Hydrozoanthus gracilis (Lwowsky, 1913) sensu Di Camillo et al. (2010)

Reimer, James D., Poliseno, Angelo & Hoeksema, Bert W., 2014, Shallow-water zoantharians (Cnidaria, Hexacorallia) from the Central Indo-Pacific, ZooKeys 444, pp. 1-57: 14

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Hydrozoanthus gracilis (Lwowsky, 1913) sensu Di Camillo et al. (2010)


Taxon classification Animalia Zoantharia Hydrozoanthidae

13. Hydrozoanthus gracilis (Lwowsky, 1913) sensu Di Camillo et al. (2010)   Figures 12A, B, 13

Specimens examined

(n=3). RMNH Coel 40692, Snellius–II Expedition station 4.098, East Komodo, Komodo (08°29'54"S, 119°38'06"E), depth = 75 m, collected on September 19, 1984 by rectangular dredge; RMNH Coel. 40518, Snellius–II Expedition station 4.022, north Pulau Mai, Maisel Islands, Banda Sea (05°29'S, 127°32'E), depth = 0 to 1.5 m, collected on September 7, 1984; RMNH Coel 3816, Snellius Expedition, Sipankat Island, near Siburu Island, Sulu Islands, Philippines, collected on September 10-14, 1929.

Photographic records

(n=5). Southwest Nusa Penida, eastern Bali (08°49'S, 115°34"E), May 25, 1998; Desa Ped, Nusa Penida, Lombok Strait, east Bali (08°40'28"S, 115°30'50"E), May 25, 1998; east Tanjung Taal, Nusa Lembongan, Lombok Strait, east Bali (08°39'33"S, 115°26'37"E), May 24, 1998; Fauna Malesiana Maluku Expedition station MAL.21, west of Lilibooi, north coast Ambon Bay, Ambon, Moluccas (03°44'S, 128°02'E), November 20, 1996; East Kalimantan Program station BER.16, northeast Pulau Maratua, East Kalimantan, Berau Islands (02°17'29"N, 118°35'29"E), October 10, 2003.


As originally and previously described ( Di Camillo et al. 2010), this azooxanthellate, colonial species is found as an epibiont on hydrozoans, particularly Plumularia habereri   Stechow, 1909. In this study, this species consists of only one morphotype, with a gray to brown scapus, and reddish-brown oral disk and tentacles (Figure 12B). The appearance matches well with the morphotype of the species observed by Di Camillo et al. (2010).

In this study, measurements are only available for two specimens, with polyps averaging 2.4 mm in height and 2.1 mm in width. These data also fit well with Di Camillo et al. (2010), who mention polyp heights of 2-5 mm, widths of 1.6 to 3 mm, with 32 tentacles and mesenteries.


Regions recorded in this study (Figure 13). East Bali (5), Komodo Island (8), Maisel Islands (13), Moluccas (14), Berau Islands (19), Sulu Islands (20).

Previous records. Originally reported from Sagami Bay, Japan ( Lwowsky 1913), and subsequently reported from Taiwan ( Reimer et al. 2011c), New Caledonia ( Sinniger 2006), and Indonesia ( Sinniger et al. 2005, Di Camillo et al. 2010). It appears this species has an Indo-West Pacific distribution.


This morphotype differs from the other known morphotype of the species (sensu Carlgren 1934) associated with this binomen, which is yellow in coloration. The original description of the species from Sagami Bay, Japan by Lwowsky (1913) was of a "gray, sandy" morphotype, but this was preserved in formalin, and thus could be either morphotype discussed here, or even a different one altogether. Phylogenetic analyses have shown subtle differences of sequences of specimens within this species ( Sinniger et al. 2008), indicating that taxonomic revision may be needed in the future for this species group.