4.1. Cu Is the Most Toxic Metal
The results showed that the mortality of the snails increased as they were exposed to increasing concentrations of metals or for longer durations. Cu was the most toxic metal. The snails were most susceptible to Cu with the lowest LC
50 values compared to other metals. Comparing the LC
50 values of Cd and Cu for
P. insularum with those of other snail species (>10 species), including mussels, clams, sea anemones, cockles and shrimp, revealed that
P. insularum was more sensitive to Cu than Cd, Ni, Pb and Zn. This is well indicated in the different species of bivalves and gastropods from the literature (
Table 2,
Table 3,
Table 4,
Table 5 and
Table 6).
Even though juvenile snails were more sensitive to the five metals, Cu was shown to be the most toxic metal for both juvenile and adult snails, when compared to Ni, Pb, Cd and Zn. This is consistently correlative with research on the toxicity of heavy metals to freshwater organisms. For instance, the rank order of toxicity of some heavy metals to
Daphnia magna was Cu > Zn > Cd > Pb > Ni (48 h) [
35]; for rainbow trout (
Salmo gairdneri) it was Cu > Zn > Cd > Pb > Ni (96 h) [
35]; for amphibian tad-poles (
Bufo melanostictus) it was Cu > Cd > Zn > Ni (96 h) [
36]; and for
Lymnaea luteola it was Cu > Cd > Ni > Zn (72 h) [
28].
The findings of the present study showed that the LC
50 values in the five metals significantly decreased (
p < 0.05) from 48-h to 72-h periods in both juvenile and adult snails. This indicated that the longer period of toxicity testing resulted in the snails being more sensitive to the five metal toxicities. Taylor et al. [
37] reported that the LC
50 values of Cu in
Gammarus pulex decreased from 0.047 to 0.037 after 48-h and 96-h periods, respectively. Similarly, they also found that the LC
50 values of Cu in
Chironomus riparius decreased from 1.20 to 0.70 after 48- and 96-h periods, respectively. Using
P. canaliculata as the test organism, Dummee et al. [
38] demonstrated that the LC
50 values of Cu exposure periods of 4, 48, 72 and 96 h were 0.330, 0.223, 0.177 and 0.146 mg/L, respectively. This indicates a decreasing order of LC
50 values with increasing Cu exposure period. All of these data demonstrated that the longer the duration of exposure, the more sensitive the invertebrates to pollutants.
Brix et al. [
39] showed that the 96-h LC
50 value of Cu in
Lymnaea stagnalis was 31 g/L, indicating a moderate acute sensitivity to Cu. However, the projected EC
20 value (the median effective concentration of a substance to 20% of test organisms) for Cu after a 30-day chronic exposure of juvenile
L. stagnalis to Cu was 1.8 mg/L, making it the most sensitive organism to Cu investigated to date. In a different experiment with adult freshwater snails,
Melanoides tuberculata, Shuhaimi-Othman et al. [
9] observed an increase in the median lethal times (LT
50) and concentrations (LC
50) of eight metals after four days of laboratory exposure. Cu was the most hazardous metal to
M. tuberculosis, followed by Cd, Zn, Pb, Ni, Fe, Mn and Al.
Several investigations suggested that
Pomacea snails were efficient bioindicators for Cu and Cd.
Pomacea canaliculata has the capacity to acquire Cu from a variety of metals (20, 30, 45, 67.5 and 101.3 mg/L), but demonstrated behavioral control at Cu concentrations of 67.5 and 101.3 mg/L, as determined by Pena and Pocsidio [
40]. This provided evidence for using the golden apple snail (whole tissue analysis) as a sublethal Cu biomonitor (0–45 mg/L). Additionally, Manzla et al. [
41] reported acute toxicity of Cu and Cd on the hepatopancreas cells of
Helix pomatia (toxicity of Cu > Cd). Hoang and Rand [
42] showed that CuCO
3 was toxic to apple snails (
Pomacea paludosa) due to the fact that Cu concentrations were higher in living snails than in dead snails. Their results indicated that apple snails could excrete deposited Cu [
38]. They demonstrated that
Pomacea was a suitable bioindicator and biomarker for Cu pollution biomonitoring in aquatic environments. Habib et al. [
43] showed that
B. alexandrina was a suitable organism for assessing Cd toxicity in freshwater environments based on short-term 96-h (LC
50) and long-term exposure to Cd.
The outcomes of the present study indicated that both the smaller and bigger snail populations displayed the same decreasing order of metal toxicity: Cu > Cd. The order of toxicity of these metal ions correlates well with the metal toxicity levels of other freshwater organisms. For amphibian tadpoles [
36],
Daphnia magna [
35] and pulmonate snails [
44], Cu was more poisonous than Cd.
