Laboratory studies on the development, survival and life tables of Culex fatigans and Anopheles stephensi

Observations on the duration of pre/post embryonic stages, survival and longevity of laboratory populations ofCulex fatigans andAnopheles stephensi were made in order to understand the factors controlling outbursts of these mosquito populations in original habitats. Regardless of the nature of culture medium and food,C. fatigans took a longer period (19 days) to complete the development of pre-embryonic stages thanA. stephensi (17 days). The highest survival rate ofC. fatigans was noticed in pupal stage (96%), while it was advanced to IV instar stage (95%) inA. stephensi. The survivorship curves ofC. fatigans andA. stephensi exhibited negatively skewed rectangles, indicating that the mortality is confined exclusively to aged individaals

Influence of body weight/age on the food intake, growth and conversion efficiency of Gambusia affinis

On a restricted food supply of Tubifex tubifex (2h/day) the fish consumed only 69.5 mg dry food/g live fish/day and grew only to 25.6 mg live body weight by the 30th day of it's age, while those fed ad libitum consumed 94.7 mg/g/day and attained a body weight of 125.9 mg live weight by the 30th day. Conversion efficiency (K1) averaged to 8.3% in the former and 14.1% in the latter series, throughout the 30 day experimental period. Feeding rate of the test series fed individually and at ad libitum, decreased from 780 mg dry food/g dry fish/day for a fish weighing 4 mg dry weight to 180 mg/g/ day for one weighing 41 mg, exhibiting a log-log relationship to the body weight (Y = 2.20140-0.5639 X). Growth rate also decreased as a log-log function with increasing body weight (Y = 1.2309-0.4384 X). © 1977 Dr. W. Junk b.v. Publishers

Environmental restraints on the food intake, growth and conversion efficiency of Gambusia affinis: influence of Living space

Food intake, growth and conversion efficiency of juvenile Gambusia affinis are considerably influenced by the volume of water available per fish. On an 'ad libitum' diet of Tubifex tubifex worms, juveniles reared in intermediate amounts of "living space" of 500 and 800 ml water per 4 individuals, exhibited maximum growth and conversion efficiency. Both below and beyond these volumes of water, the above parameters decreased indicating the inhibitory influence of 'limited' as well as 'abundant' living space on the food conversion of the fish. © 1977 Indian Academy of Sciences

Comparative studies on the food intake, growth and food conversion of two larvivorous fishes

Food intake, growth and conversion efficiency of two larvivorous fishes have been studied by supplying different proportions of first instar Culex fatigans larvae and Tubifex tubifex worms. The worms inhibit the preferential feeding on mosquito larvae by Gambusia affinis and Poecilia reticulata. The reduction is more marked in G. affinis than in P. reticulata. Growth and conversion efficiency of P. reticulata surpassed the values observed for G. affinis indicating that the mosquito larvae are better utilised by P. reticulata than by G. affinis. © 1979, Indian Academy of Sciences. All rights reserved

Effects of Meal Size on Growth and Conversion Efficiency of the Freshwater Catfish Clarias batrachus (Linn.)

Effects of different daily meal size on food intake, growth and gross conversion efficiency (K,: YO) of juvenile Clarias batracbus are described. An amount of Tubifex worms equivalent to 14.2% live body weight of fish/day represents the maximum amount which a 2.75 k 0.42g C. batracbus can consume under laboratory conditions. 24,71 and 140mg/g fish/day re resent the geometrically derived maintenance, optimum and maximum feeding rates of the juvenile fis!.The SDA increased by three times from optimum to maximum levels of feeding, thus suggesting that the energy cost of converting food into body substance is more at higher levels of feeding

Preliminary studies on the conversion of Tubifex tubifex as food by elvers of Anguilla nebulosa (Gray and Hardwicke)

Elvers of Anguilla nebulosa were reared at 23°C in confined waters and their food intake, growth and conversion efficiency (K1:%) were studied. Elvers weighing 278.33±14.35 mg were fed on an ad libitum diet of the oligochaete worm Tubifex tubifex for 60 days. On an average, the test individuals consumed 99.55±19.81 mg food/elver/day amounting to 35.76% of the initial biomass; during the corresponding period the elvers exhibited a growth rate of 5.03±2.42 mg gain in weight/elver/day which is equivalent to 5.06% of the consumed food. Thus the ‘housekeeping’ of these elvers may be regarded as established. In 50 days, the food required amounts to 0.358±50 = 17.90 times the initially stocked biomass. That is, 1 kg of initially stocked elvers may need 17.90 kg of T. tubifex to produce 0.912 kg of elver meat. A poor conversion ratio of 20 : 1 may be one reason for the slow growth of the elvers

Studies on the neurosecretion of thoracic ganglion in relation to reproduction of femaleMacrobrachium lanchesteri (de Man)

The changes in the histology of thoracic ganglion in females ofMacro-brachium lanchesteri, prior to spawning and post parturial moult, have been described. Based on the differences in size, cell inclusions and differential staining with CHP, four distinct types of neurosecretory cells have been identified in the ganglion. The activity of these cells has been correlated with the ovarian condition of the prawn and evidence for the elaboration of a gonad-stimulating hormone (GSH), by the ganglion has been derived. The, probable regulation of ovarian maturation during a normal ovarian cycle and that during the ovigerous condition ofM. lanchesteri have been illustrated

Histology of the male reproductive system of the prawn Macrobrachium lanchesteri (Crustacea: Decapoda)

The testis of the 'freshwater prawn Macrobrachium Ianchesteri consists of numerous branching lobules, bound by thin limiting membranes. There is very little inter-lobular space with indistinct blood sinuses and the lobules are filled with germ cells in different stages of development. The different regions of the vas deferens of the prawn viz., anterior vas deferens (AVD), mid vas deferens (MVD) and posterior vas deferens (PVO) , indicate structural variations reflecting the specific role of each region, in spenn transport, spermatophore formation and ejaculation. The nature of the glandular epithelium and presence of secretory material in the lumen suggest that packaging of sperms into a spermatophore is initiated in the AVO itself. The epithelial cells of the inner margin of the AVD and MVD are highly columnar. fonning a 'typhlosole'-like region. The histology of the MVD differs from that of the A VD in the presence of prominent circular and longitudinal muscle layers. Presence of copious secretory material in the MVD indicates further packaging of the sperms. Extensive muscle layers and reduced secretory activity are characteristic of the PVO. The male hormone-producing tissue. the androgenic gland, is situated mesially in the curvature of the ampulla, the distal end of the PVD. The histology of the gland confirms its secretory role

Yolk and copper utilisation during embryogenesis of the freshwater prawnCaridina nilotica

Yolk and copper utilisation during embryogenesis of the fresh-water prawnCaridina nilotica var.bengalensis (De Man) have been described. The egg number/brood increased with increase in length as well as volume (L8) of the mother animal. The water content increased from 61·3% (I stage) to 76·4% (III stage) as development proceeded. Fat appeared to be the major source of energy for embryonic metabolism. During development 28·4µg of dry substance were utilised for embryonic metabolism. The pattern of copper absorption followed the trend of salt absorption

Regulation of ovigericity in a fresh water prawn macrobrachium lanchesteri (de Man)

Summary The intermoult duration of ovigerous Macrobrachium lanchesteri, between the pre-spawning and the post-parturial moults, is significantly long, twice that of the adult non-ovigerous females. This intermoult duration is independent of mating, fertilization of eggs, presence/absence of eggs held in the brood as well as eyestalk principles. The possible role of specific endogenous factor(s) probably elaborated by the ovary, in the maintenance of the long intermoult duration as well as ovigericity of this prawn, is projected