Chromosome numbers, genome sizes, cell volumes and evolution of snake-head fish (family Channidae)

Chromosome number, C-value and cell volume studies were carried out on three species of the genus Channa , viz., C. punctatus, C. striatus and C. gachua . The chromosome number, karyotypic structure and DNA content per cell along with cell volume are reported and described. A series of chromosomal rearrangements are established in three different karyotypes along with polyploidy. Both pericentric inversion and Robertsonian fusion played a major role in chromosome rearrangements. The nuclear DNA content of these three species is within 19-29% of the present-day placental mammals, and is thus lower than the median amount for fishes in general and teleosts in particular. Their lower DNA content suggests that the three species of the family Channidae are highly specialized, and this is supported by their known morphologic, reproductive, behavioural and ecological characteristics.
The evolutionary significance of these chromosomal rearrangements, their origin and their mode of establishment are discussed. A probable phylogenetic model based on karyotype, C-value and chromosomal rearrangements of the genus is presented.     

History of lectins: from hemagglutinins to biological recognition molecules

The occurrence in nature of erythrocyte-agglutinating proteins has been known since the turn of the 19th century. By the 1960s it became apparent that such proteins also agglutinate other types of cells, and that many of them are sugar-specific. These cell-agglutinating and sugar-specific proteins have been named lectins. Although shown to occur widely in plants and to some extent also in invertebrates, very few lectins had been isolated until the early 1970s, and they had attracted little attention. This attitude changed with the demonstration that lectins are extremely useful tools for the investigation of carbohydrates on cell surfaces, in particular of the changes that the latter undergo in malignancy, as well as for the isolation and characterization of glycoproteins. In subsequent years numerous lectins have been isolated from plants as well as from microorganisms and animals, and during the past two decades the structures of hundreds of them have been established. Concurrently, it was shown that lectins function as recognition molecules in cell-molecule and cell-cell interactions in a variety of biological systems. Here we present a brief account of 100-plus years of lectin research and show how these proteins have become the focus of intense interest for biologists and in particular for the glycobiologists among them.     

Studies on lectins. LVII. Immunofluorescence localization of lectins present in fish ovaries

The occurrence of endogeneous lectins in the ovaries of four fish species has been studied by indirect immunofluorescence staining with antibodies against individual lectins. Paraffin sections of the ovary of perch (Perca fluviatilis L.) were treated with an antibody against perch lectin. In cryostat sections of the tench (Tinca tinca L.) ovary, the L-rhamnose-specific lectin "I" was detected with a specific antibody. In cryostat sections of both roach (Rutilus rutilus L.) and rudd (Scardinius erythrophthalmus L.) ovaries, lectins were localized using a single antibody against roach lectin. The isolation of tench lectins is briefly described. In the fish species employed for this study, lectins are associated exclusively with the content and surrounding membrane of cortical vesicles situated within the cytoplasm of maturing oocytes. The positive reaction with lectin antibody was observed almost immediately after the formation of the first cortical vesicles in the peripheral cytoplasm of early previtellogenic oocytes. Their lectin content increases during the later stages when cortical granules fill the whole cytoplasm before moving towards the cell periphery, as the oocyte starts to accumulate yolk. The presence of lectins within cortical vesicles is significant also in view of the polysaccharide content of these structures. In the vitellogenic oocytes lectins seem to move towards the cell periphery and accumulate beneath the plasma membrane. Our observations are discussed in view of the present ideas on the intracellular function of lectins, and with respect to the role of cortical vesicles in fertilization and in post-fertilization modifications of the egg envelopes.     

Immunological identification of two female-specific proteins from the plasma of Indian freshwater murrel,Channa punctatus (Bloch)

Existence of a non-phosphorylated female-specific protein (FS II), in addition to phosphorylated vitellogenin (FS I), in the plasma of murrel by exogenous administration of estradiol-17beta is reported. Polyspecific rabbit antibodies were raised against estrogen-inducible murrel plasma proteins. This antiserum was absorbed with normal male serum in order to obtain female-specific antiserum (FSAS). Radial immunodiffusion studies suggested that both the proteins (FS I and FS II) were present in the plasma of E2-treated and normal vitellogenic females and in the ovarian homogenate from gravid females, but absent in normal male plasma. Autoradiographic experiments demonstrated that phosphorus moiety was attached with FS I only. Further, immunoelectrophoretic analysis and peptide maps supported the observation that FS I and FS II were discrete, unrelated female-specific proteins.     

