Content uploaded by Obiora Osegboka Ikpeze
Author content
All content in this area was uploaded by Obiora Osegboka Ikpeze on May 10, 2016
Content may be subject to copyright.
Content uploaded by Obiora Osegboka Ikpeze
Author content
All content in this area was uploaded by Obiora Osegboka Ikpeze on May 06, 2016
Content may be subject to copyright.
Ikpeze and Obikwelu Int. J. Pure App. Biosci. 4 (2): 91-102 (2016) ISSN: 2320 – 7051
Copyright © April, 2016; IJPAB 91
Factors affecting seasonal abundance of gastropods of public health
importance found at Agulu Lake shorelines in Nigeria
O.O. Ikpeze* and M.E. Obikwelu
Department of Parasitology & Entomology, Nnamdi Azikiwe University, PMB 5025, Awka, Nigeria
*Corresponding Author E-mail: oo.ikpeze@unizik.edu.ng
Received: 10.04.2016 | Revised: 16.04.2016 | Accepted: 18.04.2016
INTRODUCTION
Schistosomiasis is a parasitic infection that is
endemic in 76 countries of the world
1
, and
second to malaria in terms of socio – economic
and public health significance particularly in 44
endemic countries in Africa including Nigeria
2
where large populations of children are infected
by the age of fifteen
3,4
. Gastropods have diverse
habitats in freshwater, marine and terrestrial
environments
5
. It has been stated that without
snails there can be no Schistosomiasis and
because Schistosome transmitting snails occur in
very particular ecological circumstances that are
subject to rapid change in an increasingly human
– dominated world, understanding the future of
this neglected yet persistent human diseases
require experiences on how snail species are
being affected by global changes in climate,
increased pollution of aquatic habitats, continued
transport of exotic and invasive species,
construction of dams and irrigation systems,
mass movement of humans and changes in
human population density and standard of
living
6
.
Available online at www.ijpab.com
ISSN: 2320 – 7051
Int. J. Pure App. Biosci. 4 (2): 91-102 (2016)
Research Article
ABSTRACT
Agulu Lake is one of 366 geo-referenced Schistosomiasis endemic foci in Nigeria. There is a dearth
of publication on the gastropod intermediate hosts for larval stages of Schistosoma haematobium
that cause urinary Schistosomiasis in Agulu. Gastropod abundance was determined by sampling
eight stations on Agulu Lake shorelines from November 2012 to October 2013, using scoop net
sampling and hand picking techniques, supplemented by 20 minutes manual search over aquatic
plants and suspended materials in each sampled quadrat. Total abundance of gastropods
encountered was 6866, which comprised Bulinus globosus 1957(28.5%), B. truncatus 1832(26.7%),
B. forskalii 964(14%), Lymnaea natalensis 2089(30.4%) and Melanoides tuberculatus 24(0.4%).
Mean seasonal density of gastropod/m
2
was 4.81±3.07 for dry season and 3.77±2.63 for rainy
season while spatial density for Agulu and Nri arms of the lake were 5.1±4.43 and 3.48±2.3,
respectively. Generally, gastropod density was strongly and positively correlated with calcium ions
but negatively correlated with water transparency, depth, dissolved oxygen and pH. However, water
temperature showed little influence on gastropod abundance. Further work on molecular
identification of the gastropods and their Schistosome infectivity status is needed because of human-
water-contact activities in Agulu Lake and its environs.
Keywords: Agulu Lake, water parameters, Gastropod density, Schistosomiasis
DOI: http://dx.doi.org/10.18782/2320-7051.2264
Cite this article:
Ikpeze, O.O. and Obikwelu, M.E., Factors affecting seasonal abundance of gastropods of
public health importance found at Agulu Lake shorelines in Nigeria, Int. J. Pure App. Biosci. 4(2): 91-102
(2016).
doi: http://dx.doi.org/10.18782/
2320
-
7051.2264
Ikpeze and Obikwelu
Copyright © April, 201
6; IJPAB
Human interventions in developing water
systems have affected ecology of aquatic
environments creating favorable
aquatic fauna, and have greatly increased the
prevalence of gastropods and trematode
infections in several countries
trematodes and their gastropod intermediate
hosts are integral parts of the freshwater
ecosystem in which their
distributions appear to
be focalized.
Bulinus, Biomphalaria and
Onchomelania
species have been associated
with specific Schistosome parasites of man.
Genus Bulinus host
Schistosoma haematobium
and S. intercalatum while
Biomphalaria
Onchomelania specie
s transmit
S. japonicum respectively
8
. Water temperature,
transparency, pH, dissolve oxygen and calcium
ion concentration are among water parameters
known to operate in lake ecosystems
of water bodies and transparency are found t
affect distribution of freshwater invertebrate
dwellers. These factors combine to determine
water quality and generally affect the population
of freshwater gastropods
10
. Rainfall appears to
pose the greatest influence on freshwater snails’
distribution a
nd population dynamics. In
Nigeria, there are profound periods of dry and
rainy seasons and gastropods are able to
aestivate during unfavorable conditions
especially in the temporary waters systems. The
presence of freshwater gastropods suggests
possibilit
y of parasites transmission in an area.
Therefore targeting the intermediate hosts
remains an essential component of the integrated
control strategies in a Schistosomiasis endemic
area because of the cost effectiveness of other
control methods, and the fac
t that certain water
associated activities like washing, swimming
and fishing which are essential for the
transmission of the disease are not likely to
Fig. 1: (a)
The 366 Schistosomiasis haematobium Geo
(b)
The 8 stations sampled for gastropods along Agulu Lake shorelines
Lake.
Int. J. Pure App. Biosci. 4 (2): 91-102 (2016)
6; IJPAB
Human interventions in developing water
systems have affected ecology of aquatic
environments creating favorable
conditions for
aquatic fauna, and have greatly increased the
prevalence of gastropods and trematode
infections in several countries
7
. Parasitic
trematodes and their gastropod intermediate
hosts are integral parts of the freshwater
distributions appear to
Bulinus, Biomphalaria and
species have been associated
with specific Schistosome parasites of man.
