Biocidal activity of algal toxins against immature mosquitoes

Abstract

Extracts of two species of green algae, filamentousRhizoclonium hieroglyphicum Kütz and a phytoplankton,Chlorella ellipsoidea Gerneck, obtained with solvents in the laboratory were assayed againstAedes aegypti L.,Culex quinquefasciatus Say, andCuliseta incidens (Thomson). On extraction with petroleum ether, groundR. hieroglyphicum yielded an active crude extract which was chromatographed on a neutral alumina column and eluted consecutively with petroleum ether, benzene, and methanol. All three eluted fractions were found to induce significant mortality in test mosquito species. The benzene-eluted fraction was the least toxic. The methanol-eluted fraction was the most toxic to all species and exhibited juvenile hormone-like activity; it also caused morphogenetic changes in emerging adults. All three fractions delayed the rate of development of mosquito larvae by 2-5 days. Three supernatants ofC. ellipsoidea obtained on different occasions were tested against first instars ofC. quinquefasciatus. After the confirmation of their activity, all supernatants were extracted with diethyl ether, combined, and assayed against first- and fourth-stage larvae of the three mosquito species. The first-stage larvae ofC. quinquefasciatus andC. incidens were approximately three times more suspectible than those ofA. aegypti. However, fourth-stage larvae of the former two species were about twice as susceptible to the extract as those of the latter species. Dead first-stage larvae of all the species had a shrunken appearance. In general,C. ellipsoidea extract was quicker acting than that ofR. hieroglyphicum.

Larvicidal effects of various essential oils against Aedes, Anopheles, and Culex larvae (Diptera, Culicidae)

“…Similarly, when extracts of the pond weeds Myriophyllum and potamogeton were assayed against larvae of Anopheles occidentalis and C. pipiens, C. pipiens showed more resistance to both extracts (Graham and Schooley 1984). Such a differential species susceptibility was also noticed by Dhillon et al (1982), when algal toxins were assayed against A. aegypti, C. quinquefasciatus and Culiseta incidens.…”

Effect of selected marine and freshwater microalgae on development and survival of the mosquito Aedes aegypti

“…In some cases, such as with S. quadricauda, previous negative impacts were attributed to indigestibility (Marten 1986a, b) and, in our experiments, this effect was likely mitigated by the addition of alternative food. In other cases, such as with some of the C. vulgaris strains (e.g., Dhillon et al 1982;Ahmad et al 2001;Marten 2007), the disparity may be due to strain/species-specific differences or methodological differences in handling the algal material (Goldman and Dennett 1985) and/or in the exposure of the insects to the toxins, particularly whether they were exposed to whole cell algal material or to concentrated extracts of algal cell contents (Shaalan and Canyon 2005). Here, we challenged mosquitoes with three C. vulgaris strains and did not observe significant negative effects on development time, body size, or rate of increase (k 0 ) by A. aegypti.…”

“…Many cyanobacteria (blue-green algae) have been shown to produce substances that are toxic to mosquito larvae (e.g., Carmichael 1992; Saario et al 1994;Harada et al 2000). Some green algae may produce substances that are toxic to subadult mosquitoes (e.g., Dhillon and Mulla 1981;Dhillon et al 1982), and other species can cause local reduction or elimination of mosquito populations because of their indigestibility (Marten 1984(Marten , 1986a. Marten (2007) provided a recent review of the larvicidal capacities of algae and Shaalan and Canyon (2005) a general review of phytochemicals for mosquito control.…”

Does Autocthonous Primary Production Influence Oviposition byAedes japonicus japonicus(Diptera: Culicidae) in Container Habitats?

“…Marten (1986, 2007) documented the occurrence of certain algal taxa in mosquito habitats that are indigestible to larvae because of the presence of the carotenoid sporopollenin in their cell walls. In addition, certain taxa of algae, especially the Cyanobacteria, are known to produce toxins that are damaging or lethal to mosquito larvae (Dhillon et al 1982, Kiviranta et al 1993). Though we believe that our algal communities were representative of those occurring naturally in container habitats, some of the algae colonizing our containers may not have been good larval food resources and potentially less attractive as stimuli for oviposition.…”