Diet, breeding and growth in a new carnivorous marsupial, the Buff-footed Antechinus, Antechinus mysticus, at the northern and southern limits of its range

This thesis examined the diet and ecology of a new species of suicidal mammal. The mammal’s diet included a wide range of insects and spiders, supplemented by vertebrates such as small lizards. Breeding strategy was the same as for other members of the genus: all males die annually, apparently due to immune system malfunction after a brief period of frenetic mating

The Drosophila melanogaster Phospholipid Flippase dATP8B Is Required for Odorant Receptor Function

The olfactory systems of insects are fundamental to all aspects of their behaviour, and insect olfactory receptor neurons (ORNs) exhibit exquisite specificity and sensitivity to a wide range of environmental cues. In Drosophila melanogaster, ORN responses are determined by three different receptor families, the odorant (Or), ionotropic-like (IR) and gustatory (Gr) receptors. However, the precise mechanisms of signalling by these different receptor families are not fully understood. Here we report the unexpected finding that the type 4 P-type ATPase phospholipid transporter dATP8B, the homologue of a protein associated with intrahepatic cholestasis and hearing loss in humans, is crucial for Drosophila olfactory responses. Mutations in dATP8B severely attenuate sensitivity of odorant detection specifically in Or-expressing ORNs, but do not affect responses mediated by IR or Gr receptors. Accordingly, we find dATP8B to be expressed in ORNs and localised to the dendritic membrane of the olfactory neurons where signal transduction occurs. Localisation of Or proteins to the dendrites is unaffected in dATP8B mutants, as is dendrite morphology, suggesting instead that dATP8B is critical for Or signalling. As dATP8B is a member of the phospholipid flippase family of ATPases, which function to determine asymmetry in phospholipid composition between the outer and inner leaflets of plasma membranes, our findings suggest a requirement for phospholipid asymmetry in the signalling of a specific family of chemoreceptor proteins

The Drosophila melanogaster phospholipid flippase dATP8B is required for odorant receptor function.

The olfactory systems of insects are fundamental to all aspects of their behaviour, and insect olfactory receptor neurons (ORNs) exhibit exquisite specificity and sensitivity to a wide range of environmental cues. In Drosophila melanogaster, ORN responses are determined by three different receptor families, the odorant (Or), ionotropic-like (IR) and gustatory (Gr) receptors. However, the precise mechanisms of signalling by these different receptor families are not fully understood. Here we report the unexpected finding that the type 4 P-type ATPase phospholipid transporter dATP8B, the homologue of a protein associated with intrahepatic cholestasis and hearing loss in humans, is crucial for Drosophila olfactory responses. Mutations in dATP8B severely attenuate sensitivity of odorant detection specifically in Or-expressing ORNs, but do not affect responses mediated by IR or Gr receptors. Accordingly, we find dATP8B to be expressed in ORNs and localised to the dendritic membrane of the olfactory neurons where signal transduction occurs. Localisation of Or proteins to the dendrites is unaffected in dATP8B mutants, as is dendrite morphology, suggesting instead that dATP8B is critical for Or signalling. As dATP8B is a member of the phospholipid flippase family of ATPases, which function to determine asymmetry in phospholipid composition between the outer and inner leaflets of plasma membranes, our findings suggest a requirement for phospholipid asymmetry in the signalling of a specific family of chemoreceptor proteins

A chromosome-level genome of Antechinus flavipes provides a reference for an Australian marsupial genus with male death after mating

The 15 species of small carnivorous marsupials that comprise the genus Antechinus exhibit semelparity, a rare life-history strategy in mammals where synchronized death occurs after one breeding season. Antechinus males, but not females, age rapidly (demonstrate organismal senescence) during the breeding season and show promise as new animal models of ageing. Some antechinus species are also threatened or endangered. Here, we report a chromosome-level genome of a male yellow-footed antechinus Antechinus flavipes. The genome assembly has a total length of 3.2 Gb with a contig N50 of 51.8 Mb and a scaffold N50 of 636.7 Mb. We anchored and oriented 99.7% of the assembly on seven pseudochromosomes and found that repetitive DNA sequences occupy 51.8% of the genome. Draft genome assemblies of three related species in the subfamily Phascogalinae, two additional antechinus species (Antechinus argentus and A. arktos) and the iteroparous sister species Murexia melanurus, were also generated. Preliminary demographic analysis supports the hypothesis that climate change during the Pleistocene isolated species in Phascogalinae and shaped their population size. A transcriptomic profile across the A. flavipes breeding season allowed us to identify genes associated with aspects of the male die-off. The chromosome-level A. flavipes genome provides a steppingstone to understanding an enigmatic life-history strategy and a resource to assist the conservation of antechinuses

Orco and Or22a localize normally to the dendrites in <i>dATP8B</i> mutants.

<p>14 µm thick antennal sections from wild type flies (CS-5) were stained for anti-Orco or for anti-Or22a. No difference in either Orco or Or22a localisation to the outer dendrites was observed in <i>dATP8B</i> mutants (<i>dATP8B^f05203</i>) compared to control flies.</p

Orco and Or22a localize normally to the dendrites in <i>dATP8B</i> mutants.

<p>14 µm thick antennal sections from wild type flies (CS-5) were stained for anti-Orco or for anti-Or22a. No difference in either Orco or Or22a localisation to the outer dendrites was observed in <i>dATP8B</i> mutants (<i>dATP8B^f05203</i>) compared to control flies.</p

<i>dATP8B</i> is expressed and required in <i>Or-</i>expressing olfactory receptor neurons.

