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GB 20556-2006Swimming crab (English PDF)

三疣梭子蟹

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Issued by

State Administration for Market Regulation

Level / Type

National · Mandatory

Issue date

February 27, 2026

Implementation date

September 1, 2026

Scope

GB 20556-2006 is the English-translated version of 三疣梭子蟹.

GB 20556-2006 — The study describes the structural characteristics, growth and reproduction features, molecular genetic characteristics, and judgment rules, and outlines the corresponding detection methods.

This document applies to the germplasm identification and testing of the swimming crab (Portunus trituberculatus).

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Document preview — GB 20556-2006

National Standard of the People's Republic of China

ICS: 65.150
Classification: B 51
Replacing: GB/T 20556-2006

Issued by: State Administration for Market Regulation

Foreword
1 Scope
4 Scientific name and classification
4.1 Scientific name
4.2 Classification Status
5 Main morphological and structural characteristics
5.1 External Form
5.2 Countable traits
5.3 Measurable properties
6 Growth and Reproduction Characteristics
6.1 Growth
6.2 Reproduction
7 Molecular genetic characteristics
8 Detection Methods
8.1 Main Morphological and Structural Characteristics
8.2 Growth and Reproduction Characteristics
8.3 Molecular genetic characteristics
9 Judgment Rules
Foreword

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents".

Drafting.

This document replaces GB/T 20556-2006 "Portunus trituberculatus". Compared with GB/T 20556-2006, the main differences are structural adjustments and editorial changes.

Aside from the modifications, the main technical changes are as follows.

a) The "classification status" has been changed (see 4.2, 3.2 in the 2006 edition);

b) The section on "Distribution and Ecological Habits" (see Chapter 4 of the 2006 edition) has been removed;

c) The external morphology description has been changed (see 5.1, 2006 edition 5.1);

d) The measurable characteristics have been modified (see 5.3, 2006 version 5.3), and corresponding detection methods have been added (see 8.1.3);

e) The wording for "growth" has been changed (see 6.1, 2006 edition 6.1);

f) The content regarding egg production has been removed, and the range for the number of eggs carried has been expanded (see 6.2.3, 6.2.4 in the 2006 edition);

g) Breeding water temperature has been removed (see 6.2.5 in the 2006 edition);

h) The section on "Biochemical and Genetic Characteristics" (see Chapter 7 of the 2006 edition) and the corresponding detection methods (see 9.2 of the 2006 edition) have been deleted;

i) The "Molecular Genetic Characteristics" section has been revised (see Chapter 7, Chapter 8 in the 2006 edition), and corresponding detection methods have been added (see 8.3);

j) Methods for detecting key morphological and structural features and growth and reproductive characteristics have been added (see 8.1 and 8.2);

k) The "Judgment Rules" have been changed (see Chapter 9, Chapter 10 in the 2006 edition).

Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.

This document was proposed by the Ministry of Agriculture and Rural Affairs of the People's Republic of China.

This document is under the jurisdiction of the National Technical Committee on Fisheries Standardization (SAC/TC156).

1 Scope

The study describes the structural characteristics, growth and reproduction features, molecular genetic characteristics, and judgment rules, and outlines the corresponding detection methods.

This document applies to the germplasm identification and testing of the swimming crab (Portunus trituberculatus).

4 Scientific name and classification

4.1 Scientific name

4.2 Classification Status

Phylum Arthropoda, Class Malacostraca, Order Decapoda, Family Portunidae, [unclear text - possibly related to crabs or molluscs] the genus *Portunus*.

5 Main morphological and structural characteristics

5.1 External Form

The cephalothorax is fusiform with three wart-like projections; the dorsal surface is mostly tea-green, yellowish-brown, or purplish-red, while the ventral surface is grayish-white; the anterior lateral margin is oblique.

Arched, longer than the posterior lateral margin; the cephalothorax has nine serrated teeth on each of the two anterior lateral margins, with the ninth serration being particularly long and large; the chelipeds are well-developed, with the meristem prismatic in shape, internally...

The margins have blunt teeth; the dorsal surface of the chelipeds is purple with grayish-white spots; the first three pairs of walking legs are blue with purple dactyls; the fourth pair of walking legs has flattened and broad metacarpals and dactyls.