In understanding the toxicity of Cu, Hoang and Rand [
42] indicated that the carbonate content of snails may explain the potential toxicity of Cu carbonate to snails. This is because snails need carbonate for shell growth; their carbonate need is greater than that of fish. Cu carbonate may enter snails as Cu, and dissociate after entering the snails by biological and chemical processes. Carbonate would be accessible for shell formation, while Cu would accumulate in soft tissue. Hoang et al. [
45] also showed that the majority of deposited Cu in juvenile apple snails (
Pomacea paludosa) was concentrated in soft tissue (about 60% in the viscera and 40% in the foot), and the shell contained less than 4% of the total accumulated Cu. Nevertheless, a comparison of the absorption rate in aquatic organisms revealed that, generally, the uptake rate constant is Zn > Cd > Cu [
46]. This gap is likely related to the four-day metal exposure duration in this investigation. Other factors that may influence the bioaccumulation of heavy metals in aquatic organisms include feeding habits [
47], growth rate and age of the organism [
5], and the bioavailability of the metals, which is highly dependent on water hardness, pH and acid-volatile sulfide [
48]. Hoang and Rand [
42] demonstrated that apple snails (
Pomacea paludosa) accumulated more Cu from soil-water treatments than water-only treatments, implying that apple snails accumulate Cu from environmental media (sediment or water). The rate of increase in the weight of a snail’s tissue and shell is typically greater than the rate of accumulation of metals in its body. Lau et al. [
5] and Hoang et al. [
45] showed that juvenile apple snails collected Cu during the exposure period and excreted Cu during the depuration phase. Metals accumulated in animals can be stored without excretion, leading to high body concentrations (accumulators), or the metal levels in the body can be maintained at a low constant concentration (regulators) by balancing the uptake with controlled excretion rates [
49].
4.2. Juvenile Snails Are More Sensitive to Metal Toxicity
Smaller snails (0.50 to 0.70 cm) were shown to be more sensitive and less tolerant to all metals (Cd, Cu, Ni, Pb and Zn) than larger snails (1.50–2.20 cm). Previous research has demonstrated that younger organisms are more susceptible to toxicity [
50,
51]. In a study on mussels, Yap et al. [
51] demonstrated that the species was most susceptible to Cu, followed by Cd; however, the small size group was more sensitive than the large size group, as the small group had lower LC
50 values. In addition, it should be emphasized that other environmental variables, such as water quality, might influence the toxicity of a metal [
52], and, therefore, can contribute to discrepancies in reported results. Although a standard test on a single species may provide information on the environmental risks of a toxicant, one should not establish safe environmental levels for toxicants based on a small number of test species. As the tolerance of
Pomacea to metals was influenced by chemical type and test duration, it is imperative that the toxicity test encompasses a wider range of species and exposure times in future studies.
If other aspects of the snail’s life cycle had been researched, more information about its sensitivity to heavy metals would have been available. Wier and Walter [
30] found that immature
Physa gyrina snails were three times more vulnerable to heavy metals than their mature counterparts. Cheung and Lam [
53] showed that the juvenile stage of
Physa acuta freshwater snails was the most Cd-tolerant when compared to the embryo. Earlier life stages, such as embryos and larvae, were the most vulnerable to heavy metals, according to multiple investigations [
54,
55]. These results corroborated the present study’s conclusion that snails of a lower size range (0.50–0.70 cm) were more vulnerable to all metals than snails of a larger size range (1.50–2.20 cm) (Cu, Ni, Pb, Zn and Cd). The juvenile stage was found to be more vulnerable to heavy metals than the later stages.
4.3. Comparisons of LC50 Values with Those of Other Species of Molluscs
It is difficult to compare the LC
50 values of metals in this species with those in other gastropod species due to the varying ability of closely related taxa or species belonging to the same genus that inhabit the same environments to accumulate metals in water with varying hardness. Using adult
Theodoxus niloticus snails, Abdel Gawad [
7] reported the 96-h LC
50 values for Zn, Fe, and Pb to be 12.199, 8.6 and 18 mg/L, respectively. These values grew as the duration of exposure decreased. Fe was the most hazardous element to the snail, followed by Zn and Pb.
