Histological observation of zebrafish (Danio rerio) androgenetic-induced eggs from 5 to 43 min after fertilization (AF).

(a–d) androgenetic haploid type; (e–h) triploid type; and (i–l) diploid or aneuploid type. (a) 5 min AF, the spindle was destroyed by cold-shock treatment, and part of the blastodisc swelled up with all the chromosomes; (b) 30 min AF, the blastodisc swelled further with all the chromosomes; (c) 35 min AF, the swelled blastodisc released as second polar body with all chromosomes; (d) 43 min AF, only one pronucleus was observed in the egg; (e) 5 min AF, part of the blastodisc swelled; (f) 30 min AF, the blastodisc swelled further with no chromosomes; (g) 35 min AF, few parts of the blastodisc were released, and all chromosomes remained in the egg; (h) 43 min AF, the zygote was formed by the fusing of female and male pronuclei; (i) 5 min AF, the unswelled blastodisc; (j) 15 min AF, parts of the blastodisc swelled up with some chromosomes, and other chromosomes were found at unswelled parts of the blastodisc; (k) 35 min AF, the second polar body was released with some chromosomes, and the unreleased chromosomes in the egg developed into the female pronucleus; (l) 43 min AF, the female pronucleus became bigger. Scale bars denote 10 µm. Abbreviation: 2PB, 2nd polar body; 2MeC, 2nd meiotic chromosomes; FN, female nucleus; FPN, female pronucleus; MPN, male pronucleus; ZY, zygote.

Induced androgenetic doubled haploids and clonal line in zebrafish (Danio rerio).

(a–f) The four different types of larvae hatched from eggs subjected to cold-shock treatment for 30 min at 7 ± 0.5 °C, followed by heat-shock treatment at 43 min AF. (a) and (b) Normal wild-type larva; (c) abnormal wild-type larva; (d) and (e) normal golden-type larva; and (f) abnormal golden-type larva. Scale bar denotes 1 mm. (g) DNA fingerprints were determined by amplified fragment length polymorphism using the selective primer combination E-AGC/M-CTT. dl: DNA ladder; B: golden-type male doubled haploid whose sperm was used for androgenesis induction; c1–c7: normal golden-type diploid progeny hatched from androgenesis (clonal fish); i1–i4: female intact control; i5–i8: male intact control.

Histological sections of intact control eggs from zebrafish (Danio rerio).

(a) Unfertilized eggs at metaphase of the second meiosis; (b) 10 min after fertilization (AF), second polar body was released, and the egg nucleus existed in the egg cytoplasm underneath the polar body; (c) 10 min AF, the condensed sperm nucleus and egg nucleus in the blastodisc; (d) 15 min AF, decondensed female and male pronuclei; (e) 25 min AF, metaphase of the first cleavage; (f) 30 min AF, anaphase of the first cleavage; (g) 35 min AF, prophase of the second cleavage; (h) 45 min AF, anaphase of the second cleavage. Scale bars denote 10 µm. Abbreviation: 2MeS, 2nd meiotic spindle; 2PB, 2nd polar body; FPN, female pronucleus; MN, male nucleus; MPN, male pronucleus; MiS, mitotic spindle; CF, cleavage furrow; ZY, zygote; AS, anaphase spindle.