Tsunenori Koga

Mate acceptance and guarding by male fiddler crabs Uca tetragonon (Herbst)

Abstract The fiddler crab, Uca tetragonon (Herbst) mates both on the surface near female-defended burrows and underground in male-defended burrows. In underground mating, which requires relatively high male investment, males attract both non-ovigerous and ovigerous females into their burrows by claw waving. Males aggressively expel some females soon after they enter their burrows and others after pair formation, but before females spawn. Finally males guard some females in their burrows until they spawn, which presumably ensures paternity. Males do not select mates of a particular body size, but they do differentially accept females with late-stage eggs, those about to release larvae and spawn another clutch. Except at the beginning of the reproductive season, few ripe non-ovigerous females are available because females spawn successively and only in moderate synchrony. By differentially accepting late stage ovigerous females, males may increase their fertilization rates because they minimize the time they spend guarding each of their mates to ensure their paternity. A male-biased operational sex ratio and a high last male advantage in sperm competition are two conditions that may have favored male choice based on female guarding time in this species.

Sexual Differences in Foraging Behavior of Sika Deer, Cervus nippon

We compared the foraging behavior of five age-sex classes of sika deer ( Cervus nippon nippon ) in grasslands in Nozaki Island, Japan. Seasonal changes in feeding time and food plants were greater for males than for females. For males, feeding time decreased and time allocated to social activities increased with age in the breeding season. In spring, when antlers of deer began to regrow, adult males spent more time feeding on plants with high ash contents than did younger males and females. In winter, males spent more time feeding on plants with high protein content than did females. The trend was much different from that reported in many previous investigations, perhaps because of abundant food in our study area, which was at a low latitude.

Mating behavior of the sand bubbler crab Scopimera globosa

ABSTRACT The mating behavior of the sand bubbler crab Scopimera globosa was studied in an intertidal area of Fukuoka, Japan, from 1988-1991. This species mates both on the surface and underground, as do some fiddler crabs. In surface copulations, wandering males mate sequentially with resident females beside burrows of females. In underground copulations, resident males chase and capture wandering females, carry them to their burrows and push them below. Males then enter their burrows and plug them within minutes. Pairs presumably copulate in these burrows. Unlike the fiddler crabs, however, most females that stayed in burrows of males did not have mature ovaries and wandered again within a few days. Consequently, only 30% of the females that stayed in burrows of males spawned in those burrows. After the spawning, males abandoned their burrows, while females remained in them during incubation. Thus, forced copulation characterizes the mating system of this species, though there is room for female choice. Mating success was much lower in underground than in surface copulation. However, males that succeed in forcing females into their burrows may gain a reproductive advantage, because the sperm of the last male to mate with a female prior to egg extrusion is used to fertilize most of the eggs.

Territorial behavior of both sexes in the water striderMetrocoris histrio (Hemiptera: Gerridae) during the mating season

Territorial behavior of overwintered individuals of Metrocoris histriowas observed in an upstream area. Adults of both sexes held territories, but male territories were larger than those of females. Severe competition occurred among males for territories which give them access to receptive females. The effects of male body length and midleg length on establishment of territories were not significant. The effect of female midleg length on activity of females entering preferred foraging sites was equally not significant. Instead, territorial behavior increased with male age and males stayed longer at prime sites. Females of intermediate age were likely to occupy prime sites. Females had longer territory residence time than males. The sexes were dimorphic with respect to midleg length, and dimorphism in M. histriomay be related to a difference in life history, in that sexual selection may be relaxed due to asynchronous adult emergence patterns.

Abstracts from the Japanese Journal of Limnology

The Japanese Journal of Limnology is another official publication of the Japanese Society of Limnology. The original papers in the journal were peer-reviewed by a few authorized referees, and appeared in Japanese with English abstracts.