Determinants of parasite distribution in Arctic charr populations: catchment structure versus dispersal potential.

Parasite distribution patterns in lotic catchments are driven by the combined influences of unidirectional water flow and the mobility of the most mobile host. However, the importance of such drivers in catchments dominated by lentic habitats are poorly understood. We examined parasite populations of Arctic charr Salvelinus alpinus from a series of linear-connected lakes in northern Norway to assess the generality of lotic-derived catchment-scale parasite assemblage patterns. Our results demonstrated that the abundance of most parasite taxa increased from the upper to lower catchment. Allogenic taxa (piscivorous birds as final host) were present throughout the entire catchment, whereas their autogenic counterparts (charr as final hosts) demonstrated restricted distributions, thus supporting the theory that the mobility of the most mobile host determines taxa-specific parasite distribution patterns. Overall, catchment-wide parasite abundance and distribution patterns in this lentic-dominated system were in accordance with those reported for lotic systems. Additionally, our study highlighted that upper catchment regions may be inadequate reservoirs to facilitate recolonization of parasite communities in the event of downstream environmental perturbations.

Hiding in the swamp: new capillariid nematode parasitizing New Zealand brown mudfish.

The extent of New Zealand's freshwater fish-parasite diversity has yet to be fully revealed, with host-parasite relationships still to be described from nearly half the known fish community. While advances in the number of fish species examined and parasite taxa described are being made, some parasite groups, such as nematodes, remain poorly understood. In the present study we combined morphological and molecular analyses to characterize a capillariid nematode found infecting the swim bladder of the brown mudfish Neochanna apoda, an endemic New Zealand fish from peat-swamp-forests. Morphologically, the studied nematodes are distinct from other Capillariinae taxa by the features of the male posterior end, namely the shape of the bursa lobes, and shape of spicule distal end. Male specimens were classified into three different types according to differences in the shape of the bursa lobes at the posterior end, but only one was successfully characterized molecularly. Molecular analysis indicated that the studied capillariid is distinct from other genera. However, inferences about the phylogenetic position of the capillariid reported here will remain uncertain, due to the limited number of Capillariinae taxa characterized molecularly. The discovery of this new capillariid, which atypically infects the swim bladder of its host, which itself inhabits a very unique ecosystem, underlines the very interesting evolutionary history of this parasite, which for now will remain unresolved.

Do different parasite species interact in their effects on host fitness? A case study on parasites of the amphipod Paracalliope fluviatilis.

There is a gap in our understanding of the relative and interactive effects of different parasite species on the same host population. Here we examine the effects of the acanthocephalan Acanthocephalus galaxii, an unidentified cyclophyllidean cestode, and the trematodes Coitocaecum parvum and Microphallus sp. on several fitness components of the amphipod Paracalliope fluviatilis, using a combination of infection surveys and both survival and behavioural trials. In addition to significant relationships between specific parasites and measures of amphipod survival, maturity, mating success and behaviour, interactions between parasite species with respect to amphipod photophilia were also significant. While infection by either A. galaxii or C. parvum was associated with increased photophilia, such increases were negated by co-infection with Microphallus sp. We hypothesize that this is due to the more subtle manipulative effect of A. galaxii and C. parvum being impaired by Microphallus sp. We conclude that the low frequency at which such double infections occur in our sampled population means that such interactions are unlikely to be important beyond the scale of the host individual. Whether or not this is generally true, implying that parasitological models and theory based on single parasite species studies do generally hold, requires cross-species meta-analytical studies.

Parasite spillback: a neglected concept in invasion ecology?

While there is good evidence linking animal introductions to impacts on native communities via disease emergence, our understanding of how such impacts occur is incomplete. Invasion ecologists have focused on the disease risks to native communities through "spillover" of infectious agents introduced with nonindigenous hosts, while overlooking a potentially more common mechanism of impact, that of "parasite spillback." We hypothesize that parasite spillback could occur when a nonindigenous species is a competent host for a native parasite, with the presence of the additional host increasing disease impacts in native species. Despite its lack of formalization in all recent reviews of the role of parasites in species introductions, aspects of the invasion process actually favor parasite spillback over spillover. We specifically review the animal-parasite literature and show that native species (arthropods, parasitoids, protozoa, and helminths) account for 67% of the parasite fauna of nonindigenous animals from a range of taxonomic groups. We show that nonindigenous species can be highly competent hosts for such parasites and provide evidence that infection by native parasites does spillback from nonindigenous species to native host species, with effects at both the host individual and population scale. We conclude by calling for greater recognition of parasite spillback as a potential threat to native species, discuss possible reasons for its neglect by invasion ecologists, and identify future research directions.

The carriage of Streptococcus suis type 2 by pigs in Papua New Guinea.

