Biology subjects

Walker, M. M.

Publications and source records attributed to Walker, M. M..

3 recordsLinked to original sources

bioRxiv2026

Underwater caves preserve biochemical composition and histological structure in modern and fossil mammalian bones

Biochemical and microstructural bone degradation (diagenesis) occurs after death and is environment dependent. Existing macroscopic and histological research suggests bones submerged in water degrade differently to those in dry contexts. However, little is known about how submerged and dry degradation processes affect skeletal remains in caves, which have fundamentally different decomposition conditions to open environments. This study combines histology with laboratory-based and synchrotron-sourced Fourier-transform infrared microspectroscopy (FTIRM) to characterise bone microanatomical and biochemical degradation in bones from underwater (wet) and dry cave environments. We investigate fossil and historic mammal (ovicaprids, macropodids) bone diagenesis from Mount Gambier, South Australia, intra-skeletally and between depositional conditions. FTIRM analysis revealed greater collagen-associated amide signatures in historic wet bones than dry counterparts, while fossils showed no detectable signal. Despite biochemical differences, bone histology did not present noticeable differences between specimens, with similar birefringence levels and no radial micro-fractures across the secondary osteon border. Wet and fossil bones also exhibited comparable carbonate content despite differences in organic composition and mineral recrystallisation, suggesting submerged cave environments facilitate preservation of carbonate-bearing mineral phases within relatively closed (trapped) diagenetic systems. These findings demonstrate that underwater cave conditions support fossil preservation through complex and heterogenous organic and mineral diagenetic pathways.

paleontology↗

bioRxiv2026

Neotaphonomic characteristics of vertebrate site formation in underwater caves

Recovering well-preserved vertebrate remains from underwater caves has provided critical insights into archaeological and palaeontological records worldwide. However, understanding how bone assemblages form and are modified in underwater environments remains limited due to stable low energy burial conditions that produce time-averaged deposits, and underwater settings that hinder traditional recording and recovery methods. This study applies an actualistic taphonomic framework to three assemblages of domesticate animal bones (N = 231) from two underwater caves, Green Waterhole and Gouldens Sinkhole, near Mount Gambier, South Australia, encompassing known submerged (wet; N = 134) and dry (N = 97) burial conditions. The assemblages were examined to assess how wet and dry cave environments impact bone distribution, surface and microstructural modification. Radiocarbon dating of 41 specimens indicates that domesticate fauna were deposited over decadal and centennial timescales, allowing taphonomic signatures to be contextualised through time. Statistically significant differences were identified between wet and dry burial contexts. Bones recovered from wet contexts exhibit mostly better preservation, including skeletal elemental completeness, surface, and microstructure, than those from dry caves. However, some of the submerged specimens also have elevated frequencies of bone surface corrosion with macroscopic evidence for heterogenous black biological staining, algal or biofilm attack, and a distinctive form of circular etching. Histotaphonomy further reveals patterns of peripheral cyanobacterial tunnelling across most bones recovered from submerged contexts. Bones from dry environments were dominated by terrestrially linked tunnelling across all regions of the bone cortex. These findings can be explained by variation in light availability across different cave zones which influences biological activity and, in turn, the expression of taphonomic markers on bone externally and at the microstructural level. This is the first study to provide a benchmark bone dataset for reconstructing depositional histories and post-depositional reworking in underwater cave environments under a taphonomic framework.

paleontology↗

bioRxiv2025

Mosquito sex under lock and key

Mosquitoes, the worlds deadliest animal, exemplify single-mating systems where females mate only once in their lifetime, making mate choice critically important for reproductive success and mosquito control. Despite this importance, the mechanisms of female mating control and what prevents additional matings remain poorly understood. To address this gap, we developed a dual-color fluorescent sperm system in invasive Aedes aegypti mosquitoes and quantified mating patterns, confirming that 86-96% of females mate only once. Using behavioral tracking of mating pairs, deep learning, and quantitative analysis at increasing resolution, we discovered that females actively control mating initiation through a previously undescribed behavior: genital tip elongation. This female response is triggered by rapidly evolving male genital structures, creating a precise lock-and-key mechanism that determines mating success. Comparative analysis revealed that Aedes albopictus, separated from Aedes aegypti by 35 million years of evolution, employs a similar female-controlled system. However, Aedes albopictus males uniquely bypass female control when attempting cross-species matings with Aedes aegypti females but not with conspecific females. This "lock-picking" ability, combined with the known sterility of cross-species matings, may explain how Aedes albopictus competitively displaces Aedes aegypti populations in overlapping territories. Our findings redefine mosquito reproduction as a female-controlled process and establish a quantitative framework for investigating the molecular and neurobiological mechanisms underlying mating control and species competition in these globally important disease vectors.

animal behavior and cognition↗