Cytotoxic and genotoxic responses of the RTgill-W1 fish cells in combination with the yeast oestrogen screen to determine the sediment quality of Lagos lagoon, Nigeria.

Economic advancements in developing countries have seen an increase in urbanisation and industrialisation with a rise in the levels of discharge of effluents and municipal waste into aquatic ecosystems. Unfortunately, aquatic environmental regulations in these countries are often rudimentary and the development of environmental monitoring programmes will help identify ecological risks. As an example, the current study assesses the pollution status of 11 sampling sites in Lagos lagoon, Nigeria. The organic solvent sediment extracts were assessed for cytotoxicity and genotoxicity in rainbow trout gill-W1 cells. The induction of oestrogenic activities using the yeast oestrogen screen was also determined. The sediments were analysed for polycyclic aromatic hydrocarbons (PAHs) and other contaminants (polychlorinated biphenyls, organochlorine and organophosphate pesticides). Only sediments from three sites were cytotoxic at both 25 and 12.5mg eQsed/ml using the Alamar Blue cell viability assay. The alkaline Comet assay showed that all sites caused significant DNA damage at 7 mg eQsed/ml; the extent of the damage was site specific. The measure of oxidative damage to DNA via the formamidopyrimidine DNA-glycosylase-modified Comet assay revealed similar results. Toxicity to yeast cells was observed in extracts from six sites; of the remaining sites, only two exhibited oestrogenic activity. There was no strong consistent relationship between sediment PAH concentrations and the cell toxicity endpoints. The dynamic nature of Lagos lagoon with its tides and freshwater inputs are suggested as factors that make it difficult to link the sources of pollution observed at each site with PAH levels and toxic endpoints. The study has demonstrated that the Comet assay is a sensitive endpoint to identify sediments that possess genotoxic contaminants, and this in vitro bioassay has the potential to be incorporated into an environmental monitoring framework for Lagos lagoon.

Effects of dietary calcium on growth and oviposition of the African land snail Limicolaria flammea (Pulmonata: Achatinidae).

In an attempt to elucidate the role of calcium in the life of the edible Achatinid snail, Limicolaria flammea (Miller) I investigated short and long term effects of calcium added to the food. The short term experiments lasted for 18, 30 and 32 weeks respectively, while the long term experiment to determine life time utilization of calcium carbonate lasted for 15 months. In the short term experiments, hatchlings were divided into densities of one, ten and 50 snails. In the 10 snail group, there was a positive correlation between calcium provision, body weight (t test, p < 0.01; r = 0.96, p < 0.0001) and shell length (t test, p < 0.01; r = 0.96, p < 0.00001). There was also a positive correlation between increase in shell length and availability of calcium in the 1 snail group (t test, p< 0.01; r = 0.99, p < 0.00001). In the 50-snail group, the correlation was positive for shell length of the snails (t test, p < 0.05; r = 0.99, p < 0.0001) and body weight (t-test, p < 0.05; r = 99, p < 0.00001). Mortality was very high in the snails deprived of calcium and they did not produce eggs. In the long term experiment, there were three feeding peaks in L. flammea. In the first feeding peak, amount of food and calcium ingested by the snails increased in the first three months of life. The second feeding peak occurred at six months of age, while the last occurred at 10 months of age. The amount of calcium ingested during the second peak decreased gradually in the 4th and 5th month. The amount of calcium ingested was lowest during the 3rd feeding peak. The period of highest weight gained by the snails was between the 1st and 6th month and then dropped at between six and 12 months of age which corresponds to the period of egg production. There were also three peaks of egg production; the first was between six and eight months (535 eggs), the second at between 10 and 11 months (350 eggs) and the third at 13 to 14 months (310 eggs) respectively.

Effects of dietary calcium on growth and oviposition of the African land snail Limicolaria flammea (Pulmonata: Achatinidae)

In an attempt to elucidate the role of calcium in the life of the edible Achatinid snail, Limicolaria flammea (Miller) I investigated short and long term effects of calcium added to the food. The short term experiments lasted for 18, 30 and 32 weeks respectively, while the long term experiment to determine life time utilization of calcium carbonate lasted for 15 months. In the short term experiments, hatchlings were divided into densities of one, ten and 50 snails. In the 10 snail group, there was a positive correlation between calcium provision, body weight (t test, p < 0.01; r = 0.96, p < 0.0001) and shell length (t test, p < 0.01; r = 0.96, p < 0.00001). There was also a positive correlation between increase in shell length and availability of calcium in the 1 snail group (t test, p< 0.01; r = 0.99, p < 0.00001). In the 50-snail group, the correlation was positive for shell length of the snails (t test, p < 0.05; r = 0.99, p < 0.0001) and body weight (t-test, p < 0.05; r = 99, p < 0.00001). Mortality was very high in the snails deprived of calcium and they did not produce eggs. In the long term experiment, there were three feeding peaks in L. flammea. In the first feeding peak, amount of food and calcium ingested by the snails increased in the first three months of life. The second feeding peak occurred at six months of age, while the last occurred at 10 months of age. The amount of calcium ingested during the second peak decreased gradually in the 4th and 5th month. The amount of calcium ingested was lowest during the 3rd feeding peak. The period of highest weight gained by the snails was between the 1st and 6th month and then dropped at between six and 12 months of age which corresponds to the period of egg production. There were also three peaks of egg production; the first was between six and eight months (535 eggs), the second at between 10 and 11 months (350 eggs) and the third at 13 to 14 months (310 eggs) respectively.

