Expression Of Autogeny Research Articles

Is the expression of autogeny by Culex molestus Forskal (Diptera: Culicidae) influenced by larval nutrition or by adult mating, sugar feeding, or blood feeding?

Culex molestus Forskal is suspected to have been introduced into southern Australia during the 1940s. Investigations to determine factors influencing the expression of autogeny, the response of this mosquito to potential blood meals, and the subsequent influence on oviposition were undertaken. Immature mosquitoes raised at five feeding regimes had mortality rates, development rates, wing length, and autogenous egg raft size measured. All surviving female mosquitoes laid autogenous eggs but there was a significant difference between the mean number of eggs per raft. For mosquitoes raised at each of the feeding regimes, there was a significant linear relationship between the number of eggs per autogenous egg raft and wing length. Newly emerged mosquitoes were offered a blood meal (i.e., rodent) daily but no blood feeding occurred until the autogenous egg raft was laid. There was no statistical difference in the rate of autogenous oviposition or post-oviposition blood feeding between control or treatment groups. The results of this study indicate that Cx. molestus is perfectly adapted to subterranean habitats in close association with human habitation, but their preference to delay blood feeding until up to day 8 following emergence may reduce their relative importance as a vector of arboviruses.

Development time and survival of Verrallina funerea (Theobald) (Diptera: Culicidae) immatures and other brackish water mosquito species in southeast Queensland, Australia

Verrallina funerea (Theobald) is a brackish water mosquito that is recognised as an important pest and vector in southeast Queensland, Australia. Immature development time and survival of Ve. funerea was defined in the laboratory in response to a range of temperatures (17-34 degrees C) and salinities (0-35 parts per thousand (p.p.t)). The expression of autogeny in this species was also assessed. Salinity only had a slight effect on mean development time from hatching to adult emergence (7.0-7.4 d at salinities of 0, 17.5 and 31.5 p.p.t) and survival was uniformly high (97.5-99.0%). Mean development times were shorter at 26, 29 and 32 degrees C (7.0, 6.8 and 6.8 d, respectively) and longest at 17 degrees C (12.2 d). The threshold temperature (t) was 5.8 degrees C and the thermal constant (K) was 142.9 degree-days above t. Survival to adulthood decreased from > 95% (at 17-29 degrees C) to 78% (at 32 degrees C) and 0% (at 34 degrees C). No expression of autogeny was observed. Immature development times of Ve. funerea, Ochlerotatus vigilax (Skuse) and Oc. procax (Skuse) were then determined under field conditions at Maroochy Shire. Following tide and rain inundation, cohorts of newly hatched larvae were monitored daily by dipping, and time until pupation was noted. Tidal inundation triggered hatching of Ve. funerea and Oc. vigilax larvae whereas Oc. procax larvae were found only after rain inundation. Estimates of Ve. funerea and Oc. vigilax field development times were similar (8-9 d) while Oc. procax development time was slightly longer (9-10 d). Based on these survey results, control activities targeting Ve. funerea must be initiated 4 d (if using Bacillus thuringiensis var. israelensis de Barjac) or 5 d (if using s-methoprene) after inundation. However, Casuarina glauca Sieber canopy and branchlets covering breeding habitats may present a problem for the penetration of such treatments.

Geographic Variation in the Expression of Autogeny in Aedes togoi (Diptera: Culicidae) Under Different Temperature and Photoperiod Conditions

Larval developmental time, adult size, and the expression of autogeny were studied in eight populations of Aedes togoi (Theobald) originating from 4.8 degrees N to 49.2 degrees N under four experimental conditions of temperature and photoperiod (20 degrees C and 10:14 [L:D] h; 20, 25, 30 degrees C and 16:8 [L:D] h). Larval developmental time and adult scutum length decreased as a function of increasing rearing temperature. In northern populations at 20 degrees C, larval developmental time was shorter in short-day than in long-day conditions. Females of tropical and subarctic populations remained autogenous under different conditions and produced many autogenous eggs in the first batch. In subtropical and temperate populations, the percentage of autogenous females varied from 0 to 100%, being highest at low temperature and short-day condition. A correlation analysis of population traits indicated that the autogeny rate was correlated positively with larval developmental time and the number of eggs per autogenous female. The life-history traits did not show a simple clinal gradient over mean annual temperature of the locality of origin, except that adult scutum length decreased with an increase in mean temperature. A principal components analysis for female life-history traits revealed a continuous latitudinal change from temperate to tropical populations; populations at low latitudes were small in adult size and more autogenous. Subarctic populations showed a departure from this trend, having large adult size but high autogeny rate.

