Tears of the gods in a tube!

Anemones are among the most colourful and beautiful marine invertebrates ̶ their cousins, the tube anemones, are equally as spectacular but less well known. A recent study of AMRI collections has led to a revision of records from the southwest Pacific and the recognition of a new species.

In Greek, the word anemone refers to a particular type of wildflower and translates to “windflower.” Legend has it that these flowers grew from the tears of Aphrodite, the Goddess of love and beauty, who shed them when her lover Adonis was slain. These delicate flowers are steeped in symbolism with different meanings attributed to different colours. For instance, red flowers indicate death or forsaken love, epitomising having been stained with the blood of Adonis.

A group of marine invertebrates are also known as anemones, being named after these flowers for their beautiful and colourful appearance. Scientifically, these sea anemones are classified in the same phylum as other organisms that have specialised cells for capturing prey, the Cnidaria, which includes corals and jellyfish.

Most marine anemones are placed in the class Anthozoa, order Actinaria. Usually these are individual sac-like organisms with a soft, columnar, trunk-like body that can attach to surfaces by their base. This is topped by a ring of tentacles around a mouth, these can be extended and retracted to capture food using stinging cells. However, there are a number of related groups of Cnidaria that share some similarities and differences, one of these is the tube anemones (subclass Ceriantharia).

Tube anemones live individually and are characterised by tough cylinders which they inhabit and can withdraw into. They construct these from secreted mucus interwoven with unique filaments of discharged stinging cells (ptychocysts). The body is capped by a tentacular crown which they can extend out of their tubes and this is formed by two rings of different sizes. The outer tentacles are largest, and are generally used for prey capture and defence, while the inner tentacles are used for finer-scale food handling and intake. Tubes are generally partially buried and can extend considerable distances into soft sediments. However, there are some larvae that occur in the water column and have an in-built gas bubble that allows then to float and hang upside-down at the water surface.

Ceriantharids (name derived from the most famous genus of the group, Cerianthus, which means wax flower) have been studied and scientifically named since 1784. They can be locally abundant and quite large (over 14cm). However, their secretive nature, combined with difficulty in collecting them because of their ability to retract into their tubes, means they have not been well studied. Globally only just over 50 species have been recorded but many more are known to occur. They are often the subject of photographic records as the tentacular crowns are spectacular when out and are a favourite for divers to spot, they are also commercially sold for the aquarium hobby industry. Additionally, they are long lived and excellent indicators of environmental conditions, as well as informative regarding biogeographical and evolutionary relationships.

Recently the tube anemones in the Australian Museum Research Institute (AMRI) collections were examined by Dr Sérgio Stampar, a visiting expert, as part of a broader study. This led to the discovery of a new species from just south of Sydney, in Botany Bay, which has recently been described, along with some additional species from New Zealand and Antarctica. A revision of species known from Sydney Harbour and Queensland was also included in the publication. The species from Botany Bay was collected as part of environmental surveys undertaken by the Australian Museum in the 1990’s and appears to be restricted to that area as comparative sampling undertaken at the time, nearby in Pittwater, did not locate it. Apart from another species described from New Zealand, in the same publication, the closest relatives are otherwise known from the Atlantic Ocean.

Clearly there is still much to learn about, and from, these enigmatic and beautiful animals. Equally apparent is that collections accumulated by organisations such as AMRI have a vital role to play in this.

Dr Stephen Keable, Collection Manager, Marine Invertebrates, Australian Museum Research Institute.

Dr Sérgio Stampar, Associate Professor, São Paulo State University UNESP, Brazil.