Growth of wild pearl oysters <Emphasis Type="Italic">Pinctada fucata,Pinctada margaritifera</Emphasis> and <Emphasis Type="Italic">Pinctada sugillata</Emphasis> (Bivalvia: Pteriidae) in Taiwan

In order to understand growth features of pearl oysters in the genus Pinctada, i.e. Pinctada fucata, Pinctada margaritifera, and Pinctada sugillata in Taiwan, a total of 3062 wild individuals of these species from juvenile to adult were collected monthyly from March 2001 to April 2002 in Jukeng, Pingtung County, south-west Taiwan. Quantitative measurements of live oysters were conducted for shell height (SH), shell length (SL), shell width (SW), hinge length (HL), and wet weight (WW). Different cohorts were identified through multiple length frequency analysis on SH of P. fucata and P. margaritifera, and growth curves with seasonal variation were estimated for these species. Pinctada fucata in Taiwan had a different seasonal growth pattern from the Japanese population, but had similar growth rates during the high growth period. The growth rate of P. margaritifera in Taiwan was slower than in French Polynesia, the Solomon Islands, and the Red Sea. Comparisons of morphological growth features among the three species show large differences in the SW-related features. Pinctada fucata in Taiwan had larger SW than in Japan and Korea. The differences in growth rates and morphological features suggested that the wild Taiwanese oysters may retain genetically pristine characteristics, thus genetic conservation might be urgently needed.     

Growth and biometric relationships of the pearl oyster Pinctada fucata (Gould) on transplanting from the Gulf of Mannar to the Arabian Sea

Comparative studies were made on the growth and biometric relationships of the pearl oyster Pinctada fucata (Gould) Tuticorin stock at (Tuticorin (TST) – parent stock) transplanted from the Tuticorin Bay (8.7°N; 78.2°E) in the Gulf of Mannar along the Indian southeast coast to Kollam Bay (8.8°N; 76.5°E) in the Arabian Sea along the Indian southwest coast (Tuticorin stock at Kollam (TSK) – transplanted stock). At the time of transplantation, Kollam Bay did not have a native stock, however, within a year, the transplanted stock spawned and oyster spats were collected from within the farm (Kollam stock (KS) – progeny stock). The growth in dorso‐ventral measurement and total weight in Kollam Bay was 1.4–1.6 times and 3.1 to 6.8 times respectively greater than that observed at Tuticorin. Furthermore, at Kollam Bay, the thickness observed at the end of first year was similar to that obtained at the end of second year in Tuticorin. Both the TSK and KS had significantly higher instantaneous growth rates (IGR) than TST. All the stocks displayed significantly different biometric relationships. The increased growth in Kollam Bay is attributed to the almost double productivity in the Arabian Sea compared with the Bay of Bengal. It is concluded that in the case of P. fucata, the site and its interaction with environment are important determinants of growth and shell dimensions. The present study clearly indicates that the environmental conditions prevailing along the southeast Arabian Sea are congenial for the growth, gametogenesis, spawning and settlement of P. fucata larvae. In spite of strong monsoonal influences in the hydrology of Kollam Bay, the growth and reproduction of P. fucata stocks indicates its relative hardiness and ability to adapt to a changed environment.     

Genetic parameters of growth and resistance to Polydora ciliata in the pearl oyster Pinctada fucata

The pearl oyster Pinctada fucata is an economically important oyster cultured for pearl production in China. In this study, we used an animal model to estimate the variance components and genetic parameters of growth traits and a sire‐dam threshold model to estimate the resistance of P. fucata to polychaete Polydora ciliata. The results showed that the heritability estimates were 0.3850 ± 0.1421 for shell width, 0.3478 ± 0.1292 for body weight and 0.3387 ± 0.1316 for resistance to P. ciliata, and significantly different from zero (P < 0.05). Both phenotypic and genetic correlations were high between shell width and body weight (0.935 and 0.883 respectively) (P < 0.01), but low between resistance and shell width (0.260 and 0.233 respectively)/body weight (0.152 and 0.083 respectively) (r < 0.30; P > 0.05). The higher heritabilities for shell width, body weight and resistance traits suggested that the three traits can be genetically improved through selective breeding, but the low correlation between growth and resistance traits suggested that the resistance trait can be effectively improved through index selection or through hybridization of two specialized lines, i.e. a high‐resistant line and a high growth line.     

