Annotated zoogeography of non-marine Tardigrada. Part IV: Africa

This paper is the fourth monograph in a series that describes the global records of limno-terrestrial water bears (Tardigrada). Here, we provide a comprehensive list of non-marine tardigrades recorded from Africa, providing an updated and revised taxonomy accompanied by geographic co-ordinates, habitat, and biogeographic comments. It is hoped this work will serve as a reference point and background for further zoogeographical and taxonomical studie

Experimental evolution reveals that sperm competition intensity selects for longer, more costly sperm

It is the differences between sperm and eggs that fundamentally underpin the differences between the sexes within reproduction. For males, it is theorized that widespread sperm competition leads to selection for investment in sperm numbers, achieved by minimizing sperm size within limited resources for spermatogenesis in the testis. Here, we empirically examine how sperm competition shapes sperm size, after more than 77 generations of experimental selection of replicate lines under either high or low sperm competition intensities in the promiscuous flour beetle Tribolium castaneum. After this experimental evolution, populations had diverged significantly in their sperm competitiveness, with sperm in ejaculates from males evolving under high sperm competition intensities gaining 20% greater paternity than sperm in ejaculates from males that had evolved under low sperm competition intensity. Males did not change their relative investment into sperm production following this experimental evolution, showing no difference in testis sizes between high and low intensity regimes. However, the more competitive males from high sperm competition intensity regimes had evolved significantly longer sperm and, across six independently selected lines, there was a significant association between the degree of divergence in sperm length and average sperm competitiveness. To determine whether such sperm elongation is costly, we used dietary restriction experiments, and revealed that protein-restricted males produced significantly shorter sperm. Our findings therefore demonstrate that sperm competition intensity can exert positive directional selection on sperm size, despite this being a costly reproductive trait

Molecular mechanism of topoisomerase poisoning by the peptide antibiotic albicidin

The peptide antibiotic albicidin is a DNA topoisomerase inhibitor with low-nanomolar bactericidal activity towards fluoroquinolone-resistant Gram-negative pathogens. However, its mode of action is poorly understood. We determined a 2.6 Å resolution cryoelectron microscopy structure of a ternary complex between Escherichia coli topoisomerase DNA gyrase, a 217 bp double-stranded DNA fragment and albicidin. Albicidin employs a dual binding mechanism where one end of the molecule obstructs the crucial gyrase dimer interface, while the other intercalates between the fragments of cleaved DNA substrate. Thus, albicidin efficiently locks DNA gyrase, preventing it from religating DNA and completing its catalytic cycle. Two additional structures of this trapped state were determined using synthetic albicidin analogues that demonstrate improved solubility, and activity against a range of gyrase variants and E. coli topoisomerase IV. The extraordinary promiscuity of the DNA-intercalating region of albicidins and their excellent performance against fluoroquinolone-resistant bacteria holds great promise for the development of last-resort antibiotics

Sexual selection protects against extinction

Reproduction through sex carries substantial costs, mainly because only half of sexual adults produce offspring1. It has been theorized that these costs could be countered if sex allows sexual selection to clear the universal fitness constraint of mutation load2,3,4. Under sexual selection, competition between (usually) males and mate choice by (usually) females create important intraspecific filters for reproductive success, so that only a subset of males gains paternity. If reproductive success under sexual selection is dependent on individual condition, which is contingent to mutation load, then sexually selected filtering through ‘genic capture’5 could offset the costs of sex because it provides genetic benefits to populations. Here we test this theory experimentally by comparing whether populations with histories of strong versus weak sexual selection purge mutation load and resist extinction differently. After evolving replicate populations of the flour beetle Tribolium castaneum for 6 to 7 years under conditions that differed solely in the strengths of sexual selection, we revealed mutation load using inbreeding. Lineages from populations that had previously experienced strong sexual selection were resilient to extinction and maintained fitness under inbreeding, with some families continuing to survive after 20 generations of sib × sib mating. By contrast, lineages derived from populations that experienced weak or non-existent sexual selection showed rapid fitness declines under inbreeding, and all were extinct after generation 10. Multiple mutations across the genome with individually small effects can be difficult to clear, yet sum to a significant fitness load; our findings reveal that sexual selection reduces this load, improving population viability in the face of genetic stress.We thank the Natural Environment Research Council and the Leverhulme Trust for financial support, D. Edward for statistical advice and colleagues at the 2013 Biology of Sperm meeting for comments that improved analytical design and interpretation.Peer reviewedPeer Reviewe

