Carybdea sivickisi

Geographic Range

Carybdea sivickisi has been found in many temperate, tropical, and subtropical locations in the western Pacific from Japan in the north, the Indo-Pacific, to New Zealand in the south. Most specimens have been found in temperate regions around the end of August, and subtropical regions between April and August. These regions seem to have native strains of Carybdea sivickisi. (Hoverd, 1985; Lewis and Long, 2005)


Carybdea sivickisi is generally found in the shallower waters of the ocean, especially during the summer months due to their mating rituals. However, box jellies travel to deeper depths in open marine waters in search of food. This species resides in marine saltwater, mild temperate, tropical, and subtropical regions. (Lewis and Long, 2005; Lewis, et al., 2008; Shapiro, 2011)

Physical Description

Carybdea sivickisi is a small, bell shaped, transparent creature, with a bell diameter of about 1-4 mm, sometimes up to 14 mm, and a height of 7 mm. This species has four interradial compressed corners, each with pedalia (muscular adhesive pads) and yellow tentacles coming from them. The tentacles have nematocyst rings and swellings on the end. Also visible in the specimen are the velarial canals, manubrium, nerve ring, rhopalia, and the radial cyst. Females are distinguishable from males because they have orange spots on their bell. Cnidarians in general are polymorphic with alternating polyp and medusa stages. (Hoverd, 1985; Lewis and Long, 2005)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • female more colorful
  • Average length
    7 mm
    0.28 in


Carybdea sivickisi females have a long, gelatin like strand where they house their embryos that form only a few hours after fertilization. These embryos become planulae that swim for a few days and then settle on a substrate. After settling, they metamorphose into a sessile polyp. The polyps then form a creeper stage after a few more days. The creeper stage then eventually forms a juvenile medusa. (Hartwick, 1991; Shapiro, 2011)


The mating behavior of Carybdea sivickisi differs from most jellyfish. In what is termed 'the wedding dance', the male moves the female through the water by her tentacle. He positions her so their manubria (orifices) are close together and passes her a sac full of brightly colored red sperm. She then eats this sac and the eggs are fertilized. Males can pass a sperm sac to many different females, and females can accept many different sperm sacs from many males. Males may be able to choose their females based on their bright orange spots. (Hoekenga, 2011)

Carybdea sivickisi tends to mate in the spring and summer when the water is warmer. The gestational period is an average of 55 hours, and the embryos produced from a single fertilization event are approximately 3,000 in each strand. Each embryo strand weighs approximately 55 mg, and there is evidence that Carybdea sivickisi females only produce one embryo strand and die 16 days after. These embryos are held in the embryo strand for approximately 4 days and are released as planulae as the strand decomposes. (Lewis and Long, 2005; Lewis, et al., 2008)

  • Breeding season
    The breeding season for Carybdea sivickisi is spring and summer
  • Average number of offspring
  • Average gestation period
    55 hours
  • Average time to independence
    4 days

Carybdea sivickisi puts effort into parental care through the formation of an embryo strand. This gelatinous strand holds all of the embryos together inside the female and ensures they are able to develop before they are released on their own to swim and attach to a surface to metamorphose. (Hartwick, 1991; Lewis and Long, 2005)

  • Parental Investment
  • no parental involvement
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female


The life cycle of this organism includes four days for embryonic development into a planula, four days of swimming around, and eight days for the planula to settle on a substrate to metamorphose. The actual metamorphosis process to become a polyp is 24 hours. The sessile polyp lives approximately 2-6 weeks after it settles on the substrate before they die. This makes a total of 4-8 weeks. Some organisms are able to survive the polyp stage, and after another three days become an elongated "creeper" stage which eventually metamorphs into a juvenile medusae stage. In lab experiments, the transitions from polyp to creeper and then to medusa was not observed, however it has been reported that the medusae die shortly after sexual reproduction. (Hartwick, 1991)

