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Plasticity in sex differentiation is known to be common in teleost fishes. Anemonefishes are protandrous; females are the largest and dominant members of social groups, displaying frequent aggressive behavior towards other members of groups. The second-ranked individuals become males and others remain as non-reproductive individuals. Here we examine the influence of social interaction in-group on sex differentiation in the false clown anemonefish, Amphiprion ocellaris, under laboratory conditions. Three juvenile anemonefish were kept in a tank for 180 days and their behaviors observed once a month. The social rank of individuals was distinguishable by their interactions in a group, with rank order clearly correlated with aggressive and appeasing behaviors. The dominant individuals occupied the shelter in the tank from the start to completion of the observation period. The body mass of dominant individuals increased compared to group-housed control fish, while third-ranked individuals showed growth suppression. The ratio of testicular tissue in gonads increased in dominant and second-ranked individuals but decreased in the third-ranked individuals. Differences in the plasma concentrations of estradiol, testosterone, and cortisol were not significant, but the concentration of 11-ketotestosterone was significantly higher in dominant individuals. These results suggest that, in false clown anemonefish, reproductive suppression of lower-ranked individuals becomes apparent in the first stage of group formation, and sex differentiation of upper-ranked individuals is gradually determined by long-term social interactions.

To test the hypothesis that the primer pheromone responsible for inducing the "male effect" is produced in the sebaceous gland androgen dependently, we examined the correlation between morphological changes of sebaceous glands and the pheromone activity in skin samples taken from castrated goats that had been treated with testosterone. Five castrated goats were implanted s.c. with testosterone capsules to maintain physiological levels of plasma testosterone for four weeks. Skin samples were obtained from the head region on Day 0 (the day of testosterone implant), Day 7, Day 14, Day 28 (the day of testosterone removal), Day 36, Day 42, and Day 56. Matched blood samples were also collected for measurement of testosterone concentration. The pheromone activity of the ether-extracts of the upper dermal layer containing sebaceous glands was assessed by its stimulatory effect on the hypothalamic GnRH pulse generator, which was monitored for changes of specific multiple unit activity (MUA) in ovariectomized estradiol-primed goats as described previously. The sebaceous gland enlarged during the testosterone treatment but reduced in size after testosterone removal. The pheromone activity first appeared in 2 out of 5 goats on Day 7 and in all the 5 goats by Day 28. Fourteen days after testosterone removal (Day 42), the pheromone activity was no longer detectable in any of the 5 goats. In short, the sebaceous gland size and the pheromone activity shifted almost in parallel. The present results provide strong support for the view that the primer pheromone is produced testosterone dependently in the sebaceous gland of the male goat.

The Noma horse is a Japanese breed from the Noma region of Imabari City, Ehime Prefecture. To obtain reference hematological and biochemical values, we performed examinations in 39 clinically healthy, mature Noma horses managed at the Imabari public ranch. Hematological and biochemical results of Noma horses were close to the normal ranges of horses in the U.S.A. The erythrocyte parameters and hepatobiliary enzyme levels in Noma and Kiso horses were lower than those in Japanese racehorses. Noma horses showed higher erythrocyte parameters and triglyceride concentrations and a lower creatinine concentration compared with those in Kiso horses. These data represent the first report of reference values for Noma horses and may be useful to improve their management.