• Volume 99, Issue 6

      November 1990,   pages  419-549

    • Development of visual cells in the toadBufo melanostictus (Schneider)

      Sultana Niazi I A Niazi

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      Differentiation of visual cells inBufo melanostictus begins after hatching at gill bud stage. It is indicated by emergence of cytoplasmic buds from the outer nuclear layer of the retina. Each bud contains an apically located vacuole which soon disappears from all cells. Cones and rods start differentiating simultaneously but the majority of early cells are rods. Single cones, red rods and double cones can be identified by the stage when the operculum is formed. Up to the beginning of hindlimb morphogenesis rods remain the most numerous but later single cones attain approximate numerical equality with rods and the tadpole retina becomes a truly duplex retina. Red rods of tadpoles are structurally different from those of adult. As in the accessory members of double cones a paraboloid develops in the myoid region of the inner segment of red rods also and persists throughout larval life. During metamorphosis green rods appear, cone outer segments become sharply pointed, myoid develops in the red rods replacing the paraboloid which disappears along with its glycogen but there is no change in the double cones. After metamorphosis number and size of red rods increase greatly transforming the duplex retina of the tadpole into a predominantly rod retina adapted for scoptopic vision of the nocturnal adult.

    • Female accessory glands and sperm reception in Tingidae (Heteroptera)

      David Livingstone M H S Yacoob

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      Studies on the anatomy of the female internal organs of reproduction and the intromittent organs of 34 species of Tingidae confirm the absence of spermathecae. The accessory glands are vesicular and primitively unpaired. There is no vermiform gland and the term pseudosperrnatheca, introduced by Carayon in heteropteran literature, is a misnomer. The lateral oviduct and all the 7 pedicels of each ovary develop a permanent swelling in the middle that receive the spermatozoa, syringed into them through the minute pores of the armature of ejaculatory pouches of the endotheca, when it is lodged inside the bursa during copulation. The ejaculatory pouch and the bursa are so designed and adjusted for the purpose of sperm transmission. In a few species of Tingidae a median diverticulum that arises from the endotheca plugs the unpaired vesicular accessory gland, preventing wrongful lodging of the ejaculatory pouch and such a mechanism, not known so far, has been described as a unique feature. A scheme to trace the evolution of accessory gland, from a median unpaired contacaderine condition, to a paired independent gland, having its opening either in front or behind the lateral oviduct, has been detailed.

    • Stridulation in the coconut rhinoceros beetleOryctes rhinoceros (Coleoptera: Scarabaeidae)

      A Mini V K K Prabhu

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      The coconut rhinoceros beetleOryctes rhinoceros produces different kinds of stridulatory sound under different conditions. Intense stridulations are made quite frequently by the male during courtship and mating attempts. Males also produce characteristic stridulations during aggressive encounters with other beetles, and distress stridulations, when disturbed manually. Females also stridulate, though less frequently. Sexually immature females produce feeble repellence stridulations while courted by males. Gravid females, when confined with males, are found to mimic the courtship and mating behaviour of the males, meanwhile producing intense stridulations resembling male courtship and mating stridulation. This behaviour, presumably has an ovipository motive and, to our knowledge, is the first instance of ‘’pseudomale’ activity to be reported in insects.

      Stridulatory mechanism comprises rubbing of a specialised region along the margin of the apex of the elytron —the pars stridens, against a series of striations —the plectrum, occupying the dorsum of the 7th abdominal tergite. Stridulation is possible with a single pars stridens, either of the left or right elytron, both being identical. No sexually dimorphic difference is apparent in the pars stridens. Plectral structure exhibits sexual dimorphism, being much prominent in the male.

      Wing-locking is necessary to keep the elytra in the stridulatory position. Locking is effected by a longitudinal flange along the median side of one elytron (either the left or right, irrespective of the sex) fitting into a corresponding depression along the other. This differs from the reported cases in other coleopterans in which the flange of the left elytron extends under the right when locked.

