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Simple Summary: The worth of sea urchin gonads in the market is determined by their specific features connected to size and texture. Compared with wild counterparts, farmed sea urchins fed formulated feeds showed faster gonad growth but worse gonad texture traits, such as adhesiveness, cohesiveness, hardness, springiness, chewiness, and gumminess. Thus, it is pressing to enunciate the underlying mechanisms and find solutions to solve this problem. As the most abundant collagen, collagen type I is momentous for improving the hardness, springiness, and chewiness of muscle as verified. Vitamin C is vital for participating in the regulation of hydroxyproline biosynthesis, which is an essential component of collagen. However, the effects of vitamin C addition on the collagen synthesis and underlying mechanisms remain poorly understood in any sea urchin species. Therefore, this study aims to investigate the impact of vitamin C on the gonad growth, texture, collagen content, and the expression of genes involved in the collagen synthesis of sea urchin (Mesocentrotus nudus). These results could contribute to precisely quantify the vitamin C addition in the diets to produce gonads with high texture quality in sea urchin. The market value of sea urchin gonads is determined by the specific characteristics associated with gonad size and texture. Formulated feeds can effectively promote the gonad growth of sea urchins but cannot assure essential gonad texture traits. The objective of this study was to investigate the impact of vitamin C (VC) on the gonad growth, texture, collagen content, and the expression of genes involved in the collagen synthesis of sea urchins (Mesocentrotus nudus). Graded amounts of VC (0, 3000 and 6000 mg/kg) were supplemented to make three formulated feeds. Fresh kelp (Saccharina japonica) was used as the control diet. Each diet was randomly distributed to three tanks of M. nudus. The results indicated that the gonadosomatic index (GSI) and texture traits of M. nudus fed C3000 were significantly greater than those fed C0 and C6000. Collagen type I (Col I) in the gonads of M. nudus fed C3000 showed significantly greater areas than those fed C0 and C6000. Consistently, the expression levels of collagen alpha-1 (colp1α) of M. nudus fed C3000 were significantly higher than those fed C0 and C6000. As for the transforming growth factor beta (tgf-β)/Smads pathway, the expression levels of collagen synthesis genes (tgf-β receptor 1 and 2, smad nuclear-interacting protein 1 (snip1) and prolyl 4-hydroxylase subunit beta (p4hβ)) in the C3000 group were significantly greater than those in the C0, C6000 and kelp groups. On the contrary, the expression levels of collagen degradation genes (lysyl oxidase-like 2 (loxl2) and matrix metalloproteinase 14 (mmp14)) in the C3000 group were significantly lower than those in the C0, C6000 and kelp groups. In conclusion, VC at an addition level of 3000 mg/kg significantly increased the gonad texture and collagen contents of M. nudus, which could be accomplished by increasing collagen synthesis and inhibiting collagen degradation through the tgf-β/Smads pathway. These results could contribute to better understanding the beneficial effects of VC addition on the gonad texture quality of M. nudus. [ABSTRACT FROM AUTHOR]

A 70-day feeding experiment was performed to investigate the effects of dietary vitamin E at different addition levels (0, 100, 200, and 400 mg/kg) on the growth, collagen content, antioxidant capacity, and expressions of genes related to the transforming growth factor beta (TGF-β)/Sma- and Mad-related protein (SMAD) signaling pathway in sea cucumbers (Apostichopus japonicus). The results showed that the A. japonicus in the group with 200 mg/kg vitamin E exhibited significantly higher growth rates, hydroxyproline (Hyp) and type III collagen contents, and superoxide dismutase (SOD) activity, as well as the upregulation of genes related to Tenascin, SMAD1, and TGF-β. Additionally, the A. japonicus in the group with 100 mg/kg vitamin E exhibited significantly higher body-wall indexes, denser collagen arrangements, improved texture quality, higher activities of glutathione peroxidase (GSH-Px) and peroxidase (POD), as well as the upregulation of genes related to collagen type I alpha 2 chain (COL1A2), collagen type III alpha 1 chain (COL3A1), and Sp-Smad2/3 (SMAD2/3). In contrast, the A. japonicus in the group with 400 mg/kg vitamin E showed a decrease in the growth rates, reduced Hyp contents, increased type I collagen contents, collagen fiber aggregation and a harder texture, along with the downregulation of genes related to the TGF-β/SMAD signaling pathway. Furthermore, the A. japonicus in the group with 400 mg/kg exhibited oxidative stress, reflected by the lower activities of SOD, GSH-Px, and POD. These results indicated that A. japonicus fed diets with the addition of 100–200 mg/kg vitamin E had improved collagen retention and texture quality by increasing the activities of antioxidant enzymes and the expressions of genes in the TGF-β/SMAD signaling pathway. However, the excessive addition of vitamin E (400 mg/kg) induced oxidative stress, which could increase the collagen degradation and fibrosis and pose a threat to the growth and texture quality of A. japonicus. [ABSTRACT FROM AUTHOR]

