Commentary

A good researcher usually specializes and enjoys a specific area of study. For example, the researcher is passionate to spend and devotes most of his/her time in studies like biomonitoring, ecology, ecotoxicology, genetics and plant crop improvements. The aim of this paper is to review Ecotoxicological Genetic (EG) study by using marine mussel Perna viridis under the Mussel Watch program and to discuss the potential EG o be applied to crop plants as Crop Watch.

From worldwide scenario, the pace of knowledge increment on EG studies highly indicates that this area is not a new knowledge since it can be easily found in the literature (see Nevo et al., 1986 [1]). However, in Malaysia, the first (perhaps) paper on such topic was published by Yap et al. [2], which will be further discussed in the following paragraph.

Anthropogenic activities have created significant impacts on chemical levels in the coastal environment [3], including inorganic and organic (persistent and emerging) chemicals. The evaluation of EG study in Malaysia is based on the marine mussel P. viridis as a model in this review paper.

Firstly, the most detailed ecotoxicological and biomonitoring study on P. viridis was that reported by Yap et al. [4] which reported on four heavy metals. As found in the literature, heavy metal pollution in Malaysia is increasingly reported in the literature since early 2000 see Yap et al., [5,6]. Application of the biomonitoring data of heavy metals in the marine mussels from Malaysia has been assessed for human health risks [7].

Secondly, the first genetic structures of P. viridis were investigated by Yap et al. [8] by using electrophoretic allozyme study. The genetics differentiation/composition of P. viridis is heavily dependent on free-swimming larvae along the west coast of Peninsular Malaysia especially in Malacca (Al-Barwani et al., 2007) [9]besides the physical barrier (the Johore Causeway [10] and heavy metal contamination in the east part of the Causeway [11,12]. These causative agents should merits more studies in future.

Yap and Tan [13] has made a comprehensive review on the EG studies, based on P. viridis, in Malaysia. This emerging research perspective, perhaps, has started with the use of allozyme polymorphism of P. viridis in relation to heavy metal stress [14]. Preliminary studies on the EG studies on biomonitors in Malaysia have been focused on green-lipped mussels [2,15,16], horseshoe crabs [17] and guppy fish [18].

Perhaps, the earliest EG study was that on the heavy metal stress on allozyme polymorphisms in Malaysia by Yap et al. [19]. They found a positive relationship between allozyme polymorphisms and heavy metal levels in P. viridis sampled from contaminated and uncontaminated coastal waters. Following that, Yap and Tan [15] reported changes in the enzymes GOT, EST and ME in direct connection to Zn stress. This was explained by a lower rate of filtration in the gills and a decreased value of condition index. The above laboratory experiment was conducted by using P. viridis as a test organism. The significance finding of Yap and Tan [15] supported the previous study by Yap et al. [20] that allozymes of P. viridis could be influenced by heavy metal stress based field collected samples. Yap et al. [16] reported significant (P< 0.01) relationships between heavy metal levels and RAPD primers in the byssus and soft tissues of P. viridis. This implied that correlation analysis between a specific primer of RAPD marker and a particular metal could be employed for the identification of metal pollution in the mussels.

Following the above EG studies by using P. viridis as a model, heavy allozyme polymorphisms and heavy metal levels were investigated in female guppy populations collected from two contrasting sites, namely polluted and unpolluted ecosystems [17]. They reported that the levels of Fe and Cu were significantly (P< 0.05) higher in guppy population sampled from polluted drainage than those from unpolluted ecosystem. This finding was largely supported by the significantly (P< 0.05) higher levels of Fe and Cu in the surface sediments, showing contamination by Fe and Cu in the polluted drainage. Based on allozyme study, they found that the banding pattern of the unpolluted wild guppy population with monomorphic alleles which were similar and comparable to unpolluted domesticated guppy population bought from a pet shop. This confirmed that LDH in the guppy can be used as a good biomarker of Fe and Cu contamination. Almost similar ecotoxicological genetic approach was applied to horseshoe crab populations in Malaysia by Yap et al. [18]. They sampled populations of horseshoe crab (Carcinoscorpius rotundicauda) from contaminated and uncontaminated coastal areas of Peninsular Malaysia.

