Annual cyclical changes in the testicular activity of a freshwater teleost, Barbus luteus (Heckel) from Shatt-Al-Arab, Iraq

The testes of Barbus luteus are a pair of elongated structures composed of an anastomosing system of seminiferous lobules. Six spermatogenetic stages of germ cells have been described in the gonad. The endocrine factor lies in the interstitial cells. Spermiation occurs during the months of May, June and July. Fertilization appears to be external. Un-expelled spermatozoa undergo pycnotic degeneration. The testes show a regular annual cycle which has been described in five arbitrary stages.     

Occurrence of parasites of the freshwater mugilid fish Liza abu (Heckel) from Basrah, southern Iraq

In monthly samples of Liza abu collected November 1981–October 1982 from Mehaijeran Creek, a western branch of Shatt–Al–Arab river south of Basrah, fishes were infected with the third larval stage of the nematode Contracaecum sp., the acanthocephalan Neoechinorhynchus agilis and the gill crustacean Ergasilus mosulensis.
Generally, the changes in the percentage prevalence coincided with the changes in the mean intensity of infection. There were no significant differences between the infection of male and female fishes in the cases of the monthly variations of infection with Contracaecum sp. and of infection with both Contracaecum sp. and E. mosulensis , according to fish length, but in other cases more female fishes were infected than males.
Infection with Contracaecum sp. decreased gradually in the larger fishes. In the case of both N. agilis and E. mosulensis , the infection at first increased with increase in fish length but decreased in larger fishes.
Infection with Contracaecum sp. occurred only during May–August and disappeared during September. The peak for N. agilis was in April, and it disappeared during summer. Infection with E. mosulensis disappeared during winter months.     

Morphological changes of the nucleolus during oogenesis in oviparous teleost fish, Barbus barbus (L.)

In fishes, like in amphibians, it is well established that variations in rRNA activity occur during oogenesis. Contrary to amphibians, however, little is known about the ultrastructural changes of the nucleolus during fish oogenesis. Evolution of the nucleolus has been followed during oogenesis in the teleost fish Barbus barbus (L.) using light and transmission electron microscopies. We show that the behaviour of the nucleolus during B. barbus oogenesis resembles that reported in amphibians but also presents several peculiarities. The most striking feature is the marked vacuolization of nucleoli occurs at the beginning of the growth during previtellogenesis. The results obtained by means of the in situ terminal deoxynucleotidyl transferase-immunogold method for detecting DNA seem further to indicate that the chromatin cap becomes integrated into developing nucleoli during previtellogenesis and then segregate at the periphery of nucleoli at the end of glycoproteinic vitellogenesis. Our study also shows that the nucleoli of germ cells, like that of follicle cells, are devoid of fibrillar centre but comprise a fibrillar and a granular component whatever the oogenetic stage. Ultrastructural detection of DNA and nucleolar proteins (AgNOR proteins, fibrillarin, and pp135) supports further the view that the Barbus nucleolus is a bipartite structure.     

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.     

Functional morphology of the gonoduct of the viviparous teleost Poeciliopsis gracilis (Heckel, 1848) (Poeciliidae)

Female teleosts do not develop Müllerian ducts; consequently, the ovary of teleosts contains two zones: germinal and gonoduct. The gonoduct lacks germinal cells, but has relevant functions in the reproductive process. We describe the functional morphology of the gonoduct in the viviparous teleost Poeciliopsis gracilis during nongestation and gestation stages. This study tests the hypothesis that the gonoduct functions as a barrier between the germinal zone and the exterior. By providing information about morphology and function of the gonoduct we show that this part of the ovary has an essential role in the reproduction of teleosts. The ovaries were processed by histological technique and stained with hematoxylin‐eosin (H‐E), Masson's trichrome, toluidine blue and periodic acid‐Schiff (PAS). The gonoduct is divided into three regions: cephalic, middle, and caudal. In the cephalic and middle regions there are mucosal folds that extend into the gonoductal lumen, forming structures similar to a cervix. The caudal region has two portions: the anterior contains a dorsal invagination and exocrine glands among columnar cells; the posterior has a ventral flexion and stratified epithelium with apical secretory cells. The morphology of this epithelium indicates two functions: (a) secretory by the apical columnar cells, and (b) protection through the stratification. Another peculiarity of the caudal region is that both ducts, reproductive and digestive, converge in a common cavity at their caudal ends, forming a cloacal region. The histology of the gonoduct indicates relevant functions including: (1) the control of the luminal diameter by the muscle and the presence of mucosal folds, like a cervix; (2) the relationship with the spermatozoa during insemination and storing them in mucosal folds; (3) the support of immunological processes; (4) secretory activities; (5) forming the duct during birth; and (6) possibly, acts as a barrier against parasite infestations.     

