Responses induced by long-term toxic effects of heavy metals on fish tissues concerned with digestion, absorption, and excretion.

The present study relates to the bioassay as well as the responsiveness induced by long-term exposure to sublethal concentrations of soft acceptor heavy metals, lead (Pb, IV A) and cadmium (Cd, II B), in various fish tissues viz., stomach/intestinal bulb, intestine, liver, pancreas, and kidney of Mystus vittatus (Bloch) and Labeo rohita (Hamilton) belonging to 2 different trophic strata. Responses, however, have been recorded by histopathological and histochemical studies on the aforesaid tissues concerned mainly with digestion, absorption, and excretion. Histopathological observations depict the vacuolation, degranulation, exocytosis of the various cells including their nuclear damage. Erosion of the top plate of intestinal villi, enlargement of epithelial cells, shrinkage of glomeruli, destruction or disruption of the nephric tubular cells, etc. have also been registered. Histochemical investigations emphasize on the change in the intensity of staining reactions of biologically active macromolecules particularly amino acids of the protein component and glycogen among the carbohydrate component as well as acid, neutral and/or mixed mucopolysaccharides of the cells concerned. Toxic effects of the afore-mentioned heavy metals at the tissue level have been discussed.

Annual cyclical changes in the testicular activity of an Indian freshwater major carp, Labeo rohita (Hamilton).

Different male germ cells identified on the basis of histological and cytological characteristics in the testicular lobules of Labeo rohita have been grouped into spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa. The seasonal changes of the testis in L. rohita have been described according to its morphological peculiarities as well as to its variations in gonadal volumes, GSI values and frequency percentages of the different male germ cells occurring in the testicular lobules. Consequently, the entire testicular cycle in L. rohita may be categorised into 4 distinct phases viz., growth, maturation of pre-spawning, spawning, and resting or post-spawning phases.

Adenohypophysial cell types in an Indian freshwater major carp, Catla catla (Hamilton).

The different adenocytes in an Indian freshwater major carp, Catla catla (Hamilton) have been studied by employing various modern staining techniques. Altogether, 8 different cell types have been reported in the adenohypophysis of the aforesaid fish. Variations in the staining intensities of the cell types with the different techniques adopted have been detailed.

Sulfomucins and sialomucins in the mucus cells of the alimentary canal in an Indian freshwater major carp, Labeo rohita (Hamilton): a fluorescence microscopic study.

The localization of sulfomucins and sialomucins present in the various types of mucus cells--secretory (SMC) and mature non-secretory mucus cells (MMC) of the different regions of the alimentary canal in Labeo rohita (Ham.) has been studied by fluorescence microscopical techniques (viz., Ferric alum Coriphosphine--FAC, Coriphosphine thiazol yellow--CTY and Dische reaction--DR). High degree of fluorescence activity confirms the presence of relatively high amount of sulfomucins in the mucus cells of the oesophageal and buccopharyngeal regions when tested with FAC and CTY methods while moderate intensity of the same in the mucus cells of the two aforesaid regions indicates the localization of relatively lesser amount of sialomucins studied by DR technique. Moderate degree of fluorescence is also observed in the mucus cells (in both SMC and MMC) of the intestinal region with the techniques of FAC, CTY and DR whereas weak fluorescence of FAC, CTY and DR methods is marked in the mucus cells (in both SMC and MMC) of the rectal region due to the presence of low amount of sulfomucins and sialomucins.

Scanning electron microscopic study of the intestinal mucosa of an Indian freshwater adult major carp, Labeo rohita (Hamilton).

Fine anatomical structures of the different regions (viz., anterior, middle and posterior) of the intestinal mucosa in adult Labeo rohita (Hamilton) have been studied by using Scanning Electron Microscope (SEM). Surface mucosal modifications of the anterior and the middle of the intestine not only increase the luminal surface by 2-4 times but serve also the storage function of the ingested food due to the absence of stomach in the fish studied. Fine anatomical structures of the columnar epithelial and goblet cells of the mucosa have been studied in detail. The height and complexity of the microridges on the luminal end of each columnar cells in the various regions vary greatly probably due to the functional variations of the region concerned. Communication between the columnar cells and the sub-mucosal layer through the basement membrane is effected by circular orifices. A pear-shaped apical portion provided with prominent microridges of the goblet cell probably allows the mechanical stress to develop for the accumulation of secretory mucins.