Future ecotoxicological genetic studies should focus on crop plants since they are the major food sources to the ever increasing world populations nowadays. Food crop such as oil palm is an important focus. This is due to the fact that oil palm (Elaeis guineensis Jacq.) has arisen as a key economic crop nourishing the world population nowadays [21]. For example, ecotoxicological monitoring study has been conducted in the oil palm by Yap et al. [22] while genetic studies on the oil palm by Wahid et al. [23] for the high-quality planting material through genetic improvements. However, the above two studies were conducted separately and interpretations were made based on ecotoxicology and genetics, respectively. Future studies should merge the two areas as EG study to make the our understanding in a more holistic ecologically and genetically. Other ecotoxicological monitoring study in crops such as papaya and bananas have been published by Yap et al. [24] and Yap et al. [25], respectively. However, the genetic studies on the above crops are lacking in the literature.

Therefore, Crop Watch is a new research approach incorporating ecotoxicology and genetics. This EG studies hold a great potential research in the future, not only in academia but also commercial industries.

In conclusion, the above literature review indicated Crop Watch by means of EG studies is a potential (although not a new) research area. Considering the importance and combination of knowledge on ecology, ecotoxicology and genetics would help to monitor the growth and yield besides human health risk assessment of the crop better. This Crop Watch approach is expected to continue in future, especially in Malaysia and other Asian countries.

