Artificially induced tetraploid masu salmon have the ability to form primordial germ cells

Diploid gametes generated with tetraploid animals are a stepping stone to improving chromosome manipulation techniques. However, artificially induced tetraploid individuals generally die soon after hatching. Diploid gametes could be induced by in vivo cultures of tetraploid primordial germ cells (PGCs) through germ-line chimera. In the present study, characteristics of PGCs were studied in inviable tetraploid masu salmon, Oncorhynchus masou. Histological observation of tetraploid embryos revealed that the same or smaller numbers of PGCs were observed and they migrate into the genital ridges as did diploid PGCs during gonadogenesis. By whole-mount in situ hybridization using vasa messenger RNA (mRNA), 4–35 vasa-positive signals were detected in a pair of genital ridges of tetraploids. By cytological observation of genital ridge cell suspensions, several large round cells were observed, some of which extended pseudopodia. They also contained large nuclei and round granules in their cytoplasm, characteristics of PGCs. As the results suggest that inviable artificial tetraploids have PGCs, we expect to achieve diploid gamete production through surrogate propagation and tetraploid fish production.     

Effect of calcium ion on the thermal denaturation of subfragment-1 and rod regions of squid myosin upon the heating of myofibrils

Thermal inactivation of Ca²⁺ ATPase of squid myofibrils was significantly suppressed in the presence of Ca²⁺. Monomeric myosin content decreased much faster than Ca²⁺ ATPase inactivation in Ca medium, which was well explained by fast rod denaturation. In contrast, rod denaturation was slower than S-1 in EDTA medium. The decrease in monomeric myosin content was explained by faster S-1 denaturation. Comparing the S-1 and rod denaturation rates at a fixed temperature, it was concluded that S-1 denaturation was suppressed by Ca²⁺ whereas the rod denaturation was not. An unfolding experiment with isolated myosin rod confirmed that there was no stabilizing effect of Ca²⁺ on myosin rod. It was concluded that significant stabilization of the S-1 portion by Ca²⁺ generated the apparently different myosin denaturation patterns in the two media.     

Growth and reproduction of the lion's paw scallop Nodipecten subnodosus in a suspended culture system at Guerrero Negro lagoon,Baja California Sur,Mexico

The lion's paw scallop, Nodipecten subnodosus (Sowerby) has considerable aquacultural potential due to its fast growth and large adductor muscle. Prior investigations throughout northwestern Mexico's littoral have reported highly variable growth rates; furthermore, no studies are available of the environment on growth and gametogenesis in this species under culture conditions. This investigation assesses the effect of food availability and temperature on the growth and gametogenesis of N. subnodosus in a suspended culture system at Guerrero Negro lagoon, Mexico. After 1 year of cultivation, N. subnodosus reached 69.13 mm in shell height (SH) (0.196 mm day^?1, 14 months old). Two significant growth spurts were observed: over the two first months of culture (August and September 2001, mean growth rate 0.4 mm day^?1) and in September 2002 (0.3 mm day^?1), both related to high temperatures and chlorophyll a concentrations. The onset of gametogenesis occurred in April 2002, with an increase in temperature (10‐month‐old scallops, 54.5 mm SH). The first spawning occurred in October and November (86.2 and 93 mm SH), with peak temperatures. These results, together with the analysis of previous reports, indicate that N. subnodosus has a higher preference for temperate areas; therefore, the Guerrero Negro lagoon appears to be a suitable site to culture this species.     

Nitrate removal efficiency and bacterial community of polycaprolactone-packed bioreactors treating water from a recirculating aquaculture system

A denitrification reactor packed with polycaprolactone (PCL) as a carbon source and biofilm carrier was developed to remove nitrate nitrogen (\( {\mathrm{NO}}_3^{-}-\mathrm{N} \)) from the water of a recirculating aquaculture system for 115 days. The hydraulic retention time was set to 6 h, and the water flow rate was 0.95 L h^?1. The removal rates of \( {\mathrm{NO}}_3^{-}-\mathrm{N} \) ranged from 34.67 to 155.7 g \( {\mathrm{NO}}_3^{-}-\mathrm{N} \) m^?3 day^?1 when the effluent \( {\mathrm{NO}}_3^{-}-\mathrm{N} \) concentrations ranged between 1.62 and 72.25 mg L^?1. No obvious changes in the Fourier transform infrared spectra of the PCL before and after use were observed. Bacterial community structure in the biofilm of the PCL granules was analyzed using Illumina MiSeq sequencing technology. Proteobacteria and Bacteroidetes were predominant in the biofilm, with relative abundances of 63.9 and 27.4%, respectively. Three genera, Acidovorax, Azospira, and Diaphorobacter, were capable of both denitrification and PCL degradation. This study indicates that PCL-packed reactors may be used and optimized for removing nitrate from aquaculture effluents.     

