallacis females which had normal offspring. When held with new N. californicus females, F1 males tended the deutonymphs but were not seen mating and no eggs were laid. The pairings of N. californicus× N. fallacis had more males tending, less in the mating position and the females appeared non-gravid and produced no eggs. When same-species males were added to females held with F1 males for 15–20 days, normal levels and sexes of the progeny were produced. The female and male adults of N. fallacis were more active (ambulatory) than those of N. californicus. In within-species tests, the males had a high activity except while tending and mating, the female deutonymphs were inactive and the just mated females were more active than the ovipositing females. The timing of the tending and mating differed in the cross-pairings. Overall, these and other life-history data show that these two mites are distinct species, but that their males are promiscuous in tending and mating. This revised version was published online in November 2006 with corrections to the Cover Date.     

Cockroach allatostatin-like immunoreactivity in the synganglion of the American dog tick Dermacentor variabilis (Acari: Ixodidae)

Using immunocytochemistry based on a monoclonal antibodyagainst Diploptera punctata allatostatin I and horseradishperoxidase-diaminobenzidine reaction, the presence of allatostatin-likeimmunoreactivity is demonstrated in the synganglion of Dermacentorvariabilis females. The immunoreactive cells are located in theprotocerebral, cheliceral, palpal, stomodeal, postesophageal, and opisthosomalregions of the synganglion. Strongly immunoreactive granules accumulate in theboundary area of the subganglia in the preesophageal part of the synganglion.This suggests that the immunoreactive materials may be released directly fromthere. In addition, a putative neurohemal area is found in the anterior area ofthe opisthosomal ganglion, where abundant immunoreactive materials are stored.Weak immunoreactivity and fewer immunoreactive cells are seen in newly moltedfemales compared with one month old, unfed females. Thus, the immunoreactiveproducts may be depleted during molting and synthesized in females beforefeeding.     

Unusual way of feeding by the deutonymph of Neottialges evansi (Actinotrichida,Astigmata, Hypoderatidae), a subcutaneous parasite of cormorants,revealed by fine structural analyses

The parasitic deutonymphs of hypoderatid mites live within the subcutaneous layer of their avian hosts, where they become greatly engorged despite not having functional mouthparts. The method by which they take up nutrients has been mysterious up to now. Here, we report on the morphology of hypoderatid deutonymphs using scanning and transmission electron microscopy and describe structures that may resolve the mystery. The deutonymph of Neottialges evansi (Hypoderatidae) from the cormorant Phalacrocorax carbo is a simply organized stage lacking both mouthparts and a functional foregut. The structure of midgut and hindgut indicate that they are not capable of processing food. The midgut consists of highly branching flat cells and rarely shows a lumen. Almost the entire space between integument, gut remnants and other organs (synganglion, developing gonads) is filled by huge cells containing protein and glycogen granules and numerous lipid inclusions. The anal opening is minute. The structure of the cuticle and epidermis suggests that nutrients are not absorbed through the general integument. Thus the two main existing hypotheses about feeding modes in hypoderatid deutonymphs, anal vs. integumentary food absorbtion, are not supported. We suggest instead that two pairs of genital papillae showing peculiar microanatomical features are actively involved in movement of liquid materials between host and mite and most probably are the nutrient‐intake organs. J. Morphol. 277:1368–1389, 2016. © 2016 Wiley Periodicals, Inc.     

The subgenus Persicargas (Ixodoidea: Argasidae: Argas). 22. The effect of feeding on hormonal control of egg development in Argas (Persicargas) arboreus

The blood-meal is essential to complete ova development by supplying nutrients and by stimulating hormone production in mated female Argas (Persicargas) arboreus. Within 3 days after feeding, the hormone is synthesized in the nerve ganglion and afterward is released into the hemolymph. Isolating the ovaries by ligation from the nerve ganglion during the hormone synthesis period interfered with ova development. Injecting an extract of nerve ganglia from 3-day-fed, mated females and of hemolymph from 4-day-fed, mated females into mated, recently fed females induced the same degree of ova development in their isolated ovaries as in fed, mated control females. Injecting nerve ganglion extract from 3-day-fed, mated females into mated, unfed females did not induce ova development.     