References

1. Nevo E, Noy R, Lavie B, Beiles A, Muchtar S (1986) Genetic diversity dan resistance to marine pollution. Biol J Linn Soc 29: 139–144.
2. Yap CK, Ismail A, Tan SG and Rahim Ismail A (2004) Assessment of different soft tissues of the green-lipped mussel Perna viridis (Linnaeus) as biomonitoring agents of Pb: Field and laboratory studies. Wat AirSoil Pollut 153: 253–268.
3. Amin B, Ismail A, Arshad A, Yap CK and Kamarudin MS (2009) Anthropogenic impacts on heavy metal concentrations in the coastal sediments of Dumai, Indonesia. Environ Monitor Assess 148: 291–305.
4. Yap CK, Ismail A and Tan SG (2003) Background concentrations of Cd, Cu, Pb and Zn in the green-lipped mussel Perna viridis (Linnaeus) from Peninsular Malaysia. Mar Pollut Bull 46: 1043–1048.
5. Yap CK, Ismail A, Din Mohd A, Said ZB Tan S. and Siraj SS (2005) Heavy metal (Cd, Cu, Pb dan Zn) concentrations in the green-lipped mussel Perna viridis (L.) from artificial substrates at aquacultured farm of Sebatu. Malays Fisheries J 4: 81–87.
6. Yap CK, Yeow KL, Edward FB and Tan SG (2009) Revealing copper contamination at the penang industrial area by using Malaysian Mussel Watch Approach. Asian J Microbiol Biotechnol Environ Sci 11: 683–689.
7. Yap CK, Cheng WH, Karami A and Ismail A (2016) Health risk assessments of heavy metal exposure via consumption of marine mussels collected from anthropogenic sites. Sci Tot Environ 553: 285–296.
8. Yap CK, Tan SG, Ismail A and Omar H (2002) Genetic variation of green-lipped mussel Perna viridis (Linnaeus) from the west coast of Peninsular Malaysia. Zool Stud 41: 376–387.
9. Al-Barwani SM, Arshad A, Nurul Amin SM, Japar SB, Siraj SS, Yap CK (2007) Population dynamics of the green mussel Perna viridis from the high spat-fall coastal water of Malacca, Peninsular Malaysia. Fish Res 84: 147–152.
10. Yap CK, Cheng WH, Ong CC and Tan SG (2013) Heavy metal contamination and physical barrier are main causal agents for the genetic differentiation of Perna viridis populations in peninsular Malaysia. Sains Malays 42: 1557–1564.
11. Yap CK, Mohd Nasir S, Edward FB and Tan SG (2012a) Anthropogenic inputs of heavy metals in the east part of the Johore Straits as revealed by their concentrations in the different soft tissues of Perna viridis (L.). Pertanika J Trop Agric Sci 35: 827–834.
12. Yap CK, Shahbazi A and Zakaria MP (2012b) Concentrations of heavy metals (Cu, Cd, Zn and Ni) and PAHs in Perna viridis collected from seaport and non-seaport waters in the Straits of Johore. Bull Environ Contam Toxicol 89: 1205–1210.
13. Yap CK and Tan SG (2011) Ecotoxicological genetic studies on the green-lipped mussel Perna viridis in Malaysia. In: L.E. McGevin, ed., Mussels: Anatomy, habitat and environmental impact. Nova Science Publishers USA 221–244.
14. Tan SG, Yap CK (2006) Biochemical and molecular indicators in aquatic ecosystems: Current status and further applications in Malaysia. Aquat Ecosyst Health Manage 9: 227–236.
15. Yap CK, Tan SG (2007) Changes of allozymes (GOT, EST and ME) of Perna viridis subjected to zinc stress: A laboratory study. J Appl Sci 7: 3111–3114.
16. Yap CK, Chua BH, Teh CH, Tan SG, Ismail A (2007) Primers of RAPD markers and heavy metal concentrations in Perna viridis (L.), collected from metal-contaminated and uncontaminated coastal waters: Are they correlated with each other? Russian J. Genetics 43: 544–550.
17. Yap CK, Chong CM, Tan SG (2011a) Lactate dehydrogenase in the guppy fish (Poecilia reticulata) as a biomarker of heavy-metal pollution in freshwater ecosystems. J. Sust. Manage. 6(2): 240–246.
18. Yap CK, Chong CM, Tan SG (2011b) Allozyme polymorphism in the horseshoe crabs Carcinoscorpius rotundicauda collected from polluted intertidal area in Peninsular. Malaysia. Environ Monitor Assess 174: 389–400.
19. Yap CK, Ismail A, Tan SG, Rahim Ismail A (2004b) The impact of anthropogenic activities on heavy metal (Cd, Cu, Pb and Zn) pollution: Comparison of the metal levels in green-lipped mussel Perna viridis (Linnaeus) and in the sediment from a high activity site at Kg. Pasir Puteh and a relatively low activity site at Pasir Panjang. Pertanika J Trop Agric Sci 27: 73–78.
20. Yap CK, Tan SG, Ismail A, Omar H (2004c) Allozyme polymorphisms and heavy metal levels in the green-lipped mussel Perna viridis (Linnaeus) collected from contaminated and uncontaminated sites in Malaysia. Environ Int 30: 39–46.
21. Kushairi A, Soh KL, Azaman I, Elina H, Meilina-Ong A, et al.(2018) Oil palm economic performance in Malaysia and R & D progress in 2017. J Oil Palm Res 30: 163–195.
22. Yap CK, Nur Aishah H, Cheng WH, Zakaria MP, Al-Shami SA (2019a) Bioaccumulation of Cu and Pb in the different parts of oil palm (Elaeis guineensis) in comparison to their habitat topsoils. In: Soil Pollution: Sources, Management Strategies and Health Effects, Editor: Chee Kong Yap, Nova Science Publishers, New York, USA.
23. Wahid MB, Nor S, Abdullah A, Henson IE (2005) Oil Palm – achievements and Potential. Plant Prod Sci 8: 1–13.
24. Yap CK, Nur Sakinah MJ, Cheng WH, Omar H, Nulit R, et al (2019b) Distribution of Ni and its human health risk assessment in the Carica papaya from Peninsular Malaysia. In: Soil Pollution: Sources, Management Strategies and Health Effects, Editor: Chee Kong Yap, Nova Science Publishers, New York, USA.
25. Yap CK, Ahmad Zulfadhli T, Cheng WH, Sharifinia M, Ye F, et al (2019c) Health risks of heavy metals via consumption of Musa paradisiaca and the ecological risk assessment of heavy metals in the habitat topsoils. In: Soil Pollution: Sources, Management Strategies and Health Effects, Editor: Chee Kong Yap, Nova Science Publishers, New York, USA.