(Solander in Lightfoot, 1786)
Tropical Indo-West Pacific
Sokodo, Hachijo Island, Japan, 8m, 50mm & 30mm long. 1 July, 2001. Photo: Nishina Masayoshi.
Shell identical in shape to that of Hydatina physis. In H. zonata the colour pattern consists of thin, rather irregular brown lines running across the translucent white shell, essentially parallel to the outer lip of the shell. There are spiral bands around the base and apex of the shell where the brown lines are absent, and sometimes another spiral band simewhere between the base and the apex. These colourless bands are sometimes bordered with a thin brown line. Like H. physis, the animal varies in colour from translucent white with an opaque white margin, as illustrated here, to a deep brownish pink. Anatomically it is identical to H. physis.
Major synonyms include Bulla circulata Martyn, Bulla velum Gmelin, Hydatina vexillum Sowerby.
• Lightfoot, J., (1786). A Catalogue of the Portland Museum lately the property of the Dowager Duchess of Portland, Deceased: which will be sold by Auction. 194pp, Plate 1. London.
Rudman, W.B., 2001 (August 8) Hydatina zonata (Solander in Lightfoot, 1786). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/hydazona
December 12, 2005
From: Dong Bum Koh
Here are some photos of Hydatina zonata from South Korea.
Locality: Hwa Soon. Jeju island, South Korea. Depth: 3 m. Shell length: 18 mm. 09 Dec 2005. Sandy bottom. Photographer: Dong Jin Jwa
From Dong Bum, Koh
email@example.comD. B. Koh, 2005 (Dec 12) Hydatina zonata from Korea. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15449
It's nice to get some more photos of H. zonata. This animal which lacks the clear spiral bands usually seen in this species are a useful addition to our understanding of variability in this species. In fact you can see traces of dark spiral bands on the shell formed from thickening of parts of the black axial lines on the shell.
February 10, 2004
From: Debby Lange
Dear Dr Rudman,
I have found Hydatina albocincta in Merimbula Lake [New South Wales, Australia] a few times as an adult. On the 25th Jan, 2004, we found 2 along with 15 Hydatina physis. I have attached 2 photos of each of the above with eggs. Is Hydatina albocincta documented as being found here? Also, the Hydatina physis
that we found with eggs was a darker colour than the ones we found without eggs. Is this usual? (the photos show the true colours.)
[and the Sapphire Coast Marine Society]
firstname.lastname@example.orgLange, D., 2004 (Feb 10) Hydatina zonata in Merimbula, NSW. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12151
Thanks for these photos. As you'll see in a separate message [#12170] I consider Hydatina albocincta to be a synonym of the older Hydatina zonata. The shell is quite variable in colour pattern. Your photos are useful because they help illustrate how variable both H. zonata and H. physis are in colour of the animal has well, both species ranging from a pale almost colourless translucent white to a deep red. I wouldn't know if colour change is related to egg production but large animals of both species show quite a lot of colour variation so its unlikely. But it's something you could look at with the more plentiful H. physis.
Hydatina zonata is essentially a tropical species, but when conditions are favourable larvae can sometimes settle anywhere down the New South Wales coast. Wherever it is found, it does not seem to be as common as H. physis.
February 10, 2004
From: Bill Rudman
PHOTO: Drawings from Pilsbry, 1893. 7. Bulla velum Gmelin, 1791 [Pilsbry Pl.44, f. 7]. 29. Hydatina albocincta van der Hoeven, 1839 [Pilsbry Pl. 45, f. 29].
In an earlier message I suggested that many species of Hydatina seemed to be just shell colour forms of one species, Hydatina zonata. With Debbie Lange's photos of Hydatina physis and Hydatina zonata together I think it appropriate to share some unpublished notes I have on the question. Her photo of H. zonata and earlier photos of Nishina Masayoshi's from Japan [see #4976] illustrate the 3 main colour variants.
Hydatina zonata (Lightfoot, 1786)
Bulla amplustre Born, 1780: 204, Pl.9, fig.1 (NOT B. amplustre Linnaeus, 1758).
Bulla zonata Lightfoot, 1786: 164.
Bulla velum Gmelin, 1791: 3433.
Bulla cinctoria Perry, 1811: Pl.40, fig.1.
Hydatina albo-cinctum van der Hoeven, 1839: 246, Pl.10.
Amplustrum velum: Bergh, 1901a: 242-6, Pl.20, figs 45-50, Pl.21, figs 1-10., Vayssiere, 1906: 29-33, Figs 52-5.
Aplustrum albo-cinctum: Bergh, 1901a: 251-2., 1901b: Pl.22, figs 18-23.
Hydatina (Amplustrum) velum: Eales, 1938: 79-80, Fig.1, Pl.1, fig.8.
Hydatina (Hydatoria) zonata: Habe, 1950a: 18, Pl.3, fig.6.
Hydatina (Hydatoria) albocincta: Habe, 1950a: 17-18, Pl.3, fig.7.
Hydatina cinctoria: Rudman, 1972b: 136-7, Pl.1D, E.
Amplustrum amplustre: Catala, 1979: 105, Fig.75 (NOT Bulla amplustre Linnaeus, 1758).
While Hydatina physis is characterised by many thin brown spiral lines colouring the shell, there are a number of names which apply to Hydatina shells in which brown axial lines predominate. Usually the brown lines are split into a series of spiral zones by white spiral bnads. In one form, (`H. cinctoria'), the brown zones are separated by five white bands, while in `H. velum' there is an upper, a lower, and a thin median white band, each of which is outlined with a thin dark brown line. The rest of the shell has pale brown pigmentation. These colour combinations and a gradation of intermediate patterns have been given specific names which are listed above. No anatomical differences have been observed and the colour and shape of the animal varies from a pale translucent almost white form to a dark pinkish brown edged with white. I suspect all these forms are one species.
Bill RudmanRudman, W.B., 2004 (Feb 10) How many species of Hydatina are there?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12170
August 13, 2001
From: Nishina Masayoshi
I also wonder, as you do in your discussion, whether these three species are just colour forms of one species. They are similar to each other. Hydatina physis is common at Hachijo. Though there are so many H. physis, I've never seen H. zonata and H. physis together at the same place. I will ask this question to S. Kato of Reglus Diving to make it sure.
I've never seen Hydatina cinctoria before at Hachijo.
email@example.comNishina, M., 2001 (Aug 13) Re: Hydatina zonata from Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/5057
August 10, 2001
From: Nishina Masayoshi
Hydatina zonata is common in Hachijo, but it is a seasonal animal, usually found between June and October. I temporarily dug them from the sand and moved them to the rock so I could photograph them.
Date: 1 July, 2001
Place: Sokodo, Hachijo Island, Japan
Size: 50mm & 30mm
firstname.lastname@example.orgNishina, M, 2001 (Aug 10) Hydatina zonata from Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4976
Thanks for these beautiful photographs. Do you ever find Hydatina physis or Hydatina cinctoria (= Hydatina albocincta) with H. zonata? Hydatina cinctoria is the one with broad brown spiral bands on the shell. I sometimes wonder whether these three species are just colour forms of one species