Mutual mate choice by mountain pine beetles: size‐dependence but not size‐assortative mating

1. Mutual mate choice may be rare, occurring when both sexes invest heavily in reproduction, mating opportunities are abundant, and individuals differ in quality. 2. Mountain pine beetles, Dendroctonus ponderosae (Curculionidae: Scolytinae) appear to meet the conditions for mutual mate choice. We introduced males to females in breeding sites and observed the occurrence and speed of a male entering a female's gallery. We tested for consequences of mutual mate choice, namely condition‐dependent choosiness and assortative mating. 3. Males were more likely to enter a female's gallery when the gallery was in a smaller tree with less resin production and when the gallery was larger. Female body size and condition did not influence the probability of entry. Larger males were less likely to enter a gallery than were smaller males, probably because of size‐dependent choosiness rather than physical limitations. 4. Small males took longer to enter galleries of large females than of small females, whereas large males entered as quickly into galleries of large females as small females. This suggests size‐dependent choosiness by females. 5. No assortative mating by body size was detected, probably because males appeared to choose on the basis of female‐associated resources rather than on female traits.     

On the development and reproduction of Botryllus schlossen (Tunicata) colonies from the eastern Mediterranean Sea: plasticity of life history traits

Summary

Analysis of developmental patterns of Botryllus schlosseri colonies from the eastern Mediterranean coast has been performed on 143 genets under different temperature regimens (15,20,27 °C) for up to 22 weeks. While the average maximal size as the length of the blastogenic cycle (BC) varied in respect to water temperature, ontogeny at all temperatures was characterized by 4 developmental stages: 1. the lag phase (the first 1–3 BCs, 1 bud/BC), 2. the exponential growth phase (5.5–7.8 BCs, up to 3 buds/BC), 3. the plateau phase, (7.4–8.2 BCs, 1 bud/BC), 4. the degenerative or the variable phase. Many (40.6%) colonies were not sexually reproductive, the others were male only (30.1%) or hermaphrodites. Colonies at the peak of reproduction develop 1.2 oocytes/zooid, and up to 57.7% produced >4 clutches. Analysing onset of reproduction with maximal colony size revealed 4 patterns, two for “male only” colonies and two for hermaphrodites that varied at different sea water temperatures. In two patterns, the onset of reproduction precedes colony maximal size, and in the others it starts at the peak size or thereafter. Zooids at the colony's periphery developed almost twice as many buds as did zooids at the center, but produced significantly lower numbers of eggs. Fragmentation was recorded in large colonies and was temperature dependent. Results are compared with the data available on populations from other localities indicating for dramatically different developmental modes characteristic to this cosmopolitan species.     

Evolution of Cell Adhesion Systems: Evidence for Arg-Gly-Asp-Mediated Adhesion in the Protozoan Neoparamoeba aestuarina

ABSTRACT. Developmental processes in multicellular organisms require structural elements, such as adhesion molecules, to stabilize cells at functional positions. In vertebrates, a series of extracellular matrix proteins, e.g. fibronectin and laminin are involved in cell adhesion. These proteins contain Arg-Gly-Asp [RGD] at their binding sites. Here we show that at concentrations above 2 mM the peptide GRG D SPK, comprising the tripeptide RGD (Arg-Gly-Asp), prevents the adhesiveness of cells of the marine amoeba Neopar-amoeba aestuarina. In addition, elevated levels of GRG D SPK cause cells to alter their shapes from those with digitiform subpseudopodia to rounded cells with small lobed pseudopodia. These cells detach from the substratum. These results are specific for the RGD sequence, because incubation in GRG E SPK solution at the same concentrations had no effect on cell attachment or structure. From these data we suggest that the structural adhesion molecules identified in vertebrates shows amino acid homologies with those found in unicellular protozoa.     

New Specificity of Australia Antigen

THE immunodiffusion laboratory at the Institute for Cancer Research frequently acts as a reference laboratory to test anti-Australia antigen sera for our colleagues in many parts of the world. Because Australia antigen is known to possess different antigenic specificities^1–4, a panel was established which consisted of Australia antigen specimens selected from hepatitis and Down's syndrome patients and from clinically normal residents of the Lau area in Malaita, British Solomon Islands. Sera from normal blood donors without Australia antigen were included as negative controls. All antisera received after August 1971 were tested against this panel to detect heterogeneity among both the antibodies tested and the antigens included in the panel. Immunodiffusion was performed in a seven-hole Ouchterlony pattern with the antiserum in the centre well and a positive Australia antigen control serum from a Pennsylvania Down's syndrome patient in the top and bottom wells. The patterns were cut in a layer of 1.1% agarose in veronal buffer, pH 8.2, on glass lantern slides^6,7.     

Fossil embryos and adult Viviparidae from the Early–Middle Pleistocene of Gesher Benot Ya'aqov, Israel: ecology, longevity and fecundity

Ashkenazi, S., Klass, K., Mienis, H.K., Spiro, B. & Abel, R. 2010: Fossil embryos and adult Viviparidae from the Early–Middle Pleistocene of Gesher Benot Ya'aqov, Israel: ecology, longevity and fecundity. Lethaia, Vol. 43, pp. 116–127.
A unique fossil assemblage of the extinct freshwater viviparids Viviparus apameae galileae and Bellamya sp. with intact embryos enabled the assessment of population ecology parameters applied so far only to recent living populations. The assemblage, from the Early Middle Pleistocene site of Gesher Benot Ya'aqov, occurs in the sedimentary sequence above the Matuyama Brunhes Boundary (MB boundary) at 0.78 Ma. This fossil assemblage is related to a shoreline habitat that was affected by desiccation during a sudden drop in water level. In both species, the youngest females with embryos had five or more whorls, with heights of >24.8 and >16.1 mm in Viviparus and Bellamya respectively. Comparison of shell height and width, aperture height and width and the ratio of shell height/width indicated that females are significantly longer and larger than the shells without embryos. Longevity was estimated as at least 9 years for Viviparus and 8 years for Bellamya and lifetime fecundity of female viviparids was estimated based on longevity and reproductive period. The high number of reproducing females and high number of embryos indicate favourable habitat and climate conditions for both Viviparidae. The fossil Viviparidae from GBY have the characteristics of organisms that are K-selected by natural selection forces. □ Fecundity , fossil embryos , longevity , molluscs , Pleistocene , reproductive output , sexual dimorphism , viviparids.