Barbus xanthos,a new barbel from the Southern Aegean basin (Teleostei: Cyprinidae)

Barbus xanthos, a new species, is described from the Eşen, Dalaman, Tersakan and Büyük Menderes rivers in south-western Anatolia. It differs from other Barbus species in the adjacent basins by having 53–60 lateral line scales, a weakly ossified last unbranched dorsal-fin ray (about 33–50%), numerous small irregular-shaped black or dark-brown spots smaller than scales, often forming large, black or dark-brown blotches on back and flank in juveniles and adults, and a straight or slightly convex posterior dorsal-fin margin. B. xanthos differs from its most closely related congener, B. pergamonensis, by nine nucleotide substitution sites in the mitochondrial DNA cytochrome oxidase I barcode region.     

Circadian changes in prolactin cell activity in the pituitary of the teleost Poecilia latipinna in freshwater

Summary Quantitative morphometric studies with the electron microscope were made on the prolactin cells of wild freshwater sailfin mollies taken in Florida in August at four different times of day. The results indicate a circadian rhythm in the prolactin cell, the period of highest synthetic activity being from midday to evening, as indicated by the condition of nucleus, Golgi apparatus and rough endoplasmic reticulum, and by the incidence of granule release profiles. No circadian changes were detected in the ACTH cells.Several distinct sites of prolactin granule release were recognised. However, there was no conclusive evidence of granule release by any mechanism other than classical exocytosis.We thank Mr. W. Thomson for technical assistance and Ann Grier for help in collecting the fish. T.F.C. Batten is in receipt of an S.R.C. Research Studentship.     

Pituitary cytology of the freshwater teleost Anabas testudineus (Bloch)

In the pituitary of A. testudineus the rostral pars distalis (RPD), proximal pars distalis (PPD) and pars intermedia (PI) are arranged in a rostro-caudal axis. The rostral neurohypophysis (NH) extends dorsal to the pars distalis, while the caudal part vertically penetrates into the PI and ramifies in its component. The RPD mainly consists of erythrosinophils and PgH-positive cells which are comparable to the lactotropes and corticotropes mentioned in the literature. In the nonbreeding season, acidophils are the predominant cells of the PPD and are largely confined to its dorsal aspect. The two types of cyanophils present in the PPD could not be differentiated with the various techniques used in this study. However, those cyanophils which increase in number and are active during the spawning season may be the gonadotropes, while those which are cytologically inactive may be the thyrotropes. The pars intermedia consists of PAS+ and PhH+ cells. Trichrome and tetrachrome staining techniques revealed the presence of acidophils, cyanophils and amphiphils in the PI.     

Toxic effects of mercury on testicular activity in the freshwater teleost, Clarias batrachus (L.)

Catfish ( Clarias batrachus L.) were exposed to selected sublethal concentrations of mercuric chloride (HgCl₂; 0.05 mg l⁻¹), methylmercuric chloride (CH₃HgCl; 0.04 mg l⁻¹) and emisan 6 (an organic mercurial fungicide; 0.5 mg l ⁻¹) for intervals of 45, 90 and 180 days from February to July (preparatory to spawning phase of the annual reproductive cycle). The gonadosomatic index showed a significant decrease after 90- and 180-day exposure to the mercurials. Histologically, the seminiferous tubules were smaller in size and contained mostly spermatids in comparison to the control fish in which they were greatly distended and full of spermatozoa. The Leydig cells showed pycnotic changes in Hg-treated fish after 90 and 180 days. In the Hg-treated testes, total lipid content and ³²P uptake decreased significantly after 90 and 180 days. Levels of phospholipids and free cholesterol registered a significant reduction during all the durations. Esterified cholesterol level showed a significant decrease only in the 90-day HgCl₂ and CH₃HgCl groups, and in all 180-day Hg groups, while the level of free fatty acid decreased significantly only in the 180-day Hg groups. The observations suggest that impairment of testicular lipid metabolism by Hg is one of the possible factors that led to the inhibition of steroidogenesis and spermatogenesis.     

Continuous gametogenesis in the neotropical freshwater teleost, Bryconops affinis (Pisces:Characidae)

The gametogenesis of Bryconops affinis was studied by light, transmission and scanning electron microscopy. The spermatogenesis is semi-cystic and spermatids are released into the lumen of seminiferous tubules, where spermiogenesis is completed. Spermatozoa have an ovoid head, a rudimentary middle piece with a small number of mitochondria and long flagellum (primitive spermatozoa). The Sertoli and Leydig cells show secretory activity during spermatogenesis. By the end of this phenomenon, the Sertoli cells phagocytize the residual spermatozoa, while the Leydig cells show involuted characteristics. With regard to the oogenesis process, the oocyte development was divided into four stages based on the cytological characteristics of the oocyte and its surrounding layers. Ultrastructural analysis revealed that the zona pellucida is formed during the previtellogenic stage. Specializations associated to the outer layer of the zona pellucida may be related to the egg's adherence to the substrata.     