  • Range lifespan
    Status: wild
    28 to 56 days


A medusa of Carybdea sivickisi spends most of its days attached by its bell to the undersides of rocks. They have the ability to compact their bodies by folding their four tentacles inside their bells or by flattening. They swim to a surface, make contact with it using their adhesive pads, and then quickly stick to the surface. While stuck to the surface they are motionless and their tentacles are relaxed. They can remain like this for varied amounts of time. They detach either spontaneously or by some sort of stimulus and continue to swim. The reason for attaching to substrates and remaining immobile is to save energy and to avoid predators. They are usually attached to a substrate during the day and then free swimming during the night. (Hartwick, 1991)

Communication and Perception

Vision plays a role on what surfaces Carybdea sivickisi attaches. The developed rhopalial eyes have not been studied completely, but have a role in their reproductive behavior. These box jellies also have sexually dimorphic pigmentation patterns and distinctive banding patterns on their tentacles that may have a role in mate recognition. (Hartwick, 1991)

Food Habits

Because Carybdea sivickisi is free swimming during the night, it feeds mainly on night swarming benthic organisms. This includes heteronereids, cumaceans, gammarid amphiods, and isopods. This jellyfish stings its prey to capture it. (Hartwick, 1991)

  • Primary Diet
  • carnivore
    • eats non-insect arthropods
  • Animal Foods
  • aquatic or marine worms
  • aquatic crustaceans
  • other marine invertebrates
  • zooplankton


To avoid predators Carybdea sivickisi attaches to surfaces. (Hartwick, 1991)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

There are no published studies on the role of Carybdea sivickisi on the ecosystem, but it feeds on benthic organisms and therefore is part of the food web for benthic populations. (Hartwick, 1991)

Economic Importance for Humans: Positive

Carybdea sivickisi is of special importance to scientists because of its unique mating rituals. This species is one of the only cubozoans to exhibit this "intimate" mating ritual. This species has also helped scientists study the rhopalia eyes found in cubozoans. (Hartwick, 1991; Hoekenga, 2011)

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

Like many species of Cubozoa, Carybdea sivickisi have cnidocytes that sting organisms. The cnidocytes are used to catch prey and can be harmful to humans, if they are stung. However, the stings are not known to be fatal for humans. (Hartwick, 1991)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

Carybdea sivickisi requires no special conservation efforts.


Roshni Patel (author), Rutgers University, Kimberly Rutledge (author), Rutgers University, David V. Howe (editor), Rutgers University, Renee Mulcrone (editor), Special Projects.



Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.


an animal that mainly eats meat


uses smells or other chemicals to communicate


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females


union of egg and spermatozoan

internal fertilization

fertilization takes place within the female's body


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.


reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.


An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

radial symmetry

a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


uses sight to communicate

year-round breeding

breeding takes place throughout the year


animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)


Hartwick, R. 1991. Observations on the anatomy, behaviour, reproduction and life cycle of the cubozoan Carybdea sivickisi. Hydrobiologia, 216-217: 171-179.

Hoekenga, C. 2011. "Jellyfish romance-(Carybdea sivickisi)" (On-line). Smithsonian Natural Museum of Natural History. Accessed February 23, 2013 at

Hoverd, W. 1985. Occurance of the order Cubomedusae (Cnidaria, Scyphozoa) in New Zealand: collection and laboratory observations of Carybdea sivickisi. New Zealand Journal of Zoology, 12: 107-110. Accessed February 23, 2013 at

Lewis, C., S. Kubota, A. Migotto, A. Collins. 2008. Sexually dimorphic culjomedusa Carybdea sivickisi. Publ. Seto Mar. Biol. Lab, 40: 1-8. Accessed February 23, 2013 at

Lewis, C., T. Long. 2005. Courtship and reproduction in Carybdea sivickisi (Cnidaria: Cubozoa). Marine Biology, 147: 477–483. Accessed February 23, 2013 at

Shapiro, L. 2011. "Carybdea sivickisi" (On-line). EOL species rapid response. Accessed February 23, 2013 at