Manganese and zinc in the ovipositors and mandibles of hymenopterous insects

X-ray microanalysis of the ovipositor and mandibles of various hymenopterous insects has revealed the presence in many species of up to 10% wt/wt of either zinc or manganese in the cuticle. These metals appear to be involved in cuticular hardening, so helping to reduce abrasive wear. Zinc is found in the ovipositors of most Siricidae, Stephanoidea, and Chalcidoidea. In Ichneumonoidea and Cynipoidea, the metal involved is manganese. Megalyroidea are unique in the Hymenoptera in having both zinc and manganese in their ovipositors, though in different locations. Except for Bethylidae, no metals were detected in the ovipositors or stings of species that penetrate soft substrates or do not make holes at all. The cutting edge of the mandibles of many insects that chew their way through hard substrates during egress from their pupation sites almost invariably contain high concentrations of zinc, and this is present in many that lack metals in their ovipositor. The phylogenetic and ecological implications of metal occurrence are discussed.     

How sympatric is speciation in the Howea palms of Lord Howe Island?

The two species of the palm genus Howea (Arecaceae) from Lord Howe Island, a minute volcanic island in the Tasman Sea, are now regarded as one of the most compelling examples of sympatric speciation, although this view is still disputed by some authors. Population genetic and ecological data are necessary to provide a more coherent and comprehensive understanding of this emerging model system. Here, we analyse data on abundance, juvenile recruitment, pollination mode and genetic variation and structure in both species. We find that Howea forsteriana is less abundant than Howea belmoreana . The genetic data based on amplified fragment length polymorphisms markers indicate similar levels of variation in the two species, despite the estimated census population size of H. belmoreana being three times larger than that of H. forsteriana . Genetic structure within species is low although some weak isolation by distance is detectable. Gene flow between species appears to be extremely limited and restricted to early-generation hybrids – only three admixed individuals, classified as F2s or first generation backcrosses to a parental species, were found among sampled palms. We conclude that speciation in Howea was indeed sympatric, although under certain strict definitions it may be called parapatric.     

Fossil water striders in Cretaceous French amber (Heteroptera: Gerromorpha: Mesoveliidae and Veliidae)

Fossil gerromorphan bugs from the Cretaceous (Albian–Cenomanian boundary) amber of Charentes, SW France, are reviewed. A larva described by Perrichot et al. (2005) as incertae familiae within the Gerromorpha is now placed in the Mesoveliidae. Three new genera and species are also described and illustrated: Emilianovelia audax Solórzano Kraemer & Perrichot, gen. et sp.n. , and Malenavelia videris Solórzano Kraemer & Perrichot, gen. et sp.n. , which are placed in the Mesoveliidae: Mesoveliinae; and Arcantivelia petraudi Solórzano Kraemer & Perrichot, gen. et sp.n. , which is the first Mesozoic member of the Veliinae. The relationships between these fossils and their palaeoecology are discussed. The new discoveries confirm the antiquity of the semi‐aquatic gerromorphans, particularly the clade (Veliidae + Gerridae). The habitat is described as aquatic and likely marine‐influenced, yet adaptation to a fully marine habitat in these gerromorphans remains difficult to establish. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:F8C034B8-7BD0-4C03-B8FC-CD81D75C7001 .     

Push and bite: trade‐offs between burrowing and biting in a burrowing skink (Acontias percivali)

Trade‐offs are thought to be important in constraining evolutionary divergence, as they may limit phenotypic diversification. Limbless animals that burrow head‐first have been suggested to be evolutionarily constrained in the development of a large head size and sexual head shape dimorphism because of potential trade‐offs associated with burrowing. Here we use an acontiine skink (Acontias percivali) to test for the existence of trade‐offs between traits thought to be important in burrowing (speed and force). As head size dimorphism has been shown to be limited in acontiine lizards, thus suggesting constraints on head size and shape, we additionally explore the potential for trade‐offs between burrowing and biting. Our data show that A. percivali uses a burrowing style different from those previously described for caecilians and amphisbaenians, which relies on the use of extensive lateral and dorsoventral head movements. Our data also show that animals use their entire bodies to generate force, as peak force was determined by total length only. Additionally, both bite force and the time needed to burrow into the substrate were principally determined by relative head width, suggesting a trade‐off between biting and burrow speed. Performance data were indeed suggestive of a correlation between bite force and the time needed to burrow, but additional data are needed to confirm this pattern. In summary, our data suggests that trade‐offs may exist, and may have been of crucial importance in shaping the evolution of head shape in A. percivali, and burrowing lizards more generally. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 91–99.     

