Akihiro Kijima

Inheritance of Microsatellite DNA Markers in the Pacific Abalone Haliotis discus hannai

Microsatellite markers have been developed for a variety of abalones, and locus-specific homozygote excesses at population level have been recorded for microsatellite loci. To ascertain whether null alleles exist at microsatellite loci in the Pacific abalone, we studied the mode of inheritance of 7 microsatellite loci in 4 families with a reciprocal cross of 2 females × 2 males. All loci segregated codominantly, but only 3 loci (Hdh1321, Hdh78, and Hdd108C) conformed to Mendelian segregation and can be used for parental analysis and population genetic studies. When null alleles were considered, 2 loci (Hdh1761 and Hdh1457) confirmed Mendelian expectations in all families, while the remaining 2 loci (Hdd114B and Hdd229) showed deviation from Mendelian segregation in at least one family even though null alleles were considered. These results indicated the need to test the inheritance pattern for microsatellite markers in abalones before using them for population genetic or parentage analysis.

Microsatellite Analysis of Japanese Sea Cucumber, Stichopus (Apostichopus) japonicus, Supports Reproductive Isolation in Color Variants

The genetic relationship among the three color variants (Red, Green, and Black) of the Japanese sea cucumber, S. japonicus, was investigated using 11 microsatellite markers. Genetic differentiation testing among the three sympatric color types showed the strong heterogeneity of Red (p < 0.001), while no significant difference was observed between Green and Black (p = 0.301 to 0.961). UPGMA trees constructed from 10 sample lots from 5 localities showed two distinct clusters, one from the Red types and the other from the Green and Black types. In addition, the sympatric Green and Black formed one subcluster with strong bootstrap support at each locality. These results indicate the separate species status of Red and the other color types, and also support the population identity of sympatric Green and Black.

Permanent Genetic Resources added to Molecular Ecology Resources Database 1 June 2010 - 31 July 2010.

This article documents the addition of 205 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Bagassa guianensis, Bulweria bulwerii, Camelus bactrianus, Chaenogobius annularis, Creontiades dilutus, Diachasmimorpha tryoni, Dioscorea alata, Euhrychiopsis lecontei, Gmelina arborea, Haliotis discus hannai, Hirtella physophora, Melanaphis sacchari, Munida isos, Thaumastocoris peregrinus and Tuberolachnus salignus. These loci were cross‐tested on the following species: Halobaena caerulea, Procellaria aequinoctialis, Oceanodroma monteiroi, Camelus ferus, Creontiades pacificus, Dioscorea rotundata, Dioscorea praehensilis, Dioscorea abyssinica, Dioscorea nummularia, Dioscorea transversa, Dioscorea esculenta, Dioscorea pentaphylla, Dioscorea trifida, Hirtella bicornis, Hirtella glandulosa, Licania alba, Licania canescens, Licania membranaceae, Couepia guianensis and 7 undescribed Thaumastocoris species.

Isolation and Characterization of Twenty Microsatellite Loci in Japanese Sea Cucumber (Stichopus japonicus)

Twenty microsatellite markers were first developed from the Japanese sea cucumber Stichopus japonicus using an enrichment protocol. Of the 20 microsatellite loci, 19 loci were polymorphic in the population examined. At these polymorphic loci, the number of alleles per locus varied from 2 to 15, and the observed heterozygosities ranged from 0.03 to 0.97, which is considerably higher than those previously found for allozymes. The high variability of the microsatellite markers identified in this study will make them excellent tools for genetic analyses of S. japonicus.

Color, growth and maturation in ploidy-manipulated fancy carp

Ploidy manipulation was used to examine the effects of triploidizatin and gynogenetic diploidization in fancy carp, a race of Cyprinus carpio. Ultraviolet dosages of at least 9000 erg/mm2 were required to inactivates sperm genetically. An interval of 10–12 min before the start of 60-min cold treatments was required to retain the second polar body in fertilized eggs. At optimum conditions, survival rates of gynogenetic diploids were 80% to the eyed embryo stage and 25% to hatching; corresponding values in triploids were 73% and 32%, respectively. The highest success rates in inducing gynogenetic diploids and triploids were 100% and 68.9%, respectively. Triploids with the Japanese strain as the female and European strain as the male parent grew slower than control diploids when they were reared in the same pond for 20 months. However, triploids using the Japanese strain as both parents grew larger in 7 months than control diploids. Triploids at 20 months of age had less developed gonads and more fat around the digestive tract than diploid fish. Male-specific color spots were smaller in triploids than in control diploids. The typical red and white fancy carp colors were found in the gynogenetic diploids in almost the same frequency as in the control diploids. Recombination between gene and centromere was observed at the Gpi-2 locus in gynogenetic diploids.

