Epizoanthus inazuma, Kise, Hiroki & Reimer, James Davis, 2016

Kise, Hiroki & Reimer, James Davis, 2016, Unexpected diversity and a new species of Epizoanthus (Anthozoa, Hexacorallia) attached to eunicid worm tubes from the Pacific Ocean, ZooKeys 562, pp. 49-71 : 54-56

Taxon classification Animalia Zoantharia Epizoanthidae

Epizoanthus inazuma sp. n.

Material examined.

Holotype. NSMT-Co1574 (MISE-HK54), 26°30'18.3"N, 127°51'02.3"E, Cape Manzamo, Onna Village, Okinawa, Japan, depth 24 m, collected by Hiroki Kise, July 21, 2014, divided in two pieces, one portion fixed in 99.5% EtOH and the other in 5-10% saltwater formalin, deposited in National Museum of Nature and Science, Tokyo, Japan. Paratype 1. RMNH 42100 (MISE-HK9) 26°30'18.3"N, 127°51'02.3"E, Cape Manzamo, Onna Village, Okinawa, Japan, depth 25 m, collected by James D. Reimer, October 21, 2008, fixed in 99.5% EtOH, deposited in Naturalis Biodiversity Center, Leiden, The Netherlands. Paratype 2. USNM 1296757 (MISE-HK66) 26°26'26.5"N, 127°42'43.7"E Cape Zanpa, Yomitan Town, Okinawa, Japan, depth 34 m, collected by Hiroki Kise, August 5, 2014, fixed in 99.5% EtOH, deposited in Smithsonian Institution National Museum of Natural History, Washington, D.C., USA. Other material. MISE-HK43 26°30'18.3"N, 127°51'02.3"E, Cape Manzamo, Onna Village, Okinawa, Japan, depth 30 m, collected by Hiroki Kise, April 5, 2014, fixed in 99.5% EtOH.

Description of holotype.

Colony of approximately 140 polyps connected by thin, under-developed coenenchyme on eunicid worm tubes. The tubes are made of a chitin-like substance. Polyps approximately 0.7 to 1.2 mm high (=length) from coenenchyme, and 1.0 to 1.65 mm in diameter. Polyps were attached from base to proximal extremity of zig-zag shaped tubes of eunicid worms, and attached to not only bent sections but also to other locations. Polyp external coloration black, oral disk light brown to brown, lighter nearer the oral opening and darker around oral disk edges. Polyps encrusted with sand and silica particles in their coenenchyme and ectodermal tissue; with few sand particles in the mesoglea.

Diagnosis.

Morphology. Polyps connected by thin, under-developed coenenchyme on eunicid worms belonging to family Eunicidae . Maximum diameter of polyps approximately 4 mm, maximum height approximately 5 mm in situ. Epizoanthus inazuma sp. n. has 20-22 tentacles that are cylindrical and either as long or longer in comparison to oral disk diameter.

Internal anatomy. While the 5th mesentery from dorsal directive is obviously a complete mesentery (macrocnemic arrangement), the 6th mesentery is also a complete mesentery (Figure 2b). Azooxanthellate. Mesogleal thickness approximately 75 µm.

Cnidae. Holotrichs, basitrichs, microbasic p-mastigophores, spirocysts (see Table 1 into this paper, Figure 3).

Etymology.

Epizoanthus inazuma sp. n. is named after the Japanese word ‘inazuma’ meaning ‘lightning’, as colonies of this species are attached to eunicid worm tubes, and the worm tube shape resembles a classic lightning-bolt shape. Common Japanese name. ‘Inazuma-yadori-sunaginchaku’ (new Japanese name).

Distribution and habitat.

Epizoanthus inazuma sp. n. is found in low-light environments such as on mesophotic coral reef slopes and reef floors, or on the sides of overhangs. Specimens were collected from 10 to 40 m depth.

Epizoanthus inazuma sp. n. is currently known only from Okinawa (Figure 1). However, it may be distributed in other locations in the Pacific Ocean, as it is likely this species has been confused with Epizoanthus illoricatus and/or Epizoanthus beriber sp. n. in the past due to their similar external morphology. Epizoanthus illoricatus has been found in many areas of the western Pacific Ocean such as in New Caledonia ( Sinniger 2006; Sinniger et al. 2009), the Yellow Sea, China ( Pei 1999), Papua New Guinea (BW Hoeksema, pers. comm.), Australia ( Lindsay et al. 2012), Taiwan ( Reimer et al. 2013), and Palau ( Reimer et al. 2014), and Epizoanthus inazuma sp. n. may be similarly distributed.

Remarks.

Epizoanthus inazuma sp. n., Epizoanthus beriber , and Epizoanthus illoricatus can be distinguished from most other Epizoanthus species by their specific substrate (eunicid worm tubes) in the Pacific Ocean. Acrozoanthus australiae (family Zoanthidae ) is also associated with eunicid worm tubes, but Epizoanthus inazuma sp. n. can be distinguished from Acrozoanthus australiae due to its mesenterial arrangement (the family Zoanthidae is within the suborder Brachycnemina), as well as by many obvious external features such as coloration, polyp size, and by being azooxanthellate ( Acrozoanthus australiae is zooxanthellate). Epizoanthus inazuma sp. n. is very similar to Epizoanthus illoricatus (Figure 4a, b, c, f), but can be distinguished by differing mesenterial arrangement (6th mesentery is complete as opposed to 6th mesentery being incomplete in Epizoanthus illoricatus ) (Figure 2). Epizoanthus inazuma sp. n. has different coloration than Epizoanthus beriber sp. n., which is pale white. Epizoanthus inazuma sp. n. and Epizoanthus illoricatus can have the same external coloration (black), but the cnidomes of these two species are different; Epizoanthus illoricatus has large holotrichs in the column, pharynx and mesenterial filaments, while Epizoanthus inazuma sp. n. does not have any large holotrichs in the column, pharynx, or mesenterial filaments. As well, there are also differences in sizes of some nematocyst types of these two species (e.g. bastrichs in the pharynx or mesenterial filaments). The cnidome composition of Epizoanthus inazuma sp. n. is different from Epizoanthus beriber sp. n. and Epizoanthus illoricatus , and Epizoanthus beriber 's sp. n. cnidome is similar to that of Epizoanthus illoricatus (see Table 1; Figure 3).

All Indo-Pacific Epizoanthus species that are obligate epibionts on eunicid worm tubes until now have been identified as Epizoanthus illoricatus , which was originally described from Manila, the Philippines. The type specimens of Epizoanthus illoricatus were likely lost during World War II when the Zoologische Staatssammlung Museum in München was burned down. Additionally, no specific type locality was given except ‘Manila’ in the original description and Manila is now a very altered environment compared to 1930. Therefore, it is difficult to find and identify Epizoanthus illoricatus ' exact type locality. However, Epizoanthus illoricatus can be clearly separated from Epizoanthus inazuma sp. n. and Epizoanthus beriber sp. n. by both morphological and molecular data.