Thin; flat abdomen, male crabs have a triangular or bell-shaped navel, while female crabs have a semi-circular or semi-elliptical navel. The external morphology of the three-spined swimming crab is shown in Figure 1.

5.2 Countable traits

5.2.1 There are three prominent verrucous elevations on the surface of the cephalothorax, one in the gastric region and two in the cardiac region.

5.2.2 The two anterior lateral margins of the cephalothorax each have 9 serrated teeth.

5.2.3 The frontal margin has 2 to 6 small teeth, usually 4.

5.2.4 There is a pair of stalked compound eyes that can rotate on both sides of the forehead.

5.2.5 Five pairs of chest and feet.

5.3 Measurable properties

After stage III juvenile crabs, the total carapace width ranges from 12.0 mm to 257.0 mm, which is 1.21 to 1.45 times the carapace width.

It is 1.92 to 2.52 times longer.

6 Growth and Reproduction Characteristics

6.1 Growth

The process involves a series of molts, resulting in intermittent growth. After molting, the animal's weight and size increase significantly within a short period.

6.2 Reproduction

6.2.1 Sexual maturity

Generally, male juvenile crabs in the first stage molt 8 to 10 times, while female crabs molt 9 to 10 times to reach sexual maturity.

6.2.2 Breeding season

Spring-breeding crabs reach sexual maturity in the autumn of the same year, while autumn-breeding crabs reach sexual maturity the following spring. Female crabs mate after their reproductive molt, and can mate multiple times in a single mating cycle.

spawning.

6.2.3 Egg holding capacity

3.5×104 capsules ~ 4.5×106 capsules.

7 Molecular genetic characteristics

The reference sequence of the mitochondrial COI gene is as follows (658 bp).

Intraspecific K2P (Kimura2-parameter) genetic distance should be less than 2%.

8 Detection Methods

8.1 Main Morphological and Structural Characteristics

8.1.1 External Form

Observe with the naked eye under natural light.

8.1.2 Countable traits

Observe and count with the naked eye.

8.1.3 Measurable characteristics

Measure the total nail width, nail length, and nail length using vernier calipers as per Appendix A, accurate to 0.1 mm. Weigh the body using an electronic balance, accurate to 0.1 g.

8.2 Growth and Reproduction Characteristics

8.2.1 Growth

The width of the entire nail was measured with calipers to an accuracy of 0.1 mm, and the weight was weighed with an electronic balance to an accuracy of 0.1 g.

8.2.2 Breeding season

It is determined by regularly observing the development of the gonads.

8.2.3 Egg holding capacity

Dry the berried crabs by patting their bodies, then use tweezers to remove all the eggs from their abdomens, removing any bristles, hairs, or other impurities. Use an electronic balance to...

Weigh (m1) (accurate to 0.1g). Randomly select 3 egg masses of approximately 1g each and weigh them accurately (m2). Place them in a graduated cylinder and seal with 5% formalin.

After fixation, bring the volume to 100mL with seawater. Use a dropper to repeatedly blow the fertilized eggs until they are evenly dispersed, then transfer 1mL to another beaker and add an appropriate amount of seawater.

Count the number of eggs using a transparent glass dropper, repeat 3 times and take the arithmetic mean (n). The number of brood eggs is calculated according to formula (1).

8.3 Molecular genetic characteristics

Test according to the method in Appendix B.

9 Judgment Rules

9.1 When the test results meet the requirements of Chapter 5, the species can be identified.

9.2 When the following situations occur, additional testing requirements from other chapters should be added, and a comprehensive determination of the species should be made based on the test results.

a) If Chapter 5 cannot be detected or accurately determined, add the content from Chapter 7;

b) When a third party requests testing of all or part of Chapter 6;

c) During full-item testing.

GB/T 20556-2026. Portunus trituberculatus ICS 65.150 CCSB51 National Standards of the People's Republic of China Replaces GB/T 20556-2006 swimming crab Published on 2026-02-27 Implemented on 2026-09-01 State Administration for Market Regulation the State Administration for Standardization issued a statement.