First studies of embryonic and larval development of Coilia nasus (Engraulidae) under controlled conditions

Herein, we describe the embryonic and larval development stages of Coilia nasus, an anadromous fish that is indigenous to the Yangtze River and the northwest region of the Pacific Ocean. The success of artificial breeding programmes and modern methods of reproduction allowed us to accurately describe the development stages of C. nasus. These stages were recorded using a binocular microscope and a digital camera‐equipped microscope, and histological and scanning electron microscopy observations were also conducted. Development can be divided into four periods: embryonic, prelarval, larval and juvenile. The fertilized eggs were spherical, transparent, non‐adhesives and buoyant, with an average diameter of 0.80±0.10 mm. Complete early embryonic development took place within 40–43 h post hatching, and the new hatchlings were 2.85±0.20 mm long. The mouth openings (0.25–0.35 mm) appeared at day 6 post hatching. Complete metamorphosis took place by day 60, at which time the larvae transformed into juveniles (65±5.8 mm) and attained skin coloration.     

Effect of dietary fish oil replacement by rapeseed oil on the growth,fatty acid composition and serum non‐specific immunity response of fingerling black carp,Mylopharyngodon piceus

An 8‐week experiment on fingerling black carp Mylopharyngodon piceus was conducted to evaluate the effects of dietary fish oil (FO) supplement on growth, fatty acid composition and non‐specific immunity responses. Five triplicate fingerling groups (initial weight = 2.72 ± 0.35 g) were fed isoenergetic and isonitrogenous diets in which the dietary FO was replaced with rapeseed oil (RO) in graded increments of 25% (0–100%). No significant effects were observed on specific growth rates, survival rates and feed conversion ratios, but there were significant differences in whole body moisture and liver lipid contents (P < 0.05), and the 100% RO replacement diet significantly enhanced hepatosomatic indexes compared to control group (P < 0.05). Other approximate whole body constituents, viscerasomatic ratios and condition factors were not influenced by dietary oil treatments. Fatty acid composition of muscle and liver was influenced by dietary fatty acid input, α‐linoleic acid and γ‐linolenic acid were significantly increased with increasing RO, but eicosapentaenoic acid, docosahexaenoic acid and the n‐3/n‐6 ratio were significantly reduced (P < 0.05). Alternative complement pathway, lysozyme and superoxide dismutase activities were not significantly influenced. These results indicate that black carp fed diets with FO supplement had similar growth and non‐specific immunity to the fish fed diet with RO.     

Influence of several non‐nutrient additives on nonspecific immunity and growth of juvenile turbot,Scophthalmus maximus L.

The effects of three non‐nutrient additives on nonspecific immunity and growth of juvenile turbot (Scophthalmus maximus L.) were studied in this feeding experiment. The five treatments are basal diet alone, basal diets containing three different additives [0.4 g kg^?1 of xylo‐oligosaccharides (XOS), 1.3 g kg ^?1 of yeast cell wall and 0.8 g kg ^?1 of bile acids] individually or in combination. Two hundred and twenty‐five turbots (average initial weight 151.3 ± 11.3 g) were randomly allotted in five treatments with three replicates within each treatment in a 72‐day period. Comparing with basal diet group, activities of C3, C4, phagocyte, lysozyme, specific growth rate and feed conversion rate in yeast cell wall, XOS and the combined groups was enhanced significantly (P < 0.05); however, these parameters in bile acid groups were increased slightly (P > 0.05) except for phagocyte (P < 0.05); superoxide dismutase activity in additive groups was not significantly increased (P > 0.05) except for the combined group (P < 0.05). In conclusion, supplementation of yeast cell wall and XOS enhanced the nonspecific immunity of juvenile turbot. Synergistic or additive effect of the three additives was not observed.     

