H. M. Chu

Pupation requirement of the beetle, Xyleborus ferrugineus: sterols other than cholesterol.

Abstract Aposymbiotic Xyleborus ferrugineus utilized cholesterol or lanosterol as a sole source of sterol for production of eggs and hatching of larvae, but failed to pupate during consecutive broods or generations in diets with such sources of sterol. The insects produced several broods or generations of progeny that pupated and formed normal adults when ergosterol or 7-dehydrocholesterol was the sole source of sterol. Lumisterol, or vitamin D 2 or D 3 , was antagonistic to progeny production or survival.

Morphology and ultrastructure of the antenna of male Periplaneta americana as related to chemoreception

SummaryOn the antenna of adult male Periplaneta americana, three size ranges of classical sensilla basiconica were found. Based on SEM, a sensillum of the s. trichodeum shape was revealed, but our TEM efforts indicate that this sensillum has the thin-wall, porous ultrastructure of a sensillum basiconicum. Sensilla basiconica contain flask-shaped cuticular pores. All viewed pores join four or five tubules. The pore tubules clearly contact plasma membranes of dendritic branches. Two sizes of grooved pegs were observed. The terminal segment of the antenna contains a variety of other “receptors”.

Chemosensory mechanism in Periplaneta americana: Electroantennogram comparisons of certain quinone feeding inhibitors

Abstract Several feeding-inhibitory 1,4-naphthoquinones reduced amyl acetate-stimulated electroantennograms (EAGs) from adult male Periplaneta americana in the same order as they inhibit feeding in bioassays. EAG data on the quinone effects upon antennal nerves indicate both relatively reversible and irreversible actions. Classical sulphydryl reagents closely mimicked the quinones in their effects on EAGs.

Ultrastructure of the compound eye of the diploid female beetle, Xyleborus ferrugineus

SummaryThe compound eye of female (diploid) Xyleborus ferrugineus beetles was examined with scanning and transmission electron microscopy. The eye is emarginate, and externally consists of roughly 70–100 facets. Each ommatidium is composed of a thickly biconvex lenslet with about 50 electron dense and rare layers. The lens facet overlies a crystalline cone of the acone type which is roughly hourglass-shaped. Pigment cells envelop the entire ommatidium, and pigment granules also are abundant throughout the cytoplasm of the 8 retinular cells. The rhabdomeres of 2 centrally situated photoreceptor cells effectively fuse into a rhabdom that extends from the base of the crystalline cone deeply into the ommatidium. Six distal peripheral retinular cells encircle the 2 central cells, and their rhabdomeres join laterally to form a rhabdomeric ring around the central rhabdom. The rhabdom and rhabdomeric ring are effectively separated by the cytoplasm of the two central retinular cells which contains the usual organelles and an abundance of shielding pigment granules. Eight axons per ommatidium gather in a tracheae-less fascicle before exiting the eye through the fenestrate basement membrane. No tracheation was observed among the retinular cells. Each Semper cell of each observed crystalline cone contained an abundance of virus-like particles near the cell nucleus. The insect is laboratory reared, and the visual system seems very amenable to photoreceptor investigations.

Sorbic acid-induced differences in the ultrastructural development of oocytes in the microbially ectosymbiotic female of Xyleborus ferrugineus (fabr.) (coleoptera, scolytidae)

The ovaries of the beetle Xyleborus ferrugineus reared on standard sawdust diet with an without 0.08% sorbic acid added were examined for differences in ultrastructural development of the oocytes. Indications of vigorous yolk deposition are an extensive rough‐surfaced endoplasmic reticulum (RER), numerous electron‐dense secretory vesicles and a prominent nucleus in associated follice cells, and extremely electron‐opaque material in the interfollicular cell spaces and the perioocytic area. After 6 days of feeding without added sorbic acid, a mature terminal oocyte is present in one of the two ovaries. This terminal oocyte at this mature stage contains yolk spheres and lipid bodies. However, the most mature oocyte in beetles reared on the standard sawdust diet to which 0.08% sorbic acid was added remained at a previtellogenic stage after 6 days of feeding. Titers of ecdysone in 6‐day‐old adult females reared on standard sawdust without and with 0.08% sorbic acid added were 534.64 ± 20.93 S.D. pg/mg and 39.94 ± 14.71 S.D. pg/mg body weight, respectively.