Simple Summary: Sea urchin is rare but valuable and considered luxurious sea food due to the gonads with bright color, delicate taste, and abundant nutrition. Since macroalgae have several defects, such as unstable supply, low feed conversion efficiency, and incomplete nutrition, it is essential to formulate feeds suitable for producing sea urchin seeds with higher efficiency. Vitamin E (VE) is an essential nutrient and a lipid-soluble antioxidant for animals. However, no relevant information is available about the requirement of VE and its physiological role in sea urchins. Therefore, this experiment was performed to assess the impacts of dietary VE on growth, intestinal microbiota, immune response, and related gene expression in juvenile S. intermedius. It was found that a moderate level of VE (172.5–262.4) can achieve ideal digestive enzyme activities and growth performance, but a relatively higher level of VE (235–302 mg/kg) was beneficial for maintaining the immune and antioxidant capacity of juvenile S. intermedius by regulating the expression of inflammation- and immune-related genes and abundance of some bacteria to a healthy state. A 90 d feeding experiment was conducted to investigate the effects of vitamin E (VE) on growth, intestinal microbiota, immune response, and related gene expression of juvenile sea urchin (Strongylocentrotus intermedius). Six dry feeds were made to contain graded levels of VE (78, 105, 152, 235, 302, and 390 mg/kg); these were named E78, E105, E152, E235, E302, and E390, respectively. Dry feed E50 and fresh kelp (HD) were used as the control diets. There were six replicates of cages in each dietary group, and each cage held 20 sea urchins with an initial body weight of approximately 1.50 g. Results exhibited that weight gain rate and gonadosomatic index (GSI) of the sea urchins were not significantly affected by dietary VE ranging from 78 to 390 mg/kg. Sea urchins in the dry feed groups showed poorer growth performance, but significantly higher GSI than those in the fresh kelp groups. The pepsin and lipase activities were not significantly promoted by low or moderate VE, but were inhibited by a high level of VE (302–390 mg/kg), while amylase and cellulase activities were significantly increased by low or moderate VE, with the highest values observed in the E105 and E235 groups, respectively. VE addition at a low dosage (105–152 mg/kg) showed inhibitory effects on immune and antioxidant enzyme activities and expression of inflammation-related genes, but showed no beneficial effects at moderate or high dosage (235–390 mg/kg), while a moderate or relatively higher level of VE (235–302 mg/kg) significantly increased the expression of several immune-related genes. The relative abundance of Proteobacteria, Actinobacteria, Ruegeria, and Maliponia in the intestine of the sea urchins increased with the increase in VE in the dry feeds. On the contrary, the relative abundance of the Firmicutes, Bacteroidetes, Escherichia-Shigella, Bacteroides, and Clostridium sensu stricto 1 gradually decreased as VE content increased. These results indicated that a moderate level of VE (172.5–262.4) can achieve ideal digestive enzyme activities and growth performance, but a relatively higher level of VE (235–302 mg/kg) was beneficial for maintaining the immune and antioxidant capacity of juvenile S. intermedius by regulating the expression of inflammation- and immune-related genes and abundance of some bacteria to a healthy state. [ABSTRACT FROM AUTHOR]

