Biology subjects

Hammel, J.

Publications and source records attributed to Hammel, J..

3 recordsLinked to original sources

bioRxiv2025

Claws that snap: the raptorial mechanism of dryinid wasps

Prey capture is a key selection pressure, often favoring extreme performance morphologies. Many mechanisms of prey capture, however, remain poorly understood. In this study, we document the remarkable raptorial behavior and evolutionary biomechanics of the "pincer wasps" (Hymenoptera: Dryinidae). Dryinid claws, previously thought to function as simple vises (Nachtigall-&-Nachtigall-1974), are shown to possess "snap traps", or claws that close rapidly upon prey contact. Detailed morphological analysis, using synchrotron-radiation microtomography (SR-{micro}-CT), reveals that all long-clawed dryinids can overcenter their specialized anterior pretarsal claws, presumably allowing elastic energy storage in the pretarsal apodemes. Uniquely, explosive release of this energy, leading to claw closure, appears to occur not through active withdrawal of a latch, but as the direct consequence of contact with the prey: impact hyperextends a specialized trigger-joint complex of the tarsus, pulling the claw back into undercenter alignment, and so freeing the stretched apodeme to fully recoil. Such a "contact trigger" is eminently useful, as these trap-claw wasps prey on insects with explosive jump capacity; by linking trap shutting with prey contact, success chances are increased. Paleontological and allometric analyses suggest that the raptorial behavior likely preceded the evolution of overcentering, which appears to have evolved via release from developmental constraint on anteroposterior symmetry, leading to a distinct scaling rule. These findings expand the documented diversity of spring-loaded biological mechanisms and establish Dryinidae as a promising system for studying how developmental constraints, mechanical demands, and functional innovation shape ecomorphological diversity. HIGHLIGHTSO_LIDryinidae catch prey with spring-loaded trap claws, relying on a unique direct-action trigger. C_LIO_LIRaptorial behavior evolved first, followed by the functional derivation of two separate components. C_LIO_LIThe evolution of novel raptorial mechanism was enabled by release of ancestral developmental constraint. C_LI

evolutionary biology↗

bioRxiv2025

Engineered lymphatic stroma model applications in central nervous system leukemia

Central nervous system (CNS) involvement frequently occurs in acute lymphoblastic leukemia (ALL), but many questions remain about how leukemia cells access, persist in, and exploit the CNS. The CNS is protected by the meninges, which are fluid filled membranes that surround the brain. Within the meninges, meningeal lymphatic vessels drain cerebrospinal fluid to cervical lymph nodes for immunosurveillance, a potential pathway for leukemia cell migration into or egress from the CNS. Here, we utilize tissue engineered models of the meningeal lymphatics and lymph node stroma to probe how leukemia cells interact with these key tissues. We first demonstrate that standard-of-care chemotherapeutics can damage meningeal lymphatic barriers. Next, we showed that soluble factors from the meningeal lymphatics can support leukemia cell growth while soluble factors from the lymph node model under flow can promote leukemia cell migration. Finally, we show that leukemia cells migrate through the lymph node model under both static and flow conditions. Overall, we have demonstrated the feasibility of using engineered lymphatic models to study leukemia cell behavior in the CNS with the goal of expanding the available experimental platforms for understanding CNS metastasis and relapse. Insight BoxLeukemia commonly infiltrates the central nervous system (CNS), requiring intensive CNS-directed therapies that are often ineffective and cause both acute and long-term toxicities, especially in pediatric patients. The meningeal lymphatics and the deep cervical lymph nodes constitute a pivotal axis in CNS immunity, facilitating drainage of fluid and waste and enabling peripheral immune surveillance in response to CNS-derived signals. Here, we employ in vitro models of the meningeal lymphatics and lymph node stroma to demonstrate their crosstalk in influencing leukemia cell growth and migration. These engineered platforms serve as valuable tools for uncovering mechanistic insights into the meningeal-lymph node axis in the context of CNS-leukemia relapse.

bioengineering↗

bioRxiv2023

Bite force transmission and mandible shape in grasshoppers, crickets, and allies is largely dependent on phylogeny, not diet

Although organ systems evolve in response to many intrinsic and extrinsic factors, frequently one factor has a dominating influence. For example, mouthpart shape and mechanics are thought to correlate strongly with aspects of the diet. Within insects, this paradigm of a shape-diet connection is advocated for decades but the relationship has so far never been quantified and is mostly based on qualitative observations. Orthoptera (grasshoppers, crickets, and allies) are a prominent case, for which mandible shape and dietary preference are thought to correlate strongly and even lead to predictions of feeding preferences. Here, we analysed mandible shape, biting efficiency, and their potential correlation with dietary categories in a phylogenetic framework for a broad sampling of several hundred extant Orthoptera covering nearly all families. The mandibular mechanical advantage was used as a descriptor of gnathal edge shape and bite force transmission efficiency. We aimed to understand how mandible shape is linked to biting efficiency and diet, and how these traits are influenced by phylogeny and allometry. The investigation reveals that feeding ecology is not the unequivocal predictor of mandible shape that it was assumed to be. There is a strong phylogenetic signal suggesting that phylogenetic history does have a much more prevalent influence on gnathal edge shape and distal mechanical advantage, than, e.g., feeding guilds or the efficiency of the force transmission to the food. Being ancestrally phytophagous, Orthoptera evolved in an environment with abundant food sources so that selective pressures leading to more specialized mouthpart shapes and force transmission efficiencies were low.

evolutionary biology↗