Schistosoma haematobium
Biomphalaria
and
s transmit
S. mansoni and
. Water temperature,
transparency, pH, dissolve oxygen and calcium
ion concentration are among water parameters
known to operate in lake ecosystems
9
. The depth
of water bodies and transparency are found t
o
affect distribution of freshwater invertebrate
dwellers. These factors combine to determine
water quality and generally affect the population
. Rainfall appears to
pose the greatest influence on freshwater snails’
nd population dynamics. In
Nigeria, there are profound periods of dry and
rainy seasons and gastropods are able to
aestivate during unfavorable conditions
especially in the temporary waters systems. The
presence of freshwater gastropods suggests
y of parasites transmission in an area.
Therefore targeting the intermediate hosts
remains an essential component of the integrated
control strategies in a Schistosomiasis endemic
area because of the cost effectiveness of other
t that certain water
-
associated activities like washing, swimming
and fishing which are essential for the
transmission of the disease are not likely to
change with health education or provision of
treated portable water
urinary Schisto
somiasis in Agulu community
have been extensively studied
there is dearth of information on the abundance
of freshwater gastropods that are intermediate
hosts of human and
animal trematodes
urinary Schistosomiasis in the are
the present study on abundance of freshwater
gastropods of public health importance in Agulu
Lake area of Anambra State Nigeria was to
identify the gastropods, determine their seasonal
and spatial distributions and establish any
relationship
between their density and some
water parameters of Agulu Lake shorelines.
MATERIALS AND METHODS
Study area:
Agulu (latitude 6º06
longitude 7º03
ˈE) has an outstanding terrain that
rises from the Niger valley in the West to a
height of about 1000 feet
Lake in is one the 366 Schistosomiasis
haematobium Geo-
referenced endemic foci in
Nigeria
18
. The lake is approximately 81 hectares
and stretches for about 2 kilometers, and is the
Head-
stream of Idemili River which is tributary
of t
he River Niger. It is bounded by three
communities of Agulu, Nri, and Adazi
whose inhabitants utilize the lake for washing,
drinking, fishing, swimming, cassava
fermentation, and for isolated ritual purposes.
Many commercial outfits including a Nati
Diagnostic Centre and a University Faculty of
Pharmaceutical Sciences are located in around
the area.
Sample stations and snail sampling
technique:
Eight (8) sample stations were
selected along the arms of Lake; 4 each on the
Agulu- and Nri-
arms, res
The 366 Schistosomiasis haematobium Geo
-
referenced endemic foci in Nigeria [18] include Agulu Lake,
The 8 stations sampled for gastropods along Agulu Lake shorelines
(c)
Human activity at Station 1 of Agulu
ISSN: 2320 – 7051
6; IJPAB
92
change with health education or provision of
treated portable water
11
. The prevalence of
somiasis in Agulu community
have been extensively studied
12,13,14,15,16,17
but
there is dearth of information on the abundance
of freshwater gastropods that are intermediate
animal trematodes
that cause
urinary Schistosomiasis in the are
a. The aim of
the present study on abundance of freshwater
gastropods of public health importance in Agulu
Lake area of Anambra State Nigeria was to
identify the gastropods, determine their seasonal
and spatial distributions and establish any
between their density and some
water parameters of Agulu Lake shorelines.
MATERIALS AND METHODS
Agulu (latitude 6º06
ˈN and
E) has an outstanding terrain that
rises from the Niger valley in the West to a
height of about 1000 feet
above sea level. Agulu
Lake in is one the 366 Schistosomiasis
referenced endemic foci in
. The lake is approximately 81 hectares
and stretches for about 2 kilometers, and is the
stream of Idemili River which is tributary
he River Niger. It is bounded by three
communities of Agulu, Nri, and Adazi
-Nnukwu
whose inhabitants utilize the lake for washing,
drinking, fishing, swimming, cassava
fermentation, and for isolated ritual purposes.
Many commercial outfits including a Nati
onal
Diagnostic Centre and a University Faculty of
Pharmaceutical Sciences are located in around
Sample stations and snail sampling
Eight (8) sample stations were
selected along the arms of Lake; 4 each on the
arms, res
pectively (Figure 1).
referenced endemic foci in Nigeria [18] include Agulu Lake,
Human activity at Station 1 of Agulu
Ikpeze and Obikwelu
Copyright © April, 201
6; IJPAB
A quadrat of 20m
2
along the shoreline was
delineated from each of the 8 stations and
sampled for gastropods once monthly from
November 2012 to October 2013 hydrologic
year, using scoop n
et and hand picking
technique for collection of snails as described
by
19,20,21
. All snails recovered were kept in pre
labeled plastic containers
22
which were taken to
the laboratory for counting and identification
Relative size measurements of the identi
species were depicted centimeters.
Analysis and measurements of water
parameters:
Water samples from each station
were analyzed for pH, Dissolved Oxygen (DO),
and Calcium ion using standard laboratory
procedures.
Water temperature, transparency and
depth were also recorded in situ.
Statistical analysis:
Descriptive statistics were
computed for all relevant data. Chi square (
Fig. 2:
Relative scale measurements (millimeters) of representative samples of fresh water Gastropods recovered
from shorelines of Agulu Lake.
(a)
natalensis; (e)
Melanoides tuberculatus
Tables 1 showed the seasonal variations in
abundance and density of the 5 species of
freshwater gastropod encountered in Agulu Lake
shorelines. The higher abundance of gastropods
in dry season than rainy season is in agreement
with the report
20
that snails’ population expands
in dry season and contracts during the rainy
Int. J. Pure App. Biosci. 4 (2): 91-102 (2016)
6; IJPAB
along the shoreline was
delineated from each of the 8 stations and
sampled for gastropods once monthly from
November 2012 to October 2013 hydrologic
et and hand picking
technique for collection of snails as described
. All snails recovered were kept in pre
-
which were taken to
the laboratory for counting and identification
5
.
