Purificação e caracterização parcial de duas N-acetil-ß-hexosaminidases do Equinoderma marinho Echinometra lucunter

Two b-N-acetylhexosaminidases (F11 e F15) were purified from Echinometra lucunter gonads extracts. The purified enzymes were obtained using ammonium sulfate fractionation, followed by gel filtration chromatographies (Sephacryl S-200, Sephadex G-75 and Sephacryl S-200). The F11 fraction was purified 192.47 -fold with a 28.5% yield, and F15 fraction 85.41 -fold with a 32.3% yield. The molecular weights of the fractions were 116 kDa for F11 and 42 kDa for F15 using SDS-PAGE. In Sephacryl S-200, F15 was 84 kDa, indicating that it is a dimeric protein. When p-nitrophenyl-β-D-glycosaminide was used as substrate, we determined an apparent Km of 0.257 mM and Vmax of 0.704 for F11 and for F15 the Km was 0.235 mM and Vmax of 0.9 mM of product liberated by hour. Both enzymes have optimum pH and temperature respectively at 5.0 and 45 °C. The enzymes showed inhibition by silver nitrate, while the glucuronic acid was a potent activator. The high inhibition of F15 by N-etylmaleimide indicates that sulphydril groups are involved in the catalysis of synthetic substrate

Ecologia parasitária de isópodos e biologia reprodutiva em tibiro, Oligoplites spp (Osteichthyes: carangidae) das águas costeiras de Natal, Rio Grande do Norte

Oligoplites palometa (Cuvier) and Oligoplites saurus (Bloch & Schneider) (Osteichthyes: Carangidae) are coastal pelagic fish species. The objective of this study was to investigate the effect of parasitism by isopods and the reproductive biology of the leather jack, Oligoplites spp. A total of 113 individuals of Oligoplites spp (35 of O. saurus and 78 of O. palometa) were captured during the period between January, 2005 and July, 2007 from the coastal waters of Natal, RN. The morphometric and meristic characters were registered; macroscopic analyses were done to collect the isopod parasites and the gonads were observed to verify the reproductive aspects. The crustacean isopod parasite, Cymothoa spinipalpa (Isopoda: Cymothidae) was encountered on the tongue in the oral cavity in both fish hosts. The parasitic indices of C. spinipalpa showed high values of prevalance of 51,4% for O. saurus and 64,1% for O. palometa. The host presented significant correlations between body mass and body length of O. palometa and the number of parasites. Body lengths of female C. spinipalpa were small due to the limited space available in the oral cavity of the host. There was a significant difference in the sex ratio of O. palometa, males outnumbered the females. The isopod parasites showed specificity to the oral cavity of hosts. Macroscopic analyses of gonads showed four stages of gonadal development for both sex of O. palometa: immature, maturing, mature and spent

Biologia reprodutiva da Tainha, Mugil curema valenciennes, 1836 (osteichthyes: mugilidade) nas águas costeiras do Rio Grande do Norte

The marine fish white mullet, Mugil curema Valenciennes, 1836 (Osteichthyes: Mugilidae) exhibits a wide geographical distribution, being common in the Brazilian coast and is an important component of the artisanal fisheries. The objective of this study was to investigate the reproductive biology of M. curema in the coastal waters of Rio Grande do Norte. Fish samples were captured on a monthly basis during August, 2008 to July, 2009. The fish specimens were numbered, weighed, measured, dissected and their gonads were removed, weighed, their sex and gonadal development were identified. The length-weight relationship was determined for males and females. The sex ratio, the size at first gonadal maturation and gonadosomatic index (GSI) were calculated and ovarian development was investigated using macroscopic and histological techniques. The fecundity, spawning type and the reproductive period of the species were determined. A total of 366 specimens (186 males and 180 females) were captured. The sex ratio was 1:1 and the females were heavier than males. The estimated values of the angular coefficient for both sexes suggest that the species has isometric growth. The size at which 50% of the population began the process of maturation was 25.9 cm of total length for grouped sex. The macroscopic characteristics of the ovaries showed four stages of development: immature, maturing, mature and spent. However, the microscopic characteristics of the ovaries showed five stages of development: immature, early maturing, late maturing, mature and spent. The development of oocytes indicated five phases: Chromatin-nucleolus (phase I), initial perinucleolar (phase II), final perinuclear (phase II), formation of vitelline vesicle or yolk (phase III), vitellogenic (phase IV) and complete vitellogenesis (phase V). The species has a prolonged spawning period, with two peaks coinciding with the rainy season.