The findings of this investigation on the sensitivity of
P. insularum to the toxicity of heavy metals supported the notion that the susceptibility of an animal to heavy metal toxicity differed among species [
55,
56,
57,
58]. This is demonstrated by comparing the LC
50 values of
P. insularum to those of other species. For example, Arthur and Leonard [
59] reported that the 96-h LC
50 of Cu in
Physa integra was 0.039 mg/L, which is lower than the 96-h LC
50 in
P. insularum in the present study, which was 0.21 mg/L of Cu. The variation may be due to the various test animal species, techniques, and environmental conditions. Throp and Lake [
60] reported that the 96-h LC
50 values of Cd in the freshwater shrimp
Paratya tasmaniensis were 0.06 mg/L. However, in the present investigation, the 96-h LC
50 values of Cd in
P. insularum were 2.55 mg/L. In addition, Lam [
61] reported that the 96-h LC
50 values of the tropical freshwater snail
Radix plicatulus were 2.55 mg/L of Cd, which was comparable to the 72-h LC
50 values of Cd in juvenile
P. insularum (2.15 mg/L) in the present study. Consequently, based on the preceding examples, it can be concluded that the susceptibility of different species [
62] and several factors such as experiment procedures, the physical and chemical characteristics of the experimental conditions such as temperature, DO, pH and water hardness [
63], as well as the physiological, size, and age of the animals used, can influence the LC
50 values in the toxicity study.
Multiple researchers have investigated the impact of environmental characteristics such as temperature, pH, and dissolved oxygen on the toxicity of heavy metals and published their findings in the scientific literature. In general, increasing respiration at higher temperatures directly increased toxicity. Moreover, high temperatures indirectly increase toxicity by reducing oxygen levels in water [
64]. Temperature increases had a direct effect on the ramshorn snail,
Helisoma campanulatum, and the pond snail,
Viviparus benghalensis, according to Gupta et al. [
65]. Eisler [
58] also showed that at 20 °C, the mummichog was more vulnerable to Cd than at 5 °C. In contrast, it is well established that increased water hardness reduces the acute toxicity of metals [
66]. However, as the temperature utilized in the present exposure investigation was constant, this abiotic parameter had no effect on the snails’ toxicity and tolerance to heavy metals.
Cu is more hazardous than Zn and Hg to the two intertidal snails
Planaxis sulcatus and
Trochus radiatus, according to an acute toxicity test performed by Kulkarni et al. [
67] using static bioassay procedures. The availability of heavy metals due to different anthropogenic metal inputs could be attributed to their metal toxicities [
68].
For all metals, Shuhaimi-Othman et al. [
9] found that (LC
50 increased with decreasing mean exposure concentrations and periods. Cu was discovered to be the most hazardous metal to
M. tuberculosis, followed by Cd, Zn, Pb and Ni. Other studies demonstrated divergent patterns in the toxicity of certain snails. According to Luoma and Rainbow [
40], the rank order of metal toxicity varies among organisms; Khangarot and Ray [
28,
29,
30] demonstrated that the order of toxicity was Cd > Ni > Zn in
Lymnaea luteola,; Gupta et al. [
69] and Gadkari and Marathe [
70] showed that the order of toxicity was Zn > Cd > Pb > Ni in
Viviparus bengalensis.
According to Shuhaimi-Othman et al. [
9], the LC
50 values of Cu, Cd, Zn, Pb and Ni for 48 and 96 h were 0.39, 11.85, 13.15, 10.99 and 36.46 mg/L, and 0.14, 1.49, 3.90, 6.82 and 8.46 mg/L, respectively. Metals’ acute toxicity to
M. tuberculosis was the subject of only a few studies. Nebeker et al. [
71] showed that the 96-h LC
50 value of Cu in
Fluminicola virens was 0.08 mg/L, and that of Zn in
Physa gyrina was 1.27 mg/L, which were lower than those reported by Shuhaimi-Othman et al. [
9]. Bali et al. [
72] and Mostafa et al. [
73] reported 96-h LC
50 values of Cu in
M. tuberculosis were 0.2 and 3.6 mg/L, respectively, which were greater than those reported by Shuhaimi-Othman et al. [
9].
Abdel Gawad [
74] investigated the effect of different doses of Cd on the toxicity of
Corbicula fluminalis. The 96-h LC
50 and daily survival rates were evaluated to determine the acute toxicity. Their results indicated that the
C. fluminalis mortality rate was proportional to the Cd concentration. After 96 h of exposure, the LC
50 was 0.52 mg/L. After 96 h of exposure, the bioaccumulation value of the pollutant in the soft portions of the clam was greater than the comparable value in the shell.
Shuhaimi-Othman et al. [
9] showed that the LC
50 values in
M. tuberculata were generally lower or comparable to those of other freshwater gastropods. It was difficult to make direct comparisons between the toxicity values found in this study and those in the literature due to changes in the test waters’ properties (mainly water hardness, pH, and temperature). Different species, ages, and sizes of the organisms as well as different test methods (water quality and water hardness) can influence toxicity [
50,
75,
76,
77,
78]. In the present investigation, the water hardness was low (18.7 mg/L CaCO
3), and the water was classified as soft (75 mg/L as CaCO
3).
