Comparative evaluation of Molluscicidal effects of Securidaca longepedunculata ( Fres . ) and Tephrosia bracteolate ( Guilland Perr ) on Bulinus globosus

The molluscicidal activities of ethanoic and methanoic extracts of the leaves, stem barks and roots of Securidaca longepedunculata and Tephrosia bracteolate against bred Bulinus globosus measured 0.50mm to 0.90mm in size, were investigated. The snails were exposed to a serial dilution of 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, 5.0, 7.5 and 10.0ppm of the ethanoic and methanoic extracts of the leaves, stem barks and roots of S. longepedunculata and T. bracteolata for 24hrs. All tested extracts showed varied snail mortality rates with the different concentrations of ethanoic and methanoic extracts of the plants parts from 0.0 – 100.0%. The lethal concentration LC50 values ranged from 0.15-0.60ppm and LC90 values from 0.80-6.90ppm for both ethanoic and methanoic extracts of S. longepedunculata for 24hrs. The two plants showed significant difference (P<0.05) in the mortality rates of the snails (B. globosus).


INTRODUCTION
The toxicity of active ingredients of certain plants to freshwater snails usually leads to death or densities decrease their, Adewumi C. O. and Marquis V. O (1981) & Olofintoye L. K and Akinbile P. A. (2007).The presence of Bulinus globosus in different freshwater habitats in Ekiti State as an important vector of human schistosomiasis has been reported, Olofintoye L. K. (2001); Odaibo A. B. (2004) and Olofintoye L.K. (2005).In addition, the endemicity of Schistosomiasis which may probably results to chronic and debilitating disease that affects people who have had contact with freshwater harbouring infected snails has been observed in the study area, Odaibo A. B. (2004) and Olofintoye L.K. (2005).
The need for control of the freshwater snails is imperative.
Therefore, the use of natural plant products as molluscicides were used instead of chemical ones which considered as a source of pollution.Earlier on, some of these medicinal plants have been used in the Laboratory to control freshwater snails.Some of these include, the works of Adewumi and Marquis (1981), Olofintoye and Akinbile (2007), Vasconcellos and Amorin, (2003), Jose et al. (2003), Azare et al. (2007) and Albuquerque et al. (2006).This study was planned to evaluate the molluscicidal affect of Securidaca longepedunculata and Tephrosia bracteolate in the control of Schistosome snail vector B. globosus.

MATERIAL AND METHODS
Ethanoic and methanoic extracts were obtained form the leaves, stem barks and root parts of Securidaca longepedunculata and Tephrosia bracteolate collected from forest regrowth and margins in Ado-Ekiti, Ekiti State, Nigeria.Different concentrations were prepared from vacuum dried methylonic extract of purified leaf, stem bark and root of S. longepedunculata and T. bracteolate.(the stock solution concentration).The stock solution was diluted with distilled water.Nine different concentrations (0.1, 0.2, 0.5, 1.0, 2.0, 3.0, 5.0, 7.5 and 10.0ppm) were prepared following the method of Sukumaran et al. (2002) and Azare et al. (2007).For the toxicity test newly hatched juveniles of B. globosus which were collected from Ofin stream in Ado-Ekiti in 2009 were use.

Toxicity Test
Ten juvenile snails measured 0.50mm -0.90mm in size were.exposed to 9 different concentrations each of the extracts.The toxicity test was replicated thrice per concentration for 24 -h .Thereafter, the number of died juvenile snail was counted after 24 -hr recovery in distilled water.H. (1987) andMorais S. M. (2005).The two plants are commonly available in the study area.The molluscicidal potency of the extracts of the plants used was tested statistically using chisquare analysis (X 2 ) and the 95% confidence interval (C.I) was derived for the percentage morality of the snails per concentration.

