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Study on heritability of growth in the juvenile sea urchin Strongylocentrotus nudus.



ABSTRACT The heritability heritability /her·i·ta·bil·i·ty/ (her?i-tah-bil´i-te) the quality of being heritable; a measure of the extent to which a phenotype is influenced by the genotype.

her·i·ta·bil·i·ty
n.
1.
 of growth of juvenile Strongylocentrotus nudus was analyzed using quantitative genetic methods. Twenty-one half-sib groups and 60 to 63 full-sib groups of juveniles were obtained by artificial fertilization of three to five females by single males based on a nested design. The body weight (g) and test diameter (cm) of the young was measured 3 and 5 months after metamorphosis metamorphosis (mĕt'əmôr`fəsĭs) [Gr.,=transformation], in zoology, term used to describe a form of development from egg to adult in which there is a series of distinct stages. . Maternal component estimates are significantly greater than paternal component estimates for both weight and diameter at both ages. Greater maternal components suggest large non-additive genetic effects that could not be differentiated with the available data. Estimates of heritability in the narrow sense calculated from the additive genetic component using a paternal half-sib correlation analysis ranged from 0.2167-0.4565 for weight and 0.2059-0.4998 for diameter. The results indicate significant maternal effects. The strength of the nested design and the paternal half-sib correlation analysis used in this study make the estimate the most precise and unbiased reported to date.

KEY WORDS: sea urchin sea urchin, spherical-shaped echinoderm with movable spines covering the body. The body wall is a firm, globose shell, or test, made of fused skeletal plates and marked by regularly arranged tubercles to which the movable spines are attached. . Strongylocentrotus nudus, growth, heritability

INTRODUCTION

Sea urchins are one of the most important aquaculture aquaculture, the raising and harvesting of fresh- and saltwater plants and animals. The most economically important form of aquaculture is fish farming, an industry that accounts for an ever increasing share of world fisheries production.  species in the world. The gonads have long been used as a luxury food and as a food source by common people in many countries (Hobson & Chave 1990, Shimabukuro 1991, Hagen 1996). Because of over-fishing, interest in aquaculture of sea urchins has increased greatly (Hagen 1998, Lawrence et al. 2001). One of the most important species for aquaculture is Strongylocentrotus nudus (Hagen 1996, Agatsuma 1998). Current culture of S. nudus has used seeds obtained from wild individuals (Gao & Chang 1999, Liao & Qiu, 1999). Analysis of populations of S. nudus in Japanese waters shows considerable range in size of small individuals, presumably pre·sum·a·ble  
adj.
That can be presumed or taken for granted; reasonable as a supposition: presumable causes of the disaster.
 of single cohorts (Agatsuma 1997). This could result from inter action of genetic characteristics and the environment. Vadas et al. (2002) found evidence for intrinsic variability in field populations of Strongylocentrotus droebachiensis. It is important to document the degree of heritability of growth in sea urchins because of its implications for both fisheries and aquaculture.

Demonstration of heritability is best done with comparisons of half-sib groups because they are less likely to be affected by environmental influence (Gjedrem 1992). Sib analysis techniques have been used for several important aquaculture species (Mallet mallet,
n a hammering instrument.

mallet, hard,
n a small hammer with a leather-, rubber-, fiber-, or metal-faced head; used to supply force or to supplement hand force for the compaction of foil or amalgam and to seat cast
 et al. 1986, Rawson & Hilbish 1990, Hadley et al. 1991, Crenshaw cren·shaw   also cran·shaw
n.
A variety of winter melon (Cucumis melo var. inodorus) having a greenish-yellow rind and sweet, usually salmon-pink flesh.



[Origin unknown.]
 et al. 1991, Newkirk et al. 1977, Benzie et al. 1997). The purpose of this study is to estimate heritability of growth in terms of body weight and diameter of juvenile Strongylocentrotus nudus.

MATERIALS AND METHODS

Experimental Design

This study used a classic nested mating design developed by Comstock and Robinson (1952) to partition the phenotypic variation in juvenile growth into its genetic and non-genetic causes. In this experiment each of 21 male Strongylocentrotus nudus was mated to 3 to 5 females, therefore generating 63 full-sib families and 21 half-sib families. The effects of males and females nested within males on growth were separated using nested analysis of variance (ANOVA anova

see analysis of variance.

