Differences in the food of the young and the adult Indian mackerel, Rastrelliger kanagurta (Cuv.)

The problem of the food of fishes with its varied bearings on their shoaling habits and migrations has engaged the attention of fishery biologists since the beginning of the present century. The mackerel is an important food fish in both hemispheres. Several contributions have been made to our knowledge of the food of the Indian mackerel, Rastrelliger kanagurta, which contributes to one of the largest fisheries of India. All these observations, except those of Chacko, which are from the Gulf of Manaar, are confined to the west coast of India. According to these workers, mackerel is a noted plankton feeder, securing its food by filtration. Chidambaram, while observing the adult mackerel as plankton feeder, suggested the carnivorous habits of the young mackerel. Later, in a detailed account on the food of this fish, Bhimachar and George observe that "the food of the young mackerel does not radically differ from that of the adult". Pradhan has arrived at a similar conclusion regarding the food of mackerel; but one will not fail to note from his observations that young mackerel less than 89 mm. in total length are not represented in his material

The development of glandiceps (Enteropneusta; spengelidae)

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RATE OF WATER PROPULSION IN MYTILUS CALIFORNIANUS AS A FUNCTION OF LATITUDE

Volume: 104Start Page: 171End Page: 18

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Not AvailableThe problem of the food of fishes with its varied bearings on their shoaling habits and migrations has engaged the attention of fishery biologists since the beginning of the present century. The mackerel is an important food fish in both hemispheres. Several contributions have been made to our knowledge of the food of the Indian mackerel, Rastrelliger kanagurta, which contributes to one of the largest fisheries of India. All these observations, except those of Chacko, which are from the Gulf of Manaar, are confined to the west coast of India. According to these workers, mackerel is a noted plankton feeder, securing its food by filtration. Chidambaram, while observing the adult mackerel as plankton feeder, suggested the carnivorous habits of the young mackerel. Later, in a detailed account on the food of this fish, Bhimachar and George observe that "the food of the young mackerel does not radically differ from that of the adult". Pradhan has arrived at a similar conclusion regarding the food of mackerel; but one will not fail to note from his observations that young mackerel less than 89 mm. in total length are not represented in his material.Not Availabl

Some aspects of the mechanism of thermal acclimation in the earthworm Lampito mauritii

Inorganic ions (Ca, Mg, Na, K, Cl, SO4) and free amino acids of the body fluids of the normal, cold and warm acclimated worms (laboratory as well as seasonal populations) are estimated. Calcium increased and chloride and sodium decreased on both cold and warm acclimation in relation to normal. But magnesium and sulphate and free amino acids increased on warm acclimation whereas potassium increased and magnesium decreased on cold acclimation. Changes in different ions in the same direction are observed in the seasonal populations. Attention is drawn to the adaptive significance of these changes in the different ions during thermal acclimation. Changes in the glycogen, RNA, protein and non-protein nitrogen, and water content in the tissues of normal and acclimated worms are studied. Glycogen increased on warm and cold acclimation, whereas RNA content, protein nitrogen and dry weight of the cold worms increased over normal. No change is observed in non-protein nitrogen on thermal acclimation. The role of these substances and the significance of the changes observed, in the operation of homeostatic mechanism compensating to temperature changes in the metabolic rate of the worms, are also discussed. Changes in the pattern of neurosecretory activity are followed with thermal acclimation and it is shown that the activity of the neurosecretory cells increased on cold and warm acclimation, but the positions of these cells, which are active, are different from normal worms in warm acclimated worms. Studies on the effect of the body fluids of acclimated worms on the tissues of normal and acclimated worms showed that the body fluids of cold acclimated worms increased the respiration of the tissues of normal and warm acclimated worms and vice-versa

Hormone-​like action of the sterol fraction from the nerve tissue of cold- and warm-​acclimated earthworm, Lampito mauritii

Earthworms, L. mauritii, were acclimated to cold (20°)​, warm (35°)​, or normal (28°) temps. for >15 days. An ext. was obtained from the nonsaponifiable sterol fraction of nervous tissue of the worms. The alc. ext. from the cold-​acclimated worms increased the respiration of tissue from normal worms, whereas the ext. from warm-​acclimated worms decreased the tissue respiration. The results indicated the presence of one or more hormone-​like factors in the nervous tissue of the worms

Utilization of dissolved calcium by a pelecypod

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Rate of activity as a function of intertidal height within populations of some littoral molluscs

The physiological reality and profound ecological significance of the phenomenon of regulation of rate functions towards a constant, in response to maintained temperature differences, within the species in poikilotherms, has been widely recognized in recent times. Much attention has been directed in this connexion to a study of populations spatially separated by a wide range of latitude or temporally separated by the annual cycle of seasons. Indications of the existence of similar intraspecific differences between high and low members of populations of intertidal invertebrates are reported in the present communication

Effectiveness of temporal pattern in the input to a ganglion: inhibition in the cardiac ganglion of spiny lobsters

(1) The single inhibitor axon of one side, going to the cardiac ganglion of Panulirus in a preparation with the central nervous system removed, was stimulated at a constant mean frequency but with different temporal fine structure. In particular, inhibitory trains with uniform intervals are compared with trains of alternately short and long intervals ("paired pulse"). Different ratios of short to long interval were used and, besides pairs, groups of up to 8 shocks. (2) Sixteen different measures of the inhibitory effect upon various aspects of the electroneurogram of the heart beat are compared. Some are more sensitive, others are more consistent. (3) Pattern sensitivity is found, that is the heart beat slows to different extents for different temporal structures. Trains of uniform intervals were generally more effective than any other pattern. Bursts of 7 or 8 are less effective than shorter bursts with the same minimum and mean interval. (4) The same burst has a different effect according to the phase of the heart cycle at which it arrives; the later the arrival the greater the effect. At the optimal phase and impulse interval, the minimum number of impulses for a just noticeable inhibitory effect (5-10%) is about 4. (5) In some preparations aging was associated with a reversal from inhibition to acceleration and such changes were not necessarily in parallel for different stimulus patterns. (6) On present evidence it cannot be said that the pattern sensitivity is explained by the effect of conditioning shock-test shock interval on the synaptic response to the test shock. (7) Evidence does not yet permit evaluation of the possible role of pattern sensitivity under normal conditions. The significance at presetn is the finding that in a nearly ideal preparation for testing, a postsynaptic neuron can "read", i.e., respond differently to the same mean frequency according to temporal fine structure