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Sea cucumbers are economical and ecologically important species, playing a crucial role in nutrient recycling in the ocean and providing valuable bioactive compounds for nutrition. Previous research has demonstrated that microplastic fibers, which are widely recognized as emerging contaminants, are transferred to the perivisceral coelomic fluid during respiration in sea cucumbers; however, their fate in sea cucumbers is still not well understood. We tracked the status of sea cucumbers (Apostichopus japonicus) with polyester microplastic fibers in their coelomic fluid in clean water. The results showed that after transferring sea cucumbers to clean water, the number of microplastic fibers transferred significantly decreased in the coelomic fluid, but at least one microplastic fiber was found up to 60 days. In addition, sea cucumbers recovered from the effect of microplastic fiber transfer, as indicated by enzyme levels and histological observations. Furthermore, single microplastic fiber transfer over a 60‐day farmed period did not significantly affect the growth of sea cucumbers. However, repetitive microplastic fiber transfer (i.e., twice and thrice a week over 60 days) significantly decreased the growth rate (p < 0.05). Accordingly, increasing microplastic fibers in sea cucumber habitats pose a threat to sea cucumbers because they can disrupt development. Thus, farmers are advised to select locations for farming sea cucumbers where low microplastic fiber concentrations are expected. Environ Toxicol Chem 2023;42:205–212. © 2022 SETAC [ABSTRACT FROM AUTHOR]

The body colour of sea cucumber, Apostichopus japonicus (Selenka), is an important trait affecting the price and taste of its products; the rare white and purple colour types are favoured and are more expensive in China. Identification of factors that may contribute to the differences among white, green and purple sea cucumbers will provide a scientific basis for improving the cultivability of the rare colour morphs. In this study, the growth, histology, ultrastructure and expression of microphthalmia-associated transcription factor ( MITF) and astacin of two newly discovered white and purple colour morphs were investigated and compared with the common green morph, in the same breeding environment. At 50 days old, the growth and survival rates and the extent of pigmentation were the highest in purple, then green colour morphs and were lowest in white morphs. The white morph had fewer, and less developed, epidermal melanocytes compared with the green and purple colour morphs. MITF and astacin expression, which are necessary for the formation of melanin and astaxanthin, respectively, were highest in purple morphs and lowest in white morphs. In addition, there were significant differences in growth rates and expression of MITF and astacin among early, mid and late pigmentation stages of each colour morph. The results suggested that growth and survival rates were highest in purple sea cucumber and lowest in white sea cucumber. Epidermis thickness and melanin content may be the newfound factors contributed to the differences in growth and survival rate among three colour morphs. [ABSTRACT FROM AUTHOR]

We evaluated the effect of rearing density on the yield of a fast-growing and heat-resistant strain of Apostichopus japonicus using a full-sib family. We analysed the relationship between density and key growth parameters during factory seedling of A. japonicus and developed a model to explain the variation in growth. From 130 to 220 days, the rearing density of A. japonicus had a significant effect on body weight, specific growth rate, coefficient of variation and survival rate ( P < 0.05). We obtained predicted integral regression equations for yield and growth rate, density fluctuation, variable coefficient fluctuation and survival rate. Specific growth rate had a significant effect on the yield of A. japonicus and, therefore, can be used as a primary indicator of yield. We recommend that stocking density should be adjusted from age 130-166 days to avoid frequent seedling separation to different pools of different seedling sizes during the fast growth period of A. japonicus seedlings, a procedure that causes yield decline. The optimal initial stocking density was 24.4 g m−2 (0.2 g L−1). [ABSTRACT FROM AUTHOR]

Using incomplete diallels cross and North Carolina II design, this study established sea cucumber families with heat-resistant and fast-growing Apostichopus japonicus strains from different ecological areas. Then, this study analyzed the influence of paternal and maternal genetic effects on the growth of A. japonicus, evaluated the growth effect of different A. japonicus families in the early growth stage and estimated the combining ability and heritability. The study showed that, in the early growth stage of A. japonicus, the influence of paternal genetic effects on the growth was higher than that of maternal effects. The best five parents and eight offspring families in terms of genetic potential breeding and growth were selected. The 3-month weight, 9-month weight, 12-month weight, 5-month to 9-month specific growth rate, 9-month coefficient of variation (CV) and 12-month CV of A. japonicus are at moderate heritability level, in order, 28.18, 40.82, 43.56, 27.87, 44.39 and 38.59 %, respectively; these traits played a leading role in parental additive gene effect on the formation of hybrids offspring traits. [ABSTRACT FROM AUTHOR]

