Population genetics ofAnisakis simplex (Nematoda: Ascaridoidea) in Atlantic salmon (Salmo salar) and their use as biological indicators of host stocks

Synopsis The extent to which data concerning the population genetics of a parasite — namely larvalAnisakis simplex, may be used as an auxilliary source of information on various aspects of the marine migrations of Atlantic salmon (Salmo salar) is examined.Frequencies of the various acid phosphatase alleles could not be used in distinguishing between or estimating the proportions of North American and European salmon occurring off west Greenland. The genetic structure of larvae from salmon taken in Scotland was different from that taken in Ireland and England confirming an earlier conclusion that the feeding habits of the fish from Scotland were significantly different. In the western Atlantic, salmon from northern Newfoundland and also salmon from the Bay of Fundy had apparently ingested different populations (or different proportions of the same nematode population) than salmon from Miramachi and Chaleur Bay areas. Samples from northern Newfoundland and Labrador were also genetically different. These findings are discussed in relation to the available literature concerning salmon migrations, explanations are put forward and areas of future research suggested.     

Host-attacking behavior of a eulophid parasite,Kratochviliana sp., to the leaf mining host,Phytomyza ranunculi (Diptera: Agromyzidae) during its stay on the leaf

The present paper studies how the female parasite of Kratochviliana sp. visits and attacks its host larvae of Ranunculus leaf mining fly, P. ranunculi at a single leaf visit. The parasite visited its hosts at random on the leaf. The frequency of host visits was independent of the host density and the proportion of hosts survived from the parasite attack, in a leaf and its distribution was expressed as a single straight line. It almost always attacked living hosts at the first host visit after isolated from them for one day but with the rate of about 0.5 at the subsequent visits. In consequence, the relationships of the number of host attacks and killed hosts to the host density drew satulated curves in each. A model of host attack by this parasite at its single leaf visit was formulated by modifyingBakker et al.'s model (1972) basing upon these observations and the attack avoidance by the parasite to already attacked hosts previously reported.     

Dictyocaulus viviparus: Migration in agar of larvae subjected to a variety of physicochemical exposures

Dictyocaulus viviparus larvae were exposed to ox bile and CO₂ at intervals during their cultivation to the infective stage. Preinfective and young infective larvae were stimulated by CO₂. Bile slightly inhibited preinfective larvae, but stimulated the infective stage. Old coiled, resting infective larvae were stimulated by bile down to a concentration of 10 ppm of bile dry matter, by vertebrate biles of pig, sheep, newborn calf, cow, guinea pig, dog, and chicken, as well as by defatted bile dry matter and by glyco-, tauro-, glycodeoxy-, and taurodeoxycholates. Continuous bile exposure appeared necessary to maintain high larval activity. A high pCO₂ as well as a low redox potential potentiated the effect of bile, but had no effect alone. Exposure to pepsin-HCl and to trypsin had only a minor stimulatory effect.     

Population dynamics of the swallowtail butterfly,Papilio xuthus L., in a deforested area

The long-term population dynamics of the swallowtail butterfly, Papilio xuthus, were studied by means of life table analysis in a deforested area, where the host tree, Zanthoxylum ailanthoides, was growing. The number of eggs laid on host trees in the deforested area decreases as secondary succession progresses. When the trees were classified into three groups, i. e. tall, medium and short, according to their height relative to the surrounding vegetation, less eggs were laid on tall than on short host trees. Life tables for the natural populations in each generation were developed on the basis of mean values for 6 years. Eggs and larvae in early stages were attacked chiefly by small- and middle-sized predators, such as ants, spiders, bugs and orthopterids, while later stage larvae were attacked chiefly by birds or Polistes wasps. An inchneumonid wasp was the most important mortality factor in the pupal stage. Key-factor analysis was tested on the life table data of each immature stage. The late larval stage was a key stage, and most mortality factors were considered to operate independently. The test for density dependency did not show any tendencies. The analysis of variance in two-way classifications was carried out for the difference of survival rate among the tree groups. It was suggested that tall host trees were unsuitable for P. xuthus. The construction of life tables for artificially inoculated populations on large host trees showed that high physiological death rate were characteristic of such trees in comparison with natural populations on smaller trees. The characteristics of the population dynamics of P. xuthus in the deforested area are compared among some kinds of the habitat, and the interrelationship between P. xuthus and its host plant are discussed.     