The snail
M. tuberculata was found to be less sensitive to metals compared to other species [
9]. Von Der Ohe and Liess [
79] demonstrated that 13 Crustacea taxa were among the most sensitive to metal compounds, and they concluded that Crustacea taxa are comparable to one another and to
Daphnia magna in terms of sensitivity to organics and metals, and that mollusks have an average sensitivity to metals. Mitchell et al. [
80] observed that the snail has a tightly sealed operculum, which enables it to tolerate desiccation and, presumably, also boosts its chemical tolerance.
Table 2.
Comparison of LC50 values (mg/L) of Cd in Pomacea insularum with other mollusks reported in the literature.
Table 2.
Comparison of LC50 values (mg/L) of Cd in Pomacea insularum with other mollusks reported in the literature.
Molluscs | Species | Water Hardness (mg L−1) | Live Stage | Test Duration | LC50 (mg/L) | References |
---|
Bivalves | Donax faba | 29.9 ppt | Adult | 96-h EC50 | 0.99 | Din and Ong [81] |
| Anadara granosa | 29.5 ppt | Adult | 96-h EC50 | 0.94 | Din and Ong [81] |
| Perna viridis | NA | NA | 24-h EC50 | 1.53 | Yap et al. [45] |
| Modiolus phillippinarum | NA | NA | 96-h EC50 | 0.02 | Ramakristinan et al. [82] |
Gastropods | Lymnaea luteola | 195 | Adult | 48-h EC50 | 2.10 | Khangarot and Ray [28] |
| Amnicola sp. | 50 | Adult | 96-h EC50 | 8.40 | Rehwoldt et al. [83] |
| Biomphalaria glabrata | 100 | NA | 96-h EC50 | 0.30 | Bellavere and Gorbi [84] |
| Viviparus bengalensis | 180 | NA | 96-h EC50 | 1.20 | Gupta et al. (1981a) [69] |
| Viviparus bengalensis | NA | NA | NA | 2.54 | Gadkari and Marathe [70] |
| Aplexa hypnorum | 45 | Adult | 96-h EC50 | 0.09 | Holcombe et al. [85] |
| Physa fontinalis | NA | NA | 96-h EC50 | 0.08 | Williams et al. [86] |
| Radix plicatulus | NA | NA | 96-h EC50 | 2.50 | Lam [62] |
| Lymnaea luteola | 195 | Adult | 72-h EC50 | 1.60 | Khangarot and Ray [28] |
| Lymnaea luteola | 195 | Adult | 96-h EC50 | 1.52 | Khangarot and Ray [28] |
| Physa acuta | NA | NA | 48-h EC50 | 1.05 | Cheung and Lam [48] |
| Potamopygus antipodarum | NA | NA | 96-h EC50 | 0.72 | Hall and Golding [87] |
| Pomacea sp. | NA | NA | 24-h EC50 | 2.25 | Piyatiratitivorakul et al. [88] |
| Pomacea sp. | NA | NA | 48-h EC50 | 2.07 | Piyatiratitivorakul et al. [88] |
| Pomacea sp. | NA | NA | 72-h EC50 | 0.68 | Piyatiratitivorakul et al. [88] |
| Pomacea sp. | NA | NA | 96-h EC50 | 0.47 | Piyatiratitivorakul et al. [88] |
| Filopaludina martensi martensi | NA | NA | 24-h EC50 | 27.8 | Piyatiratitivorakul and Boonchamoi [54] |
| Filopaludina martensi martensi | NA | NA | 48-h EC50 | 5.01 | Piyatiratitivorakul and Boonchamoi [54] |
| Filopaludina martensi martensi | NA | NA | 72-h EC50 | 3.96 | Piyatiratitivorakul and Boonchamoi [54] |
| Filopaludina martensi martensi | NA | NA | 96-h EC50 | 2.33 | Piyatiratitivorakul and Boonchamoi [54] |
| Melanoides tuberculata | 18.7 | Adult | 96-h EC50 | 1.49 | Shuhaimi-Othman et al. [9] |
| Cerithedia cingulata | NA | NA | 96-h EC50 | 9.19 | Ramakristinan et al. [82] |
| Biomphalaria alexandrina | NA | NA | 96-h EC50 | 0.22 | Habib et al. [43] |
| Pomacea canaliculata | NA | NA | 48-h EC50 | 4.26 | Huang et al. [89] |
| Pomacea canaliculata | NA | NA | 72-h EC50 | 2.24 | Huang et al. [89] |
| Pomacea canaliculata | NA | NA | 96-h EC50 | 1.98 | Huang et al. [89] |
| Pomacea insularum (small) | 65 | Juvenile | 48-h EC50 | 3.67 | This study |
| Pomacea insularum (small) | 65 | Juvenile | 72-h EC50 | 2.15 | This study |
| Pomacea insularum (large) | 65 | Adult | 48-h EC50 | 24.73 | This study |
| Pomacea insularum (large) | 65 | Adult | 72-h EC50 | 11.7 | This study |
Table 3.
