# Jelly blubber

Catostylus mosaicus is also known as the jelly blubber or blue blubber jellyfish. The jelly blubber is distinguishable by its color, which ranges from light blue to a dark blue or purple, and its large (250-300mm), rounded bell which pulses in a staccato rhythm. It occurs along the coastline of Eastern Australia in estuaries and shallow bays, and often blooms to high abundance.

## Taxonomy

Catostylus mosaicus is a member of the class Sycphozoa and order Rhizostomae, which distinguishes them as possessing eight oral arms instead of tentacles. There are thought to be two monophyletic clades of the Castolysus mosaicus found in Eastern Australia: C. mosaicus mosaicus and C. mosaicus conservitus. The two differ in mitochondrial DNA, color, dimension, and bell depth. C mosaicus mosaicus is found in New South Wales and southern Queensland, and can be distinguished due to their small or nonexistent papillae and larger bell diameter. C. mosaicus conservitus occupies the Bass Strait and can be distinguished by conspicuous papillae, blue or white color, and smaller bell.

## Morphology

Jellyfish in the Rhizostomae order such as the Catostylus mosaicus are distinguishible by their unique morphology, characterized by a lack of tentacles. Instead of these tentacles, their bodies are composed of four oral lobes and eight arms that attach at the center of the bell. The bell of the jelly blubber is spherical in shape, and its feeding structures make up a greater proportion of its body than in many other species of jellyfish. Because of their unique body shape, C. mosaicus are known to utilize jet propulsion, triggered by the contracting and relaxing patterns of their bell.
Located on the arms of the C. mosaicus are nematocysts, or stinging cells. Nematocysts are utilized for defense as well as to immobilize prey, and because they vary between species, are often used for identification. Different types of nematocysts are specialized to catch different types of prey, and may be a causal factor for the specialized diets seen in jellyfish Catolystus mosaicus have four different types of nematocysts (Oval Isorhizae, pear-shaped Isorhizae, Rhopaloids, and Birhopaloids), distributed in relatively high abundance, that allow them to capture prey and defend themselves.

## Habitat

Catostylus mosaicus is the most common large medusae along the coastline of Eastern Australia, and can be found along the Malay Peninsula. They inhabit estuaries, semi enclosed lagoons, and shallow bays, and can form large, dense blooms. C. mosaicus thrive in high salinity environments, and events of lowered salinity can inhibit planula settlement and impair feeding ability of medusae. Additionally, rapid changes in salinity can impair osmoregulation, causing the jellyfish to swell or shrink rapidly. As a result, C. mosaicus resides predominantly in higher salinity areas of estuaries. C. mosaicus additionally influences the estuaries in which they reside through recycling of inorganic nutrients, providing nutrition for primary producers. Due to lower amounts of symbiotic photosynthetic zooxanthellae, C. mosaicus is able to recycle higher amounts of inorganics than many other estuarine-dwelling Sychphozoa.

## Ecology

Castolysus mosaicus feeds primarily on zooplankton, specifically mollusc veligers, copepods, and copepod nauplii. They generally capture fewer gelatinous zooplankton, as well as later, more developed stages of fish larvae and crab megalopae, as these animals are better selected to evade capture. C. mosaicus can form large blooms in the regions it inhabits, which can both their competition as well as their zooplankton prey. These blooms can negatively impact zooplankton which are consumed at higher rates or forced to expend more energy to avoid capture, leading to limitations in feeding and survival. In addition, competition with C. mosaicus for food may lead to declines in populations for competitors such as fish. C. mosaicus populations are controlled by predation by sea turtles as well as jellyfish-eating fish, including tuna, butterfish, sunfish, and spiny dogfish

## Reproduction and life history

The life cycle of Castolysis moscaicus is similar to that of other members of the order Rhizostomae. These jelly blubbers alternate life stages between a sexually reproducing free-swimming medusae stage and an asexually reproducing benthic polyp stage. The polyp stage reproduces asexually, while the medusa stage of the C. mosaicus reproduces sexually. The medusae are gonochoristic, with a 1:1 ratio of female to male. After fertilization, the eggs of the C. mosaicus develop into elongated, pelagic planula larvae and settle to the benthos to develop into their polyp stage. The polyp reproduces asexually through strobilation which produces an Ephyra, a juvenile stage that matures into the medusa

## Symbiosis

Catostylus mosaicus are known to have a symbiotic relationship with photosynthetic algae. This algae lives within the host and uses the sun to produce energy for itself as well as its C. mosaicus host. This energy makes up a small proportion of the diet of the jellyfish, and C. mosaicus is known to have less of this symbiotic zooxanthellae than many other Sychphozoa. Catostylus mosaicus are also known to have relationships with other species, including fishes, spider crabs, shrimp, phyllosoma larvae, portunid crabs, and amphipods. A commensal relationship with the copepod species Paramacrochiron maximum has been observed. This copepod exists in high abundance on the oral arms of the jellyfish, and it is thought that the copepod consumes mucus produced by its jellyfish host.

## Human interactions

Catostylus mosaicus and humans influence one another in a few different ways. Large blooms of jellyfish in coastal areas can interrupt recreation and their arms may produce a mild but irritating sting. Due to their size and high abundance, C. mosaicus is harvested for human consumption, and is considered a delicacy in some countries, including China and Japan.
Finally, the venom of C. mosaicus and other Sychphozoans is being investigated in terms of potential anticancer effects. The cnidocytes of C. mosaicus hold venom which may have apoptopic effects on A549 cells, the same cells linked to pulmonary adenocarcinoma, a common form of lung cancer. Further study and isolation of these cnidocytes may lead to anticancer innovations.