The salivary glands of the cockroach Nauphoeta cinerea (Olivier)

The innervation of the salivary gland of the cockroach Nauphoeta cinerea (Olivier) has been investigated with the use of light and scanning electron microscopy. Light microscopy of methylene blue stained glands reveals the presence of a dual innervation arising from the ventral nerve cord and the stomodeal nervous system; the principal innervation is that from the ventral nerve cord which passes to the gland via the reservoir ducts. Branches of these nerves form a plexus on the acinar surface, the axons of which exhibit swelling at irregular intervals. The presence of this surface plexus and the axonal swellings was confirmed by scanning electron microscopy both in normal glands and in those in which the basal lamina had been removed by means of an HCl-collagenase digestion method. No acinar plexus was seen to be formed by branches of the stomatogastric nerve that were associated with the gland. However, other branches of this nerve were clearly connected with a complex network of multipolar neurones on the surfaces of the anterior regions of both salivary reservoirs.     

The adult cervicothoracic musculature of the cockroach, Nauphoeta cinerea (Olivier)

The cervicothoracic musculature of the adult cockroach, Nauphoeta cinerea (Olivier) is described for the first time. The adult thoracic ventral intersegmental muscles are compared with those of the nymph and of the adult cockroach, Periplaneta americana (Linnaeus).     

Histological and cytological studies on the fat body of the cockroach Nauphoeta cinerea during the first reproductive cycle

Summary The central fat body of the ovoviviparous cockroach Nauphoeta cinerea was studied during the first reproductive cycle of the female by means of light microscopy, autoradiography and electron microscopy. Comparative studies in larval stages were also undertaken. The fat body of Nauphoeta contains a large amount of lipid droplets and the remaining cytoplasm is very scarce. The cytological cyclicity of the fat body is consistent with the known biochemical rhythms of vitellogenin production. The proteosynthetic apparatus appears about 3 days after imaginal ecdysis, along with vitellogenin. The ribosomal endoplasmic reticulum (RER) shows a tremendous increase by the 7th day of the first cycle. The most active period of vitellogenin production lasts from day 7 to day 12. The proteosynthetic apparatus then returns to an inactive stage and disappears. This inactive condition lasts to the end of the gestation period. The autoradiographic results are consistent with the cytological features.Work carried out under the scientific direction of Prof. M. Lüscher of the University of Bern and supported in part by a grant from the Swiss National Science Foundation (No 3. 633.71).     

Changes in pheromone production, release, mating behaviour and reproductive ability of the gamma-irradiated cockroach Nauphoeta cinerea (Olivier).

Mature males of Nauphoeta cinerea produce a sex pheromone 'seducin' which has short-range effects in attracting mature females of the same species. Exposure of newly-emerged adult males to 3.5, 7, 14 or 21 krad of gamma-radiation decreased their life expectancy and affected their mating behaviour. Bioassay of dichloromethane extracts of males showed that radiation doses (14 krad) sufficient to induce sterility did not affect the ability to produce pheromone but significantly reduced the release of pheromone by inhibiting wing-raising. The sterile-male technique using males sterilized by ionizing radiation in air may not be the method of choice for control of Nauphoeta cinerea.     

Chilling-injury and disturbance of ion homeostasis in the coxal muscle of the tropical cockroach (Nauphoeta cinerea)

Adults of warm- and cold-acclimated tropical cockroaches, Nauphoeta cinerea were exposed to low temperatures of 0 or 5 degrees C for various time intervals (hours to days). Development of chilling-injury (defects in crawling and uncoordinated movements) and mortality during the exposure were assessed and correlated with the changes in concentrations of metal ions (Na(+), K(+) and Mg(2+)) in the haemolymph and coxal muscle tissue. Warm-acclimated insects entered chill-coma at both low temperatures. In their haemolymph, the [Na(+)] and [Mg(2+)] linearly decreased and [K(+)] increased with the increasing time of exposure. The rate of concentration changes was higher at 0 than at 5 degrees C. The concentration changes resulted in gradually dissipating equilibrium potentials across the muscle cell membranes. For instance, E(K) decreased from -49.8 to -20.7 mV during 7 days at 5 degrees C. Such a disturbance of ion homeostasis was paralleled by the gradual development of chilling-injury and mortality. Most of the cockroaches showed chilling-injury when the molar ratio of [Na(+)]/[K(+)] in their haemolymph decreased from an initial of 4.4 to 2.1-2.5. In contrast, the cold-acclimated cockroaches did not enter chill-coma. They maintained constant concentrations of ions in their haemolymph, constant equilibrium potentials across muscle cell membranes and the development of chilling-injury was significantly suppressed at 5 degrees C for 7 days.     

