Induction of triploidy in large yellow crocker Pseudosciaena crocea (Richardson, 1846): effects of pressure shocks and growth performance in the first rearing year

The precociously sexual maturation in large yellow crocker Pseudosciaena crocea has become a serious problem. In an attempt to solve this problem, the production of sterile triploids could be an effective strategy. In this study, triploid P. crocea was obtained by subjecting fertilized eggs to pressure shock. Flow-cytometry analysis was used to assess ploidy level. In terms of triploid rate and hatching rate, the optimal conditions of pressure shock for triploidy induction in P. crocea were 7500 psi for 3 min shock at 3 min after fertilization at 20 degrees C. With the application of these parameters, 100% triploid fish were produced. During the first rearing year, triploid P. crocea had a similar growth performance compared with its diploid counterpart before the age of 8 months and showed a significant advantage at the age of 10 and 12 months in body weight and body length (P < 0.05). At the age of 12 months, the carcass weight of triploids was markedly higher than that of diploid control, and gonadal somatic index was significantly lower than that of their diploid control. During the first rearing year, survival in triploid group was 76.44%, inferior to its diploid control (83.21%).

Improvement of polyploidy induction in Eriocheir sinensis

An incubating temperature of 15 degreesC is used to induce triploidy in Etiocheir sinensis through inhibition of the release of polar body H, and that of 18 degreesC to induce tetraploidy through inhibition of the first cleavage. Flow cytometry is used to identify the ploidy in different developmental stages. For induction of triploidy in fertilized eggs in vitro, the highest induction rate observed in blastula by cytochalasin B, 6-DMAP and KCI is 49.1%, 51.7% and 77.5%, respectively. In the KCI treatment of pregnant crabs with the fertilized eggs, the highest triploid induction rate observed in the zoea is 85.3%. For induction of tetraploidy, the highest induction rate observed in the blastula by cytochaslasin 13, 6-DMAP and KCI is 50.3%, 54.9% and 79.8% respectively. In the KCI treatment of pregnant crabs with the fertilized eggs, the highest induction rate in zoea is 27.3%. Through this study such difficulty as in vitro culture is overcome. Triploid zoea Etiocheir sinensis has been developed for the first time. The induction rate of tetraploid zoea has also been greatly improved.

Optimization of triploid induction by heat shock in Chinese shrimp Fenneropenaeus chinensis

Chromosome manipulation for commercially valuable marine animals plays an important role in aquaculture. The special reproductive characteristics of shrimp make it difficult to control fertilization and synchronize egg development, so research on chromosome manipulation in shrimp has proceeded very slowly. In the present study, triploid shrimp Fenneropenaeus chinensis were induced by heat shocks and the optimal-inducing condition was screened at different spawning temperatures. Level of triploid induction for each treatment was evaluated by flow cytometry at nauplius stage. The highest level of triploid induction reached to more than 90%. Starting time for each treatment was very crucial for triploid induction in shrimp. One optimal treatment condition for triploid induction was heat shock (29-32 degreesC), starting at 18-20 min for duration of 10 min. These conditions varied depending on the temperature at spawning. Triploid level at embryo stage and nauplius stage was not different, suggesting the same hatching rate between diploids and triploids. Heat shock is a very effective way to induce triploids in this species, and can be easily used on large scale without any harmful effect on the environment as compared with chemical treatment. (C) 2003 Elsevier Science B.V. All rights reserved.

Induction and characterization of green pigmentation mutant in Porphyra yezoensis Ueda

The free living conchocelis of Porphyra yezoensis Ueda was treated with N-methyl-N-nitro-N-nitrosoguanidine to induce pigmentation mutants. The artificial green pigmentation mutant of P. yezoensis conchocelis, which was composed entirely of green cells, was isolated through visualization with the unaided eye. The acquired green conchocelis was further developed into a green gametophytic blade. This mutant was relatively stable in color in both gametophytic blade and conchocelis phases. The gametophytic blade mutant was successively cultivated for commerce at some Porphyra farms in Rudong, China, and few wild type or sectorially variegated gametophytic blade occurred, indicating that the green mutant has commercial value. The green mutant was characterized as having lower phycoerythrin and higher phycocyanin content, and SDS-PAGE suggested that phycoerythrin was missing the gamma-subunit in comparison to the wild type. The wild type and the green mutant showed a clear difference in 02 evolution rates in white, green, yellow, and red light, which might be due to the qualitative and quantitative changes of phycoerythrin, and the quantitative difference of phycocyanin. (C) 2008 Elsevier B.V. All rights reserved.

Substrate induction and statistical optimization for the production of chitosanase from Microbacterium sp OU01

The chitosanase production was markedly enhanced by substrate induction, statistical optimization of medium composition and culture conditions by Microbacteritan sp. OU01 in shake-flask. A significant influence of (NH4)(2)SO4, MgSO4 center dot 7H(2)O and initial pH on chitosanase production was noted with Plackett-Burman design. It was then revealed with the method of steepest ascent and response surface methodology (RSM) that 19.0 g/L (NH4)(2)SO4, 1.3 g/L MgSO4 and an initial pH of 2.0 were optimum for the production of chitosanase; colloidal chitosan appeared to be the best inducer for chitosanase production by Microbacterium sp. OU01. This optimization strategy led to the enhancement of chitosanase from 3.6 U/mL to 118 U/mL. (c) 2006 Elsevier Ltd. All rights reserved.

