Biology subjects

Watson-Zink, V. M.

Publications and source records attributed to Watson-Zink, V. M..

4 recordsLinked to original sources

bioRxiv2026

Aquatic respiratory rates in red devil vampire crabs (Geosesarma hagen) are dependent on interactions between temperature, sex, and body size

The shift to terrestrial environments in ancestrally aquatic animals is often associated with key physiological and physical changes, including shifts in respiratory physiology and in some cases, even the evolution of completely novel respiratory structures. Examining how respiration operates across a gradient of submersion states in ancestrally aquatic terrestrial animals may shed light on how complex biological traits shift under different selective regimes. In this work, we begin exploring respiration in terrestrially-adapted land crabs that still use their gills to respire while underwater. We tested the relationship between aquatic respiratory rates, body size, and sex in red devil vampire crabs (Geosesarma hagen) at two ecologically-relevant temperatures. We found small females respire more than small males at 28{degrees}C, while large females respire more than large males at 21{degrees}C. Additionally, body size is a significant factor affecting respiratory rates of both sexes at 21{degrees}C and warmer temperatures significantly increase respiration in small crabs of both sexes. Interactions between these factors also led to emerging trends that can be explained by both physiological rules, such as reproductive investment and surface-to-volume ratios and heat transfer. We also report a temperature coefficient (Q10) of 1.52 for this species, showing an expected 52% change in respiratory and metabolic rate for every 10{degrees}C increase. This work also demonstrates the importance of understanding how and to what extent biological variables like sex and body size interact with abiotic environmental factors when measuring physiological traits in ectothermic invertebrate animals. What is already knownAs crabs colonize terrestrial environments, they undergo adaptive physical and physiological changes in their respiratory abilities. Few studies have examined these respiratory shifts in individual terrestrial crab species using modern respirometry tools and techniques and across different submersion states and biotic and abiotic factors. We quantify how temperature, body size, and sex affect aquatic respiratory rates in adult terrestrial vampire crabs. What this study addsWe found small females respire more than small males at 28{degrees}C, while large females respire more than large males at 21{degrees}C. Additionally, body size is a significant factor affecting respiratory rates of both sexes at 21{degrees}C and warmer temperatures significantly increase respiration in small crabs of both sexes. Interactions between these factors also led to emerging trends that can be explained by both physiological rules, such as reproductive investment and surface-to-volume ratios and heat transfer. We also report a temperature coefficient (Q10) of 1.52 for this species, showing an expected 52% change in respiratory and metabolic rate for every 10{degrees}C increase.

physiology↗

bioRxiv2026

Convergent lignocellulose degradation in terrestrial crabs is driven by distinct host genus-specific microbial communities

BackgroundRestrictions on the types of food available on land have repeatedly triggered the convergent evolution of herbivory in terrestrial animals. This pattern also holds true in many terrestrially adapted crabs, which have independently colonized land more than 17 times since the Cretaceous, and many clades are now almost completely herbivorous, standing in contrast to the ancestral pattern of detrivory. While many bacteria possess efficient pathways for degrading lignin and cellulose, the role of gut microbiomes in facilitating these dietary shifts in terrestrial crabs remains poorly understood. To explore the relationship between microbial community structure and the ability of land crabs to digest lignocellulose, we conducted read-based and assembly-based metagenomic analyses on feces collected from the guts of 14 crab species across six genera, representing a gradient of terrestriality from the lower intertidal zone to forested habitats. ResultsWe generated 129 metagenome-assembled genomes (MAGs) that represent key members of these gut microbial communities, establishing a foundational resource for future studies on crab-microbiome interactions. We found that host genus explained most of the variation in bacterial community composition, while degree of terrestrial adaptation (i.e. terrestrial grade) explained a smaller proportion. We also identified multiple bacterial genera that strikingly differed in relative abundance across terrestrial grades, crab genera, and diet type. Broad-scale functional analyses of general carbon metabolism across crabs revealed an absence of complete pathways in crabs from lower terrestrial grades, suggesting a functional divergence in gut communities linked to habitat transition. Fine-scale functional analyses of carbohydrate-active enzyme (CAZyme) domains allowed us to connect specific MAGs to lignocellulose degradation pathway genes, demonstrating that different crab genera harbor distinct microbial taxa that have similar CAZyme profiles in their guts. ConclusionsThis work provides a foundational metagenomic resource for genomic exploration of microbial communities in terrestrial crab guts. These results suggest that the gut microbiomes of terrestrially adapted crabs are structured primarily by host identity and have convergently acquired microbes with similar functions to help perform lignocellulose degradation. Overall, different degrees of adaptation to terrestrial environments, including resulting dietary shifts, may be responsible for functional divergence in crab gut community assembly.

