Female medaka, Oryzias latipes, is known to deposit their eggs on substrates in shallow waters. However, there is a possibility that the eggs will be exposed to the air and dry when the surrounding water level falls. In the present study, we examined the resistance to desiccation of fertilized eggs of medaka. Each egg was placed in a plastic dish filled with water and subjected to one of the following three treatments for one or three days at different times after fertilization: 1) placed on a wet filter paper and exposed to the air (wet group), 2) placed on a dry dish (dry group), and 3) kept in water (control). Most eggs in the control and the wet group hatched, and all the eggs of the dry group died. The results of the wet group indicate that fertilized eggs of medaka have some resistance to desiccation.

View full abstract

Construction of artificial river and lake banks changes the aquatic environment, and these changes are known to cause decreases of aquatic plants in shallow waters. We conducted experiments to examine the involvement of aquatic plants in spawning behavior of goldfish, Carassius auratus, and cruicuan carp, Carassius buergeri subsp.2. The spawning behavior was induced by injecting prostaglandin F2α into females. Pairs of male and female goldfish or crucian carp were placed in experimental tanks with or without aquatic plants made of acrylic yarn. Both goldfish and crucian carp spawned actively onto the aquatic plants whereas the behavior significantly decreased without the aquatic plants. The present experiments demonstrate that aquatic plants are essential as spawning substrates for performance of spawning behavior of these species. It is critical for conservation of fish species that use aquatic plants as spawning substrates to maintain aquatic plants on river and lake banks.

View full abstract

Mammal fauna in an isolated green area in a Tokyo suburban residential area was studied. Using a camera-trapping method and interviewing some residents in the area, a total of thirteen mammal species including two temporal visitors were recorded. Among them, breeding of Japanese badgers (Meles anakuma) in a suburban residential area was confirmed for the first time. The RAIs (relative abundance indices) in 2008 and 2018 were compared among medium-sized Carnivores such as badgers, raccoons (Procyon lotor), raccoon dogs (Nyctereutes procyonoides), masked palm civets (Paguma larvata), and domestic cats (Felis catus). In these ten years, raccoons increased drastically, and badgers, raccoon dogs, and cats also increased. Masked palm civets did not show much change. Despite overlapping diet resources, the increase in raccoons did not influence the size of population of other medium-sized mammals.

View full abstract

Dispersal of Manchurian walnut seeds depends mainly on zoochory due to their size. Eurasian red squirrels have a behaviour of caching Manchurian walnuts. This behaviour is scatter-hoarding of large seeds. Snag and dying fallen trees are major resources by themselves in forest ecosystems. Slash or woodpiles after tree felling have the same function as snag and dying fallen trees. The present paper aims to report that Eurasian red squirrels utilize piles of slash, to discuss the importance of slash on the forest floor, and to determine which properties of the piles of slash influence Eurasian red squirrels' access to the slash. Among the woodpile properties, the results showed a negative correlation between the distance to the Manchurian walnut tree and the number of walnuts having feeding marks, and a positive correlation between the number of logs in a woodpile and the number of walnuts having feeding marks. Eurasian red squirrels may use woodpiles as a safe feeding site.

View full abstract

Japanese badger was captured on a motion-sensor camera on the Tamagawa Gakuen campus in Machida City, Tokyo, where no such record has been reported before. Although only two pictures were taken in July of 2018, possibe establishment of Japanese badger on the campus is presumed because the species can inhabit small, urban green areas.

View full abstract

A supplementary literature survey was conducted on bryophytes reported from Kanagawa Prefecture, Japan. Including infraspecific taxa, a total of 663 species, which were classified into 452 species of mosses, 201 species of liverworts, and 10 species of hornworts, were recorded.

View full abstract