Effects of ultra-violet irradiation on sperm motility and diploid gynogenesis induction in large yellow croaker (Pseudosciaena crocea) undergoing cold shock

Large yellow croaker, Pseudosciaena crocea, exhibit sexually dimorphic growth, with females growing faster and reaching larger adult sizes than males. Thus, development of techniques for preferentially producing females is necessary to optimize production of these species. We have established a protocol to produce all-female croaker P. crocea through induction of meiotic gynogenesis with homologous sperm. The first set of experiments investigated the ultra-violet (UV) irradiation on sperm motility and duration of sperm activity to determine the optimal UV dosage for genetic inactivation of sperm, yet retaining adequate motility for activation of eggs. Milt from several males was diluted 1: 100 with Ringer's solution and UV irradiated with doses ranging from 0-150 J cm (-2). The results indicated that motility and duration of activity generally decreased with increased UV doses. At UV doses greater than 105 J cm(-2), after fertilization, motility was < 10% and fertilization rates were significantly lower. Highest hatching rate was obtained at 75 J cm -2. A second set of experiments was carried out to determine appropriate conditions of cold shock for retention of the 2nd polar body in P. crocea eggs after fertilization with UV-inactivated sperm by altering the timing, temperature and duration of shock. At 208 degrees C, shock applied at 3 min after fertilization resulted in higher survival rate of larvae at 6 h after hatching. Results of different combinations of three shock temperatures ( 28 degrees C, 38 degrees C or 48 degrees C) and five shock durations ( 4 min, 8 min, 12 min, 16 min or 20 min) at 3 min after fertilization demonstrated that shocks of 12 min gave highest production of diploid gynogens. Statistical analysis revealed that maximum production of diploid gynogens (44.55 +/- 2.99%) were obtained at 38 degrees C. The results of this study indicate that the use of UV-irradiated homologous sperm for activation of P. crocea eggs and cold shock for polar body retention is an effective method for producing gynogenetic offspring.

Induction of diploid gynogenesis in turbot Scophthalmus maximus with left-eyed flounder Paralichthys olivaceus sperm

Turbot Scophthalmus maximus exhibits sexually dimorphic growth, with females growing faster and reaching larger adult sizes than males. Thus, development of techniques for preferentially producing females is necessary to optimize production of these species. In this paper, gynogenetic diploids of turbot were induced by activating egg development with ultraviolet (UV)-irradiated left-eyed flounder Paralichthys olivaceus sperm combined with cold shock to prevent extrusion of the second polar body. The results of UV irradiation experiments showed that survival, motility, and duration of activity of P. olivaceus sperm generally decreased with increase in UV dose. The typical Hertwig's effect was observed after fertilized turbot eggs with UV-irradiated P. olivaceus sperm and the optimal UV dose for gynogenetic haploid production was 36,000 erg mm(-2). At 15 degrees C, appropriate timing of cold shock for retention of the second polar body in turbot eggs was at 6 min after fertilization. Results of different combinations of two shock temperatures (1 or 3 degrees C) and four shock durations (15, 25, 35 or 45 min) at 6 min after fertilization demonstrated that shock of 25 min at 1 degrees C gave the highest production of diploid gynogens (39.58% relative to its diploid control). The results of this study reveal that the use of UV-irradiated P. olivaceus sperm for activation of turbot eggs and cold shock for polar body retention is an effective method to produce gynogenetic offspring.

Tank cultivation of the red alga Palmaria palmata: Year-round induction of tetrasporangia, tetraspore release in darkness and mass cultivation of vegetative thalli

Field-collected tetrasporophytes of Palmaria palmata were tumbled in 300-L outdoor tanks from January to August at ambient daylength or in a constant short-day (SD) regime (8 h light per day), both at 10 or 15 degrees C. Tetrasporangia were massively induced after 2.5 months under SD conditions at 10 degrees C and completely lacking at 15 degrees C, both under SD or ambient daylength conditions, with a few tetrasporangia present at 10 degrees C and ambient daylength. Elongation rates of tagged tetrasporophytic thalli peaked from March to April in all four conditions, when the biomass densities in the outdoor tanks were close to 2.5 kg fresh weight m(-2). Under all four conditions, juvenile proliferations started to appear in June from the margins of the old fronds, and attained approximately 1 cm in length by the end of July. Approximately 80% of the tetraspores were released during the first three dark phases in a light/dark regime, and the remaining 20% during the light phases. A minimum of 10 min darkness was observed to trigger spore release. White light inhibited tetraspore release, while a similar number of spores were released in continuous red light or in the light/dark regime, although with no significant differences of spore release during subjective days and nights. Sporelings were successfully derived from the released tetraspores for mass propagation of the male gametophyte in 2000-L outdoor tanks in a greenhouse. Mass production of male gametophytic sporelings of P. palmata was completed two times by SD induction of tetrasporangia at 10 degrees C, release of spores in darkness and culturing the sporelings until they were ready to be propagated vegetatively in greenhouse tanks. One experiment lasted from January to October 2001, with spore release in June, and the second from September to April 2003, with spore release in January. These results may support the development of sustainable, year-round Palmaria farming. (c) 2005 Elsevier B.V. All rights reserved.