Effects of ultraviolet irradiation on genetical inactivation and morphological structure of sperm of the Japanese scallop, Patinopecten yessoensis

Abstract Effects of ultraviolet (UV) irradiation on genetic inactivation and morphological structure of sperms were examined in the scallop, Patinopecten yessoensis . Haploid gynogenesis of the scallop was successfully induced by 50–60 s UV irradiation of 720 μW cm −2 s −1 . The fertilization rate apparently decreased with increasing irradiation time, and the development of the eggs fertilized with the genetically inactivated sperms terminated before reaching the D-shaped larvae stage. Scanning electron microscopy (SEM) showed clear destruction of the sperm acrosome and flagellum in the UV-irradiated sperms. As the duration of UV irradiation increased, the acrosome of sperms tended to suffer greater damage, until the sperms eventually lost their flagella. Abnormalities in these structures have appeared to account, at least in part, for the decline of the fertilization rate of eggs inseminated with UV-irradiated sperms.

Segregation of Microsatellite Alleles in Gynogenetic Diploid Pacific Abalone ( Haliotis discus hannai )

Inheritance of 9 microsatellite loci was examined in 3 families of gynogenetic Pacific abalone Haliotis discus hannai produced by fertilizing eggs with UV-irradiated sperm followed by inhibition of the second meiotic division. The proportion of heterozygous progeny was used to estimate marker-centromere (M-C) distances. All loci conformed to Mendelian segregation in the control crosses when null alleles were accounted for. The absence of paternal alleles confirmed the gynogenetic origin of the offspring and indicated 100% success for 3 families. Estimated recombinant frequencies ranged from 0.10 to 0.60, which is lower than those observed in other gynogenetic diploid animals. The mean recombination frequency was 0.22, corresponding to a fixation index of 0.78 in one generation. This is 3.12 times the increase in homozygosity expected after one generation of sib mating (0.25), suggesting meiotic gynogenesis may be an effective means of rapid inbreeding in the abalone. M-C map distances for the 9 loci varied between 5 and 30 cM under the assumption of complete interference. The information about M-C distances will be useful for future gene mapping in H. discus hannai.

Inbreeding depression traits in pacific abalone Haliotis discus hannai by factorial mating experiments

Abstract‘Inbreeding depression’ may be an avoidable phenomenon for abalone culture. However, only a few studies have been carried out on inbreeding depression. In the present study, using six families produced in 1994, a factorial mating system including inbreeding and outbreeding was constructed in order to demonstrate inbreeding depression traits of the Pacific abalone. In total, 24 inbreeding and 21 outbreeding crosses were produced during three years (1999–2001) and these off-spring were reared for approximately one year. Significant differences in fertilization rate and growth were not observed between inbreeding and outbreeding corsses. However, the deformity rate of veliger larvae was always higher in inbreeding crosses than that of outbreeding crosses in all experiments. Moreover, a significantly high deformity rate was observed in some full-sib families of inbreeding. Alternatively, the survival rates of inbreeding crosses were much lower than for outbreeding crosses after about 4 months and one year in two rearing localities. These results indicate that inbreeding depression is observed in the traits of deformity rate and survival, but not in fertilization rate nor growth in the first generation of a full-sib family of the Pacific abalone.

Quantitative analysis of pattern of gonial proliferation during sexual maturation in Japanese scallop Patinopecten yessoensis

This study was undertaken to describe and quantitatively analyze the pattern of development of gametes in the Japanese scallop Patinopecten yessoensis. Incorporation of 5-bromo-2′-deoxyuridine (BrdU) into gonial cells was used to quantitatively detect mitotically active gonial cells. Oogonia increased in number from November to December and decreased rapidly to March. A small number of oocytes was detected in November. Oocytes steadily increased in number and size up to March. The number of spermatogonia slightly increased from November to December, and increased markedly from January to March. Both ratios of BrdU-immunopositive gonial cells in the ovary and testis to gonial cells moderately increased from September to December. The ratio of BrdU-immunopositive spermatogonia to gonial cells drastically increased from January to February and kept an elevated level in March, whereas the oogonia started to disappear in January. The results suggest that the pattern of proliferation of gonial cells can be divided into two phases: (i) phase I, oogonia and spermatogonia slowly proliferate through the growing stage; and (ii) phase II, oogonia develop into oocytes and spermatogonia begin to proliferate rapidly through the mature and spawning stages. The proliferation of gonial cells is likely under different endocrine controls in phases I and II.

Genetic divergence and relationship among fifteen species of genera Trachurus, Decapterus, Selar and Selaroides

Genetic distance and the relationships among 15 species of generaTrachurus, Decapterus,Selar, andSelaroides were estimated from 18 electrophoretically detectable isozyme genes. Estimates of genetic distance (D) between every pair of species within the genusTrachurus ranged from 0.005 to 0.560 with a mean of 0.322, and from 0.484 to 1.868 with a mean of 1.022 within the genusDecapterus. Between species of different genera, estimates of D ranged from 0.786 to 2.863 with a mean of 1.784. From these results,Decapterus species could be considered as having evolved over a long period whileTrachurus is a newly arisen genus. A relationship among species suggests that theDecapterus species are expanded to offshore and deep area after being divided into some groups, and that theTrachurus species are divided presumably into at least two groups, one group of which is coastal and the other of which is offshore.Trachurus japonicus andTrachurus novaezelandiae could be considered subspecies on the basis of allelic distribution and genetic distance.