Effects of chickens on the prevalence of infestation and population density of Triatoma infestans in rural houses of north-west Argentina

Abstract Effects of the presence of chickens on population density of the bug Triatoma infestans , principal vector of Chagas disease, were investigated by standardized sampling (indoors and peridomestically) from sixty-eight houses of three rural communities in north-west Argentina, during March 1992.
The domiciliary density of T. infestans increased linearly with the percentage of bugs that fed on chickens, as identified by agar double-diffusion tests. Bug density was significantly higher in houses where hens usually nested indoors than in those where they did not, as determined by concurrent direct observations and interviews of householders. Multiple linear regression analysis of domiciliary bug density on (a) the total number of people, dogs and cats per house; (b) the percentage of domiciliary bugs that fed on chickens, or (c) the indoor-brooding habit of hens, showed the two variables (b, c) related to chickens as significant predictors in each regression model. Inclusion both variables representing chickens increased the fit significantly. Addition of other potentially confounding factors (domestic insecticide use, type of roof and walls of house) did not affect the significant variables retained in the best-fitting regression model.
Peridomestic infestation was positively associated with the household number of fowls. Chickens were the main bloodmeal source of peridomestic T.infestans populations. Human-fed bugs were detected in peridomestic sites of sixteen houses, indicating active dispersal of adults and large nymphal instars from bedroom areas.
Exclusion of hens from domiciliary areas and promotion of chicken sheds, of an appropriate design that would not harbour bug populations, should limit the triatomine population growth rate and reduce the risk of infestation.     

Homology of Holocene ostracode biramous appendages with those of other crustaceans: the protopod, epipod, exopod and endopod

Unambiguously biramous appendages with a proximal precoxa, well-defined coxa and basis, setose plate-like epipod originating on the precoxa, and both an endopod and exopod attached to the terminal end of the basis are described from several living Ostracoda of the order Halo-cyprida (Myodocopa). These limbs are proposed as the best choice for comparison of ostracode limbs with those of other crustaceans and fossil arthropods with preserved limbs, such as the Cambrian superficially ostracode-like Kunmingella and Hesslandona. The 2nd maxilla of Metapolycope (Cladocopina) and 1st trunk limb of Spelaeoecia, Deeveya and Thaumatoconcha (all Halocypridina) are illustrated, and clear homologies are shown between the parts of these limbs and those of some general crustacean models as well as some of the remarkable crustacean s.s. Orsten fossils. No living ostracodes exhibit only primitive morphology; all have at least some (usually many) derived characters. Few have the probably primitive attribute of trunk segmentation (two genera of halocyprid Myodocopa, one order plus one genus of Podocopa, and the problematic Manawa); unambiguously biramous limbs are limited to a few halo-cyprids. Homologies between podocopid limbs and those of the illustrated primitive myodocopid limbs are tentatively suggested. A setose plate-like extension, often attached basally to a podocopid protopod, is probably homologous to the myodocopid epipod, which was present at least as early as the Triassic. Somewhat more distal, less setose, and plate-like extensions, present on some podocopid limbs (e.g., mandible), may be homologous instead to the exopod (clearly present on myodocopid mandibles). The coxa (or precoxa) is by definition the most basal part of the limb. A molar-like tooth is present proximally on the mandibular protopod of many ostracodes; it is the coxal endite and projects medially from the coxa (or proximal protopod). The Ostracoda is probably a monophyletic crustacean group composed of Myodocopa and Podocopa. All have a unique juvenile (not a larva) initially with three or more limbs. Except that juveniles lack some setae and limbs, they are morphologially similar to the adult. Thus the following suite of characters in all instars may be considered a synapomorphy uniting all Ostracoda: (1) Each pair of limbs is uniquely different from the others. (2) The whole body is completely enclosed within a bivalved carapace that lacks growth lines. (3) No more than nine pairs of limbs are present in any instar. (4) The body shows little or no segmentation, with no more than ten dorsally defined trunk segments. No other crustaceans have this suite of characters. A probable synapomorphy uniting the Podocopa is a 2nd antenna with exopod reduced relative to the endopod.     