Effects of embryonic exposure to α‐lipoic acid or ascorbic acid on hatching rate and development of zebrafish (Danio rerio)

This study investigates the effects of embryonic exposure to two different antioxidants on growth and development in fish. Zebrafish (Danio rerio) embryos (100 per group) were exposed to lipoic acid (LA, 6–12 μM) or ascorbic acid (AA, 100–200 μM) and the hatching rate, standard lengths (SL) at hatching, development and growth post‐hatching monitored. The SLs at hatching were increased (P<0.05) in both antioxidant‐exposed groups relative to the controls, with no effect on yolk reserves. This enhanced development persisted up to 15 days post hatching. At hatching, cell proliferation rates (P<0.0005) and basic fibroblast growth factor (P<0.001), were greater in the antioxidant‐exposed fish than in the controls (0 μM antioxidant); no oxidative DNA damage was detected (P>0.05). Activity of the endogenous antioxidant enzyme superoxide dismutase was greater (P<0.001) in LA‐treated fish than in the controls. The results suggest that embryonic treatment of zebrafish with LA or AA during embryogenesis enhanced cell proliferation, leading to increased somatic growth in the larval stages, persisting into the juvenile stage. The findings support the treatment of embryonic fish with antioxidants for enhanced results in aquaculture.     

菲律宾蛤仔福建与广东群体的双列杂交

2015年9月–12月,以菲律宾蛤仔福建养殖群体和广东野生群体子一代为亲本,开展了双列杂交实验,建立了两个自交组和两个杂交组,研究了杂交子代幼虫和稚贝的生长与存活的杂种优势。结果显示,各实验组均有较高的受精率和孵化率,但无显著差异。总体上,幼虫期的生长受母体效应影响显著,稚贝期的生长杂交效应主要受交配方式影响。相反,幼虫期的存活受配对方式影响最显著,稚贝期的存活受卵源影响显著。在幼虫期,杂交组与自交组在生长和存活方面差异不显著。在稚贝期,生长表现出明显的杂种优势,壳长和壳高在30日龄以后,正反交组的平均生长速率显著快于自交组。在40日龄时,壳高和壳长总杂交优势值达到最大,分别为25.64和27.00。这可能是因为杂种优势的表达具有时期差异性。在幼虫期,福建自交组表现出最高的存活率,为36.45%±1.85%;稚贝期,广东自交组存活率最高,为52.27%±2.13%。在幼虫期和稚贝期的存活率方面,未观测到杂种优势,这可能是由于两个杂交亲本群体与存活相关的基因频率无差异或者检测次数较少所致。     

Effects of stocking density on growth and non-specific immune responses in juvenile soft-shelled turtle, Pelodiscus sinensis

To investigate the influence of stocking density on the growth and non‐specific immune responses of juvenile soft‐shelled turtle, Pelodiscus sinensis, three groups of turtles (initial body weight 74.2±12.2 g) were reared in 80 cm (L) × 40 cm (W) × 30 cm (H) tanks for 35 days at three stocking densities (StD), which were 1 individuals (ind.) tank⁻¹ (3.13 ind m⁻²) for D1, 4 ind. tank⁻¹ (12.5 ind m⁻²) for D2 and 6 ind. tank⁻¹ (18.75 ind m⁻²) for D3 respectively. D1 was the control group. Turtles were weighted individually at the beginning and at the end of the trial. At the end of the rearing trial, non‐specific immune parameters were determined. The results showed that the heterophil:lymphocyte ratio (HLR) increased and the total plasma protein decreased with increasing StD, suggesting a stress response. Specific growth rate (SGR) significantly decreased with increasing StD. Non‐specific immune indicators such as blood cell phagocytic activity, serum haemolytic activity and serum bacteriolytic activity increased clearly at a higher StD, indicating a pattern of immunoenhancement. The results indicated that at StDs of 4 and 6 ind. tank⁻¹, non‐specific immune responses were not suppressed compared with the control, but were inversely enhanced at the cost of growth reduction. A possible energy‐based trade‐off between growth and constitutive immunity may exist in soft‐shelled turtles.     

