A possibility of using synthetic analogues of juvenile hormone (juvenoids) to disrupt imaginal diapause of the apple blossom weevil, Anthonomus pomorum females was demonstrated. Out of three preparations tested (methoprene, fenoxycarb and W-328) methoprene and fenoxycarb appeared to be effective. Sensitivity to juvenile hormone analogues develops early after imaginal emergence (even before the female starts to feed) and lasts throughout the whole aestivo-hibernation dormancy. Although the juvenoids could stimulate the onset of oogenesis at any time during diapause, the propensity of the ovaries to form normal eggs developed only during hibernation part of the dormancy; in earlier stages of diapause accumulation of yolk was observed but matured eggs were not produced. Methoprene treatment caused marked increase of locomotory activity accompanied with decrease of dry weight, increase of water content, depletion of trehalose resources, decrease of cold hardiness and, finally, 100% mortality within four weeks in the weevils treated during their feeding or aestivation stages. Although similar changes were observed in the treated pre-feeding weevils, they later recovered and survived until next spring without apparent loss of cold hardiness. A possibility of designing a control method based on this principle is discussed and the results of small-scale field trials that support its plausibility are reported.
Endo-polygalacturonases (PGs) are hydrolytic enzymes involved in the degradation of pectin, one of the major components of plant cell wall. While PGs from fungi, bacteria and plants have been extensively studied, PGs from insects are much less known, although they are likely to play an important role in insect-plant interactions. Presence of PGs has been reported for both piercing-sucking and chewing insect species, and possibly more commonly in mirid bugs (Heteroptera: Miridae). A screening of some common mirid species and other insects, belonging to different orders and families, was conducted using agarose diffusion assays run at different pHs. All the mirid species tested [Lygus rugulipennis Popp., L. pratensis (L.), Orthops kalmi (L.), Adelphocoris lineolatus (Goeze) and Closterotomus norwegicus (Gmelin)] showed PG activity, mainly at pH 7-8, whereas no activity was recorded for the other insect species, except Sitophilus sp. (Coleoptera: Curculionidae). PG activity in females of L. pratensis was significantly higher than in males, whereas there were no differences between the sexes in the other species. In all these species, PGs were present both in the salivary glands and the gut, with a higher activity in the salivary glands, confirming the role of these enzymes in the feeding behaviour of mirid bugs. Inhibition of mirid PGs by polygalacturonase-inhibiting proteins (PGIPs) from different plant sources was analysed at pH 7. PGIPs are extracellular plant proteins known for their ability to inhibit fungal PGs and restrict fungal colonization. Two PGIPs from Phaseolus vulgaris (PvPGIP3 and PvPGIP4) inhibited PGs of all the mirid bugs tested. This information may be helpful for the development of innovative insect-resistant plant varieties, for use in low-impact IPM.
A new genus, Afromuelleria gen. n., assigned to the tribe Trachyphloeini Lacordaire, 1863, is described for four South African species of weevils: A. awelani sp. n., A. baobab sp. n., A. limpopo sp. n. and A. venda sp. n. All species are illustrated and keyed. Taxonomic status of the new genus is discussed and compared with similar genera of Trachyphloeini and Embrithini Marshall, 1942.
A new genus, Coniophloeus gen. n., is described for five species of South African weevils known from the Western and Eastern Cape and assigned to the tribe Embrithini Marshall, 1942: Coniophloeus squalidus (Boheman, 1842) comb. n. (type species, transferred from the genus Trachyphloeus Germar, 1817 and tribe Trachyphloeini Lacordaire, 1863), C. alternans sp. n., C. oberprieleri sp. n., C. robustus sp. n. and C. obrieni sp. n. All five species are illustrated and keyed.
Fifteen years after the publication of the first genomic sequence of a phytophagous beetle, we review here the wealth of genetic and genomic information generated so far for the species-rich beetle superfamilies Chrysomeloidea (longhorn, seed and leaf beetles) and Curculionoidea (weevils and bark beetles). In this review we briefly describe the most common methods used to investigate the beetle genomes and also compile the nucleotide sequence information stored in public gene databases until December 2004. The motivations and relevance of these research initiatives are described in certain detail, distinguishing among structural and population studies, phylogenetic research, the study of genes involved in development and diapause, energetic metabolism, vegetal tissue digestion, and genes for insect resistance and defence.
Differences in the karyology of two species, Centricnemus leucogrammus and Peritelus familiaris (Coleoptera: Curculionidae), were investigated in order to elucidate their taxonomic position of the taxa. Previously both species were placed in one genus whereas the latest taxonomic revision puts them in separate genera. Cytogenetic analysis of P. familiaris and C. leucogrammus showed significant differences in karyotype structure and confirmed their present taxonomic status. The diploid set of C. leucogrammus consists of 22 chromosomes with a fundamental number of arms (FN) of 45 and little variation in morphology and length. Peritelus familiaris has 24 chromosomes with FN of 47 and a more diverse karyotype. The karyotype evolution might have occured by centric fissions of autosomes. At pachytene and diplotene in spermatocytes, each chromosome bivalent showed a small band of pericentric heterochromatin. The bands were hardly visible or undetectable in other stages of spermatogenesis, namely mitotic metaphase, diakinesis, metaphase I and II. The nucleolar organizer regions (NORs) were active at premeiotic stages and early meiosis, but invisible at meiotic metaphase I, metaphase II, and mitotic metaphase. These results indicate the usefulness of cytogenetic methods in taxonomic evaluations.