Evolutionary Analyses of Morphological and Physiological Plasticity in Thermally Variable Environments

SYNOPSIS. Morphological and physiological plasticity is oftenthought to represent an adaptive response to variable environments.However, determining whether a given pattern of plasticity isin fact adaptive is analytically challenging, as is evaluatingthe degree of and limits to adaptive plasticity. Here we describea general methodological framework for studying the evolutionof plastic responses. This framework synthesizes recent analyticaladvances from both evolutionary ecology and functional biology,and it does so by integrating field experiments, functionaland physiological analyses, environmental data, and geneticstudies of plasticity. We argue that studies of plasticity inresponse to the thermal environment may be particularly valuablein understanding the role of environmental variation in theevolution of plasticity: not only can thermally-relevant traitsoften be mechanistically and physiologically linked to the thermalenvironment, but also the variability and predictability ofthe thermal environment itself can be quantified on ecologicallyrelevant time scales. We illustrate this approach by reviewinga case study of seasonal plasticity in the extent of wing melanizationin Western White Butterflies (Pontia occidentalis). This reviewdemonstrates that 1) wing melanin plasticity is heritable, 2)plasticity does increase fitness in nature, but the effect variesbetween seasons and between years, 3) selection on existingvariation in the magnitude of plasticity favors increased plasticityin one melanin trait that affects thermoregulation, but 4) themarked unpredictability of short-term (within-season) weatherpatterns substantially limits the capacity of plasticity tomatch optimal wing phenotypes to the weather conditions actuallyexperienced. We complement the above case study with a casualreview of selected aspects of thermal acclimation responses.The magnitude of thermal acclimation ("flexibility") is demonstrablymodest rather than fully compensatory. The magnitude of geneticvariation (crucial to evolutionary responses to selection) inthermal acclimation responses has been investigated in onlya few species to date. In conclusion, we suggest that an understandingof selection and evolution of thermal acclimation will be enhancedby experimental examinations of mechanistic links between traitsand environments, of the physiological bases and functionalconsequences of acclimation, of patterns of environmental variabilityand predictability, of the fitness consequences of acclimationin nature, and of potential genetic constraints.     

Locomotory mechanisms in Antarctic pycnogonids

Patterns of walking, modes of joint movement, and individual limb diversity were analysed with the aid of ciné film of several living Antarctic pycnogonids, including the 8-legged Colossendeis australis, C. angusta, Pallenopsis patagonica , and Nymphon sp., the 10-legged Decolopoda australis , and the 12-legged Dodecolopoda mawsoni. Appendage musculature of several of these species and also of the 10-legged Pentapycnon charcoti and Pentanymphon antarcticurn was dissected. At least two distinct morphotypes were identified: a short-legged, crawling variety ( P. charcoti ); and the more typical long-legged, large bodied, walking forms. No gross differences in musculature of joints were noted in the species examined. All joints are, at least superficially, hinge joints. The coxa-body joint is largely immobile, the coxa 1-coxa 2 joint alone exhibits promotion-remotion and all other joints are flexion-extension joints. The 8-legged forms move in an imprecise manner, there being irregularity of leg raising and lowering and where legs touch down in relation to the body and to other legs. The 10- and 12-legged forms exhibit more precise patterns of metachronal leg movements. Although legs move in a basic promotion-remotion, extension-flexion mode, there is a certain degree of twisting of a leg as it is picked up, brought forward, and set down; models indicating how such joint movement occurs were constructed. The possibility that hydrostatic pressure is employed in extension is considered and is found to be remote. Lateral placement of legs, orientated in almost all directions in the horizontal plane of the trunk, achieves a versatility of movement similar to that in crabs. Comments on pycnogonid taxonomic affinities are offered.     

Isolation and characterization of 13 polymorphic microsatellite loci from the clam shrimp Eulimnadia texana (Crustacea: Spinicaudata)

Thirteen polymorphic microsatellite loci were isolated and characterized from the clam shrimp Eulimnadia texana. In analyses of 20–50 individuals from two populations the number of alleles ranged from two to seven with observed heterozygosity ranging between 0.00 and 0.37. The low values for heterozygosity were not unexpected for a group characterized by its unusual androdioecious mating system, in which males compete with self‐compatible hermaphrodites for offspring production. These microsatellites are likely to be useful for further evolutionary investigations of this rare mating system in these crustaceans.     

Redescription of the clam shrimp Lynceus gracilicornis (Packard) (Branchiopoda, Conchostraca, Lynceidae) from Florida, with notes on its biology

Clam shrimps of the family 1.ynccidac differ markedly from all other families of the Conchostraca. The biology and morphology of the genus Lynceus are poorly known. In North America the genus is represented by four species: L. brachyurus, L. mucronatus, L. brevifrons and L. grarcilicornis. The last species, previously known from two localities in Texas, is reported from an ephemeral pond in north Florida. Amoung the characters distinguishing L. gracilicornis from North American congeners arc dimorphic male claspers and a broad, straight rostral margin. Females are distinct in having a smoothly rounded, distal rostra1 margin. External and internal morphology are described using light and scanning electron microscopy. Scanning electron microscopy reveals the presence of frontal setose sensory fields and a small rostral pit in both sexe5. Numerous setal types are described from the claspers and posterior thoracopods. Internal structures include a large anterior hepatopancreas, C-shaped gut and large paired gonads ventro-lateral to the gut.     