Rainbow trout silage as immune stimulant and feed ingredient in diets for Mozambique tilapia (Oreochromis mossambicus)

Peptides and free amino acids resulting from protein hydrolysis could act as stimulants of fish non‐specific immunity. The study aimed to determine the potential of rainbow trout viscera silage as immune stimulant and feed ingredient for Mozambique tilapia, and to establish whether formic acid used during silage preparation contributed to any effects. Four diets were evaluated: a reference diet (R), one containing 6.5 g kg^?1 formic acid (FA) and two silage diets containing 160 g kg^?1 (SL, low inclusion) and 285 g kg^?1 (SH, high inclusion) silage. Low silage inclusion improved phagocytic activity of leucocytes compared with the reference, while high inclusion showed no improvement. No other non‐specific immunity parameters or haematology were affected by any treatments. High silage inclusion significantly decreased growth and led to higher mortality, while formic acid had no effect on growth. It is concluded that rainbow trout viscera silage can stimulate the cellular non‐specific immunity of Oreochromis mossambicus, and that protein hydrolysis products (and not formic acid) is responsible for the stimulation. The silage can also serve as source of dietary protein and essential amino acids in tilapia diets. However, both fish growth performance and improvement in cellular immunity are dependent on silage inclusion level.     

Embryonic and larval development in the semelparous Nereid polychaete Hediste diversicolor (OF Müller, 1776) in Norway: Challenges and perspectives

Knowledge of broodstock manipulation, gametogenesis, artificial fertilization and larval nutrition is a prerequisite to reach a large‐scale production of the polychaete Hediste diversicolor. In this study, the characteristics of oogenesis and spermatogenesis and embryonic and larval development were observed. Moreover, the effect of temperature on embryonic development and effect of diets and sediment on earlier juvenile development were tested. Mature oocytes were characterized by a spherical shape with a diameter of about 200 μm. They showed radial symmetry with a large centric nucleus surrounded by four distinctive layers. Embryo cleavage started between 4 and 10 hr after fertilization, and developed to the swimming trochophore stage after 5–6 days after fertilization at 11°C. The rate of embryonic development increased with a temperature increase from 6.1 to 21.2°C. The trochophore larvae increased in length from day 9 and commenced differentiation into 3‐setiger stage larvae at day 12. The length growth of larvae until 7‐setiger stage was 0.43 mm/day when fed with fish feed, while those fed shellfish diet and smolt sludge both grew around 0.21–0.23 mm/day. The results suggest that fish feed is a superior diet compared to shellfish diets and smolt sludge for the early larval stage of H. diversicolor.     

Pearl formation in the Japanese pearl oyster (Pinctada fucata) by CaCO3 polymorphs: Pearl quality‐specific biomineralization processes and their similarity to shell regeneration

Pearl oyster shell consists of two layers: a calcite prismatic layer (outer layer) and an aragonite nacreous layer (inner layer). Calcite and aragonite are CaCO₃ polymorphs, and their formations are controlled by shell‐forming tissue called mantle. Pearl sacs originating in the mantle form cultured pearls. Therefore, it has been widely accepted that pearl and shell are produced by the same process. However, this idea has been called into question by some recent mineralogical studies indicating microstructural and crystal‐polymorphic diversity in pearls. The pearl biomineralization process is still not fully understood in detail. Thus, in this study, we focused on the diversity of CaCO₃ polymorphism of non‐nacreous structures (NNSs) underlying the nacreous layer in pearl and regenerated shell, to reveal the biomineralization process of the Japanese pearl oyster (Pinctada fucata). Using Meigen's stain and scanning electron microscope‐energy dispersive X‐ray (SEM‐EDX), NNSs polymorphs in valuable and valueless pearls, in addition to regenerated shell, were compared. Aragonite was exclusively observed in the NNSs of valuable pearls, whereas calcite was dominant in those of valueless pearls. The same analysis of NNSs of regenerated shells was carried out. As in valueless pearls, almost all regenerated shell NNSs consisted of calcite, but one NNS was composed of aragonite. Accordingly, it seems that pearls are formed by the same biomineralization process as shell regeneration rather than shell formation.     

