Toxicological screening of marine red algae Champia parvula (C. Agardh) against the dengue mosquito vector Aedes aegypti (Linn.) and its non-toxicity against three beneficial aquatic predators

Highlights

• Larvicidal activity of ethanolic extracts of marine Champia parvula (Ex-Cp) against the dengue mosquito vector Ae. aegypti.

• Sub-lethal dosage of Ex-Cp significantly alters the physiological as well as enzyme activity of carboxylesterase (α and β), GST and CYP450.

• Ex-Cp displayed significant repellent activity (97%) with maximum level of protection time (210 minutes) at the lethal dosage of 100 ppm.

• Non-target toxicity of Ex-Cp against the beneficial aquatic mosquito predators displayed less toxicity.

Abstract

Larval toxicity of ethanolic extract of C. parvula (Ex-Cp) was prominent in the second and the third instars at the maximum lethal dosage of 100 ppm with 98 and 97 % mortality rate respectively. The LC₅₀ and LC₉₀ was displayed at 43 ppm and 88 ppm dosage respectively. Correspondingly, the sub-lethal dosage (65 ppm) of Ex-Cp significantly alters the carboxylesterase (α and β), GST and CYP450 enzyme level in both III and IV instar larvae in dose-dependent manner. Similarly, the Ex-Cp displayed significant repellent activity (97 %) with a maximum level of protection time (210 min). Photomicrography assay of Ex-Cp (65 ppm) were toxic to dengue larvae as compared to control. The non-target toxicity of Ex-Cp against the beneficial mosquito predators displayed less toxicity at the maximum dosage of 600 ppm as compared to Temephos. Thus the present research delivers the target and non-target toxicity of red algae C. parvula against the dengue mosquito vector.

Introduction

Vector-borne diseases (VBD) are generally caused by the dreadful pathogens and parasites in human populations across the nations (Ellse and Wall, 2014). The major vector responsible for spreading the disease is mosquitoes which is the superlative in spreading the diseases as compared to other species of flies, ticks, sandflies, bugs, fleas and freshwater snails (European Centre for Disease Prevention and Control, 2014; Edwin et al., 2016). Among VBD, Dengue is considered as the remotest re-emerging diseases spreads across the countries leads to heavy health and economic loss on developing nations (Arunachalam et al., 2010; Benelli, 2015, 2016). The chief mosquito responsible for dispersal dengue fever is Aedes aegypti (Diptera: Culicidae) Linn. and regarded as the primary vector for this virus in South Asian Countries (World Health Organization, 2009a, 2009b; Polson et al., 2011; Thanigaivel et al., 2012; Reegan et al., 2015; Lija-Escaline et al. (2015)). Despite, there is no attainment has been achieved in controlling Ae. aegypti, across the nations after expensing significant money to eradicate the arthropod vector (Shaalan et al., 2005; Silva et al., 2008). The effective strategies were conducted to control the mosquito larvae using larvicides and mosquito adults using adulticides of synthetic chemical origin (Chellappandian et al., 2017, 2018). Despite, persistent usage of commercial insecticides for dengue vector management has resulted in the minor efficacy and higher resistance rate and more importantly higher environmental risks and potential human health loss due to this indiscriminate usage of synthetic chemicals (Senthil-Nathan et al., 2004; Pates and Curtis, 2005; Senthil-Nathan et al., 2005; 2006; Senthil-Nathan, 2015). Chemical resistance are linked to upsurge in insecticide metabolism, such as the uplifting the detoxifying enzyme rate or structural changes in the enzyme that escalate the metabolic capacity (Polson et al., 2011; Diniz et al., 2015). Owing to its resistance and non-target impacts global researchers attention has been drifted to the alternate techniques especially from the source of natural origin intended to control mosquito vectors (Bakkali et al., 2008; Thanigaivel et al., 2017; Vasantha-Srinivasan et al., 2017, 2018). The phyto-compounds present in the natural based insecticides has proved as an effective mosquitocidal and insecticidal properties observed by global scientist (Rehman et al., 2014; Benelli et al., 2016).

Seaweeds are marine macro algae and primitive type of plants, growing abundantly in the shallow waters of sea, estuaries and back waters while flourish wherever rocky (Ali et al., 2013). They commonly grow on coral reefs of rocky landscape or can grow at great depths if sunlight can penetrate through the water (Manilal et al., 2009). Most of the seaweeds can be seen booming under water beds floating along the sea surface attached to rocks (Collen et al., 2001). More than 90 % of botanicals of marine origin are signified by algae and form a vital part of the coastal environment (Manilal et al., 2011). Among them the red seaweed has been widely harvested and consumed as the major source in South Asian Countries and many communities actively occupied in red seaweed farming for agar and carrageenan manufacturing (Crawford et al., 1999). Among them, the marine red alga Champia parvula (C. Agardh) Harvey. has blended with diversified natural bioactive compounds including carbohydrates, lipids, vitamins, proteins, amino acids, minerals, agar, alginates, phycocyanins, fucoidans, glycoproteins, pheophytins, sargachromanol-E, elatols, stypodiol diacetate, phlorotannins furanones and monoterpenes and it is highly applied in pharmaceutical industries (Murugesan et al., 2015). Red algae are commercially used as human food stuff in the diet. The major active ingredients are carotenoids, dietary fibres, proteins, essential fatty acids, vitamins and minerals. Marine algae are exploited chiefly for the industrial production of phycocolloids such as Alginate Agar-Agar and Carrageenan. Among the macro algae of the region, the red algal species grow in abundance as dominant communities in the shores of South Asian Countries especially abundant in India. The algal extracts were reported to have a promising effect on multi-drug resistant such as Staphylococcus aureus (Dadgar et al., 2006). Despite their insecticidal activity against the dreadful mosquito vectors remains to be investigated. The sea weeds and its major derivatives will deliver a low cost, ecologically safe phyto-chemical insecticides to control dengue vectors in local, and rural regions which have few other options as preventive measures. Overall, research and development of EO products in this review adds to the baseline of information available on the internet databases. Thus the present research was aimed to investigate the larvicidal, metabolic enzyme inhibitory property of biologically derived marine C. parvula (C. Agardh) Harvey. against the medically challenging dengue mosquito vector and its non-toxicity against the beneficial aquatic predator.