    • Genetic and morphological variations in the Indian mackerelRastrelUger kanagurta (Cuvier 1817) from the Goa region

      Maria R Menezes Sandeep Naik Maria Martins

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      The population structure ofRastrelliger kanagurta (Cuvier 1817) from two localities off Goa (Arabian sea) was assessed from genetic and morphological characters. Seventeen loci were examined from 8 enzymes, sarcoplasmic proteins and hemoglobins. The allele frequencies were not significantly different between the two localities. Nei’s genetic distance value was 0-0017. The proportion of polymorphic loci at the 1% level was 47-1 and 52–9%. The level of genetic variation, estimated by average observed heterozygosity, was 5–8 and 6–6%. The sarcoplasmic protein-2 locus was found to be highly polymorphic. Significant (P< 0-001) departures from Hardy-Weinberg expectations were observed at this locus. About 67–89% of the variation in meristic characters was found to be within the groups.

    • Moulting patterns in the silkworm,Bomhyx mori L. (PM × NB4D2) under different photoperiodic conditions

      N Sivarami Reddy T Pavan Kumar K Sasira Babu

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      Moulting patterns in the silkworm,Bomhyx mori L. (PM × NB4D2) under different photoperiodic conditions were studied. Moulting phenomenon, inBombyx mori seems to be under the control of the circadian phenomenon. The peaks for the second moult were observed during the dark phase of the photoperiodic schedule expressing nocturnal predominancy. Consequently these peaks for consecutive moults moved into the light part of the 24 h cycle. This clearly demonstrates the instar dependency of the moulting expression. Under LL condition, a damp-out situation in moulting was observed. Moulting durations were greatly affected by photoperiods. Shortest moulting durations were recorded for LD 11:13.

    • Effect of insect growth regulators on hatching of eggs of three vector mosquito species

      V Vasuki

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      Hatchability of eggs ofCulex quinquefasciatus, Aedes aegypti andAnopheles stephensi was studied by exposing freshly laid (0–1 h) and older (12–18 h) eggs to varying concentrations (0–0001–l-0mg/l) of 6 insect growth regulators viz. OMS 3019, OMS 3007, OMS 2015, OMS 3031, OMS 3013 and OMS 3009. In all the 3 species, dosage dependent response was observed. The response was also dependent on the age of eggs. Among the 6 IGR compounds OMS 3031 was found highly active resulting in maximum reduction in hatching of freshly laid eggs ofAnopheles stephensi (99-95%) followed byAedes aegypti (89–9%) whereas 50% inhibition in hatching occurred in older eggs ofCulex quinquefasciatus exposed to OMS 3009 at the same dosage. Dose, age and dose and age dependent hatching was evident in eggs of the 3 test species exposed to insect growth regulators OMS 3019, OMS 3013 and OMS 2015. Higher proportion of unhatched eggs with varying abnormalities was noticed in test species. Percentage mortality observed was higher in first instar larvae hatched from treated eggs reared in untreated water. Therefore, insect growth regulators have great potency in suppressing the population by affecting hatching of mosquito eggs in addition to inhibition of adult emergence, thus providing a useful tool for integrated vector management.

    • A feeding test to identify rice varieties resistant to the leaf folder,Cnaphalocrocis medinalis (Guenee)

      J S Bentur M B Kalode

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      Dynamics of leaf feeding by the larvae of rice leaf folderCnaphalocrocis medinalis (Guenee) was studied under greenhouse conditions to develop a feeding test to identify varietal resistance. Area of leaf damaged by larvae during their development indicated that first 3 instars accounted for only 8-06% and V instar alone for 66-3% of the total feeding. In view of the highest feeding rate and the longest feeding duration, V instar was chosen for feeding test. No significant differences in area of leaf damaged were recorded when V instar larvae fed for 48 h on 30, 45 and 60 days old plants or when leaf nitrogen content varied from 2–3·4%. Inherent variability among individual larvae in feeding rate could be maintained within acceptable limits with 5 replications.

