EVALUATING THE GENETIC DIVERSITY AND HEAVY METAL COMPOSITION OF PERIWINKLE (TYMPANOTONUS FUSCATUS VAR. RADULA) AT THE SHORELINE OF UNIVERSITY OF LAGOS, NIGERIA

Akeredolu et al

ABSTRACT
Heavy metal pollution constitutes a threat to life in aquatic environment. Information
on the effect of heavy metals on the genetic diversity of periwinkle remains scanty in
literature .Thus a study was carried out in two sites along the heavy metal polluted
shoreline of the University of Lagos, Nigeria to determine the effect of heavy metals on
the genetic diversity of periwinkles (Tympanotonus fuscatus var. radula).The
concentration of heavy metals namely: Chromium (Cr), Zinc (Zn), Cadmium (Cd) and
Lead (Pb) in water, sediment and periwinkles collected from the two sites were
determined and compared. The effect of heavy metal on the species from the two study
locations was determined using the Random Amplified Polymorphic DNA. The gene
diversity among the populations from both sites was calculated using Shannon
information and Nei’s heterozygozity indices. The concentration of heavy metals in
water from the two sites ranged as follows: Pb (0.77+ 0.13 to 0.79+ 0.09mg/l), Ni (0.08+
0.03mg/l) Zn (0.95+0.01 mg/l) Cr (0.08+ 0.10 to 0.65+0.05mg/l). The mean
concentration of metals in Sediments: Pb (0.82+0.02µg/g), Ni (0.51+ 0.39µg/g),
Cr(0.65+ 0.05µg/g),were higher at the unrestricted site than in the restricted site with
values: Pb (0.80+0.09µg/g), Ni (0.09+ 0.01µg/g), Cr(0.36+ 0.025µg/g) respectively.
Cadmium (Cd) was not detected in water and sediment samples collected from both
sites. The mean concentration of heavy metals recorded in tissues of periwinkles
obtained from both the unrestricted and restricted sites exceeded the WHO and FEPA
recommended allowable limit for seafood. Genetic analysis revealed a greater
heterozygosity (0.239+0.03), higher polymorphism (88.24%) and higher Shannon’s
information index (0.383+0.05) among periwinkle obtained from the controlled site
than the unregulated site. The study concluded that incidence of heavy metal pollution
in the unregulated site accounts for the lower genetic diversity observed.
Keywords: Periwinkles, Biomonitoring,Random Amplified Polymorphic DNAAnalysis