microbiology↗

bioRxiv2024

Transcriptomic responses of gecarcinid land crabs to acute and prolonged desiccation stress

Decapod crabs have repeatedly and convergently colonized land. Because of their aquatic ancestry, desiccation is their greatest physiological challenge, yet the genetic basis of their responses to desiccation are unknown. For this study, we sought to identify osmoregulatory genes that were differentially expressed in their antennal glands and posterior gills in response to desiccation stress. We dehydrated and tracked gene expression across three confamilial species displaying increasing degrees of terrestrial adaptation: Tuerkayana celeste, T. magna, and Gecarcoidea natalis. We observed acute dramatic upregulation in the posterior gills of T. celeste and G. natalis and a more muted response in T. magna; however some genes with known osmoregulatory functions were downregulated throughout the trial. We also found that some modules of orthologous genes with correlated expression were associated with greater degrees of terrestriality whereas others reflected shared ancestry, suggesting that different parts of the transcriptome are under varying degrees of terrestrial selective pressure. Finally, while differentially expressed genes were likely to be conserved across the three species, genes from expanded gene families and species-specific genes may also play a role in how land crabs adapt to the unique selective challenges that accompany a terrestrial life.

evolutionary biology↗

bioRxiv2022

Convergent adaptation of true crabs (Decapoda: Brachyura) to a gradient of terrestrial environments

For much of terrestrial biodiversity, the evolutionary pathways of adaptation from marine ancestors are poorly understood, and have usually been viewed as a binary trait. True crabs, the decapod crustacean infraorder Brachyura, comprise over 7,600 species representing a striking diversity of morphology and ecology, including repeated adaptation to non-marine habitats. Here, we reconstruct the evolutionary history of Brachyura using new and published sequences of 10 genes for 344 tips spanning 88 of 109 brachyuran families. Using 36 newly vetted fossil calibrations, we infer that brachyurans most likely diverged in the Triassic, with family-level splits in the late Cretaceous and early Paleogene. By contrast, the root age is underestimated with automated sampling of 328 fossil occurrences explicitly incorporated into the tree prior, suggesting such models are a poor fit under heterogeneous fossil preservation. We apply recently defined trait-by-environment associations to classify a gradient of transitions from marine to terrestrial lifestyles. We estimate that crabs left the marine environment at least seven and up to 17 times convergently, and returned to the sea from non-marine environments at least twice. Although the most highly terrestrial- and many freshwater-adapted crabs are concentrated in Thoracotremata, Bayesian threshold models of ancestral state reconstruction fail to identify shifts to higher terrestrial grades due to the degree of underlying change required. Lineages throughout our tree inhabit intertidal and marginal marine environments, corroborating the inference that the early stages of terrestrial adaptation have a lower threshold to evolve. Our framework and extensive new fossil and natural history datasets will enable future comparisons of non-marine adaptation at the morphological and molecular level. Crabs provide an important window into the early processes of adaptation to novel environments, and different degrees of evolutionary constraint that might help predict these pathways.

evolutionary biology↗