Influence of replacing fish meal with enzymatic hydrolysates of defatted silkworm pupa (Bombyx mori L.) on growth performance,body composition and non‐specific immunity of juvenile mirror carp (Cyprinus carpio var. specularis)

This study was conducted to investigate the effects of dietary supplementation of enzymatic hydrolysates of defatted silkworm pupa (EHDSP) on growth performance, body composition and non‐specific immunity of juvenile mirror carp (Cyprinus carpio var. specularis). The control diet (EHDSP0) was produced using fish meal (FM) as the main protein source and the other four diets were formulated by substitution of 25% (EHDSP25), 50% (EHDSP50), 75% (EHDSP75) and 100% (EHDSP100) FM with EHDSP. Five groups containing 270 juvenile mirror carp (14.51 ± 0.03 g) were fed to apparent satiation for 8 weeks. The results indicated that the special growth rate, weight gain, protein efficiency ratio and feed conversion rate of experimental fish in EHDSP25 and EHDSP50 groups were not significantly different from EHDSP0 group (p > .05). The spleen index of experimental fish in EHDSP25 group was significantly higher than that of EHDSP0 group (p < .05). The muscle protein content of experimental fish in EHDSP25 and EHDSP50 groups was significantly higher than that of EHDSP0 group (p < .05). Serum alanine aminotransferase and total cholesterol of experimental fish fed with the EHDSP were significantly lower than that of control (p < .05). The activity of serum superoxide dismutase of experimental fish in EHDSP25, EHDSP50 groups was significantly higher than that of EHDSP0 group (p < .05). Intestinal trypsin activity of EHDSP25 group was significantly higher than that of EHDSP0 (p < .05). In conclusion, EHDSP can be included into diet to replace 50% FM of juvenile mirror carp without negative effect on growth, furthermore, it can improve the non‐specific immunity and function of intestinal tract.     

Application of prospective probionts at early stages of Atlantic cod (Gadus morhua L.) rearing

This work aimed at validating the use of two prospective probionts (Arthrobacter sp. and Enterococcus sp.) at early stages of cod (Gadus morhua L.) rearing. Ova at late post‐fertilized stage and larvae during their first 4 weeks of life were bathed with both probionts, isolated previously from the cod‐rearing environment. This treatment was compared with groups fed rotifers supplemented with a commercial probiotic (Remus^®) and those untreated. Microbiological analyses (total viable counts, presumptive Vibrio and lactic acid bacteria) were performed in rearing systems and larval survival, growth and development were assessed. Larval development was evaluated by proteolytic activity of larval lysates and immunological analysis of important proteins: apolipoprotein A‐I, haemoglobin, C‐reactive protein, C3 and cod serum proteins. Bacterial bathing led to a significantly higher larval weight, length and culturable microbial load in larval gastrointestinal (GI) tract when compared with the control and Remus groups. Development occurred earlier in bathed larvae. However, their survival was negatively affected compared with the control group, but was significantly higher than for the Remus group. The non‐pathogenicity of both probionts was demonstrated by intraperitoneal injection of 13 g cod juveniles. The results suggest that Arthrobacter and Enterococcus probionts affected the larval GI microbiota and contributed to growth, development and digestion, either directly or indirectly.     

