Can multiple mating compensate for slower development and shorter adult life in a male dimorphic dwarf spider?

Oedothorax gibbosus (Blackwall, 1841) is a dwarf spider characterized by the occurrence of a male dimorphism: the tuberosus male does not show any remarkable differentiation at the dorsal side of the carapace; the gibbosus morph on the contrary has a hunch behind the eye region, with a transversal groove densely clothed with hairs. These structures play an important function in the gustatorial courtship, being the uptake of secretions by the female from a body part of the male during courtship. Based on standardized survival experiments we show that tuberosus has a greater overall survival strength for different humidity levels than gibbosus . The two male morphs of O. gibbosus also have a different mating strategy: tuberosus as well as gibbosus copulate with virgin females, but gibbosus copulates significantly more with already inseminated females. Because of this strategy gibbosus secures its offspring notwithstanding the faster development, the longer adult life and the greater overall survival strength of tuberosus. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 269–273.     

Regulation of last reproduction steps in tsetse flies (Glossina: Diptera)

Summary

The regulation of ovulation and parturition, in the viviparous tsetse flies, constitutes a very precisely adjusted mechanism, Indeed the process of vitellogenesis takes places, in one oocyte only, during the incubation period when the larva is nourished in utero on milk produced by the mother. Neuropeptides, biogenic amines, neurotransmitters as well as ecdysone, and 20-hydroxyecdysone and also nervous outputs regulate ovulation and parturition. A model is proposed for the mechanisms controlling these processes.     

SOUND ANALYSIS AND SYNTHESIS USING AN AMIGA MICRO-COMPUTER

ABSTRACT

This note presents a program for analysis and synthesis of sounds designed to be used with an Amiga micro-computer. The user is in real-time control of the capture of the signal with reference to both time and amplitude parameters. Subsequently the chosen signal can be edited and analysed. Sonograms can be obtained at three resolutions, both in time and frequency. Measurements of time can be made on the signal, of frequency on the sonogram and of amplitude on sections. Three functions for the extraction of the fundamental are available. A synthetic sound may be obtained, either by modifying the amplitude and frequency modulation of an existing sound, or by creating a new sound by additive synthesis. All the commands can be selected by using a mouse, and the program is user-friendly.     

A relict bank vole lineage highlights the biogeographic history of the Pyrenean region in Europe

The Pyrenean region exhibits high levels of endemism suggesting a major contribution to the phylogeography of European species. But, to date, the role of the Pyrenees and surrounding areas as a glacial refugium for temperate species remains poorly explored. In the current study, we investigated the biogeographic role of the Pyrenean region through the analyses of genetic polymorphism and morphology of a typical forest-dwelling small mammal, the bank vole ( Myodes glareolus ). Analyses of the mitochondrial cytochrome b gene and the third upper molar (M³) show a complex phylogeographic structure in the Pyrenean region with at least three distinct lineages: the Western European, Spanish and Basque lineages. The Basque lineage in the northwestern (NW) Pyrenees was identified as a new clearly differentiated and geographically localized bank vole lineage in Europe. The average M³ shape of Basque bank voles suggests morphological differentiation but also restricted genetic exchanges with other populations. Our genetic and morphological results as well as palaeo-environmental and fossils records support the hypothesis of a new glacial refugium in Europe situated in the NW Pyrenees. The permissive microclimatic conditions that prevailed for a long time in this region may have allowed the survival of temperate species, including humans. Moreover, local differentiation around the Pyrenees is favoured by the opportunity for populations to track the shift of the vegetation belt in altitude rather than in latitude. The finding of the Basque lineage is in agreement with the high level of endemic taxa reported in the NW Pyrenees.     

Patterns of size and shape differentiation during the evolutionary radiation of the European Miocene murine rodents

Fourier analysis applied to the outlines of the first upper and lower molars of European Miocene murine rodents was used to quantify the size and shape variations associated with their radiation and to determine the evolutionary relationships among the taxa. The results suggested the occurrence of two lineages involving different evolutionary patterns. Size exhibits a rapid diversification in both lineages, probably because of selective pressures related to increasing competition among species. With regard to shape, one of the lineages is characterized by a conservative morphology, and the other by a tooth evolution oriented toward broader molars, which is interpreted as an adaptive specialization. Size and shape evolution are diversely associated during the radiation, and they may be related to the morphological differentiation of co-existing species and the avoidance of interspecific competition.     