Relative size measurements of the identi
fied
species were depicted centimeters.
Analysis and measurements of water
Water samples from each station
were analyzed for pH, Dissolved Oxygen (DO),
and Calcium ion using standard laboratory
Water temperature, transparency and
Descriptive statistics were
computed for all relevant data. Chi square (χ
2
)
analysis was used to compare the association
among groups for statistical significance.
Correlation analysis was also used to compare
relationship between gastropod density and
values determined for water parameters of the
lake.
RESULTS AND DISCUSSIONS
Five species of fresh water gastropods namely,
Bulinus globosus, Bulinus truncatus, Bulinu
forskalii, Lymnaea natalensis
tuberculatus
were encountered in Agulu Lake
shorelines and their comparative sizes and
characteristic shapes are shown in Figure 2. Co
existence of
M. tuberculatus
trematode vectors like
B. globosus
and
Lymnaea natalensis
several water bodies by other workers
Relative scale measurements (millimeters) of representative samples of fresh water Gastropods recovered
(a)
Bulinus globosus; (b) Bulinus truncatus; (c)
Bulinus forskalii
Melanoides tuberculatus
.
Tables 1 showed the seasonal variations in
abundance and density of the 5 species of
freshwater gastropod encountered in Agulu Lake
shorelines. The higher abundance of gastropods
in dry season than rainy season is in agreement
that snails’ population expands
in dry season and contracts during the rainy
season. A seasonal trend in species population
with high population peak during and or shortly
after the rainy season was also reported
However, seasonal fluctuat
has been tagged to seasonal rainfall pattern and
habitat volume
25
.
M. tuberculatus
shorelines had similar pattern with other widely
ISSN: 2320 – 7051
6; IJPAB
93
analysis was used to compare the association
among groups for statistical significance.
Correlation analysis was also used to compare
relationship between gastropod density and
values determined for water parameters of the
RESULTS AND DISCUSSIONS
Five species of fresh water gastropods namely,
Bulinus globosus, Bulinus truncatus, Bulinu
s
forskalii, Lymnaea natalensis
and Melanoides
were encountered in Agulu Lake
shorelines and their comparative sizes and
characteristic shapes are shown in Figure 2. Co
-
M. tuberculatus
with other
B. globosus
, B. truncatus
Lymnaea natalensis
has been reported in
several water bodies by other workers
19,23
.
Relative scale measurements (millimeters) of representative samples of fresh water Gastropods recovered
Bulinus forskalii
; (d) Lymnaea
season. A seasonal trend in species population
with high population peak during and or shortly
after the rainy season was also reported
9
.
However, seasonal fluctuat
ions in snails’ density
has been tagged to seasonal rainfall pattern and
M. tuberculatus
in Agulu lake
shorelines had similar pattern with other widely
Ikpeze and Obikwelu Int. J. Pure App. Biosci. 4 (2): 91-102 (2016) ISSN: 2320 – 7051
Copyright © April, 2016; IJPAB 94
documented reports
26,27,28,29,30,31
. Lower
gastropod density in late wet season of July to
October (Figure 3) indicated that most snail
species would be washed to different places or
into the lake where they died easily but L.
natalensis which mostly implicated in
Fasciolosis in ruminants in the area and which
attached to elephant grasses, showed higher
density in rainy season (Figure 4). Generally,
rainfall possesses greatest effect on freshwater
snails’ population dynamics
11,32
as heavy
flooding that usually accompanied rainfall aided
in the dispersal of aquatic fauna including
gastropods, thereby decreasing their density in
the given foci. Flooding does not support high
density of snail species, and low snail density
during the peak rainy season has been attributed
to flushing out of snails by flood waters
33,34,35,36
.
Dry season has been associated with high rates
of biological activities as well as increased
frequency of snails’ occurrence
36
. The prevailing
ecological conditions during dry season is
therefore regarded as being more favorable to
snails than those of rainy season
37
.
Table 1. Seasonal variations in freshwater gastropod abundance in Agulu Lake shorelines
Season Bulinus
globosus Bulinus
truncatus Bulinus
forskalii Lymnaea
natalensis Melanoides
tuberculatus *Abundance
‡Density
(n=1957)
28.46% (n=1832)
26.68% (n=964)
14.03% (n=2089)
30.42% (n=24)
0.35 % (n=6866)
100%
Dry season:
Nov-2012 404 357 198 265 0 1224 7.65
Dec- 2012 386 409 186 224 0 1205 7.53
Jan-2013 276 257 22 100 0 655 4.09
February 133 146 31 94 2 406 2.54
March 101 113 63 78 0 355 2.22
*Abundance 1300 1282 500 761 2 3845
‡Density 8.12 8.01 3.13 4.76 0.0125 Mean± SD=4.81±3.07
Relative % 18.90 18.67 7.28 11.08 0.03 56
Rainy season:
April 2013 32 99 74 109 0 314 1.96
May 105 136 169 412 11 833 5.21
June 217 108 83 443 7 858 5.36
July 93 15 8 127 3 246 1.54
August 60 17 82 51 0 210 1.31
September 45 74 12 78 0 209 1.31
Oct-2013 105 101 36 108 1 351 2.19
*Abundance 657 550 464 1328 22 3021
‡Density 4.11 3.43 2.9 8.3 0.1375 Mean± SD=3.77±2.63
Relative % 9.56 8.01 6.75 19.34 0.32 44
* Abundance = Total individuals, ‡Density of Gastropod/m
2
= Abundance ÷ (no. of quadrats x area of each quadrat)
24
.
