Circadian Activity Rhythm of the House Fly Continues after Optic Tract Severance and Lobectomy

Under constant conditions, locomotor activity in about 50% of 63 adult Musca domestica continued to be rhythmic after bilateral severance of optic tracts or bilateral lobectomy. Apparently, the optic lobes of Musca do not contain the oscillator for rhythmic control of locomotor activity as has been proposed for other insects. In 20% of the individuals, several circadian components of activity rhythms were found after operation indicating a role of the optic lobes in the coupling of oscillators. The remaining 30% of the flies with severed optic tracts appeared to be arrhythmic. Most of these flies had vacuolized tissue in the central brain. However, disruption of rhythmicity did not correlate with a common pattern of degeneration. Therefore no conclusions can be drawn as to the localization of the circadian control of locomotor activity in the brain. Flies showing an arrhythmic activity pattern could still be synchronized by LD cycles. Activity did not occur solely during the light period as is the case in controls; but was phase delayed by about 6 hr towards the dark period. Since all flies with severed optic tracts could be synchronized by LD cycles, Musca domestica must possess extraocular photoreceptors.     

Walking on ashes: insect trace fossils from Laetoli indicate poor grass cover associated with early hominin environments

More than 4000 insect trace fossils collected in recent years from Pliocene deposits at Laetoli in northern Tanzania provide new insights on early hominin palaeoenvironments. These trace fossils include: Fictovichnus gobiensis, Coprinisphaera murguiai, C. kheprii, Coprinisphaera ispp., Quirogaichnus isp., Teisseirei linguatus isp. nov., Celliforma ritchiei isp. nov., C. spirifer, C. germanica, C. cfr. curvata, Celliforma ispp., Rosellichnus isp., Vondrichnus planoglobus, Laetolichnus kwekai igen. et isp. nov. and Krausichnidae indet. They reveal that at least one species of moth, three dung beetles and five other coleopterans, nine taxa of solitary bees, and an indeterminate number of taxa of termites inhabited the Lower Laetolil environments. The Upper Laetolil environments, which have yielded a rich diversity of vertebrate fossils, including the early hominin Australopithecus afarensis and its putative footprints, supported several taxa of termites, one dung beetle, five other coleopterans, and eleven taxa of bees. The Upper Ndolanya environments, which have yielded the hominin Paranthropus aethiopicus, record four taxa of dung beetles, four other coleopterans, and two taxa of bees. The record of larval mortality and lack of intruder activity, revealed by the absence of emergence and intruder traces, may be associated with the anoxic/hypoxic conditions caused by the instantaneous burial of soils under thick volcanic ashes. The record of the Celliforma Ichnofacies in the Upper Laetolil environments indicates the dominance of shrubland to woodland with limited grass cover. This is supported also by the absence of Coprinisphaera, which suggests a scarcity of fresh grasses and a low abundance of large mammal grazers.     

The Earth’s Magnetic Field and Visual Landmarks Steer Migratory Flight Behavior in the Nocturnal Australian Bogong Moth

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Extensive chromosome aberrations inSpiroplasma citri strain BR3

Genetic variations in the plant pathogen,Spiroplasma citri strain BR3, were characterized through physical genome mapping of the original isolate, BR3-3X, and two derivatives, BR3-T and BR3-G, obtained after several years of different maintenance conditions. BR3-T was transmitted from plant to plant via its natural insect vector, the leafhopperCirculifer tenellus, while BR3-G was maintained only in plants by periodic grafting and has lost its ability to be insect transmitted. By pulsed field gel electrophoresis (PFGE) analysis and DNA hybridization, extensive changes in chromosomal DNA restriction patterns relative to the parent, BR3-3X, were observed in both BR3-T and BR3-G, each of which also had a larger genome size than the parent line. Genetic organization was relatively conserved between BR3-T and BR3-3X. In contrast, a large chromosomal inversion and deletions of approximately 10 kb near each of the inversion borders were observed in BR3-G. One of the deletions, which included several possibly functional genes, was closely linked to a SpV1-related transposase gene. The locations of the deletion borders were also determined. The results of this study demonstrated remarkable genome instability of spiroplasmas.     