To determine whether marine mud substrate is suitable for sea cucumber aquaculture, we studied the effects of sea mud on the behavioral characteristics, growth and survival of Apostichopus japonicus, in both the field and laboratory. Our results showed that sea mud is beneficial for the growth of A. japonicus, but was unfavorable for its locomotion and attachment when a water current was present. In the field experiment in Yuehu lagoon, juvenile A. japonicus preferred to inhabit the base of seaweeds or dead leaves, which provide a favorable substrate for both their locomotion and ingestion. The mud substrate was not suitable for the small juveniles to inhabit; therefore, >3.25 g ind is the preferred size for bottom-sowing culture of sea cucumbers on the seabed in a field environment such as the Yuehu lagoon. Water current is a key factor influencing sea cucumber distribution on the bare mud substrate, with 90 % of juvenile sea cucumbers (<40 g ind) being unable to keep still in a current speed of 0.115 m s for 10 min. In conclusion, a mud substrate is suitable for A. japonicus aquaculture, although hard substrates or shelters are a prerequisite for successful rearing. The water current is a key factor that influences substrate selection by A. japonicus and, thus, is an important factor to be considered in the bottom-sowing culture of these organisms. [ABSTRACT FROM AUTHOR]

Albinism in the sea cucumberApostichopus japonicus(Selenka) may be a significant biomarker that can be used to obtain information about behaviors and growth of this species. The goal of this study was to compare the behaviors and growth rate between albino and normalA. japonicus. Total light intensity and specific growth rate were used as statistical indices. Diverse light intensities were tested in the laboratory and in the field to identify ecological characteristics of albinoA. japonicus. Experimental results revealed that: (1) both albino and normal specimens had negative phototaxis; (2) normalA. japonicuswere more responsive to intense light than albino species, and the latter could withstand longer periods of exposure to intense light; (3) normalA. japonicusgrew faster than albino specimens; and (4) both normal and albinoA. japonicusgrew faster in natural light than in the other light intensities tested. [ABSTRACT FROM PUBLISHER]

Abstract: Powdered algae is an essential ingredient in the artificial diet of the sea cucumber Apostichopus japonicus (Selenka) in aquaculture systems. In this study, growth performance, apparent digestibility coefficients, and ammonia-nitrogen production of A. japonicus fed six different granulated macroalgae diets (Sargassum thunbergii, Sargassum polycystum, Zostera marina, Ulva lactuca, Laminaria japonica and boiled L. japonica) were quantified for 60d to identify the optimal diet for this species. The type of seaweed ingested greatly affected the growth, ingestion rate, digestibility, and ammonia-nitrogen production of A. japonicus. Sea cucumbers grew faster when fed the U. lactuca or L. japonica diet than when fed the S. thunbergii or S. polycystum diet. The ingestion rate was much higher when fed the U. lactuca, L. japonica, Z. marina, or boiled L. japonica diet than when fed the S. thunbergii or S. polycystum diet. The apparent digestibility coefficients of the test diets ranged from 9.63% to 15.84%. Ammonia-nitrogen production was much lower in A. japonicus fed the U. lactuca or L. japonica diet compared to the other seaweed diets. The results of this study indicate that U. lactuca and L. japonica are optimum seaweeds for use in the culture of the commercially valuable sea cucumber A. japonicus. [Copyright &y& Elsevier]