Fig. 3: Monthly\ seasonal trends in gastropod density in Agulu Lake shorelines
7.65 7.53
4.1
2.54 2.22 1.96
5.21 5.36
1.54 1.31 1.3 2.19
0
1
2
3
4
5
6
7
8
9
Gastropod/m²
Density
← Dry season →← Rainy season →
Ikpeze and Obikwelu Int. J. Pure App. Biosci. 4 (2): 91-102 (2016) ISSN: 2320 – 7051
Copyright © April, 2016; IJPAB 95
Fig. 4: Seasonal density of individual gastropod species in Agulu Lake shorelines
Table 2 showed the spatial variations in
abundance of the 5 species of freshwater
gastropod in Agulu Lake shorelines. B. globosus
and B. truncatus were present at all stations
against others that were absent from one or more
stations. B. forskalii was not encountered at
stations 1 to 5 while L. natalensis was absent
from stations 6 to 8. The co-existence of the sub-
class Pulmonata in same foci signified they have
same ecological niche but the absence of L.
natalensis from two stations 6, 7 and 8 located at
Nri arm of the lake could mean that the species
dispersal is moving northward from Agulu arm
or that limnological conditions there were not
favourable for the species survival. Physa acuta
was observed in Agulu Lake area where it co-
existed with Bulinus species
16
. However we did
not recover Physa species; perhaps P. acuta had
gone into extinction since
16
also reported that
only six Physa acuta were identified out of
hundreds of other snails collected by them.
Bulinus species were collected from sub-merged
plant vegetations at the water shores, while most
of the lymnaeid snails were observed attaching
themselves to floating materials on the
peripheral surface of water near the bank. This
observation is a confirmation to the report of that
freshwater lymnaeid seemed to prefer peripheral
sites of water bodies
24
. Spatial distributions of
the freshwater gastropods also differ
significantly between the stations
(Figure 5).
Variations in gastropods’ density at
sampled stations could be linked with nature and
level of human-water contact activities. Human
activities like fetching of water, washing of farm
tools and produce, bathing, swimming and
fishing observed in Agulu Lake were also
reported in River Ulasi in southern Nigeria
2
and
in Opa Reservoir and Research Farm Pond
23
,
where mean duration of individual contact
ranged from 1 minute of washing limbs to more
than 5 hours of fishing. Higher numbers of snails
collected from stations 1, 2, 5, and 7 (Figure 5)
were thought to be related to increased
frequency of contacts due to human activities at
these sites which apparently created favourable
microhabitats for the gastropods
38
. Zones of
different human activities have been referred to
as shallow shocked areas where one would
collect aquatic organisms
39
. Definitely polluted
Agulu Lake is a still water body, the kind which
would necessitate the establishment of snail
species
40
. The overall low density of M.
tuberculatus observed in both Agulu and Nri
arms of the lake (Figure 6) could be due to their
habitats at edges of river beds and stream banks
where water current is high
30,31,41
as well as their
nocturnal behavior
42
.
8.13 8.01
3.13
4.76
0.01
4.1 3.44 2.9 8.3 0.14
0
1
2
3
4
5
6
7
8
9
10
B. globosus B. truncatus B. forscalii L. natalensis M. tuberculatus
Gastropod/m²
Dry season Rainy season
Ikpeze and Obikwelu Int. J. Pure App. Biosci. 4 (2): 91-102 (2016) ISSN: 2320 – 7051
Copyright © April, 2016; IJPAB 96
Table 2. Spatial variations in freshwater gastropod abundance in Agulu Lake shorelines
Stations Bulinus
globosus
Bulinus
truncatus
Bulinus
forskalii
Lymnaea
natalensis
Melanoides
tuberculatus
*Abundance ‡Density
(n=1957)
28.5%
(n=1832)
26.7%
(n=964)
14%
(n=2089)
30.4%
(n=24)
0.4%
(n=6866)
100%
Agulu Arms:
Station 1 481 517 0 1012 10 2020 12.63
Station 2 413 393 0 685 6 1497 9.35
Station 3 101 98 0 109 1 309 1.93
Station 4 83 146 0 25 3 257 1.6
*Abundance 1078 1154 0 1831 20 4083
‡Density 6.74 7.21 0 11.44 0.125 Mean± SD=5.1±4.43
Nri Arms:
Station 5 204 314 0 258 3 779 4.87
Station 6 110 67 109 0 0 286 1.79
Station 7 486 216 682 0 1 1385 8.66
Station 8 79 81 173 0 0 333 2.08
*Abundance 879 678 964 258 4 2783
‡Density 5.49 4.24 6.03 1.61 0.025 Mean± SD=3.48±2.3
* Abundance= Total individuals; ‡Density (Gastropod/m
2
) = Abundance ÷ (no. of quadrats) x (area of each quadrat)
24
Fig. 5: Overall gastropod density at Stations in Agulu Lake shorelines
12.63
9.35
1.93 1.6
4.87
1.79
8.66
2.08
0
2
4
6
8
10
12
14
12345678
Gastropod/m²
Density
←Stations on Agulu-arm →← Stations on Nri-arm →
Ikpeze and Obikwelu Int. J. Pure App. Biosci. 4 (2): 91-102 (2016) ISSN: 2320 – 7051
Copyright © April, 2016; IJPAB 97
Fig. 6: Specific gastropod density in Agulu-arm and Nri-arm of Agulu Lake shorelines
The recent attack and killing of a school pupil by
a crocodile in Agulu Lake has made the lake a
high risk area. The incidence had drastically
reduced the frequency of human-water contacts.
However, wary local farmers still plant
vegetables at the banks, while fishermen and
raffia-palm wine tappers who visited the lake
were watchful of crocodile attack, being
ignorant of potential risk of Schistosomiasis
transmission. Reduced frequency of visit to the
lake by children implied that prevalence of
Schistosomiasis among that age-group would
decrease.
It had been observed that pronounced seasonal
variations in temperature and rainfall in tropical
systems influence other physicochemical
characteristic of water bodies
20,42
.
Variations in some physical and chemical water
parameters of sample stations in Agulu Lake
shorelines thought to affect gastropod abundance
such as temperature, transparency, depth;
dissolved oxygen (DO), calcium ion (Ca
++
) and
hydrogen ion (pH) concentrations are shown in
Table 3 while correlation between gastropod
density and these water parameters are presented
in Figure 7.
