• Volume 96, Issue 4

      July 1987,   pages  349-435

    • Host dependency among haematophagous insects: A case study on flea-host association

      R S Prasad

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      Obligatory haematophagy is the end result of long standing interspecific associations. Present day specificities to host, blood meal and physiological stage of the host are all offshoots of the primitive interspecific associations. The cause/effect relationship of these dependencies and specificities are probably based on the route through which haematophagy evolved in different groups of insects.

      In the present analysis, flea-host association is taken into consideration. It is possible to find an array of host relationships ranging from promiscuous and catholic host associations to strict ones. In general 3 categories may be recognized. In fleas likeXenopsylla cheopis a utilizable protein in an optimum concentration gives the necessary stimuli for maturation (Cheopis-type), while in a second group the stimuli is provided by certain circulating hormones of the host (Cuniculi-type) as seen in rabbit fleaSpitopsyllus cunicuti and in a third grnup (Monositus-type) a priming period characterized by tissue fluid feeding and neosomy is necessary before whole blood diet can stimulate maturation as exemplified byTunga spp.

      It appears that vertebrate associations of Siphonaptera initiated as adaptations to the nest microhabitat and haematophagy and adaptations to physical/chemical factors of epidermal habitat being subsequent developments.

    • Effect of okra fruit blocks, seeds and pericarp on post-embryonic development ofEarias vittella (Fab.) in relation to some phytochemicals of selected okra genotypes

      Ram Singh

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      Post-embryonic development of the spotted bollworm,Earias vittella (Fab.) studied on pericarp, seeds and fruit blocks of 8 okra genotypes, revealed significant differences in larval survival, larval period, pupation and adult emergence among genotypes as well as fruit components. First instar larval survival on fruit components was in the order of fruit blocks> seeds> pericarp> axil. Mean total developmental period was 24·20, 21·33 and 21·09 days on pericarp, seeds and fruit blocks, respectively. Likewise pupation was 25·30, 65·42 and 71·58% on pericarp, seeds and fruit blocks, respectively. Primary phytochemicals, like protein, free amino acids, total sugars, non-reducing sugars and moisture content in pericarps were in higher concentrations in comparison to seeds and whole fruits. These compounds also differed significantly among genotypes. There were positive correlations between the pest survival and these nutritional compounds. Tannins were 0·35, 0·23 and 0·29% in pericarp, seeds and whole fruits, respectively. Tannin content was significantly higher in pericarps of tolerant genotypes and showed significant negative correlation (r=−0·81) with fruit borer survival.

    • In vitro studies on the involvement of brain and gonad in the functional differentiation of prostate gland inCryptozona belangeri (Deshayes) (Mollusca: Gastropoda)

      Uma Natarajan Vijayam Sriramulu

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      Prostate glands from mature and juvenileCryprozona belangeri were culturedin vitro for 8 days in single or double association with cerebral ganglia. visceral ganglionic complex and gonads obtained from adult snails. The histology of the glands was studied and compared with those of normal glands and with glands culturedin vitro without any organ association. Functional differentiation was not evident in glands cultured in isolation or in single association with gonad or brain. In double associations, involving cerebral ganglia, visceral ganglionic complex and gonad response from the gland was obtained only when the gonad was involved. The cerebral ganglia and visceral ganglionic complex acting through the gonad elicit differential responses from the prostate gland. It was concluded from thein vitro studies that the prostate gland may be dependent on a gonadal hormone for functional differentiation, which in turn is under the control of trophic factors released from the brain.

    • Life and fertility tables ofAchaea janata Linnaeus on castor

      A N Byale G G Bilapate

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      The life fecundity tables were constructed whenAchaea janata Linnaeus reared on castor leaves in the laboratory. The net reproductive rate (Ro) was 467·57 females/female/ generation in a generation time of 37·99 days. The intrinsic rate of natural increase (rm) was 0·16l8 female/female/day. In the stable age-distribution, 99% contribution was made by immature stages.

    • Cadmium induced vertebral deformities in an estuarine fish,Ambassis commersoni Cuvier

      V Pragatheeswaran B Loganathan R Natarajan V K Venugopalan

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      Amhassis commersoni was treated with 3 different concentrations (0·1, 0·25 and 0·5 ppm) of cadmium upto 120 days. Fishes treated in higher concentrations developed vertebral deformity and the deformation was prominent after 89th and 115th day. The levels of the vertebral minerals such as calcium, magnesium and phosphorus lowered in all exposure concentrations and minerals lost were directly proportional to the toxic concentrations. Nearly 2/3 of skeletal mineral composition was eliminated in the deformed fish. Vertebral fracture was attributed mainly to the large amount of vertebral components eliminated from the vertebrae. Vertebral cadmium accumulation was also linear in relation to the experimental concentrations.