Abstract: Suspension aquaculture of filter-feeding bivalves has been developing rapidly in coastal waters in the world, especially in China. Previous studies have demonstrated that dense populations of filter-feeding bivalves in shallow water can produce a large amount of faeces and pseudofaeces (biodeposits) that may lead to negative impacts on the benthic environment. To determine whether the deposit feeder Stichopus (Apostichopus) japonicus Selenka can feed on bivalve biodeposits and whether the sea cucumber can be co-cultured with bivalves in suspended lantern nets, three experiments were conducted, two in tanks in the laboratory and one in the field. In a 3-month flow-through experiment, results showed that sea cucumbers grew well with specific growth rate (SGR) reaching 1.38% d−1, when cultured in the bottom of tanks (10m3 water volume) where scallops were cultured in suspension in lantern nets. Moreover, results of another laboratory experiment demonstrated that sea cucumbers could survive well on bivalve biodeposits, with a feeding rate of 1.82±0.13g dry biodeposits ind−1 d−1, absorption efficiency of organic matter in biodeposits of 17.2%±5.5%, and average SGR of 1.60% d−1. Our longer-term field experiments in two coastal bays (Sishili Bay and Jiaozhou Bay, northern China) showed that S. japonicus co-cultured with bivalves also grew well at growth rates (0.09–0.31g wet weight ind−1 d−1) depending on individual size. The results suggest that bivalve lantern nets can provide a good habitat for sea cucumbers; and the co-culture of bivalve molluscs with sea cucumbers may provide an additional valuable crop with no additional inputs. [Copyright &y& Elsevier]

Abstract: In recent years, bivalve feces and powdered algae have been used as the food sources of holothurians in China. In this study, growth and energy budget for sea cucumber Apostichopus japonicus (Selenka) with initial wet body weights of 32.5±1.0g (mean±SE, n =45) when fed with five different granule diets containing dried bivalve feces and/or powdered algae in water temperature 13.2–19.8°C and salinity 30–32ppt were quantified in order to investigate how diets influence growth and energy distribution and to find out the proper diet for land-based intensive culture of this species. Results showed that diets affected the food ingestion, feces production, food conversion efficiency and apparent digestive ratios, hence the growth and energy budget. Sea cucumbers fed with dried feces of bivalve showed poorer energy absorption, assimilation and growth than individuals fed with other four diets; this could be because feces-drying process removed much of the benefits. Dried bivalve feces alone, therefore, were not a suitable diet for sea cucumbers in intensive cultivation. The mixed diets of feces and powered algae showed promising results for cultivation of sub-adult Apostichopus japonicus, while animals fed with powdered algae alone, could not obtain the best growth. According to SGR of tested animals, a formula of 75% feces and 25% powdered algae is the best diet for culture of this species. Extruded diets were used in the present experiment to overcome shortcomings of the traditional powdered feeds, however, it seems a conflict exists between drying bivalve feces to form extruded diets and feeding sea cucumbers with fresh feces which contain beneficial bacteria. Compared with other echinoderms, in holothurians the energy deposited in growth is lower and the energy loss in feces accounts for the majority of the ingested energy. Such detailed information could be helpful in further development of more appropriate diets for culture of holothurians. [Copyright &y& Elsevier]

Abstract: Shrimps Litopenaeus vannamei with initial body weight of 2.108±0.036 g were sampled for specific growth rates (SGR) and body color measurements for 50 days under different light sources (incandescent lamp, IL; cool-white fluorescent lamp, FL; metal halide lamp, MHL; and control without lamp) and different illumination methods (illumination only in day, IOD, and illumination day and night, IDN). Body color of L. vannamei was measured according to the free astaxanthin concentration (FAC) of shrimp. The SGR, food intake (FI), feed conversion efficiency (FCE) and FAC of shrimps showed significant differences among the experimental treatment groups (P <0.05). Maximum and minimum SGR occurred under IOD by MHL and IDN by FL, respectively (difference 56.34%). The FI of shrimp for the control group did not rank lowest among treatments, confirming that shrimp primarily use scent, not vision, to search for food. FI and FCE of shrimps were both the lowest among treatment groups under IDN by FL and growth was slow, thus FL is not a preferred light source for shrimp culture. Under IOD by MHL, shrimps had the highest FCE and the third highest FI among treatment groups ensuring rapid growth. FAC of shrimp were about 3.31±0.20 mg/kg. When under IOD by MHL and IDN by FL, FAC was significantly higher than the other treatments (P <0.05). To summarize, when illuminated by MHL, L. vannamei had not only vivid body color due to high astaxanthin concentration but also rapid growth. Therefore, MHL is an appropriate indoor light source for shrimp super-intensive culture. SGR of shrimp was in significantly negative correlation to FAC of shrimp (P <0.05). Thus, when FAC increased, SGR did not always follow, suggesting that the purpose of astaxanthin accumulation was not for growth promotion but for protection against intense light. [Copyright &y& Elsevier]

