Hayadan > Jellyfish under attack: Researchers have found parasitic sea lilies in jellyfish for the first time

Jellyfish under attack: Researchers have found parasitic sea lilies in jellyfish for the first time

Researchers have discovered for the first time the existence of parasitic planoles (sort of larvae) of the sea lily that grows in jellyfish in the Mediterranean Sea that allow the sea lily to spread beyond the immediate environment, a finding that may affect marine ecosystems in the region

Photo 4: The life cycle of the blooming sea lily Edwardsiella carnea. a. Mature male and female polyps release gametes into the water column. b. Free-swimming planula formed after fertilization. c. The planula infects the comb host Mnemiopsis leidyi and develops into a worm-like parasitic stage. d. Planula after the parasite stage exits the comb host to the water column (e), where it can either settle on the sea floor (f) and develop into a polyp (a) or infect another comb host or a scyphozoan host such as Rhopilema nomadica or Rhizostoma pulmo (hypothetical parasite spillover) (gh) . A planula after the parasite stage may leave the scyphozoan host and move through the water column (i), where it can settle on the sea floor (f) and develop into a polyp. The dashed line represents an alternative route.

Many marine creatures, such as sea anemones, have difficulty dispersing long distances across the ocean, especially when they do not have a long, mobile larval stage. Unlike their relatives in the class Cnidaria, sea anemones lack a jellyfish stage as part of their life cycle, which makes it difficult for them to spread. Their only mobile stage is a tiny preemie called a planula. In many species of sea anemones, the planula stage exists for only a short period of time, a few days, and then settles on the sea floor and becomes a polyp—a soft tube-like creature with a mouth in the center surrounded by hunting arms. This short window of time reduces the ability of sea anemones to colonize new areas far from their source population.

Some of the sea anemone species, such as the blooming sea anemoneEdwardsiella carnea , developed a unique strategy to deal with the challenges of distribution in the ocean. These anemones are parasites on marine gelatinous creatures called Maserkaniyat. The polyps of the blooming sea anemone release eggs and sperm cells into the water. The fertilized eggs develop into flavones, which can infect the worms by penetrating through their tissue or by ingestion. Inside the comb, the planules grow into a worm-like shape, and after a while they can break free from the comb, settle on the sea floor and develop into polyps. The combs can contain many parasites of these sea anemones, and carry them long distances across the ocean.

A new study led by Prof. Tamar Guy-Chaim from the Israel Sea and Lakes Research Institute (Khiel) and Ben-Gurion University and PhD student Anastasia Yakovleva, Dr. Arseni Morov from Prof. Guy-Chaim's laboratory in Khayel and Prof. Dror Angel from the University of Haifa, first discovered parasitic flavonols of The sea lily that blooms in jellyfish. In the study, conducted with funding from the National Science Foundation and published on Friday in the journalScientific Reports , phenols of Edwardsiella carnea were found in the Israeli Mediterranean in jellyfish of a species wandering thread וSmooth border blue, through morphological and genetic identification. These findings indicate "parasite spillage", an ecological phenomenon in which a parasite normally associated with one host species appears in new species.

Figure 1: General view of the scyphomedose hosts Rhizostoma pulmo (a) and Rhopilema nomadica (b), and the initial developmental stages of the parasitic planulae of Edwardsiella carnea (cg) found in them. c. Planula (black arrow) on the oral arm of R. nomadica. d. Planules (pl) with developing mesenteries (se) and vacuolar globules that resembled fat droplets (v). e. Spherical planula with a mouth (mo). The contents of the box are detailed in panel gf A worm-like planula with a recognizable mouth (mo) and an aboral end (ab). Box contents detailed in panel hg Highly polygonal epidermis (ci) of globular flavones. h. Highly ribbed epidermis (ci) of a worm-like planula. um – umbrella (bell), oa – mouth arms, tn – hunting arms. Scale bar: 1 mm (c), 300 μm (d, e, f), 25 μm (g, h). — Figure 1: General view of the scyphomedose hosts Rhizostoma pulmo (a) and Rhopilema nomadica (b), and the initial developmental stages of the parasitic planulae of Edwardsiella carnea (cg) found in them. c. Planula (black arrow) on the oral arm of R. nomadica. d. Planules (pl) with developing mesenteries (se) and vacuolar globules that resembled fat droplets (v). e. Spherical planula with a mouth (mo). The contents of the box are detailed in panel gf A worm-like planula with a recognizable mouth (mo) and an aboral end (ab). The contents of the box are detailed in panel hg Highly ribbed epidermis (ci) of globular flavones. h. Highly ribbed epidermis (ci) of worm-like planula. um – umbrella (bell), oa – mouth arms, tn – hunting arms. Scale: 1 mm (c), 300 μm (d, e, f), 25 μm (g, h).

This finding is particularly surprising, since most of the connections between parasites and hosts are maintained in an evolutionary way over time, that is, parasites tend to infect species with which they have evolved together in a process of mutual evolution (coevolution) over long periods. It is rare for a parasite to switch hosts from one species to a species from a completely different evolutionary group. The researchers suggest that the selection of the sea anemone spawning host is due to the seasonal availability of gelatinous zooplankton, such as jellyfish during seasonal jellyfish blooms, rather than a shared evolutionary history.

This study highlights how parasites can adapt to new hosts in rapidly changing marine ecosystems, such as the eastern Mediterranean exposed to rapid and extreme climate change. The consequences of this spillover of parasites could be significant, especially as jellyfish blooms have increased in recent decades in our regions. Further studies are now being planned to examine the wider effects of this parasitism on jellyfish populations, particularly on their reproduction and survival.

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