Allelochemics produced by the hydrophyteMyriophyllum spicatum affecting mosquitoes and midges

Abstract

An extract of the hydrophyteMyriophyllum spicatum L. was found to be toxic to first- and fourth-instar larvae of the mosquitoes,Culex quinquefasciatus Say,Culex tarsalis Coquillett,Culiseta incidens (Thomson),Aedes aegypti L., and chironomid midges in the laboratory. When first-stage larvae were exposed to the extract, the lowest concentration (6.4 mg extract/100 ml H2O) produced 86,60, and 48% mortality inC. incidens, C. quinquefasciatus, andA. aegypti, respectively. Higher concentrations caused 100% mortality in both first and fourth instars (63.75 mg/100 ml H2O or more). In general, the biocidal activity of the extract was found to be similar when first- and fourth-stage larvae were exposed. Some mortality in the successive pupal and adult stages was observed when fourth-stage larvae were exposed to the extract, but mortality occurred only in the various larval instars when first instars were exposed. Among the chironomids,Tanytarsus spp. was more tolerant to the extract thanChironomus spp. In addition to the biocidal activity against immature mosquitoes, the extract was found to show a unique activity acting as an attractant to both sexes of adultC. quinquefasciatus andA. aegypti. The response elicited inA. aegypti appeared to be somewhat higher than that inC. quinquefasciatus. In general, the percentage of males responding to water treated with the extract was higher than that of the females. The extract at higher concentrations seemed to show some repellency at the outset to both species, but induced positive responses later on.

Distribution differences and active habitat choices of invertebrates between macrophytes of different morphological complexity

“…Bioactive chemicals affecting biota have been documented for M. spicatum (Körner and Nicklisch 2002) and C. baltica (in plant extracts; WiumAndersen et al 1982), but not for P. pectinatus (Körner and Nicklisch 2002). Although such chemicals from M. spicatum have been documented as having only negative effects on invertebrates (dipterans, Dhillon et al 1982;mysids, Lindén and Lehtiniemi 2005), we cannot exclude that bioactive chemicals may have attracted other invertebrate species in the present study. The animals could also be attracted by the palatability and nutritional content of plants, which are determined by their physical and chemical properties.…”

“…Several other factors of natural plants could influence the invertebrate distributions. The animals could be affected by plantsecreted bioactive chemicals that could attract (Brönmark 1985), repel, or kill the invertebrates (Dhillon et al 1982;Lindén and Lehtiniemi 2005) or affect the periphyton food resources for the animals (Hilt 2006). Bioactive chemicals affecting biota have been documented for M. spicatum (Körner and Nicklisch 2002) and C. baltica (in plant extracts; WiumAndersen et al 1982), but not for P. pectinatus (Körner and Nicklisch 2002).…”

The lethal and sublethal effects of the aquatic macrophyte Myriophyllum spicatum on Baltic littoral planktivores

“…The ultimate reason for the production of repellent chemicals in aquatic macrophytes may be herbivore deterrence (Dhillon et al 1982;Cronin and Hay 1996a), gaining competitive advantage over other autotrophs (Gross 2003) or both. If the toxicity is primarily an inducible defense against herbivores, tissue damage may facilitate the production and excretion of the chemicals (Levin 1971;Cronin and Hay 1996b).…”

“…Several Myriophyllum species inhibit the growth of phytoplankton, especially cyanobacteria (reviewed in Gross 2003), and repel cladocerans (Pennak 1973;Lauridsen and Lodge 1996). Potentially the most harmful species in the genus is Myriophyllum spicatum, which has negative effects on phytoplankton (reviewed in Gross 2003), other macrophytes (Agami and Waisel 1985), and animals, such as mosquitoes and midges (Dhillon et al 1982;Johnson and Mulla 1983). Similarly, Chara spp.…”

Analyzing the effects of four submerged macrophytes with two contrasting architectures on zooplankton: A mesocosm experiment

“…Additionally, greater water circulation in V. americana stands could guarantee other critical conditions for macroinvertebrates like higher dissolved oxygen levels than other macrophytes (Caraco and Cole, 2002). In addition, allelochemicals releasing from macrophytes decreased survival or changed behaviors of some invertebrate taxa (dipteran larvae, Dhillon et al, 1982;mysids, Lindén and Lehtiniemi, 2005), but the concentration and effectiveness of such substances varied with macrophyte species. Gross (2003) reported that allelopathic substances have been documented for M. spicatum but, are rare among submerged Potamogeton species.…”