Abundance and biomass of heterotrophic microorganisms in Lake Tanganyika

1. This study focused on heterotrophic microorganisms in the two main basins (north and south) of Lake Tanganyika during dry and wet seasons in 2002. Bacteria (81% cocci) were abundant (2.28–5.30 × 10⁶ cells mL^?1). During the dry season, in the south basin, bacterial biomass reached a maximum of 2.27 g C m^?2 and phytoplankton biomass was 3.75 g C m^?2 (integrated over a water column of 100 m). 2. Protozoan abundance was constituted of 99% of heterotrophic nanoflagellates (HNF). Communities of flagellates and bacteria consisted of very small but numerous cells. Flagellates were often the main planktonic compartment, with a biomass of 3.42–4.43 g C m^?2. Flagellate biomass was in the same range and often higher than the total autotrophic biomass (1.60–4.72 g C m^?2). 3. Total autotrophic carbon was partly sustained by the endosymbiotic zoochlorellae Strombidium. These ciliates were present only in the euphotic zone and usually contributed most of the biomass of ciliates. 4. Total heterotrophic ciliate biomass ranged between 0.35 and 0.44 g C m^?2. In 2002, heterotrophic microorganisms consisting of bacteria, flagellates and ciliates represented a large fraction of plankton. These results support the hypothesis that the microbial food web contributes to the high productivity of Lake Tanganyika. 5. As the sole source of carbon in the pelagic zone of this large lake is phytoplankton production, planktonic heterotrophs ultimately depend on autochthonous organic carbon, most probably dissolved organic carbon (DOC) from algal excretion.     

A REDRAWN PHYLOGENY OF GUENONS BASED UPON THEIR CALLS—BIOGEOGRAPHICAL IMPLICATIONS

ABSTRACT

A phylogeny of guenons was drawn up from the analysis of the acoustic structure of their cohesion, contact and alarm calls, as well as of the loud calls of the adult males. The plesiomorphic or apomorphic state of every acoustic parameter retained was inferred from comparisons with calls given by papionines and/or colobines. A cladistic method was used for analysing a matrix of species by character.

The proposed phylogeny separates guenons into two groups: the one includes all forest- living arboreal forms, the other most of the terrestrially-adapted species. The latter, together with C. nigroviridis, which lie close to the origin from which all guenons diverged, share a relatively primitive position, while the arboreal species are the most derived living representatives of the taxon. Quite reliable interspecific affinities are found among arboreal forms, while there are some inconsistencies for the more primitive species. Such results suggest that cercopithecines would have undergone a radiation from more or less open habitats into forests, the evolution proceeding from large-bodied, partly-terrestrial forms to smaller arboreal ones.     

INHIBITION OF CELLULAR GROWTH AND STEROID 11β-HYDROXYLATION INRAS-TRANSFORMED ADRENOCORTICAL CELLS BY THE FUNGAL TOXINS BETICOLINS

The proliferation of GM16 and 4CDTras-transformed newborn rat adrenocortical (RTAC) cells and Y1 mouse adrenal tumor cells was inhibited by beticolins, the fungal toxins extracted fromCercospora beticola, at submicromolar concentrations in a dose-dependent manner. Inhibitory concentrations for half the maximum inhibition were 150, 75 and 25 nm for beticolin-1 and 230, 150 and 50 nm for beticolin-2 in GM16, 4CDT and Y1 cells respectively. Beticolins strongly inhibited the production of 11β-hydroxysteroids on the second and third days of treatment in a dose-dependent manner between 0.1 and 1 μm . Beticolins were shown by confocal microscopy to be localized in cytoplasmic organelles about 30–40 min after treatment. This finding favors a direct action of beticolins on mitochondrial steroid 11β-hydroxylase albeit another less direct mechanism involving a cytoplasmic signaling pathway cannot be excluded.     

ECOLOGY OF THE INTRODUCED SNAIL MELANOIDES TUBERCULATA (GASTROPODA: THIARIDAE) IN RELATION TO BIOMPHALARIA GLABRATA IN THE MARSHY FOREST ZONE OF GUADELOUPE, FRENCH WEST INDIES

Melanoides tuberculata was introduced to several types of aquatichabitat occurring in the marshy forest zone, Guadeloupe, asa competitor of the snail host, Biomphalaria glabrata, of Schistosomamansoni. Colonization by the competitor was successful in allhabitats, but the impact on the snail host was variable accordingto the site. Evolution of global prevalences, intensities andabundances of Schistosoma mansoni in the reservoir host, Rattusrattus, did not show any significant changes during the eightyears following the introduction of the competitor. The analysisof size distribution of M. tuberculata in a release plot showedthat maximum reproduction took place during the rainy seasonbetween June and November. The thiarid snail needed 4.5 monthsto reach a size of 10 mm, 14 months to reach 15 mm, and morethan 30 months to reach 20 mm. Calculated life expectancieswere 0.74 year at the first year of age, 0.9 year at the secondyear, and 0.5 year at the third year. (Received 21 September 1992; accepted 5 January 1993)