Factors affecting the rate of attack by Cotesia rubecula (Hymenoptera: Braconidae)

Abstract. 1. The relationship between responses of the insect parasitoid Cotesia rubecula (Marshall) to kairomones produced by the feeding activities of its host, Pieris rapae (L.), and patterns of parasitism were investigated under field conditions.
2. Parasitoid adults aggregated in patches with the highest densities of host larvae but there was no commensurate increase in the rate of attack in these patches.
3. The rate of attack was not limited by the availability of eggs.
4. The rate of parasitoid attack was highest where feeding damage by the host was highest, irrespective of current host density.
5. The rate of parasitoid attack was further influenced by host age distribution. Late instar larvae were less susceptible to parasitism than were early instar larvae. The rate of attack on early instar larvae occupying the same plants as late instar larvae was reduced. This reduction in rate of attack was due to limitations on parasitoid search time imposed by the increased feeding damage associated with large host larvae and by the increased time the parasitoid required to recover from an attack on these large host larvae.     

International collaboration in freshwater ecology

1. International collaboration in freshwater ecology was examined using authorship affiliations of articles published in thirty-three specialized journals. Most are published in Europe. 2. Researchers from four to thirty-seven different countries were represented in the 100 articles examined for each journal. Only 29% of articles were single-authored; multicountry authors' addresses (indicating international collaboration) were found for 9% (range 0–23% per journal) of articles examined. 3. Five of the eighty-nine countries listed in the addresses of the 3300 articles together contributed >50% of total articles: United States (24.9%), Canada (8.6%), Germany (7.6%), Commonwealth of Independent States (7.0%) and Poland (5.9%). Of the fifteen countries that each produced >2.5% of total articles, the percentage representing international collaboration was highest for France (34.9%) and Canada (24.0%). The seventy-four countries that each contributed <2.5% of total articles generally had higher rates of international collaboration. 4. Researchers in the United States and Canada collaborate internationally almost twice as often in freshwater ecology than in all science. Much of France's extensive international collaboration is with countries that produce few articles in freshwater ecology, and their international collaboration is often exclusively with France. 5. Three journals publishing both marine and freshwater ecology articles contain more articles on the former topic, but more countries are represented in the publication of freshwater than marine research. 6. The percentage of articles that represent international collaboration is higher in freshwater ecology than in medicine, biology, chemistry and engineering, and approximates that in physics.     

Effect and Localization of Trifluralin in Plasmodium falciparum Gametocytes: An Electron Microscopic Study1

Trifluralin, a herbicide which is known to bind to plant and algal tubulin, induced ultrastructural changes in the microtubules of the mature Plasmodium falciparum gametocytes in vitro. Trifluralin treatment led to disassembly of the well ordered subpellicular microtubules, whereas it had no effect on microtubules of human platelets or of rat neuronal cells in vitro. The disassembled microtubules showed fragmented large tubular structures, which frequently were associated with the pellicular membranes. Electron microscopic autoradiography showed radioactive trifluralin associated with the microtubule fragments. These results provide evidence that trifluralin selectively binds to microtubules in malaria parasites and causes disruption of their structure.     

Gene flow and hybridization following introduction of Mus domesticus into an established population

Seventy-seven house mice ( Mus domesticus ) from Eday, Orkney were released into a long-established population on the Isle of May (56^o 12'N) in 1982. Introduced allozymes, mt and Y-chromosome DNA, and Robertsonian chromosomes spread rapidly, reaching approximate stability c . 3 years later at frequencies different to those in both parental populations. The hybrid population was morphometrically intermediate between the two parents. This is a preliminary summary only; full details will be published elsewhere.     

Induced Enzyme Synthesis in the Phytoflagellate, Polytoma

SUMMARY. The enzymatic induction of fatty acid oxidase activity in Polytoma can be characterized as follows: (1) the preferential synthesis of oxidase activity can be induced in non-proliferating cells, (2) the rate of induction is dependent upon the concentration of exogenous nitrogen, (3) the rate of induction is also dependent upon the age of the cells, (4) with log-phase cells, the rate of synthesis is highest and the kinetics of synthesis, linear; the rate of synthesis by older cells is low and variable in form, (5) ultraviolet irradiation selectively inhibits induction at doses which do not inhibit respiratory activity, oxidative assimilation or nitrogen utilization.