ANOVA Analysis of variance, see there
). Juveniles were weighed and their diameters measured at 3 and 5 months of age.

Genetic Analysis

The covariance Covariance

A measure of the degree to which returns on two risky assets move in tandem. A positive covariance means that asset returns move together. A negative covariance means returns vary inversely.
 among full- and half-sibs provides the basis for the separation of phenotypic variance into genetic and environmental components of variance. The covariance among full- and half-sibs are calculated from the observed components of variance obtained from a three-level nested, unbalanced ANOVA (Table 1) and the General Linear Models procedure of the statistical analysis system (SAS (1) (SAS Institute Inc., Cary, NC, www.sas.com) A software company that specializes in data warehousing and decision support software based on the SAS System. Founded in 1976, SAS is one of the world's largest privately held software companies. See SAS System. ) (Freund et al. 1986).

The experiment was a three-level classic nested, unbalanced design. Therefore the number of offspring in dams and in sires and in dams within sires should revise ("revise" means adjust). The effective means were computed using the equations:

Effective mean number of offspring in dams within sires

[K.sub.1] = [N - [summation summation n. the final argument of an attorney at the close of a trial in which he/she attempts to convince the judge and/or jury of the virtues of the client's case. (See: closing argument)  of]([n.sub.ij.sup.2]/[dn.sub.i])]/(D - S)

Effective mean number of offspring in dams:

[K.sub.2] = [[summation of]([n.sub.ij.sup.2]/[dn.sub.i]) - [summation of] ([n.sub.ij.sup.2]/N)]/(S - 1)

Effective mean number of offspring in sires:

[K.sub.3] = (N - [summation of][dn.sup.2.sub.i]/N)/(S - 1)

in which S = number of sires, D = number of dams, [n.sub.ij] = number of offspring of the i-th sire and j-th dam, [dn.sub.1] = number of offspring of i-th sire, N = sum of number of offspring of all sires or all dams.

The phenotypic variance ([V.sub.P]) was separated into the additive genetic variance ([V.sub.A]), non-additive genetic variance ([V.sub.N] and environmental variance ([V.sub.E]), and the environmental variance ([V.sub.E]) was separated into the common environmental variance ([V.sub.E]) and the specific environmental variance ([V.sub.ES) using the standard separation of variance components (Falconer Falconer

prison where former professor Farragut, who had killed his brother, witnesses the torments and chaos of the penal system. [Am. Lit.: Cheever Falconer in Weiss, 151]

See : Imprisonment
 1989). The causal components of variance were estimated from the full- and half-sib covariance using the relationships in Table 2.

Heritabilities were computed using the relationships:

[h.sup.2] = [V.sub.A]/[[V.sub.A] + [V.sub.NA] + [V.sub.E]]

Thus heritabilites in the narrow sense of paternal half-sib and maternal half-sib and full-sib were computed using the respective relationships:

[h.sup.2.sub.HS(S)] = 4 x [[sigma].sup.2.sub.S]/([[sigma].sup.2.sub.s] [[sigma].sup.2.sub.D] + [[sigma].sup.2])

[h.sup.2.sub.HS(D)] = 4 x [[sigma].sup.2.sub.D]/([[sigma].sup.2.sub.s] [[sigma].sup.2.sub.D] + [[sigma].sup.2])

[h.sup.2.sub.FS(D/S D/S Downstream
D/S Duty Station
D/S Duration of Status (immigration)
D/S Dominance and Submission
D/S Downsize
D/S Design Standard
D/S Dynamic/Static
D/S Digital to Synchro
)] = 2 x ([[sigma].sup.2.sub.S] + [[sigma].sup.2.sub.D]) /([[sigma].sup.2.sub.S] + [[sigma].sup.2.sub.D] + [[sigma].sup.2]

Test of significant of heritability:

t = [h.sup.2]/[[sigma].sub.h.sup.2]

Paternal half-sib:

[MATHEMATICAL EXPRESSION A group of characters or symbols representing a quantity or an operation. See arithmetic expression.  NOT REPRODUCIBLE IN ASCII ASCII or American Standard Code for Information Interchange, a set of codes used to represent letters, numbers, a few symbols, and control characters. Originally designed for teletype operations, it has found wide application in computers. .]

