The Australian red claw crayfish Cherax quadricarinatus, an emerging species within the freshwater aquaculture trade, is not only an ideal species for commercial production due to its high fecundity, fast growth, and physiological robustness but also notoriously invasive. Investigating the reproductive axis of this species has been of great interest to farmers, geneticists, and conservationists alike for many decades; however, aside from the characterisation of the key masculinising insulin-like androgenic gland hormone (IAG) produced by the male-specific androgenic gland (AG), little remains known about this system and the downstream signalling cascade involved. This investigation used RNA interference to silence IAG in adult intersex C. quadricarinatus (Cq-IAG), known to be functionally male but genotypically female, successfully inducing sexual redifferentiation in all individuals. To investigate the downstream effects of Cq-IAG knockdown, a comprehensive transcriptomic library was constructed, comprised of three tissues within the male reproductive axis. Several factors known to be involved in the IAG signal transduction pathway, including a receptor, binding factor, and additional insulin-like peptide, were found to not be differentially expressed in response to Cq-IAG silencing, suggesting that the phenotypic changes observed may have occurred through post-transcriptional modifications. Many downstream factors displayed differential expression on a transcriptomic level, most notably related to stress, cell repair, apoptosis, and cell proliferation. These results suggest that IAG is required for sperm maturation, with necrosis of arrested tissue occurring in its absence. These results and the construction of a transcriptomic library for this species will inform future research involving reproductive pathways as well as biotechnological developments in this commercially and ecologically significant species.

Following decades of clearing, fragmentation, and degradation of coastal heathlands in southeast Queensland, many endemic species are now threatened with extinction, including the vulnerable sand yabby Cherax robustus (Parastacidae), a freshwater crayfish restricted to 200km 2 of acidic wetlands. Dramatic fluctuations in the biogeography of these wetlands, particularly during the glacial cycles of the Pleistocene, likely shaped the distribution and genetic structure of acid-specialist species, yet their historic and contemporary connectivity remains poorly understood, despite these species being particularly sensitive to habitat fragmentation and environmental change. Here, we investigate the genetic structure of two island and two mainland C. robustus populations within peatlands using DArTseq next-generation DNA sequencing. Analysis of over 7,000 SNP markers indicates population divergence around the Pleistocene-Holocene boundary, with no detectable gene flow between most sites for between 5000 and 13000 years. Geographic proximity did not predict genetic connectivity due to persistent dispersal barriers such as K’gari’s central dune ridge and the Great Sandy Strait. Despite this long-term isolation, we found evidence of genetic erosion in only one population, which should continue to be monitored, however the effect appears natural, predating European arrival in Australia. Populations otherwise appear to have remained genetically healthy where suitable habitat persists, despite thousands of years of isolation. Evidently, sand yabbies are not naturally rare within these stable environments but have become vulnerable through anthropogenic pressures of habitat loss and degradation. The strong population structuring observed means that each population represents a unique genetic lineage, and each lost is irreplaceable. Protecting all remaining habitat and preventing any further degradation is therefore critical to the conservation of this species as well as the wider ecosystem.

Shaped over millennia by fire and shifting biogeographical barriers, the subtropical peatlands of Australia’s eastern coast are among the most carbon-dense terrestrial ecosystems in the world. These are the only known peatlands that are ecologically dependent on fire, resulting from complex ecological interactions between geohydrology, vegetation, microbes and fauna. Following two centuries of fire suppression and ecosystem degradation, protecting peatland biodiversity and carbon storage requires improved knowledge for informed management.

Despite harbouring a disproportionate diversity of rare and endemic species, the pyrophilic peatlands of southeast Queensland remain poorly characterized, particularly regarding their invertebrate communities. In the physically and chemically extreme blackwater pools, meiofaunal assemblages likely form critical trophic links but have never been described due to their small size and low public profile. This study used 18S environmental DNA metabarcoding to characterize invertebrate communities across three peatland sites. We detected 48 unique taxa across 10 phyla, including five invertebrate phyla previously unrecorded in these ecosystems (Cnidaria, Rotifera, Platyhelminthes, Nematoda and Gastrotricha). Metabarcoding exceeded the resolution achieved by field surveys for morphologically cryptic microcrustaceans; however, field surveys achieved better resolution for larger hexapods, demonstrating that the methods target distinct components of the invertebrate community. Key life-history traits were shared across the detected meiofaunal communities, including rapid maturation, parthenogenetic reproduction, and dormancy capabilities. These traits likely enable rapid community recovery and ecosystem stabilization following fire disturbances characteristic of pyrophilic peatlands. Collectively, these taxa occupy a crucial and previously undocumented intermediary trophic link between microbial production and higher consumers. Our findings reveal a previously unrecognized diversity of invertebrate taxa and demonstrate the efficacy of using molecular tools to describe cryptic community assemblages.

Following decades of clearing, fragmentation and degradation of coastal heathlands in southeast Queensland, many endemic species are now threatened with extinction, including the vulnerable sand yabby Cherax robustus (Parastacidae), a freshwater crayfish restricted to 200km ² of acidic wetlands. Dramatic fluctuations in the distribution and extent of these wetlands, particularly during the glacial cycles of the Pleistocene, likely shaped the distribution and genetic structure of acid‐specialist species, yet their historic and contemporary connectivity remains poorly understood, despite these species being particularly sensitive to habitat fragmentation and environmental change. Here, we investigate the genetic structure of two island and two mainland C. robustus populations within peatlands using DArTseq next‐generation DNA sequencing. Analysis of over 7000 SNP markers indicates population divergence occurred during the mid‐to‐late Pleistocene, with no detectable gene flow between most sites for between 50,000 and 120,000 years. Consistent with long‐term isolation, we found slight heterozygote deficiency in all populations, and evidence of genetic erosion in only one population, which should continue to be monitored, though the effect appears to predate European arrival in Australia. Evidently, sand yabbies are not naturally rare within stable environments but have become vulnerable through anthropogenic pressures of habitat loss and degradation. The strong population structuring observed means that each population represents a unique genetic lineage and should be managed as an independent unit. Protecting all remaining habitat and preventing any further degradation is therefore critical to the conservation of this species as well as the wider ecosystem.