Table 3: Variations in spatial gastropod density and water parameters of Agulu Lake
Stations Density Temperature Transparency Depth DO Ca
++
pH
(Gastropod/m
2
) ºC cm cm mg/L mg/L
1 12.62 26.6 8.4 13.1 5.4 8.5 7.5
2 9.35 27.6 10.1 14.8 5.6 8.6 7.8
3 1.93 31.0 27.1 33.6 7.1 6.5 9.4
4 1.61 30.8 24.6 28.8 6.7 4.1 9.2
5 4.87 27.2 14.5 16.8 6.6 6.7 8.4
6 1.78 25.2 24.1 26.7 6.7 4.0 9.0
7 8.66 27.7 11.7 17.8 6.2 8.3 7.5
8 2.08 25.4 24.8 36.1 6.9 5.4 9.0
Averages 27.68 18.16 23.46 6.4 6.51 8.47
Water temperature range of 25.2-30.8
0
C
obtained for Agulu Lake (Table 3) was closely
related to those reported from water bodies in
other endemic areas in Nigeria such as 23-33
o
C
in Imo State
20
and 22-28
o
C for Moro Lake in
Kwara State
44
, both in Nigeria. However, water
temperature showed little influence on gastropod
density but we observed that high temperature
beyond 30
o
C (Figure 7a) would be lethal to
gastropod development. As fewer snails were
encountered in hotter periods of March and
April and at Stations 3 and 4 with higher
temperatures.
6.74 7.21
0
11.44
0.125
5.49
4.24
6.03
1.61
0.025
0
2
4
6
8
10
12
14
B. globosus
B. truncatus
B. forscalii
L. natalensis
M. tuberculatus
Gastropod/m²
Agulu-arm Nri-arm
Ikpeze and Obikwelu Int. J. Pure App. Biosci. 4 (2): 91-102 (2016) ISSN: 2320 – 7051
Copyright © April, 2016; IJPAB 98
Water transparency decreased with rains as
flooding washed down suspended materials and
mud soil into the Lake which brought about
turbidity\mixing that led to decrease in the
clearness of the lake. This kind of report had
been noted by
44
who described lower Secchi disc
value due to washing of suspended particles into
Moro Lake. Transparency was also known to
facilitate the penetration of sunlight to the
bottom of water particularly in the littoral zone
encouraging the establishment and proliferation
of aquatic weeds.
Water depth varied according to habitat
stations and such variations accounted for the
differences in the number of snails collected
from various stations. The more polluted the
water is, the less transparent it becomes and such
zones favour snails existence. Thus, habitats
with high depth maintained minimal snail
populations while those with low depth had
maximum numbers of snails (Table 3). The same
situation was reported at Opa Reservoir and
Research Farm pond Ile-Ife, Nigeria by
investigators who observed that Bulinus snails
inhabit the shallow part of the water bodies
45
.
This showed that freshwater snails only colonize
the ecological shorelines of the water bodies
which were regarded as the shallowest part.
There was a linear relationship between
transparency and water depth (Figure 7b&c),
with strong negative correlation between
gastropod density, in line with
25
who attributed
seasonal fluctuations in snails’ density to
variations in habitats’ volume and rainfall.
Variations in Dissolved oxygen (DO)
with temperature observed during this research
supported that DO tended to reduce with
increased temperature
20
. Low range of DO
observed in Agulu Lake was closely related to
the range of 3.2-6.8mg/l reported from Moro
Lake
44
but was far lower than 17-35mg/l
reported for Light House Beach and polluted
Creeks in Lagos
46
. However, low oxygen level
has been linked to slow flowing nature of waters
which could limit oxygen level
47
. Relatively
higher DO at Stations 3 and 8 could be attributed
to lesser use of these sites for microbial activities
because such places were not known as refuse
dumping sites neither were ritual materials found
around the area which would have necessitated
serious microbial putrefaction. The lower values
of DO at Stations 2, 5 and 7 were thought to be
due to cumulative human activities in these areas
and dumping of ritual materials. In such polluted
areas, oxygen would be greatly utilized during
microbial metabolic processes. There was a
negative correlation between DO and gastropod
density (Figure 7d) as the gastropods clustered at
a range of 5.4-7mg/l, similar to 5.1–6.4mg/l at
Opa Reservoir and Research Farm Pond
45
,
suggesting that DO showed little correlation
with snails’ density. It had been observed that
density of pulmonates increased with increasing
DO while that of prosobranchs decreased
21
.
Mostly L. natalensis but not other pulmonates
were seen in the open water at Nri-arm of Agulu
Lake (Figure 6) which suggested that they
needed high oxygen. This exertion agrees with
reports that Lymnaea snails float on water
surface because they require high oxygen
concentration
48,49
.
Calcium ion concentration in Agulu
Lake was found to vary according to sampled
stations and could be dependent on nature and
rate of inflow of materials containing Calcium
compounds from adjoining farms. Cement
substances, chippings and other dusts from
nearby COTAB Construction Company were
also flooded into the lake and could raise its
Ca
++
level. Calcium in Agulu Lake may be
important for snails’ growth, egg laying and
shell building as calcium was important in shell
formation and regulation of tissue permeability
according to workers who also reported that C
9++
in freshwaters was reasonably high to support
snail’s survival in Jos
28
. More gastropods were
collected from Stations 1, 2, 5 and 7 (Figure 5)
where Calcium levels were high
(Table 3), an indication that the Calcium level
was probably up to the range for supporting
snails’ survivals, growth and reproduction. A
strong positive correlation existed between
Calcium ion concentration and gastropod density
(Figure 7e).
Average pH 8.47 of surface waters of
sampled stations in Agulu Lake was in line with
earlier reports in Agulu Lake
50,51
of high pH of
8.45 and 9.00, which conclusively showed that
the lake witnesses an alkaline environment.