Maternal half-sib:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII.]

Full-sib:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII.]

Experimental Animal

Collection and Maintenance

Parental Strongylocentrotus nudus were taken from a cultured population in Dalian Bay Dalian Bay (also spelled Talien Bay) is a roughly rectangular arm of the Korea Bay, oriented long side parallel to the land due south-east of the modern port city of Dalian, and serving as the roadstead for the harbor.  on the northern coast of the Yellow Sea on 10 September 2001. These individuals were held at 18-22[degrees]C under 500 x 1 illumination and fed Laminaria japonica Laminaria japonica,
n See kelp.
 ad libitum ad libitum

without restraint.


ad libitum feeding
food available at all times with the quantity and frequency of consumption being the free choice of the animal.
 for 32 days before spawning on 12 October 2001.

Fertilization

Individuals were removed from the aquaria a·quar·i·a  
n.
A plural of aquarium.
 and allowed to drain for 30 minutes before 1 mL 0.5 M KCL KCL - Kyoto Common Lisp  was injected into the coelomic cavity via the peristomial per·i·stome  
n.
1. Botany A fringe of toothlike appendages surrounding the mouth of a moss capsule.

2. Zoology The area or parts around the mouth in certain invertebrates.
 membrane. They were placed on the tops of flasks filled with sea water and the eggs and sperm collected from each individual for 30-60 minutes.

The eggs of each female were fertilized fer·til·ize  
v. fer·til·ized, fer·til·iz·ing, fer·til·iz·es

v.tr.
1. To cause the fertilization of (an ovum, for example).

2.
 with sperm from a single male. Approximately 15,000 eggs from each female were placed in 100-L containers. Sperm were diluted 1000-fold (Uehara et al. 1990) and a small amount of the diluted sperm was added to the eggs. Fertilization success was examined microscopically. The fertilized eggs were washed two to three times to remove excess sperm. The embryos were layered on the bottom of flasks and transferred into a 50-L container to develop at 17-21[degrees]C at a density of four to five individuals/mL. Normal plutei developed in 30-35 h. (Rahman et al. 2000, Rahman et al. 2001).

Rearing

The larvae Larvae, in Roman religion
Larvae: see lemures.
 were transferred to 100-L containers of filtered seawater seawater

Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine.
 at 16[degrees]C. Densities of larvae from the 2-arm to the 8-arm stage were maintained at one to two individuals/mL. The water was changed twice daily. The larvae were fed Chaetoceros gracilis, Light was maintained at <300 LX. A small amount of air was babbled into the water, After 3 months the juveniles from each fertilization group were placed separately into plastic cages suspended in a large pool. The juveniles were fed fresh Laminara japonica japonica (jəpŏn`əkə): see quince; camellia. . The cages were changed every 2 months. The juveniles were weighed and their diameter measured at ages of 3 and 5 months.

RESULTS

Growth--Increase in Body-weight and Test Diameter

Mean and standard deviation In statistics, the average amount a number varies from the average number in a series of numbers.

(statistics) standard deviation - (SD) A measure of the range of values in a set of numbers.
 of the increase in body weight and test diameter of offspring at 3 and 5 months of age are given in Table 3.

Analysis of Variance of Body Weight and Test Diameter of Offspring

Analysis of variance demonstrated great differences in body weight and diameter of juveniles from different females mated with the same male and between males at both 3 and 5 months of age (Table 4).

Effective mean number of offspring for sires and clams after 3 months was computed as follows: effective mean number of offspring in darns within sire is [K.sub.1] = 34.689, in dams is [K.sub.2] = 38.821, and in sires is [K.sub.3] = 107.719 Effective mean number of offspring for sires and dams after 5 months was computed as follows: [K.sub.1] = 33.505: [K.sub.2] = 36.831; [K.sub.3] = 109.268.

