First Detailed Record of Symbiosis Between a Sea Anemone and Homoscleromorph Sponge, With a Description of Tempuractis rinkai gen. et sp. nov. (Cnidaria: Anthozoa: Actiniaria: Edwardsiidae)
Authors
Takato Izumi1, Yuji Ise2,*, Kensuke Yanagi3, Daisuke Shibata4 and Rei Ueshima1 * Corresponding author. E-mail: ug@bio.nagoya-u.ac.jp 1 Department of Biological Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan 2 Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, Sugashima, Toba, Mie 517-0004, Japan 3 Coastal Branch of Natural History Museum and Institute, Chiba, Kastsuura, Chiba 299-5242, Japan 4 Shimoda Marine Research Center, University of Tsukuba, 5-10-1, Shimoda, Shizuoka 415-0025, Japan
External view of Tempuractis rinkai gen. et sp. nov. and its host sponge Oscarella sp. collected from Misaki, Kanagawa, including a holotype (NSMT-Co 1573) and four paratypes (CMNH-ZG 08969 to 08972).
Abstract
A new species in a new genus of sea anemone, Tempuractis rinkai gen. et sp. nov., was discovered at several localities along the temperate rocky shores of Japan. The new species is approximately 4 mm in length and has been assigned to family Edwardsiidae, because it has eight macrocnemes, lacks sphincter and basal muscles, and possesses rounded aboral end. The sea anemone, however, also has a peculiar body shape unlike that of any other known taxa. This new species resembles some genera, especially Drillactis and Nematostella, in smooth column surface without nemathybomes or tenaculi, but is distinguishable from them by several morphological features: the presence of holotrichs and absence of nematosomes. Furthermore, this edwardsiid species exhibits a peculiar symbiotic ecology with sponges. Therefore, a new genus, Tempuractis, is proposed for this species. In the field, T. rinkai sp. nov. was always found living inside homosclerophorid sponge of the genus Oscarella, which suggests a possible obligate symbiosis between Porifera and Actiniaria. The benefit of this symbiosis is discussed on the basis of observations of live specimens, both in the aquarium and field. This is the first report of symbiosis between a sea anemone and a homoscleromorph sponge.
KEYWORDS: Japan; edwardsiid; intertidal; marine invertebrates; overhang; species description; symbiotic relationship; taxonomy; transmission electron microscopy (TEM)
RESULTS
Order ACTINIARIA Hertwig, 1882 Family Edwardsiidae Andres, 1881
Tempuractis gen. nov. Izumi, Ise and Yanagi (Japanese name: tempura-isoginchaku-zoku)
Etymology. Tempura is a deep-fried, batter-coated nugget of seafood and/or vegetables in Japanese cuisine. This word comprises the first half of the Japanese name of the type species of this genus, as the shape of the actiniarian when embedded in a sponge tissue resembles shrimp tempura. The siffix -actis is commonly used in actiniarian genus names, meaning radiation of sunshine in Greek. The new genus name is feminine in gender.
Tempuractis rinkai sp. nov. Izumi, Ise and Yanagi, 2018 (New Japanese name: tempura-isoginchaku)
Etymology. The species epithet is dedicated to marine biological stations around Japan. The first specimens of this species were collected from a rocky shore in front of the Misaki Marine Biological Station (the University of Tokyo). This station is called “Misaki rinkai jikkenjo” in Japanese (“rinkai” means seaside and “jikkennjo” means research facility). Other specimens were collected during a subsequent faunistic survey in collaboration with other marine biological stations: Sugashima Marine Biological Laboratory (Nagoya University) and Sado Marine Biological Station (Niigata University).
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