• Volume 99, Issue 2

      March 1990,   pages  91-174

    • Aspects of spermiogenesis inArrhenothrips ramakrishnae Hood (Insecta: Thysanoptera)

      T N Ananthakrishnan A Balu

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      Aspects of spermiogenesis inArrhenothrips ramakrishnae are described based on light microscopic and transmission electron microscopic studies.

    • Histological studies on femaleSetaria digitata (von Linstow 1906), a filaria of bovine,Bos indicus

      S William Decruse R Kaleysa Raj

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      The fine structure ofSetaria digitata based on histological assessment is described. The cuticle is thick and multilayered. The well developed longitudinal muscles consists of fibrillar zone only and cover about 65–70% of the circumferences throughout its body, the rest being occupied by the very voluminous lateral hypodermal chords. The digestive system is well developed and the intestine possesses a narrow simple tube consisting of a single layer of epithelial cells. The paired genital tubes run through almost the entire length of the body until the two uteri unite to form a short unpaired vagina. Morphologically distinct spermatheca is absent, but posterior part of uterus serves the function. Gradation of developmental stages—fertilized egg to microfilariae—occur from posterior to anterior part of uterus. The developing embryos are interconnected and also connected to the uterine wall. This condition commences from early embryogenesis and exists up to hatching stage. Probable function of these connections in the synchronised development of embryos and as ‘nutritive channels’ for the supply of nutrients has been discussed.

    • Influence of neem kernel extract on morphogenesis and vitellogenic oocyte development inTrogoderma granarium everts

      S Chellayan G K Karnavar

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      Neem seed kernel extracts adversely affect the growth and morphogenesis of insects. InTrogoderma granarium, neem seed kernel extract was found to inhibit normal pupal-adult development. The malformed adults comprised a heterogenous group of transitory forms between the pupal and adult types. Older pupae were less sensitive to the compound. In the seemingly normal surviving adults ofTrogoderma granarium a reduction in the number of vitellogenic oocytes was found. The active compound(s) in the neem seed kernel extracts is proposed to produce the observed effects by regulating morphogenetic hormone titres, though the precise mode of action cannot be safely defined.

    • Effect of plumbagin on haemocytes ofDysdercus koenigii F.

      B P Saxena K Tikku

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      Effect of plumbagin, a phytochemical, on the haemocytes ofDysdercus koenigii was studied after topical application. Scanning electron microscopical studies showed deformity in surface morphology in almost all the 5 types of haemocytes categorized in the bug, especially that of granular haemocytes and plasmatocytes, which are devoid of their filopods in the treated insects. The fat droplets of adipohaemocytes shrink while oenocytoid is affected to a lesser degree. Plasma membrane of all the cells becomes fragile leading to a gradual loss of cytoplasm and ultimately only a few interconnected cytoplasmic strands are left. Ultrathin sections revealed a highly vacuolized condition and disintegrating organelles which pass out of the cells due to ruptures of very thin plasma membrane. Total and differential haemocyte counts performed after 24 and 48h of treatment showed a drastic reduction of all the types i.e. the prohaemocytes disappear from blood, the number of granular haemocytes and plasmatocytes declines while oenocytoids and adipohaemocytes comprise the major part of counts. Because of the damages caused to haemocytes and the suppression of filopodial elongations of plasmatocytes and granular haemocytes (the types that are active in defense mechanism), it can be inferred that cellular defense reactions ofDysdercus koenigii are reduced after plumbagin treatment.

    • Changes in nucleic acids and protein content in relation to body size in the prawnPenaeuss indicus H Milne Edwards

      George Thomas A D Diwan

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      This study was carried out to find out the relationships of RNA, DNA content, RNA/DNA ratio and protein levels with different size length individuals ofPenaeus indicas. RNA, DNA content, and RNA/DNA ratio were found to be high in small sized prawns, with increased amount of protein. There was a decline in RNA concentration as size of the prawns increased, thus showing an inverse relationship. Though DNA values also showed a slight decline with increase in size, among large sized prawns there was a tendency to conserve DNA content. RNA/DNA ratio has been found useful in correlating growth (in terms of protein increase) only in small sized prawns.