Comparison of LC50 values (mg/L) of Cu in Pomacea insularum with other mollusks reported in the literature.
Table 3.
Comparison of LC50 values (mg/L) of Cu in Pomacea insularum with other mollusks reported in the literature.
Molluscs | Species | Water Hardness (mg/L) | Live Stage | Test Duration | LC50 (mg/L) | References |
---|
Bivalves | Clam Donax faba | NA | NA | 96-h EC50 | 0.93 | Sommanee [90] |
| Donax faba | 29.9 ppt | Adult | 96-h EC50 | 0.20 | Din and Ong [81] |
| Anadara granosa | 29.5 ppt | Adult | 96-h EC50 | 0.23 | Din and Ong [81] |
| Perna viridis | NA | NA | 24-h EC50 | 0.25 | Yap et al. [45] |
| Anadara granosa | NA | NA | 48-h EC50 | 0.29 | Yap et al. [91] |
| Modiolus phillippinarum | NA | NA | 96-h EC50 | 0.22 | Ramakristinan et al. [82] |
Gastropods | Biomphalaria glabrata | 100 | NA | 96-h EC50 | 0.04 | Bellavere and Gorbi [84] |
| Viviparus bengalensis (at 27.3 C) | 180 | NA | 48-h EC50 | 0.27 | Gupta et al. [66] |
| Viviparus bengalensis (at 27.3 C) | NA | NA | 72-h EC50 | 0.12 | Gupta et al. [66] |
| Lymnaea luteola | NA | NA | 96-h EC50 | 0.172 | Mathur et al. [92] |
| Physastra gibbosa | NA | NA | 96-h EC50 | 0.041 | Skidmore and Firth [93] |
| Melanoides tuberculata | NA | Juvenile | 24-h EC50 | 0.20 | Bali et al. [72] |
| Potamopyrgus jenkinsi | NA | Adult | 96-h EC50 | 0.08 | Watton and Hawkes [94] |
| Lithoglyphus virens | 21 | Adult | 96-h EC50 | 0.08 | Nebeker et al. [71] |
| Juga plicifera | 21 | Adult | 96-h EC50 | 0.015 | Nebeker et al. [71] |
| Lymnaea luteola | 195 | Adult | 48-h EC50 | 0.025 | Khangarot and Ray [28] |
| Lymnaea luteola | 195 | Adult | 72-h EC50 | 0.027 | Khangarot and Ray [28] |
| Lymnaea luteola | 195 | Adult | 96-h EC50 | 0.027 | Khangarot and Ray [28] |
| Biomphalaria glabrata | 44 | Adult | 48-h EC50 | 0.18 | De Oliveira-Filho et al. [95] |
| Melanoides tuberculata | NA | NA | 48-h EC50 | 3.60 | Mostafa et al. [73] |
| Pomacea sp. | NA | NA | 24-h EC50 | 4.84 | Piyatiratitivorakul et al. [88] |
| Pomacea sp. | NA | NA | 48-h EC50 | 1.85 | Piyatiratitivorakul et al. [88] |
| Pomacea sp. | NA | NA | 72-h EC50 | 0.92 | Piyatiratitivorakul et al. [88] |
| Pomacea sp. | NA | NA | 96-h EC50 | 0.12 | Piyatiratitivorakul et al. [88] |
| Pomacea paludosa | 68 | 60 d | 96-h EC50 | 0.14 | Rogevich et al. [96] |
| Melanoides tuberculata | 18.7 | Adult | 96-h EC50 | 0.14 | Shuhaimi-Othman et al. [9] |
| Cerithedia cingulata | NA | NA | 96-h EC50 | 0.52 | Ramakristinan et al. [82] |
| Pomacea canaliculata | NA | NA | 24-h EC50 | 0.33 | Dummee et al. [32] |
| Pomacea canaliculata | NA | NA | 48-h EC50 | 0.22 | Dummee et al. [32] |
| Pomacea canaliculata | NA | NA | 72-h EC50 | 0.18 | Dummee et al. [32] |
| Pomacea canaliculata | NA | NA | 96-h EC50 | 0.15 | Dummee et al. [32] |
| Pomacea insularum (small) | 65 | Juvenile | 48-h EC50 | 0.94 | This study |
| Pomacea insularum (small) | 65 | Juvenile | 72-h EC50 | 0.50 | This study |
| Pomacea insularum (large) | 65 | Adult | 48-h EC50 | 3.10 | This study |
| Pomacea insularum (large) | 65 | Adult | 72-h EC50 | 1.84 | This study |
Table 4.
Comparison of LC50 values (mg/L) of Ni in Pomacea insularum with other mollusks reported in the literature.
Table 4.
Comparison of LC50 values (mg/L) of Ni in Pomacea insularum with other mollusks reported in the literature.
