Patterns of variation in tail ornament size in birds

In recent years several different kinds of sexual selection models have been developed, and tail ornaments in birds have frequently been used as an example of a sexually selected character where the models might apply. However, very little is known about intra- and interpopulation variation in ornament size. We have studied the elongated tail ornaments in four species of whydahs Vidua , the forktailed flycatcher Tyrannus savana and the Asian paradise flycatcher Terpsiphone paradisi. Ornaments were relatively longer in males with the longest tarsi ('heterogony' with positive allometry). Also, tail lengths were remarkably variable within each geographical area, the coefficient of variation (average = 11%) being three times as high as for body size characters. Models, with female preference of ornaments bearing no relation to male viability, usually generate lines of neutral equilibria. Thus, they predict extraordinary variation in ornaments between populations. However, elongated tail ornaments did not show higher geographical variation than the body size characters, suggesting that there is no line of equilibria for these ornaments.     

Cannibalism and Coprophagy Are Modes of Transmission of Blastocrithidia triatomae (Trypanosomatidae) between Triatomines

Transovarial transmission was not detectable among Blastocrithidia triatomae- infected Triatoma infestans . Rather, B. triatomae was transmitted directiy between triatomines by cannibalism and coprophagy. Cannibalism conditions that excluded coprophagy always resulted in an infection of Dipetalogaster maxima . The efficiency of transmission was not influenced by the blood source—mice or chickens—fed to the infected donor bugs although chicken blood lyses the epimastigotes of the stomach population. Triatoma infestans was infected by coprophagy only if fed, not if unfed. Blastocrithidia triatomae in dry feces was taken up only if the feces were redissolved in fresh feces. Infections also appeared in groups of bugs fed on chickens previously used for feeding infected bugs.     

Reconstructing the past density of planktivorous fish and trophic structure from sedimentary zooplankton fossils: a surface sediment calibration data set from shallow lakes

1. As quantitative information on historical changes in fish community structure is difficult to obtain directly from fish remains in lake sediments, transfer function for planktivorous fish abundance has been developed based on zooplankton remains in surface sediment (upper 1 cm). The transfer function was derived using weighted average regression and calibration against contemporary data on planktivorous fish catch per unit effort (PF-CPUE) in multiple mesh size gill nets. Zooplankton remains were chosen because zooplankton community structure in lakes is highly sensitive to changes in fish predation pressure. The calibration data set consisted of thirty lakes differing in PF-CPUE (range 18–369 fish net^–1), epilimnion total phosphorus (range 0.025–1.28 mg P l^–1) and submerged macrophyte coverage (0–57%). 2. Correlation of log-transformed PF-CPUE, total phosphorus and submerged macrophyte coverage v the percentage abundance in the sediment of the dominant cladocerans and rotifers revealed that the typical pelagic species correlated most highly to PF-CPUE, while the littoral species correlated most highly to submerged macrophyte coverage. Consequently, only pelagic species were taken into consideration when establishing the fish transfer function. 3. Canonical correspondence analysis (CCA) revealed that the pelagic zooplankton assemblage was highly significantly related to PF-CPUE (axis 1), whereas the influence of total phosphorus and submerged macrophyte coverage was insignificant. Predicted PF-CPUE based on weighted average regression without (WA) and with (WA(tol)) downweighting of zooplankton species tolerance correlated significantly with the observed values (r² = 0.64 and 0.60 and RMSE = 0.54 and 0.56, respectively). A marginally better relationship (r² = 0.67) was obtained using WA maximum likelihood estimated optima and tolerance. 4. It is now possible, quantitatively, to reconstruct the historical development in planktivorous fish abundance based on zooplankton fossil records. As good relationships exist between contemporary PF-CPUE data and indicators such as the zooplankton/phytoplankton biomass ratio, Secchi depth and the maximum depth distribution of submerged macrophytes, it is now also possible to derive information on past changes in lake water quality and trophic structure. It will probably prove possible further to improve the transfer function by including other invertebrate remains, e.g. chironomids, Chaoborus, snails, etc., and its scope could be widened by including deeper lakes, more oligotrophic lakes, more acidic lakes and lakes with extensive submerged macrophyte coverage (in the latter case to enable use of the information in the fossil record on plant-associated cladocerans).     

Cladistic analysis of the Cirripedia Thoracica

We present a cladistic analysis of the Cirripedia Thoracica using morphological characters and the Acrothoracica and Ascothoracida as outgroups. The list of characters comprised 32 shell and soft body features. The operational taxonomic units (OTUs) comprised 26 well-studied fossil and extant taxa, principally genera, since uncertainty about monophyly exists for most higher ranking taxonomic units. Parsimony analyses using PAUP 3.1.1 and Hennig86 produced 189 trees of assured minimal length. We also examined character evolution in the consensus trees using MacClade and Clados. The monophyly of the Balanomorpha and the Verrucomorpha sensu stricto is confirmed, and all trees featured a sister group relationship between the ‘living fossil Neoverruca and me Brachylepadomorpha. In the consensus trees the sequential progression of ‘pedunculate‘sister groups up to a node containing Neolepas also conforms to current views, but certain well-established taxa based solely on plesiomorphies stand out as paraphyletic, such as Pedunculata (= Lepadomorpha); Eolepadinae, Scalpellomorpha and Chthamaloidea. The 189 trees differed principally in the position of shell-less pedunculates, Neoverruca, the scalpelloid Capitulum, and the interrelationships within the Balanomorpha, although the 50% majority rule consensus tree almost fully resolved the latter. A monophyletic Sessilia comprising both Verrucomorpha and Balanomorpha appeared among the shortest trees, but not in the consensus. A tree with a monophyletic Verrucomorpha including Neoverruca had a tree length two steps longer than the consensus trees. Deletion of all extinct OTUs produced a radically different tree, which highlights the importance of fossils in estimating cirripede phylogeny. Mapping of our character set onto a manually constructed cladogram reflecting die most recent scenario of cirripede evolution resulted in a tree length five steps longer than any of our shortest trees. Our analysis reveals that several key questions in cirripede phylogeny remain unsolved, notably the position of shell-less forms and the transition from ‘pedunculate‘to ‘sessile‘barnacles. The inclusion of more fossil species at this point in our understanding of cirripede phylogeny will only result in even greater levels of uncertainty. When constructing the character list we also identified numerous uncertainties in the homology of traits commonly used in discussing cirripede evolution. Our study highlights larval ultrastructure, detailed studies of early ontogeny, and molecular data as the most promising areas for future research.     