A 56‐day feeding experiment was performed to investigate the effects of the dietary lipid level on the survival, growth performance, digestive enzyme activities and antioxidant capacity of Eriocheir sinensis reared under three salinities. Six feeds with graded levels of lipids (5%, 7%, 9%, 11%, 13% and 15%) were formulated by including fish oil as the main lipid source. Sixty crab individuals (initial weight: 0.21 ± 0.02 g) were assigned to each aquarium. In total, 18 aquariums were distributed under each salinity condition. Each feed was randomly allocated to three parallel tanks of crabs. The feeding experiment lasted for 56 days. Results showed that the survival rate of E. sinensis fed diets with 7%–15% lipids just showed a decreasing tendency as the salinity increased. The highest weight gain rate (WGR) was found in the treatment with 11%, 9% and 5% lipid at the salinity of 0.5‰, 2‰ and 6‰ respectively. At the salinity of 0.5‰, 2‰ and 6‰, the highest activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase) were detected in the treatments with 11%, 13% and 7% lipid respectively. As the salinity increased, the protein and lipid contents showed an increasing trend, while the moisture content showed an opposite trend. At each salinity, arachidonic acid and docosahexaenoic acid increased, while saturated fatty acids and monounsaturated fatty acids decreased with the increase of dietary lipid level. These results indicated that increasing salinity resulted in decreased antioxidant enzyme activities and increased malondialdehyde content in the juvenile E. sinensis, especially when they were fed diets with relatively higher lipid level. Based on WGR, digestive enzyme activity and antioxidant capacity, the optimal lipid level was estimated to be 8.28–13%, 7.54–13% and 5–8.89% for juvenile E. sinensis reared at the salinity of 0.5‰, 2‰ and 6‰ respectively. [ABSTRACT FROM AUTHOR]

A study was conducted to investigate the effects of dietary n‐3 LC‐PUFA on the growth performance, fatty acid profile, transcription of related genes and intestinal microflora in adult sea urchin (Strongylocentrotus intermedius). Kelp (Laminaria japonica) and four formulated feeds with graded levels of n‐3 LC‐PUFA (0%, 0.5%, 0.8% and 1.0% dry diet) were prepared as the experimental diets. Each diet was randomly allocated to ten adult sea urchin individuals. The feeding period lasted for 90 days. Results showed that gonadosomatic index (GSI) of adult S. intermedius fed formulated feeds was significantly higher than that fed kelp (p < 0.05), while weight gain rate (WGR) showed no significance between kelp and feed groups (p > 0.05). Neither WGR nor GSI showed significant differences among the four feed treatments (p > 0.05). Notably, ARA and EPA in the gonads of S. intermedius fed the feeds devoid of n‐3 LC‐PUFA were comparable to that fed the feeds with 0.5% n‐3 LC‐PUFA (p > 0.05). Transcription of Elovl4 and Δ5‐desaturase in the intestine and gonad significantly decreased as dietary n‐3 LC‐PUFA increased (p < 0.05). Proteobacteria and Bacteroidetes (phylum level) and Psychromonas and Sulfurimonas (genus level) were the most abundant bacteria species in the intestine of S. intermedius. The abundance of Sulfurimonas was comparable in the S. intermedius fed kelp and the feed with 0% n‐3 LC‐PUFA, which was significantly higher than that fed the other formulated feeds (p < 0.05). These results indicated that S. intermedius seems to have a low requirement for n‐3 LC‐PUFA to sustain its normal growth and gonad development. The increased transcription of rate‐limiting enzymes (Elovl4 and Δ5‐desaturase) could be responsible for the considerable amounts of EPA and ARA in the gonads of S. intermedius when fed feeds without LC‐PUFA. The intestinal microflora were affected to a certain extent by the die categories and the n‐3 LC‐PUFA in the formulated feeds. It is speculated that some unknown bacteria in the genus of Sulfurimonas could participate in the synthesis of LC‐PUFA. [ABSTRACT FROM AUTHOR]

