Responses of Mud Snails and Periwinkles to Environmental Odors and Disaccharide Mimics of Fish Odor

Estuarine snails, periwinkles (Littoraria irorata), and mud snails (Ilyanassa obsoleta) were tested for behavioral responses to aqueous extracts of tissue macerates, odors of living intact organisms, and to disaccharides derived from heparin. Extracts included salt-marsh cordgrass (Spartina alterniflora), pink shrimp (Penaeus duorarum), crushed periwinkles, and crushed mud snails. Odors included live periwinkles, mud snails, stone crab (Menippe mercenaria), striped hermit crab (Clibanarius vittatus), tulip snail (Fasciolaria hunteria), and mummichog (Fundulus heteroclitus). Responses were determined upon contact by snails of a ring of solution in the bottom of an otherwise dry bowl and by presenting snails in seawater with 25 l of solution on a cotton swab. In each test, the response of 30 individuals was determined. Behaviors were recorded as fed, alarm, and no response. The strongest alarm response (>80% of all snails tested) in both snails was elicited by crushed mud snails. The strongest feeding response was to shrimp and periwinkle extract for mud snails (>70%), and salt-marsh cordgrass extract attracted periwinkles. High percentages of mud snails and periwinkles fled in response to the odors of intact snail predators, stone crabs, tulip snails, and mummichogs. Mud snails and periwinkles did not flee in response to nonpredator odors, including each other's odor, as well as that of hermit crabs, shrimp, and marsh cordgrass. Heparin disaccharides were tested because other studies reported that biological activity of predatory fish odor is due to similar disaccharides originating from fish mucus. Mud snail responses to disaccharides indicate that they respond to the same kinds of molecules as crustacean larvae and that the modified amine on the disaccharide is essential for activity. The Q-tip assay is appropriate for bioassay-directed purification of alarm signals originating in fish body odor.     

Chemical mediation of egg capsule deposition by mud snails

Mud snails (Ilyanassa obsoleta = Nassarius obsoletus = Nassa obsoleta) deposit eggs in protective capsules on hard substrata in soft bottom environments. We studied sites of egg capsule deposition and snail movement responses to odors to determine if chemoreception plays a role in deposition site selection. From results of field surveys, laboratory experiments, and field experiments, we conclude that mud snails use chemoreception for capsule deposition. Attractive odors originate from mud snail and whelk egg capsules and from living bivalves. Evidence for attractive odors from conspecifics is equivocal. Capsules are deposited on living odor sources and nearby hard substrates. We hypothesize that deposition of capsules on living substrates increases the likelihood that embryos will survive by decreasing the chance of smothering of embryos by sediments.     

Sequestration of lichen compounds by three species of terrestrial snails

Three species of lichen-grazing snails,Balea perversa, Chondria clienta, andHelicigona lapicida, all from the Swedish island of Öland, were found to sequester lichen compounds when feeding on the crustous lichen speciesAspicila calcarea, Caloplaca flavovirescens, Lecanora muralis, Physcia adscendens, Tephromela atra, andXanthoria parietina. The lichen compounds detected in the soft bodies of the snail species analyzed included the anthraquinone parietin, the depside atranorin, as well as a presumable degradation product of the latter. Other lichen compounds such as (+)-usnic acid or -collatolic acid were not found in the soft bodies but were only detected in the feces, suggesting selective uptake of lichen compounds by the snails. In individuals ofC. clienta initially fed on the lichenX. parietina, the amount of sequestered parietin decreased over time on a parietin-free diet but was still detectable in the soft bodies after 28 days. In the ovoviviparous land snail,B. perversa, sequestered parietin was transferred from the mother to the eggs in the reproductive tract.Dedicated to Prof. Dr. F.-C. Czygan on the occasion of his 60th birthday.     

Semiochemical-Mediated Oviposition Avoidance by Female House Flies, <Emphasis Type="Italic">Musca domestica</Emphasis>, on Animal Feces Colonized with Harmful Fungi

House flies, Musca domestica, utilize ephemeral resources such as animal feces for oviposition and development of larval offspring, but they face competition with fungi that colonize the same resource. We predicted that house flies avoid oviposition on feces well-colonized with fungi, thereby reducing fungal competition for larval offspring. Working with fungal isolates from chicken feces, we have previously shown that prior establishment of Phoma spp., Fusarium spp., or Rhizopus spp. on feces significantly reduced oviposition by house flies. Here, we report that, in the headspace volatiles of these three fungal genera, five compounds (dimethyl trisulfide, an unknown, 2-phenylethanol, citronellal, norphytone) elicit responses from house fly antennae. In behavioral bioassays, dimethyl trisulfide and 2-phenylethanol significantly reduced oviposition by house flies. We conclude that fungus-derived volatiles serve as semiochemical cues that help house flies avoid resources colonized with fungal competitors for the development of larval offspring.     

