Reconciling diagnostic traits in living and fossil taxa: The taxonomy and evolution of the genus Microceratina (Crustacea, Ostracoda, Cytheruridae).

The original diagnosis of the genus Microceratina Swanson is re-examined with the aim of elucidating the evolutionary history of this living and fossil genus. The different systematic placements of this genus in one of three alternative suprageneric taxa, family Bythocytheridae Sars, family Cytheruridae G.W. Müller (subfamily Eucytherurinae Puri, emend. Maddocks & Steineck) and/or family Loxoconchidae Sars are reviewed. We provide details of a special type of tiny pores, named Loophole Sieve-type Pore Canals, and show how their morphology and position on the valve differ from the typical Sieve-type Pore Canals present in other superfamily Cytheroidea groups, especially members of the Loxoconchidae. A comparative analysis of the valve ornamentation, especially the structure of the anterior peripheral area, and posterior margin morphology, between selected taxa of the three subfamilies of the Cytheruridae (Cytherurinae, Cytheropterinae, Eucytherurinae) demonstrates that Microceratina species belong to a special phylogenetic lineage of Eucytherurinae, which differs from another lineage represented by the genus Xylocythere Maddocks & Steineck. This proposal is strengthened by examination of the limb traits of Microceratina martensi Namiotko et al., currently the only living species of the genus for which both valves and limbs are described; the description is extended herein. Key diagnostic traits of the genus Microceratina are presented, a new Early Jurassic age species is described, and two new combinations are proposed. The homeomorphic valve shapes of M. andreui sp. nov., M. amfibola and ?S. rectum (Loxoconchidae) support the value of the approach adopted herein: analysis of subtle morphological details with high-resolution microscopy.

Non-marine Ostracoda (Crustacea) of the Early Cretaceous Pre-Salt sediments of Brazil: An illustrated catalogue of the type specimens of Wicher, Krmmelbein, Krmmelbein amp; Weber, and Bate.

Type material of 10 genera, one subgenus, 110 species and 28 subspecies described by Wicher (1959), Krmmelbein (1961, 1962, 1963, 1964a,b, 1965a,b), Krmmelbein Weber (1971) and Bate (1972, 1994) are re-illustrated using optical digital technology in order to provide a standard reference for future systematic work and its biostratigraphical and palaeoenvironmental application. The genera are: Brasacypris, Coriacina, Hourcqia, Ilhasina, Looneyellopsis, Pattersoncypris, Petrobrasia, Reconcavona, Salvadoriella, and Tucanocypris, and subgenus Cypridea (Sebastianites).

Learnings from over a decade of increasing pesticide resistance in the redlegged earth mite, Halotydeus destructor (Tucker).

BACKGROUND: The redlegged earth mite, Halotydeus destructor (Tucker), is a destructive and economically important pest of winter grain crops and pastures in Australia. It is largely controlled by pesticides, but this mite has evolved resistance to pyrethroid and organophosphate chemicals. A national Resistance Management Strategy has been developed for pro-active management to delay further resistance evolution, though its success is reliant on a detailed understanding of the incidence, patterns of spread, current distribution and the nature of resistance in the field. Here, we report on a long-term resistance surveillance programme undertaken between 2006 and 2019 informed by resistance risk forecasting. RESULTS: By mapping the Australian distribution of resistance through time, we show that resistance is present across three Australian states and covers more than 3000 km. This current range includes a recently identified population exhibiting organophosphate resistance representing the most easterly location of resistance in H. destructor. Using field history information, we identify associations for the first time between crop management practices employed by farmers and the presence of pyrethroid resistance. Management strategies that could minimize the risk of further resistance include limiting local spread of resistance through farm hygiene practices, crop rotations and reducing pesticide usage. CONCLUSION: This study highlights the challenges of resistance in H. destructor but also indicates how quantitative resistance risk analysis can be developed to target field surveillance and delay further resistance. The management strategies highlighted in this study can help maintain the effectiveness of control options but will depend on farmer engagement and adoption. © 2021 Society of Chemical Industry.

Origin of resistance to pyrethroids in the redlegged earth mite (Halotydeus destructor) in Australia: repeated local evolution and migration.

BACKGROUND: Halotydeus destructor is a major pest of crops and pastures across southern parts of Australia. This invasive mite has been chemically controlled for over 50 years, but resistance to synthetic pyrethroids and organophosphates is developing. Understanding processes behind the emerging resistance is important for effective management efforts. We undertook a ddRAD pool-sequencing approach to analyse genome-wide single nucleotide polymorphism variation in H. destructor population samples at two scales: local resistance across a set of fields, and regional resistance across their Australian range, along with toxicology bioassays to screen for pyrethroid resistance. RESULTS: Spatial patterns of genomic variation and resistance at a local scale indicated that genetic similarity among samples was more closely correlated with distance along roads and fence-lines than with straight-line geographic distance. This pattern was particularly strong in resistant samples, which were also more related than susceptible samples, suggesting local spread of resistance within an area after it emerged. By contrast, regional data suggest resistance has emerged repeatedly within parts of Australia. Our de novo annotation of the H. destructor draft genome sequence and Bayesian analysis identified several candidate loci strongly associated with population-level resistance to pyrethroids, located in genomic regions that code for transmembrane transport and signalling proteins that have previously been linked to insecticide resistance in other arthropods. CONCLUSION: Our findings highlight multiple independent evolutionary events leading to resistance in H. destructor, and demonstrate the utility and cost-effectiveness of a cross-population, genome-wide association study to reveal processes underlying adaptive evolution in a non-model invasive species. © 2019 Society of Chemical Industry.

Sieve-type pore canals in the Timiriaseviinae-A contribution to the comparative morphology and the systematics of the Limnocytheridae (Ostracoda, Crustacea).