The causal components of variance were estimated from the full- and half-sib covariance using the relationships in Table 5.

Estimations of Heritability of Body Weight and Test Diameter of Offspring

Heritabilities in the narrow sense of paternal half-sib and maternal half-sib and full-sib of body weight and diameter of 3-month-old Strongylocentrotus nudus were calculated on the result of component of variance and test (t = [h.sub.2]/[[sigma].sub.h.sup.2) of significant of heritability respectively as Table 6.

All of the heritability in the narrow sense of sire half-sib and the heritability in the broad sense of dam full-sib of body weight, test diameter of S. intermedius were significantly different from zero (t-test, P < 0.01).

Estimated heritability was somewhat different among the sire heritability, dam heritability, and the pooled (combined) heritability for all three traits. The estimates of dam heritability were higher than that of sire heritability, and the pooled (combined) heritability was moderate.

DISCUSSION

Predicted heritabilities of larval larval

1. pertaining to larvae.

2. larvate.


larval migrans
see cutaneous and visceral larva migrans.
 growth have been reported for full-sib correlation analysis for Crassostrea virginiica (Lannan 1972, Haley et al, 1975, Newkirdk et al. 1977) and Penaeus vannamei (Carr et al. 1997) and half-sib correlation analysis for Mercenaria mercenaria (Rawson & Hilbish 1990), Macrobrachium rosenbergii (Malecha et al. 1984), Penaeus vannamei (Carr et al. 1997, Benzie et al. 1996), and Penaeus stylirostri (Benzie et al. 1996). Predicted heritabilities of shell traits in wild littorina saxatilis populations have been reported for full-sib correlation analysis and offspring mother regression (Carballo et al. 2001). Estimates of heritabilities in the narrow sense generally ranged from 0.2-0.7. Realized heritability for increase in rate of growth in northern quahog quahog: see clam.
quahog

Thick-shelled edible clam of the U.S. The northern quahog (Mercenaria mercenaria), also known as the cherrystone, littleneck, or hard-shell clam, is 3–5 in. (8–13 cm) long.
 and Argopecten irradians concetricus (Crenshaw et al. 1996, Crenshaw et al. 1991) and realized heritability estimates for growth in the Chilean oyster Ostrea chilensis (Toro Toro may refer to:
  • Denominación de Origen Toro, the Spanish wine region
  • Toró, the nickname of Rafael Ferreira Francisco, Brazilian football (soccer) player
 et al. 1995). In our study, the estimates of heritabilities in the narrow sense for body weight at 3-5 months of age ranged from 0.217-0.457, consistent with those reported for other species. However, estimates are based on full-sib families bias heritabilities upwards when dominance and maternal effects are present (Lester, 1988). Because of the nested design and a paternal half-sib correlation analysis used, the estimate reported here is more precise and unbiased. This is the first report of heritability in the narrow sense reported for sea urchins.

An animal model includes a random effect for the additive genetic effect of each individual; and incorporates a complete set of additive genetic relationships among all individuals; and allows an unbiased estimation of variance components, even for the data involving selection and non-random mating (Gall & Bakar 2002, Sorensen & Kennedy 1986, Su et al. 1997). In this investigation full-sib family was taken as a random effect in a simple random model to account for the covariance among full-sibs caused by common environmental, dam and non-additive genetic effects, and half-sib family was used to account for covariance among half sibs caused by common environmental, dam, sire, and non-additive genetic effects. The results from the analyses based on this model were expected to be unbiased estimates of genetic parameters for the base population.

The much larger heritabilities computed from the female additive genetic component indicate the female genetic component still contain common environmental effects, maternal effects or non-additive genetic variance in the body weight or diameter. Dam effects are omnipresent om·ni·pres·ent  
adj.
Present everywhere simultaneously.



