Effects of Photoperiod on Growth, Digestive Enzyme Activity, Stress, and Oxidative Status of Juvenile Chinese Soft-Shelled Turtles (Pelodiscus sinensis) in a Greenhouse

Abstract

HIGHLIGHTSArtificial sunlight with the main components of UVB, UVA, and visible light was used to investigate the influence of photoperiod on large-scale farming of juvenile Chinese soft-shelled turtles in a greenhouse.The effects of photoperiod on digestive enzyme activity, stress, and oxidative status of juvenile Chinese soft-shelled turtles were revealed.The optimal photoperiod for juvenile Chinese soft-shelled turtles reared in a greenhouse was 0 h light:24 h dark.Abstract. To improve light conditions for soft-shelled turtles in a greenhouse, the effects of photoperiod on growth, digestive enzyme activity, stress, and oxidative status of juvenile Chinese soft-shelled turtles were investigated. In this study, juvenile Chinese soft-shelled turtles were reared under three photoperiods (hours light:hours dark), i.e., 0L:24D, 6L:18D, and 12L:12D) for four months. Results demonstrated that differences in growth were insignificant during the experiment, but the growth parameters of final weight, weight gain rate (WGR), and feed conversation ratio (FCR) were better at 0L:24D, and the survival rate was significantly higher at 0L:24D than at 12L:12D. Regarding digestive function, serum trypsin activity was significantly higher at 0L:24D than at 6L:18D, while lipase activity was significantly higher at 0L:24D than at 12L:12D. For the stress response parameters, serum cortisol level was significantly lower in turtles exposed to 0L:24D compared to the other treatments. With regard to antioxidant enzyme activities, the total antioxidant capacity (T-AOC) was significantly lower at 0L:24D compared to the other treatments, while superoxide dismutase (SOD) activity was significantly higher in turtles exposed to 0L:24D. The activity of glutathione peroxidase (GSH-PX) was significantly lower at 0L:24D than at 12L:12D. The malonaldehyde (MDA) activity was a little lower at 0L:24D than at 6L:18D; however, it significantly decreased in turtles exposed to 12L:12D. On the whole, the results indicated that the photoperiod treatments had no significant effects on the growth of juvenile Chinese soft-shelled turtles, while extended light exposure may cause physiological stress in turtles. Considering the survival rate, digestive function, cortisol level, and oxidative status, it is suggested that juvenile soft-shelled turtles should be reared under a 0L:24D photoperiod. Keywords: Chinese soft-shelled turtle, Digestive enzyme activity, Growth, Oxidative status, Photoperiod, Stress.

The Photoperiod Significantly Influences the Growth Rate, Digestive Efficiency, Immune Response, and Antioxidant Activities in the Juvenile Scalloped Spiny Lobster (Panulirus homarus)

“…Total darkness (0 L:24 D) has been reported to maximize LPS and AMS activities in the fairy shrimp (Branchinecta orientalis) [45,46], while a prolonged photoperiod (18 L:6 D) affects LPS and TRYP activities in spotted sea bass (Lateolabrax maculatus) [23]. Similarly, the highest TRYP and LPS activities in the Chinese soft-shell turtle were observed in complete darkness (0 L:24 D) [30].…”

“…It exerts a profound influence on various physiological processes and feeding behaviors in aquatic animals [22], modulating growth performance and developmental stages [23][24][25]. Notably, light impacts the growth and development of diverse species, including fish [26,27], shrimp [28], crabs [29], other crustaceans [22], and turtles [30], along with various physiological responses. As a pivotal environmental element, light is instrumental in regulating the circadian rhythms of these organisms [31].…”

Seasonality and growth in tropical freshwater ectotherm vertebrates: Results from 1‐year experimentation in the African gray bichir, giraffe catfish, and the West African mud turtle

“…But, in some tropical fish species, the correlation has been reported to be negative, as in Clarias gariepinus , which shows increased growth in the complete night with short day length (Almazán‐Rueda et al, 2005 ; Mustapha et al, 2012 ), and in Labeo rohita where prolonged photoperiod negatively affected growth (Shahjahan et al, 2020 ). In some cases, no photoperiod effect has been identified, as in the catfish Lophiosilurus alexandri (Kitagawa et al, 2015 ) or the Chinese softshell turtle Pelodiscus sinensis (Li et al, 2020 ; Xianqing et al, 1999 ).…”

Effects of Extreme Light Cycle and Density on Melatonin, Appetite, and Energy Metabolism of the Soft-Shelled Turtle (Pelodiscus sinensis)

“…Photoperiod is one of the most crucial signal factors that regulate the proper phasing of behavioral and physiological variables such as feeding, energy metabolism, and neuroendocrine functions [1]. Nowadays, in terms of light control for culture purposes or environmental problems, how animals will respond to extreme light cycles (herein meaning constant darkness or constant light) has received great attention [2][3][4], with the focus mostly on birds and rodents. The soft-shelled turtle Pelodiscus sinensis is a freshwater reptile with great economic value, living at the bottom of water with dim light with a preference to feed in the dark [5].…”

“…The soft-shelled turtle Pelodiscus sinensis is a freshwater reptile with great economic value, living at the bottom of water with dim light with a preference to feed in the dark [5]. It has been reported that 24 h of darkness is beneficial to the feeding and growth of the soft-shelled turtle [3,5]; however, the underlying physiological mechanism is not yet clear. Few studies have explored the effect of light on physiological processes in turtles.…”