Plasma levels of immune factors and sex steroids in the male seahorse <Emphasis Type="Italic">Hippocampus erectus</Emphasis> during a breeding cycle

To better understand the endocrine- and immune-response pattern during reproduction in a fish species having parental care behaviors and also to accumulate the endocrine- and immune-related data for future explanations of the low reproductive efficiency in seahorse species, the variations of immune factors and sex steroids in the plasma of the male lined seahorse Hippocampus erectus at different breeding stages, i.e., pre-pregnancy, pregnancy (early, middle, and late periods), and post-pregnancy, were investigated in the present study. The immune factors included monocytes/leucocytes (M/L), leucocyte phagocytic rate (LPR), immunoglobulin M (Ig M), interleukin-2 (IL-2), interferon-α (IFN-α), and lysozyme (LZM). The sex steroids included testosterone (T), 11-ketotestosterone (11-KT), 11β-hydroxytestosterone (11β-OHT), 17α-methyltestosterone (17α-MT), 17β-estradiol (E2), and 17α-hydroxy-20β-dihydroprogesterone (17α-20β-P). Moreover, the immune metabolic activity of epithelium cells in the brood pouch at different breeding stages was also analyzed through ultrastructural observations of the abundance of cytoplasmic granules, mitochondria, endoplasmic reticulum, lysosomes, and exocytosis. The results show that a higher immune level was observed during pregnancy, particularly in the early and middle periods, and a lower immune level was noted during pre-pregnancy. Correspondingly, the epithelium cells in the brood pouch also showed a stronger immune metabolic activity during pregnancy and weaker activity during pre-pregnancy. Four sex steroids of T, 11β-OHT, 17α-MT, and E2 were higher during pre-pregnancy and lower during post-pregnancy, whereas 11-KT and 17α-20β-P, which were positively correlated with part immune factors, were higher during pregnancy. No negative correlations between sex steroids and immune factors were observed. In conclusion, the higher immune competence during pregnancy may indicate that parental care could improve immunity, which may be the major factor for no immunosuppressive effect of sex steroids during reproduction in the seahorse H. erectus, unlike noncaregiving fishes in which inhibitions of sex steroids on immunity are frequently observed. Moreover, higher 11-KT and 17α-20β-P during pregnancy than during pre-pregnancy and post-pregnancy may suggest that these two steroids are also involved in parental care regulation.     

Comparative analysis of using cereal grains and compound feed in semi-intensive common carp pond production

The semi-intensive system of carp farming is dominant in inland aquaculture. Although it appears to be simple, this system has a whole range of options, from those based on traditional rearing methods with use of plants from the region where the fish are reared to production based on the use of high-quality concentrated feeds. In this paper, we conduct a comparative analysis of the effect of using cereal grains as opposed to compound feed (pelleted and extruded) on the quantity of fish produced, flesh quality, histological changes in the digestive tract, water quality, and structure of the biocoenosis in the pond ecosystem. When the fish are fed cereal grains, production ranges from 500 to 1500 kg/ha, while using compound feed gives production that is twice as great. The proportions of protein and water are higher and that of lipids lower in flesh of common carp reared on compound feed in relation to fish fed cereal grains. Use of extruded feed gives better content of n-3 polyunsaturated fatty acids and a better n-3/n-6 ratio than when pelleted feed and cereal grains are used. Comparison of water quality in carp ponds under conditions of using various types of feed indicates that there are no significant differences. Although it was expected that feed with a higher percentage of proteins would cause disturbances in the aquatic ecosystem, their continual incorporation into the cycling of matter in the water contributes to maintenance of ecological equilibrium and even indirectly promotes growth of the common carp.     

