visits to the landing site of a small urban fishery (APREBAN) in Rio de Janeiro city were conducted and 816 specimens of Rhizoprionodon lalandii were analysed. The sample, mostly females, was composed of two cohorts: young-of-the-year were abundant in spring and summer and adults predominated in autumn and winter. Gravid females were most abundant from April to June, whereas postpartum females composed most of the catch in August to September. Adult males were present all year although were more abundant between February and July. No neonates were captured during the study and most embryos collected measured slightly below the reported total length (L T ) at time of birth (L 0 ) for the species, suggesting that parturition may occur slightly outside the main fishing grounds or that neonates were not captured in commercial gillnets set at this time of the year. The mean L T at maturity (L T50 ) for males was 578 mm and females matured between 620 and 660 mm, although a precise estimate of L T50 for females could not be determined. The total length (L T ) and total mass (M T ) relationship ðM T ¼ 7E À L 3Á2597 T Þ was calculated for both sexes and showed no significant differences. The mean condition factor increased steadily from February to July followed by a steep decrease in values relative to females in August and September, suggesting a pupping season. The present study area can be classified as a coastal juvenile habitat and a probable mating ground for R. lalandii.
Normal lung morphogenesis is dependent on chloride-driven fluid transport. The molecular identity of essential fetal lung chloride channel(s) has not been elucidated. CLC-2 is a chloride channel, which is expressed on the apical surface of the developing respiratory epithelium. CLC-2-like pH-dependent chloride secretion exists in fetal airway cells. We used a 14-day fetal rat lung submersion culture model to examine the role of CLC-2 in lung development. In this model, the excised fetal lung continues to grow, secrete fluid, and become progressively cystic in morphology (26). We inhibited CLC-2 expression in these explants, using antisense oligonucleotides, and found that lung cyst morphology was disrupted. In addition, transepithelial voltage (V(t)) of lung explants transfected with antisense CLC-2 was inhibited with V(t) = -1.5 +/- 0.2 mV (means + SE) compared with -3.7 +/- 0.3 mV (means + SE) for mock-transfected controls and -3.3 +/- 0.3 mV (means + SE) for nonsense oligodeoxynucleotide-transfected controls. This suggests that CLC-2 is important for fetal lung fluid production and that it may play a role in normal lung morphogenesis.
Sampling of the demersal ichthyofauna of Guanabara Bay was conducted bimonthly for 2 years at 10 stations distributed along a hydrobiological gradient. A total of 16,081 Tetraodontiformes specimens were collected, representing 10 species distributed among Ostraciidae, Monacanthidae, Tetraodontidae and Diodontidae. Tetraodontiformes appear to be well adapted to hydrological variations and inhospitable conditions prompted by intense eutrophication. However, abiotic factors traditionally considered important in estuarine community structure play a secondary role in the distribution of Tetraodontiformes. The type of sediment appears to be the most important physical factor but acts only as an indicator of ecological domain. The low explanatory power of physicochemical variables, in addition to the relative stability of the bay's ichthyofauna, suggests an influence of biological parameters. The species exhibited wide variation in their use of Guanabara Bay and utilized it as a resting, feeding and growing area. Among the species captured, Stephanolepis hispidus, Lagocephalus laevigatus, Sphoeroides greeleyi, Sphoeroides testudineus, Sphoeroides tyleri, Chilomycterus reticulatus and Chilomycterus spinosus were categorized as marine estuarine opportunists, and Aluterus heudelotii and Aluterus schoepfii were classified as marine stragglers. Acanthostracion sp. could not be categorized. The boom of C. spinosus indicates an ecological misbalance and must be carefully investigated.
Guanabara Bay is one of the most ecologically, economically and socially important tropical estuaries in the southwestern Atlantic. Fortnightly samples of the demersal ichthyofauna were obtained from July 2005 to June 2007, by bottom trawling from six stations determined according to the water quality. The net was 7 m long with a 14 m wide mouth and a mesh size of 18 mm. The tows were made at a speed of about 1.5 knots. The most abundant species, occurring in all 48 surveys, was Chilomycterus s. spinosus (14,837 specimens; 61.8 ind/h; 3.85 kg/h). Although commonly captured in Brazilian bays, this species has never been found in such high abundance and wide L T ranges (2.635.6 cm). The fish were concentrated in the middle portion of the estuary, which shows their high tolerance to eutrophic conditions, as well as to natural variations in temperature and salinity. In the last quarter of the study, the relative abundance levels rose to 228 ind/h, mostly small specimens of about 8.0 cm L T and 40 g M T , comprising 45% of the total catch. Such a successful recruitment could cause a large shift in species composition in the demersal community, with unpredictable ecological consequences. The population fluctuations of this species coincided with the rainfall pattern; the estuary is used as a nursery area until the fish reach the size at first maturity.
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