Effects of Mating and Sugar Feeding on the Expression of Autogeny in Crabhole Mosquitoes of the Genus Deinocerites (Diptera: Culicidae)1

Autogeny was much more prevalent in a temperate than in a tropical population of Deinocerites pseudes . Most sugarfed De. pseudes females did not initiate autogenous egg development until after mating. High proportions (>90%) of autogeny were found in tropical, subtropical, and temperate-zone populations of Deinocerites cancer . Either sugar feeding or mating triggered egg development in De. cancer, but sugar-fed females produced more eggs. Whether sugar-fed or not, unmated De. cancer females developed eggs after blood feeding. Thus 3 factors, blood feeding, sugar feeding, or mating, can independently stimulate the production of the initial egg clutch in De. cancer .

Oogenesis in a North American population of Aedes (Finlaya) togoi (Theobald) (Diptera: Culicidae)

The expression of autogeny in Aedes togoi and its timing are highly variable. Autogenous females, fed 10% sucrose and maintained at 24 °C with a photoperiod of 17.5 h light: 6.5 h dark, developed mature eggs between 5 and 30 days after eclosion. The percent autogeny in a population from Vancouver, B.C., collected as larvae from the field (P1 generation) was 42% ([Formula: see text] eggs/female); the percent autogeny in the laboratory F2 generation, unselected for autogeny, was 40% ([Formula: see text] eggs/female). In the laboratory colony, the process of maturing follicles to the egg stage was frequently delayed. Some females (8%) had mature oocytes on day 5, while 20, 27, and 44% of the female population had mature oocytes on days 6, 8, and 15, respectively. The presence of mature oocytes does not inhibit blood feeding: 17–26% of the females containing mature oocytes took blood, and embarked on a new round of oogenesis. The ovaries of these females contained two separate cohorts of primary follicles, viz., mature oocytes developed autogenously and oocytes developing as a result of the blood meal. Most of the autogenous females with mature oocytes (57–83%) refused blood. This indicates that the presence of mature follicles is a deterrent to feeding and probably to host-seeking. Mating had no effect on the proportion of females that was autogenous.

Expression of autogeny in relation to larval population density of Sarcophaga bullata Parker (Diptera: Sarcophagidae)

The expression of autogeny in S. bullata was influenced by the larval rearing conditions. Low larval population densities resulted in large flies that were autogenous. On the other hand, high larval population densities produced small flies that were anautogenous, In anautogenous females the size and stage to which the follicles developed varied with the size of the fly. When reared on a sucrose–water diet, the females from an intermediate larval population density possessed larvae, mature eggs, degenerate follicles, or undeveloped follicles.

Autogeny and polymorphism for wing length in Leptoconops becquaerti (Kieff.) (Diptera: Ceratopogonidae).

Data given show that in Jamaica, Leptoconops Becquaerti is polymorphic for wing length in both sexes. The polymorphism is associated with autogeny so that in a given population the smaller ♀♀ are autogenous, the larger anautogenous. The autogenous ♀♀ emerge from the pupa with ovaries already in early Stage IV of development; at 26.6°C egg maturation is completed within 24–36 hr post-emergence. The number of eggs produced autogenously in the 1st gonotrophic cycle is comparable with that seen in anautogenous ♀♀ fully engorged with blood and kept under optimum conditions. Larval environment does not appear to affect the expression of autogeny by regulating the proportion of ♀♀ that produce eggs without taking blood. Instead, it appears that wing length polymorphism and autogeny are entirely under genetic control. Some observations on mating and resting behavior in the field are described. Reasons are given for believing that human discomfort is caused almost entirely by anautogenous ♀ L. becquaerti .

STUDIES ON THE DIETARY AND ENDOCRINE REGULATION OF AUTOGENOUS REPRODUCTION IN AEDES TAENIORHYNCHUS (WIED.).

The expression of autogeny, in a highly autogenous strain of AEDES TAENIORHYNCHUS, may be reduced by altering the quality and quantity of the larval diet and by withholding sugar from newly emerged females. Allatectomy of these autogenous A. taeniorhynchus within one hour of emergence prevented all autogenous yolk deposition, but the implantation, 24 hours later, of 1 pair of corpora allata stimulated egg maturation. Extirpation of the medial neurosecretory cells from the brain of newly emerged ♂ ♂ also prevented autogenous egg maturation.