Identification and Expression of Inward-Rectifying Potassium Channel Subunits in Plutella xylostella

In insects, inward-rectifying potassium (Kir) channels regulate vital physiological functions, such as feeding behavior, silk secretion, renal excretion, and immune function. Therefore, they offer promising potential as targets for insecticides. Three types of Kir subunits have been identified in Diptera and Hemiptera, but the Kir subunits of Lepidoptera still remain unclear. This study identified five Kir subunit genes (pxkir1, pxkir2, pxkir3A, pxkir3B, and pxkir4) in the transcriptome of Plutella xylostella. Phylogenetic analysis identified pxkir1, pxkir2, pxkir3A, and pxkir3B as orthologous genes of kir1–3 in other insects. Interestingly, pxkir4 may be encoding a new class of Kir subunit in Lepidoptera that has not been reported to date. To identify further Kir channel subunits of P. xylostella, the gene expression profiles of five pxkir genes were studied by quantitative real-time PCR. These pxkir genes are expressed throughout the development of P. xylostella. pxkir1 and pxkir2 were highly expressed in thoraxes and legs, while pxkir3 (3A and 3B) and pxkir4 had high expression levels in the midgut and Malpighian tubules. This study identified the composition and distribution of Kir subunits in P. xylostella for the first time, and provides useful information for the further study of Kir channel subunits in Lepidoptera.

Curious Caddis Couture: Form and function among cases of Australian Hydroptilidae

Trichoptera larvae that construct portable cases occur worldwide, in some groups building highly distinctive cases. Fifth instar larvae of several genera in the micro-caddisfly family Hydroptilidae always build cases of the same form, thus affording ready identification of their larvae and pupae to genus level. Examples are Oxyethira and Orthotrichia: the former have transparent flask-shaped silk (secretion) cases, the latter ‘wheat seed’-shaped silk cases that are generally dark brown to black in colour. Additionally, in the fauna of mainland Australia, cases of the endemic genus Orphninotrichia are unmistakable in form; enigmatically, however, quite different forms are seen in two of the four locally endemic species on the small, off-shore, oceanic island of Lord Howe. The larval cases of some other Australian genera also vary considerably, some in materials (e.g., Hydroptila) and others in both materials and shape (e.g., Hellyethira and an Australian endemic genus, Maydenoptila). Known larvae of microcaddisfly species in the Australian fauna are examined in search of patterns in the three most obviously variable attributes of cases: mode of construction, shape, and materials. Possible relationships between form and function are postulated for some of the cases.

SILKS AND SILK-PRODUCING ORGANS OF NEOTROPICAL TARANTULA AVICULARIA METALLICA (ARANEAE, MYGALOMORPHAE, THERAPHOSIDAE)

Silks and silk-producing organs of the theraphosid species Avicularia metallica were studied using scanning electron microscopy. The spinning apparatus is made up of two pairs of spinnerets located at the end of the ventral side of the opisthosoma. Both pairs of spinnerets are equipped with spigots (modified setae), i.e. external outlets of silk-producing glands which, in the case of posterior lateral spinnerets, are present on all three segments.The secreted silk, which hardens when exposed to air, is processed by movements of spinnerets and the opisthosoma. An investigation of spinning activity revealed two different manners in which silk is affixed to the ground: (1) by smearing silk secretion directly onto the surface of the substratum; or (2) by attaching silken fibers onto a layer of adhesive silk of attachment fields. The fibers connecting the walls of tubular shelters to the silk of attachment fields are essentially bundles of parallel nanofibrils. The connection between multifibrillar connecting fibers and the adhesive silk of attachment fields is, in essence, “silk-to-silk” connection. Nanoglobules (spherical subunits) are the basic microstructural blocks in the studied silk materials irrespective of whether the fibrils are a part of the tube, connecting fibers, or attachment fields. SEM images showed that the liquid silk, running through spigot ducts, has two components, which do not mix as they leave the spigots. The peripheral component of the solidified protein mixture surrounds the central component, which has a granular appearance

Croissance, bilan d'energie et production d'eau metabolique chez la larve de Tineola bisselliella

The keratophagous larva Tineola bisselliella develops better in a dry than in a wet environment at the constant temperature of 20 °C. At 95% relative humidity (RH), mortality is higher than 80% and the larval life lasts up to 341 days. At 5% RH, mortality reaches only 30% and the larval life lasts only 216 days. The study of utilization of the energy contained in 3680 μg of food (mukrat hair) at 95% RH and then at 5% RH shows the physiological reactions of the larva when the RH is modified. At 5% RH, the larva ingest the 3680 μg of food in 17 days while they ingest the same amount in 10 days at 5% RH. For the same quantity of ingested energy, the energetic value lost by respiration and silk secretion are more important at 95% RH than at 5% RH. In a very wet environment, the energy lost in the feces is reduced. At 5% RH, the production of body tissue and the storage of the ingested energy are twice as high as those at 95% RG, in spite of a loss of water which may exceed 4 μg/h. The production of metabolic water allows the larva to keep constant its quantity of body water and does not prevent the storage of lipidic substances. The weight of metabolic water produced at 5% RH is evaluated at 33% of the weight of the ingested food.