Developmental constraints on the mode of reproduction in the facultatively parthenogenetic cockroach Nauphoeta cinerea

Considerable work in evolutionary biology has focused on the question of why sex persists. Both advantages to sex and constraints limiting a return to asexual reproduction are hypothesized to maintain sex once it evolves. Developmental constraints would limit asexual reproduction from a sexual species if it were difficult for females to switch from making eggs that do not develop without fertilization to making zygotes that are capable of developing in the absence of fertilization. Nauphoeta cinerea is an ovoviviparous cockroach in which some females are capable of switching from a sexual mode of reproduction to an asexual mode when isolated from males. Yet, while facultative parthenogenesis can occur in individuals, few females make the switch. Thus, this cockroach provides an ideal system for examining the potential role of developmental constraints in maintaining sex. Here we compare the cytogenetics and embryonic development of sexual and parthenogenetic offspring in N. cinerea. We find that deviations from normal ploidy levels are associated with abnormal development. All viable N. cinerea embryos exhibit typically hemimetabolous insect embryogenesis. Although there is no variation among embryos in development within a sexually produced clutch, we see extreme variation in asexually derived clutches. These results suggest that developmental constraints limit the success of asexual reproduction in this facultatively parthenogenetic cockroach. Our data further suggest that the specific constraint occurs in the switch from a meiotic mode of reproduction requiring fertilization to diploid zygotes that develop in the absence of fertilization.     

Demonstration of a voltage dependent calcium current in follicles of the cockroach Nauphoeta cinerea

Summary

The electrical properties of vitellogenic cockroach follicles have been studied using a two-electrode voltage-clamp technique. The resting potential of freshly isolated follicles was usually between ?30 mV and ?45 mV. A voltage-dependent inward current could be activated when the follicles were placed in a medium containing high concentrations of either Ca²⁺ or Ba²⁺. Maximal current amplitudes were 0.8μA in a medium containing 30 mM Ca²⁺ and 2 μA in 30 mM Ba²⁺. Maximal amplitudes could be elicited with depolarizing pulses to about +15 mV. The steady-state inactivation curve indicated half maximal current at a holding potential of about ?20 mV. Co²⁺, Ni²⁺ and Mn²⁺ inhibited the divalent cation currents in a concentration dependent manner. Half maximal inhibition was observed at about 3 mM concentration for each of the inhibitory cations.     

Vitellogenesis in the cockroach Nauphoeta cinerea: Separation of two classes of ovarian binding sites and calcium effects on binding and uptake

Two classes of vitellogenin binding sites with K_d-values of 7.3 nM and 290 nM were observed in follicle-membrane preparations of the cockroach Nauphoeta cinerea using a membrane-binding assay at pH 8. Separation of follicle cells and basal laminae from oocyte membranes prior to binding studies showed that the fraction consisting of follicle cells and basal laminae (FC/BL) contained high-affinity binding sites for vitellogenin (K_d=16.6 nM), whereas loweraffinity binding sites (K_d=200 nM) were found in the oocyte membrane fraction. The concentration of Ca²⁺ had a distinct effect on vitellogenin binding and uptake: maximal binding to the oocyte membrane fraction was observed at 0.3 mM Ca²⁺ and to the FC/BL fraction at 10 mM, whereas uptake of vitellogenin by oocytes in vitro was highest at 4 mM Ca²⁺. The calcium ionophore A23187 decreased vitellogenin uptake. This effect of A23187 could be counteracted by the calcium chelator Quin2. A hypothetical model for the uptake of vitellogenin into follicles of Nauphoeta cinerea is suggested.     

