“Those who dwell among the beauties and mysteries of the earth are never alone or weary of life.” –Rachel Carson, The Sense of Wonder (1965)

Per usual, the words of trailblazing conservationist and marine biologist Rachel Carson are timelessly applicable. In the quote above, as excerpted from her award-winning composition The Sense of Wonder, Carson emphasizes the values rooted in straying away from what is familiar, and instead pursuing the unknown within the natural world. Such a reflection analogizes the current conservation crisis of under-studied species such as the stalked jellyfishes, due to their inconspicuous identities. As a relatively obscure group in the world of science (until recently), stalked jellyfish populations have been inadvertently excluded from most conservation efforts, as their existence is often overlooked.

The stauromedusa Craterolophus convolvulus, nestled among the algae, by David Fenwick Senior

Belonging to the class Staurozoa, stalked jellyfishes are members of the Cnidaria phylum, specifically residing under the order Stauromedusae. Early in their taxonomic history, stalked jellyfishes caused some confusion as they were first misclassified as relatives of sea cucumbers, only to later be inaccurately associated with sea anemones (possibly because both organisms live attached to the seafloor). The absence of a medusa stage, in addition to the stalked jellyfish’s favored fixed orientation, provoked major deliberation as to its relationship to other cnidarians with free-swimming tendencies.

Using an adhesive basal disc as a holdfast to latch themselves onto boulders and rocky substrates, as well as onto sea grasses and aquatic plants alike, stalked jellyfishes usually inhabit rock pools and shallow tidal zones with environmental conditions that accommodate their sticky situation! Because species of stalked jellyfish maintain a lifelong sessile position, it is vital that the ecosystem in which they are affixed allows for adequate water circulation to regularly propel food sources into the jellyfishes’ reach. Equipped with nematocysts (stinging cells) stored within the cnidocytes of the tentacles located atop each of their eight “arms”, stalked jellyfishes fire these toxic darts to impair their prey, allowing them time to capture the stunned organism with their tentacles.

Lucernaria sainthilairei on the rocks, by Alexander Semenov.

Despite the information collected thus far regarding the behavioral tendencies, anatomical structures, and ecological roles of stalked jellyfishes, the species still remain relatively unexplored. Yet in recent years, scientists have been working in a race against time to properly research individual species, providing scientific names and descriptions of “new” species (they aren’t really new, just new to science!) that lack a proper identity, prior to and in prevention of their untimely extinction. In fact, bringing these poorly known species into the scientific spotlight may be key to their conservation in an ever-changing environment under the pressures of human activities. Without exposure to the attention elicited by extensive research efforts, many species reside in an out of sight, out of mind void where no conservation efforts are made to protect them, solely due to their unsung status. In fact, no species of stalked jellyfish has ever been evaluated to determine if it is threatened or endangered [but see the exciting efforts being made by Stauromedusae UK].

While most stauromedusae are found in cold waters, a few such as this Calvadosia sp. are found in tropical waters. This animal was documented as part of the Moorea Biocode Project in French Polynesia.

As for knowledge about stalked jellyfish biodiversity, Dr. Lucília S. Miranda from the University of São Paulo in Brazil, has made monumental contributions and revisions to the pre-existing understanding of the species in a set of newly published papers. With help from her collaborators, whom she accredits for “assisting [her] with data collections, enriching [her] discussions, and moving [her] forward in [her] research”, Lucília discusses the stalked jellyfish’s nomenclatural history, while underscoring an overall need for further analysis and documentation of all things Stauromedusae. Initially compelled by the cnidarian life cycle, Lucília chose to further delve into staurozon biology through an extensive study of stalked jellyfishes for her PhD (part of which was spent as a visiting researcher in the NMNH Department of Invertebrate Zoology), in which she progressively developed interests in areas including the systematics, evolution, and macroecology (the study of the relationships between organisms and their environments) of stalked jellies. With a scarce selection of background information available, the ambiguous nature of such an under-studied species posed obstacles in her research at times, yet Lucília remains grateful for the challenges presented in her work.

Manania uchidai from Hokkaido Japan.

Some of the earliest records of Stauromedusae research (even dating back to more than 100 years ago) contain anecdotal reports of stalked jellyfish populations disappearing from where they were once abundant, possibly due to pollution. Despite such speculations, stalked jellyfishes have never been studied well enough to fully determine how sensitive they are to pollution or other environmental changes, putting them into a precarious position. Who would have thought that simply living off the grid could potentially be so detrimental to a group of species? However, because every species fulfills a unique role in their surrounding ecosystems, identifying anonymous organisms and extracting further information through research initiatives are fundamental steps in piecing together an ultimate understanding of how Earth’s systems sustain life.

By Meredith Kucik, NMNH Intern

Further Reading

Miranda LS, Mills CE, Hirano YM, Collins AG, & AC Marques. 2017. A review of the global diversity and natural history of stalked jellyfishes (Cnidaria, Staurozoa). Marine Biodiversity. doi:10.1007/s12526-017-0721-4