• Volume 92, Issue 1

      January 1983,   pages  1-85

    • Condition factor ofAmblypharyngodon chakaiensis Babu and Nair in the Chakai boat channel (Trivandrum-Kerala-India)

      N Babu N Balakrishnan Nair

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      Condition factor (K) and relative condition factor (Kn) ofAmblypharyngodon chakaiensis Babu and Nair males and females respectively have been studied in relation to the various months of the year and length groups. No significant correlation exists between the proportion of the males in the population and value of condition factor (K). On the basis ofK andKn and the various length groups in respect of males and females are arranged into three classes and their incidence in the pre-spawning, spawning and post-spawning seasons were represented. In femalesKn showed significant positive correlation with gonadosomatic index. The size at first maturity observed by direct observation of the gonads in females and males agrees with the inflexions on the curve depictingK andKn with respect to length groups. The influence of feeding intensity onK does not seem to be quite apparent inA. chakaiensis. The steady fall inK in the males seems to be related to the decrease in the percentage occurrence of males of these length group in the sample.

    • Gut spore composition and influence of fungal host on the rate of mortality and post-embryonic development inTiarothrips suhramanii (Ramk.)

      T N Ananthakrishnan B Padmanaban K Dhileepan

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      Studies on the spore composition of the gut of the adult idolothripine sporophagous speciesTiarothrips subramanii (Ramk.) indicated a greater preference forAnthostomella consanguinea as compared to others (viz., A. phoenicicola, A. sepelibilis, Pestalotia algeriensis, Melanographium citri, Phoma sp., Diplodia sp., Gnomonia sp., Stigmina palmivora). The rates of development and mortality were higher when developing instars were reared onA. phoenicicola andP. algeriensis respectively.

    • Response of some freshwater micrometazoans to DDT

      M P Sharma A K Dattagupta

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      The response of a few members of freshwater micrometazoans to DDT have been ascertained by conducting laboratory and field bioassay experiments. The organisms tested in laboratory bioassays, have been found to respond at low concentrations with LC50 ranging between 10 and 49 ppb.Cyclops sp. andAsplanchna brightwelli respond to higher concentrations of DDT with LC50 as high as 515 ppb and 2218 ppb respectively LC50 for the larvae ofCulex fatigans has been found to be 180 ppb. In the field test of 70 ppb of DDT was applied and repeated after 23 days. The response of organisms is similar in both the treatments. The population ofC. cornuta andM. brachiata reappeared after 22 days of the treatment whereas,D. excisum andN. kamakhiae failed to reappear. Analysis of the bottom soil of the treated tank revealed the presence of DDD, DDE and DDT. Some secondary effects of the DDT treatment have also been observed and discussed.

    • Effects of body size on the rate and pattern of ammonia excretion in an air-breathing fish

      Geetha Belliyappa Nirupa Krishnan S Ravichandra Reddy

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      The rate and pattern of ammonia excretion ofChanna gachua is described in relation to its body size. The food intake and rate of ammonia excretion was found to depend on the body size of the fish. The pattern of ammonia production is directly dependant on the food intake.

    • Distribution pattern of succinic dehydrogenase in the myocardia of some vertebrates

      Mathew M Oommen K M Alexander

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      A comparative study on the myocardial SDH levels in certain representative vertebrates revealed interesting variations. TheCybium myocardium exhibited relatively lesser SDH levels, whereasRana, despite its diving habits, had a higher level with significant variations between the two ventricular halves.Calotes, an active terrestrial form, showed the highest enzyme level among the reptiles. The SDH activity of the avian myocardia are quite high, withColumba having a greater level thanGallus. The myocardia of the actively flying forms (Columba andPteropus) exhibited higher enzyme levels in the right ventricle than the left ventricle.

    • Food preference studies of the larger bandicoot rat,Bandicota indica (Bechstein)

      Shakunthala Sridhara K Srihari

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      The food preferences of the South-Asian commensal rat,Bandicota indica were studied to evolve a suitable bait for control. Amongst cereals clear preference towards rice in its whole/divided form was evident. Amongst additives 7\2-10% groundnut oil enhanced bait intake significantly while 2% salt and sugar did not influence the rat’s diet choice. The results indicate whole/broken rice mixed with 7\2-10% groundnut oil as the most attractive bait for poisoningB. indica.

    • A sensitive period for the acquisition of food preferences in the Indian field mouseMus hooduga (Gray)

      Shakunthala Sridhara

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      The effect of exposure to particular cereals during infancy on adult food selection, and the sensitive period of acquisition of such food preferences, were studied in the Indian field mouse,Mus booduga Gray. Preliminary tests indicated an influence of early exposed diet on adult food selection. Further tests suggested that there is a sensitive period (4-6 days after birth) during which long lasting diet preferences are established in this wild mouse.

    • Structure and function of the truncus arteriosus of the Indian frogRana tigerina (Daud)

      Harish C Nigam

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      This paper presents new results on studies on the Indian frogRana tigerina; these include, the presence of a vertical septum in the truncus arteriosus, a cardiac skeleton of cartilaginous nature, a systemic valve in the right systemic arch, and the recording of some events in the cardiac cycle with the help of pressure and electrocardiogram parameters.

    • Effect of solar eclipse on the emergence of some freshwater cercariae

      R Madhavi

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      The effect of solar eclipse on the emergence of five species of freshwater cercariae from their snail hosts has been studied. Two cercariae showed visible changes from their normal emergence pattern from the snails during eclipse. It appears that changes in atmospheric light and temperature brought about by eclipse altered the behaviour of the snail and this has affected the emergence of cercariae.

    • Studies on the meiofauna of Sagar Island

      G Chandrasekhara Rao A Misra

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      Mean number of total meiofauna individuals in the intertidal estuarine sediments around the island ranged from 1/10 cm2 to 517/10 cm2. Nematodes and copepods were the dominant taxa comprising over 80% of the total fauna. Higher meiofaunal densities occurred over the lower shore. The fauna was concentrated mostly in top 4 cm of sediment, showing little submergence towards higher tidal levels. No diurnal and seasonal vertical migrations of meiofauna were observed. Two small seasonal peaks of meiofaunal abundance were noted. Total population values were highest in summer and lowest during monsoon. Nematodes reached their maximum in winter and copepods in summer. Variations in salinity appeared to be responsible for the seasonal pattern. The present meiofaunal densities are considerably lower than those recorded in other areas. The highly fluctuating hydrographical conditions and the fine sediment with silt-clay fraction, poor drainage, low oxygen content, etc., are considered responsible for the paucity of meiofauna in this area.

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