Though some authors maintain that pH was
Ikpeze and Obikwelu
Copyright © April, 201
6; IJPAB
rarely a factor limiting snails distribution
our finding was similar to pH ranges of 6.8
and 7.0-8.0
reported from Upper Egypt
Brazil
,32
respectively, as optimally normal for
development of aquatic molluscs. The pH 9.01
and 9.58 for Obutu and Agbu Lakes respectively
in Anambra State
20
indicate that lakes in this part
of the country have alkaline pH
Fig.7:
Correlation between gastropod density and water parameters at Stations in Agulu Lake shorelines. Water
temperature (a), Transparency (b)
, Depth
CONCLUSIONS
This study identified 5
fresh water gastropod
species and determined water parameters that
influence their population abundance and
distribution in Agulu Lake shorelines, the most
important being rainfall and calcium ion
concentration as well as human interventions.
Generally, gastropod density was strongly and
positively correlated with calcium ions but
negatively correlated with water transparency,
depth, dissolved oxygen and pH.
recommended that further studies be carried out
to investigate the extent at whic
environmental factors would be manipulated
under natural and laboratory conditions to
control the population of the gastropods. Further
research on the molecular phylogeny of
snails of Agulu Lake using DNA
characterization will differ
Int. J. Pure App. Biosci. 4 (2): 91-102 (2016)
6; IJPAB
rarely a factor limiting snails distribution
21,51
,
our finding was similar to pH ranges of 6.8
-7.95
reported from Upper Egypt
22
and
respectively, as optimally normal for
development of aquatic molluscs. The pH 9.01
and 9.58 for Obutu and Agbu Lakes respectively
indicate that lakes in this part
of the country have alkaline pH
. More snails
were encountered in sites with slightly alkaline
pH than those with pH values above 9.0 (Table
3). A negative correlation occurred between pH
and gastropod density (Figure 7f) and such
condition appeared to be constant as pH range
was slightl
y above the neutral point, and a good
number of gastropods were collected from
stations where pH ranges from 7.5 to 8.4.
Correlation between gastropod density and water parameters at Stations in Agulu Lake shorelines. Water
, Depth
(c), Dissolved oxygen (d), Ca⁺⁺ (e), and pH (f).
CONCLUSIONS
fresh water gastropod
species and determined water parameters that
influence their population abundance and
distribution in Agulu Lake shorelines, the most
important being rainfall and calcium ion
concentration as well as human interventions.
Generally, gastropod density was strongly and
positively correlated with calcium ions but
negatively correlated with water transparency,
depth, dissolved oxygen and pH.
It is
recommended that further studies be carried out
to investigate the extent at whic
h each of the
environmental factors would be manipulated
under natural and laboratory conditions to
control the population of the gastropods. Further
research on the molecular phylogeny of
Bulinus
snails of Agulu Lake using DNA
characterization will differ
entiate and
conclusively identify the gastropods and
investigate their cercarial infection rates.
Conflict of interests:
The authors declare that
there is no conflict of interests regarding the
publication of this paper.
REFERENCES
1.
WHO. Report of the S
Group on Schistosomiasis.
Report Series,
(2005), 123. (2005).
2.
Okwelogu, I.S., Ikpeze, O.O., Ezeagwuna,
D.A., Aribodor, D.N., Nwanya, A.V.,
Egbuche, C.M., Okolo, K.V. and Ozumba,
N.A. Urinary Schistosomiasis among
school c
hildren in Okija, Anambra State,
Eastern Nigeria.
Biological Science,
3.
Akinwale, O., Ajayi, M., Akande, D.,
Adeleke, M., Gyang, P., Adenenye, A. and
ISSN: 2320 – 7051
6; IJPAB
99
were encountered in sites with slightly alkaline
pH than those with pH values above 9.0 (Table
3). A negative correlation occurred between pH
and gastropod density (Figure 7f) and such
condition appeared to be constant as pH range
y above the neutral point, and a good
number of gastropods were collected from
stations where pH ranges from 7.5 to 8.4.
Correlation between gastropod density and water parameters at Stations in Agulu Lake shorelines. Water
conclusively identify the gastropods and
investigate their cercarial infection rates.
The authors declare that
there is no conflict of interests regarding the
publication of this paper.
REFERENCES
WHO. Report of the S
cientific Working
Group on Schistosomiasis.
WHO Technical
(2005), 123. (2005).
Okwelogu, I.S., Ikpeze, O.O., Ezeagwuna,
D.A., Aribodor, D.N., Nwanya, A.V.,
Egbuche, C.M., Okolo, K.V. and Ozumba,
N.A. Urinary Schistosomiasis among
hildren in Okija, Anambra State,
Eastern Nigeria.
Scholarly Journal of
Biological Science,
1(1): 1-6 (2012).
Akinwale, O., Ajayi, M., Akande, D.,
Adeleke, M., Gyang, P., Adenenye, A. and
Ikpeze and Obikwelu Int. J. Pure App. Biosci. 4 (2): 91-102 (2016) ISSN: 2320 – 7051
Copyright © April, 2016; IJPAB 100
Dike, A. Prevalence of Schistosoma
haematobium infection in a Neglected
Community, South-western Nigeria.
International Journal of Health Research,
2(2): 149-155 (2009).
4. Ogbe, M.G. Schistosomiasis (bilharziasis):
An ancient water-borne disease that occurs
in some of our communities. Zoologist, 1:
91-104 (2002).
5. Brown, D.S. Freshwater snails of Africa
and their medical importance. 2
nd
edition
Taylor and Francis, London, 609 (1994).
6. Loker, E.S. Research on the Molluscan
intermediate hosts for Schistosomiasis:
what are the priorities? Paper presented to
scientific working group on
Schistosomiasis, WHO Geneva,
Switzerland. Molluscan aspect of
Schistosomiasis, Loker (http:// biology as
Loker@unm.edu), 13 (2005).
7. Cheesbrough, M. Parasitological Tests:
examination of urine for Schistosoma
haematobium eggs. In: District Laboratory
Practice in Tropical Countries, low price
edition part 1, ISBN: 0521665485,
Cambridge, United Kingdom: Cambridge
University Press, pp. 178-309 (1998).
