Jordano, Mayara de A.
Morandini, Andre C.
Nagata, Renato M.
Total Authors: 3
 Univ Sao Paulo, Inst Biociencias, Dept Zool, Rua Matao, Trav 14, 101, BR-05508090 Sao Paulo, SP - Brazil
 Univ Sao Paulo, Ctr Biol Marinha, Rodovia Manuel Hypolito do Rego Km 131-5, BR-11600000 Sao Sebastiao, SP - Brazil
 Univ Fed Rio Grande, Inst Oceanog, Av Italia, Km 8, BR-96203000 Rio Grande, RS - Brazil
Total Affiliations: 3
Journal of Experimental Marine Biology and Ecology;
Web of Science Citations:
Some organisms can compensate for changes in the fluid environment (Re), through behavioral or morphological responses, but it is not known whether their filtering structures could respond to such changes. Among filter-feeding organisms, scyphomedusae have a feeding mechanism based on vortices produced by bell pulsations, which carry fluids toward post-bell structures (tentacles and oral arms) where food particles are retained. To understand if variations in the physical environment (temperature and viscosity) could determine functional shapes or dimensions of feeding structures to compensate for these variations, we cultivated two scyphomedusae species, Lychnorhiza lucerna and Cassiopea andromeda, in different temperatures. Bell and oral-arm filtering structures (digitata) were measured and compared among treatments. Temperature influenced the bell and digitata development (p < 0.001). Ephyrae at lower temperatures filled the umbrella margin more slowly, and developed smaller bells and longer, more spaced and thicker digitata. At lower temperatures, the thickness of the boundary layer around the digitata and the bell marginal lobes increases as the viscosity of the fluid environment increases (i.e., Reynolds number, Re). Therefore, neighboring structures can operate as a continuous structure due to the overlap of their surrounding boundary layers. On the oral arms, the potential overlap of the boundary layers around adjacent digitata could reduce or obstruct the flow between these structures and hinder particle filtration. However, the morphology of the digitata developed differently at the different temperatures, which may compensate for potential boundary-layer overlapping effects. Scyphomedusae proved to be resilient to different developmental temperatures and exhibited different growth patterns that maintained the functionality of the swimming and feeding structures. This phenotypic plasticity suggests the existence of a survival mechanism for filter-feeding jellyfish in a wide range of temperatures. Therefore, we consider whether characteristics of the physical environment (e.g., temperature and viscosity) could determine, to some extent, the functional shapes and dimensions of the feeding structures of filter-feeding gelatinous organisms. (AU)