This experiment was conducted to compare the effects of three lipid sources on the growth and gonad development in juvenile sea urchin (Strongylocentrotus intermedius). Kelp (Laminaria japonica) and three formulated feeds with the supplementation of fish oil (FO), linseed oil (LO) or soybean oil (SO) as the sole lipid source. Results showed that sea urchins fed kelp had significantly higher weight gain rate (WGR) but lower gonadosomatic index (GSI), than those fed formulated feeds (p <.05). WGR and GSI of sea urchins fed SO were significantly lower than that fed LO and FO (p <.05). The content of EPA in the gonad of sea urchins fed LO was significantly higher than that fed SO (p <.05). The content of ARA in SO was higher than that in FO and LO (p >.05). The expression of elongase 4, Δ6 desaturase and Δ5 desaturase was significantly lower in the intestine of sea urchins fed FO than that fed LO and SO (p <.05). These results indicated that LO and FO, but not SO were the ideal lipid sources for the juvenile S. intermedius. The elevated transcription of fatty acid synthesis‐related genes could be responsible for the increased EPA and ARA deposition in LO and SO, respectively. [ABSTRACT FROM AUTHOR]

Feeding regime is an important concern for sea urchin aquaculture. However, optimal feed regimes have not been established for land-based sea urchin ventures using a formulated feed. In this study, we investigated the effects of short-term continuous and intermittent feeding regimes on food consumption, growth, gonad production and quality of the sea urchin Strongylocentrotus intermedius (54.90 ± 2.28 mm of test diameter) fed a formulated feed. The results showed that (1) compared with initial conditions, all involved traits except a* (test diameter, test height, body weight, gonad weight, gonad index, gonad moisture, L* and b*) showed significant increase at the end of the experiments; (2) only the longest term feed regime tested in this trial (S2) significantly negatively affected growth and gonad production of S. intermedius fed a formulated feed; (3) there was a trend but this was not significant for inhibiting gonad development of S. intermedius in intermittent feeding regimes and there was no change in the gonad colour and sweetness; (4) S0.5 (fasting half day and then feeding half day) is the optimal intermittent feeding regime for S. intermedius fed a formulated feed. To our knowledge, the present study is the first report of finding an effective intermittent feeding regime for land-based cultured sea urchins of relatively large size, and thus has direct application potential in the field of aquaculture. [ABSTRACT FROM PUBLISHER]

An 8-week feeding trial was conducted to investigate the effects of dietary chitosan oligosaccharide complex with cerium (Ce IV) ( COS-Ce) on growth performance, nonspecific immunity and disease resistance of sea cucumber, Apostichopus japonicas. Five isonitrogenous (18.6%) and isolipidic (1.1%) practical diets were formulated with graded level of COS-Ce (0, 150, 300, 600 and 1200 mg kg−1 dry feed), which were named as COS-Ce/0, COS-Ce/150, COS-Ce/300, COS-Ce/600, COS-Ce/1200 respectively. Each diet was allocated to four replicates of sea cucumbers (Initial weight: 6.72 ± 0.02 g). Sea cucumbers were fed to apparent satiation once daily (19:00 hours) for 56 days. During the experiment, water temperature was kept at 16 ± 0.5°C, pH 7.8-8.2, dissolved oxygen beyond 5 mg L−1, ammonia nitrogen below 0.5 mg L−1 and salinity from 30‰ to 31‰. Results showed that the specific growth rate of sea cucumbers was significantly higher in COS-Ce/600 than that in other four treatments. Activities of phagocytosis, respiratory burst, acid phosphatase and alkaline phosphatase in COS-Ce/600 were significantly higher than that in COS-Ce/0 ( P < 0.05) respectively. On the contrary, cumulative mortality was the lowest in COS-Ce/600 following 14 days exposure to Vibrio splendidus ( P < 0.05). In conclusion, these results confirmed that dietary COS-Ce had beneficial effects on growth performance, nonspecific immunity and disease resistance of sea cucumber. [ABSTRACT FROM AUTHOR]