8. Ayanda, O.I. Prevalence of snail vectors of
Schistosomiasis and their infection rate in
two localities within Ahmadu Bello
University Zaria, Kaduna State Nigeria.
Journal of Cell and Animal Biology, 3(4):
058-061 (2009).
9. Chingwena, G., Mukaratirwa, S., Chimbari,
H., Kristensen, T.K. and Madsen, H.
Population dynamics and ecology of
freshwater gastropods in the highveld and
lowveld regions of Zimbabwe with
emphasis on Schistosome and Amphistome
intermediate hosts. African Zoology, 39(1):
55-62 (2004).
10. Okoli, E.I and Odaibo, A.B. Urinary
Schistosomiasis among school children in
Ibadan, an Urban Community in South-
western Nigeria. Tropical Medicine and
International Health, 4(4): 308-315 (2002).
11. Yakubu, N., Musa, G. and Sabo, E. Y.
Seasonal changes in the distribution and
infection rate of Schistosome intermediate
hosts in River Kubanni and its tributaries.
Bioscience Research Communications,
15(3): 2007-2011 (2003).
12. Ekwunife, C.A., Okafor, F.C. and
Nwaorgu, O.C. Ultrasonographic screening
of urinary Schistosomiasis infected patients
in Agulu Community, Anambra State,
south-eastern, Nigeria. International
Archives of Medicine, 2:34.
Doi:10.1186/17557682-2-34 (2009).
13. Ekwunife, C.A and Okafor, F.C.
Schistosomiasis infection in primary
schools in Agulu Town of Anambra State,
Nigeria. Animal Research International,
1(3): 203-207 (2004).
14. Emejulu, C.A., Alabaraonye, F.F.,
Ezenwaji, H.M. and Okafor, F.C.
Investigation into the prevalence of urinary
Schistosomiasis in the Agulu lake Area of
Anambra State, Nigeria. Journal of
Helminthology, 68: 119-123 (1994).
15. Emejulu, C.A. Okafor, F.C. and Ezigbo,
J.C. Gastropod fauna of Agulu Lake and
Adjoining freshwater systems in Anambra
State, Nigeria. Journal of Aquatic Sciences,
7: 35-38 (1992).
16. Ude, E.A.G., Akinwale, O.P., Ukaga, C.N.,
Ajayi, M.B., Akande, D.O., Adeleke, M.A.,
Gyang, P.V. and Dike, A.A. Prevalence of
urinary Schistosomiasis in Umuowele
Village, Agulu, Anambra State, Nigeria.
International Journal of Health Research,
2(4): 347-353 (2009).
17. Ekwunife, C.A., Ozumba, N.A., and
Eneanya, C.I. Studies on the biology and
population parameters of Bulinus globosus
and Bulinus truncatus in the laboratory.
Nigeria Journal of Parasitology, 29(1): 11-
14 (2008).
18. Ekpo, U.F., Hurliman, E., Schur, N.,
Oluwole, A.S., Abe, E.M., Mafa, M.A.,
Nebe, O. J., Isiyaku, S., Olamiju, F.,
Kristensen, T. K., Utzinger. J. and
Penelope, V. Mapping and prediction of
Schistosomiasis in Nigeria using compiled
survey data and Bayesian geospatial
modelling. Geospatial Health, 7(2): 355-
366 (2013).
19. Idris, H.S. and Ajanusi, O.J. Snail
intermediate hosts and etiology of human
Schistosomiasis in Kastina State, Nigeria.
Ikpeze and Obikwelu Int. J. Pure App. Biosci. 4 (2): 91-102 (2016) ISSN: 2320 – 7051
Copyright © April, 2016; IJPAB 101
Nigerian Journal of Parasitology, 23: 145-
152 (2002).
20. Njoku-Tony, R.F. Effects of some physical
and chemical parameters on abundance of
intermediate snails of animal trematodes in
Imo state, Nigeria. Researcher, 3(4): 5-8
(2011).
21. Ofoezie, I.E. Distribution of freshwater
snails in the Man-made Oyan Reservoir,
Ogun State, Nigeria. Hydrobiologia, 416:
181-191 (1999).
22. Mohamed, A.H., Ahmad, A.M. and Heba,
M.F. Population dynamics of freshwater
snails (Mollusca: Gastropoda) at Qena
Governorate, Upper Egypt. Acad. J. Biolog.
Sci., 3(1): 11-22 (2011).
23. Owojori, O.J., Asaolu, S.O. and Ofoezie,
I.E. Ecology of freshwater snails in Opa
Reservoir and Research Farm Ponds at
Obafemi Awolowo University Ile-Ife,
Nigeria. Journal of Applied Sciences,
6(15): 3004-3015 (2006a).
24. Okafor, F.C. and Ngang, I. Freshwater
snails of Niger-Cem Nkalagu, Eastern
Nigeria: Observations on some
demographic aspects of the Schistosome
transmitting Bulinids. Animal Research
International, 1(2): 120-124 (2004).
25. Ekpo, U.F. and Mafiana, C.F.
Epidemiological studies of urinary
Schistosomiasis in Ogun State, Nigeria:
Identification of high communities.
Nigerian Journal of Parasitology, 25: 111-
119 (2004).
26. Omudu, E.D. and Iyough, A. Ecological
studies of the gastropod fauna of some
minor tributaries of River Benue in
Makurdi, Nigeria. Animal Research
International, 2(2): 306-310 (2005).
27. Okafor, F.C. Distribution of freshwater
gastropods in the Lower River Niger and
Cross River basins of South-eastern Nigeria
with reference to their trematodes
infections. Beitr. Trop. Landwirch
Veterinaries, 28(2): 207-216 (1990).
28. Agi, P.I. and Okwuosa, V.N. Aspect of
water quality of freshwater systems
habouring snail vectors of Schistosome
parasites in Jos, Nigeria. Journal of Aquatic
Sciences, 16:3-17 (2001).