Neutral lipids in snail-conditioned water fromBiomphalaria glabrata (Gastropoda: Planorbidae)

Thin-layer chromatography was used to study neutral lipids in snail-conditioned water (SCW) fromBiomphalaria glabrata snails. A major lipid fraction in SCW at 2 and 4 hr after snail incubation contained free fatty acids. Fatty acids released per snail per milliliter of water when 10 snails were incubated in 5 ml of deionized water for 4 or 2 hr was 2.4±0.4 µg/ml and 0.9±0.1 µg/ml (mean ± SE), respectively. The amount released at 4 hr was significantly greater than at 2 hr. Snails also released free sterols, a sterol ester-hydrocarbon fraction, methyl esters, and other unidentified lipid fractions into the water. The potential of these neutral lipids to serve as chemoattractants for larval trematodes or snails remains to be determined.     

Volatiles from Duck Feces Attractive to Mexican Fruit Fly

Aqueous extracts of three types of bird feces were attractive to laboratory-colony Mexican fruit flies in laboratory bioassays. Extracts of black-bellied whistling duck feces were chosen for further analysis. Duck feces extract was attractive to both sugar-fed and sugar-starved flies but was more attractive to sugar-fed flies. Protein deprivation of flies had no effect on their response. Duck feces incubated in water for 24 hr were more attractive than those incubated for longer periods. Duck feces extract was attractive at pH 5–9, but was most attractive at pH 9, indicating that more than one class of chemicals contributed to attractiveness of the feces. Major components of headspace of duck feces extracts collected by solid-phase microextraction and identified by GC-MS, GC-FID, and GC-FTD included ethanol, propanol, phenol, ammonia, low-molecular weight amines, and pyrazines. In general, chemicals containing nitrogen proved most attractive to sugar-fed flies. However, dimethylamine and 1-pyrroline were nearly equally attractive to sugar-fed and sugar-deprived flies. Two chemicals without nitrogen were attractive to sugar-deprived flies; none were attractive to sugar-fed flies. A synthetic mixture was prepared containing ammonia, methylamine, dimethylamine, trimethylamine, 1-pyrroline, phenol, and 2-ethylhexanol in amounts found in odor of duck feces extract. The synthetic mixture was 96% as attractive as duck feces extract to sugar-fed flies and 80% as attractive to sugar-deprived flies.     

House fly oviposition inhibition by larvae ofHermetia illucens,the black soldier fly

Wild populations of house flies were inhibited from ovipositing into poultry manure containing larvae of the black soldier fly,Hermetia illucens (L.). A laboratory strain of house fly responded differently, readily ovipositing into manure with lower densities of soldier fly larvae, but avoiding the higher densities tested. The amount of timeH. illucens larvae occupy the manure prior to an oviposition test influences ovipositional responses of house flies. Manure conditioned byH. illucens larvae for 4–5 days did not significantly inhibit house fly oviposition. We suggest that some type of interspecific chemical communication (allomone) is present.Diptera: Stratiomyidae.Portion of an MS thesis by S.W.B.Research partially supported by State and Hatch funds.     

Long-Term Effects on Food Choice of Land Snail Arianta arbustorum Mediated by Petasin and Furanopetasin, Two Sesquiterpenes from Petasites hybridus

Sesquiterpenes (STs) from the Senecioneae have been found to be potent snail repellents. We investigated the range of activity of the STs petasin, isopetasin, furanopetasin, kablicin, and cacalol, which were isolated from Petasites hybridus, P. kablikianus, and Adenostyles alpina. We found the petasin content of leaves of P. hybridus to lie within the range of deterrence of the isolated compound. Furthermore, leaf extracts containing petasin proved to be deterrent, and leaf discs with low petasin content were preferred over discs with higher petasin content. The cacalol-containing fraction of a leaf extract of A. alpina was not deterrent to the snails. When the snails had experience with the relevant ST one week before a choice test, their sensitivity towards petasine and furanopetasine increased whereas for the other ST it remained at the same level. We speculate that this sensitivity increase could be the result of a rapid long-term associative learning process, but there is also the possibility that these STs are directly interfering with the feeding motor program of the snails, thereby eliciting a direct neurophysiological sensitization reaction which prevents them from further feeding.     

