Physiological and Behavioral Plasticity of the Sea Cucumber Holothuria forskali (Echinodermata, Holothuroidea) to Acidified Seawater

Abstract

Research into the effects of reduced pH caused by rising CO2 on echinoderms has been strongly biased toward those groups which rely heavily on calcification, such as sea urchins. There is very limited information available for groups that are less reliant on calcification, such as sea cucumbers. Moreover, plasticity in physiology and behavior in holothurians, which is considered to be critical to cope with ocean acidification, remains even less understood. Here, we examined the effects of a 22-week exposure to three pH levels (pH 7.97, 7.88, and 7.79) on the responses of adult Holothuria forskali. This is an abundant and ecologically important sea cucumber in shallow waters of the northeast Atlantic and Mediterranean. The holothurians did not exhibit serious acidosis after a 4-week gradually decreased pH exposure, possibly due to the slow acclimation period. After an additional 18 weeks of exposure, coelomic acid–base parameters did not differ significantly among the pH treatments, whereas they were higher than in week 4. Gonad development, defense behavior, and the structure and Ca2+ and Mg2+ concentrations of calcareous endoskeleton deposited in the body wall were all unaffected by decreased levels of seawater pH. No statistical differences were found after 22 weeks, and adult H. forskali showed strong physiological and behavioral plasticity to the effects of lowered seawater pH. While the interpretation of our results is restricted due to small sample sizes, this first long-term study of the effects of seawater acidification on sea cucumbers revealed resilience within the wide natural range of pCO2 found in NE Atlantic coastal waters.

The effects of stocking density on physiological traits in Holothuria forskali broodstock

“…This in turn would require more frequent and active interventions in the tanks, which could lead to rising levels of stress on captive individuals. Despite general sea cucumber species faring well in organically charged environments (Yuan et al., 2018), an unchecked growth of biofilm could lead to a higher consumption of oxygen in the tanks (Li & Chen, 1994), especially at night which is the period of most activity for sea cucumbers (Dong et al., 2011; Hammond, 1982). This surge in oxygen uptake could lead to a rise in stress, which in turn could lead to increased evisceration and mortality rates (Santos, 2017; Tonn et al., 2016).…”

Optimizing Growth and Rearing Techniques for Larvae and Juveniles of the Sea Cucumber Holothuria arguinensis

“…Sea cucumbers possess an important ecological role in the ecosystems they inhabit, from bioturbation of sediments to nutrient recycling [1]. However, they are most notably procured for their reputation as a nutritionally rich food resource as well as a very coveted medicinal supplement.…”

Antifungal activity of selected sea cucumber species from Tukuran, Zamboanga del Sur, Mindanao, Philippines using modified SPOTi assay

“…Sea cucumbers are marine benthic organisms with elongated bodies distributed on the sea floor worldwide. They occupy a wide range of marine habitat, from tropical to polar areas and intertidal zone to deep oceans (Yuan et al 2018); with extreme conditions that require them to adapt to survive. These organisms have remarkable biodiversity in Asia Pacific region, with 1716 species (Bahrami et al 2014).…”