SCANNING ELECTRON MICROSCOPY OF ANTENNAE OF COCCINELLA SEPTEMPUNCTATA (COCCINELLIDAE: COLEOPTERA)

Scanning electron microscopy was done to describe the morphology of antenna of adult male and female ladybeetle, Coccinella septempunctata. Eleven‐segmented, scaly antenna was 950 μm in male and 980 μm in female. Electron micrographs reveal the occurrence of eight types of sensillae, viz. chaetica (Ch), trichoidea (Tr), basiconica (Ba), campaniformia (Ca), ampucellaceous (Am), scolopalia (Sc), placoidea (Pl) and hook shaped sensilla on the antennae of male and female ladybeetles. Ch had long external‐process, with base surrounded by membranous socket and the length was 60 and 70 μm in male and female ladybeetle, respectively. Sensillae Tr were distally curved and inserted into depression, 9.0 and 15 μm long in male and female ladybeetle, respectively. Sensillae Ba were cuticular peg‐like and 0.57 and 0.70 μm long on the male and female antennae. Sensillae Ca were small dome‐like and had diameter of 3.0μm in both the sexes. Sensillae Am were pit‐like in appearance and the diameter of the pit was 1.2 and 1.5 in male and female ladybeetle, respectively. Sensillae Pl were elliptical sunken plates like in both the sexes. Sensillae Sc were broad at their apex and pointed at their tip, 2.5 μm. A single hook‐shaped sensilla of 21.0 μm in length was present on male antenna only. Ch, Ca, Am, and Pl were almost similar in numbers in both the sexes. Sensillae Tr were more numerous on the male antenna and Ba were more numerous on the female antenna.     

Effect of photoperiod on slow and fast developing individuals in aphidophagous ladybirds,Menochilus sexmaculatus and Propylea dissecta (Coleoptera: Coccinellidae)

The effects of environmental parameters on insect development have been studied extensively. But the reasons for 2 differential developmental rates within same cohort under varying environmental factors have not been explored. For the purpose, in this study the existence and stability of slow and fast development under 5 photoperiods (i.e., 8L: 16D, 10L : 14D, 12L : 12D, 14L : 10D and 16L : 8D; light and dark hours per day) and its effect on body mass and reproductive attributes in 2 aphidophagous ladybirds, Menochilus sexmaculatus (Fabricius) and Propylea dissecta (Mulsant) was examined on Aphis craccivora Koch at 27 ± 1 °C temperature. A clear bimodal (2 peaks, where the first peak represented the fast developing and the 2nd peak slow developing individuals) pattern of distribution at each photoperiod was found. The proportion of slow and fast developing individuals in a cohort differed with photoperiods. The slow developing individuals were more in numbers at 8L : 16D, in equal numbers at 14L : 10D and in less numbers at 16L: 8D, indicating that the variation in emergence was owing to exogenous cues influenced differential rates of mortality. Slow developing individuals had female biased sex ratio, higher longevity and lower body mass than fast developing individuals. Fast developing females laid higher numbers of eggs with higher egg viability than slow developing females. Study of such variations in development at different photoperiods is helpful to understand its role in the development of insects particularly ladybirds and permits the selection of fast developing bioagents for their use in biocontrol of pest species.     

Conspecific interference by adults in an aphidophagous ladybird Propylea dissecta (Coleoptera: Coccinellidae): effect on reproduction

The effects of conspecific adult interference on the reproductive output of an aphidophagous ladybird, Propylea dissecta (Mulsant) were investigated. Ovipositing females were subjected to physical interference with conspecific adults (0 to 4 males or females) in Petri dishes and the effects on egg cannibalism, oviposition and egg viability were recorded. The absence of interference was related to the lowest egg cannibalism (0.00%) and higher fecundity (336.30+/-32.16 eggs) and egg viability (95.83+/-1.60%). Fecundity decreased with increasing physical interference from either sex. Egg viability declined with increasing male density, but was not influenced by conspecific females. In a second experiment, evaluating the role of conspecific adult chemical tracks on fecundity and egg viability, it was observed that adult chemical track density (fresh and ten-day-old) was negatively correlated. Egg viability was not affected by the presence of adult chemical tracks. The decrease in fecundity was not affected by the sex of the adults making the tracks, thus revealing that the chemical constitution of these deterrent compounds was not sex-specific. Conspecific interference in a Petri dish reduces reproductive output, as a result of physical interference and response to what seem to be oviposition-deterring pheromones present in adult tracks.     

Evolutionary significance of promiscuity in an aphidophagous ladybird, Propylea dissecta (Coleoptera: Coccinellidae)

The short- and long-term consequences of monogamy and promiscuity in an aphidophagous ladybird, Propylea dissecta (Mulsant) in terms of reproductive performance and offspring fitness were investigated. Promiscuous females were more fecund and laid more viable eggs than monogamous ones. Amongst promiscuous females, those mated with multiple males (freedom for mate choice) had significantly higher reproductive output than those mated daily with a new unmated male. The increased reproductive output of females mated with an unmated male each day in comparison to monogamous ones might possibly be a result of their increased ejaculate size. The further increase in reproductive output, when a female was allowed to choose a mate, may be because of repeated preferential mating with the fitter males. Results on long-term consequences of promiscuity revealed faster development and increased survival in offspring of promiscuous females at 25, 27 and 30 degrees C. The percent adult emergence was more strongly influenced than development by the mating regime. There were no statistically significant differences in survival of offspring of promiscuous females (mate choice) at the three temperatures, while the percent survival of offspring of monogamous females differed significantly. Offspring of promiscuous females (mate choice) were fittest in terms of development and survival, which indicates their probable better genetic constitution and subsequently that of chosen mates. Thus, promiscuity has both short- and long-term benefits and is advantageous to ladybirds. The presence of long-term benefits in terms of fitter offspring probably indicates the evolutionary rationale behind the prevalence of promiscuity in ladybirds.     

