PeerJ 2026 Jun 02;14:e21358. doi: 10.7717/peerj.21358.

Individual response in basal metabolism and nutritional composition to asexual reproduction in tropical sea cucumber Holothuria atra.

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BACKGROUD: Asexual reproduction via fission plays a vital role in the survival of the sea cucumber Holothuria atra. However, the energetic and nutritional mechanisms driving its regenerative capacity remain poorly understood. METHOD: Fission was induced in the sea cucumber Holothuria atra by constricting the mid-body with a rubber band. Following fission, the resulting fragments were designated as anterior (A) and posterior (P) based on their original body orientation. The growth, oxygen consumption, ammonium (NH4 +) excretion rates and biochemical composition were then assessed in both anterior and posterior fragments at 10, 20, 30, 40, 50 and 60 days post-fission regeneration. RESULTS: Induced fission generated anterior and posterior fragments. Both fragments exhibited significant weight loss, with a 31.6% reduction observed by day 10. Routine metabolic rates (RMR) were elevated during regeneration, particularly in anterior fragments, which peaked at 1.06 ± 0.46 mg O2 h-1 g-1 DW (dry body weight) by day 40. Simultaneously, increased ammonia excretion rates indicated a reliance on protein catabolism as a primary energy source (O:N ratio < 10). Despite these metabolic shifts, the proximate biochemical composition (levels of protein, lipid and carbohydrate) remained largely stable during the regeneration. An exception was a transient peak in specific fatty acids (e.g., C18:1n-9, MUFA) at day 30, which may be associated with membrane synthesis. Moreover, posterior fragments showed higher carbohydrate mobilization by day 50 (p < 0.05). CONCLUSION: These findings suggest that H. atra may maintain homeostasis during fission by modulating metabolism rather than depleting stored nutrients, possibly entering a hypometabolic state to conserve energy. This study highlights the resilience of H. atra to asexual reproduction stressors and underscores the need for further research on exogenous nutrient absorption during regeneration.

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