Noctuidonema dibolia n. sp. (Aphelenchida: Acugutturidae), an Ectoparasite of the moth Mocis latipes (Lepidoptera: Noctuidae)

Noctuidonema dibolia n. sp., an ectoparasite of adults of the noctuid moth Mocis latipes (Guenée) is described. The differentiating characters are a club-shaped body with a subterminal vulva in the female, spicules with a reduced matrix and sheath and closely apposed dorsal and ventral arms in the male, very long stylet and conus, moderately prominent stylet knobs, a bluntly rounded head, and a large renette cell in both sexes. Lateral fields, rectum, anus, bursa, and gubernaculum are absent. Noctuidonema dibolia differs from the other species of the subfamily Noctuidonematinae in the size and robustness of the body, the length of the stylet and conus, the length of the tail, and the shape of the spicules.     

Colorado potato beetle resistant somatic hybrid potato plants produced via protoplast electrofusion

Leptines are natural glycoalkaloids found only in certain selections of the wild potato speciesSolanum chacoense. These rare glycoalkaloids have been identified to be phytochemical defensive agents against insect herbivores such as the Colorado potato beetle (CPB). In an attempt to introduce this CPB resistance into the cultivated potatoS. tuberosum, interspecific somatic hybrid plants were developed between a dihaploid ofS. tuberosum and a high leptine-producing germplasm selection ofS. chacoense. The somatic hybrid was fused using protoplast electrofusion and regeneration techniques. Selection of interspecies fusion cell lines was based on hybrid vigor in protoplast-callus (p-callus) growth, on shoot regeneration from p-calli, and on characteristic appearance of anthocyanin pigment. This selection system was highly efficient and 12 of 13 fully regenerated plants were identified as somatic interspecies hybrids, as determined by the analyses of morphologic biochemical, and isozyme markers. In vitro insect bioassays demonstrated that the hybrids averaged a threefold reduction in leaf consumption by the CPB when compared to cultivated potatoes.     

PBAN-induced sex pheromone biosynthesis in Heliothis peltigera: Structure,dose, and time dependent analysis

A structure-activity relationship study of Hez-PBAN was performed with respect to its pheromonotropic activity, using Heliothis peltigera as the test animal. The activity of N- and C-terminally derived sequences was examined in a time- and dose-dependent mode. Using a variety of Hez-PBAN-derived fragments at two doses (1 and 10 pmol) and at different times post-injection (5–120 min), we were able to demonstrate that peptides lacking 12 and 16 amino acids from their N-terminus are as potent as the full length PBAN, and that the C-terminally derived hexapeptide was capable of stimulating sex pheromone production to a similar extent as PBAN 1–33NH₂, when its activity was analyzed at shorter post-injection times. Within the C-terminal sequence, the amide was found to play a crucial role. In addition, it was observed that the region between amino acids 9 and 13 is important for the biological activity of the full length PBAN. The fact that the pheromonotropic activity of the hexapeptide was similar to that of the full length PBAN, under specific conditions, suggests that this sequence constitutes the biologically active site of the neuropeptide. The discovery that PBAN-derived peptides reacted in a time- and dose-dependent mode, strengthens the assumption that proteolytic enzymes interfere with the pheromonotropic activity of the PBAN-derived fragments. The ability of a variety of peptides to stimulate sex pheromone biosynthesis suggests two possible mechanisms: (1) Existence of multiple pheromonotropic mechanisms which may be mediated by multiple PBAN receptors that are activated at different kinetics; (2) Existence of only one mechanism mediated by short C-terminally derived peptides. In the first case, the C-terminally derived sequences fulfill the conformational requirement of only one class of receptors, and other regions in the PBAN molecule (e.g., 9–13) fulfill the conformational requirements of a second (or other) class of receptors. In the second case, the C-terminally derived sequence is the only conformationally important sequence, and other sequences, which were found to be essential for the biological activity, serve other non-conformational purposes (e.g., protection against proteolytic degradation). © 1995 Wiley-Liss, Inc.     

Toxicity toChrysomela tremulae (Coleoptera: Chrysomelidae) of transgenic poplars expressing a cysteine proteinase inhibitor

The aim of this study was to test the potential of proteinase inhibitors to controlChrysomela tremulae, a beetle that causes severe damage in young plantations and in short-rotation intensive culture (SRIC) of poplar. As a first step, cysteine proteinases were determined to be the major digestive proteinases ofC. tremulae and oryzacystatin OCI, a cysteine proteinase inhibitor, was shown to inhibit this activityin vitro. The gene encoding OCI was introduced into poplar (Populus tremula ×P. tremuloides) and transgenic plants expressing OCI at a high level were selected. Feeding tests on these transgenic plants demonstrate the toxicity of OCI-producing poplar leaves againstC. tremulae larvae.J.C. Leplé and M. Bonadé-Bottino contributed equally to the research presented in this paper.