The larvae of most benthic marine invertebrate species must develop for a minimum of time in the plankton before they become competent for settlement and metamorphosis in response to stimulating external cues. In an experimental laboratory study, we identified the temporal window of cue receptivity within the moulting cycle of the megalopa stage of an estuarine crab, Chasmagnathus granulata Dan...

Fourth-stage larvae (L4) of the cattle filarial parasite Onchocerca lienalis were produced from third stage forms (L3) and maintained in vitro using a variety of culture media and feeder cell layers. Up to 50% of the L3 larvae moulted to the fourth stage in the presence of two jird (Meriones unguiculatus) cell lines, a monkey kidney cell line and also with Vero cells. Moulting took place 2-5 da...

The effect of moult on eggshell mechanical properties, on composition and concentrations of organic matrix components and on eggshell microstructure was investigated. The observed changes were studied to understand the role of organic matrix and eggshell microstructure in eggshell strength. Moult was induced by zinc oxide (20 g zinc/kg diet) in 53 ISA Brown laying hens at 78 weeks of age. No di...

BACKGROUND Nuclear receptors are essential players in the development of all metazoans. The nematode Caenorhabditis elegans possesses more than 200 putative nuclear receptor genes, several times more than the number known in any other organism. Very few of these transcription factors are conserved with components of the steroid response pathways in vertebrates and arthropods. Ftz-F1, one of the...

The effects of a sublethal dose of Dieldrin (7.2 x 10(-5) g/day) were evaluated on oxygen consumption, survivorship, moulting and reproduction of Rhodnius prolixus. No difference was found in oxygen consumption between treated and control male insect. Survivorship proved to be very much affected by the sublethal exposure, but this was strongly dependent on the feeding stage of the individuals. ...

The developmental events occurring during moulting and metamorphosis of insects are controlled by precisely timed changes in levels of ecdysteroids, the moulting hormones. The final four sequential hydroxylations of steroid precursors into the active ecdysteroid of insects, 20E (20-hydroxyecdysone), are mediated by four cytochrome P450 (P450) enzymes, encoded by genes in the Halloween family. O...

All nematodes possess an external structure known as the cuticle, which is crucial for their development and survival. This structure is composed primarily of collagen, which is secreted from the underlying hypodermal cells. Extensive studies using the free-living nematode Caenorhabditis elegans demonstrate that formation of the cuticle requires the activity of an extensive range of enzymes. En...

It was observed that Leidynema appendiculata (Leidy, 1850) and Hammerschmidtiella diesingi (Hammerschmidt, 1838; Chitwood, 1932), which are nematodes parasitic in the hind-gut of Blatta orientalis L., could survive in the hind-gut when the cockroach moulted and it was decided to see what effect moulting of the cockroach had upon the nematodes. In moulting cockroaches there is a certain amount o...

Flavonoids are the most abundant plant polyphenols, widely occurring in fruits and berries, and show a strong antioxidant activity in vitro Studies of avian species feeding on berries suggest that dietary flavonoids have health-promoting effects and may enhance the expression of melanin-based plumage traits. These effects are probably mediated by the antioxidant activity of flavonoids. However,...

During downstream transport from rivers to estuaries, early larval stages of the Amazon River prawn Macrobrachium amazonicum (Heller 1862) are likely exposed to planktonic food limitation. In the laboratory, we studied the effects of presence or absence of food on larval survival, moulting and biomass (dry mass, and content of carbon, hydrogen and nitrogen). Unfed larvae developed successfully ...