<p>(A–A′) dATP8B protein localises to the dendrites of ORNs. 14 µm thick antennal sections from wild type flies (CS-5) were stained for anti-dATP8B (magenta). Strong anti-dATP8B staining is seen in the shafts of the sensilla (the location of the outer dendrites) of basiconic (arrows) and trichoid (arrowhead) sensilla. Staining is also seen in the inner dendrites and cell bodies, however this staining is also present in <i>dATP8B</i> mutants. (B) The strong outer dendrite staining of anti-dATP8B is absent in <i>dATP8B</i> mutants (<i>ll2</i>/<i>Df(3R)Exel8155</i>), indicating it is specific for dATP8B. (C) dATP8B and Orco co-localise in the outer dendrites. 14 µm thick antennal sections from wild type flies were stained for anti-dATP8B (magenta) and Orco (green). (D) dATP8B is absent from the outer dendrites of <i>Gr21a</i>-expressing (ab1C) neurons. 14 µm thick antennal sections from Gr21a&gt;mCD8:GFP flies were stained for anti-dATP8B (magenta) and anti-GFP (green). (E) In <i>Orco-GAL4: UAS-dATP8B^RNAi</i> flies (red bars) the EAG response is significantly reduced compared to controls (black and grey bars, t-test, Bonferroni, <i>p&lt;0.05</i>) for some of the same odorants that are affected by the two <i>dATP8B</i> mutant alleles. Bars represent mean EAG responses ± SEM (n = 6–10). Odorants are: EA, ethyl acetate, PA, pentyl acetate, MS, methyl salicylate, OL, 1-octen-3-ol, HB, ethyl 3-hydroxybutanoate, EH, ethyl hexanoate, BZ, benzaldehyde, PO, paraffin oil (solvent blank).</p

<i>dATP8B</i> is required for responses of <i>Or</i> but not <i>IR</i> or <i>Gr-</i> expressing sensory neurons.

<p>(A–C) Mutations in <i>dATP8B</i> reduce the sensitivity of <i>Or</i>-expressing neurons to their major ligands. Dose-response curves for neurons located in three different morphological types of sensilla are shown; (A) ab3B neurons in basiconic sensilla (<i>Or85b</i>) to 2-heptanone, (B) at1A neurons in trichoid sensilla (<i>Or67d</i>) to cis-vaccenyl acetate, (C) ac3B neurons in coeloconic sensilla (<i>Or35a</i>) to Z3-hexenol. In all cases sensitivity is significantly lowered for all doses in homozygous <i>dATP8B^f05203</i> flies (red) compared to controls (black, t-test, Bonferroni, n = 6–9, recorded from 4–8 flies). (D–E) Mutations in <i>dATP8B</i> differentially alter responses of ab3A neurons (<i>Or22a</i>) to a major ligand ethyl hexanoate (D) and a minor ligand ethyl butanoate (E). (n = 7 sensilla, recorded from 5–6 flies). (F–I) Neurons expressing <i>IR</i> or <i>Gr</i> receptors are not affected by <i>dATP8B</i> mutations. Four different types of neurons are shown; (F) responses of ac2A neurons in coeloconic sensilla (<i>IR41a</i> and <i>IR76b</i>) to 1,4-diaminobutane, (G) responses of ac3A neurons in coeloconic sensilla (<i>IR75a,b and c</i>) to propionic acid, (H) responses of ab1C neurons in basiconic sensilla (<i>Grs21a</i> and <i>63a</i>) to CO₂, (I) responses from single neurons in labellar taste sensilla expressing <i>Gr</i> genes to 100 mM sucrose (Suc) or 10 mM caffeine (Caff) (mean ± SEM). In all cases control and mutant responses are not significantly different (n = 6–10 sensilla from 3–5 flies, t-tests, Bonferroni). Controls are either wild type or heterozygous <i>dATP8B^f05203</i> mutants.</p

Dietary composition and prey preference of a new carnivorous marsupial species, the buff-footed antechinus (Antechinus mysticus), at the northern and southern limits of its range

The buff-footed antechinus (Antechinus mysticus) is a newly described carnivorous marsupial from eastern Australia. We examined the diet composition and prey preference of this little known dasyurid in the southernmost (Brisbane) and northernmost (Eungella) populations. Animals were captured over three months (July–September) during 2014 encompassing the breeding period (late July and August) of the species. Seasonal sampling carried over into a second year which followed the succeeding cohort of juveniles as they dispersed from their maternal nest (summer), through their maturation (autumn), to the beginning of breeding (winter), sampling across one complete generation. The diet of A. mysticus consisted predominantly of invertebrates, with 16 prey orders identified (11 Insecta, two Arachnida, two Myriapoda, one Crustacea). Vertebrate (Family Scincidae) consumption was recorded in low abundance at both sites. The diet of A. mysticus was dominated by Araneae (spiders), Blattodea (cockroaches) and Coleoptera (beetles). Comparison of identified prey consumption in scats with prey availability in pitfall traps showed A. mysticus to be a dietary generalist, opportunistically consuming mostly invertebrate prey with supplementary predation on small vertebrates. Juvenile A. mysticus preyed predominantly on Blattodea (33.4% mean percentage volume) and Coleoptera (31.6% mean percentage volume), potentially suggesting a preference for larger, easier to catch, prey items. Further exploration into the relationship between prey and body size is required to determine this