Sexual selection and reproductive compatibility in Tribolium castaneum

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Dactylobiotus luci, a new freshwater tardigrade (Eutardigrada: Macrobiotidae) from the Rwenzori Mountains, Uganda

A new freshwater eutardigrade, Dactylobiotus luci sp. nov., is described from a permanent marsh pool (Zaphania’s Pool) at 4225 m elevation in the Alpine zone of the Rwenzori Mountains, Uganda. The new species is most similar to D. dervizi Biserov, 1998 in the shape of the egg processes, absence of papillae and absence of eyes, but differs from it mainly by a different appearance of macroplacoids, by having tips of the egg processes usually sharp, not divided and more slender, and by several  morphometric characters of eggs and adults. The new species was found in fairly acidic (pH<6) Sphagnum-Carex fens bordering/extending into the pool. So far, it has only been recorded in one other high-elevation water body in Rwenzori in a similar habitat.Key words: Tardigrada, Dactylobiotus dervizi, Dactylobiotus luci , alpine pool, Rwenzori, Uganda

The first record of Tardigrada from Zambia, with a description of Doryphoribius niedbalai n.sp. (Eutardigrada: Isohypsibiidae, the evelinae group)

In three mixed samples (mosses and leaf litter) collected in Zambia (southern Africa), forty-three specimens and six eggs of eutardigrades were found. Among them, 29 specimens belonged to a new species of the family Isohypsibiidae, Doryphoribius niedbalai n.sp. The new species belongs to the Doryphoribius evelinae group and it differs from other members of the group mainly by a different number and configuration of dorsal gibbosities, as well as by some morphometric characters. Apart from the new species, the examined material contained also two rare African eutardigrades: Milnesium tetralamellatum and Calcarobiotus  (Calcarobiotus) parvicalcar. These species are recorded for the first time outside their type localities. Additionally,  Paramacrobiotus vanescens is recorded for the fourth time from Africa. In this paper, together with the description of the new species, first ever photomicrographs of  Milnesium tetralamellatum and Paramacrobiotus vanescens are also provided. This is the first account of the phylum Tardigrada from Zambia.Key words: Africa, Doryphoribius niedbalai n.sp., evelinae group, Milnesium  tetralamellatum, Paramacrobiotus vanescens, Tardigrada, Zambia

Dactylobiotus luci, a new freshwater tardigrade (Eutardigrada, Macrobiotidae) from the Rwenzori Mountains (Uganda/DR Congo).

A new freshwater eutardigrade, Dactylobiotus luci sp. nov., is described from a permanent marsh pool (Zaphania's Pool) at 4225 m elevation in the Alpine zone of the Rwenzori Mountains, Uganda. The new species is most similar to D. dervizi Biserov, 1998 in the shape of the egg processes, absence of papillae and absence of eyes, but differs from it mainly by a different appearance of macroplacoids, by having tips of the egg processes usually sharp, not divided and more slender, and by several morphometric characters of eggs and adults. The new species was found in fairly acidic (pH < 6) Sphagnum-Carex fens bordering/extending into the pool. So far, it has only been recorded in one other high-elevation water body in Rwenzori in a similar habitat

Short communications: The first record of the genus Haplohexapodibius Pilato & Beasley, 1987 in Africa, with notes on synonymy of Hexapodibius beasleyi Maucci, 1988, with Haplohexapodibius seductor Pilato & Beasley, 1987

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