STAUROMEDUSAE UK
An online guide to the Stalked jellyfish (Stauromedusae) found
around the coastal waters of the United Kingdom and Ireland.
Includes notes on their identification, and where and how to find them.
There appears to be only four previous accounts of twin-headed specimens of stauromedusae being found, although with further reading and promotion this abnormality, more may be discovered. The term 'twin-headed' here, includes twin-headed specimens where each bell is of equal size, and also where one of the bells appears to be less developed.
On researching this subject in English texts, and texts that have been translated into English, there are only multiple reports of twin-headed specimens from just one species, Depastrum cyathiforme. Twin-headed specimens so far being reported globally in four species, Depastrum cyathiforme, Calvadosia campanulata, Calvadosia cruxmelitensis and Haliclystus antarcticus. Two twin-headed specimens mentioned here were described as "budding" in literature; one head was described as being, or was likely to have been smaller than the other. Another account reports " two individuals growing from a single basal disc". The abnormality described here may possibly be found widely throughout the stauromedusae. It has been found to occur in the sub-order Eleutherocarpida, in the genus Lucernariopsis of the family Kishinouyeidae, and in Haliclystus of the family Lucernariidae. If the record of Depastrum cyathiforme is considered, the abnormality also occurs in the sub-order Cleistocarpida, and in the family Depastridae.
The first report of twin-headed stauromedusae was by a Professor Allman; who produced an early article about a species, we now know as Depastrum cyathiforme. Prof. Allman, F.R.S., writing 'On the Structure of Carduella cyathiformis' in the Quarterly Journal of Microscopical Science No. XXXI, April 1860; states on page p. 126. "It was a very frequent thing to meet with two individuals growing from a single basal disc; but this I believe to be a case of simple fusion from contiguity, and not an example of gemmation or other form of zooidal multiplication". Professor Allman and Mr. Gilchrist found these specimens at the town of Stromness, Orkney Islands, in August 1859; they were "attached to stones near low water mark, in the neighbourhood of that town."
Coincidentially, the second report of a twin-headed stauromedusae appears to be for a specimen of Depastrum cyathiforme also, a specimen was found at Rame Head, South East Cornwall, UK; during May of 1893. In the literature it is stated that "specimen exhibited a distinct lateral bud". Ref: Journal of the Marine Biological Association. Ref: Faunistic Notes at Plymouth during 1893-4. By Walter Garstang, M.A.. JMBA Vol. III. p. 216.
The third report of a twin-headed specimen appears to be much clearer, and was by N. Kassianow, with the species Calvadosia campanulata. Kassianow found a specimen of Calvadosia campanulata in the Bay of Saint-Vaast, Saint-Vaast-la-Hougue, Basse-Normandie, France (Pre. 1901). Kassianow reports on this specimen in a paper entitled "Studien über das Nervensystem der Lucernariden, nebst sonstigen histologischen Beobachtungen über diese Gruppe", which appeared in the publication "Zeitschrift für Wissenschaftliche Zoologie bd.69. p. 370. 1901" (click for text). The section is entitled "4. Über Knospungserscheinungen bei den Lucernariden", which loosely translates to "Budding phenomena of Lucernaria".
"Budding" in a historically context may have been seen as a method of asexual reproduction. Here "budding" in terms of twin-heading, is seen as an a morphological abnormality, consistent with a species morphological variability, and in opposition to the development of an appendage that may split from an individual forming a clone.
I reported the find of a twin-headed Calvadosia cruxmelitensis on the 16th April 2014, from Marazion, Cornwall, England; on social media, on Facebook's group entitled "NE Atlantic Cnidaria". A member of the group, and stauromedusae expert Allen Collins, came forward and informed me that morphological abnormalities were observed in a population of the stauromedusa Haliclystus auricula, in southern Chile. Ref: Zagal, CJ, ‘Morphological abnormalities in the stauromedusa Haliclystus auricula (Cnidaria) and their possible causes’, Journal of the Marine Biological Association of the UK, 88 (2) pp. 259-262. ISSN 0025-3154 (2008). It appears the species described in the paper is now considered to be Haliclystus antarcticus. It was reported by Dr. Carolina Zagal, that a total of 144 abnormal specimens was observed out of 3790 stauromedusae sampled, and that one twin-like individual was recorded for the first time in this species.