      The proposed feeding test involved caging of individual V instar larvae for 48 h on 30–45 days old plants of test varieties and recording area of leaf damage. The test revealed varietal differences in area of leaf damaged by the leaf folder and displayed consistency over time. Based on feeding test, 19 rice varieties have been identified as resistant against leaf folder.

    • Inherited and rearing components of aggressive dominance and autonomic reactivity in the rat

      Sunitha Shankar Mewa Singh

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      On the basis of their scores in the open field test apparatus and ‘limited access’ competition, rats were divided into high and low aggressive and high and low reactive lines. Intrastrain breeding experiments were conducted across 3 generations to determine the heritability of aggressive behaviour and reactivity. In each generation, the animals of each strain were reared under ‘normal’, ‘crowded’ and ‘food restricted’ conditions to determine the extent of the influence of rearing environment on these behaviours. The genetic and environmental contributions to aggression and reactivity were further investigated through reciprocal cross matings and foster rearing. In most of the cases, environmental factors showed significant but varied and unpredictable influences, whereas the genetic factors were more consistent in their effects.

    • Effect of imipramine and amitriptyline on circadian locomotor activity rhythm in the field mouseMus booduga

      P Subramanian R Subbaraj

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      We have performed experiments on the influence of imipramine and amitriptyline (antidepressant drugs) offered through drinking water on the period length (τ) of the circadian locomotor activity rhythm in the field mouseMus booduga under continuous darkness (DD). Ingestion of imipramine to mice under freemnning conditions caused lengthening of the activity rhythm whereas amitriptyline caused dissociation of activity components. Furthermore, the amount of activity (α) is significantly reduced (P< 0-005) during imipramine as well as amitriptyline treatment. The action of these antidepressants may be explained by their action on serotonergic terminals in the suprachiasmatic nucleus, the putative circadian pacemaker in mammals.

    • Mineralization of phosphorus by faecal phosphatases of some earthworms of Indian tropics

      R V Krishnamoorthy

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      The casts of earthworms contain greater amounts of extractable inorganic phosphate than underlying soils. Casts contain higher phosphatase activity than that occurs in undigested soil, which increases the inorganic phosphorus released by mineralization. Of the 4 species compared,Perionyx excavatus showed a higher faecal phosphatase activity. Composition of casts vary with species. pH increases and nutrients accumulate in worm-activated soils. Based on the data on surface cast production, it is estimated that grasslands around Bangalore show a phosphorus turnover of about 55 kg ha−1 y−1, and the woodlands, 38 kg ha−1 y−1.

    • Production of rotifer,Brachionus plicatilis Muller fed with different cell densities of microalgae,Chlorogibba trochisciaeformis Geiter

      A S Rafiuddin Kusuma Neelakantan

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      The production dynamics such as growth rate(K) doubling time(Dt) and production (ml−1 d−1) on rotifer,Brachionus plicatilis was studied in different cell densities of microalgae,Chlorogibba trochisciaeformis. A significant increase in rotifer production was achieved at a density of 50x 106Chlorogibba trochisciaeformis cells ml−1.

    • Colonization of marine foulants at a power plant site

      N Sasikumar K V K Nair Jayapaul Azariah

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      Observations were made on the colonization of test panels (8×5 cm) by fouling organisms in the coastal waters and the cooling circuit (forebay) of Madras Atomic Power Station for a year. In coastal waters, hydroids settled as a pioneer species followed by barnacles and ascidians, whereas at the forebay, sea anemones were the important settlers. Species abundance, diversity indices and fouling biomass showed relatively low values at the forebay as compared to coastal waters. Species richness however was more in forebay than in coastal waters. Low species diversity with high species richness indices observed at the forebay could be attributed to species selection under altered environmental factors (chlorine levels, high flow rates and lack of predators).

    • Human evolution from the Miocene to the Present

      Shama Barnabas

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      Based on morphological, palaeoanthropological and molecular biological studies, human evolution from the Miocene to the Present has been reviewed. The initial divergence of orangutan from the hominoid stock, the divergence of man from the last common ancestor with the African apes, the origin and expansion ofHomo lineage and the advent of modern man have been discussed.


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