Abstract
Physalia physalis and Velella velella, are among the few marine organisms that harness the wind for their locomotion, whereas other cnidarian jellyfish make use of their pulsating bell-shaped bodies to propel themselves through the seas. We investigate their composition and metabolism compared with two species of pulsating scyphozoan jellyfish, Aurelia aurita and Pelagia noctiluca. Protein (P), lipid (L), carbohydrate (K), and derived energy content (Ec), provided information on the biochemical composition of these species and their relevance as prey. Physiological respiration (R) from oxygen consumption. As well as potential respiration (Φ) from the electron transport system (ETS) activity and the derived respiratory carbon demand (RCD) and heterotrophic energy transformation (HET), allow the comparison of the impact of these two types of propulsion on the metabolism, along with the impact of these organisms as predators. In this study it was found that these hydrozoans depicted a different biochemical composition relative to other gelatinous zooplankton. Lower water content at around 90% was observed, while WM-specific P, L, K, and Ec were higher, showcasing new aspects of these species as prey. The lower R/P in P. physalis and V. velella (1.8 ± 0.7 and 2.9 ± 1.1 μL O2 h–1 mg Prot–1, respectively) and the low R/Φ, around 0.1, indicate lower respiration in wind-driven propulsion compared to pulsation-driven propulsion. Additionally, these results encourage the use and research on enzymatic techniques that are particularly useful for gelatinous research, and the calculation of RCD and HET helps in understanding the physiology and role played by the organisms as predators from carbon and energy perspectives.
Highlights
There is a growing interest in gelatinous zooplankton in ocean ecosystems (Chiaverano et al, 2018; Ruzicka et al, 2020; Wright et al, 2021)
Games-Howell statistical analysis showed a significant difference between the results of the scyphozoans and P. physalis (p < 0.01); it did not show a significant difference between the scyphozoans and V. velella
The composition of P. physalis and V. velella varies from other gelatinous zooplankton
Summary
There is a growing interest in gelatinous zooplankton in ocean ecosystems (Chiaverano et al, 2018; Ruzicka et al, 2020; Wright et al, 2021). The neuston, known as pleuston, is the ecosystem located on the ocean surface, comprising of a unique community of floating organisms, such as Sargassumtype seaweeds, wind-propelled cnidarians, and other floating invertebrates. This highly dynamic surface layer fosters the exploration of various lifestyles and locomotion strategies and connects disparate atmospheric and oceanic habitats (Helm, 2021). Several studies have investigated the formation of dense aggregations by some jellyfish and their impact on prey populations (Malej, 1989a; Mills, 1995; Schneider and Behrends, 1998; Hansson et al, 2005; Ishii and Tanaka, 2006; Condon et al, 2011; Boero, 2013; Iguchi et al, 2017; Schiariti et al, 2018). Carbon demand, associated with the respiratory activity can be calculated from the respiration measurements, which can help in the estimation of the impact on prey populations (Purcell et al, 2010; Lilley et al, 2014; Iguchi et al, 2017)
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