Volume 95, Issue 1
February 1986, pages 1-116
pp 1-6 February 1986
Reproductive cycle of the crabOcypoda macrocera has been studied employing the gonad index method. Breeding period in this crab is found to be a prolonged one extending from March–September with small intermittent peaks and falls. Salinity is found to have a close relationship with the breeding cycle as lower salinities during October–January coincided with the absence of reproductive activity. Male crabs have not shown any clear picture in their gonad index in relation to breeding period and male gametes are found round the year.
pp 7-21 February 1986
In teak plantations at Nilambur, Kerala,Hyblaea puera Cramer (Lepidoptera, Hyblaeidae) caused one or two waves of epidemic defoliations between late April and July, followed in some years by isolated, lighter defoliation between August and November. The insect was absent at other periods, although with a 3-week life cycle it can theoretically pass through several generations per year. The temporal and spatial distribution of infestation and certain behavioural characteristics of populations gave evidence of short-range migration of newly emerged moths. In a model proposed for population dynamics ofH. puera, no diapause occurs and a residual, non-migratory population exists in natural forests during the nonepidemic period. With the onset of general flushing of teak in February–March, the population starts building up and when a critical density is reached, migratory behaviour is triggered. Migration facilitates exploitation of new food sources and escape from larval parasites. Generally, after one or two epidemics, the population declines due to leaf maturity, natural enemies and density-dependent food depletion. This cycle of ups and downs, with attendant transition between migratory and non-migratory phases is repeated every year. If some steps of the proposed model are confirmed by further study, simple methods could be devised to manage this serious pest of teak.
pp 23-44 February 1986
The morphology, anatomy and histology of the organs concerned with capture and digestion of food of the canine catfish-eelPlotosus canius Hamilton, have been described. It shows a primitive organisation of digestive organs in the presence of only one type of secretory cell in the gastric glands and diffused pancreatic cells, embedded within the intrahepatic cells. The study indicates the species to be a carnivore with characters of both primitive, as well as, developed carnivorous nature. While discussing, the structural peculiarities observed, have been correlated with type of food generally encountered in the gut of the species.
pp 45-50 February 1986
Interscapular brown adipose tissue was studied in pregnant and lactating females and compared with virgin females in inbred Wistar rats, using the histomorphology and quantitation of cell numbers. In pregnant females an increase in the interscapular brown adipose tissue weight, total fat content and total fat cell numbers associated with a decrease in adipocyte diameter was observed when compared with virgin females. The total lipid content and total fat cell number in the interscapular brown adipose tissue of lactating females showed a decrease when compared to the pregnant females. This suggests that pregnancy and lactation are accompanied by changes in the status of interscapular brown adipose tissue which may be related to the changes in energy metabolism in these physiological states.
pp 51-57 February 1986
Juveniles ofChanna striatus were fed twice a week with hormone supplemented diet at concentrations of 0, 1, 2·5, or 10 mg/kg fish and the hormone effects on growth and food utilization were observed for a period of 75 days. Neither ethylestrenol nor the tested doses of the steroid appear to significantly change feeding rate. Administration of 5 mg of ethylestrenol/kg fish not only enhanced growth but also conversion efficiency.
pp 59-66 February 1986
In bright light-adapted (25 Iux) retina ofChanna punctatus, the pigment in the epithelial cell is fully migrated into the epithelial cell protuberances. In dim light-adapted retimae (6, 3 and 1 lux), the pigment concentration gradually decreases into the tips of the epithelial cell protuberances and its concentration gradually increases in the origin of the epithelial cell protuberances. In dark-adapted retina, the pigment is fully expanded into the epithelial cell. The pigment concentration is more in the vitread region. The cones remain contracted in light-adapted retinae of various light intensities. The rods are visible only in dim light-adapted (6, 3 and 1 lux) retinae and invisible in dark (0 lux). The mechanism of pigment migration in this fish is different from those of other fish.