Population ecology of the paddy field-dwelling fish Channa gachua (Günther) (Perciformes, Channidae) in Sri Lanka

A population of Channa gachua in a small irrigation canal that supplies rice fields was studied by monthly sampling over 2 years. The population density was positively correlated with the rainfall and varied from 0.34 to 0.95 individuals m⁻². The growth parameters of the von Bertalanffy growth equation determined on monthly size–frequency data were L_x = 179 mm total length and K =0.50. Overall male to female ratio was 0.82 and there were more females than males in the middle size classes. Spawning occurred throughout the year, but all evidence indicated enhanced breeding during major rainy periods of May to July and October to December. The length at first spawning was 102 mm, which is reached in about 20 months. Fecundity, which varied between 389 and 2130, was positively correlated with gonad weight, body weight and total length. Longevity and natural mortality were estimated as 6 years and l.27 yr⁻¹, respectively. However, 99% of the population appeared to live for only 3 years. The mean biomass, average annual production and turnover ratio of the population were 7.35 g m⁻², 12.06 g m⁻² and 1.64, respectively.     

Purification of vitellogenin from the plasma of Indian freshwater murrel, Channa punctatus (Bloch) by different methods: a comparative study

Plasma from estrogenized, [32P] NaH2PO4-injected murrel, Channa punctatus was collected in the presence of proteolytic inhibitors and subjected to different separation procedures singly or in combination, viz., gel filtration chromatography on Ultrogel AcA 34, ion-exchange chromatography on DEAE sephacel, or selective precipitation with dimethylformamide or with Mg2+: EDTA in order to isolate vitellogenin from other plasma proteins. The results show that chromatography on Ultrogel or DEAE sephacel yields intact vitellogenin whereas prior precipitation with DMF or with Mg2+: EDTA results in either co-precipitation of other plasma proteins or in the cleavage of phosvitin-like material from the native vitellogenin molecule.     

Structure and composition of teleost scales from snakehead Channa argus (Cantor) (Perciformes: Channidae)

The structure of teleost scales from snakehead Channa argus was investigated using thermogravimetric analysis (TG), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive analysis of X-rays (EDAX), Fourier transform infra-red spectroscopy (FTIR) and X-ray diffraction (XRD). Thermal treatment of fish scales indicates that the fibrillary plate is partially calcified. SEM shows two kinds of scale denticles, arranged along the circuli in the anterior field and the lateral fields, respectively. TEM indicates the stratum laxum with abundant fibrils, chromatophores and capillary blood vessels within the scale covering, and shows the fibrillary plate as an 'orthogonal plywood structure' of stratified lamellae, consisting of 80–100 nm diameter collagen fibres co-aligned in individual lamellae and alternated by c. 90° of the fibre alignment between adjacent lamellae. EDAX, FTIR and XRD show that the mineral phase of the scales is a carbonated hydroxyapatite with a Ca:P molar ratio of 1·85.     

Taxonomical notes on selected freshwater fish species described from northern and central Vietnam(Cypriniformes:Balitoridae,Cobitidae,Cyprinidae,Nemacheilidae; Perciformes:Channidae,Osphronemidae;Synbranchiformes:Mastacembelidae)

Selected,little known taxa of northern and central Vietnamese freshwater fish species are reviewed.Nomenclatural acts are taken:Hemibarbus lehoai is placed in synonymy of H.maculatus,Paracobitis hagiangensis in synonymy of Schistura caudofurca.A neotype of Micronemacheilus bacmeensis is assigned.The name Channa hanamensis is treated as a nomen nudum.Two labeonine species described from China are nomenclaturally affected:Garra findolabium is transferred to Vinagarra and its specific epithet is treated as a noun in apposition;the specific epithet of Sinigarra napoense is corrected to napoensis.     

Carcass characteristics of marketable size striped murrel,Channa striatus (Bloch, 1793)

The carcass and commercial yield traits of Channa striatus were evaluated. Experimental fish were 8‐month‐old snakehead murrels (Channa striatus) weighing 500–700 gm, reared in earthen ponds and cultivated intensively at a rate of 10 000 fingerlings/ha. The fish were given formulated feed for a period of 1 year. Morphometric parameters were measured along with carcass, filleting, and offal traits. The murrel head yield (28.7%) as well as scales and skin yield (11.92%) were recorded. Dressed murrel (evisceration yield) was 89.59% of the live weight. Dressed percentage (minus the head, skin and viscera) was 50.72%. Average meat‐to‐bone filleting ratio was 3.43 of marketable size murrels. Insignificant accumulations of fat deposits on the lining of the abdominal cavity and coating the bowels were noted.     

Related mannose-specific lectins from different species of the family Amaryllidaceae

Bulbs from three species of the plant family Amaryllidaceae ( Narcissus pseudonurcissus L., Leucojum aestivum L. and Leucojum vernum L.) were found to contain mannose-specific lectins. These lectins were serologically identical to a previously reported Amaryllidaceae lectin from Galanthus nivalis L. bulbs, but had a different molecular structure. The lectins described in this paper are dimeric proteins composed of subunits of 13 kDa, which are not held together by disulphide bridges. In hapten-inhibition assays Amaryllidaceae lectins exhibited exclusive specificity towards mannose. Furthermore, they all had a high specific agglutination activity with trypsin-treated rabbit erythrocytes, whereas human red blood cells were not agglutinated.