Donor effect on cultured pearl nacre development and shell matrix gene expression in Pinctada margaritifera reared in different field sites

Understanding the respective roles played by donor and recipient pearl oysters in pearl quality determination in relation to the environment is a challenge for the pearl industry. In most Pinctada species, pearl size is mainly related to recipient oyster growth performance but also relies to some extent on the biomineralisation activity of the pearl sac, a tissue that originates from the donor oyster mantle. We examined donor effect on pearl size in response to culture in the lagoons on Arutua and Apataki atolls. Overall, nacre weight and thickness were greater in Arutua than in Apataki, but sensitivity to the environment differed between donors. Some donors were associated with significantly heavier and thicker nacre in Arutua (I group), while others had similar results at the two sites (NI group). On average, up to 20% of the pearl size could be attributed to the donor but, in group I, donor effect was responsible for up to 36% of nacre weight determination. Additionally, a real‐time PCR expression study of eight matrix protein genes related to biomineralisation in the pearl sac showed that MSI60, pearlin and pif177 were significantly and positively correlated with nacre weight and thickness, with the latter two genes explaining the larger pearl size observed in Arutua. Donor oysters in P. margaritifera therefore play a key role in pearl size improvement, related to the role of the shell matrix protein genes. Understanding such contributions could help in the design of genetic selection plans for specific and adapted donor oyster lines.     

Dietary supplements of guanosine improve the growth,non‐specific immunity of sea cucumber,Apostichopus japonicus Selenka,and its resistance against Vibrio splendidus

The growth response, non‐specific immune activities and disease resistance were measured in sea cucumber, Apostichopus japonicus Selenka (initial average weight 6.80 ± 0.10 g), when fed diets supplemented with graded levels of guanosine from the guanosine‐5’‐monophosphate disodium (GMP) at 0 (control), 0.3, 0.6 and 1.2 g/kg for 8 weeks. The results showed that GMP supplemented at 0.6 and 1.2 g/kg significantly enhanced the growth of sea cucumber. Sea cucumber fed a diet with 0.6 g/kg of GMP had significantly higher intracellular superoxide anion production, nitric oxide synthase activity, lysozyme activity and the total superoxide dismutase (T‐SOD) activity than those in control group (p < .05). Increased lysozyme activity and T‐SOD activity were also found in sea cucumber fed GMP at 1.2 g/kg. Moreover, there was significantly lower cumulative mortality after the disease challenge in sea cucumber fed the diets with 0.6 and 1.2 g/kg GMP than that in control and 0.3 g/kg GMP groups (p < .05), and no significant difference was observed between 0.6 and 1.2 g/kg GMP groups. These results suggested that feeding GMP at a dose of 0.6 g/kg could enhance growth, non‐specific immunity of sea cucumber as well as its resistance against Vibrio splendidus.     

Development of release methods for captive‐bred freshwater pearl mussels (Margaritifera margaritifera

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Embryonic development and larval and post‐larval growth of the tropical scallop Nodipecten (= Lyropecten) nodosus (L. 1758) (Mollusca: Pectinidae)

This work describes for the first time the embryonic development of the tropical scallop Nodipecten nodosus. Larval and post‐larval growth parameters and some characteristics of larvae shell morphology were also ascertained. The larvae were obtained from the induced spawning of a group of broodstocks under controlled laboratory conditions. After fertilization, larval cultivation was carried out in conical tanks at a temperature of 26–27 °C. Larval density was controlled as a function of larval growth to give 10, 5 and 3 larvae mL^?1 from days 1, 3 and 8 respectively. The larvae were nourished with a 1:1 mix of Isochrysis galbana (clone T‐ISO) and Chaetoceros gracilis in portions varying between 30 000 and 70 000 cells mL^?1. Expulsion of polar groups was observed 5 and 15 min after fertilization, whereas the first cellular division occurred after 30 min. The first gastrule ciliates and trocophore larvae were noted after 8 and 18 h had elapsed, respectively, whereas prodissoconch I, or D‐larvae, were discerned after 26 h. Subsequently, larvae with prodissoconch II or veliger‐conch appeared at 30 h. Larval development continued for 10–12 days, followed by metamorphosis, at an approximate length of 208–230 µm. The growth of the post‐larvae was evaluated for 9 days. Larval and post‐larval growth corresponded to the linear equations L = 71.85 + 10.85t, r² = 0.99, and L = 44.09 + 17.81t, r² = 0.94 respectively. Accordingly, larval morphology and size disparities are discussed with respect to other tropical pectinids.