Molluscs | Species | Water Hardness (mg/L) | Live Stage | Test Duration | LC50 (mg/L) | References |
---|
Bivalves | Utterbackia imbecillis | 60 | Juveniles | 96-h EC50 | 0.19 | Keller and Lam [97] |
| Utterbackia imbecillis | 80 | Juveniles | 96-h EC50 | 0.252 | Keller and Lam [97] |
| Hamiota perovalis | 43 | Juveniles | 96-h EC50 | 0.313 | Gibson et al. [98] |
| Villosa nebulosa | 43 | Juveniles | 96-h EC50 | 0.51 | Gibson et al. [98] |
Gastropods | Amnicola sp. | 50 | Embryo | 96-h EC50 | 11.4 | Rehwodlt et al. [83] |
| Amnicola sp. | 50 | Adult | 96-h EC50 | 14.3 | Rehwodlt et al. [83] |
| Viviparus bengalensis | 180 | NA | 96-h EC50 | 9.92 | Gupta et al. [69] |
| L. acuminata | 375 | NA | 96-h EC50 | 2.78 | Khangarot et al. [99] |
| Lymnaea stagnalis | 100 | Juveniles | 96-h EC50 | 0.9 | Nebeker et al. [71] |
| Physa gyrina | 26 | NR | 96-h EC50 | 0.239 | Nebeker et al. [71] |
| L. luteola | 195 | Adult | 48-h EC50 | 1.7 | Khangarot and Ray [28] |
| L. luteola | 195 | Adult | 72-h EC50 | 1.7 | Khangarot and Ray [28] |
| L. luteola | 195 | Adult | 96-h EC50 | 1.43 | Khangarot and Ray [28] |
| Melanoides tuberculata | 18.7 | Adult | 96-h EC50 | 8.46 | Shuhaimi-Othman et al. [9] |
| Leptoxis ampla | 43 | Juveniles | 96-h EC50 | 0.033 | Gibson et al. [98] |
| Somatogyrus sp. | 43 | Adult | 96-h EC50 | 0.301 | Gibson et al. [98] |
| Pomacea insularum (small) | 65 | Juvenile | 48-h EC50 | 4.77 | This study |
| Pomacea insularum (small) | 65 | Juvenile | 72-h EC50 | 3.01 | This study |
| Pomacea insularum (large) | 65 | Adult | 48-h EC50 | 10.73 | This study |
| Pomacea insularum (large) | 65 | Adult | 72-h EC50 | 6.88 | This study |
Table 5.
Comparison of LC50 values (mg/L) of Pb in Pomacea insularum with other mollusks reported in the literature.
Table 5.
Comparison of LC50 values (mg/L) of Pb in Pomacea insularum with other mollusks reported in the literature.
Molluscs | Species | Water Hardness (mg/L) | Live Stage | Test Duration | LC50 (mg/L) | References |
---|
Bivalve | Mussel Modiolus phillippinarum | NA | NA | 96-h EC50 | 2.88 | Ramakristinan et al. [82] |
Gastropods | A. hypnorum | 60.9 | NA | 96-h EC50 | 1.34 | Call et al. [100] |
| Viviparus bengalensis | 165 | NA | 96-h EC50 | 2.54 | Gadkari and Marathe [70] |
| L. emarginata | 150 | NA | 96-h EC50 | 14 | Cairns Jr et al. [101] |
| E. livescens | 150 | NA | 96-h EC50 | 71 | Cairns Jr et al. [101] |
| Filopaludina sp. | NA | Adult | 24-h EC50 | 319 | Jantataeme et al. [102] |
| Filopaludina sp. | NA | Adult | 48-h EC50 | 271 | Jantataeme et al. [102] |
| Filopaludina sp. | NA | Adult | 72-h EC50 | 235 | Jantataeme et al. [102] |
| Filopaludina sp. | NA | Adult | 96-h EC50 | 192 | Jantataeme et al. [102] |
| Melanoides tuberculata | 18.7 | Adult | 96-h EC50 | 6.82 | Shuhaimi-Othman et al. [9] |
| Snail Cerithedia cingulata | NA | NA | 96-h EC50 | 15.5 | Ramakristinan et al. [82] |
| Freshwater snail Theodoxus niloticus | NA | Adult | 96-h EC50 | 18 | Abdel Gawad et al. [7] |
| Archachatina papyracea | Land snails | Adults | 28-days EC50 | 1121 | Owojori et al. [103] |
| Pomacea insularum (small) | 65 | Juvenile | 48-h EC50 | 10.44 | This study |
| Pomacea insularum (small) | 65 | Juvenile | 72-h EC50 | 8.35 | This study |
| Pomacea insularum (large) | 65 | Adult | 48-h EC50 | 17.24 | This study |
| Pomacea insularum (large) | 65 | Adult | 72-h EC50 | 11.45 | This study |
Table 6.
