Percent Egg Viability Research Articles

Influence of parental age on reproductive performance of an aphidophagous ladybird, Propylea dissecta (Mulsant)

Abstract: In the present study the influence of maternal and paternal ages on reproductive performance of an aphidophagous ladybird, Propylea dissecta (Mulsant) were investigated. Maternal age strongly influenced fecundity and pre‐oviposition period while paternal age strongly influenced the egg viability. Maternal age also influenced percent egg viability, however, at lower levels of significance. The results revealed that the fecundity and percent egg viability increased up to the respective maternal and paternal ages of 30 days and thereafter declined, indicating the onset of senescence. The results of the present study can help in better mass multiplication of the ladybird concerned and in laying foundation for further age‐related studies.

Reproductive performance in induced and spontaneous spawning of the mangrove red snapper, Lutjanus argentimaculatus : a potential candidate species for sustainable aquaculture

A reliable breeding technique was developed for the mangrove red snapper, Lutjanus argentimaculatus (Forsskal 1775), to help sustain the aquaculture of this immensely popular species in Southeast Asia. Using standardized indices of female maturity (based on mean oocyte diameter of ≥0.40 mm), time of injection (1000–1130) and sex ratio (one female to two males), a single injection of 100 μg kg−1 luteinizing hormone-releasing hormone analogue (LHRHa) (n=16 fish), but not 50 μg kg−1 (n=five fish), successfully induced egg (62.5% success rate) and larval (43.8%) production. Human chorionic gonadotropin (hCG) at 500 IU kg−1 (n=five fish) also failed to induce spawning, but doses of 1000 (n=22 fish) and 1500 IU kg−1 (n=15 fish) gave spawning (77.3% and 80.0% respectively) and hatching success rates (72.7% and 60.0% respectively) that were not significantly different from those of 100 μg kg−1 LHRHa. No spawning was observed in saline-injected controls (n=seven fish). While mean spawning latency, egg diameter, egg production per spawn, percent egg viability, hatching rate, percent of normal larvae and cumulative survival of eggs to normal larvae did not differ significantly among the effective hormones and doses, 1000 IU kg−1 hCG had a higher percentage (76.5%) of total spawns with egg production per spawn in excess of one million than those of 1500 IU kg−1 hCG (50.0%) and 100 μg kg−1 LHRHa (40.0%). Mangrove red snapper spontaneously spawned from March–April to November–December with a peak of egg collection and spawning in May–June. Egg collection per spawn ranged from 0.05 to 6.35 million. Spontaneous spawning of mangrove red snapper exhibited lunar periodicity with spawns mostly occurring 3 days before or after the last quarter and new moon phases and occurred consistently between 02:00 and 04:00 hours. High fecundity and good egg quality, coupled with the ability to respond to induce spawning or natural spawning in captivity, provide a sound basis for improving the sustainability of red snapper aquaculture in Southeast Asia.

Influence of Temperature on Age-Specific Fecundity of the Ladybeetle Micraspis discolor (Fabricius)

The influence of temperature on the age-specific fecundity of an aphidophagous ladybeetle, Micraspis discolor (Fabricius) (Coleoptera: Coccinellidae) feeding on the cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) at four different temperatures, viz. 20, 25, 27 and 30°C, was investigated. The age-specific fecundity function was triangular and oviposition rate (no. of eggs/day) increased with increase in reproductive age of the ladybeetle, attaining a peak then gradually decreasing before finally ceasing. Young adults were more efficient at converting aphid biomass into eggs than older ones. The oviposition peak tended to shift towards younger females and the oviposition rate increased with increase in temperature from 20 to 27°C. The maximum fecundity and percent egg viability was 750 eggs and 95% at 27°C and minimum 385 eggs and 65% at 20°C, respectively.

Selection, Egg Viability, and Fecundity of the Sugarcane Borer (Lepidoptera: Crambidae) with Tebufenozide

Two separate attempts to select the sugarcane borer, Diatraea saccharalis (F.), for resistance to tebufenozide were unsuccessful. Both selected colonies were lost after the fourth generation due to a lack of oviposition. Differences were not detected in fecundity or percent egg viability for 5-d-old third instars exposed to concentrations (EC5, EC15, and EC30) of tebufenozide for 7 d. Decreases (P < or = 0.01) in mean female pupal weights were detected in larvae exposed to EC15 and EC30 concentrations. An ovicidal impact using serial dilutions of tebufenozide (10, 100, and 200 ppm) also was detected. Percent viability was reduced from 98% for untreated eggs to 61% for eggs dipped in 10 ppm and below 6% for eggs dipped in > or = 100 ppm. Eggs treated with 200 ppm did not hatch. Though some embryonic development was observed on eggs treated with the high concentrations (100 and 200 ppm), sclerotization of head capsule was not apparent. The ovicidal property of tebufenozide may enhance its effectiveness in controlling populations of the D. saccharalis on an area-wide basis. Fecundity and egg viability were affected in later generations of selection; however, separate studies assessing individuals that were exposed to sublethal concentration (EC5, EC15, and EC30) of tebufenozide as third instars for 7 d in one generation did not detect differences.

Laboratory Mating of Aedes vexans (Diptera: Culicidae)1

While most efforts to produce cage conditions that encourage stenogamy within a population of Aedes vexans (Meigen) have met with little success (Horsfall et al. 1973), mating of caged A. vexans has been previously reported by Dashkina and Tsarichkova (1965). However, neither the percent insemination nor the percent egg viability was given in their brief account. Female adults were observed to copulate with swarming males under reduced light conditions, when the adults were kept in a cage 100 × 100 × 200 cm high.