Relationships between the Sphaerularia nematodes and Bumble bees: from host manipulation to indirect interactions within communities.

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K06413
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 45040:Ecology and environment-related
• Research Institution: University of Toyama
• Principal Investigator: Ishii Hiroshi 富山大学, 学術研究部理学系, 教授 (90463885)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 寄生生物 / 宿主操作 / マルハナバチタマセンチュウ / マルハナバチ / 行動 / 群集

Outline of Final Research Achievements

Sphaerularia bombi Dufour is a major parasite of bumble bee queens that manipulates its host’s behavior: parasitized queens do not breed and found nests but continue to fly into the early summer months. To understand the relationships between Sphaerularia nematodes and their host, Bumble bees, we observed the behavior of the parasitized queens of bumble bees and analyzed metapopulation genetic structure of both the hosts and the parasites. Our major findings are as follows. (1) Sphaerularia nematodes contains several cryptic species. (2) Host-specificity of each cryptic species would be very low. (3) Cross-species parasite transmission between host species likely have occurred but its frequency would be very small. (4) exotic lineages of the nematodes would not have invaded in Japan. (5) Dispersal of Bumble bee queens would highly be restricted by host manipulation by Sphaerularia nematodes.

Free Research Field

生態学

Academic Significance and Societal Importance of the Research Achievements

今回の研究から、マルハナバチタマセンチュウには隠蔽種が存在すること、その隠蔽種には寄主特異性はないこと、マルハナバチ種間での感染の頻度は低く抑えられていること、外来系統のタマセンチュウは日本に侵入していないと思われることなどが示された。また、タマセンチュウが、宿主の移動分散を抑制していることを支持する結果を、初めて提示することができた。マルハナバチという、生態系のキーストーン種と呼べるほどに重要な送粉者の寄生虫であるにも関わらず、研究例が非常に少ないマルハナバチタマセンチュウの生態に、新たな知見を加えることができたと考えている。