Post-molt processes of cuticle formation and calcification in the Japanese mitten crab <Emphasis Type="Italic">Eriocheir japonicus</Emphasis>

This study examines the following in the Japanese mitten crab: (1) the structure of the exoskeleton with special reference to its calcification; (2) the progression of post-molt cuticle formation and calcification. In the crab, the structure and calcification state of the exoskeleton at the molt and during the inter-molt stage were similar to those of other crustaceans. During the inter-molt, the exoskeleton consisted of four cuticle layers; the outermost epicuticle, the exocuticle, the endocuticle and the innermost membrane layer. Intense calcification was observed in the exo- and endocuticle. At the molt, the synthesis of the epi- and exocuticle was already complete, and the addition of the endocuticle began after the molt. Calcification of the exocuticle initiated soon after the molt, but there was a delay between endocuticle matrix synthesis and calcification. Histology showed that the process of calcification was similar to that in other crustaceans. However, calcium concentrations within the exoskeleton continued to increase and never reached the levels of the inter-molt stage at the end of the experiment. This suggests that the Japanese mitten crab is relatively slow to calcify compared to other crustaceans.     

Relative potencies of natural estrogens on vitellogenin and choriogenin levels in the Indian freshwater spotted snakehead, <Emphasis Type="Italic">Channa punctata</Emphasis>: in vivo and in vitro studies

The relative efficacies of three natural estrogens viz., estrone (E₁), estradiol-17β (E₂) and estriol (E₃) to induce synthesis of vitellogenin (Vg) and choriogenin (Chg) were assessed in primary hepatocyte cultures of the Indian freshwater spotted snakehead, Channa punctata. Hepatocytes were isolated from the spotted snakehead liver by a non-enzymatic protocol. Optimum culture conditions were standardized for ensuring their viability and functioning. Isolated hepatocytes were cultured for 48 h for monolayer formation and then exposed to various concentrations (0.001–10 μM) of the three estrogens. Competitive homologous ELISAs, developed and validated for spotted snakehead Vg and Chg were employed to determine the amounts of these two proteins secreted into the culture medium after 48 h of incubation. The results reveal that although all the three estrogens were effective in inducing the production of Vg and Chg in a dose-dependent manner, there were differences in their relative potencies. Of three estrogens, E₁ was the least potent and could induce synthesis of Vg and Chg only at a minimum concentration of 0.5 μM; whereas significant levels of both the proteins were quantified in culture medium by exposing the hepatocytes to E₂ or E₃ even at a concentration of 0.001 μM. All three estrogens were effective in inducing synthesis of Vg and Chg in vivo also. These results suggest the possibility of employing the above in vitro experimental design to monitor the presence of estrogens/estrogen-like chemicals in natural waters, which could interfere with the estrogen receptor system of fish. This study further points to the possibility of using Chg, in addition to Vg, as a parameter for screening various chemicals for their estrogenic activity.     

Guanine-cytosine contents of the host and symbiont cDNA in a symbiotic coral

ABSTRACT:   Hermatypic (reef-building) corals harbor dinoflagellate endo-symbionts Symbiodinium spp. In studying gene expression in such symbiotic corals, problems arise regarding how to distinguish the coral and symbiont mRNA, and how to estimate their fractions in the mRNA population of the holobiont (symbiotic complex of the coral and Symbiodinium cells). In this study, these issues were addressed using juveniles of hermatypic coral Acropora tenuis in symbiosis with Symbiodinium cells of strain PL-TS-1. First, the guanine-cytosine (GC) contents were determined in expressed sequence tags (EST) from PL-TS-1 cells cultured in vitro and symbiont-free larvae of A. tenuis , and their average GC contents were found to be significantly different. The average GC content of the EST from the holobiont was much closer to that of A. tenuis larvae, suggesting that the majority (>90%) of mRNA isolated from the holobiont originated in the host. In protein-coding sequences, little overlap was observed between the GC-content distributions of PL-TS-1 cells and A. tenuis larvae. All of the coding sequences ( n  = 59) found in the A. tenuis EST had GC contents below 0.5, whereas the GC content exceeded 0.5 in the majority (43/44) of coding sequences from the nuclear genome of PL-TS-1 cells.