Abstract: Fed fish farms produce large amounts of wastes, including dissolved inorganic nitrogen and phosphorus. In China, fish mariculture in coastal waters has been increasing since the last decade. However, there is no macroalgae commercially cultivated in north China in warm seasons. To exploit fish-farm nutrients as a resource input, and at the same time to reduce the risk of eutrophication, the high-temperature adapted red alga Gracilaria lemaneiformis (Bory) Dawson from south China was co-cultured with the fish Sebastodes fuscescens in north China in warm seasons. Growth and nutrient removal from fish culture water were investigated in laboratory conditions in order to evaluate the nutrient bioremediation capability of G. lemaneiformis. Feasibility of integrating the seaweed cultivation with the fed fish-cage aquaculture in coastal waters of north China was also investigated in field conditions. Laboratory seaweed/fish co-culture experiments showed that the seaweed was an efficient nutrient pump and could remove most nutrients from the system. Field cultivation trials showed that G. lemaneiformis grew very well in fish farming areas, at maximum growth rate of 11.03% day− 1. Mean C, N, and P contents in dry thalli cultured in Jiaozhou Bay were 28.9±1.1%, 4.17±0.11% and 0.33±0.01%, respectively. Mean N and P uptake rates of the thalli were estimated at 10.64 and 0.38 μmol g− 1 dry weight h− 1, respectively. An extrapolation of the results showed that a 1-ha cultivation of the seaweed in coastal fish farming waters would give an annual harvest of more than 70 t of fresh G. lemaneiformis, or 9 t dry materials; 2.5 t C would be produced, and simultaneously 0.22 t N and 0.03t P would be sequestered from the seawater by the seaweed. Results indicated that the seaweed is suitable as a good candidate for seaweed/fish integrated mariculture for bioremediation and economic diversification. The integration can benefit economy and environment in a sustainable manner in warm seasons in coastal waters of north China. [Copyright &y& Elsevier]

Apostichopus japonicus is one of the main aquaculture species in northern China. The green tide macroalgae Chaetomorpha linum and the seagrass Zostera marina occur in this region. Our previous study has suggested that Z. marina detritus can be a food source for A. japonicus . In the present study, we carried out a laboratory simulation experiment for 60 days to understand whether C. linum can also be utilized to fulfill the nutrient demands of A. japonicus . The powdered C. linum and Z. marina detritus, mixed in five ratios (100:0; 75:25; 50:50; 25:75; 0:100), were fed to sea cucumbers along with muddy sediment in a fixed proportion. Sargassum thunbergii (40%) combined with the muddy sediment (60%) was also used as a standard reference/control diet. Results showed that the specific growth rates (SGRs), food utilizing efficiencies and energy budgets of A. japonicus were strongly influenced by the ratio of C. linum and Z. marina in their diets. The growth energy deposited in the bodies of sea cucumbers fed higher proportions of C. linum was significantly higher than those fed higher proportions of Z. marina . Furthermore, sea cucumbers fed on C. linum and S. thunbergii had similar growth performances. This study indicated that C. linum could replace S. thunbergii as a food source for A. japonicus . Statement of relevance Because of its high nutritive and medical properties, the sea cucumber Apostichopus japonicus has become a highly valuable fishery and aquaculture species in Asia. Influenced by eutrophication in coastal waters, blooming events of the green tide algae Chaetomorpha linum are increasing around the world, including some natural habitats for A. japonicus in northern China. However, whether C. linum can also be utilized to fulfill the nutrient demands of sea cucumbers, such as A. japonicus , is unknown. We carried out a laboratory simulation experiment for 60 days to study this question. Our results showed that sea cucumbers fed on C. linum and Sargassum thunbergii had similar performances. Due to its higher protein and lower cellulose contents, C. linum was easier for A. japonicus to digest and absorb, and more energy per unit of food was converted to growth. This study indicated that C. linum could act as a food source for A. japonicus . The results of this research are also beneficial for promoting the collection and control of C. linum . [ABSTRACT FROM AUTHOR]