Takashi Oshiro

Triploidy Induction in an Atherinid Fish, the Pejerrey (Odontesthes bonariensis)

Abstract Experiments were conducted on triploidy induction and effects of triploidy on growth and survival of embryos, larvae, and juveniles of pejerrey, a freshwater atherinid fish. Eighty minutes of cold shock (0.5–0.8°C) starting 6 min after egg activation at 18.5°C consistently induced 100% triploidy, as assessed by chromosome counting of juvenile offspring from five different females. Cold-shocked groups had mean relative survival rates of 94.26, 84.15, 53.16, 65.97, and 68.60% at 20 h and 6–7 d after egg activation, at hatching, and at 2 and 20 d after hatching, respectively. Cumulative mortality among cold-shocked groups up to 20 d after hatching exceeded 80%. Critical mortalities were encountered between the eyed-egg stage and a week after hatching. Triploids showed higher rates of embryo and larval abnormalities (ocular malformation, dilation of the pericardial cavity, bulges in the head, and curling or bending of the body). Triploid larvae and juveniles had variable performance in short-term sur...

Chromosome Synapsis and Recombination during Meiotic Division in Gynogenetic Triploid Ginbuna, Carassius auratus langsdorfii.

Electron microscope examinations of primary oocytes of gynogenetic triploid ginbuna (Carassius auratus langsdorfii) and diploid gengoroubuna (Carassius auratus cuvieri) were carried out. Typical synaptonemal complexes were observed in both subspecies. In addition, clear differences in PGM-A electrophoretic patterns between a female parent ginbuna and her offspring were detected. It was concluded that synapsis and recombination occur between at least some homologous chromosomes in triploid ginbuna.

Two tandemly arrayed transfer-RNA-derived SINEs of the medaka (Oryzias latipes)

Abstract: Two tandemly arrayed short interspersed repetitive element (SINE) sequences were found in medaka (Oryzias latipes). These two SINE sequences, designated SINE1 and SINE2, were flanked by a 180-bp AT-rich region. Both appeared to be derived from transfer RNA. The former exhibited 80% sequence homology to human tRNAAla and the latter exhibited 94% sequence homology to rat tRNASer. SINE1 contained the retroviral U5 region, whereas SINE2 did not. This is the first sequence-level demonstration of the existence of neighboring SINEs in medaka.

Fertility of triploid backcross progeny, (GengoroubunaCarassius auratus cuvieri ♀ × carpCyprinus carpio ♂)F11 ♀ × carp or gengoroubuna ♂

The fertility of triploid backcross progeny, (gengoroubunaCarassius auratus cuvieri ♀ × carpCyprinus carpio ♂) F1 ♀ × gengoroubuna or carp ♂ is reported. In females, spawning could be induced by the injection of pituitary extracts. The fertilization rates were from 52.4 to 88.6%, and free swimming rates from 2.6 to 34.4%. Many normal larvae were obtained after crossing with the sperm of gengoroubuna. However, after crossing with sperm of the loachMisgurnus anguillicaudatus, most of the embryos died before hatching and no normal larvae were obtained.Sperm could not be stripped from the progeny of either type of triploid backcross after the injection of pituitary extracts. Under light microscope, each seminal lobule in the testis was mainly occupied by spermatocytes in various stages. Some spermatids were found in part of the lobules, but no spermatozoa were observed.These facts suggest that the laboratory-reared, triploid backcross progeny may represent an intermediate step in the evolution of a gynogenetic triploid form.