Flight responses in a wind tunnel of the parasitoid Microplitis croceipes to three spring and three summer host plants of Heliothis spp.

Flight responses of the parasitoid, Microplitis croceipes (Cresson) (Hymenoptera: Braconidae) to two phenological stages of spring host plants (crimson clover, Trifolium incarnatum L., hairy vetch, Vicia villosa Corbiere, and cutleaf geranium, Geranium dissectum L.) and summer host plants (cotton, Gossypium hirsutum L., sorghum, Sorghum bicolor L., and soybean Glycine max (L.) Merr.) of Heliothis virescens (F.), were measured in a dual choice situation in a wind tunnel. Preflowering clover was more attractive than preflowering geranium, followed by preflowering vetch. Clover was preferred over geranium in flowering stages as well. No within species differences were detected for the two phenological stages. Preflowering and flowering cotton and soybean were preferred over preflowering and flowering sorghum. The findings could be important in pre-determining release sites for M. croceipes in the field.     

Occurrence and performance of the aspen blotch miner,Phyllonorycter salicifoliella,on three host-tree species

Summary Larvae of the aspen blotch miner, Phyllonorycter salicifoliella Chambers (Lepidoptera: Gracillariidae), feed within leaves of three host-tree species in north-central Minnesota, USA. Far more individuals occur on Populus tremuloides than on P. balsamifera or P. grandidentata. We tested whether this pattern of host use reflected variable performance among alternative hosts by examining survivorship, sources of mortality, pupal mass, feeding efficiency, and development time of miners on each tree species. We also determined foliar water, nitrogen, condensed tannin, and phenolic glycoside content of host trees to test if host-tree chemical attributes were responsible for differences in performance. There was no significant difference in egg-to-adult survival among miners on different hosts, although dominant sources of mortality did vary. Miners on P. grandidentata suffered less parasitism and more predation than those on the other hosts, even though most parasitoid species attacked miners on all hosts. The other performance parameters varied among host species, but not in a consistent pattern. Pupal mass was greatest on P. tremuloides and P. balsamifera, the hosts with comparatively high foliar nitrogen and low phenolic glycoside concentrations. However, feeding efficiency was greatest and development time shortest for miners on P. grandidentata. Thus, pupal mass was the only index of performance maximized on P. tremuloides, the most commonly used host. Infrequent occurrence of Phyllonorycter salicifoliella on P. grandidentata results in part from phenological differences between this and the other host species. Low oviposition rates on P. balsamifera are correlated with low abundance of this host at the study site and a phenolic glycoside profile different from that of the other host species.     

Physiological responses of Uroleucon jaceae (L.) to seasonal changes in the quality of its host plant Centaurea jacea L.: multilevel control of adaptations to the life cycle of the host

Summary Exploiters of short-lived plants have evolved strategies in response to physiological changes that occur during the development of their hosts. The ability to adapt to host quality changes is necessary particularly if the mobility of an animal is poor or risk-constrained. In the plant-aphid system Centaurea jaceae-Uroleucon jaceae, the responses of the aphid to the seasonal changes in its host plant grown in poor and good quality soil were investigated. Coarse- and fine-tuned physiological reactions were observed in discrete aphid generations which were reared on plants grown either in a growth chamber or in a greenhouse. The number of ovarioles and developmental time depended on extrinsic factors (length of photoperiod) not directly related to plant quality. The reproductive investment of the aphids was also independent of their total dry weight. However, within the gonadal system high correlations were found at the embryonic level (e.g. the number of sclerotized embryos or the length of the oldest embryos per ovariole were highly correlated with gonadal dry weight). Aphids which were living on the 4-leaf stage of high-quality host plants showed a significantly higher investment in their gonads than aphids feeding on senescenting hosts. Factor analysis corroborated that aphids reared on poor-quality hosts revealed no grouping of variables measured, whereas those which were reared on high-quality plants showed clustering in respect of somatic (tibia length, dry weight of soma) and gonadal (number of sclerotized and unsclerotized embryos, length of the oldest embryos, ovariole number, gonad dry weight) factors. Three different levels of adaptive response to plant quality are distinguished: individual response to host quality, maternal influences on offspring and response to changes not specific to habitat (photoperiod). These different levels of regulation are thought to enable the aphids to adapt to a host of a given nutritional quality and anticipate deteriorating habitat quality simultaneously. It is concluded that physiological constraints in aphids are only revealed when aphids are exposed to severe nutritional stress for several generations.     

