Anatomical and physiological characteristics of individual neurones in the central antennal pathway of insects

Signals of tens up to hundreds of thousands of (mostly olfactory) receptor cells on an insect antenna are switched to a comparatively low number of neurones in the antennal lobe of the deutocerebrum in circumscribed units of neuropile, the glomeruli. Each glomerulus is connected via its output neurone to two separate neuropiles (calyces of mushroom body, and lateral lobe) of the protocerebrum. Local interneurones interconnect between the glomeruli. Certain modes of convergence between receptors and central neurones provide for a very high sensitivity of the latter to certain odours and their sensitivity for complex odour stimuli, and in many cases for a marked multimodality. Anatomical and physiological data are given especially for pheromone sensitive neurones and their projections.     

Location and major postembryonic changes of identified 5-HT-immunoreactive neurones in the terminal ganglion of a cricket (Acheta domesticus)

Summary In the terminal ganglion of the cricket, Acheta domesticus, the somata of certain interneurones and efferent neurones consistently react to 5-HT immunohistochemistry. There are serially homologous pairs of bilateral interneurones seen in the neuromeres of the 7th to the 10th segment and hindgut neurones with their somata located at the posterior median end of the ganglion. In adult crickets, pairs of large efferent neurones with lateral somata supply specific genital muscles in the 8th and the 9th segment of females. In males, only one pair of these efferent neurones supplies genital muscles of the 9th segment only. These identified 5-HT-immunoreactive neurones are not detected in larval crickets before development of the genital apparatus.     

Choline acetyltransferase-like immunoreactivity in the brain of Drosophila melanogaster

Summary Using a monoclonal antibody selective for the acetylcholine (ACh)-synthesizing enzyme choline acetyltransferase (ChAT) of Drosophila melanogaster we find ChAT-like immunoreactivity in specific synaptic regions throughout the brain of Drosophila melanogaster apart from the lobes and the peduncle of the mushroom body and most of the first visual neuropile (lamina). Several anatomically well-defined central brain structures exhibit particularly strong binding. Characteristic differential staining patterns are observed for each of the four neuromeres of the optic lobes. Cell bodies appear not to bind this antibody. The prominent features of the distribution of ChAT-like immunoreactivity are paralleled by the distribution of acetylcholine hydrolyzing enzymatic activity as revealed by histochemical staining for acetylcholine esterase (AChE). These results are discussed in comparison with published data on enzyme distribution, choline uptake and ACh receptor binding in the nervous system of Drosophila melanogaster.     

Pattern formation in fragmented eggs of the short germ insect Schistocerca gregaria

Summary The effect of transverse fragmentation on the segment pattern of the short germ embryo of the locust Schistocerca gregaria has been investigated at two stages subsequent to the formation of the germ anlage. Following fragmentation both anterior and posterior partial embryos were observed, although rarely in a single egg. Anterior partial patterns usually terminated with a segment visible at the time of fragmentation or with the next segment due to appear. Posterior partial patterns began with a wide range of segments depending on the level of fragmentation.Anterior and posterior partial patterns developing in a single egg were usually not complementary and the segments missing sometimes included some segments visible when the embryo was fragmented. Non-complementary patterns resulted following fragmentation in all regions, while complementary patterns only occurred after fragmentation in the visibly-segmented region.The results suggest that following fragmentation isolated posterior portions of the embryo continue to form segments, while isolated anterior regions usually do not. This effect could result from variable damage to an existing pattern of unequally-sized segment primordia, or from the disruption of a process of sequential segmentation in the elongating posterior region of the embryo. The results are broadly compatible with the progress zone model proposed by Summerbell et al. (1973).     

Estimation of the stage-specific survival rate in the insect population with overlapping stages

An application ofHokyo andKiritani 's method (1967) was attempted to estimate the stage specific survival rates of the population with overlapping stages. This method can be written as follows assuming a constant daily survival rate (K) throughout the life: where, and F refer respectively to the total incidence of ith instar nymphs and that of individuals after ith instar inclusive, and α_i refers to the developmental period of ith instar. Application of this model to caged and natural populations of the southern green stink bug, Nezara viridula, was made to test its validity. The estimates of the initial number of successive stages obtained from the present method were compared with those fromRichards andWaloff 's method (1954) for the caged populations of 1st, 2nd and 3rd generations. The superiority of the present method to theRichards andWaloff 's in estimating adult numbers was shown in all the generations examined. When different daily survival rates are involved in the course of population decrease, application of the revised method proposed byHokyo andKiritani (1967), gives much reliable estimate as compared with one before correction. The present method is useful in constructing life table of such species as scale insects which complete their life cycle within a defined space, but their successive stages overlap considerably.     

Natural mortality at different population densities of a pine shoot moth,Evetria cristata

A field population of Evetria cristata was studied in 10 plots in 1962 and in 6 plots in 1963. These plots were divided into 2 or 3 groups of different population levels of the shoot moth in respective years. The survival of the insect was then analysed in these different groups of plots. The survival rate of E. cristata from eggs to adults in the first generation was found always higher in the group with low population density, which indicates the existence of some factors that affect the population more severely when the insect is more abundant. Lissonota evetriae and Pediobius sp. seemed to have killed more proportion of the hosts where the shoot moth density was high. However, the total effect of the all natural enemies was not always great in the plots with high density of the moth. The survival of the second generation of the moth in 1963 was observed to be much higher at any population level than in the other generations.     

Insect capture and growth of the insectivorous Drosera rotundifolia L.

Summary Rates of insect capture increased with leaf area in the insectivorous plant Drosera rotundifolia, and growth of new leaves was related to insect capture. However, increased leaf growth was counterbalanced by leaf abscission which was in turn related to insect capture and leaf growth. Leaf loss equaled leaf growth in plants having natural rate of insect capture. A large proportion of the nitrogen gain from prey was stored in the hypocotyl; it was estimated from feeding experiments that about 24% to 30% of the nitrogen stored in the hypocotyl after winter originated from insect capture in the previous season. The effect of insect capture is discussed in relation to the life cycle of Drosera.     

The association of proctolin with a ventral abdominal muscle of Locusta migratoria

The association of proctolin with the external ventral protractor muscle of the VIIth abdominal segment (M234) of Locusta migratoria was investigated using immunohistochemistry and RP-HPLC in conjunction with the sensitive locust oviduct bioassay. Immunohistochemistry of whole-mount tissues revealed two proctolin-like immunoreactive axons in N2B_2b1 (the nerve branch which innervates M234) as well as immunoreactive processes and varicosities on the surface of M234. Immunogold staining of M234 demonstrated that the proctolin-like immunoreactivity was present in electron-dense granules in its motor terminals. A material indistinguishable from proctolin and with proctolin-like bioactivity co-eluted with authentic proctolin on two different RP-HPLC systems. Bath application of proctolin at concentrations greater than 10^-11 M resulted in a dose-dependent increase in the neurally-evoked fast twitch amplitude and duration of M234. Concentrations greater than 10^-9 M resulted in a dose-dependent increase in basal tonus of M234. These results indicate that proctolin, or a peptide very similar to proctolin, is present in the motor innervation of M234 and acts as a cotransmitter and/or neuromodulator at this typical fast skeletal muscle.Abbreviations M234 external ventral protractor muscle of the Vllth abdominal segment - RP-HPLC reverse-phase high pressure liquid chromatography - TFA trifluoroacetic acid