Suppression of osteoclastic activities by calcitonin in the scales of goldfish (freshwater teleost) and nibbler fish (seawater teleost)

Using a tartrate-resistant acid phosphatase (TRACP) activity, the effects of calcitonin (CT) and estradiol-17beta(E(2)) on osteoclastic activities in cultured scales of goldfish (freshwater fish) and nibbler fish (seawater fish) were examined. In mature male and female goldfish, scales were collected and incubated in Earle's minimun essential medium (MEM) supplemented with either CT (100 ng/ml) or E(2) (100 ng/ml). In both sexes, CT suppressed TRACP activities in the scales, whereas E(2) increased them. When CT (100 ng/ml) and E(2) (100 ng/ml) were added simultaneously to MEM, TRACP activities in the scales did not change as compared with the control. Similar results were obtained with the scales of female nibbler fish. In goldfish, furthermore, the activation of scale TRACP by E(2) was suppressed, depending on CT concentrations (100 pg/ml to 1 microg/ml). In fish reproduction, this function of CT may be useful to protect scales from excess degradation of calcium at vitellogenesis.     

Length–weight and length–length relationships of four species (Barbus lacerta Heckel, 1843), Oxynoemacheilus angorae (Steindachner, 1897), Squalius lepidus (Heckel, 1843) and Pseudorasbora parva (Temminck & Schlegel, 1846) from the Sirwan River (western Iran)

The study describes the length–weight and length–length relationships for three cyprinid species, namely Barbus lacerta, Squalius lepidus and Pseudorasbora parva, and a balitorid species, Oxynoemacheilus angorae from the Sirwan River (located in Kurdistan and Kermanshah provinces, Iran. This study presents the first reference on LWR for most of the species in their distribution range.     

The yolk nucleus in the freshwater teleost Garra gotyla gotyla (Gray)

The structure and functional significance of the yolk nucleus in Garra are described. The study shows that the yolk nucleus appears in the cytoplasm of the early perinucleolus stage of the oocyte. It is present as a deeply stained structure enclosed in a vesicle. It disappears in the yolk vesicle stage and vitellogenesis begins soon afterwards. This probably indicates that it plays a role in the initiation of vitellogenesis. When yolk formation starts, the yolk nucleus disappears; this also suggests that it is of functional significance in yolk synthesis.     

The cytoarchitecture of the torus semicircularis in the teleost Barbus meridionalis

The torus semicircularis of Barbus meridionalis is composed of two nuclei, the nucleus centralis and nucleus lateralis. Its cytoarchitecture was studied in sections stained by Nissl and Golgi-Colonnier techniques. In the nucleus lateralis two portions were identified: the ‘pars lateralis’ and the ‘pars medialis.’ Cytoarchitecturally, both portions are identical. They exhibit a layered structure in which there is an alternation of cell-poor and cell-rich laminae designated as: (1) the subependymal layer; (2) the layer of small cells; (3) the fibrillar layer; and (4) the layer of disperse cells. The subependymal layer consists of fine fibers and some small rounded-ovoid cells whose dendritic prolongations course horizontally or ventrally. The second layer has small, densely-packed cells with rounded-ovoid and triangular somata and a main dendritic trunk that courses ventrally. The third layer contains dendritic fields of the cells of layer two and of cells from layer four. The fourth layer is composed of fusiform neurons with two dendritic trunks of equal thickness, rounded-ovoid neurons with one or two main dendritic trunks and multipolar triangular stellate neurons with equal dendritic trunks. The nucleus centralis comprises a fibrillar cortex with a structure identical to that of the subependymal layer. There is also a cellular region with the same cell types as those found in the nucleus lateralis. These two nuclei thus compose the torus semicircularis of the barbel. They exhibit the same cytological characteristics and both are differentiated by their cytoarchitectural and functional orders.     

Annual changes in the brain neurosecretory profile of the Indian freshwater Leech,Poecilobdella viridis (Blanchard) in relation to reproduction

Annual changes in the brain neurosecretory profile of Poecilobdella viridis in relation to reproductive activity have been investigated. The changes in A cell neurosecretory activities were found to be in strong correlative correspondence with the reproductive programme. Heavy accumulation of neurosecretory material was observed in A cells perikarya during the reproductive period i.e. from March to June, 1975, with enlarged nuclei and during reproductive quiescence i.e. from August, 1974 to January 1975, the neurosecretory activity was low.     

Copper influenced changes of lipid metabolism in the tissues of freshwater teleost Labeo rohita (Hamilton).

Modulations in the lipid metabolism in the gill, liver, muscle and brain of freshwater teleost Labeo rohita exposed to 1, 2 and 3 days to lethal (1.2 mg/l) and 1, 15 and 30 days to sublethal (0.24 mg/l) concentrations of copper were studied. The total lipids decreased and there was an increase in the free fatty acids, glycerol and lipase activity in the organs studied at lethal concentration of copper. The degree in these shifts increased over time of exposure (1 less than 2 less than 3 days). In sublethal concentration, the levels of total lipids, free fatty acids, glycerol and lipase activity increased in all the four organs and the shifts followed two different trends during the exposure periods, 1 less than 15 less than 30 days in total lipids and 1 greater than 15 greater than 30 days in the other parameters. Among the organs, in both concentration media the changes in the lipid metabolism were in the order liver greater than gill greater than muscle greater than brain.