Comparison of LC50 values (mg/L) of Zn in Pomacea insularum with other mollusks reported in the literature.
Table 6.
Comparison of LC50 values (mg/L) of Zn in Pomacea insularum with other mollusks reported in the literature.
Molluscs | Species | Water Hardness (mg/L) | Live Stage | Test Duration | LC50 (mg/L) | References |
---|
Bivalves | Corbicula fluminea | 64 | NA | 96-h EC50 | 6.04 | Cherry et al. [104] |
| Actinonaias pectorosa | 170 | Glochidia | 96-h EC50 | 0.31 | Cherry et al. [104] |
| Medionidus conradicus | 170 | Glochidia | 96-h EC50 | 0.57 | Cherry et al. [104] |
| Phychobranchus fasciolaris | 170 | Juveniles | 96-h EC50 | 0.21 | Cherry et al. [104] |
| Utterbackia imbecillis | 60 | Juveniles | 96-h EC50 | 0.27 | Keller and Lam [97] |
| Utterbackia imbecillis | 80 | Juveniles | 96-h EC50 | 0.44 | Keller and Lam [97] |
| Utterbackia imbecillis | 60 | Juveniles | 96-h EC50 | 0.36 | Keller and Lam [97] |
| Utterbackia imbecillis | 80 | Juveniles | 96-h EC50 | 0.59 | Keller and Lam [97] |
| Villosa nebulosa | 170 | Glochidia | 96-h EC50 | 0.66 | Cherry et al. [104] |
| Actinonaias pectorosa | 40 | Juveniles | 96-h EC50 | 0.36–0.37 | McCann [105] |
| Actinonaias pectorosa | 160 | Juveniles | 96-h EC50 | 1.06–1.19 | McCann [105] |
| Villosa iris | 50 | Juveniles | 96-h EC50 | 0.34 | McCann [105] |
| Villosa iris | 160 | Juveniles | 96-h EC50 | 1.12 | McCann [105] |
| Villosa umbrans | 43 | Juveniles | 96-h EC50 | 1.30 | Gibson et al. [98] |
| Villosa nebulosa | 43 | Juveniles | 96-h EC50 | 0.44 | Gibson et al. [98] |
| Donax faba | 29.9 ppt | Adult | 96-h EC50 | 3.61 | Din and Ong [81] |
| Anadara granosa | 29.5 ppt | Adult | 96-h EC50 | 7.76 | Din and Ong [81] |
| Modiolus phillippinarum | NA | NA | 96-h EC50 | 2.34 | Ramakristinan et al. [82] |
Gastropods | Helisoma campanulatum | 20 | Adult | 96-h EC50 | 0.87–1.27 | Wurtz [106] |
| Helisoma campanulatum | 100 | Adult | 96-h EC50 | 1.27–3.03 | Wurtz [106] |
| P. heterostropha | 20 | Adult | 96-h EC50 | 1.11 | Wurtz [106] |
| P. heterostropha | 100 | Adult | 96-h EC50 | 3.16 | Wurtz [106] |
| Physa heterostropha | 20 | Juveniles | 96-h EC50 | 0.30–1.39 | Wurtz [106] |
| Physa heterostropha | 100 | Juveniles | 96-h EC50 | 0.43–1.39 | Wurtz [106] |
| Amnicola sp. | 50 | Adult | 96-h EC50 | 14.0 | Rehwodlt et al. [83] |
| Amnicola sp. | 50 | Embryo | 96-h EC50 | 20.2 | Rehwodlt et al. [83] |
| Viviparus bengalensis | 180 | NA | 96-h EC50 | 0.64 | Gupta et al. [69] |
| Lymnaea luteola | NA | NA | 96-h EC50 | 6.13 | Mathur et al. [92] |
| L. acuminata | 375 | NA | 96-h EC50 | 10.5 | Khangarot et al. [99] |
| Physa gyrina | 36 | Adult | 96-h EC50 | 1.27 | Nebeker et al. [71] |
| Lymnaea luteola | 195 | Adult | 96-h EC50 | 11.0 | Khangarot and Ray [28] |
| Lymnaea luteola | 195 | Adult | 48-h EC50 | 3.80 | Khangarot and Ray [28] |
| Lymnaea luteola | 195 | Adult | 72-h EC50 | 3.80 | Khangarot and Ray [28] |
| Lymnaea luteola | 195 | Adult | 96-h EC50 | 1.68 | Khangarot and Ray [28] |
| Lanistes bolteni | NA | NA | NA | 58.0 | Abdel-Moati and Farag [8] |
| Melanoides tuberculata | 18.7 | Adult | 96-h EC50 | 3.90 | Shuhaimi-Othman et al. [9] |
| Cerithedia cingulata | NA | NA | 96-h EC50 | 8.99 | Ramakristinan et al. [82] |
| Leptoxis ampla | 43 | Adult | 96-h EC50 | 0.07 | Gibson et al. [98] |
| Somatogyrus sp. | 43 | Adult | 96-h EC50 | 0.33 | Gibson et al. [98] |
| Theodoxus niloticus | NA | Adult | 96-h EC50 | 12.2 | Abdel Gawad et al. [7] |
| Pomacea insularum (small) | 65 | Juvenile | 48-h EC50 | 30.16 | This study |
| Pomacea insularum (small) | 65 | Juvenile | 72-h EC50 | 11.36 | This study |
| Pomacea insularum (large) | 65 | Adult | 48-h EC50 | 57.99 | This study |
| Pomacea insularum (large) | 65 | Adult | 72-h EC50 | 26.97 | This study |
4.4. Implications from Biomonitoring Perspective
The use of small prosobranch snails, such as