After being informed of Dr. Carolina J. Zagal's paper, I decided to look further into Calvadosia cruxmelitensis, as the species has been extensively studied in Devon and Cornwall by P.G. Corbin. Corbin studied stauromedusae at sites around Devon and Cornwall, including Plymouth, for over 20 years. Corbin also authored the species Lucernariopsis cruxmelitensis in 1978; producing a detailed account of the species and notes on its seasonal occurrence, the latter for the period of time described above. Corbin reports finding many thousands of Lucernariopsis cruxmelitensis, and reports finding 2000 at a single time. However despite this, there are no reports of twin-headed specimens being found, in either of Corbin's papers, despite Corbin describing the morphology of the species concerned. Ref: "A new species of the genus Lucernariopsis (Colenterata: Scyphomedusae)", Journal of the Marine Biological Association U.K. (1978) 58, 285-290; and with reference to "The Seasonal Abundance of four species of Stauromedusae (Colenterata: Scyphomedusae) at Plymouth". Journal of the Marine Biological Association. (1979) 59, p. 385-391.
It was after re-reading Corbin's work with Calvadosia cruxmelitensis, that I accidentally discovered the specimen of Calvadosia campanulata described by Kassianow. It was only on reading this article, in terms of the mention of "budding", that I realized the relevance of the record of Depastrum cyathiforme from Rame Head, Cornwall. The five accounts / records giving me purpose to write something about and promote this abnormality.
To conclude, twin-headed specimens are likely to be found either infrequently or very rarely indeed in some species; being reported to occur in approximately 1 in 4000 individuals by Zagal. The likelihood of finding them may increase where stauromedusae occur in greater numbers, however the proportions of this abnormality in each of the species described is not known, although it may occur more frequently in the species Depastrum cyathiforme, as is reported here.
It is likely that twin-headed specimens occur in more species than is listed here. One would expect it likely for such abnormalities to occur more in commoner species, or more frequently in intertidal species, where there is possibly an increase in the recording of stauromedusae, but this does not appear to be the case.
To update this article I have to report that potentially the first twin-headed specimen of the species Haliclystus octoradiatus has been found, and during the stauromedusae and turbidity monitoring of Penzance Harbour by ECOSPAN ENVIRONMENTAL LTD. 06.01.15. Images below.
Digital images of twin-headed specimens
Calvadosia cruxmelitensis twin-headed variant found at Marazion, Penzance, Cornwall. 16.04.14. A female specimen of 8mm oral diameter, producing eggs on collection. (Click on image links to view larger images).
Calvadosia cruxmelitensis - twin-headed variant 1
Calvadosia cruxmelitensis - twin-headed with eggs 1
L. cruxmelitensis - orally measured with 0.1mm rule 1
L. cruxmelitensis - laterally measured with 0.1mm rule 1
Calvadosia cruxmelitensis - eggs on slide 1
Calvadosia cruxmelitensis - eggs on slide 2
Calvadosia cruxmelitensis - eggs on slide 3
Calvadosia cruxmelitensis - eggs on black perspex 1
Haliclystus octoradiatus twin-headed variant found at Albert Pier reef, Penzance, Cornwall, 06.01.15, by Greg Lingard of ECOSPAN ENVIRONMENTAL LTD. (Click on image links to view larger images).
Haliclystus octoradiatus - twin-headed variant 1
Haliclystus octoradiatus - twin-headed variant 2
Article produced by David Fenwick on the 27th April 2014, for Stauromedusae UK. (Updated 07.01.15)
References cites:
Allman, Prof. G.. "On the Structure of Carduella cyathiformis'. Quarterly Journal of Microscopical Science. No. XXXI, April 1860. p. 126.
Corbin, P.G.. "A new species of the genus Lucernariopsis (Colenterata: Scyphomedusae)", Journal of the Marine Biological Association (UK). 1978. 58. p.285-290.
Corbin, P.G.. "The Seasonal Abundance of four species of Stauromedusae (Colenterata: Scyphomedusae) at Plymouth". Journal of the Marine Biological Association (UK). 1979. 59. p.385-391.
Garstang, Walter. "Faunistic Notes at Plymouth during 1893-4". Journal of the Marine Biological Association (UK). JMBA Vol. III. p. 216.
Kassianow, N.. "Studien über das Nervensystem der Lucernariden, nebst sonstigen histologischen Beobachtungen über diese Gruppe", Zeitschrift für Wissenschaftliche Zoologie. (4. Über Knospungserscheinungen bei den Lucernariden). Bd.69. p.370. 1901.
Zagal, Dr. C.J.. "Morphological abnormalities in the stauromedusa Haliclystus auricula (Cnidaria) and their possible causes". Journal of the Marine Biological Association (UK). 88 (2) pp. 259-262. ISSN 0025-3154 (2008).