Effects of host-plant quality on male two-spotted spider mite (Acari: Tetranychidae) mate location and guarding behavior

Effects of host-plant quality on two-spotted spider mite,Tetranychus urticae Koch, mate location and guarding behaviors were described using a no-choice bioassay. Males and quiescent deutonymphs were collected from lima bean leaves of one of two host qualities. High-chlorophyll (HC) leaves had been infested with spider mites for 6–10 days, while low-chlorophyll (LC) leaves had been infested for>21 days. Three parameters of maleT. urticae guarding behavior were quantified: approach arrestment, and arrestment duration. HC males approached quiescent deutonymphs more often than did LC males, even though host quality of females had no effect on male approach frequency. HC males were arrested more frequently by HC quiescent deutonymphs than were LC males, while LC males were arrested more often by LC females than were HC males. However, a different pattern was observed for arrestment duration. HC males were arrested for twice as long by LC quiescent deutonymphs than by HC females, while the LC-male arrestment durations elicited by HC and LC females did not differ. These results show that host-plant quality affectsT. urticae intersexual communication, in terms of both the female signal and the male response. Whether the differing male responses observed in this study indicate alternativeT. urticae mating strategies or are incidental by-products of host-induced physiological changes remains to be determined.     

Ultrastructure of the synganglion in the larval tickAmblyomma americanum (Ixodoidea: Ixodidae)

The synganglion in the larvalAmblyomma americanum consists of a ganglionic mass pierced by the oesophagus. The nervous tissue consisting of an outer cortex and an inner neuropile is surrounded by an external neurilemma. The cortex comprises perineurium glial cells and neurosecretory and non-neurosecretory neuronal cell bodies. The neuropile consists of nerve fibres ensheathed by glial cells. The entire ganglionic mass is enclosed within a sinus of the circulatory system. No investigations using electron microscopy appear to have been made on the synganglion in the tick larval stage.     

Muscles and innervation of the genital and postgenital abdominal segments of the female american cockroach Periplaneta Americana (L.) (Dictyoptera : Blattidae)

The locations of skeletal muscles in abdominal segments 7–10 of female Periplaneta americana (Dictyoptera : Blattidae) are described, and the action of some of those attached to the gonapophyses is hypothesized. The muscles are innervated from a terminal synganglion, a composite formed by fusion of embryonic neuromeres of abdominal segments 7–11. Pathways of the 5 pairs of segmental nerves and 3 pairs of transverse nerves that issue from the synganglion are documented. In addition to supplying skeletal muscles, certain of the nerves can be traced to the oviducts, spermatheca, colleterial glands, ventral glands, hindgut, and apparently, to sensilla of the cerci, gonapophyses, paraprocts, tergum, pleura, and sternum. Homologous relationships of the nerves are proposed, and the observations are compared to those reported by others who have, for the most part, examined males only. Putative neurosecretory somata occur in abdominal segments 7 and 8, at the junction of the transverse and segmental nerves. The association may be comparable to the “link nerve” complex described by others.     

Effect of juvenile hormone (III) from the hostApis mellifera (Insecta: Hymenoptera) on the neurosecretion of the parasitic miteVarroa jacobsoni (Acari: Mesostigmata)

In the parasitic bee miteVarroa jacobsoni neurosecretory material of ten different cell groups in the synganglion was examined by victoria blue staining after oxidation. Important periods in the life of the mite correspond to definite patterns of filling in of the neurosecretory cell groups. Material of cell group 1, which is situated in the medial protocerebral area of the synganglion, supports molting and oviposition. Secretion of cell group 2, which lies between the two ganglionic masses, seems to be necessary during the whole reproductive process. Cell group 8, located at the opisthosomal ganglion where the genital nerves leave the subesophageal ganglion, seems to be mainly responsible for the initiation of reproduction. Juvenile hormone (JH_III) in the hemolymph of the bees acts on the mites as a release mechanism for reproductive behavior with entry into the brood cell of the bee. Mites on bees with a low JH_III titer that are sprayed with external JH_III show a similar neurosecretion pattern to mites parasitizing bees with a high JH_III titer. The influence of external JH_III on the degree in which the three cell groups are filled with neurosecretion is discussed with respect to the regulatory mechanisms. In this parasite-host relationship there is a clear synchronization of the reproductive cycle of the mite with the metamorphosis and hormonal regulation of the bee.     

