Prefrontal deep projection neurons enable cognitive flexibility via persistent feedback monitoring

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Promiscous female Euxesta eluta derive nutrients for ovarian development by expelling and consuming ejaculates

Seminal gifts range from important material donations to items that provide little direct benefit to females. Promiscuous, female silk corn flies Euxesta eluta expel and consume male ejaculates immediately after mating. The evolution and function of this peculiar behavior are currently unknown. We performed a series of experiments aimed to: determine if females under different dietary regimes derive nutrients or water for survival and/or reproduction from ejaculate consumption, if males suffer a fitness cost from supplying females with ejaculates, and if females prefer to mate and/or are more likely to store sperm from well fed than nutritionally stressed presumably inferior males. Experiments revealed that protein deprived E. eluta females derive nutrients for ovarian development through consumption of ejaculates of protein fed males. No seminal products affecting survival appear to be transferred in the consumed ejaculate. However, ovarian development, in contrast to testes growth, occurs in detriment of longevity. Females preferred to mate with protein fed males, yet sperm retention in spermathecae was extremely rare after a single mating. This finding suggests that females could be exerting post copulatory control. A key question that remained to be addressed for the understanding of this puzzling and promiscuous mating system is what ecological factors or male traits drive females to retain sperm from one or several males in order to achieve and/or maximize fertilization potential.     

Identifying biochemical phenotypic differences between cryptic species

Molecular genetic methods can distinguish divergent evolutionary lineages in what previously appeared to be single species, but it is not always clear what functional differences exist between such cryptic species. We used a metabolomic approach to profile biochemical phenotype (metabotype) differences between two putative cryptic species of the earthworm Lumbricus rubellus. There were no straightforward metabolite biomarkers of lineage, i.e. no metabolites that were always at higher concentration in one lineage. Multivariate methods, however, identified a small number of metabolites that together helped distinguish the lineages, including uncommon metabolites such as Nε-trimethyllysine, which is not usually found at high concentrations. This approach could be useful for characterizing functional trait differences, especially as it is applicable to essentially any species group, irrespective of its genome sequencing status.     

Ultrastructure of spermatozoa in Orthalicidae (Mollusca,Gastropoda, Stylommatophora) and its systematic implications

Sperm morphology of orthalicid gastropods Clessinia pagoda, Spixia tucumanensis, Plagiodontes daedaleus (Odontostominae) and Drymaeus hygrohylaeus, D. poecilus, Bostryx stelzneri (Bulimulinae) are examined and described for the first time using transmission electron microscopy. Spermatozoa show the general characteristic of Pulmonata: an acrosomal vesicle, sperm nucleus helical, mitochondrial derivative forming a continuous sheath with paracrystalline material and coarse fibers associated with axonemal doublets. Features in the acrosomal complex and shape of the nucleus distinguish orthalicid sperms from other stylommatophoran. The acrosomal pedestal is traversed by fine striations in all species examined except in S. tucumanensis. The structure and thickness of the perinuclear sheath with a single or double layer of electron-dense material ensheathing the nuclear apex is characteristic of the group. The presence of a subnuclear ring in Drymaeus, Bostryx and Clessinia species is also reported. A data matrix of eleven species per 34 characters (16 sperm plus 18 anatomical and shell characters) from orthalicids plus other stylommatophoran and systellommatophoran representative species was constructed. Three cladistic analyses (sperm-based, anatomical-based and a combined sperm + anatomical-based) were performed to test the phylogenetic potential of sperm ultrastructure in orthalicid systematics and understand how sperm characters affect the topology and resolution of the obtained trees. Stylommatophora resulted in a monophyletic clade in the sperm-based and in the combined-character analysis. Orthalicidae is monophyletic only in the combined-character cladogram. Within Orthalicidae, Odontostominae is recovered as a monophyletic clade in all analyses, while Bulimulinae is paraphyletic in all trees except in the combined phylogeny. The present study and cladistic analyses performed support the hypothesis that characters on sperm ultrastructure are informative for stylommatophoran systematic and phylogenetic approaches, providing synapomorphies at familiar, subfamiliar and generic level.     

Separate Intramolecular Targets for Protein Kinase A Control N-Methyl-d-aspartate Receptor Gating and Ca2+ Permeability

Protein kinase A (PKA) enhances synaptic plasticity in the central nervous system by increasing NMDA receptor current amplitude and Ca²⁺ flux in an isoform-dependent yet poorly understood manner. PKA phosphorylates multiple residues on GluN1, GluN2A, and GluN2B subunits in vivo, but the functional significance of this multiplicity is unknown. We examined gating and permeation properties of recombinant NMDA receptor isoforms and of receptors with altered C-terminal domain (CTDs) prior to and after pharmacological inhibition of PKA. We found that PKA inhibition decreased GluN1/GluN2B but not GluN1/GluN2A gating; this effect was due to slower rates for receptor activation and resensitization and was mediated exclusively by the GluN2B CTD. In contrast, PKA inhibition reduced NMDA receptor-relative Ca²⁺ permeability (P_Ca/P_Na) regardless of the GluN2 isoform and required the GluN1 CTD; this effect was due primarily to decreased unitary Ca²⁺ conductance, because neither Na⁺ conductance nor Ca²⁺-dependent block was altered substantially. Finally, we show that both the gating and permeation effects can be reproduced by changing the phosphorylation state of a single residue: GluN2B Ser-1166 and GluN1 Ser-897, respectively. We conclude that PKA effects on NMDA receptor gating and Ca²⁺ permeability rely on distinct phosphorylation sites located on the CTD of GluN2B and GluN1 subunits. This separate control of NMDA receptor properties by PKA may account for the specific effects of PKA on plasticity during synaptic development and may lead to drugs targeted to alter NMDA receptor gating or Ca²⁺ permeability.