Essential-Oil-Mediated Interactions Between Oregano Plants and Helicidae Grazers

Aromatic plants dominate in Mediterranean-type ecosystems. They often produce remarkable quantities of essential oils containing high amounts of phenolic isoprenoids, such as thymol and carvacrol. The purpose of this work was to examine the interactions between commonly occurring aromatic plants in the Mediterranean environment and their snail grazers. The aromatic plants used were two Origanum vulgare subspecies, subsp. hirtum and subsp. vulgare. They differ in the content and the qualitative composition of their essential oil; subsp. hirtum contains a much larger amount and is rich in phenolic compounds. Their effect on the foraging behavior of three snail species, native in Greece, was studied; the snail species were Helix lucorum, H. aspersa, and Eobania vermiculata. The snails' responses to different food sources, raw or processed, with or without essential oils, were evaluated during the different stages of the foraging cycle. During the encounter stage, snails were more repelled than attracted when close to phenol-rich foods. During the acceptance stage, all snail species tended to reject food types that contained high concentrations of subsp. hirtum essential oil. At the feeding stage, subsp. hirtum essential oil caused reduction of daily consumption rates. Overall, the essential oil of O. vulgare subsp. vulgare did not produce any marked change in the snails' behavior. In contrast, that of O. vulgare subsp. hirtum had a repellent effect, particularly when present in naturally occurring high concentrations. Among the snail species, H. lucorum, which does not share the same biotope with O. vulgare subsp. hirtum, was the least tolerant to its essential oil.     

Influence of age and body size on alarm responses in a freshwater snail Pomacea canaliculata

A hypothesis that size selection of prey by predators elicits size-specific responses from prey was examined. Freshwater snails, Pomacea canaliculata, ages 1, 3, 7, 15, 30, or 60 days, were given an extract of 3-day-old snails, and 3-day-old snails were given extracts of snails of the other ages or eggs. Snails 15 days or younger crawled out of the water in response to the 3-day-old snail extract, but older ones did not. The 3-day-old snails responded to the extracts of snails of all examined ages, but not to the extract of eggs. Snails of four size classes, 3-days-old, small (shell lengths 8–12 mm), medium (13–20 mm), and large (>28 mm) were given extracts of snails of each of these four classes. The 3-day-old snails crawled out of the water in response to the extract of 3-day-old snails, but showed a lower or no response to other extracts. Larger snails buried themselves in the soil in response to the extract of snails of similar sizes. These responses are discussed in the context of the evolution of the snail's avoidance behavior in response to the size-dependent prey choice by the predator.     

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.     

Recombinant Snail Sialic Acid Aldolase is Promiscuous towards Aliphatic Aldehydes

Aldolases are enzymes that reversibly catalyze the cleavage of carbon-carbon bonds. Here we describe a recombinant sialic acid aldolase originating from the freshwater snail Biomphalaria glabrata (sNPL), and compare its substrate spectrum with a sialic acid aldolase originating from chicken (chNPL). In contrast to vertebrate animals which can synthesize, degrade, and incorporate sialic acids on glycoconjugate ubiquitously, snails (as all mollusks) cannot synthesize sialic acids endogenously, and therefore the biological function and substrate scope of sNPL ought to differ significantly from vertebrate sialic aldolases such as chNPL. sNPL was active towards a series of sialic acid derivatives but was in contrast to chNPL unable to catalyze the cleavage of N-acetylneuraminic acid into N-acetylmannosamine and pyruvate. Interestingly, chNPL and sNPL showed contrasting C4(R)/(S) diastereoselectivity towards the substrates d -mannose and d -galactose in the presence of pyruvate. In addition, sNPL was able to synthesize a series of 4-hydroxy-2-oxoates using the corresponding aliphatic aldehyde substrates in the presence of pyruvate, which could be not achieved by chNPL.     