[Medieval Latin omnipres
 in the study. The fact that the juvenile phase may indicate that the quality of yolk yolk (yok) the stored nutrient of an oocyte or ovum.

yolk
n.
The portion of the egg of an animal that consists of protein and fat from which the early embryo gets its main nourishment and of
 reserves plays a role in early development. Dam effects may persist after the onset of exogenous Exogenous

Describes facts outside the control of the firm. Converse of endogenous.
 feeding. Crandell and Gall (1993) reported that dam The That Dam is a large stupa in Vientiane, Laos. Many Laotians believe it is inhabited by a seven headed dragon who tried to protect them from the armies of Siam, who invaded in 1827. It is also known as the Black Stupa, the English translation of the Lao name That Dam.  effects persist up to 2 years in rainbow trout rainbow trout

Species (Oncorhynchus mykiss) of fish in the salmon family (Salmonidae) noted for spectacular leaps and hard fighting when hooked. It has been introduced from western North America to many other countries.
 and up to 18-month-old Arctic char arctic char also Arctic char
n.
A char (Salvelinus alpinus) native to the fresh waters of Alaska and northern Canada.

Noun 1.
 (Nilsson 1994).

The estimated heritability indicates significant additive genetic variation for body weight and test size all over the sampling periods. Sire heritability for the different variables were lower than dam heritability in many cases. However, all heritabilities in the narrow sense of body weight, test diameter of S. intermedius were significantly different from zero (P < 0.01). The heritabilities in the narrow sense estimate obtained from this experiment indicate there is sufficient variation in the base population of sea urchins to respond to natural or artificial selection on juvenile growth weight. This justifies selection of juveniles based on growth characteristics for cultured brood stock.
TABLE 1.
Analysis of variance for components of phenotypic variation.

    Source of          Degree of         Sum of
    Variance         Freedom (df)     Squares (SS)

Dams                F x M - 1         S[S.sub.M]
Sires               F - 1             S[S.sub.F]
Dams/sires          F x (M - 1)       S[S.sub.M(F)]
Offspring (error)   F x M x (n - 1)   SS

Total               N - 1             S[S.sub.T]

    Source of        Mean Square        Expected Mean
    Variance            (MS)            Square E (MS)

Dams
Sires               M[S.sub.F]      [[sigma].sup.2] +
                                      [k.sub.2] [[sigma].
                                      sup.2.sub.M] + [k.
                                      sub.3] + [[sigma].
                                      sup.2.sub.F]
Dams/sires          M[S.sub.M(F)]   [[sigma].sup.2] +
                                      [k.sub.1] [[sigma].
                                      sup.2.sub.F]
Offspring (error)   MS              [[sigma].sup.2]

Total

TABLE 2.
Relationships between the covariance of full and half-sibs and
causal components of phenotypic variance.

      Component of                  Covariance
        Variance                    Components

[[sigma].sup.2.sub.F]       CO[V.sub.HS]
[[sigma].sup.2.sub.M]       CO[V.sub.FS] - CO[V.sub.HS]
[[sigma].sup.2.sub.E]       [V.sub.P] - CO[V.sub.FS]
[[sigma].sup.2.sub.T] =     [V.sub.P]
  [[sigma].sup.2.sub.F] +
  [[sigma].sup.2.sub.M] +
  [[sigma].sup.2]
[[sigma].sup.2.sub.F] +     CO[V.sub.FS]
  [[sigma].sup.2.sub.M]

      Component of                           Causal
        Variance                           Components

[[sigma].sup.2.sub.F]       1/4 [V.sub.A]
[[sigma].sup.2.sub.M]       1/4[V.sub.A] + 1/4[V.sub.NA] + [V.sub.EC]
[[sigma].sup.2.sub.E]       1/2 [V.sub.A] + 3/4[V.sub.D] + [V.sub.ES]
[[sigma].sup.2.sub.T] =     [V.sub.A] + [V.sub.NA] + [V.sub.EC] +
  [[sigma].sup.2.sub.F] +     [V.sub.ES]
  [[sigma].sup.2.sub.M] +
  [[sigma].sup.2]
[[sigma].sup.2.sub.F] +     1/2 [V.sub.A] + 1/4[V.sub.D] + [V.sub.EC]
  [[sigma].sup.2.sub.M]

      Component of                        Calculation of
        Variance                      Component of Variance