Ecdysteroids in adults, ovaries and eggs of Xyleborus ferrugineus (Coleoptera:Scolytidae)

Abstract Free ecdysteroids in the extract of various aged males, females and embryos, and of ovaries of different aged females were estimated by radioimmunoassay. Such ecdysteroids were present during all stages of ovarian development and their titre peaked (534 pg/mg body wt) at day 6 in the cycle, the time of major yolk deposition and initial ovulation. Ovaries did not contain the whole body complement of free ecdysteroids; however, they showed a cyclical pattern of titre that coincided with cycles of oocyte maturation and ovulation. The observed cyclical decline in these free steroids in ovaries was approximately two egg equivalents. Such ecdysteroids were present during all phases of embryonic development and peaked at 362 pg/mg egg wt in embryos that had undergone gastrulation and germ band extension. Free ecdysteroid content in males showed no significant peak at any stage of development.

Maternal Xyleborus ferrugineus transmission of sterol or sterol-dependent metabolites necessary for progeny pupation☆

Aposymbiotic female Xyleborus ferrugineus transmitted, apparently transovarially, the sterol or sterol-dependent metabolites necessary for progeny pupation. Sterol for immature development was required in the progeny diet. When maintained on cholesterol-containing diet, maternal females lost their ability to pass required pupation factors to progeny.

Ultrastructure of the compound eye of the haploid male beetle, Xyleborus ferrugineus.

SummaryThe compound eye of male (haploid) Xyleborus ferrugineus beetles was examined with scanning and transmission electron microscopy. The eye externally consists of ca. 19 to 33 facets. Each ommatidium is composed of a thickly biconvex lenslet with about 50 electron dense and rare layers, but at the junction area between two lenslets there are only about 35 to 37 layers that can be distinguished. A very short (3.4–4.0 μm) acone type crystalline cone is located directly beneath the lenslet. Each ommatidium is surrounded by pigment cells, and pigment granules also appear throughout the cytoplasm of the retinular cells. Some pigment granules are even present below the basement membrane. There are 8 retinular cells. The rhabdomeres of 2 centrally situated photoreceptor cells fuse into a rhabdom which is enveloped by the rhabdomeres of 6 peripheral retinular cells. The rhabdomeres of the 6 peripheral retinular cells join laterally to form a rhabdomeric ring around the central rhabdom. No tracheation was observed among the retinular cells. Virus-like particles are evident near the nucleus in each Semper cell of the crystalline cone.

Role of Steroids in Aging

One of the better criteria for senescence in an animal is unequivocal decline in one or more physiological functions significantly before the death of the individual (Lockshin and Zimmermann 1983). Some long-lived insect imagoes are known to show overall changes in given physiological and biochemical activities and histological appearances which can appropriately be described as senescence (Rockstein and Miquel 1973). A particularly appealing criterion for senescence in an insect would be an equivalent of menopause (Lockshin and Zimmerman 1983).

ECDYSTEROIDS DURING PUPAL DEVELOPMENT OF FEMALE XYLEBORUS FERRUGINEUS

Ecdysteroid titers were estimated on the whole body homogenates of Xyleborus ferrugineus (Fabr.) female pupae during development by radioimmunoassay. A distinct peak of ecdysteroids was observed at 36‐hr pupal development (743 pg/mg body wt). Titer declined to 299 pg/mg by the pharate adult stage and to 193 pg/mg body wt just before adult emergence. Qualitative studies by HPLC revealed a ratio of 3:1 ecdysone to 20‐hydroxyecdysone in the initial pupal stage. Pharate adults had mainly 20‐hydroxyecdysone. The observed single peak in ecdysteroid titer agrees with findings in other studied coleopteran species.