Toxic assessment, growth disrupting and neurotoxic effects of red seaweeds’ botanicals against the dengue vector mosquito Aedes aegypti L

• Published in: Ecotoxicology and environmental safety 2020-06, Vol.195, p.110451, Article 110451
• Main Authors: Bibi, Rabia, Tariq, Rajput Muhammad, Rasheed, Munawwer
• Format: Article
• Language: English
• Subjects: Aedes aegypti; Asparagopsis taxiformis; Gracilaria foliifera; Jania rubens; Laurencia karachiana; Pesticidal effects
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2020.110451

Application of synthetic pesticides over decades to control insects, pests, and disease vectors has resulted in negative impacts on environment and health. The current study assessed the toxicological effects of 12 botanicals obtained from 4 different red seaweeds against the dengue vector mosquito Aedes aegypti L. (Diptera: Culicidae). Four species of red seaweeds, namely Laurencia karachiana, Gracilaria foliifera, Jania rubens, Asparagopsis taxiformis, were collected from Karachi coast and extracted with hexane, dichloromethane and methanol. The efficiency of these extracts was determined by using a dose-response bioassay method against 4th instar larvae of Ae. aegypti. Separate investigations on the toxicity and IGI effects were done. Comparative studies showed that the hexane extracts induced more toxic effects. Based on the LC50 values, obtained after 24 h of treatments, hexane extract of J. rubens (HJ) exhibited toxic effects with LC50 32 μg/mL, (equivalent to GHS category 3), followed by G. foliifera (HG) (LC50 76.8 μg/mL). HJ also showed prominent neurotoxic effects within 1–6 h. Comparatively, higher morphological abnormalities and growth inhibiting (IGI) effects were obtained in the dichloromethane and methanol extracts treated larvae, after 48–96 h, resulting in the formation of immature life forms such as larvi-pupae and pupi-adult. Presumptive growth inhibiting effects were also noted. These included formation of albino and black pupae, deformities in the internal structure of the treated larvae and the chitin synthesis related effects such as ‘inhibiting effect on adult emergence’. Finding revealed that red seaweeds, harvested from the Arabian Sea, have potentials to affect Ae. aegypti survival and thus can be utilized as green pesticides. [Display omitted] •Ae. aegypti is a common vector for dengue, chikungunya, zika, yellow fever viruses.•Toxicity assessed of 3 different extracts from 4 red seaweeds against dengue vector.•All hexane extracts showed some neurotoxic activity against 4th instar larvae.•Morpho-anatomical, growth inhibiting abnormalities seen in larvae, pupae and adults.•Larvicidal effects observed in hexane extract from J. rubens was maximum.