[[sigma].sup.2.sub.F]       {M[S.sub.F]- [(M[S.sub.M(F)] - M[S.sub.E])
                              /[k.sub.1] x [k.sub.2] - M[S.sub.E]}
                              /[k.sub.3]
[[sigma].sup.2.sub.M]       (M[S.sub.M(F)] - M[S.sub.E])/[k.sub.1]
[[sigma].sup.2.sub.E]       M[S.sub.E]
[[sigma].sup.2.sub.T] =
  [[sigma].sup.2.sub.F] +
  [[sigma].sup.2.sub.M] +
  [[sigma].sup.2]
[[sigma].sup.2.sub.F] +
  [[sigma].sup.2.sub.M]

TABLE 3.
Body weight and test diameter of offspring at 3 and 5 months of age.

             Body Weight (g)       Test Diameter (mm)

 Growth               Standard    Standard
 Phase     Average    Deviation   Average    Deviation

3 months   0.014484    0.0103      2.916       0.945
5 months   1.366       0.377       8.492       2.841

TABLE 4.
Analysis of variance for components of phenotypic variation
of Strongylocentrotus nudus at 3 and 5 months of age.

                              Body Weight

   Source of       Degrees of        Mean
   Variance       Freedom (df)    Square (MS)     F-Value

3 months
  Dam                   62       4.08340 x        9.893 **
                                   [10.sup.-3]
  Sire                  20       7.26634 x       17.605 **
                                   [10.sup.-3]
  Dams within           42       2.56772 x        6.221 **
    sires                          [10.sup.-3]
  Full-sibs           2210       4.12753 x
    within dams                    [10.sup.-4]
  Total               2272
5 months
  Dams                  59          0.79976       7.580 **
  Sire                  20          1.31728      12.485 **
  Dams within           39          0.53436       5.065 **
    sires
  Full-sibs           2045          0.10551
    within dams
  Total               2104

  Body Weight                   Test Diameter

   Source of         Mean                       Expected Mean
   Variance       Square (MS)    F-Value        Square E (MS)

3 months
  Dam               6.01406      6.737 **
  Sire             10.71717     12.006 **   [[sigma].sup.2] +
                                              [k.sub.2] [[sigma].
                                              sup.2.sub.M] +
                                              [k.sub.3][[sigma].
                                              sup.2.sub.M]
  Dams within       3.77449      4.228 **   [[sigma].sup.2] +
    sires                                     [k.sub.1] [[sigma.
                                              sup.2.sub.M]
  Full-sibs         0.89266                 [[sigma].sup.2]
    within dams
  Total
5 months
  Dams              69.16935     8.570 **
  Sire             108.2978     13.418 **   [[sigma].sup.2] +
                                              [k.sub.2] [[sigma].
                                              sup.2.sub.M] +
                                              [k.sub.3][[sigma].
                                              sup.2.sub.F]
  Dams within       49.10348     6.084 **   [[sigma].sup.2] +
    sires                                     [k.sub.1] [[sigma.
                                              sup.2.sub.M]
  Full-sibs          8.07108                [[sigma].sup.2]
    within dams
  Total

** P < 0.01; S = sires; D = dams; [K.sub.1] is the weighed mean
offspring number of females, [K.sub.2] = is the weighed offspring
number of females within sire, [K.sub.3] is the weighed mean
offspring number of sires.

TABLE 5.
Relationships between the covariance of full and half-sibs and causal
components of phenotypic variance.

Component of                   Causal        Covariance
Variance                     Components      Components

[[sigma].sup.2.sub.F]     1/4 [V.sub.A]      [Cov.sub.HS]
[[sigma].sup.2.sub.M]     l/4[V.sub.A] +     [Cov.sub.FS]
                            1/4 [V.sub.NA]     - [Cov.sub
                            + [V.sup.EC]       .HS]
[[sigma].sup.2]           1/2[V.sub.A]       [V.sub.P] -
                            + 3/4[V.sub.D]     [Cov.sub.
                            + [V.sub.EW]       FS]
[[sigma].sup.2.sub.P] =   [V.sub.A] +        [V.sub.P]
  [[sigma].sup.2.sub.F]     [V.sub.NA] +
  [[sigma].sup.2.sub.M]     + [V.sub.EC]
  [[sigma].sup.2]           + [V.sub.EW]
[[sigma].sup.2.sub.F] +   1/2[V.sub.A]       CO[V.sub.FS]
  [[sigma].sup.2.sub.M]     + 1/4[V.sub.D]
                            + [V.sub.EC]

