The architecture of the gill surface of the catfish, Heteropneutes fossilis (Bloch): SEM study.

A scanning electron microscopical examination of the gills of H. fossilis is described. The surface architecture of gill filaments and secondary gill lamellae showed the presence of various features such as indentations, micropits and crevices. The possible functions of these morphological adaptations are discussed in relation to physiology of the gill.     

Seasonal changes in the corpuscles of Stannius and the gonads of the catfish, Heteropneustes fossilis (Bloch).

The seasonal changes in the corpuscles of Stannius (CS) and the gonads of the catfish, Heteropneustes fossilis were studied. The annual sex cycle of the fish has been divided into 4 phases on the basis of the variations in the gonosomatic index and histocytological features displayed by the testes and ovaries. There is a rise in the percentage of aldehyde fuchsin (AF)-positive cells in the CS and an increase in the nuclear diameter, at the beginning of preparatory period (February). In the prespawning period (May--June) the AF-positive cells undergo degranulation. A slight regranulation and rise in the percentage of AF-positive cells occurs during early spawing period (July). During the postspawning phase (September--January) the corpuscles remain predominated by AF-negative cells and show histolytical changes; the nuclear indices are reduced. In view of the concomitant changes occurring in the CS and the gonads the possibility of some direct or indirect relationship between the two has been discussed, although it is difficult to ascertain whether the changes in the corpuscles are cause or consequence of the gonadal cycle.     

Effect of salicylate and adrenocorticotropin on the hepatic and serum cholesterol in catfish, Heteropneustes fossilis (Bloch).

A single injection of salicylate or salicylate plus ACTH was able to lower the hepatic cholesterol content within one hour after the treatment. However, their daily injection for eight days caused significant rise in the hepatic cholesterol. ACTH alone could not significantly alter the liver cholesterol content after similar treatment. A single injection of salicylate produced hypocholesterolemia within one and three hours after the treatment. ACTH or salicylate plus ACTH also brought about 50 per cent reduction in serum cholesterol level from its initial control value within one hour. Similar treatments, however, raised the serum cholesterol after three hours. The rise in the serum cholesterol level was about twofold in animals five hours after salicylate plus ACTH treatment. Daily administration of salicylate, ACTH or salicylate plus ACTH for eight days caused, however, hypocholesterolemia.     

Pituitary cytology of radiothyroidectomised teleost Heteropneustes fossilis (Bloch.).

The pituitary of Heteropneustes fossilis is divisible into rostral (RPD) and proximal (PPD) pars distalis, and pars intermedia (PI). Neurohypophysis extensively ramifies in the PI. The RPD is formed of acidophilic prolactin cells and lead hematoxylin (H. Pb) positive ACTH cells. The latter is arranged around the neurohypophysial extensions. The PPD is comprised of thyrotrophs (TSH) and gonadotrophs which are stainable with PAS, AF, and aniline blue. Acidophilic somatotrophs (STH) and chromophobes are scattered throughout the PPD. In the pars intermedia PAS positive and H. Pb positive cells are present. The latter is believed to secrete MSH whereas the function of the former is yet to be confirmed. In the partly and completely thyroidectomised H. fossilis the TSH cells exhibited marked hypertrophy. They are located in the middle of the PPD flanked by the gonadotrophs on either side. Hypertrophy of the ACTH cells were also evident. But the other cell types did not show any marked changes as compared to the controls.     

Effect of ACTH and bilateral gonadectomy on the adrenocortical tissue of an air-breathing fish -- Heteropneustes fossilis (Bloch).

The mammalian ACTH (20 I.U.) injected in Heteropneustes fossilis (Bloch) caused hyperplasia of the adrenocortical tissue. The interrenal as well as chrome cells became vacuolated. The interrenal nuclear size increased by 15% as an average than the control fishes. The glycogen granules were found to be absent from the interrenal cells. The effect of bilateral gonadectomy in both sexes has been marked in the gradual decrease of the interrenal nuclear diameter which 12 weeks after the operation, recorded nearly 25% reduction in size. The glycogen content was reduced considerably. Removal of gonads during maturation period bringing inhibition of hyperplasia of the gland at the time of spawning possibly indicates action of gonadal steroids on the physiological alterations of the interrenal cells.     

Responses of seminal vesicle and testicular beta-glucuronidase and beta-N-acetylglucosaminidase to testosterone and some metabolites in Heteropneustes fossilis (Bloch).

