Time of sex differentiation, as well as effects of 4-nonylphenol (NP)on growth and sex differentiation in juvenile Macrobrachium rosenbergii were studied by morphologic observation and histological sections. Ten zoea were collected randomly every 3 days, fixed in Bouin's solution, then embedded in paraffin and sectioned. Transverse sections were stained with hematoxylin and eosin to identify its sex differentiation time. Juvenile M. rosenbergii were divided into 5 groups( n =200 per group) :control,5,15,45, and 135 μg/L NP,respectively. All these juvenile M. rosenbergii were immersed in different doses of NP solutions for 30 days, and 50％ NP solutions were renewed every 2 days to keep NP's steady concentration. Ten juvenile M. rosenbergii were collected randomly from each group on 15,20,25, and 30 d,and both the body mass and length were measured respectively for the assessment of NP on growth. Thirty juvenile M. rosenbergii were collected randomly from each group on 30 d to identify their sex by outward features( gonopore, appendix masculine, etc)under anatomical lens, and 10 were fixed, embedded and sectioned to observe its gonad histology. Data were subjected to one-way analysis of variance followed by Duncan's multiple rang test. Results showed that primordial germ cells (PGCs)appeared in 15 d larva;however, genital duct,a wrinkled and pimply plastron, and a sunken basal part on the 4th -5th walking legs appeared in 24 d larva in some M. rosenbergii. In addition, a rudiment of the appendix masculine on the internal of the 2nd pleopod was found in 45 d larva in some M. rosenbergii, and gonads could be identified easily as testis and ovary, respectively. M. rosenbergii larvae were not affected in their body weight and length if treated by NP less than 15 d, however, they were inhibited significantly in a dose-dependent manner if treated more than 20 d( P ＜0.05). Spermatogonium and oogonium were observed respectively in the testis and ovary in the control group on 30 d, however, gonads unidentified as male and female were found in the NP-treated groups, and the quantity of sex-unidentified M. rosenbergii increased with the doses of NP.Results suggested that the time of sex differentiation of larval M. rosenbergii occurred between 21 to 45 d larva and the change of external forms occurred before that of the internal forms. Furthermore, growth and testis development were inhibited possibly because of NP interfering with the processes of molt and vitellogenin synthesis.%采用外部形态观察和性腺组织学连续切片方法,确定罗氏沼虾幼虾的性别分化时期,并探讨壬基酚(NP)对罗氏沼虾幼虾(体长约1.5 cm)生长和性别分化的影响.结果表明,罗氏沼虾仔虾后15 d出现生殖原基;仔虾后24 d,部分仔虾第四至第五步足基部明显凹陷,腹甲出现皱折和突起,并出现生殖管;仔虾后45 d,部分仔虾第二游泳足内侧出现雄性附肢,性腺明显区分为精巢和卵巢.处理时间短于15 d,NP对罗氏沼虾幼虾生长无显著影响;但处理超过20 d,NP以明显的剂量依存关系显著抑制罗氏沼虾体长和体重(P＜0.05).实验结束时(30 d),对照组个体均已完成性别分化,精巢和卵巢内分别出现大量精原细胞和卵原细胞,但NP处理组无法鉴定性别的幼虾比例随NP剂量增加而增加.研究表明,罗氏沼虾幼虾外部性征出现略早于内部性征的分化,早期性别分化发生在仔虾变态后21～45 d;此外,NP可能通过干扰蜕皮及卵黄蛋白原合成从而抑制罗氏沼虾幼虾生长和精巢发育.
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