The vasopressin-like immunoreactive (VPLI) neurons of the locust,Locusta migratoria. I. Anatomy

Summary Antiserum to arginine-vasopressin has been used to characterise the pair of vasopressin-like immunoreactive (VPLI) neurons in the locust. These neurons have cell bodies in the suboesophageal ganglion, each with a bifurcating dorsal lateral axon which gives rise to predominantly dorsal neuropilar branching in every ganglion of the ventral nerve cord. There are extensive beaded fibre plexuses in most peripheral nerves of thoracic and abdominal ganglia, but in the brain, the peripheral plexuses are reduced while neuropilar branching is more extensive, although it generally remains superficial. An array of fibres runs centripetally through the laminamedulla chiasma in the optic lobes. Lucifer Yellow or cobalt intracellular staining of single VPLI cells in the adult suboesophageal ganglion shows that all immunoreactive processes emanate from these two neurons, but an additional midline arborisation (that was only partially revealed by immunostaining) was also observed. Intracellularly staining VPLI cells in smaller larval instars, which permits dye to reach the thoracic ganglia, confirms that there is no similar region of poorly-immunoreactive midline arborisation in these ganglia. It has been previously suggested that the immunoreactive superficial fibres and peripheral plexuses in ventral cord ganglia serve a neurohaemal function, releasing the locust vasopressin-like diuretic hormone, F₂. We suggest that the other major region of VPLI arborisation, the poorly immunoreactive midline fibres in the suboesophageal ganglion, could be a region where VPLI cells receive synaptic input. The function of the centripetal array of fibres within the optic lobe is still unclear.Abbreviations AVP arginine vasopressin - DIT dorsal intermediate tract - FLRF Phe-Leu-Arg-Phe - FMRF-amide Phe-Met-Arg-Phe-amide - LDT lateral dorsal tract - LVP lysine vasopressin - MDT median dorsal tract - MVT median ventral tract - SEM scanning electron microscopy - SOG suboesophageal ganglion - VIT ventral intermediate tract - VNC ventral nerve cord - VPLI vasopressin-like immunoreactive     

Cytophysiological study of neurosecretory and pheromonal influences on sexual development in Ophryotrocha puerilis (Polychaeta,Dorvilleidae)

Summary

Prominent secretory nerve endings are found at the posterior margin of the supraesophageal ganglion in the protandric polychaete, Ophryotrocha puerilis. Solitary juveniles developing as primary males, and then as females, accumulate neurosecretory material in the nerve endings which thereby swell and become filled with granules. Females maintained in mass culture have similar terminals, whereas in secondary males (males which had been females before), these axon terminals are very small and contain no material. When such males are isolated, they accumulate neurosecretory material within the nerve endings and become females. When formerly isolated females are put together, their stores of neurosecretory material are rapidly discharged. Subsequently they lay egg masses and switch to the male state. These effects are mediated by a pheromone released during social contact of formerly isolated females. The complexity of the relationship between neurosecretory activity and sexual state is indicated by the situation in animals maintained in pairs, when both male and female partners have swollen nerve endings packed with secretory material.     

Indirect effects of phytochemicals on offspring performance of Queensland fruit fly,Bactrocera tryoni (Diptera: Tephritidae)

Phytochemical lures such as methyl eugenol (ME) and cue‐lure are used in the management of Bactrocera fruit flies for monitoring and control. These lures are not just attractants, but also trigger physiological changes in males that lead to enhanced mating success. Additionally, in the cue‐lure‐responsive Bactrocera tryoni, females mated with lure‐fed males exhibit changes in fecundity, remating receptivity and longevity. While the lures show current generation effects, no research has been carried out on possible multigenerational effects, although such effects have been hypothesized within a ‘sexy‐son’ sexual selection model. In this study, we test for indirect, cross‐generational effects of lure exposure in F1offspring of B. tryoni females mated with cue‐lure‐fed, zingerone‐fed and lure‐unfed (=control) males. The F1 attributes we recorded were immature development time, immature survival, adult survival and adult male lure foraging. No significant differences were found between treatments for any of the three life‐history measurements, except that the offspring sired by zingerone‐fed males had a longer egg development time than cue‐lure and control offspring. However, indirect exposure to lures significantly enhanced the lure‐foraging ability of F1 adult males. More offspring of cue‐lure‐fed males arrived at a lure source in both large flight cages and small laboratory cages over a 2‐h period than did control males. The offspring of zingerone‐fed males were generally intermediate between cue‐lure and control offspring. This study provides the first evidence of a next generation effect of fruit fly male lures. While the results of this study support a ‘sexy‐son’ sexual selection mechanism for the evolution of lure response in Bactrocera fruit flies, our discussion urges caution in interpreting our results in this way.