Tradeoff between triglyceride consumption and ovariole development in Plutella xylostella(L.) released in mixed-host environments

After exposure to mixed environments with multiple hosts, the frequency of flight take-offs for Plutella xylostella(L.) is known to increase with a concomitant decrease in female fecundity. The objective of the present study was to elucidate the physiological mechanism underlying the increased flight activity and decreased fecundity of P. xylostella in mixed-host environments. We measured ovariole length, and triglyceride and vitellogenin(Vg) content in P. xylostella females after they were released into different host environments consisting of either a single host(Brassica campestris, Brassica oleracea or Brassica juncea) or a mixture of all three hosts. Our results indicated that ovariole length varied significantly between female adults from different host environments. Females from the B. campestris environment had the longest ovarioles, whereas those from the mixed environment had the shortest ones. A negative correlation was found between ovariole length and the flight take-off frequency of P. xylostella adults. Additionally, there were significant differences in the triglyceride content of P. xylostella females from different host environments. Our data revealed that more triglyceride was consumed by P. xylostella female adults from B. oleracea and the mixed environments than those from environments containing only B. campestris or B. juncea. In contrast, the relative Vg content in P. xylostella females from the mixed environment was lower than that in females from the B. campestris-, B. juncea-or B. oleracea-only environments. In conclusion, the mixed environment caused increased consumption of available energy resources(triglyceride) at the cost of retarding ovarian development and decreasing the amount of Vg produced.

Variations in body melanisation, ovariole number and fecundity in highland and lowland populations of Drosophila melanogaster from the Indian subcontinent

We investigated geographical variations in three fitness-related traits （body melanisation, ovariole number and fecundity） in laboratory-reared offspring of 10 populations of Drosophila melanogaster. The populations were collected from adjacent lowland and highland localities （-80-100 km apart） in the tropical as well as subtropical regions （11.15-31.06°N） covering a linear distance about 3 000 kilometers from south to north on the Indian subcontinent. Persistence of within- as well as between-population differences at 21 ℃ suggest that observed variations in fitness-related traits have a genetic basis. Populations from higher altitudes showed consistently higher trait values （1.4-fold increase） as compared with their corresponding lowland populations. By contrast, latitudinal variations were about two-fold higher across the entire continent. Along latitude as well as altitude, population means showed higher correlation values （r 〉 0.98） between all the three fitness traits. However, on the basis of within-population analysis （assorted darker and lighter flies）, changes in body melanisation were significantly correlated with fecundity but not with ovariole number. Thus, analysis of within-population trait variability should be preferred as compared with data on population means for adaptive significance of fitness-related traits. In the present study, the role of climatic selection is evident from regression analysis with changes in annual average temperature of the sites of origin of populations along latitude as well as altitude.

Observation of granulations in the basal body of ovarioles and follicular dilatations for the determination of physiological age of Anopheles gambiae s.s.

Objective:To explore ovariole basal body granulations and follicular dilatations for determining physiological age inAnopheles gambiaes.s.(An.gambiaes.s.).Methods:Mosquitoes were collected by using window trap catch and identified morphologically.For the first lot ofmosquitoes,they were dissected,and ovary was left in distilled water for reading ovarian tracheoles and the second was cut and transferred to another blade in a physiological liquid for verification of ovariole basal body granulations.The same approach was followed with the second lot of mosquitoes where follicular dilatations were found after classic dilaceration of ovaries were transferred into physiological liquid.The other body parts of mosquitoes were used to identify the species of theAn.gambiaes.s.complex by PCR.Results:Among the 123An.gambiae s.s.of the first lot,the method of Detinova determined the age of 89 mosquitoes versus 114 for the observation of granulations(P>0.05).Among the 112An.gambiae s.s.of the second lot,the method of Detinova determined the age of 84 mosquitoes versus 93 for the observation of follicular dilatations(P>0.05).Unlike the method of Detinova,observation of follicular dilatations and basal body granulations of ovarioles were possible beyond the stage II Christophers.Conclusions:Overall,the observation of follicular dilatations and ovariole basal body granulations are reliable for the determination of the physiological age inAn.gambiaes.s.Furthermore,these two methods can be used beyond the stage II.

Physiological Age Status of Female Adults and Off-Season Survival of Rice Leaffolder Cnaphalocrocis medinalis in India

Rice leaffolder, Cnaphalocrocis medinalis, is one of the major foliage feeders found in the rice growing regions in India. When the crop was at maturity, numerous adults of rice leaffolder were found in the rice fields though the larval population gradually decreased, and no eggs were found on rice leaves. The population characteristics of C. medinalis were assessed based on the physiological age status of adults at different crop growth stages. Based on egg development within ovarioles, ovariole appearance number and colour of fat bodies, and characteristics of bursa copulatrix, physiological age status of the adults was described, which served as a basis for the determination of age composition. C. medinalis adults were found during the first week of August on rice plants, of which 44% were in Age 0 with immature ovaries, indicating immigrants. However, 28% adults each were at Ages 1-2 with developing ovaries, indicating local breeding population. The carryover and off-season survival of C. medinalis were also studied to determine the contribution of the alternative hosts in the population growth that helped in devising efficient management strategies. Rice was the most preferred host followed by Triticum aestivum, Echinochloa crusgulli and Brachiaria plantaginea. Various routes of the carryover of C. medinalis from season to season were discussed.

Methionine as a methyl donor regulates caste differentiation in the European honey bee(Apis mellifera)

Nutrition contributes to honey bee caste differentiation,but the role of individual nutrients is still unclear.Most essential amino acid contents,except that of methionine(Met),are greater in royal jelly than worker jelly.After〜3.5 i the Met content in the latter was slightly greater than in the former.Met is the major raw material used in the synthesis of S-adenosyl-L-methionine,an active methyl donor for DNA methylation,which is an epigenetic driver of caste differentiation.Here,we tested whether Met regulates caste differentiation in honey bees by determining its effects on the caste development of bees receiving four diets:the basic,basic+0.2%Met,basic+0.2%Met+20 mg/kg 5-azacytidine,and basic+20 mg/kg 5-azacytidine.The presence of Met decreased the adult bee body length and the numbers of ovarioles,indicating that Met may direct the development of female larvae toward worker bees.The upregulated expression of SAMS,Dnmtl,and Dnmt3 caused by Met exposure in 4-d-old larvae indicated that the worker-inductive effects of Met may occur through the promotion of DNA methylation.We investigated the co-effects of Met and glucose on bee development,and found that the effects of an increased glucose level on the number of ovarioles and body length did not strengthen the worker-inductive effects caused by Met.Our results contribute to caste development theory and suggest that Met-as a methyl donor一plays a regulatory,but not decisive,role in caste differentiation.