A cytogenetic study of bisexual species belonging to the genera Cirrorhynchus, Dodecastichus and Otiorhynchus is presented in order to confirm their taxonomic position. The karyotype characterization was accomplished by an analysis of mitotic and meiotic chromosomes after differential staining, namely by C-banding, silver impregnation, DAPI and CMA3. A review of the cytogenetic data for the tribe Otiorhynchini contributed to knowledge of chromosomal evolution in this group. An investigation of five of the species studied showed some similarities such as a sex chromosome system of "parachute type" (Xyp), the presence of 10 autosomal bivalents (2n = 22) and heterochromatin localized around centromeres. These observations are similar to those already described for Otiorhynchini species, and confirm the karyological conservatism of this weevil group. In contrast, another species Cirrorhynchus kelecsenyi has an additional four autosomal bivalents (n% = 14 + Xyp, 2n = 30), which differs considerably from the chromosomal homogeneity of the other genera. Karyotypic evolution in this species was achieved most probably by increasing the number of chromosomes by centric fissions, resulting in variation in the number of acrocentric chromosomes. DAPI-positive and CMA3-negative reactions of heterochromatic DNA in all the species studied suggest that it has an AT-rich composition. Impregnating chromosomes with silver nitrate reveals NORs on one pair of autosomes, and probably argentophilic material in the interspace between the X and y sex chromosomes. The karyological findings support the taxonomical revision of Otiorhynchini based on morphological characters.
The maize weevil, Sitophilus zeamais (Motschulsky), is a major pest of stored grain kernels. Irradiation is an established technique for controlling insects in stored grain and is a major stress factor affecting these insects. Since heat shock protein (hsp) genes respond to this stress, we proposed that hsps may be associated with irradiated stress tolerance in S. zeamais. The responses of the maize weevil to exposure to ultraviolet-C (UV-C) and microwave irradiation were assessed at four developmental stages: egg, larva, pupa and adult. The results revealed that exposure to UV-C (254 nm, < 8 h) did not affect the survival of the maize weevils; however, Szhsp70, Szhsc70 and Szhsp90 mRNA levels significantly increased during the first 1 h of UV-C exposure. The median lethal time (LT50) of exposure to microwave irradiation indicated that the adult stage was more tolerant of microwave irradiation than the other developmental stages. Microwave irradiation enhanced the expression of the three hsps, but the intensity of up-regulation differed among the three genes, with Szhsp70 the most highly up-regulated. Our experiments revealed that UV-C and microwave irradiation influenced the expression profile of hsp genes in S. zeamais. At the tissue level, the gene responses to UV-C and microwave irradiation varied greatly in different tissues., Jatuporn Tungjitwitayakul, Nujira Tatun, Boongeua Vajarasathira, Sho Sakurai., and Obsahuje bibliografii
Traps baited with plant volatiles and/or bark beetle pheromones have been used to survey for exotic and potentially invasive bark and wood-boring beetles in North America since the mid-1990s. Recent discoveries of sex and aggregation pheromones in the Cerambycidae offer means of improving detection rates of longhorn beetles, but little is known of their effects on detection of bark and ambrosia beetles in the subfamily Scolytinae. Our objectives were to determine the efficacy of host volatile trap lures for survey and detection of Scolytinae species and whether that efficacy was affected by the addition of longhorn beetle pheromones. More than 12,000 specimens and 36 species of Scolytinae were collected in two field trapping bioassays conducted in the Russian Far East in 2009 and 2010. The lure combination of spruce blend (a blend of racemic α-pinene, (-) β-pinene, (+)-3-carene, (+)-limonene, and α-terpinolene) and ethanol significantly increased detection rates and mean catches of Hylastes brunneus Erichson, Hylastes obscurus Chapuis, Ips typographus (L.), and Dryocoetes striatus Eggers compared with unbaited traps. The addition of the longhorn beetle pheromones, E-fuscumol, or E-fuscumol acetate, to traps baited with spruce blend and ethanol, slightly reduced mean catches of D. striatus but otherwise did not affect catch of any Scolytine species. Baiting traps with ethanol significantly increased mean catches of Anisandrus apicalis (Blandford), Anisandrus dispar (Fabr.), Anisandrus maiche (Kurenzov), Xyleborinus attenuatus (Blandford), Xyleborinus saxesenii (Ratzeburg), Xylosandrus germanus (Blandford), Scolytoplatypus tycon Blandford, and Trypodendron lineatum (Olivier). By themselves, the longhorn beetle pheromones, racemic hydroxyhexan-2-one and racemic hydroxyoctan-2-one, were not attractive to any Scolytine species. However, when added to ethanol-baited traps, hydroxyhexan-2-one lures significantly increased mean catch of S. tycon, hydroxyoctan-2-one lures significantly reduced mean catches of A. maiche and X. attenuatus, and lures of either hydroxyketone significantly reduced mean catch of T. lineatum. The lure treatments that detected the greatest number of species per sampling effort were spruce blend plus ethanol in 2009 (16 Scolytinae species and 13 species of Cerambycidae combined in an eight-trap sample) and hydroxyhexan-2-one plus ethanol in 2010 (20 Scolytinae species and 7 species of Cerambycidae combined in an eight-trap sample). Species accumulation curves did not reach an asymptote for any lure treatment, indicating that many species would go undetected in samples of 8-9 traps per site., Jon D. Sweeney, Peter Silk, Vasily Grebennikov, Michail Mandelshtam., and Obsahuje bibliografii