Estudié el efecto de agregar calcio al alimento sobre el desarrollo del caracol pulmonado africano Limicolaria flammea (Müller). La cantidad de calcio tuvo una correlación positiva con el peso corporal (T de Student, p < 0.01; r = 0.96, p < 0.0001) y la longitud de concha (T de Student, p < 0.01; r = 0.96, p < 0.00001). Los caracoles que no recibieron calcio murieron en gran cantidad y no produjeron huevos. En un experimento a largo plazo, hubo picos de consumo del calcio y el mayor aumento de peso fue en los seis meses iniciales. Los picos de producción de huevos fueron entre los seis y los ocho meses (535 huevos), entre los diez y once meses (350 huevos) y en los meses 13 y 14 (310 huevos).

An ultrastructural study of the seminal vesicle of the hermaphrodite duct of the land snail Limicolaria flammea (Müller) (Pulmonata: Achatinidae).

The seminal vesicle region of the hermaphrodite duct of the edible land snail, Limicolaria flammea (Müller) is described using light and electron microscopy. The lumen is lined with a single layer of epithelial cells surrounded by connective tissues and circularly arranged smooth muscle. Transmission electron microscopy reveals that there are two types of epithelial cells lining the lumen of the seminal vesicle duct. Type 1 epithelial cells are highly ciliated columnar with large irregular shaped basal nuclei. Type 2 epithelial cells are non-ciliated columnar with large irregularly shaped basal nuclei. The apical surface of the Type 2 cell bears numerous microvilli. Mitochondria, glycogen, lipids, rough and smooth endoplasmic reticulum, lysosomes, Golgi bodies and vacuoles are observed in the two types of epithelial cells and their lateral margins are joined apically by zonula adhaerens, below which are located septate junctions. The functional significance of the epithelial cells are discussed.

Reproductive cycle of the mangrove prosobranch, Pachymelania fusca (Gmelin, 1791) var. quadriseriata (Gray) (Gastropoda: Melaniidae) in Lagos, Nigeria.

The reproductive activity of the mangrove prosobranch, Pachymelania fusca was studied monthly in the University of Lagos mangrove swamp, at the edge of the Lagos lagoon. The reproductive cycle was analysed from November 2003 to March 2005 by histological examination and macroscopic features of the gonads. Four gonadal stages are described: recently spawned, unripe, ripe and spawning gonads. Sex ratio obtained during this study was 1: 0.95; (51.24% males, 48.76% females). On month by month, there were three peaks when there were more females than males; October-December 2003, October-December 2004 and February-March 2005. Histological analyses revealed that reproductive activity was synchronous in both sexes, from October to March, the exact timing appearing to vary in successive years by about one month. Spawning occurred at end of rainy season and the beginning of the dry season, when the salinity of the water ranged from about 0.5-25.5 psu and surface water temperature was 29-30 degrees C. The resting phase was April to June, during the rainy and low salinity season when the mudflat is flooded and the water turbulent. It is suggested that the species limits its breeding season to a period when there is sufficient food available and when the eggs and larvae will not be washed away.

Thermal tolerance and evaporative water loss of the mangrove prosobranch Tympanotonus fuscatus var. radula L. (Cerithiacea: Potamididae).

Rate of weight loss and mortality, of the Nigerian periwinkle, Tympanotonus fuscatus var. radula L. were investigated during prolonged exposure to air for one month. Short term thermal tolerance in the laboratory was carried out by heating the water in which the animals are placed at the rate of 1 degree C every 10 min. The group exposed to air continued to lose weight; when the experiment was terminated after 4 weeks, 20% of body weight was lost and 5 out of 40 periwinkles died, while the control experimental snails lost 11% of body weight, due to starvation. The species has an upper lethal temperature of 46-48.5 degrees C, much higher than the temperature of its habitat. Survival of T. fuscatus var. radula out of water and adaptation to high temperature suggests the presence of highly adaptive mechanisms of water balance and metabolism.

Gross morphology and ultrastructural study of albumen gland of the land snail Archachatina marginata ovum (Pfeiffer) (Pulmonata: Achatinidae).

The gross morphology of the albumen gland of the edible land snail Archachatina marginata ovum (Pfeiffer) was studied by measurement of the shell length of the snails and wet weight of albumen gland of specimens collected from wild. Additionally, the structure of the albumen gland was studied by light and electron microscopy. The gland is large during the breeding season and there is no correlation between its weigh and the shell length of the snail. The albumen gland is made up of tubules which consist of closely packed single layer of elongated columnar secretory cells arranged radially around a central lumen. The secretory cells have large nuclei, secretory granules and are densely packed with rough endoplasmic reticulum. The secretory cells of the albumen gland produce secretions which are massively stored in their cytoplasm. Two types of secretions were identified, small droplets and large globules. The large globule was so extensive that the diameter of the cell was greatly reduced. TEM shows that the secretory globules contain fine morular granules characteristic of glycogen in several cell types and probably beta-glycogen.