Role of volatile inforchemicals emitted by feces of larvae in host-searching behavior of parasitoidCotesia rubecula (Hymenoptera: Braconidae): A behavioral and chemical study

The role of volatile infochemicals emitted by feces of larvae in the host-searching behavior of the parasitoidCotesia rubecula was evaluated during single- and dual-choice tests inside a wind tunnel. The following treatments were tested: feces produced by second and fourth instars ofPieris rapae (preferred host), second instars ofP. brassicae (inferior host), second instars ofP. napi (nonhost), and wet feces of second instars ofP. rapae. During a single-choice situation females ofC. rubecula oriented to all types of feces tested. When a preference was to be made,C. rubecula preferred feces of second instars ofP. rapae over that of fourth, feces ofP. rapae over that ofP. brassicae, feces ofP. napi over that ofP. brassicae, and wet over normal host feces. No preference was exhibited between feces of second instars ofP. napi and that of second instars ofP. rapae. The relative importance of infochemicals from host feces versus plant damage caused by host larvae to the searching behavior ofC. rubecula was also evaluated. Plant damage was more important to the searching females than host feces when feces were present in specific concentrations in relation to damage. The volatiles released by normal and wet feces of second instars ofP. rapae, wet feces of fourth instars ofP. rapae, and normal and wet feces ofP. brassicae were collected and identified. Overall, 85 chemical compounds were recorded belonging to the following chemical groups: alcohols, ketones, aldehydes, esters, isothiocyanates, sulfides, nitriles, furanoids, terpenoids and pyridines. The blend of chemicals emitted by feces of different instars ofP. rapae and different species ofPieris exhibited an instar and species specificity in both quantity and quality. Wetting of normal feces increased the amount of volatile chemicals released, and it was also responsible for the appearance of new compounds. The role of feces of larvae in the host-seeking behavior ofC. rubecula is discussed.     

High-Performance Thin-Layer Chromatographic Analysis of Sugars in Snail-Conditioned Water and Mucus from Biomphalaria glabrata, Helisoma trivolvis, and Lymnaea elodes

The presence of sugars, particularly glucose, maltose, and sucrose, in the SCW of Biomphalaria glabrata, the two strains of Helisoma trivolvis, and Lymnaea elodes was variable, although only maltose was quantifiable in two samples of snail conditioned waters from B. glabrata. The only sugar detected in mucus was glucose, but it was below the lowest quantifiable amount in the mucus samples of B. glabrata and H. trivolvis. The mean percentage of glucose in the mucus of L. elodes was 0.0040% ± 0.00067%.     

Foraging Behavior of Anastrepha Ludens, A. obliqua, and A. serpentina in Response to Feces Extracts Containing Host Marking Pheromone

Following oviposition, females of many Tephritid flies deposit host marking pheromones (HMPs) to indicate that the host fruit has been occupied. We describe the foraging behavior of these three economically important species (Anastrepha ludens and A. obliqua from the fraterculus species group and A. serpentina from the serpentina species group) when they encounter an artificial fruit (green agar spheres wrapped in Parafilm) marked with intra- and interspecific feces extracts that contain, among other substances, host marking pheromone. When flies encountered fruit treated with either 1 or 100 mg/ml feces extract, there were drastic and statistically significant reductions in tree residence time, mean time spent on fruit, and in the number of oviposition attempts or actual ovipositions when compared to the control treatment (clean fruit). These responses were almost identical irrespective of extract origin (i.e., fly species), indicating complete interspecific HMP cross-recognition by all three Anastrepha species tested. We discuss the ecological and practical implications of our findings.     

Earthworm mucus stimulates oviposition in a predatory fly (Diptera: Anthomyiidae)

Coenosia tigrina larvae feed on earthworms. We hypothesized that earthworm mucus contains a kairomone that stimulates oviposition behavior in adultC. tigrina females, thus minimizing the search area in the soil required for newly eclosed larvae to find earthworms. In bioassays, adult females responded with extension of the ovipositor 25–43% of the time to earthworm-mucus-soaked filter paper disks compared to 6–7% in response to water-soaked disks. Ovipositor extension on mucus-soaked disks was followed by egg-laying 29% of the time and 0% of the time on water-soaked disks. Egg-laying byC. tigrina followed a diurnal periodicity, with most eggs laid in the latter half of the photophase even in the absence of earthworm mucus. More eggs were deposited from 1600 to 1800 hr by females given access to earthworm mucus during that period than were deposited by females not given access. There was no difference in the number of eggs deposited from 0600 to 0800 hr, by females given access to earthworm mucus or not. This is a time of day when few eggs are normally laid. This paper is the first report of an earthworm-produced kairomone in an insect-earthworm interaction. The kairomone may have potential for enhancing biological control of the onion maggot,Delia antiqua, which is a prey of adultC. tigrina.     

