A new species was found in samples collected by students
A new species of parasite was found in snails and sparrows
Dr. Tsukasa Waki
Dr. Tsukasa Waki of the Faculty of Science and Haruki Furusawa (graduate student at the time of the research) of the Graduate School of Science both at the Toho University described a new species of parasite, Brachydistomum suzume (Japanese name: Suzume no haradumori), found in snail and sparrow samples collected by undergraduate students, and they investigated the life history of the new parasite. The result of the research was reported on February 19, 2024 in “Systematic Parasitology” (Electronic ISSN 1573-5192).
Dr. Tsukasa Waki
Dr. Tsukasa Waki of the Faculty of Science and Haruki Furusawa (graduate student at the time of the research) of the Graduate School of Science both at the Toho University described a new species of parasite, Brachydistomum suzume (Japanese name: Suzume no haradumori), found in snail and sparrow samples collected by undergraduate students, and they investigated the life history of the new parasite. The result of the research was reported on February 19, 2024 in “Systematic Parasitology” (Electronic ISSN 1573-5192).
Key Points:
During the laboratory examination of snail and sparrow (roadkill) samples collected by students, a parasite, which turned out to be a new species, was found in both the snail and sparrow samples. This new parasite was named Suzume no haradumori, Brachydistomum suzume.
The adult form of the parasite has only been found in sparrows. Sparrows are presently decreasing in population, and this decrease may result in a decrease in the number of this new parasite.
This new species parasitizes snails as larvae and sparrows as adults. We believe that there might be another intermediate host animal between snails and sparrows; however, the identity of this host animal is currently unknown. Detailed investigation of the areas where the snails and sparrows were collected from will provide information on the host animal.
There have been no reports of infection of this parasite in humans.
Content of Announcement:
Parasites constitute a diverse group, and each animal has its specific parasite. Therefore, parasites are inevitably attached to all animals in their surroundings. However, detailed information on the species, host range, and distribution of the parasite in this study remains unclear.
Figure 1. Hosts of Brachydistomum suzume: Eurasian Tree Sparrow (left) and snail (photographed species: Bradybaena similaris). Photo by Haruki Furusawa.
Hence, Dr. Waki of the Faculty of Science in Toho University has been discovering various parasites (species that do not infect humans) in places such as natural parks in urban areas, fields, and rice fields. During 2020–2021, Haruki Furusawa (a graduate student at the time of the research) and Miko Takayama (an undergraduate student at the time of the research) of the Department of Life Sphere Environmental Science in the same Faculty collected snails and sparrows from Chiba and Ibaraki Prefectures while shopping and examined them in the laboratory. The larva of the parasite (called sporocysts) was found in the snail samples, whereas the adult form was found in the sparrow samples. DNA analysis revealed that the larva and adult parasites were of the same species and that the species was a new species. The new species was named Brachydistomum suzume (Japanese name: Suzume no haradumori ) (Figure 2).
Figure 2. Adult Brachydistomum suzume : Collected from the bile duct of a Eurasian Tree Sparrow. Approximately 2 mm in length. Photograph by Haruki Furusawa.
Additional investigations revealed that Brachydistomum suzume is distributed from Kanto to Shikoku and can parasitize four species of snail as larvae. This parasite does not show strong pathogenicity to sparrows; hence, it is believed to have a symbiotic relationship with them. To date, only the adult form of Brachydistomum suzume has been found in sparrows. The population of sparrows is currently decreasing, and this decrease may decrease the population of this parasite. The group of parasites, which Brachydistomum suzume belongs to (family Dicrocoeliidae of trematodes) generally after leaving snails, infects other invertebrates and subsequently adult vertebrates, such as birds. Brachydistomum suzume also releases larvae called cercariae from the sporocyst larvae that infect snails, and these larvae are believed to infect other invertebrates (Figure 3). It is believed that this parasite become adults when eaten by sparrows. The intermediate host animal that exists between snails and sparrows is currently unknown; however, the host is certainly of a size that can be eaten by sparrows. Detailed investigation of the areas where the snails and sparrows were collected from will provide more information on the host animal.
Figure 3. Current known life cycle ofBrachydistomum suzume : Adult parasitizes sparrows, and sporocyst larval parasitizes four species of snails. The second intermediate host (host parasitized by larvae in the second stage) remains unknown. Illustration by Rena Doi and Tsukasa Waki.
Journal
Systematic Parasitology, February 19, 2024 issue
Title
A description of a new species of the genus Brachydistomum (Trematode, Dicrocoeliidae) from the Eurasian Tree Sparrow Passer montanus in Japan, with a report on the first intermediate host.
