Search results for "Larva"

The ecdysone-induced DHR4 orphan nuclear receptor coordinates growth and maturation in Drosophila

2005

0092-8674 (Print) Journal Article Research Support, Non-U.S. Gov't; A critical determinant of insect body size is the time at which the larva stops feeding and initiates wandering in preparation for metamorphosis. No genes have been identified that regulate growth by contributing to this key developmental decision to terminate feeding. We show here that mutations in the DHR4 orphan nuclear receptor result in larvae that precociously leave the food to form premature prepupae, resulting in abbreviated larval development that translates directly into smaller and lighter animals. In addition, we show that DHR4 plays a central role in the genetic cascades triggered by the steroid hormone ecdyson…

Postembryonic development of Zophobas atratus Fab. (Coleoptera: Tenebrionidae) under crowded or isolated conditions and effects of juvenile hormone a…

1995

Abstract Pupation in Zophobas atratus is dependent on isolation and this provides a model for study of the onset of metamorphosis in beetles. We have analyzed the effects of isolation vs grouping on certain developmental parameters; the number of larval instars; their duration and weight. Sex differences were detected, such as the occurrence of regressive moults in females. Moreover, the development of Z. atratus is discussed in relation to Tenebrio molitor , the physiological timing of which appeared in part extendable to Z. atratus . Experiments show that 4–6 days of isolation are required for commencement of metamorphosis, as indicated by an immobile crooked posture observed at the end o…

Field application of the juvenile hormone analogue fenoxycarb against hopper bands of Locusta migratoria capito in Madagascar

1997

Summary Field trials have been carried out to examine the suitability of the JHA fenoxycarb in locust control. Laboratory tests have shown that a variety of JHAs, including fenoxycarb, applied to last instar larvae increased mortality, induced morphogenetic defects during metamorphosis, reduced fertility and provoked solitarisation of gregarious hoppers. The phase shift was indicated by green coloration and the acquisition of morphological and behavioural characteristics typical for solitary locusts. The present field experiments should clarify whether or not the effects observed in the laboratory are also observed with hopper bands in their natural habitat and if swarm formation and emigra…

The effect of L-thyroxine on the metamorphosis of Ascidia malaca

1981

Larvae of Ascidia malaca, both before and after hatching, were treated with L-thyroxine solutions. The effect of the thyroid hormone was to induce the onset of metamorphosis and then to cause the rate at which body reorganization occurred to increase. In treated larvae the resorption of the tail occurred only few hours after hatching, and a beating heart appeared form 10 to 15 h earlier than in the control larvae. These results are discussed in the context of a probable relationship between the occurrence of a hormonal metamorphic factor and the button cells of the trunk.

Presence of thyroid hormones in ascidian larvae and their involvement in metamorphosis

2001

In this study we investigated the presence and localization of thyroxine in Ciona intestinalis larvae and its involvement in metamorphosis. To date, the mechanisms regulating the metamorphosis of ascidians remain largely unknown. In vivo treatment of swimming larvae with exogenous L-thyroxine and thiourea, and in vitro experiments utilizing high performance liquid chromatography, radioimmunoassay, and immunoperoxidase staining demonstrate the presence of thyroxine at the larval stage. This suggests that this hormone may participate in the control of metamorphosis and thus play a different role from that observed in adults.

Acute hepatotoxicity induced by quetiapine fumarate in larval zebrafish

2016

Responses to ultraviolet radiation in larval pike, Esox lucius, of two origins and ages

2007

Ultraviolet radiation (UVR)-induced mortality and behavioural disorder were studied in larval northern pike of two origins and ages. Newly hatched larvae of two differently coloured populations and six-day-old larvae of one population were exposed to four fluence rates of UVR, resulting in total doses from 11.5 to 63 kJ m–2, and monitored for mortality and behaviour. The rate of mortality and the severity of behavioural disorder differed by origin and age of the animals, but the effect was fluence-rate dependent. Total melanin concentration of newly hatched larvae was measured to assess if sensitivity to UVR correlated with pigmentation, but no differences in melanin concentration between l…

Variation in the Sizes of Chthamalid Barnacle Post-Settlement Cyprids on European Shores

2001

As part of a wider study on the settlement and recruitment of Chthamalus spp. in Europe, this study investigated whether chthamalid cyprids can be separated by length on a European scale. Variation in cyprid length with latitude and temporal variation at selected localities were also examined. The lengths of cyprids collected between 1996-1999 on nine rocky shores in Europe are reported. Elminius modestus cyprids were found only at Roscoff, NW France and could be distinguished due to their Carapace shape and length. They showed a unimodal length distribution, measuring between 450 and 625 mum, with no variation in length between the two sampling dates (1997 and 1998). Based on carapace shap…

STUDY OF LARGE PELAGIC FISH LIFE-HISTORY TRAITS IN THE CENTRAL MEDITERRANEAN SEA AND PROJECTION UNDER FUTURE CLIMATE CHANGE SCENARIOS

2022

One of the most sensitive life periods for each species is the first life stages (larval and juvenile). The survival rates of pelagic fish larvae in these phases are usually very low and subject to fluctuations, consequently affecting the recruitment of new generations. From historical Tuna landing data, the stock's abundance is fluctuating, especially for Atlantic Bluefin Tuna (ABT) (Thunnus thynnus, Linnaeus, 1758) Eastern stock. It is the largest Mediterranean Tuna and one of the most expensive species in the world. Some studies hypothesized that the fluctuations are dictated by environmental factors, particularly in the early life stages. Therefore, it appears necessary to better unders…

Female Oviposition Decisions and Their Impact on Progeny Life-History Traits

2008

An important factor affecting the life-history of an organism is parental investment in reproduction: reproductive decisions are almost invariably costly. Therefore, reproductive decisions should be beneficial in terms of increased offspring number or fitness. For example, egg laying decisions in many insects can influence resource availability of the offspring through changes in the larval density, and resource availability will have effects on many life-history traits. Here we studied whether female reproductive decisions affect offspring fitness in Callosobruchus maculatus seed beetles. Females laid more eggs on black-eye beans than on mung beans. However, when the difference in the surf…