    • Distribution and population dynamics of soil nematodes in a tropical forest ecosystem from Sambalpur, India

      G B Pradhan M C Dash

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      An ecological study on soil nematodes was made in a tropical deciduous forest ecosystem. Seventeen species of nematodes were identified of whichRotylenchus sp. was the dominant plant parasitic form andAcrobeloides sp. was the dominant microbivore species. The mean annual importance value for the miscellaneous feeders, plant parasites, microbivores and predators were 57·5, 22·5, 12·6 and 7·4 respectively. The Shannon index of general divérsity was maximum during February (1·73) and minimum during June (1·41). Nematodes were distributed in clusters resulting in so called pocket effect. Of the total nematodes 88·4% occurred in the top 10 cm soil during the peak period of density and the microbivores were more frequent in the top 5 cm soil due to the litter layer. Total nematode density ranged from 15·1 × 104/m2 (May) to 66·1 × 104/m2 (November). Monthly mean nematode biomass was 18·86 ± 8·36 mg dry wt/m2. Temperature, soil organic carbon and soil total nitrogen apparently played an important role in regulating the nematode population.

    • Biology ofNyphasia apicalis Gahan (Coleoptera: Cerambycidae) with particular emphasis on emergence and imaginal life

      T N Khan T Khan

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      Biology of the sapwood borer,Nyphasia apicalis Gahan is discussed with special reference to some aspects of adult behaviour, Development and survival of eggs and pupae are dependent on high humidity. Life-cycle is annual but may be prolonged to the next year. Adult emergence mainly occurs in June and July and is synchronized with the onset of rains. Beetles are diurnal, being most active in bright sunlight and are flower visitors feeding on different floral components. They are sexually mature on emergence and mate soon afterwards usually on the material from which they have emerged. Females prefer logs after a month of felling for oviposition. Logs lying in shady areas are avoided by the ovipositing females.

    • Micromorphology and cytochemistry of the branchial glands of the freshwater mullets,Rhinomugil corsula (Ham.) andSicamugil cascasia (Ham.)

      Jagdtsh Ojha A K Mishra

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      Scanning electron microscopic studies of the gills ofRhinomugil corsula andSicamugil cascasia reveal interspecific variations in distribution, density and architectural plan of the mucous glands and the cytochemical nature of the mucus secreted by them. The gill arch and gill filament epithelium ofRhinomugil corsula contains numerous mucous cells, butSicamugil cascasia has few mucous gland openings on its gill arch and gill filament epithelium. In both the mullets the secondary lamellar epithelium lacks mucous gland openings, which is discussed. The presence of blue, blue-red, red and red-blue mucous cells [AR-pH 2·5 periodic acid-Schiff] in the gills ofRhinomugil corsula signifies the acid and neutral nature of the glyco-protein of the mucus secreted by them. However, the presence of only blue mucous cells indicates the presence of acid glycoprotein in the mucus of the gills ofSicamugil cascasia.

    • Nature of resistance in selected rice varieties and population fluctuation of green leafhoppers,Nephotettix virescens (Distant) andNephotettix nigropictus (Stål)

      Kasi Viswanathan M B Kalode

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      In multiple-choice tests with 30-day-old plants of resistant and susceptible varieties, both the species of green leafhoppers,Nephotettix virescens (Distant) andNephotettix nigropictus (Stål) exhibited relative non-preference to highly resistant varieties (Ptb 2, Ptb 7 and Ptb 18) both for settling and oviposition. Even when 100 first instar nymphs were caged on individual 25-day-old plants of highly resistant varieties, the plants suffered very low damage and also induced high mortality of nymphs. Different ages of the plants had no influence on the antibiosis mechanism of resistant varieties. Feeding behaviour studies revealed that both the species made more punctures and excreted less honeydew while feeding on resistant varieties than on susceptible ones. Histological studies indicated no mechanical barrier for feeding in resistant varieties.

      Field investigations indicated that resistant varieties viz Ptb 18, Ptb 2 and Ptb 7 harboured less population of green leafhoppers and had relatively nil or very low incidence of tungro virus disease. An year round survey in the rice ecosystem and marshy habitat whereLeersia hexandra grows in abundance revealed that although both the species coexisted in rice fields,Nephotettix nigropictus alone was present in the marshy habitat.

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