Effective response of nonlinear composite under external AC and DC electric field

A perturbation method is used to study effective response of nonlinear Kerr composites, which are subject to the constitutive relation of electric displacement and electric field, D-alpha = epsilon(alpha)E + chi(alpha)vertical bar E vertical bar(2)E. Under the external AC and DC electric field E-app = E-a (1 + sinwt), the effective nonlinear responses and local potentials are induced by the cubic nonlinearity of Kerr materials at all harmonics. As an example in three dimensions, we have investigated this kind of nonlinear composites with spherical inclusions embedded in a host. At all harmonic frequencies, the potentials in inclusion and host regions are derived. Furthermore, the formulae of the effective linear and nonlinear responses are given in the dilute limit.

Controlling electric field distribution by graded spherical core-shell metamaterials

This paper investigates analytically the electric field distribution of graded spherical core-shell metamaterials, whose permittivity is given by the graded Drude model. Under the illumination of a uniform incident optical field, the obtained results show that the electrical field distribution in the shell region is controllable and the electric field peak's position inside the spherical shell can be confined in a desired position by varying the frequency of the optical field as well as the parameters of the graded dielectric profiles. It has also offered an intuitive explanation for controlling the local electric field by graded metamaterials.

Localization of the electric-field distribution in graded core-shell metamaterials

The local electric-field distribution has been investigated in a core-shell cylindrical metamaterial structure under the illumination of a uniform incident optical field. The structure consists of a homogeneous dielectric core, a shell of graded metal-dielectric metamaterial, embedded in a uniform matrix. In the quasistatic limit, the permittivity of the metamaterial is given by the graded Drude model. The local electric potentials and hence the electric fields have been derived exactly and analytically in terms of hypergeometric functions. Our results showed that the peak of the electric field inside the cylindrical shell can be confined in a desired position by varying the frequency of the optical field and the parameters of the graded profiles. Thus, by fabricating graded metamaterials, it is possible to control electric-field distribution spatially. We offer an intuitive explanation for the gradation-controlled electric-field distribution.

Effective dielectric response of nonlinear composites with external ac and dc electric field

The perturbation method is developed to investigate the effective nonlinear dielectric response of Kerr composites when the external ac and dc electric field is applied. Under the external ac and dc electric field E-app=E-a(1+sin omegat), the effective coupling nonlinear response can be induced by the cubic nonlinearity of Kerr nonlinear materials at the zero frequency, the finite basic frequency omega, the second and the third harmonics, 2omega and 3omega, and so on. As an example, we have investigated the cylindrical inclusions randomly embedded in a host and derived the formulas of the effective nonlinear dielectric response at harmonics in dilute limit. For a higher concentration of inclusions, we have proposed a nonlinear effective-medium approximation by introducing the general effective nonlinear response. With the relationships between the effective nonlinear response at harmonics and the general effective nonlinear response, we have derived a set of formulas of the effective nonlinear dielectric responses at harmonics for a larger volume fraction. (C) 2004 American Institute of Physics.

Higher order response of nonlinear composite in external AC electric field

The fifth-order effective nonlinear responses at fundament frequency and higher-order harmonics are given for nonlinear composites, which obey a current-field relation of the form J = sigmaE + x\E\(2) E, if a sinusoidal alternating current (AC) external field with finite frequency omega is applied. As two examples, we have investigated the cylinder and spherical inclusion embedded in a host and, for larger volume fraction, also derived the formulae of effective nonlinear responses at higher-order harmonics by the aid of the general effective response definition. Furthermore, the relationships between effective nonlinear responses at harmonics are given. (C) 2003 Elsevier Science B.V. All rights reserved.

Effective response of a non-linear composite in external AC electric field

A general effective response is proposed for nonlinear composite media, which obey a current field relation of the form J = sigmaE + chi\E\(2) E when an external alternating current (AC) electrical field is applied. For a sinusoidal applied field with finite frequency omega, the effective constitutive relation between the current density and electric field can be defined as, = sigma(e) + chi(e) <\E(x, omega, t)\(2) E(x, omega, t)> + (. . .), where sigma(e) and chi(e) are the general effective linear and nonlinear conductive responses, respectively. The angled brackets <(. . .)> denotes the ensemble average. As two examples, we have investigated the cylindrical and spherical inclusions embedded in a host and also derived the formulae of the general effective linear and nonlinear conductive responses in dilute limit. For higher volume fraction of inclusions, we have proposed a nonlinear effective medium approximation (EMA) method to estimate the general effective response of nonlinear composites in external AC field. Furthermore, the effective nonlinear responses at harmonics are predicted by using the general effective response. (C) 2002 Elsevier Science B.V. All rights reserved.