Convergent evolution in morphological characters of dicyemids

2018 Fiscal Year Final Research Report

• Project/Area Number: 26440216
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Biodiversity/Systematics
• Research Institution: Osaka University
• Principal Investigator: Furuya Hidetaka 大阪大学, 理学研究科, 准教授 (20314354)
• Project Period (FY): 2014-04-01 – 2019-03-31
• Keywords: 分類 / 形態形質 / 収斂 / 進化 / ニハイチュウ / 寄生虫 / 頭足類 / 棲み分け

Outline of Final Research Achievements

Dicyemids are microscopic animals and endoparasites that live only in the renal sacs of benthic cephalopod molluscs. The adult stage has a distinct anterior region termed a“calotte”by which they attach to the renal appendages of the host Calotte shapes of dicyemids detected in different host species more closely resembled each other than in dicyemids found in the same host species. Species of dicyemids that possess similar calotte shapes are very rarely found together in a single host individual. This appears to be morphological convergence in calotte shapes. The molecular phylogenetic analyses indicated a close relationship among species living in the same host renal sacs. In addition, a host-switching likely occurs between species that have similar inhabitants in several species of host cephalopods. Thus, the calotte shape pattern of dicyemids may be formed by both convergent evolution and host-switching.

Free Research Field

動物系統分類学

Academic Significance and Societal Importance of the Research Achievements

ニハイチュウ類は多細胞動物のなかで最も少数の細胞からなり、体制や発生が簡単である。そのため、ニハイチュウ類がもつ分類形質は形態的に明瞭で解析が容易である。また、動物系統学上の興味だけでなく、その生活様式が片利共生であるがゆえに、他の動物にはみられないユニークな特徴をもち、他の動物にない現象へのアプローチが可能である。本研究は、アフリカ巨大湖のカワスズメの形態における収斂現象に対して、微小環境での収斂現象のモデルとなる。