Cellular, Hormonal, and Behavioral Responses of the Holothuroid Cucumaria frondosa to Environmental Stressors

Abstract

Holothuroids (sea cucumbers) are one of the most ubiquitous groups of benthic animals found across diverse marine ecosystems. As echinoderms, they also occupy an important place in the evolutionary hierarchy, sitting close to vertebrates in the deuterostome clade, making them valuable multidisciplinary model organisms. Apart from being ecologically and phylogenetically important, many species are commercially exploited for luxury seafood markets. With the global rise of aquaculture and fisheries, management and protection of these valuable species relies on a better understanding of how their immune systems respond to environmental and anthropogenic stressors. Here, the cellular, hormonal and behavioral indicators of stress in the North Atlantic sea cucumber Cucumaria frondosa were examined. The immediate and carry-over (post recovery) effects of a 1-hour exposure to low salinities or to emersion (at two temperatures) highlighted that morphoplasticity in C. frondosa was accompanied by shifts in all monitored indicators. From baseline levels measured in controls, densities of free coelomocytes increased, showing successions of specific cell types and subsequent coelomocyte aggregations, combined with a rise in cortisol levels. These responses mirrored increased fluctuations in cloacal opening rates, decreased force of attachment to the substrate, and enhanced movements and active buoyancy adjustment with increasingly severe stressors. The findings suggest that many systems of sea cucumbers are impacted by stresses that can be associated with harvesting and handling methods, with likely implications for the quality of the processed products. Gaining a deeper understanding of immune and hormonal responses of sea cucumbers is not only of broad ecological and evolutionary value, but also helpful for the development of sustainable fisheries and aquaculture practices, and conservation programs.

Comparative physiological study of sea cucumbers from eastern waters of United States

“…the species studied in this research as C. frondosa was the biggest species compared to the other two. Other studies supported our results as the authors showed that higher coelomocyte counts and enhanced concentration of phagocytes were seen over time when C. frondosa was induced with stress [20,33]. In our result for differential cell count, we also saw that C. frondosa had a significantly high number of phagocytic cells, which could indicate a better immune response.…”

“…Other studies supported our results as the authors showed that higher coelomocyte counts and enhanced concentration of phagocytes were seen over time when C . frondosa was induced with stress [ 20 , 33 ]. In our result for differential cell count, we also saw that C .…”

Time-Course of the Innate Immune Response of the Terrestrial Crustacean Porcellio scaber After Injection of a Single Dose of Lipopolysaccharide

“…It is known that the number of hemocytes changes dramatically after live bacteria and viruses or microbial polysaccharides such as LPS, laminarin, and β1,3-glucan (i.e., M/PAMPs) are introduced into the body of invertebrates ( 12 – 14 , 22 ). This parameter has thus been used as a measure of stress and/or the physiological conditions of different species, including crustaceans ( 21 , 37 , 39 , 40 ). In the present study, injection of LPS into the body of P. scaber resulted in a rapid decrease in the numbers of free hemocytes (by 3 h), followed by recovery to the baseline control levels 6 h after challenge.…”

Is Holothuria tubulosa the golden goose of ecological aquaculture in the Mediterranean Sea?

“…In openwater, but with another species (H. poli), a recent study also observed significant growth, but low survival, of juveniles over 1 year (Cutajar et al 2022). Sea cucumbers are stresssensitive with physiological responses observed in response to environmental changes (Jobson et al, 2021;Hou et al, 2019;Kamyab et al, 2017). Performing a longer experiment allows the sea cucumbers to recover from environmental stress applied and acclimate to the new conditions.…”