                               Result of Component of Variance

                                   3 Month               5 Month

Component of                                Test      Body       Test
Variance                   Body Weight    Diameter   Weight    Diameter

[[sigma].sup.2.sub.F]     4.13895 x       0.06027    0.00678   0.50447
                            [10.sup.-5]
[[sigma].sup.2.sub.M]     6.16974 x       0.08308    0.01280   1.22465
                            [10.sup.-5]
[[sigma].sup.2]           4.275 x         0.89264    0.10551   8.07108
                            [10.sup.-4]
[[sigma].sup.2.sub.P] =   5.40587 x       1.03598    0.12509   9.80020
  [[sigma].sup.2.sub.F]     [10.sup.-4]
  [[sigma].sup.2.sub.M]
  [[sigma].sup.2]
[[sigma].sup.2.sub.F] +   1.03087 x       0.14335    0.01958   1.72912
  [[sigma].sup.2.sub.M]     [10.sup.-4]

TABLE 6.
Heritabilitics in narrow sense ([h.sup.2]) and standard
error ([[sigma].sub.h.sup.2]).

                                   3 Months of Age

                         Body Weight                Diameter

[h.sup.2.sub.S]    ** 0.306 [+ or -] 0.055   ** 0.233 [+ or -] 0.046
[h.sup.2.sub.D]    ** 0.457 [+ or -] 0.071   ** 0.321 [+ or -] 0.046
[h.sup.2.sub.FS]   ** 0.381 [+ or -] 0.063   ** 0.277 [+ or -] 0.051

                                   5 Months of Age

                         Body Weight                Diameter

[h.sup.2.sub.S]    ** 0.217 [+ or -] 0.042   ** 0.206 [+ or -] 0.041
[h.sup.2.sub.D]    ** 0.409 [+ or -] 0.064   ** 0.500 [+ or -] 0.072
[h.sup.2.sub.FS]   ** 0.313 [+ or -] 0.054   ** 0.353 [+ or -] 0.058

** Denotes very significance between [h.sub.2] with
zero (P < 0.01); [t.sub.0.01] [infinity] = 2.576.


ACKNOWLEDGMENTS

The authors thank J. Song, G. D. Wang, R. L. Xing, and S. G. Yan for their invaluable assistance in the laboratory production of the family lines. They also thank J. M. Lawrence for editing the paper.

LITERATURE CITED

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LIU LIU Linköpings Universitet (Sweden)
LIU Long Island University (New York)
LIU Line Interface Unit
LIU Lightguide Interconnection Unit (AT&T)
LIU Laugh It Up
 XIAOLIN, (1),(3) CHANG YAQING, (2) XIANG JIANHAI, (1) * DING JUN (2) AND CAO XUEBIN (2)

(1) Experimental Marine Biology marine biology, study of ocean plants and animals and their ecological relationships. Marine organisms may be classified (according to their mode of life) as nektonic, planktonic, or benthic. Nektonic animals are those that swim and migrate freely, e.g.  Laboratory, Institute of Oceanology, CAS, Qingdao 266071, China, (2) Key Lab of Mariculture mariculture

marine aquaculture.
 and Biotechnology of the Ministry of Agriculture, Dalian Fisheries University Dalian Fisheries University (大连水产学院) is a university located in Dalian, China. Founded in 1952, it is the sole university featuring fisheries science courses in northern China. Over 7,000 students are enrolled there. , Dalian 116023, China; (3) College of Animal Science and Technology, Northwest Sci-Tech University of Agriculture and Forestry, Yangling, Shaanxi 712100, China

This is contribution number G1999012009 of 973 from the Chinese National Fundamental research project and Chinese High Technology Plan (2002AA628170).

* Corresponding author. E-mail: jhxiang@ms.qdiao.ac.cn
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