Characterization and distribution of neutral and acidic mucins in the alimentary canal of an Indian freshwater major carp, Catla catla (Hamilton) by histochemical methods.

The distribution and chemical nature of acid and neutral mucins in the various regions of the alimentary canal of Catla catla (Ham.) have been studied. Both acid (sulfated and non-sulfated) and neutral mucins have been found to occur as a mosaic of complex substances in the different mucous cell types (secretory and non-secretory--both mature and immature) in the various regions of the alimentary canal (buccopharynx, oesophagus, intestine, and rectum). Acid mucin (both sulfated and non-sulfated) of the secretory and mature non-secretory mucous cells in the buccopharyngeal and oesophageal regions, however, predominates since these 2 regions are known to participate actively in food lubrication while the sulfated acid mucin keeps the internal mucosa moist. Mucous mother cells which originate from the multipotent progenitor cells contain exclusively neutral mucin in the form of neutral mucopolysaccharide granules. In the course of development these mucous mother cells are gradually pushed towards the periphery of the mucosa and transformed into mature and secretory mucous cells through an intermediate stage--the immature mucous cells. The latter cells during development synthesize intact acid mucopolysaccharide granules which ultimately fuse to produce a compact mass of mucin (both acid and neutral) in the mature and secretory mucous cells.

Detection and localization of alkaline and acid phosphatases in the digestive system of the adult Catla catla (Hamilton), an Indian freshwater major carp by histochemical methods.

The localization and distribution of alkaline phosphatase (ALPase) and acid phosphatase (ACPase) in the various regions of the alimentary canal viz., buccopharynx, oesophagus, intestine, rectum and hepatopancreas of adult Catla catla have been studied by employing various histochemical techniques. ALPase activity was recorded in the various regions of the alimentary canal in the present study although its intensity of localization and distribution varies greatly. The highest ALPase activity was detected in the columnar epithelial cells of the intestine including their brush border, sub-mucosal layer as well as in the basement membrane while intense activity of the same was observed in the epithelial cells (stratified and columnar) of the buccopharynx and oesophagus, hepatic and pancreatic acinar cells. The intense localization of ALPase was also found in the nuclei of the epithelial cells (stratified and columnar), sub-mucosal connective tissue nuclei, hepatic cell nuclei, and sub-mucosal polysaccharide granules of the intestine. The moderate ALPase activity was detected in the neuroepithelial cells of the taste buds in the buccopharynx, cytoplasm of the epithelial cells (stratified and columnar) and muscularis layers. The blood vessels of the intestine and rectum also furnished moderate ALPase activity. The weak ALPase activity was noticed in the brush border of the rectum and also in the basement membrane. Intense ACPase activity was recorded in the striated border of the intestinal villi, while moderate activity of the same was detected in the nuclei of the stratified and columnar epithelial cells of the various regions of the alimentary canal as well as in the hepatic and pancreatic acinar cells. Very weak ACPase activity was localized in the cytoplasm of the stratified epithelial cells of the buccopharynx and oesophagus.

Chronology of meiosis and spermiogenesis in a fresh-water teleost fish, Colisa fasciata (Bloch and Schneider).

The duration of individual stages of meiosis and spermiogenesis in Colisa fasciata (Bloch and Schneider) was calculated autoradiographically by following the kinetics of H3-TdR labelled spermatocytes in vivo. The leptotene lasts for less than 0.5 day, zygotene even for shorter period and pachytene for 1.86 +/- 0.13 days. The transition from diplotene to anaphase II requires about a day. The spermiogenesis is completed within 6.43 days. The labelled spermatozoa were detected at 9.68 d post injection, which is the approximate total duration of meiosis and spermiogenesis.

Comparative morphology, anatomy and histology of the alimentary canal of an Indian freshwater major carp, Labeo calbasu (Hamilton) during the different life-history stages in relation to food and feeding habits.

1. The early life-history stages of Labeo calcasu (Hamilton) viz., the fries, are zooplankton-feeders (carnivorous). The morphology, anatomy and histology of the alimentary canal during this stage is adapted accordingly. 2. With increase in age, size and body-length, the food and feeding habits of the fish undergo changes from the carnivorous to the herbivorous type (adult) through the omnivorous type (fingerlung). 3. The morphology, anatomy and histology of the alimentary canal gets modified accordingly in the fingerlings and adults.