Identification of a sulfonoquinovosyldiacylglyceride from Azadirachta indica and studies on its cytotoxic activity and DNA binding properties

Chromatographic separation of the methanolic extract of the leaves of Azadirachta indica led to the isolation of a sulfonoglycolipid characterized as a sulfonoquinovosyldiacylglyceride (SQDG), by extensive 2D NMR and mass spectral analysis. SQDG induces apoptosis in a dose dependent manner with IC(50) 8.3 μM against acute lymphoblastic leukemia (ALL) MOLT-4 cell lines. The compound showed significant DNA binding properties as evidenced by the enhancement of melting temperature and perturbation of the characteristic B-form in CD evidence of calf thymus DNA. The DNA binding was also characterized by isothermal calorimetry where a predominantly enthalpy driven binding to CT DNA was revealed.     

Diel Rhythmicity of Certain Life Events of a Ladybird, Propylea dissecta (Mulsant)

The diel rhythms of certain life events, viz. mating, oviposition, hatching, moulting, pupation and eclosion were investigated in ladybird, Propylea dissecta. The peaks of activity and major portions of all life events were recorded in the scotophase. Mating, oviposition and hatching rhythms did not change with days and were thus probably endogenous in nature. The predominant occurrence of life events in the scotophase is probably owing to the foraging rhythms, which occur in the photophase as evinced by literature.     

Ovipositional Rhythmicity in Ladybirds (Coleoptera: Coccinellidae): A Laboratory Study

Complete and diel ovipositional rhythms have been observed in three aphidophagous ladybirds (Coleoptera: Coccinellidae): Coccinella septempunctata Linnaeus, Coccinella transversalis Fabricius and Propylea dissecta (Mulsant) for the first time. The complete ovipositional rhythm could be described in terms of a polynomial curve and daily fluctuations in all three species. In the diel cycle, all three ladybird species oviposited significantly in the scotophase. C. septempunctata females preferred to oviposit at the end of scotophase in the early morning hours (0300-0700), P. dissecta laid most eggs in the middle of scotophase during the night (2100-2300), and C. transversalis laid most at the beginning of the scotophase at dusk (1700-1900). While the diel ovipositional rhythm of C. septempunctata and P. dissecta did not differ between days, that of C. transversalis changed dramatically; there was a single peak on the first and second day of observation, and four oviposition peaks on the fifth day with the peaks being situated in the two hours preceding and succeeding the onset and end of the scotophase. Diel rhythms of C. septempunctata and P. dissecta appear to be endogenous in nature while that of C. transversalis is partly modified by exogenous factors.     

Myliobatid and pycnodont fish from the Late Cretaceous of Central India and their paleobiogeographic implications

Bulk sampling from Upper Cretaceous (Maastrichtian) Deccan volcano-sedimentary sequences at Kisalpuri (District Dindori, Madhya Pradesh) and Pisdura–Dongargaon (Chandrapur District, Maharashtra) in Peninsular India has yielded the dental remains of myliobatid and pycnodont fish. This fish fauna comprises Igdabatis indicus, Pycnodontoidea indet. and Pycnodontidae indet., and resembles assemblages known from Upper Cretaceous deposits in Africa and Europe. While paleobiogeographically speaking, the presence of Igdabatis suggests a series of shallow marine dispersals that may have occurred between Africa and India, possibly along the margins of the Kohistan–Ladakh island arc during the latest Cretaceous; the record of pycnodont fish favours instead a Gondwanan dispersal event.     

Prey quality dependent growth,development and reproduction of a biocontrol agent,Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae)

Growth, development and reproduction of a ladybird beetle, Cheilomenes sexmaculata (Fabricius) were investigated in relation to seven aphid species, viz. Aphis craccivora Koch, Aphis gossypii Glover, Rhopalosiphum maidis (Fitch), Myzus persicae (Sulzer), Uroleucon compositae (Theobald), Lipaphis erysimi (Kaltenbach) and Aphis nerii Boyer de Fonscolombe on specific hosts. Maximum prey consumption, percent larval survival, developmental rate, weight of different life stages, percent adult emergence, adult longevity and fecundity of C. sexmaculata were recorded on A. craccivora, and minimum on A. nerii. A linear relationship was found between development rate and weight of adult, daily prey consumption and relative growth rate, log weights of adult males and females, and female longevity and total fecundity. On the basis of overall performance of ladybird the order of suitability of prey species was A. craccivora>A. gossypii>R. maidis>M. persicae>U. compositae>L. erysimi>A. nerii.     

Optimal number of matings in two aphidophagous ladybirds

Abstract.  1. The present study was designed to identify the optimal number of matings required for maximum fecundity and egg viability in two aphidophagous ladybirds, Cheilomenes sexmaculata and Propylea dissecta .
2. For this purpose, ladybirds were subjected to different numbers of matings and the reproductive responses were recorded thereafter.
3. The Gompertz model was used to draw asymptotic graphs for fecundity and per cent egg viability in both ladybird species. Ninety-five per cent and 50% of maximum theoretical fecundity and per cent egg viability were predicted from the model.
4. Ninety-five per cent maximum theoretical fecundity was obtained after 13.25 and 12.95 matings in C. sexmaculata and P. dissecta , respectively; and 8.95 and 11.25 matings were required for 95% maximum theoretical per cent egg viability in C. sexmaculata and P. dissecta , respectively.
5. The results of these experiments clearly support the existence of an optimal number of matings in these two ladybird species leading to maximum adult fitness.