• Volume 98, Issue 5

      September 1989,   pages  291-372

    • Morphometrics, micromorphology, microanatomy and cytochemistry of the gills of a swamp catfish,Chaca chaca (Ham.)

      Jagdish Ojha A K Das Bishakha Singh

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      Dimensions, micromorphology, microanatomy and cytochemistry of the gills of a swamp catfish,Chaca chaca have been investigated using morphometric, scanning electron microscopic, light microscopic and cytochemical techniques respectively. The findings have been correlated with the respiratory efficacy of the gill sieve and the physicochemical behaviour of the habitat of the fish.

      The filament number among 4 gill arches varies from 144–151 and does not show any significant (P>0·05) difference among themselves. The filament length shows heterogeneity in their relative dimensions at different points along the various hemibranchs of the 4 gills. Lamellar frequency (n) and area (bl) were 31·2 and 0·08316 mm2 respectively. The small gill area (13905·3 mm2) assigns comparatively low level of activity to the catfish. Total lamellar water flow of the gill sieve ofChaca was 20·123 cc/s.

      The heterogenous gill arch epithelium contained taste buds and mucous gland openings. Short and stumpy gill rakers signify carnivorous feeding habit of the catfish. The micropockets of the gill filament epithelium entrap some water molecules to protect the gills from desiccation, when the fish is temporarily exposed to water-land interface and acts as a regular source of oxygen to the fish during adverse ecological conditions.

    • Impact of mating on the post-embryonic development ofCoranus soosaii Ambrose and Vennison (Insecta—Heteroptera—Reduviidae)

      Dunston P Ambrose P Murphy Alexander

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      Post-embryonic development of assassin bugCoranus soosaii Ambrose and Vennison was studied in the offsprings of 4 categories of females, viz (i) virgins, (ii) mated once with a male of the same age, (iii) lived continuously with a male of the same age and (iv) lived with 3–4 males of different ages. Mating shortened the pre-oviposition period, enhanced the fecundity and hatchability, hastened the emergence and extended the adult longevity.

    • Effect ofAzadirachta indica andPongamia glabra leaf extracts on food utilization and modulation of efficiency of digestive enzymes inEuproctis fraterna (Lepidoptera: Lymantridae)

      S Sridhar J Sulochana Chetty

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      The effect of application ofAzadirachta indica andPongamia glabra leaf extracts on food consumption and utilization in fifth instar larvae ofEuproctis fraterna, a serious lepidopterous pest on castor,Ricinus communis, is assessed. Reduction in food consumption byEuproctis fraterna feeding on castor leaves treated with extract ofAzadirachta indica was 11% higher than that recorded for castor leaves treated withPongamia glabra. Consumption, assimilation, production and their rates showed a negative correlation with the concentration of the extracts used.

      The effect of administration of these two leaf extracts on efficiency of the digestive enzymes invertase, amylase and protease ofEuproctis fraterna was also assessed. A reduction in activity of these enzymes with the administration of increasing concentration of extracts was also observed.

      Leaf extracts of neem andPongamia appear to be most efficaceous in controllingEuproctis fraterna especially when they are administrated along with castor leaves in the fifth instar providing a suitable alternative to synthetic pesticides.

    • Insect growth regulator XRD-473 (OMS 3031), a prospective compound for control of mosquito vectors

      Dominic Amalraj R Velayudhan

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      Insect growth regulating activity of a substituted urea compound XRD-473 (OMS 3031) was evaluated against the target species viz.Culex quinquefasciatus, Aedes aegypti, Anopheles stephensi and non target speciesToxorhynchites splendens. This compound inhibited the emergence of all these mosquito species with EI50 values of 9×10−5, 1·09×10−4, 2·22×10−4 and 2·14×10−4 mg (ai)/l respectively. Emergence inhibiting activity of XRD-473 was found to be more than fenoxycarb, and S 21149 against one or other species. In stagnant polluted water, the activity of the compound againstCulex quinquefasciatus was for shorter duration of 5 and 10 days at 0·02 and 0·2 kg(ai)/ha respectively whereas in clear water the activity was for longer duration i.e. 11 and 17 days at the same dosage. However, in drain the activity was negligible i.e. 12 days at 2 kg(ai)/ha. More than two weeks control ofAedes aegypti was obtained in cement tank at the treatment rate of 0·2 kg(ai)/ha whereas at the lower dose of 0·02 kg(ai)/ha this compound was effective for less than a week.