RESULTS AND DISCUSSION
The molluscicidal activities of leafs stem bark and roots of S. longepedunculata and T. bracteolate with ethanol and methanol extracts at different concentrations (0.100m -10.0ppm) are shown in Tables 1&2.
Table 1 shows the peak molluscicidal activity of leaf, stem bark and the root of S. longepedumculata with ethanol and methanol extracts at 10.0ppm concentration ranged from 70%, C. I = 0.42 -0.98 to 100%, C.I = 0.0-0.0,morality rates of juveniles of B. globosus for 24hrs exposure.However, the molluscicidal potency of ethanol extract with the leaf, stem bark and root of S. longepedunculata showed higher potency of mortality rates of 100.0%,C.I = 0.0 -0.0 at 10ppm for 24hrs than the methanol extract.
The lethal concentrations LC 50 of S. longepedunculata with ethanol were 0.15ppm of the leaf, 0.19ppm of the stem bark and 0.18ppm of the root.
The lethal concentrations LC 90 of S. longepedunculata with ethanol extral were 0.80ppm of the 1.80 ppm leaf, of the stem bark and 6.70ppm of the root at 24hrs exposure.(Table 1).
The molluscicidal effect of methanol extract with leaf, stem bark and root of S. longepedunculata showed peak mortality rates of 90.0%, C.I = 0.71-1.09at 10.0ppm at 24hr.but less than what was observed with ethanol extract in Table 1.Similarly, very low mortality rate of 0.0%, C.I = o.0 -0.0 at 0.10ppm was recorded with stem bark extract for 24hrs (Table 1).
The lethal concentration LC 50 of S. longepedunculata with methanol extract were 0.55ppm of the leaf, 0.60ppm of the stem bark and 0.21ppm of the root.The Lethal concentration LC 90 of S. longepedunculata with methanol extract were 3.10ppm of the leaf, 2.50ppm of the stem bark and 2.90ppm of the root for 24hr exposure.These LC 50 and LC 90 values agree well with the findings of Ebenso I. E. (1992) and TRipaths S. M. and Singh D. K. (2000).
Statistically, the molluscicidal potency of the leaf, stem bark and the root of S. longepedunculata with ethanol and methanol extracts showed significant difference in the mortality rates of juvenile B. globosus (P<0.05) at different concentrations for 24hrs exposure.The molluscicidal activities of S. longepedunculata on juvenile B. globosus may probably due to the active ingredients of saponinglycosides of Oleanolic acid, Tannins and Vateriannate methylsaliciate Kloss H. (1987);Morais S. M. (2005).
The lethal concentrations LC 50 of T. bracteolate with ethanol extract were 0.19ppm of the leaf, 0.45ppm of the stem bark and 0.35ppm of the root for 24-hrs and the lethal concentrations LC 90 of T. bracteolate with ethanol extract were 1.60ppm of the leaf, 1.80ppm of the stem bark and 1.90ppm of the root for 24-hrs.
With methanol extract, the concentrations LC 50 of T. bracteolate were 0.18ppm of the leaf, 0.30ppm of the stem bark and 0.44ppm for 24-hr.LC 90 recorded 0.90ppm of the leaf, 1.20ppm of the stem bark and 2.40ppm of the root for 24-hrs.The lethal concentrations of LC 50 and LC 90 values observed in this plant were lower than the findings of Hashem and Fetyani, TRipaths S. M. and Singh D. K. (2000).
Chi Square (X 2 ) analysis shows that moluscicidal potency of the leaf, stem bark and the root of the T. bracteolate with ethanol and methanol extracts revealed significant difference in the mortality rate of juvenile B.globosus (P<0.05) at different concentrations for 24-hrs.It then suggests that the molluscicidal potency of the T. bracteolataon juvenile of B. globosusmay probably due to active ingredients of Degcidin, Tephrosin, Toxi-carol, Temphrasal, Quoscentrin, Rutin and Rotenone Tahraoui A. E.J.( 2007) and Agra, M. F.(2007).
In conclusion, the use of S. longepedunculata and T. bracteolate products as molluscicides in the control of schistosome vector B.globosus may play a vital role, since the plants are commonly available all the year round in the study area.

Table 1 :
Mortality rates of leaf, stem bark and root of S. longepedunculata with ethanonic and methanoic extracts against B. globosus.

Table 2 :
Mortality rates of leaf, stem bark and root of T. bracteolata with Ethanonic and methanoic extracts against B. globosus.