    • Biology ofAphanogmus fijiensis (Fernere) (Hymenoptera: Ceraphronidae) a hyperparasite ofDiaphania indica (Saunders) (Lepidoptera: Pyralidae) throughApanteles taragamae Viereck (Hymenoptera: Braconidae)

      Clement Peter B V David

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      Studies were conducted on the hyperparasiteAphanogmus fijiensis (Fernere) (Hymenoptera: Ceraphronidae) to determine its biology throughApanteles taragamae Viereck (Hymenoptera: Braconidae).Aphanogmus fijiensis is a gregarious ectoparasite and developed on the prepupal and pupal stages of Apanteles taragamae present inside the host cocoon. Mean development time from egg to adult was 12–28 days at 26·43±2·53°C. There is no preoviposition period; the host is paralysed before oviposition, freshly formed to 3-day old cocoons are preferred for oviposition and mean longevity for both sexes was 4·86 days.

    • Influence of biochemical parameters of host plants on the biology ofDialeurodes vulgaris Singh (Aleyrodidae: Homoptera)

      R Sundararaj B V David

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      The influence of biochemical parameters of the host plants viz.Jasminum multiflorum Andr.,Jasminum sambac Ait.,Jasminum grandiflorum Linn.,Jasminum auriculatum Vahl.,Jasminum pubescens Willd. andJasminum flexile Vahl. on the biology of Dialeurodes vulgaris was studied. The results indicate remarkable variation in the biochemical parameters of host plants which affected significantly the biology of the insect. The per cent survival and growth index have been considerably low inJasminum pubescens, Jasminum auriculatum andJasminum grandiflorum and the same trend has been noticed with regard to fecundity and longevity also. The most preferred hosts have beenJasminum sambac andJasminum multiflorum. It is observed that high amount of phenol and excessive accumulation of sugars in host plants make them nonpreferred while high amount of amino acids makes the plants more preferred byDialeurodes vulgaris.

    • On reconfirming the evidence for pre-imaginal caste bias in a primitively eusocial wasp

      Raghavendra Gadagkar Seetha Bhagavan Rashmi Malpe C Vinutha

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      Caste is usually thought to be determined entirely in the adult stage in most primitively eusocial wasps and bees. A pre-imaginal caste bias has however been recently discovered in the primitively eusocial waspRopalidia marginata. This study also suggested that reigning queens and possibly other adults may influence the production of new queens and implied at least partial support to the parental manipulation or sub-fertility hypothesis for the evolution of insect sociality. The interest of these results prompted an attempt at their reconfirmation. Complete reconfirmation has now been obtained using data from an independent experiment and two additional methods of data analysis. We therefore conclude that caste is at least partly determined prior to eclosion in the primitively eusocial waspRopalidia marginata which lacks morphological differentiation between egg-layers and non-egg-layers.

    • Dynamics of a population ofCeriodaphnia cornuta Sars (Crustacea: Cladocera) from a seasonal pond in Madurai

      N Murugan

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      Investigation of the dynamics of a population ofCeriodaphnia cornuta indicated that the internal and external phenomena of clutch size and food supply were significant factors influencing population density and other population parameters. The relationships of clutch size with transparency and temperature were attempted. A single period of bisexual reproduction was noticed over a period of 12 months. The mean annual clutch size ranged from one to two eggs. Animals with 3 eggs were far fewer in percentage in the natural habitat. A low positive correlation of r=0·27 was recorded between mean brood size and body length, indicating that small body size naturally restricts the egg laying capacity of the females. The absence of size groups III and IV in the field samples was explained. The population parameters such as finite birth rate (B), instantaneous birth rate (b) population change (r) and death rate (d) were estimated from field data for this cladoceran.

    • Biofilm characteristics in coastal waters of Bombay

      R B Srivastava S N Gaonkar A A Karande

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      Field and laboratory studies were carried out to analyse the development of biofilms generated on various metallic and non-metallic coupons immersed in coastal waters of Bombay. It is observed that the nature of the biofilm formed not only varies from substratum to substratum but is also influenced by the quality of water, flow conditions and the biotic status of the seawater. The biofilms depending upon the degree of entrapment of the inorganic detritus have varying weights. The biofilms formed on metallic surfaces when compared with perspex surface, are both qualitatively and quantitatively richer. Cupro-nickel, despite its toxicity, supports denser film than the one developed on inert perspex surface. The metallic coupons, both inert and toxic, support thicker films in polluted waters than in clean waters.

    • Foreword

      T N Ananthakrishnan

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