ABSTRACT
Aims: To ascertain the gastrointestinal nematode burden on the channids, Parachanna obscura and Parachanna africana (Steindachner, 1879) (Family: Channidae) in the down reaches of Orogodo River at Evboesi and Ekwuoma-Abavo, southern Nigeria and its relationship to the levels of organic pollution. Study Design: A total of 220 channid fish were collected from two stations of the river experiencing different degree of organic pollution and dissected for gastrointestinal nematode parasites Place and Duration of Study: The study lasted for a period of six months (Jan to Jun 2010) with collections of fishes done monthly at two sampling stations of Orogodo River in southern Nigeria. Methodology: A total of 220 channid fishes were examined. Their stomachs and intestines were cut open and the contents were emptied into Petri dishes containing water and were examined for nematode parasites. These were quickly stained with Giemsa stain and viewed under a light microscope. Results: A total of 100 (45.5%) were infected with gastrointestinal nematode parasites. The prevalence of infection reveals that Parachanna obscura recorded 62.5% while Parachanna africana had 66.7% in fishes collected from station 1 and 20.1% and 28.6% respectively from fishes collected at station 2. The nematode parasites recovered were Cucullamus sp., Camallanus sp. and Procamallanus laevionchus. The overall parasitic burden reveals that the prevalence infection was statistically significant (p< 0.05) in the species examined. The distribution of infrapopulations of the parasites varied significantly with size class and weight of the fish peaking in most cases in larger size classes. The chemical parameters of the river water at station 1 showed the water to be stressed with high BOD and nutrients levels when compared with station 2. This may explain the high parasitic burden recorded in the channids at station 1. Conclusion: The intensity of the parasites in the host fish agree with previous hypotheses suggesting that environmental pollution does affect parasite population.
ABSTRACT
Investigation into some aspects of the biology and ecology of the freshwater crab, Sudanonautes floweri (De Man, 1901) in River Ogbomwen, Edo State, southern, Nigeria was carried out between February and July 2006. The study revealed that the crab species were widespread and abundant in the river. Abundance in terms of number and biomass was more during the wet season with at a peak in the months of June and July. The crab grew allometrically attaining a maximum total length and weight of 11.5 cm and 65 g respectively. The condition factor ranged from 8.60-9.45. These values did not vary with size and sex of the crab but showed seasonal variations. Females of Sudanonautes floweri were more abundant although not significantly different from the expected 1:1 ratio. There were some sexually matured females with stages III gonad development. Fecundity estimate ranged from 400 to 650 eggs. The gonadosomatic index varied between 14.97 and 24.11%. Feeding habits varied slightly with size with larger sized crabs feeding on more and varied food particles. Generally, Sudanonautes floweri fed predominantly on detritus, crustaceans, fish, algae, filaments, diatoms and sand grains.
Algunos aspectos de la biología y ecología del cangrejo de agua dulce Sudanonautes floweri (De Man, 1901) fueron estudiados en el río Ogbomwen, estado de Edo, al sur de Nigeria entre febrero y julio de 2006. Este estudio reveló que este cangrejo se encuentra en forma abundante y ampliamente distribuido en este río. Abundancia en términos de número y biomasa fue mayor en la estación lluviosa con un pico para los meses de junio y julio. El cangrejo tuvo un crecimiento alométrico alcanzando una longitud y peso máximos de 11,5 cm y 65 g respectivamente. El factor condicional varió de 8,6-9,45. Estos valores no variaron ni con el tamaño o el sexo del cangrejo pero mostraron variaciones estacionales. Las hembras de Sudanonautes floweri fueron más abundantes pero esto no fue significativo con respecto a la razón esperada de 1:1. Se encontraron algunas hembras sexualmente maduras con estado III de desarrollo gonadal. El estimado de fecundidad osciló entre 400 hasta 650 huevos. El índice gonadosomático varió entre 14,97 y 24,11%. Hábitos alimentarios variaron poco con el tamaño en donde cangrejos de mayor tamaño se alimentaron en forma más variada. En general Sudanonautes floweri se alimentaron de detritos, crustáceos, pescado, algas, filamentos, diatomeas y granos de arena.
ABSTRACT
Preliminary investigation into some aspects of the biology of the palaemonid prawn, Macrobrachium dux (Lenz, 1910) in River Orogodo at Abavo, southern Nigeria was carried out between March and August 1995. The freshwater prawns were collected with properly baited cage traps and scooping with hand basket. The study revealed that the prawn species were widespread and abundant in the river. Abundance in terms of number and biomass was more during the wet season with a peak in August. Both adults and juveniles showed a progressive increase from late dry season to midrainy season (August). The malefemale ratio was 1:1.2. The fluctuation in the number and percentage of ovigerous females indicated that the prawn spawned during the midrainy season (JuneAugust). Ovigerous females ranged from 4.6 to 7.5 cm and egg size varied from 1.5 to 1.7 mm. The prawn attained a maximum total length and weight of 7.5 cm and 7.0 g respectively. Its growth pattern was allometric. The mean monthly condition factor (k) ranged from 1.43 to 2.37 and generally showed a monthly fluctuation with a peak in July.
Una investigación preliminar de algunos aspectos de la biología del langostino Macrobrachium dux (Lenz, 1910) fue realizada en el río Orogota en Abavo, sur de Nigeria entre marzo y agosto de 1995. Los langostinos de agua dulce fueron recolectados con trampas y removidos con una canasta de mano. Este estudio reveló que las especies de langostinos se encontraban distribuídas ampliamente y en abundancia en este río. La abundancia en términos de número y biomasa fue mayor en la estación lluviosa con un pico en agosto. Tanto adultos como juveniles mostraron un crecimiento progresivo desde el final de la estación seca hasta la mitad de la estación luuviosa (agosto). La relación machoshembras fue de 1:1,2. La fluctuación entre el número y porcentaje de hembras ovígeras que los langostinos depositan sus huevos durante la mitad de la estación lluviosa. Hembras ovígeras oscilaron entre 4,6 y 7,5 cm y el tamaño de los huevos varió entre 1,5 y 1,7 cm. Los langostinos alcanzaron longitudes y pesos totales de 7,5 cm y 7 g respectivamente. Su patrón de crecimiento fue alométrico. El promedio mensual del factor de condición osciló entre 1,43 y 2,37 y mostró fluctuación mensual con el pico en julio.