Chemoattraction between fry of Arctic char [Salvelinus alpinus (L.)] studied in a Y-maze fluviarium

Attraction of fry of Arctic char [Salvelinus alpinus (L.)] to water conditioned by conspecifics of the same age was studied in a Y-maze fluviarium. Two types of experiments were run. In up-swimming tests (1), starting from the common leg of the Y-maze, a single fish was given the choice of entering one of the two upstream arms. In gradient tests (2), the momentary positions of a single char were time-lapse photographed in a test yard of this common shank. Strong attraction to conditioned water was observed in both types of tests.     

Schistosome behavior in vitro

Schistosome adults attract each other in vitro and the attraction is chemically mediated. InSchistosoma mansoni adults, excretory-secretory (ES) products of worms of one sex attract worms of the opposite sex, and at least the lipophilic fraction is attractive. Intra- and interspecific attraction occurs inSchistosoma mansoni, S. japonicum, andS. haematobium adults. Current knowledge of schistosome behavior in vitro is reviewed.     

Misleading the Colorado potato beetle with an odor blend

Walking tracks of Colorado potato beetles,Leptinotarsa decemlineata Say, were recorded on a locomotion-compensator in response to wind, odors of host plantsSolanum tuberosum L. and nonhost plantsLycopersicon hirsutum f.glabratum C.H. Mull, and to mixtures of these plant species. Host-plant odor induced positive anemotactic responses in starved females, whereas odor of the nonhostL. hirsutum was neither repellent nor attractive. The attractiveness of host-plant odor, however, was neutralized in the odor blend of plant species. Masking the attractive host-plant odor will hinder the beetle's searching for host-plant patches, and this principle may be exploited in pest control by mixed cropping.The locomotion-compensator was constructed with financial support from the Foundation for Fundamental Biological Research (BION), which is subsidized by the Netherlands Organization for the Advancement of Pure Research (ZWO), grant 14-02-02. The first author was supported by a grant from the French Ministry of Industry and Research.     

Intraspecific and interspecific chemoattraction inBiomphalaria glabrata andHelisoma trivolvis (Gastropoda: Planorbidae)

A Petri dish bioassay previously used to examine food preferences in planorbid snails was used to study intraspecific and interspecific chemoattraction inBiomphalaria glabrata (albino strain, M-line) andHelisoma trivolvis (Colorado strain) snails.B. glabrata snails showed significant intraspecific chemoattraction in the absence of visual cues and snail thigmotaxis.H. trivolvis snails also showed significant intraspecific chemoattraction. Interspecific chemoattraction between these species occurred in the bioassay, suggesting that the chemoattractants were not species specific. Artificial spring water conditioned by aqueous excretory-secretory products (snail-conditioned water) ofB. glabrata elicited significant intraspecific chemoattraction. However, lipophilic excretory-secretory products ofB. glabrata elicited significant chemorepulsion. Repellant factors in the lipophilic fraction were not characterized.     

Chemical communication in adult schistosomes

Lipids released bySchistosoma mansoni adult males attract females in vitro. Lipid release is modulated by the presence of other worms. AlthoughS. mansoni males release lipid when paired with females, the release is enhanced when they are separated.S. japonicum adults release more free sterols when incubated individually than when incubated together. Similarly, individually incubatedS. haematobium males release more free sterols than when incubated in groups. However,S. haematobium females incubated in groups release more free fatty acids than do equal numbers of males or pairs incubated in groups. There is evidence thatS. mansoni adult females concomitantly accumulate and release cholesterol in the absence of an exogenous supply, although de novo synthesis of cholesterol in schistosomes has not yet been demonstrated. Schistosomula and adult schistosomes incorporate exogenous lipids. Lipids are incorporated chiefly through the tegument. Cholesterol is transferred between males and females.     

Time-lapse video tape documentation of chemical orientation bySchistosoma mansoni in vitro

In vitro, the opposite sexes ofS. mansoni are attracted to each other by some means of premating communication which culminates in aggregation and copulation of sexual pairs within 24 hr. The system used for time-lapse video tape documentation of worm sexual behavior in vitro is described and evidence of sexual chemoattraction is presented.     

Pellioditis pellio: Substituted phenolic compounds as chemoattractants

Vanillin, vanillic acid, and other related compounds are chemoattractants either for nematodes or arthropods. We tested vanillin, vanillic acid, and 2,4-dihydroxybenzaldehyde in an in vitro bioassay system for their ability to attractPellioditis pellio males and females. Females were not attracted to any of the three compounds tested. Males responded to vanillin and vanillic acid, but not to 2,4-dihydroxybenzaldehyde. Males responded to vanillin and vanillic acid when these compounds were present at 10^–5 M concentration. Vanillin at 10^–3 and 10^–7 M concentrations was not attractive.     

Chemoattraction inPellioditis pellio (Nematoda: Secernentia) in the presence and absence of barriers

Pellioditis pellio (Nematoda) adults showed heterosexual chemoattraction and female homosexual chemoattraction in an in vitro bioassay without barriers. Male-to-female heterosexual, but no homosexual chemoattraction, was observed whenM _r 25,000 pore size dialysis tube chimneys (barriers) were used to restrain female attractor worms. Less attraction was seen whenM _r 12,000 pore size barriers were used. The results suggest the presence of at least two types of chemoattractant for this species and that at least one heterosexual chemoattractant is betweenM _r 12,000 and 25,000.