Hoyos, M. | bioRxiv Science

bioRxiv2025

Scraping the Surface: First Records of Cleaning Associations Between Sharks and Oceanic Manta Rays

Interspecific scraping behaviors among large marine vertebrates may serve as an important mechanism for ectoparasite removal. Here, we present the first documented observations of shark-manta scraping interactions, which occurred in the Revillagigedo Archipelago, a remote marine protected area in the eastern tropical Pacific. Opportunistic video footage was collected at two dive sites between December 2024 and February 2025, capturing three discrete events in which Galapagos sharks (Carcharhinus galapagensis) initiated contact with three different oceanic manta rays (Mobula birostris). Using a focal-animal sampling approach, we quantified the number and rate of scraping events and categorized responses. Sharks scraped against mainly the ventral surfaces of mantas using their heads, gill regions, and lateral areas associated with high ectoparasite loads. Manta responses ranged from passive tolerance to active evasion, with the strongest reactions observed in response to the adult Galapagos shark. Scraping rates varied by site and shark size. These interactions occurred at or near established cleaning stations, suggesting that sharks may opportunistically use mantas as alternative cleaning substrates. While this may indicate behavioral plasticity among sharks, it raises concern about potential costs to mantas, particularly if some ectoparasites or pathogens are transferred. Our findings highlight the complexity of shifting ecological interactions among marine megafauna and underscore the importance of understanding behavioral responses to cleaning disruption for endangered oceanic mantas.

ecology↗

bioRxiv2020

Self-organization and culture of Mesenchymal Stromal Cell spheroids in acoustic levitation

In recent years, 3D cell culture models such as spheroid or organoid technologies have known important developments. Many studies have shown that 3D cultures exhibit better biomimetic properties compared to 2D cultures. These properties are important for in-vitro modeling systems, as well as for in-vivo cell therapies and tissue engineering approaches. A reliable use of 3D cellular models still requires standardized protocols with well-controlled and reproducible parameters. To address this challenge, a robust and scaffold-free approach is proposed, which relies on multi-trap acoustic levitation. This technology is successfully applied to Mesenchymal Stromal Cells (MSCs) maintained in acoustic levitation over a 24-hour period. During the culture, MSCs spontaneously self-organized from cell sheets to cell spheroids with a characteristic time of about ten hours. Each acoustofluidic chip could contain up to 30 spheroids in acoustic levitation and four chips could be ran in parallel, leading to the production of 120 spheroids per experiment. Various biological characterizations showed that the cells inside the spheroids were viable, maintained the expression of their cell surface markers and had a higher differentiation capacity compared to standard 2D culture conditions. These results open the path to long-time cell culture in acoustic levitation of cell sheets or spheroids for any type of cells.

bioengineering↗