    • Field life-tables and key mortality factors ofAchaea janata Linn on castor

      B B Gaikwad G G Bilapate

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      Field life-tables and key mortality factors of castor semilooperAchaea janata L. were studied on castor for the year 1985–86 and 1986–87. There were 4 regular overlapping generations during both the years. The parasitization ofAchaea janata larvae in early instars (I–III instar) by parasiteMicroplitis maculipennis (Sziepligetis) was 1·34, 4·41, 22·02 and 43·70% in first, second, third and fourth generation respectively during 1985–86. Similarly, the parasitization by same parasite was 44·12, 61·46 and 65·55% during second, third and fourth generation respectively in the year 1986–87. Key mortality factors and separate budget for each generations were prepared.

    • Maturity and breeding of the mud crab,Scylla serrata (Forskal) (Decapoda: Brachyura: Portunidae)

      P N Prasad B Neelakantan

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      Females ofScylla serrata attained sexual maturity after reaching 80 mm carapace width and above. Fifty per cent of females at size range 91–100 mm carapace width were sexually mature. The growth rate of abdomen width or length with respect to either carapace width or length was generally at much higher side in mature females than in the immature specimens. A sharp transition at 80 mm carapace width indicated the morphological changes accompanied with the sexual maturity. The relationship between abdomen allometry and carapace measurements was highly significant (P<0·001).Scylla serrata although bred all through the year, exhibited two peaks of breeding, one in between December–March and another in September–November. The sex-ratio in two biotopes varied considerably with the breeding season and size of the female population. The females were found to be in berried state in inshore and off-shore waters of Karwar at 90 mm carapace width and above. Spawning ofScylla serrata was found to occur only in inshore and off-shore but not in backwaters.

    • Induction of allotriploids in the hybrids ofOreochromis mossambicus female × red tilapia male

      K Varadaraj T J Pandian

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      Cent percent allotriploids were induced by heat shocking (42°C for 3 min) of 2·5 min old (post-fertilization)Oreochromis mossambicus eggs fertilized with (homozygous) red tilapia milt. Control diploid hybrids were red (orange) in colour. A few triploid hybrids displayed more patches of black pigmentation. Hence red and black colours are regarded as co-dominants. Survival of the allotriploids was higher than that ofOreochromis mossambicus autotriploids.

    • Nitrogen budget ofCallosobruchus maculatus larva developing in different host seed species

      J Chandrakantha S Mathavan J Muthukrishnan

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      Studies on effect of seed species and their interacting influence on food utilization ofCallosobruchus maculatus clearly pointed out that rates and efficiencies of nitrogen utilization are determined by the composition of the seed also. Of the 3 species of seeds tested,Vigna unguiculata has significantly more nitrogen and water per unit weight than the other two seeds,Dolichos lab lab andPhaseolus radiatus. With increasing nitrogen content of the seed, rates of feeding, assimilation and metabolism decreased. On the other hand efficiencies of assimilation and net production increased. Nitrogen assimilation efficiency ofCallosobruchus maculatus ranged from 76·6% inDolichos lab lab to 85·8% inVigna unguiculata. The efficiency of accumulation of assimilated nitrogen was around 82%. The less nutritiousDolichos lab lab contributed more to the observed variance in the efficiencies of assimilation and production. The low efficiencies may be attributed to the presence of protease inhibitors.

    • Foraging activity and temperature relations in the ponerine antHarpegnathos saltator Jerdon (Formicidae)

      T Shivashankar H C Sharathchandra G K Veeresh

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      Harpegnathos saltator Jerdon constructs nests in the shade of plants and are strictly individual foragers. The nest entrance is barricaded by seeds, seed stalks and faecal pellets of rodents, the function of which is not clear. The diurnal foraging activity is controlled by a combination of surface temperature and light. High midday surface temperature resulted in the bimodal transit activity in a day.

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