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.
The collection of stauromedusae is not generally regarded as necessary, as most specimens can be identified in-situ without their removal, and with increasing confidence as more experience is gained.
Digital cameras, with good macro capability, can usually be successfully used in the field, and by using a cameras PLAYBACK facility, determination being gained by zooming in on characteristics seen in the images that are taken. Any determination may also be made easier by carrying a set of printed images, or illustrative guide. Technology may also be used, digital images of previously confirmed species, or guides, may be stored on the memory card of a digital camera, smart phone or other mobile device, as a point of reference.
See Photographing stauromedusae.
With many species being quite different, (click link to see a larger illustration showing the most frequently seen species in Cornwall), different even to the naked eye, once some experience of the group has been gained, the only time one might have to consider the collection or removal of a specimen is to determine species that may be morphologically similar. e.g. Haliclystus octoradiatus and Haliclystus auricula, in determining Haliclystus octoradiatus if a specimen possesses few white nematocysts; or in determining very small juvenile stauromedusae. Stauromedusae found attached to rock, such as Depastrum cyathiforme, should only be removed if collecting for DNA testing, detailed study or preservation. There is currently a need to collect this species for study, for DNA testing, anatomical photography and in gaining better detailed descriptions of the microscopic characteristics of this species, e-mail for details.
Photography as an identification tool is less useful where specimens are surrounded by algae, situated too deep in an intertidal pool, in areas of locally strong currents, poor visibility, bad weather conditions, especially windy weather, or at wave prone locations. Where and when photography cannot be used, the collection of a specimen/s may be necessary to determine species that are present, e.g. in surveying MCZs or proposed MCZs (Marine Conservation Zones).
I cannot discuss Haliclystus auricula here because it appears to be either very rare, periodic or not present in my region. I can however report my findings that relate to the removal and relocation of a similar species, Haliclystus octoradiatus, which is frequently found around Cornwall. It is a species of which more people are becoming aware, being transferred from H. auricula in 1979.
I have found, through the intertidal surveys I've conducted, that specimens found around Cornwall are far more likely to be H. octoradiatus than H. auricula, which I haven't yet found, despite closely studying hundreds of individuals of Haliclystus. Continued study is needed to find where H. auricula may occur as its current status around the UK is unknown. It is crucial that funding is provided to address this issue, with potential sites surveyed for this species "at the right time of the year".
The following sections describe how stauromedusae may be best removed from the medium on which they occur, and best relocated after study and / or photography.
Removal
1/ Remove specimen by cutting away the piece of algae or Eelgrass, or part of it, on which the specimen is found.
2/ Carefully cut, with scissors, sharp knife or scalpel, 5mm either side of the specimen. Holding the medium on which the specimen is attached to transfer it, so as to avoid any damage to the specimen.
3/ Place the specimen for study in a "clear plastic container of fresh, clean (clear) seawater"; small tubes should not be used as the removal of specimens from them is very difficult. Please note, the seawater in the container must be the same temperature as the seawater the specimen was collected from to avoid shocking the specimen.
4/ Allow the specimen to cling to the side of the plastic container by its tentacles, or promote this by offering the side of the container to the specimen.
5/ Once the specimen has attached to the plastic, the small 10mm piece of algae or Eelgrass, on the end of the stalk can, after a little time, be more easily removed, and by using a pair of tweezers. In practice what tends to happen is once the specimen is attached to the plastic, the 10mm piece of algae or Eelgrass, will be released by the specimen.
6/ The specimen can then be better studied or photographed. Care needs to be taken in the summer as small amounts of seawater in containers can heat up quite quickly, and this will decrease the amount time one has to study specimen/s, and affect how they are released. For instance, it may be necessary to gradually lower the temeperature of the seawater in the container by placing it in a rockpool, or cool bag, and until the seawater in the container is of equal temperature to the seawater at the site of relocation.
Relocation
1/ It is probably best practice to relocate specimen/s where they were found, or as near as possible, and onto the same species of algae, again if possible. However, point five below should be considered, for re-attachment is probably best carried out where there is some water flow, and this may not be possible where the species was originally found.