pp 67-76 February 1986
Oxygen consumption and carbon dioxide production increased with increase in random (spontaneous) swimming activity in mullet,Rhinomugil corsula in high oxygen (normoxia), but the oxygen consumption in low oxygen (hypoxia) was negatively correlated with swimming activity in tests at both 30 and 35°C. The RQ of mullet under hypoxia always remained over unity and increased with increase in activity, clearly indicating intense utilization of anaerobic energy. The RQ under normoxia remained near unity irrespective of random swimming activity change. The AQ of normoxic and hypoxic mullet showed opposing trends, the quotient increasing with decreasing activity in the former and increasing with activity increase in the latter. The AQ change suggests increased protein utilization in quieter fish when adequate ambient oxygen is available, but the hypoxic mullet utilizes more protein the more active it is. The latter change in AQ is consonant with the change in hypoxic RQ and it is likely that increased anaerobic energy utilization demanded by the increased activity is accompanied by increased protein breakdown and ammonia release, thereby helping in acid-base balance and ionic (Na+) regulation. Results obtained at 30 and 35°C are almost identical. Within the small range temperature does not seem to cause a marked metabolic difference in mullet.
pp 77-87 February 1986
Fifty three freshwater habitats located in and around Bangalore (South India) were surveyed for studying the distribution and abundance of prawns. The survey indicated that, the habitats were rich in prawn fauna, harbouring one species of Palaemonid,Macrobrachium lanchesteri (de Man) and 3 species of Atyids,Caridina nilotica (Roux) varbengalensis, Caridina rajadhari (Bouvier) andCaridina weberi varsumatrensis (de Man).Macrobrachium lanchesteri andCaridina nilotica were more widely distributed thanCaridina rajadhari andCaridina weberi. The results throw light on the pattern of distribution and species composition of these prawns in relation to the nature of the habitats.
pp 89-96 February 1986
Results of experiments conducted in T-maze to probe the functional role of conspecific odours indicated that whereas the male Indian gerbil,Tatera indica indica invariably prefers odours (from their body, that of the sebum exudation of scent marking gland, urine and faecal matter) of strange males, the females with and devoid of the scent marking gland show slight preference for male odours. However, all the categories ofTatera indica placed their preference for their own odours at the lowest. This behaviour suggests that the role of scent marking to label the habitat for its own use or to signal ‘home’ to the marking animal may not be the sole function of scent marking in this species. It is quite possible that in the desert grassland, scent marking is being used for maintaining a minimum distance between two animals or pairs, as exhibited by the diversity in the occurrence of the scent gland in the field (pair-tolerant) and urban (gregarious social organisation) populations ofTatera indica. This type of spatial distribution, maintained by scent marking behaviour, may be important to withstand the low carrying capacity of the aridland which suffers from almost a perpetual paucity of food.
pp 97-102 February 1986
The effect of certain abiotic factors viz. temperature relative humidity and soil moisture has been revealed on the activity ofAdoretus epipleuralis Arrow. This beetle was caught with the help of Pilani type light trap operated daily for 2 years (1976, 1977) from dusk to dawn at Pilani (Pilani is on the North-eastern side of Jhunjhunu District of Shekhawati Region in semi-arid zone of Rajasthan, India. Its geographical position is 28°20′ N latitude and 75°35′ E longitude and 330 mase.) To ascertain in mathematical terms the extent of relationship between the prevailing weather conditions and the light trap catches ofAdoretus epipleuralis, regression analysis, partial regression analysis, multiple linear regression analysis and β-coefficient analysis have been exercised.
pp 103-107 February 1986
In order to determine the optimum protein requirement in the feeds forCatla catla (Hamilton) andLabeo rohita (Hamilton), isocaloric pelleted feeds containing 20%, 30%, 40% and 45% protein were formulated using casein as the main source of protein. The best growth of catla and rohu was observed when fed on feeds containing 30% and 40% protein. The growth was poorer when fed on the diet containing 20% protein and poorest when fed on the feed containing 45% protein. The results revealed that the protein requirement of both catla and rohu was around 30%. It also indicated that more than the optimum level of protein in feeds has an adverse effect on the growth of the species investigated.
pp 109-116 February 1986
Pollination by two species of flower thrips in six Solanaceous plants (four perennials and two seasonal) were studied. The results highlight the role of thrips in both self and cross pollination of these flowers. The findings also suggest that in view of the stigmatic surface in all the flowers being at a higher level than the anthers, there is more entomophily. Data relating to the population dynamics of thrips as well as the pollen load of thrips are also included.