Abstract
Nearly 1.4 billion people in 73 countries worldwide are threatened by lymphatic filariasis, a parasitic infection that leads to a disease commonly known as elephantiasis. Filariasis is vectored by mosquitoes, with special reference to the genus
Culex
. The main control tool against mosquito larvae is represented by treatments with organophosphates and insect growth regulators, with negative effects on human health and the environment. Recently, green-synthesized nanoparticles have been proposed as highly effective larvicidals against mosquito vectors. In this research, we attempted a reply to the following question: do green-synthesized nanoparticles affect predation rates of copepods against mosquito larvae? We proposed a novel method of seaweed-mediated synthesis of silver nanoparticles using the frond extract of
Caulerpa scalpelliformis
. The toxicity of the seaweed extract and silver nanoparticles was assessed against the filarial vector
Culex quinquefasciatus
. Then, we evaluated the predatory efficiency of the cyclopoid crustacean
Mesocyclops longisetus
against larval instars of
C. quinquefasciatus
in a nanoparticle-contaminated water environment. Green-synthesized silver nanoparticles were characterized by UV–vis spectrum, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In mosquitocidal assays, the LC
50
values of the
C. scalpelliformis
extract against
C. quinquefasciatus
were 31.38 ppm (I), 46.49 ppm (II), 75.79 ppm (III), 102.26 ppm (IV), and 138.89 ppm (pupa), while LC
50
of silver nanoparticles were 3.08 ppm, (I), 3.49 ppm (II), 4.64 ppm (III), 5.86 ppm (IV), and 7.33 ppm (pupa). The predatory efficiency of the copepod
M. longisetus
in the control treatment was 78 and 59 % against I and II instar larvae of
C. quinquefasciatus
. In a nanoparticle-contaminated environment, predation efficiency was 84 and 63 %, respectively. Predation was higher against first instar larvae over other instars. Overall, our study showed that seaweed-synthesized silver nanoparticles can be proposed in synergy with biological control agents against
Culex
larvae, since their use leads to little detrimental effects against aquatic predators, such as copepods.