P. insularum, as one of the biological indicators in toxicity testing, offers several benefits. First, because these snails are prevalent in still (ponds) and running (streams) waters, they can be utilized as ecologically significant target species in both lotic and lentic environments. Secondly, they are affordable, easily harvested and manageable. In addition, they are sensitive indicators of dangerous amounts of heavy metals such as Cu, Pb, Cd, Ni and Zn identified in this study, comparable to that reported by Ravera [
52] and Lam [
62]. They are possibly more susceptible to metals than larger snails,
Brotia hainanensis, because they possess the same trait [
107]. For a realistic approach to pollution consequences, additional research on the acute and chronic toxicity of various environmental contaminants under various environmental and biological circumstances is necessary. It is also necessary to assess the combined toxicity of substances. The mechanisms of contaminants at the cellular and molecular levels in these animals must also be comprehended.
Under controlled laboratory conditions, Pyatt et al. [
108] evaluated the effects of Pb (5 or 10 mg/L) on the survival of the freshwater snail
Lymnaea stagnalis (L.) collected from lead-contaminated or uncontaminated environments. Significantly more animals from the polluted environment survived subsequent acute (up to 24 days) Pb exposure than animals from the unpolluted environment. Acute exposure to Pb (72 h) hindered various behavioral activities, including movement, eating, tentacle elongation and emerging from the shell. Pb bioaccumulated in snail tissues, specifically the buccal mass and the stomach. The freshwater snail is an excellent system for researching the bioaccumulation and development of environmental Pb tolerance.
Nebeker et al. [
71] observed that three snail species from western Oregon were exposed to metals:
Juga plicifera and
Lithoglyphus virens, which occupy temperate coastal streams, and
Physa gyrina, which inhabits ponds in the Willamette Valley.
J. plicifera was subjected to Cu and Ni in laboratory flow-through testing, while
L. virens was exposed to Cu, and
P. gyrina was exposed to Ni and Zn.
J. plicifera had a 96-h LC
50 Cu value of 0.015 mg/L, and a no observable effect level (NOEL) of 0.006 mg/L (at which mortality was not substantially different from that in control groups) (30-d survival). The 96-h LC
50 and NOEL for Ni in
J. plicifera were 0.23 mg/L and 0.124 mg/L, respectively. The 96-h LC
50 and NOEL for Cu in
L. virens were 0.008 mg/L and less than 0.008 mg/L, respectively. The 96-h LC
50 for Ni in
P. gyrina was 0.239 mg/L, the 96-h LC
50 for Zn was 1.274 mg/L and the NOEL for Zn was 0.570 mg/L.
Piyatiratitivorakul et al. [
88] investigated the acute toxicity of Cd and Cu to
Pomacea sp collected from Thailand. The findings revealed the possibility of using the freshwater snail
Pomacea sp. as a biomonitor for heavy metal levels in freshwater resources. Huang et al. [
89] revealed the acute toxicity of Cd, in which the metal bioaccumulation in tissue was measured in
P. canaliculata and its native competitor
Sinotaia quadrata under experimental settings. The LC
50 concentrations (mg/L) for the invasive species were 4.26, 2.08 and 1.98 after being exposed for 48, 72 and 96 h, respectively, which were approximately three times greater than those of the native species. The viscera gathered the highest concentration of Cd, followed by the foot and shell in both species. The metal concentrations in the aforementioned three tissues of
P. canaliculata were significantly greater than those of
S. quadrata, regardless of Cd dose and exposure time. They concluded that a high Cd tolerance, may partially explain
P. canaliculata’s capacity to displace
S. quadrata from Cd-contaminated habitats. Cd primarily accumulated in the hepatopancreas and kidneys of invading species, thus altering the activity of antioxidant enzymes and helping the animals to deal with the toxicity.