The comb jellies Bolinopsis and Mnemiopsis
I took this ‘one off’ shot of a clear jelly during my dive at Moonta Bay jetty in June 2017. While the photograph is enigmatic, my observations were sufficient for me to pursue a positive identification of the species. It turned out to be a comb jelly, and my interest in the animal was piqued and extended with help from the author of the books Stung! and Jellyfish: A Natural History, Dr Lisa-Ann Gershwin.
I posted the photo on the Facebook group I Friggin’ Love Jellyfish which she administers with the comment “Saw this clear ‘jelly’ yesterday at Moonta Bay jetty”. Before long, Lisa-ann confirmed the species ID and asked me about their abundance. She mentioned that this has been a species of concern for her in Spencer Gulf, South Australia for many years. She told the group:
“It occasionally blooms into ridiculous numbers, whereby it can eat pretty much every living thing in the water column. If you google “Mnemiopsis Black Sea”, you’ll see what I mean; Bolinopsis is a more prolific breeder and more voracious predator than Mnemiopsis.”
The people I was staying and diving with at Moonta Bay didn’t spot any Bolinopsis in the water, but fellow Marine Life Society member Dan Monceaux, who coincidentally had been snorkeling near Point Lowly for several days during the previous week, told me he had made some sightings. He said that he seen multiple individuals on every snorkeling dip, which included both day and night swims. He observed that the animals were sparsely distributed (no group sightings were made) appeared to be swimming within 1 metre of the sea surface, and were refracting and reflecting colourful flashes of light with their cilia plates, which they also use for locomotion.
Dan was able to capture a few sharp images of one of the individuals he encountered near Stony Point, in upper Spencer Gulf, though his priority subject was the aggregation of giant Australian cuttlefish which occurs there every winter.
Prompted by Lisa-ann’s comments, I looked up Mnemiopsis on Wikipedia which informed me that Mnemiopsis are a “tentaculate ctenophore (comb jelly), originally native to the western Atlantic coastal waters. . . . Mnemiopsis is a carnivore that consumes zooplankton including crustaceans, other comb jellies, and eggs and larvae of fish; it is sometimes known to eat smaller individuals of its own kind.”
It also stated that “three species have been named in the genus Mnemiopsis, but they are now believed to be different ecological forms of a single species M. leidyi by most zoologists”. Mnemiopsis leidyi is referred to as the warty comb jelly or sea walnut (because it moves so slowly) and it is also described as an invasive species.
The Global Invasive Species Database shows that Mnemiopsis was named among 100 of the “World’s Worst invaders” and can be found in estuarine and marine habitats. Further information from the website is reproduced below:
“The native habitat of the ctenophore Mnemiopsis, is in temperate to subtropical estuaries along the Atlantic coast of North and South America (Mayer,1912). M. leidyi is tolerant of a wide range of salinity, temperature and water quality conditions over a broad range of inshore habitats. Since its unintentional introduction to the Black Sea, Mnemiopsis has spread to adjacent bodies of water, inhabiting waters of salinities ranging from 3% in the Sea of Azov to 39‰ in the eastern Mediterranean, and temperatures ranging from 4oC in winter to 31oC in summer (Dumont and Shiganova).”
“Mnemiopsis ledyi is a major zooplankton predator and is associated with fishery crashes (Costello, 2001). A carnivorous predator on edible zooplankton (including meroplankton), pelagic fish eggs and larvae, M. leidyi causes negative impacts right through the foodchain of the areas it has invaded. In the Black Sea and the Sea of Azov, the zooplankton, ichthyoplankton and zooplanktivorous fish stocks all underwent profound changes.
The pelagic ecosystem of the Black Sea was degraded, manifesting as sharply decreased biodiversity, abundance, and biomass of the main components of the pelagic ecosystem-zooplankton (Dumont and Shiganova). Fish stocks in the Black Sea and Sea of Azov have suffered due to predation on eggs and larval stages of food supplies (Shiganova 2003). Effects on the ecosystem in the Caspian Sea were faster and stronger than in the Black Sea. In 2001, repercussions were felt at all trophic levels, including that of the top predator, the Caspian seal (Dumont and Shiganova).
A cascading effect occurred at the higher trophic levels, from a decrease in zooplankton stock and collapsing planktivorous fish, to vanishing predatory fish and dolphins. Similar effects occured at lower trophic levels: from a decrease in zooplankton stock to an increase in phytoplankton, which was released from zooplankton grazing pressure. The majority of these effects were top-down, but a few were also bottom-up. Similar effects, but less pronounced, were recorded in the Sea of Marmara. Effects on Mediterranean food webs have, so far, remained insignificant. Salinity is probably supraoptimal there, and several predators prevent M.leidyi from reaching outbreak levels.”
Back to Bolinopsis
To learn more about Bolinopsis, I visited Jellieszone.com which stated, “Careful attention is required to observe the almost totally transparent comb jelly, Bolinopsis. Although attaining lengths of up to 15 cm, it can still easily evade detection by the eyes of predators seeking a gelatinous meal. A pair of large oral lobes are held open to gather copepods, euphausids and other zooplankton. Prey are funnelled on to the mucous-covered lobes with the aid of ciliated structures known as auricles. Once captured, cilia transport the food to the mouth slit. Bolinopsis usually orients vertically and swims slowly up and down while gathering food. L
ike other comb jellies, the eight comb rows propel the animal. The only pigmentation on the body is in the form of rows of dark spots on the lobes. The delicate gelatinous tissue is easily damaged. This comb jelly is a favoured prey of the voracious ctenophore, Beroe. Bolinopsis is not particularly common in Monterey Bay (California), but may occasionally be seen in large aggregations during fall and winter months. It is more common in northern waters, and ranges from southern California to the Arctic. Bolinopsis is sometimes displayed at public aquariums featuring jellies. It does well in captivity when maintained in a kreisel and fed brine shrimp nauplii and wild zooplankton. A similar species, Mnemiopsis leidyi (bottom photo), native to the East Coast U.S., has become an invasive pest in the Mediterranean and Black Sea.”
The Atlas of Living Australia gave some further insights into the animal’s occurrence from an Australian perspective, with records of sightings or collected specimens logged off the coasts of Queensland, New South Wales and Western Australia. Dan Monceaux advised me that marine invertebrate records in the Atlas are often data deficient. For example, Lisa-ann’s historic observations of Bolinopsis in Spencer Gulf are yet to be reflected in the database. At the time of posting this article, the Atlas had no records of Bolinopsis in South Australian waters at all.
Since writing and extending this article, Dan and I have each submitted records of our Bolinopsis sightings to the Atlas of Living Australia and would encourage anyone else who encounters these voracious and hypnotising comb jellies in Australian waters to do the same.
Many thanks to co-author Dan Monceaux and to Dr Lisa-ann Gershwin for their assistance with this article.
Steve Reynolds is the current President of MLSSA and is a long-standing member of the Society. Steve is a keen diver, underwater explorer, photographer and is chief author of the Society's extensive back catalogue of newsletters and journals.