Solubilization, identification, and localization of vitellogenin-binding sites in follicles of the cockroach, Nauphoeta cinerea

Binding sites for vitellogenin were solubilized and analyzed either with a filter assay or with ligand blotting. We tested sodium dodecylsulfate (SDS), Chaps, octyl-beta-D-glucoside, and sodium deoxycholate and found SDS and sodium deoxycholate to be most effective in solubilizing both high and low molecular weight binding sites. In the filter assay the sodium deoxycholate extracts, but not the SDS extracts, maintained binding activity after dilution of the solubilizer below its critical micellar concentration. In ligand blotting we consistently observed, in vitellogenic follicles, binding sites with an apparent Mr of approximately 200,000, 35,000, and three closely spaced bands between 14,000 and 20,000. Binding of vitellogenin to all binding sites was suppressed in the presence of the drug suramin. Analysis of corpora lutea and oothecae as well as of ovariole sheath, follicle cell/basal lamina, and oocyte plasma membrane preparations showed that the 35 and 14-20 kDa binding sites are located in the outer follicle compartments, and the 200 kDa binding site in the oocyte plasma membrane. In the latter we occasionally also observed binding sites with an apparent Mr of approximately 150,000, 95,000, 67,000 and 30,000, particularly at stages after ovulation. The 35 and 14-20 kDa binding sites, as visualized in stained gels and in ligand blotting, are rather abundant and were also seen in several other male and female tissues of Nauphoeta and even in other species. They also bound other 14C-labeled hemolymph proteins and thus appear to be rather unspecific. As binding analysis with nonsolubilized and sodium deoxycholate-solubilized membranes revealed that the quantity of vitellogenin bound by binding sites of the outer follicle compartments was low, it is conceivable that the abundance of the 14-20 kDa and 35 kDa binding sites in ligand blotting is merely an effect of SDS and does not reflect the in vivo situation. We suppose that the 200 kDa binding site of the oocyte plasma membrane represents the vitellogenin receptor involved in endocytosis.     

Variations in skinfold thickness during de-acclimatisation and re-acclimatisation to high altitude. Relation to body fat content

Skinfold thickness, body weight, body water, anthropometric measurements and segment volumes were determined in 28 young and healthy Indian soldiers on return to Delhi (200 m) after staying for more than 24 months at high altitude (3500 m). The measurements were made on the 2nd day and after 3 weeks. Ten subjects were then randomly selected from this group and returned by air to the high-altitude station, and the measurements were repeated on the 3rd and 12th day of their reinduction. Though body weight and total body water increased marginally on transfer to the lower altitude, body density remained more or less unchanged. There were significant increases in the thickness of skinfolds, even when body density had increased. During this period hand and foot volumes decreased significantly. Despite significant increases in thoracic skinfold thickness, the torso volume decreased slightly. On returning to high altitude, the soldiers lost body weight, were hypohydrated and showed reduced skinfold thickness. Fat losses calculated on the basis of reduction in skinfold thickness were far in excess of those calculated from losses in body weight and in total body water. As the reduced skinfold thickness was unrelated to changes in body water content at high altitude, it seems that such reductions are due to redistribution of blood in the skin. From the results of these investigations it is concluded that variations in skinfold thickness during acclimatisation to high altitude do not accurately represent the changes in body fat content.     

Histological and cytological studies on the ovary of Nauphoeta cinerea (Blattaria,Oxyhaloidea) during the first reproductive cycle

Histological studies were performed on the ovary of the ovoviviparous cockroach Nauphoeta cinerea during the first reproductive cycle by means of optical microscopy and histoautoradiography, and electron microscopy. The oöcyte chamber is composed of follicle cells, the oöcyte and a layer of symbiotic bacteria at the level of the microvillous border of the oöcyte. The first reproductive cycle begins with a short inactive period preceding the appearance of vitellogenin. During this period, the follicular epithelium achieves its development by a mitotic flare. From the 3rd day on, vitellogenin is synthesized by the fat body and large intercellular spaces appear between the follicular cells, in conjunction with a rapid growth of the oöcyte, which takes up selectively the vitellogenin by means of pinocytotic vesicles. These coalesce to give the yolk globules. Along with these phenomena, the proteosynthetic apparatus and its activity in the follicular cells increase slowly. After about the 12th day, the intercellular spaces disappear and the follicular epithelium which has now a very well developed proteosynthetic apparatus, begins to synthesize and lay down the egg membranes. After ovulation, the empty oöcyte chamber collapses and the follicular epithelium shows rapid degeneration processes (large cytolysosomes) that destroy the chamber completely during the gestation period. At the beginning of the 2nd cycle, there only remain a cell or two of the previous follicular epithelium and a very large annular piece of basement membrane.