29. Oguoma, V.M., Ugorji, N.D., Okolo, K.V.,
Mbanefo, E.C. and Umeh, J.M. Aquatic
snails’ species of two adjoining rivers in
Owerri, Imo State, South eastern Nigeria.
Animal Research International, 7(1): 1125-
1128 (2010).
30. Duggan, I.C. First record of a wild
population of the tropical snail Melanoides
tuberculatus in New Zealand natural
waters. New Zealand Journal of Marine
and Freshwater Research, 36: 825-829
(2002).
31. Pointier, J.P., Samadi, S., Jame, P. and
Delay, B. Introduction and spread of Thiara
granifera (Lamarck, 1822) in Martinique,
French West Indies. Biodiversity and
Conservation, 7: 1277-1290 (1998).
32. Barbosa, F.S and Barbosa, C.S. The bio-
ecology of snail vector for Schistosomiasis
in Brazil. Cad. Saude publ. Rio de Janeiro,
10(2): 200-209 (1994).
33. Appleton, C.C.. Review Literature on biotic
factors that influence the distribution and
life cycles of bilharziasis intermediate host
snails. Malacol. Rev. 11:1-25 (1978).
34. Woodhouse, M.E.J. and Chandiwana, S.K.
Spatial and temporal heterogeneity in the
population dynamics of Bulinus globosus
and Biomphalaria pfeifferi and in the
epidemiology of their infection with
Schistosomiasis. Parasitology, 98: 21-34
(1989).
35. Belot, J., Geerts, S. and Diouf, M.
Observation on the population dynamics of
snail hosts for Schistosomiasis in the delta
of Senegal River basin. Journal of
Molluscan Studies, 59: 7-13 (1993).
36. Ndifon, G.T. and Ukoli, F.M.A. Ecology of
freshwater snails in south-western Nigeria:
Distribution and Habitat preferences.
Hydrobiologia, 171: 231-253 (1989).
37. Badger-Emeka, L.I. Studies on seasonal
variation in the gut contents of snail
intermediate hosts of Schistosomes in Kano
State of Nigeria. Nigerian Journal of
Parasitology, 27: 49-53 (2006).
38. Madsen, H. Food selection by freshwater
snails in Gezira irrigation canals, Sudan.
Hydrobiologia, 228: 203-217 (1992a).
Ikpeze and Obikwelu Int. J. Pure App. Biosci. 4 (2): 91-102 (2016) ISSN: 2320 – 7051
Copyright © April, 2016; IJPAB 102
39. Odum, E.P. Fundamentals of Ecology. 3
rd
Edition, Saunders Company. 574 pp
(1971).
40. Wilcocks, C. and Manson-Bar, P.E.C.
Trematodes infections; Schistosomiasis. In:
The English Language Book Society and
Bailliere Tindall (eds.), Manson’s Tropical
Diseases. Henrietta, London: Whitefriars
Press Limited, London and Tonbridge, pp.
285-311 (1972).
41. Pointier, J.P., Incani, R.N., Balzan, C.
Chrosciechowski, P. Inversion of the rivers
of the littoral central region of Venezuela
by Thiara granifera and Melanoides
tuberculatus (Mollusca: Prosobranchia:
Thiaridae) and the absence of
Biomphalaria grabrata, snail host of
Schistosoma mansoni. The Nautilus, 124-
128 (1994).
42. Livshit, G. and Fischlson, L. Biology and
reproduction of the freshwater snail
Melanoides tuberculatus (Gastropoda:
Prosobranchia) in Israel. Israel Journal of
Zoology, 32: 21-35 (1983).
43. Akin-Oriola, G.A. On the phytoplankton of
Awba reservoir, Ibadan, Nigeria. Revista de
Biologia Tropical, 51(1) (2003).
44. Mustapha, M.K. and Omotosho, J.S. An
assessment of the physico-chemical
properties of Moro Lake, Kwara State,
Nigeria. African Journal of Applied
Zoology and Environmental Biology, 7: 73-
77 (2005).
45. Owojori, O.J., Asaolu, S.O. and Ofoezie,
I.E. Schistosomiasis: water contact patterns
and snail infection rates in Opa Reservoir
and Research Farm Pond in Obafemi
Awolowo University, Ile Ife, Nigeria.
International Journal of Zoological
Research, 2: 323-33 (2006b).
46. Onyema, I.C. and Nwankwo, D.I. The
epidemic assemblage of a polluted
estuarine creek in Lagos, Nigeria. Poll. Res,
25(3): 459 – 468 (2006).
47. Edokpayi, C.A. Variation in chemical
constituents of a brackish water prawn
habitat in Southern Nigeria. Acta SATECH.
2(1): 11-18 (2005).
48. Maqbool, A., Hayat. C.S., Tanveer, A.,
Salahuddin, M. and Arfan, A. Prevalence
and Ecology of Lymnaea snails in Punjub.
Iranian Journal of Veterinary Research, 8:
192-195 (2003).
49. Karimi, G.R., Derakhshanfar, M. and
Paykari, H. Population density, trematodal
infection and ecology of Lymnaea snails in
Shadegan, Iran. Arch Razi Ins., 58: 125-129
(2004).
50. Eyo, J.E., Odoh, G.E. and Achife, A.
Variations in the physico-chemical
parameter of a natural Tropical Rainforest
Lake. Bio-Research, 6(2): 371-374 (2008).
51. Nwosu, M.C., Nsofor, C.I. and Okeke J.J.
Studies on the Ichthyofaunal Assemblages
of some natural lakes in Anambra State,
Nigeria. Natural and Applied Sciences
Journal(www.naasjournal-ng.org.),10(2):
(2009).
52. Canete, R., Yong, M., Sanchez, J., Wong,
L. and Gutierrez, A. Population dynamics
of intermediate snail hosts of Fasciola
hepatica and some environmental factors in
San Juan Martinez. Municipality, Cuba.
Mem. Inst. Oswaldo Cruz, Rio de Janeiro,
99(3): 257-262 (2004).