Examination of normal pore canals, especially sieve-type pore canals, in living and fossil representatives of ten genera of the family Limnocytheridae, subfamily Timiriaseviinae, has revealed important diversity of structure. These complex pore canals have been studied via high-resolution scanning electron microscopy (the Cartographic Method) and analysed via the application of newly devised indices to assess patterns of consistency and variation in both detailed structure of individual pores and of their distribution on the calcified valve. The timiriaseviine taxa are compared with species of the genera Limnocythere, sub-family Limnocytherinae and Cyprideis (family Cytherideidae). The relationship between the living animal and its aquatic environment is discussed in the light of previous studies and of new evidence herein. The importance of normal pore canals for systematics is highlighted by the recognition and definition of the new tribe Gomphodellini Danielopol, Cabral Lord nov. tribe, subfamily Timiriaseviinae, family Limnocytheridae.

A genomic approach to identify and monitor a novel pyrethroid resistance mutation in the redlegged earth mite, Halotydeus destructor.

Resistance mechanisms are typically uncovered by identifying sequence variation in known candidate genes, however this strategy can be problematic for species with no reference data in known relatives. Here we take a genomic approach to identify resistance to pyrethroids in the redlegged earth mite, Halotydeus destructor, a member of the Penthalidae family of mites that are virtually uncharacterized genetically. Based on shallow genome sequencing followed by a genome assembly, we first identified contigs of the H. destructor parasodium channel gene. By linking variation in this gene to known resistant phenotypes, we located a single nucleotide polymorphism in resistant mites. This polymorphism results in a leucine (L) to phenylalanine (F) amino acid substitution in the II6 region (predicted) of the gene (L1024F). This novel mutation has not previously been linked to pyrethroid resistance, although other polymorphisms have been identified in the two-spotted spider mite, Tetranychus urticae at the same locus (L1024V). The sequencing approach was successful in generating a candidate polymorphism that was then validated using laboratory bioassays and field surveys. A high throughput Illumina-based sequencing diagnostic was developed to rapidly assess resistance allele frequencies in pools of mites sourced from hundreds of populations across Australia. Resistance was confirmed to be widespread in the southern wheatbelt region of Western Australia. Two different resistance mutations were identified in field populations, both resulting in the same amino acid substitution. The frequency and distribution of resistance amplicon haplotypes suggests at least two, and probably more independent origins of resistance.

Discovery and characterisation of field resistance to organophosphorus chemicals in a major mite pest, Halotydeus destructor.

BACKGROUND: The redlegged earth mite (Halotydeus destructor) is an agricultural pest in Australia that attacks a wide variety of crops and pasture species. Chemicals remain an important part of control strategies for H. destructor, despite the existence of resistance to pyrethroid insecticides in this species. Recent chemical control failures involving a second insecticide class, organophosphates, were investigated using pesticide bioassays. RESULTS: We confirmed, for the first time, resistance to organophosphates in H. destructor, and show that resistance is not confined to a single property, or region. There was no evidence that resistance to organophosphorus chemicals has evolved in Australian states outside of Western Australia. CONCLUSION: These findings demonstrate the strong evolutionary capability of H. destructor and highlight the need for ongoing resistance surveillance within Australia. © 2017 Society of Chemical Industry.

First glimpse into Lower Jurassic deep-sea biodiversity: in situ diversification and resilience against extinction.

Owing to the assumed lack of deep-sea macrofossils older than the Late Cretaceous, very little is known about the geological history of deep-sea communities, and most inference-based hypotheses argue for repeated recolonizations of the deep sea from shelf habitats following major palaeoceanographic perturbations. We present a fossil deep-sea assemblage of echinoderms, gastropods, brachiopods and ostracods, from the Early Jurassic of the Glasenbach Gorge, Austria, which includes the oldest known representatives of a number of extant deep-sea groups, and thus implies that in situ diversification, in contrast to immigration from shelf habitats, played a much greater role in shaping modern deep-sea biodiversity than previously thought. A comparison with coeval shelf assemblages reveals that, at least in some of the analysed groups, significantly more extant families/superfamilies have endured in the deep sea since the Early Jurassic than in the shelf seas, which suggests that deep-sea biota are more resilient against extinction than shallow-water ones. In addition, a number of extant deep-sea families/superfamilies found in the Glasenbach assemblage lack post-Jurassic shelf occurrences, implying that if there was a complete extinction of the deep-sea fauna followed by replacement from the shelf, it must have happened before the Late Jurassic.

The current status of pesticide resistance in Australian populations of the redlegged earth mite (Halotydeus destructor).

BACKGROUND: The redlegged earth mite, Halotydeus destructor Tucker, is an important pest of broad-acre farming systems in Australia, New Zealand and South Africa. In 2006, high levels of resistance to synthetic pyrethroids were discovered in this species in Western Australia. RESULTS: Between 2007 and 2010, the authors monitored resistance in field populations and found it had spread considerably within the state of Western Australia. Twenty-six paddocks from 15 individual properties were identified with resistance, and these paddocks ranged over 480 km. To date, resistance has not been detected in any other Australian state. Resistance in H. destructor appears to be found across the entire pyrethroid group, but not to other chemical classes such as organophosphates and carbamates, or other chemistries with novel modes of action. CONCLUSION: The high levels of resistance occurring in Western Australia have caused considerable economic losses due to ineffective chemical applications and mortality of crop plants at seedling establishment. These findings highlight the need for a comprehensive resistance surveillance programme to be developed for H. destructor within Australia. Growers need to consider non-chemical approaches for pest control and should be encouraged to implement pesticide resistance management programmes for H. destructor.