Gender-typical olfactory regulation of sexual behavior in goldfish.

It is known that olfaction is essential for the occurrence of sexual behavior in male goldfish. Sex pheromones from ovulatory females elicit male sexual behavior, chasing, and sperm releasing act. In female goldfish, ovarian prostaglandin F2α (PGF) elicits female sexual behavior, egg releasing act.

Histological observations of early gonadal development to form asymmetrically in the dwarf gourami Colisa lalia.

The asymmetrical and latitudinal formation of the gonads during early development in the dwarf gourami Colisa lalia was histologically observed using fish reared in laboratory. Hatching larvae obtained 33 hours after spawning possessed primordial germ cells (PGCs), which aggregated to the dorsal surface of the gut. In prolarvae on day 7, the gonadal anlagen were still situated on the dorsal surface of the gut, however, in those on day 10, the left gonadal anläge began to shift leftward, although the coelom did not develop sufficiently.

Sexual bipotentiality of behavior in male and female goldfish.

It is known that in goldfish Carassius auratus, a non-sex changing fish, prostaglandin (PG) treatment can induce female-typical sex behavior in males, and androgen treatment can induce male-typical sex behavior in females. These facts suggest that goldfish have a sexually bipotential brain even after attaining sexual maturity unlike mammals which have sexually differentiated brain. In the present study, in order to further characterize the brain function of goldfish, whether hormonal treatments which induce heterotypical sexual behavior suppress the occurrence of sex-typical behavior and whether sex-typical and heterotypical behavior can be induced in a relatively short time were examined.

Influences of establishment and maintenance of territory on reproductive activity in the male dwarf gourami Colisa lalia.

We examined the importance of establishment and maintenance of territory on reproductive activity in the male dwarf gourami, Colisa lalia. After three males had been forced to fight for territory (five sets) for three weeks, social status was divided into three classes: the territorially dominant male, which guarded the territory under the floating nest; the second male which remained near the nest and occasionally attacked the dominant male; and the third male which was non-aggressive and remained at a distance from the other two males. Comparing testicular size by gonadosomatic indices (GSI) after three weeks of aggression, GSI of the dominant male (1.

Characterization of an alternative chromatin remodeling to parasperm in a cottid fish, Hemilepidotus gilberti.

The dimorphic sperm of Hemilepidotus gilberti, i.e., haploid eusperm and diploid parasperm, have different morphologies corresponding to their own roles in fertilization.

Production of recombinant Japanese eel gonadotropins by baculovirus in silkworm larvae.

Recombinant follicle-stimulating hormone (reFSH) and luteinizing hormone (reLH) of the Japanese eel Anguilla japonica were produced by baculovirus in silkworm Bombyx mori larvae. cDNAs encoding Japanese eel gonadotropin subunits (i.e.

Seasonal changes in sex ratio, maturation, and size composition of fresh water snail, Sinotaia quadrata histrica, in Lake Kasumigaura.

Sinotaia quadrata histrica is a fresh water viviparous snail distributing from the Kanto region to Kyushu Island, Japan. About 7000 snails were collected in Lake Kasumigaura (L. Nishiura and L.

Ultrastructural observations of eu- and paraspermiogenesis in the cottid fish Hemilepidotus gilberti (Teleostei: Scorpaeniformes: Cottidae).

The developmental process of eu- and paraspermatozoa in the cottid fish, Hemilepidotus gilberti, was observed by electron microscopy. Euspermatozoa of H. gilberti consist of a thin disk-like sperm head (about 3 microm in length), a short middle piece, and a long flagellum, but lack an acrosome.