Host selection behavior of a thistle-feeding fly: choices and consequences

Summary Female Canada thistle seed flies (Orellia ruficauda) preferentially oviposit into seed heads which are a single day from opening. When flies are forced to oviposit into flower heads at other stages of development, offspring typically do slightly poorer: they attain a mature mass of about 15% less than do larvae derived from preferred hosts. Larval mass correlates strongly with reproductive success: heavy larvae develop into adults that produce eggs at a faster rate than do those developing from small larvae. After laying a clutch of eggs, flies circumscribe the rim of the flowerhead with their extended ovipositor and deposit a clear fluid. Flies reject previously-attacked hosts, bearing this apparent marking pheromone, significantly more often than they reject unattacked hosts. Costs of superparasitism in this system are relatively small, inasmuch as there is only a weak relationship between clutch size and larval success at the densities measured in this study. We speculate that flies are highly selective, when the apparent costs of making a mistake are rather low, because the information provided by phenological cues and by the putative marking pheromone is highly reliable, and low fecundity and time costs allow sufficient time to express a high level of discrimination.     

Solvent effects on biocatalysis in organic systems: equilibrium position and rates of lipase catalyzed esterification

Porcine pancreatic lipase immobilized on celite particles has been employed as a catalyst for the esterification of dodecanol and decanoic acid in a predominantly organic system. Solvent influence on the equilibrium position and on the catalyst activity has been studied using 20 solvents, including aliphatic and aromatic hydrocarbons, ethers, ketones, nitro- and halogenated hydrocarbons, and esters. The equilibrium constant for esterification correlates well with the solubility of water in the organic solvent, which in turn shows a good relationship with a function of Guttman's donor number and the electron pair acceptance index number of the solvent. This may be rationalized in terms of the requirements for solvation of water and of the reactants. The catalyst activity, measured as the initial rate of the esterification reaction, is best correlated as a function of both n-octanol-water partition coefficient (log P) and either the electron pair acceptance index or the polarizability.     

Ixodes dammini: Induced skin lesions in guinea pigs and rabbits compared to erythema chronicum migrans in patients with lyme arthritis

Erythematous skin lesions occurred in rabbits 2 days after being fed upon by larvae or nymphs of the tick, Ixodes dammini. Similar lesions occurred in guinea pigs 7 days after a primary infestation with either larvae or nymphs. Host resistance to secondary feeding by larvae was demonstrated in guinea pigs and rabbits. Host resistance to secondary feeding by nymphs was seen in guinea pigs, but not in rabbits. Guinea pigs developed resistance to nymphs after being previously fed upon twice by larvae. All skin lesions in resistant guinea pigs contained large accumulations of basophils (49–76% of cells) with smaller (20–33%), but significant, numbers of eosinophils. These responses were characteristic of strong cutaneous basophil hypersensitivity reactions. Primary and secondary lesions in rabbits fed upon by larvae contained mostly mononuclear cells (46–52%) and moderate numbers (16–30%) of basophils and eosinophils. Primary and secondary lesions in rabbits fed upon by nymphs had few (3–11%) basophils and eosinophils and were dominated by mononuclear cells (73–86%). Thus, acquired resistance in guinea pigs and rabbits was associated with cutaneous basophil and eosinophil responses and the lack of resistance of rabbits to nymphs was associated with erythematous lesions dominated by mononuclear cells. The mononuclear nature of rabbit lesions induced by nymphal feeding was similar to that seen in erythema chronicum migrans in Lyme arthritis patients who are thought to have been fed upon by I. dammini nymphs. This study confirms the cutaneous basophil hypersensitivity characteristics of lesions in guinea pigs resistant to ticks and demonstrates a relationship between the mononuclear cell response of rabbits to nymphal I. dammini and the cellular response seen in patients with erythema chronicum migrans and Lyme arthritis.