A simple water and plankton sampler

SUMMARY. A lightweight, free-flushing water and plankton sampler constructed of readily available, inexpensive material is described. Easily interchangeable tubes of varying volumes allow sampling flexibility. The sampler is activated by a messenger and is shut by two plastic funnels. For analyses in highly stratified waters, the sampler can be adjusted into the horizontal position. Several samplers may be tripped in series. The sampler has proved a versatile and reliable instrument in ecological studies.
The tripping mechanism may also be used to release reversing thermometers and closing nets.     

Stage-Dependent Effects of Chloroquine on Plasmodium falciparum In Vitro1

The erythrocytic developmental cycle of Plasmodium falciparum can be conveniently divided into the ring, trophozoite, and schizont stages based on morphology and metabolism. Using highly synchronous cultures of P. falciparum, considerable variation was demonstrated among these stages in sensitivity to chloroquine. The effects of timed, sequential exposure to several clinically relevant concentrations of chloroquine were monitored by three techniques: morphological analysis, changes in the rate of glucose consumption, and changes in the incorporation of ³H-hypoxanthine into parasite nucleic acids. All three techniques gave essentially identical results. The trophozoite and schizont stages were considerably more sensitive to the drug than ring-stage parasites. Chloroquine sensitivity decreased as nuclear division neared completion. The increase in chloroquine sensitivity was coincident with a marked rise in the rate of glucose consumption and nucleic acid synthesis. The rate of nucleic acid synthesis decreased as schizogony progressed while glucose consumption continued at high rates during this process. The degree of chloroquine sensitivity was not highly correlated with either metabolic activity.     

The distribution, abundance and host plant relationships of Salix- feeding psyllids (Homoptera: Psylloidea) in arctic Alaska

Abstract. 1. Five species of psyllid occurred on seven species of Salix at Meade River, Alaska. Studies were made on the two common species Psylla pclmeni Löw and P.phlebophyllae Hodkinson. The former feeds on the phanerophy tes Salix pulchra, S.lanata, S.alaxensis and S.glauca , the latter on the chamaephytes S.phlebophylla and S.reticulata.
2. Both P.palmeni and P.phlebophyllae had a 1-year life cycle and nymphal development took place on the female Salix catkin. The life cycle was generally closely synchronized with the period of catkin development. However, only a few eggs were laid on S.glauca
3. Seasonal perturbation of the host plant by flooding, ice movement and blown sand prevented psyllids breeding in certain areas colonized by the host plant.
4. In P.palmeni densities and 'feeding pressure', measured as biomass of psyllids per gram of catkin, on the different host plants followed the sequence S.pulchra>S.lanata> S.alaxensis > S.glauca. In P.phlebophyllae densities and feeding intensities were similar on S.phlebophylla and S.reticulata and grazing intensity was comparable with P.palmeni on S.pulchra.
5. A highly significant negative correlation was found between psyllid density and catkin dry weight in S.pulchra, S.phlebophylla and S.reticulata , suggesting that psyllid feeding is affecting catkin growth.
6. Predation of psyllid nymphs by syrphid larvae was heavy but there was no evidence of parasitism.
7. The life history strategies of the five psyllid species are discussed within the context of the constraints imposed by the arctic environment.     

Influence of Cotyledon Excision and Sucrose on Root Formation in Pea Cuttings

Sucrose was supplied to stock plants of Pisum sativum L. cv. Alaska grown at different levels of irradiance. There was no significant effect on the rooting of the cuttings by sucrose supply to intact plants regardless of the irradiance. However, an increase in the number of roots per cutting was obtained at increasing concentrations of sucrose when the stock plants had been grown at 4 W m^?2 and their cotyledons had been removed two days before the cuttings were excised. Cotyledons were removed from stock plants at different times before the excision of cuttings with the intent to regulate the endogenous supply of carbohydrate. The number of roots per cutting was reduced by removal of the cotyledons and this reduction was correlated to the number of days the stock plants had grown without cotyledons as well as to the irradiance pre-treatment. A greater reduction occurred in cuttings from plants grown under 4 W m^?2 than from those grown under 38 W m^?2. The growth of the stock plants and the subsequent stem growth of the cuttings was determined by the irradiance to the stock plants and by the time of removal of the cotyledons. Exogenous supply of sucrose had no effect on the stem growth of the cuttings.