Intraperitoneal administration of testosterone for 20 days produced differential effects on beta-glucuronidase and beta-N-acetylglucosaminidase (beta-Glc) activity in seminal vesicle (SV) and testis of the catfish Heteropneustes fossilis in preparatory phase (March). The lower dosages of 0.25 and 0.5 microg/g body weight (BW) of the steroid did not alter enzyme activity, and the higher dosages (1.0 and 2.0 microg/g BW) inhibited it significantly. Under in vitro conditions, addition of ascorbate and fructose (0.5-100 mM) to the incubation medium influenced enzyme activity differentially. At concentrations 0.5 and 1.0 mM, both fructose and ascorbate were ineffective except for the inhibition of testicular beta-Glc activity in the 1.0 mM ascorbate group. At higher concentrations (10, 50, and 100 mM), ascorbate inhibited enzyme activity in a concentration-dependent manner. At 10 mM concentration of fructose, only testicular beta-Glc activity was inhibited, but at higher concentrations (50 and 100 mM), activities of both enzymes decreased uniformly in a concentration-dependent manner. The addition of glucose had no significant effect on the enzyme activity at any of the concentrations tested. The results suggest that the inhibitory effect of testosterone on enzyme activity may be mediated through androgen-dependent metabolites, such as fructose and ascorbate.     

Seasonal changes in the hypothalamo-hypophyseal-ovarian system in the catfish,Heteropneustes fossilis (Bloch)*

The annual reproductive cycle of the catfish, H. fossilis (Bloch) is divided into the preparatory period (February-April), the prespawning period (May-June), the spawning period (July-August) and the postspawning period (September-January). During the early postspawning period (September-November), the hypothalamo-hypophyseal-ovarian system shows a gradual regression. In January, the hypothalamic nuclei, the pars magnocellularis (PMC), the pars parvocellularis (PPC) of the nucleus preopticus (NPO), and the nucleus lateralis tuberis (NLT) show renewed activity, as shown by a significant increase in their nuclear diameters and an accumulation of neurosecretory material (NSM) in their cell bodies. The hypophysis and the ovary remain quiescent. During the preparatory period, all the hypothalamic neurons studied indicate decreased activity but simultaneously show an accumulation of NSM in their cell bodies. The number of granulated basophils in the proximal pars distalis (PPD) of the hypophysis remains low but ovarian weights increase, presumably due to the multiplication of oogonia. In the prespawning period, there is a marked accumulation of NSM in the cell bodies of the hypothalamic neurons and at the same time the number of granulated basophils in the PPD of the hypophysis dramatically increases with concomitant increase in vitellogenic activity in the ovary. During the spawning period, the hypothalamic neurons continue to store NSM in their cell bodies and simultaneously there is a tremendous increase in the number of granulated basophils in the PPD of the hypophysis and the ovary has a large proportion of yolky primary oocytes. Spawning is associated with a significant degranulation of the granulated basophils in the PPD of the hypophysis. The significance of the results is discussed in relation to the environmental and hormonal regulation of seasonal ovarian activity.     

Lipids in the skin of a cat-fish Heteropneustes fossilis (Bloch) (Heteropneustidae,Pisces)

Summary Localization and characterization of different lipids in the cellular constituents of the skin of Heteropneustes fossilis has been made using several histochemical techniques.High contents of cholesterol, its esters and phospholipids have been correlated with the metabolically active state of the basal cells undergoing cell proliferation and differentiation.The polygonal cells in the outermost layer of the epidermis, though rich in phospholipid contain small amounts of cholesterol and its esters. This has been correlated with the metabolically less active state of these cells.Neutral lipids and phospholipids in the polygonal cells of the outermost layer may contribute to the contents of surface slime and act as an efficient barrier for the penetration of water through the skin.The deposits of neutral lipids in the subcutis may provide energy during the period of fasting, act as a barrier for water diffusion through the skin and serve as shock absorbing pads protecting the fish from mechanical injury.Supported by a post doctoral fellowship sponsored by the Council of Scientific and Industrial Research, Government of IndiaSupported by a research scholarship sponsored by Banaras Hindu University     

Effect of environmental factors on the activity of thyroid gland in an air breathing siluroid fish Heteropneustes fossilis Bloch.

1. Studies on cyclic activity of thyroid in relation to environmental factors were made in an air breathing siluroid fish, H. fossilis. 2. The activity of thyroid gland showed parallelism with water temperature and photoperiod but from the regression analysis it was evident that the effect of photoperiod on thyroid activity is more pronounced than the effect of water temperature. 3. The maximum thyroid activity coincides well with the breeding phase of this animal.