An indirect fluorescent antibody test was used to detect the presence of Streptococcus suis type 2 in nasal and pharyngeal swabs taken from pigs in Papua New Guinea. The rate of carriage for the two sites in domesticated indigenous village pigs was 0.5 and 2.5% respectively, compared to 39 and 43% for intensively reared pigs. These findings were supported by the results of a serological survey, using an enzyme linked immunosorbent assay, in which 87% of intensively reared pigs but only 8% of village pigs were seropositive to S. suis type 2. It is proposed that in intensive piggeries S. suis type 2 is continually cycled between pigs. In village pigs, the low population density and harsh environmental conditions prevents this cycle of infection.

Xanthone additives for blood storage that maintain its potential for oxygen delivery. I. 2-Hydroxyethoxy- and 2-ethoxy-6-(5-tetrazoyl) xanthones in citrate-phosphate-dextrose-adenine (CPDA-1) blood.

Two xanthones, 2-hydroxyethoxy-6-(5-tetrazoyl) (BW A440C) and 2-ethoxy-6-(5-tetraozyl) (BW A827C), are members of a chemical series tested in vitro as potential additives to citrate-phosphate-dextrose-adenine (CPDA-1) medium for blood storage. P50 was maintained in the presence of these compounds during 42 days' storage by a partial maintenance of 2,3 diphosphoglycerate (2,3 DPG) and by a direct effect on hemoglobin previously reported for BW A827C. Red cell 2,3 DPG levels for BW A440C (n = 5), BW A827C (n = 5), and control (n = 6), respectively, were 3.38 +/- 0.47, 3.44 +/- 0.25, and 1.20 +/- 0.10 mM +/- SEM on day 7; 1.16 +/- 0.13, 1.52 +/- 0.37, and 0.16 +/- 0.02 mM on day 21; and 0.67 +/- 0.09, 0.61 +/- 0.08, and 0.06 +/- 0.006 mM on day 42. Red cell adenine triphosphate levels at the same time intervals were 1.84 +/- 0.09, 1.46 +/- 0.18, and 2.11 +/- 0.04 mM; 2.10 +/- 0.05, 2.07 +/- 0.17, and 2.13 +/- 0.05 mM; and 1.42 +/- 0.13, 1.37 +/- 0.13, and 1.38 +/- 0.06 mM, respectively. The degree of hemolysis was less with the addition of the compounds, and the methemoglobin formation, plasma Na+ and K+, and lactate production were unaffected by the compounds.

Caesarean section for twins in a patient with myotonic dystrophy.

The management of a patient with myotonic dystrophy undergoing Caesarean section for delivery of twins in breech position is reported. Anaesthetic management must reflect the multi-system nature of the disease in addition to the implications of pregnancy. Known triggers of myotonic crisis (succinylcholine, shivering) must be avoided. Attention to respiratory reserve is necessary in view of the restrictive defect this disease can impose. Cardiomyopathy and conduction system disturbances may be features. Upper gastrointestinal incoordination can superimpose the added risk of aspiration on the pregnant myotonic. Ineffective uterine contraction can cause vigorous post partum haemorrhage. Endocrine disturbances, especially diabetes mellitis, may be present. There may be increased sensitivity to sedative and narcotic agents. The newborn myotonic will need the expertise of neonatal care.

The effect of 2,3-diphosphoglycerate on the oxygen dissociation curve of human haemoglobin.

1. Oxygen dissociation curves for concentrated human haemoglobin solutions (1.6 mmol dm-3 in haem) have been measured by mixing known quantities of oxy- and deoxyhaemoglobin solutions and measuring the resulting partial pressure of oxygen with an oxygen electrode. 2. Observations in the presence of 2,3-diphosphoglycerate support previous conclusions derived from experiments at low haemoglobin concentrations, the validity of which has been questioned. 3. The two affinity state model of Monod, Wyman & Changeux (1965) does not fully describe the actions of 2,3-diphosphoglycerate and a model in which this allosteric effector not only binds preferentially to the T state but also lowers the oxygen affinity of this state gives an improved fit to the data.

Mineralocorticoid receptors in sheep kidney and parotid: studies in Na+ replete and Na+ deplete states.

1. As an adrenalectomized sheep becomes progressively more Na+ deplete, its salivary electrolyte secretion becomes increasingly sensitive to exogenous aldosterone administration. 2. Alteration in mineralocorticoid receptor affinity or concentration is a possible mechanism whereby this sensitivity could be expressed at a molecular level. 3. Bonding sites with a high affinity for aldosterone (Kd 37 degrees C approximately 5 x 10(-10) M) have been demonstrated in sheep kidney and parotid. 4. Renal binding sites were examined in detail, and shown to have affinity characteristics appropriate for mineralocorticoid receptors (aldosterone greater than deoxycorticosterone greater than dexamethasone greater than cortisol greater than progesterone greater than oestradiol greater than dihydrotestosterone). 5. No difference in mineralocoticoid receptor affinity or concentration could be shown between Na+ replete and Na+ deplete sheep, in either kidney or parotid gland. 6. Accordingly, the molecular mechanisms whereby parotid sensitivity is mediated remain as yet undefined.