Functional morpho-histology of the alimentary canal of an Indian frewhwater major carp, Labeo rohita (Hamilton) during it's different life-history stages.

1. The alimentary canal of the fry of L. rohita (Hamilton) is of the carnivorous type in nature and disposition with a low relative length of the gut (R. L. G.). 2. End-buds are present. The buccopharyngeal region has a simple epithelial surface. Mucous cells are small and few throughout the length of the alimentary canal. The presence of these structures in association with a zooplankton feeding habit indicate that the fries are primarily sightfeeders and carnivorous. 3. With increase in age and body-length, the food and feeding habits of the fish undergo changes and accordingly the fingerlings and adults become herbivorous. The value of the R. L. G. steadily increases and the alimentary canal gradually develops into the typically herbivorous type. 4. Tast buds by now become completely developed and have lamina propria, sustentacular cells, neuroepithelial cells, gustatory pores and gustatory canals. 5. Taste buds are abundant in the lip, buccopharynx and anterior oesophagus. The buccopharyngeal region is also provided with distinct villi. Mucous cells are abundant and large being present throughout the alimentary canal. 6. The frequency, length, breadth and distribution of the mucous cells and taste buds are significantly different in marked contrast with those of the fry thus indicating that the fingerlings and adults depend primarily on their gustatory organs for feeding. The fingerlings and adults therefore, are herbivorous and tast feeders.

On the origin, development and probable functions of taste bud in the lip and bucco-pharyngeal epithelia of an Indian freshwater major carp, Cirrhinus mrigala (Hamilton) in relation to food and feeding habits.

1. Various developmental stages of taste bud have been observed in the fry, fingerling and adult of Cirrhinus mrigala (Hamilton). 2. The fries are zooplankton-feeders (carnivorous) and sight-feeders. Therefore, functional taste buds are absent in the lip and bucco-pharyngeal epithelia. Only formative stages of taste bud are present. Some epithelial cells aggregate together to form this structure which has no function in gustation. Moreover, the fires have low R. L. G. valle (0.71;..1.20) due to the carnivorous diet. 3. In the fingerling, the stages of elongation, differentiation and maturation of taste bund develop from the formative stage present in the fries in order to adjust to changed food and feeding habit. The value of R. L. G; (1.21...3.10) also increases. 4. Fully formed taste buds along with the stage of differentiation are found in the adult stage. The adult fish becomes herbivorous and bottom-feeder. Consequently, the value of R.L.G. 3.11...12) becomes highest in this stage.

Morpho-histology of the intestine in a freshwater major carp, Cirrhinus mrigala (Hamilton) during the different life-history stages in relation to food and feeding habits.

The morpho-histology in relation to food and feeding habits of the intestine in the fry, fingerling and adult of Cirrhinus mrigala (Hamilton), a freshwater major carp, has been described. The intestine has been observed to be shortest in the fry (carnivorous) and longest in the adults (herbivorous) with intermediate values in the fingerlings (omnivorous). The mucosal folds of the intestine have also been observed to be adapted according to the nature of the dietary prevailing in the different life history stages. The food appears to have a marked influence on the morpho-histology of the villi and the number of mucous cells/unit area of the fry, fingerling and adult. The sub-mucosa, muscularis and tunica propria are characteristic in the fry, fingerling and adult.

A histochemical study of the mucous cells in the bucco-pharyngeal region of four Indian freshwater fishes in relation to their origin, development, occurrence and probable functions.

Observations on the origin, development and occurrence of mucous cells in the bucco-pharyngeal region of Labeo rohita (Ham.), Cirrhinus mrigala (Ham.), Catla catla (Ham.) and Clarias batrachus (Linn.) have been made histochemically, by PAS technique. The mucous cells have been found to develop from ordinary epithelial cells of the stratum Malpighii which is situated immediately above the basement membrane. The different stages in the development of mucous cells are: 1. Formation stage: Some of the epithelial cells get modified into mucous cells according to the need of the organ concerned. 2. Maturation stage: The spherical shaped mucous cells now become elongated and enlarged due to accumulation of mucin. They remain embedded in the stratified mucosa of the bucco-pharyngeal cavity. 3. Functional stage: In the course, these cells discharge their contents -- mucin into the bucco-pharyngeal cavity through an opening. 4. Degenerationstage: The mucous cells become empty soon after discharging their contents and eventually degenerate...