The Use of Functional and Adaptive Criteria in Phylogenetic Systematics

SYNOPSIS. The controversy over whether functional data can contributeto phylogenetic inference has grown in recent years. Steps canbe taken toward its resolution if the relevance of functionaldata is judged for each component of phylogenetic analysis.These components are (1)recognizing of basic taxa (species orsupraspecific taxa), (2) formulating hypotheses of homologyfollowed by character analysis, (3) evaluating character phylogeny,(4) formulating phylogenetic hypotheses, and (5) evaluatingalternative phylogenetic hypotheses. It can be shown that functionaldata do not play a necessary or unique role in any of thesecomponents of phylogenetic analysis. Arguments to the contraryhave failed to provide a rigorous, repeatable methodto incorporatefunctional data; proponents of a functional approach to phylogeneticreconstruction rely too often on subjective, authoritarian argumentation. Students of functional evolutionary morphology frequently havefailed to understand the kinds of information necessary to studyor apply the causal process of adaptation via natural selection.This information, required by the very nature of the theoryitself, includes knowing the pattern of heredity of the phenotypiccharacters being studied, relating intrapopulational phenotypicvariability to variation in fitness, and knowing a sufficientamount about population structure to specify the componentsof natural selection. Studies within functional evolutionarymorphology are not designed to satisfy these requirements. Functionalevolutionary morphology uses the concepts of adaptation andnatural selection axiomatically, and thus such studies contributenothing to our understanding of the evolutionary process becausehypotheses about that process are not being evaluated. Thisalso suggests that, if functional evolutionary morphology wishesto engage in analyses of the evolutionary dynamics of the phenotype,a reorientation of its research strategy and goals will be necessary.     

The effects of water on patch use by two Simpson Desert granivores (Corvus coronoides and Pseudomys hermannsburgensis)

Abstract Water loss while foraging may affect the overall value of food to desert animals. When water is scarce, foragers may alter activity and shun certain types of food due to elevated water loss. When water is abundant, foragers can exploit food patches more thoroughly and remain active over a broader range of ambient conditions. In short, food and water may be complementary resources. The presence of water raises the marginal value of food, particularly those foods low in water content. We tested for the complementarity of food and water to foragers at a sand dune site in the Simpson Desert of arid Australia. To do so, we quantified patch exploitation of foragers in the presence or absence of bowls filled with water. In order to quantify patch use, we provisioned feeding trays with granulated peanuts mixed into a sand substrate. In these trays we measured giving-up densities (GUD; the amount of food left in a tray after a foraging bout) of diurnal (mostly Australian ravens, Corvus coronoides) and nocturnal foragers (mostly sandy inland mouse, Pseudomys hermannsburgensis). The presence of water affected the GUD of ravens but not of rodents. For the ravens, GUD dropped about 50% in response to added water. For ravens, water and food are strongly complementary. In addition, ravens had lower GUD in the open than the bush microhabitat, and lower GUD at the bottom than the tops of sand dunes.     

Amino Acid Activation in Subcellular Fractions of Tetrahymena pyriformis*

SYNOPSIS. The presence of amino acid activating enzymes was demonstrated in the ciliated protozoan Tetrahymena pyriformis. By employing a sensitive hydroxamate assay procedure, the activation of L-valine was assayed in various subcellular fractions of the ciliate, and some characteristics of the enzyme activity in the most active fraction were determined. Most of the activity resided in pH 5 fractions isolated from high speed supernatants of ciliates disrupted by various physical and chemical methods. No activity could be demonstrated in isolated cilia, in pellicles with attached kinetosomes, in microsomes or in macronuclei, providing these organelles were thoroughly washed. A washed mitochondrial preparation isolated by the Mager and Lipmann procedure activated L-valine; mitochondria isolated by the procedure of Hogg and Kornberg did not. The pH 5 fraction isolated from the 102,000 X g supernatant of digitonin-lysed ciliates was stable for several weeks when stored in 0.1 M Tris buffer, pH 7.6 at – 25 C. The activity of this fraction with respect to L-valine activation was dependent on the presence of ATP¹ and magnesium in the reaction mixture. The optimal concentrations of these components and of L-valine and hydroxylamine were determined, and the linearity of activity with time and enzyme concentration was demonstrated. Valine activation was not modified by dialysis of the pH 5 fraction, or treatment with RNase, or the addition of boiled pH 5 fraction.