2/ Where attachment to the same algal species is not possible specimens may be attached to Eelgrass, Zostera marina; Sargassum muticum stalks or Chondrus crispus. The named species of algae mentioned are probably best regarded as 'universal recipients', as they are species on which many species of stauromedusae that are found on the shore are commonly found.
3/ Where it isn't possible to return the specimen to where it was found, it is best to replace at the narrow end of a pool where pools drain into one another. Places such as these tend to be
where stauromedusae may congregate to feed, because of local currents and water flow.
4/ As already mentioned, on replacing specimen/s to algae or eelgrass, seawater temperature in the container has to be the same as surrounding water temperature as to avoid shocking the specimen.
5/ Importantly, seawater in which a specimen is being returned is best having some "flow". Flowing water seems to stimulate stauromedusae and give them a purpose to cling on to algae, or Eelgrass, to which specimen/s are being transferred. It appears to be harder to transfer a specimen successfully where there is no flow at all, much of the time specimens will just sink to the floor of the pool without attaching and when they do attach the grip of the basal disk may be poorer because of a lack of stimuli.
The method here was worked out in a small aquarium where the flow or water was able to be controlled, the flow was achieved by switching on a bio-pump / filtration system. Stauromedusae appeared to cling less successfully in still water. Basal disc attachment was more quickly achieved when the filtration pump was turned on and water allowed to circulate freely around the tank. This is all based on general observation, no measurements were taken. The species used and studied was Haliclystus octoradiatus, attachment was to the algae, Cladostephus spongiosus, a brown algae, on which juvenile Haliclystus octoradiatus are frequently found.
How specimens are returned / relocated is very important, as specimens collected must be given time to gain the best possible grip on the medium on which they are being returned, and before the tide reaches the area of collection. There is an obvious risk that if the stauromedusae isn't given enough time for its basal disk to attach sufficiently well, then it may be washed away. Returning specimens to algae in slightly flowing water, either where they were collected or near to where they were collected would seem to be beneficial to both specimens, and the collector, and in terms of shortening the time spent ensuring successfully transfer.
Haliclystus octoradiatus is one of the easiest species to collect and relocate; however, the species Calvadosia cruxmelitensis is one of the hardest. Fortunately the latter species is quite distinct from other species of stauromedusae, so identification can often be achieved visually and with the specimen in-situ. The only species it can be confused with is the related species Calvadosia campanulata, but once the differences are understood they are easy to tell apart, although small juvenile specimens are potentially a lot more difficult to identify and a microscope may be needed to observe them.
See Species accounts.
The basal disk of Calvadosia cruxmelitensis has been found to be quite powerful, so powerful, that specimens will often tear apart rather than self-release, if care is not taken to remove them, and if the methods described above are not used. On collecting a specimen of this species, the above points need to be followed, but I have found that the grip of the basal disk on the medium that they are found, may be further reduced by applying light, e.g. light from a reasonably powerful head torch. This species also appears to readily cling to plastic and this in turn may help with the removal of the short strip of algae or Eelgrass.
I would be interested in hearing from anyone who has found stauromedusae on plastic; e.g. on plastic boards used in ports, marinas etc., during surveys for aliens species.
Specimens of Calvadosia cruxmelitensis may be transferred as described above, the best algae for transfer are Chondrus crispus and Corallina officinalis, and Eelgrass, Zostera marina, where specimen/s have been found on it. Calvadosia cruxmelitensis is found quite frequently on Eelgrass in Mounts Bay (Fenwick, 2013), but is rarely found on Eelgrass in South Devon (Corbin, 1978). Getting Calvadosia cruxmelitensis to re-attach can be extremely difficult, which is why I do not recommend its removal for the sole purpose of identification or photography. It is a BAP species, and quite locally distributed, so the species and the habitat where it occurs should be treated with some respect.
Collection of specimens for molecular analysis
Collection of specimens for DNA analysis is done using 99% ethanol. If small 2mml tubes are used for collection it is best to remove excess seawater from a specimen to prevent dilution of the alcohol. It is always best to take as detailed photographs as is possible, of the specimen in seawater, at various angles, before its preservation. Colour is lost from specimens on placing them in alcohol.