Semiochemicals from anal exudate of larvae of tsetse fliesGlossina morsitans morsitans Westwood andG. morsitans centralis Machado attract gravid females

Tsetse flies (Diptera: Glossinidae:Glossina) mature their offspring in utero, giving birth to mature larvae that burrow into soil and pupariate. During the hot dry seasons, puparia of some species of tsetse are aggregated in areas of deep shade in dense thickets. We have confirmed the presence of a semiochemical from the prepupariation excretions of larvae ofGlossina morsitans morsitans Westwood and report a similar semiochemical inGlossina morsitans centralis Machado. These semiochemicals are attractive to gravid females and result in the aggregation of puparia. Behavioral studies withG. m. centralis showed that a higher percentage of females larviposited over moist sand conditioned by the anal exudate of larvae. Electroantennogram analyses of extracts of sand conditioned byG. m. centralis andG. m. morsitans confirmed the presence of olfactory receptors on the antennae for the semiochemicals. Both subspecies responded to extracts of the semiochemicals of the other, withG. m. morsitans more responsive to lower concentrations of extract ofG. m. centralis than the converse.     

Efficacy of the plant phototoxinα-terthienyl againstAedes intrudens and effects on nontarget organisms

The botanical phototoxin, -terthienyl (-T) was spray applied to natural or artificial pools containing mosquito (Aedes intrudens) larvae and nontarget invertebrates (caddisfly, damselfly, midge, shrimp,Daphnia, snail) and one vertebrate (trout) at concentrations varying from 0.01 to 1 kg/hectare, under field and laboratory conditions. All field-treated nontarget invertebrates survived -T treatment better thanA. intrudens which can be controlled at doses as low as 0.01 kg/hectare within one week. Under laboratory conditions, snails and trout survived -T and UV treatments up to 10 kg/ hectare. These results compare favorably with organophosphates and pyrethroid insecticides currently used for mosquito control. The results confirm that -T is a highly effective larvicide with acceptable nontarget effects.     

Quantity Does Matter: How Feces Are Used for Host Stage Selection by Granary Weevil Parasitoid Lariophagus distinguendus

The present paper examines the mechanisms of host stage selection in Lariophagus distinguendus, a larval parasitoid of the granary weevil Sitophilus granarius endophytic in wheat grain. The amount of host feces accumulating in infested grains was on average, 0.2, 0.3, 1.5, and 4 mg for first, second, third, and fourth instars, respectively. A maximum of 9 mg feces was found in grains with fourth instars. In bioassays with female parasitoids, only a little drumming and drilling behavior was observed on grain models treated with feces extract equivalent to 0.2 mg and 0.4 mg feces. Most drumming and drilling occurred on models with extracts equivalent to 4 and 8 mg feces. These results correspond to literature data demonstrating that older host larvae (fourth instars) are preferred for oviposition. Thus, host stage selection in L. distinguendus is apparently achieved by assessing the quantity of feces present in infested grains.     

Evidence for a Host-Marking Pheromone in White Spruce Cone Fly, Strobilomyia neanthracina

Cone flies (Strobilomyia spp.) lay eggs on coniferous cones, and larvae must complete development within the cone on which the eggs are laid. Previous field surveys showed that egg distributions of several species are uniform, suggesting that females avoid ovipositing on cones with conspecific eggs or larvae. In both the field and laboratory, S. neanthracina females walked around cones following oviposition, touching their mouthparts to the cone as they walked. In laboratory bioassays, where females were presented with a cone on which they or another female had oviposited and touched with mouthparts, or one without an egg, females laid preferentially on cones without eggs. However, females laid randomly when presented with a cone on which a female had oviposited but been prevented from touching with her mouthparts following oviposition or another cone without an egg. This indicates that females deposit a host-marking pheromone with their mouthparts following oviposition and that this deters further oviposition on marked hosts. Laboratory and field bioassays indicated that the host-marking pheromone is located in the head and thorax of female flies.